Next Article in Journal
Three-Dimensional Time-Lapse Joint Inversion of Resistivity and Time-Domain Induced Polarization Methods
Previous Article in Journal
The Effect of Metal Artefacts in Guided Implant Placement: A Review on the Accuracy of 3D-Printed Surgical Implant Template
Previous Article in Special Issue
Mutation Rates and Fitness Genes in Staphylococcus aureus Treated with the Medicinal Plant Synadenium glaucescens
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Applied Sciences
Volume 15
Issue 18
10.3390/app151810017
applsci-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Influence of Q-SUN Irradiation on Antimicrobial and Antiviral Activity of Tea Tree Oil-Based Coatings on Polypropylene Films

by
Wojciech Jankowski
1,
Dobrosława Mizielińska
1,2 and
Małgorzata Mizielińska
1,*
1
Center of Bioimmobilisation and Innovative Packaging Materials (CBIMO), Faculty of Food Sciences and Fisheries, West Pomeranian University of Technology Szczecin, Janickiego 35, 71-270 Szczecin, Poland
2
Faculty of Pharmacy, Medical Biotechnology and Laboratory Medicine, Pomeranian Medical University, 70-204 Szczecin, Poland
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(18), 10017; https://doi.org/10.3390/app151810017
Submission received: 1 August 2025 / Revised: 2 September 2025 / Accepted: 11 September 2025 / Published: 13 September 2025
(This article belongs to the Special Issue Advances in Natural Antimicrobial Compounds: Discovery, Synthesis, Characterization, and Application)
Browse Figures
Versions Notes

Abstract

The study investigated the antimicrobial and antiviral effects of polypropylene foil coated with hydroxypropyl methylcellulose (HPMC) layer containing tea tree oil (TTO) as the active agent. Moreover, the influence of accelerated aging using Q-SUN treatment on the efficacy of the non-coated and coated foils was also investigated. The results of the study indicated a slight antimicrobial effect of the irradiated coating against S. aureus, noticeable antibacterial activity of both irradiated and non-irradiated coating against E. coli and a complete inhibition of B. cereus growth by the irradiated coating. However, both of these coatings exhibited strong antiviral properties, confirmed by a method consisting of two separate tests conducted on the Φ6 phage as the infectious agent: real-time measurement of the host’s OD during co-culture with the phage and observation of the host’s growth on copper mesh grids using scanning electron microscopy (SEM). The characteristics of non-irradiated and irradiated foils were also determined using SEM and FT-IR.

1. Introduction

Melaleuca alternifolia is a well-described species of native Australian plant. This plant can be subjected to an extraction process, yielding a substance known as tea tree oil (TTO). TTO is transparent to slightly yellow in color, has a strong odor—similar to camphor—and exhibits a cooling effect [1]. The M. alternifolia oil is extracted from the leaves and terminal branches by steam and vacuum distillation processes [2]. Tea tree essential oil is composed of approximately 100 various chemical substances, such as monoterpenes (α-pinene, terpinolene, p-cymene, 1,8-cineole, γ-terpinene, and terpinen-4-ol) and sesquiterpenes, as well as their respective alcohols. Most of the antimicrobial properties of TTO were attributed to terpinen-4-ol (also known as 4-carvomenthenol) [1]; however, chlorhexidine (cationic bisbiguanide) is considered a gold standard antimicrobial agent [2]. Moreover, it is assumed that TTO antimicrobial properties result from complex interactions between its different components. Many scientific studies demonstrated that most clinically relevant bacteria such as Salmonella typhimurium, Staphylococcus aureus (including MRSA), Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, etc., are sensitive to low TTO concentrations, confirming its role as an effective antibacterial agent [3,4,5,6,7,8,9]. The antifungal effectiveness of some major components of tea tree oil against Fusarium graminearum, Fusarium culmorum, Trichophyton rubrum, Candida albicans, etc., was also widely described in numerous studies [8,10,11,12]. The antimicrobial activity of TTO components can be attributed to disturbing the structural integrity of bacterial and fungal membranes. Due to the lipophilic character of cyclic monoterpenes, they can separate from the aqueous phase into the lipid cell membrane environment, resulting in cell membrane expansion, increased fluidity and inhibition of membrane-embedded enzymes [3,13]. The key difference between the mechanisms of action of TTO against Gram-positive and Gram-negative bacteria is related to the structure of the outer membrane of Gram-negative bacteria, which is rich in lipopolysaccharides and acts as a barrier for the hydrophobic compounds present in tea tree oil. This structural barrier makes Gram-negative bacteria generally more resistant to TTO, as it restricts the penetration of tea tree oil’s active compounds through the membrane. On the other hand, Gram-positive bacteria lack the outer membrane, and their underlying thick peptidoglycan layer is susceptible to being penetrated by TTO’s active compounds. These compounds can easily disrupt the bacterial cell membrane, leading to leakage of ions, proteins, and other cellular contents, eventually causing cell death. They may also interfere with enzyme activity and inhibit bacterial replication [14].
Most essential oils (EOs) have a more pronounced antibacterial effect on Gram-positive than on Gram-negative bacterial species. Their antimicrobial properties are dependent on the overall chemical composition, as well as on the exact amounts of specific compounds. Some EOs, such as those found in hyssop, basil, rosemary, or in oregano and marjoram, were observed to be effective against S. aureus, E. coli, B. cereus and Salmonella spp., even though they were less active against Pseudomonas spp., owing to the formation of exopolysaccharides (produced by Pseudomonas cells) which increased the cells’ resistance to EOs. The mechanisms of action of essential oils depend on their chemical composition. It is why their antimicrobial properties are not attributable to a unique mechanism, but are rather a result of a cascade of reactions involving the entire bacterial cell [14].
While antibacterial and antifungal properties of tea tree oil are well known, few studies describe the mechanism of its virucidal and/or antiviral effectiveness. It was demonstrated that TTO can be active against the herpes simplex virus (HSV-1) [3,15,16,17,18], as the components of the oil exert direct action on extracellular virions. The oil is also effective against the influenza virus and several members of Orthocoronavirinae, as its interactions with their envelopes hamper the process of viral invasion into the cells. Additionally, non-enveloped viruses were found to be more resistant than enveloped viruses to TTO-based antiviral treatments than enveloped particles [3,15,19,20,21,22,23]. The SARS-CoV-2 virion is composed of an outer membrane envelope, mainly covered with glycoproteins called Spike (S), that are responsible for receptor binding and virus fusion with the host/human cell [15,24]. Romeo A. et al. [15] showed that formulations characterized by a 3.33% concentration of TTO demonstrated virucidal activity against two SARS-CoV-2 surrogates: the FCoVII virus and a low–pathogenicity human HCoV-OC43 coronavirus. The simulation analysis performed by the authors confirmed that the TTO’s compounds easily entered the viral membrane and altered its thickness profile. The authors assumed that the introduction of TTO compounds into the viral envelope could lead to changes in its molecular organization and influence the efficiency of the viral–host cell membrane fusion process. Specifically, the lipophilic terpene components tended to disrupt the structure and function of the envelope. Additionally, it should be added that tea tree oil, if correctly used, is considered safe [3,24,25,26]. Taking into account its low toxicity to humans, as well as significant antibacterial, antifungal and antiviral properties, this oil can be used as the active agent of antimicrobial coatings applied on the surfaces of packaging materials.
In order to make a material exhibiting antimicrobial properties, packaging materials such as polypropylene film (PP) can be covered with active coatings. It is possible for such films to be coated on both sides—the internal coating with antibacterial and/or antifungal activity preserves food and acts against microorganisms responsible for food spoilage, while the external coating with antibacterial and antiviral effectiveness protects consumers from toxigenic bacteria and viruses such as SARS-CoV-2 [27,28,29,30,31]. Additionally, it is very important to ensure that an active/coated film keeps its functionality throughout storage, inhibiting the growth of microorganisms such as bacteria, yeast, or mold in order to maintain the quality and even extend the shelf life of the food. This means that an active layer applied on packaging material should provide sufficient resistance against ultraviolet (UV) radiation. Unfortunately, ultraviolet radiation can lead to the inactivation of packaging materials and the loss of their antimicrobial properties. An active agent that is sensitive to UV in an active coating can lose its functionality after accelerated UV aging, which is supposed to simulate real-world conditions [28,29,30,31].
Active agents are often used in conjunction with suitable carriers to create durable and effective coatings with desirable characteristics. Zhu L. et al. [32] used tea tree oil as the active agent in pullulan-based and hydroxypropyl-β-cyclodextrin-based coatings applied on kraft paper to create a packaging material with antimicrobial properties. The authors confirmed that the coated paper exhibited activity against S. aureus and E. coli. While these coatings served their purpose well, the most commonly used substance to serve as a carrier for the sustained release of essential oils is currently hydroxypropyl methylcellulose (HPMC) [33]. This non-toxic, water-soluble biopolymer, characterized by good compatibility with active antimicrobial substances, was chosen as the coating carrier to obtain active layers on the surface on PP film [28,33].
To summarize, numerous studies describe antibacterial [3,9], antifungal [10,12] and antiviral properties of tea tree oil [15,19,20,21,22,23] as well as the mechanisms of action of its active compounds [14]. Due to its antimicrobial effectiveness, tea tree oil was used as antibacterial and antifungal agent to obtain packaging materials for food products to preserve them against microorganisms responsible for their spoilage or against human pathogens [32,34]. Such active packaging may maintain the high quality of food and extend its shelf-life [27,28,29,31]. However, there is a lack of information in scientific works regarding the use of tea tree oil to obtain packaging material covered with an external coating with antiviral activity. Such packaging could protect consumers against the viruses spread by contact with the skin. Moreover, it is worth mentioning that the external coating is very often exposed to UV radiation. A suitable coating should remain active or even increase its activity after exposure to UV aging.
Therefore, an attempt was made to create an active, external and internal coating applied on polypropylene film with tea tree oil as the antimicrobial agent. The aim of study was also to analyze the influence of accelerated Q-SUN irradiation (UV-aging) on the antimicrobial properties of obtained coating.

2. Materials and Methods

2.1. Materials

The microorganisms tested in the performed experiments were purchased from two international collections:
1. The Leibniz Institute DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen), which provided E. coli DSMZ 498 as a representative of rod-shaped, Gram-negative bacteria, C. albicans DSMZ 2566 as a member of yeast, S. aureus DSMZ 346 as a spherically shaped, Gram-positive bacterial strain, Pseudomonas syringae van Hall 1902 DSM 21482 as Φ6 phage host; the Φ6 phage (DSM-21518) was used as SARS-CoV2 substitute;
2. The American Type Culture Collection (ATCC), which provided Bacillus cereus ATCC 14579 as a rod-shaped, spore-forming, Gram-positive bacterial strain.
Polypropylene (PP) film (CBIMO, Szczecin, Polska) was used as packaging material to be covered with the antimicrobial coating. Hydroxy-propyl-methylcellulose (HPMC, Chempur, Piekary Śląskie, Poland) was employed as the coating carrier to be applied on PP surface. Tea tree oil (ETJA S.C., Elbląg, Poland) was purchased as the antimicrobial agent, and Tween 20 (Chempur, Piekary Śląskie, Poland) was used as an emulsifier. To evaluate the antimicrobial effectiveness of the created coating, TSB, MacConkey, TSA and Sabouraud mediums (Merck, Darmstadt, Germany) were purchased. Suitable aliquots of the powdered media were weighted, suspended in distilled water and sterilized in an autoclave at 121 °C for 15 min, in accordance with the protocol supplied by the producer.

2.2. Preparation of Coating Carrier

As the first step of investigations, 4 g of HPMC was introduced into 96 mL of distilled water and mixed for 4 h using a magnetic stirrer (Ika, Staufen im Breisgau, Germany) at 750 rpm, 25 °C. Then, 10 g of tea tree oil and 1 g of Tween 20 were introduced into the beaker and mixed for 2 min at 800 rpm, 25 °C. As the final step, 90 g of dissolved HPMC was added into the emulsion and mixed 10 min at 1200 rpm, 25 °C.

2.3. Application of Carrier with TTO on the Surface of PP Film

The polypropylene (PP) film was coated with the emulsion of HPMC containing TTO and Tween 20 using Unicoater 409 (Erichsen, Hemer, Germany) at a temp. of 25 °C with a roller which produced a layer 40 μm thick. The coating was dried for 10 min at a temperature of 50 °C to obtain transparent layer (Figure 1). PP film which was not coated was used as the control sample (C).

2.4. Q-SUN Irradiation

The neat and coated PP films were cut into rectangular shapes (26.0 cm × 2.5 cm). The samples were placed in a Q-SUN accelerated Xenon Test Chamber set at 1.5 W/m2 (Model Xe-2, Q-LAB) and irradiated for 24 h.

2.5. Determination of the Antimicrobial Activity of the Coatings

The neat and coated PP films (subjected and not subjected to accelerated Q-SUN irradiation) were cut into square shapes (3 cm × 3 cm). The antibacterial and antifungal activity was examined according to the ASTM E 2180-01 standard [35].
To prepare for the analysis of the antiviral properties of neat and coated films (irradiated and non-irradiated), the Φ6 phage was refined according to Bhetwal et al. [36]. The pure Φ6 lysate was prepared according to Bonilla et al. [37]. The antiviral activity of the samples was examined according to a modified ISO 22196-2011 standard [38]. Then, an amplification of the Φ6 particles was performed using the method of Skaradzińska et al. [39].
Based on previous studies, an analysis of antiviral properties took place [27,30]. The previously prepared viral lysates were incubated with neat PP film as control sample (irradiated and non-irradiated), as well as PP film with HPMC coating containing TTO applied on its surface (also irradiated and non-irradiated). The lysate was incubated with all mentioned samples individually according to ISO 22196-2011 [38]. Afterwards, LB broth was introduced into 4 Falcon-type test tubes, dedicated for BioSan bioreactors (BS-010160-A04, BioSan, Riga, Latvia), which allowed for real-time optical density quantification. Then, host overnight culture was added to LB broth (to obtain 10 mL of bacterial inoculum), and this was incubated at 28° with initial OD = 0.2. Four Φ6 lysates (100 µL of each separately) were amplified in their own host bacteria (the first lysate—after its incubation with the non-covered, non-irradiated film (control sample), the second lysate—after its incubation with the non-irradiated HPMC layer containing TTO, the third lysate—after its incubation with non-covered, irradiated film, the fourth lysate—after its incubation with the irradiated HPMC layer containing TTO. The lysates were added to host cultures (test tubes) when OD = 0.2 and incubated in the BioSan bioreactors at 28 °C until the OD for the control samples began to decrease (15 h). Simultaneously, the samples for microscopic analysis were prepared as follows: four grids of carbon-coated copper (400 mesh) were placed into microplate wells. Then, 100 µL of the 4 lysates with host (from Falcon-type test tubes, before they were placed in bioreactors) were added into microplate wells and incubated at 28 °C for 15 h in a climate chamber with 90% relative humidity. The processes described in this section are presented in Scheme 1.

2.6. Microscopic Examination of the Coating Before and After Q-SUN Irradiation

A microscopic analysis of both the neat PP film and the film coated with HPMC containing TTO and Tween 20 was performed with a Vega 3 LMU (Tescan, Brno-Kohoutovice, Czech Republic) scanning electron microscope (SEM). The analysis has been deemed necessary to visualize the impact of accelerated aging through Q-SUN irradiation on the structure of the coating. The microscopic examination was performed at 25 °C using tungsten filament, with an accelerating voltage of 10 kV.

2.7. Host’s Count Visualization by SEM

After incubation, the previously prepared grids were removed from Eppendorf tubes, placed on Petri dishes and left to dry. Then, 100 µL of 2% glutaraldehyde in 0.1 M sodium cacodylate (NaCac, pH 7.4) solution was placed on the surface of each grid. After an 18 h period of storage at 4 °C, the samples were washed in 0.1 M sodium cacodylate. This was followed by dehydration using serial concentrations (20%, 40%, 60%, 80% and 100%) of methanol at −20 °C; the samples were transferred to a new container with higher concentration of methanol every two hours. Following these procedures, a sputter coater (Quorum Technologies Q150R S, Laughton, East Sussex, UK) set at 25 °C was used to cover the samples (previously placed on suitable pin stubs) with a thin layer of gold. Afterwards, the samples were subjected to microscopic analysis using a Vega 3 LMU (Tescan) scanning electron microscope (SEM) as described above.

2.8. FT-IR

A Spectrum 100 spectrophotometer (PerkinElmer, Waltham, MA, USA) set to a resolution of 4 cm−1 and sixteen scans per cycle was used to evaluate the Fourier transform infrared spectra (FT-IR) of both the non-coated PP film and the PP film coated with hydroxypropyl methylcellulose containing tea tree oil (before and after Q-SUN irradiation. The samples were placed directly at the ray-exposing stage, and the spectra were recorded at wavelengths between 650 and 4000 cm−1.

2.9. Statistical Analysis

The statistical significance was determined using a standard analysis of variance (ANOVA) procedure and a subsequent one-way ANOVA test. The threshold for considering the values statistically significant was set to p < 0.05. The analyses were performed using Prism 8 (GraphPad Software, San Diego, CA, USA).

3. Results and Discussion

3.1. Antimicrobial Properties

3.1.1. Antibacterial and Antifungal Properties

The performed procedures led to the creation of thin, transparent coatings with a grammage of 2.5 g/cm2 on the surface of the PP films. Despite the antibacterial properties of tea tree oil, the HPMC-based coating containing TTO did not inhibit the growth of S. aureus, and a slight increase in bacterial count was observed in the AC sample (Figure 2). Opposite findings were noted in previous studies [27,29,31] which showed that HPMC-based coatings with the addition of geraniol [27], Achillea millefolium L., Hippophae rhamnoides L., and Hypericum L. extracts [29] or Eucomis comosa extract [31] were active against S. aureus. The accelerated Q-SUN irradiation did not exert noticeable influence on the neat PP film; however, it very slightly improved the antibacterial effectiveness of the coating with TTO (Figure 2). These findings are partially supported by a previous experiment [28], which determined that a coating based on HPMC containing subcritical CO2 sea buckthorn extract was not active against S. aureus. However, after accelerated UV-A irradiation, this coating inhibited the growth of S. aureus completely. The results of the work were not in agreement with some other previous outcomes [31] which showed that Q-SUN irradiation marginally decreased the effectiveness of an active layer with the addition of E. comosa. It has to be underlined that accelerated Q-SUN irradiation significantly deteriorated the activity of the coating containing Achillea millefolium L., Hippophae rhamnoides L., and Hypericum L. extracts [31]. However, both a 24 h and a 72 h Q-SUN irradiation had no influence on the antibacterial activity of the coating consisting of HPMC and the three aforementioned extracts combined with ZnO nanoparticles [30]. The purported mechanism is thought to rely on the shielding properties of the nanoparticles, which protected the active substances from UV-aging, maintaining their activity [30,31].
The susceptibility assay of B. cereus is shown in Figure 3. As was emphasized on this Figure, the coating decreased the number of B. cereus in comparison with the control sample (neat PP film). Similar results were observed in previous studies [31], which demonstrated that B. cereus cells exhibited sensitivity towards a coating containing E. comosa extract. The accelerated Q-SUN irradiation did not affect the PP film, although it significantly improved the antibacterial activity of the layer with TTO, leading to a complete inhibition of B. cereus growth. These findings are in agreement with the previous results [31], which showed that Q-SUN treatment improved the antimicrobial effectiveness of the active coating with E. comosa. Analyzing the difference between the efficacy of non-irradiated and irradiated coatings against the described bacteria, there is no certain explanation for the phenomenon. However, in a previous paper [28] on the antibacterial properties of coatings containing sea buckthorn extract, it has been theorized that the exposure of the coating to Q-SUN radiation could cause morphological changes in the structure of the coating, exposing small pockets of the active agents embedded in the carrier and therefore causing the release of active, bactericidal compounds.
The high activity of the TTO-containing coating against B. cereus might be surprising, but the efficacy of TTO and other essential oils against spore-forming, Gram-positive bacteria is well-established in the literature. One study by Messager et al. [40] confirmed that TTO in high concentrations is able to exert direct sporicidal action against B. cereus. However, the reduction level observed by Messager was only moderate (1 to 1.5 log reduction for 10% and 15% TTO solutions with 30 to 120 min of contact time), so it cannot fully explain the complete inhibition of B. cereus growth in this study. Yet, it is important to point out that many essential oils can also hamper germination, effectively extending the lag phase more than tenfold [41]. It is possible that this mechanism was responsible for the lack of perceived growth, and perhaps in future experiments the actual amount of viable, not-yet-sporulating spores in the material exposed to active coatings will be assessed.
When it comes to the antibacterial properties of the HPMC coating containing tea tree oil against E. coli, it was noted that the number of bacterial cells decreased (>1 log reduction) when compared to the control sample (Figure 4), confirming that this layer was in fact effective against Gram-negative microorganisms. Similar findings were noted in previous studies [27,29], which showed that the HPMC carrier containing either geraniol [27] or a mixture of Achillea millefolium L., Hippophae rhamnoides L., and Hypericum L. extracts [29] could be used to create coatings which were effective against E. coli. It is worth underlining that the coating with 3 extracts described above was more effective than the coating containing TTO as the antimicrobial agent, as it inhibited the growth of E. coli completely. When analyzing the outcomes of the experiment, it was noted that neither the neat PP film nor the coating containing TTO were affected by the accelerated Q-SUN irradiation (Figure 4). These findings were confirmed by previous investigations [29] which showed no influence of accelerated irradiation on the active coatings’ ability to hinder E. coli growth. However, opposite results were observed in another work [28], which confirmed that the coating containing subcritical CO2 sea buckthorn extract had actually begun to exhibit activity against E. coli only after its exposure to Q-SUN irradiation.
The investigations performed on the coating’s effectiveness against C. albicans proved its slight efficacy against yeast cells (Figure 5). Contrary findings were observed in previous studies [28], which had shown that the coating containing subcritical CO2 sea buckthorn extract was not effective against C. albicans. Moreover, the accelerated Q-SUN irradiation slightly deteriorated the antimicrobial properties of the coating. Unfortunately, it was observed not to be active after irradiation. Opposite results were observed in the aforementioned work [28], which showed that Q-SUN irradiation slightly improved the coating’s activity against C. albicans.

3.1.2. Antiviral Properties

The performed experiments demonstrated that the coatings containing tea tree oil as the active agent were able to induce a complete reduction of the Φ6 phage titer compared to the control sample (neat PP film) (Figure 6). As visualized in Figure 7, an OD fall was noted after 6 h of Φ6 lysate cultivation with P. syringae for neat/uncoated PP film, confirming that the Φ6 particles were still active—meaning that their prior exposure to PP film had no influence on their activity. Opposite findings were noted for the coating with TTO. As emphasized in Figure 7, an OD fall was not noted even after 15 h of phage cultivation with P. syringae, meaning that the phage was not active. It may be concluded that the HPMC layer containing TTO was highly active against the mentioned phage, resulting in the inactivation of the Φ6 particles. The results of the previous investigations showed that the cultivation of Φ6 lysate with a coating containing geraniol as the active compound only marginally reduced the titer of the bacteriophages [27]. Additionally, an OD fall was observed after a 12 h of host incubation with the previously exposed Φ6 particles. Comparing antibacterial properties with antiviral activity, it was observed that the coating containing geraniol described in the aforementioned study was more active against bacterial strains than against the Φ6 phage. However, the coating containing TTO analyzed in this study was more effective against viral particles than against bacterial cells. This can be attributed to TTO’s lipophilic terpene components, which may disturb or even disintegrate the lipid envelope of the Φ6 phage. Previous experiments [42] also showed that a coating based on HPMC carrier containing subcritical CO2 black chokeberry extract with the addition of ZnO particles was highly effective against the Φ6 phage. The high antiviral activity could have been caused by the hydrophobic character of the CO2 black chokeberry extract or by the synergistic effect between the extract and ZnO nanoparticles. Another investigation [43] provided findings which showed that coatings containing ZnO nanoparticles and F. betulina, Verbascum L. or U. tomentosa extracts caused complete inactivation of the bacteriophage particles, meaning that the coatings were very effective against the Φ6 phage—perhaps due to a synergistic effect between extracts and zinc oxide nanoparticles.
The results of the work indicated that Q-SUN irradiation did not decrease the activity of the coating containing TTO against the Φ6 phage, which was confirmed by the lack of OD fall (Figure 7) and the complete elimination of Φ6 particles (Figure 6). Previous research [29] focused on the influence of UV irradiation on the antiviral activity of the coating containing Achillea millefolium L., Hippophae rhamnoides L., and Hypericum L. extracts. The results confirmed that the 24 h irradiation neither decreased nor increased the activity of the described coating. Moreover, the differences between the titers observed for the coating pre- and post-irradiation for 24 h were statistically insignificant. However, the coating sample irradiated for 72 h was found to have antiviral activity, confirming that longer irradiation could potentially improve the antiviral properties of the coating. Slightly different findings were observed in the case of coating containing A. millefolium L., H. rhamnoides L., and Hypericum L. extracts combined with ZnO nanoparticles, which turned out to be more effective against Φ6 phage after just 24 h of Q-SUN irradiation.

3.2. Microscopic Examination of the Coatings

Microscopic analysis of the neat PP film revealed that its surface was slightly rough and scratched, with visible impurities (Figure 8A). Interestingly, the Q-SUN irradiation had no impact on the film surface’s morphology (Figure 8B). Similar results were observed in a previous study [30], which also revealed the apparent roughness of both irradiated and non-irradiated neat PP film surfaces, confirming that Q-SUN irradiation did not influence their morphology. However, SEM images taken by Ranjan [44] showed the effects of 30-day UV irradiation combined with exposure to four kinds of environmental conditions—air, double-distilled water, potable water and saline water—on polypropylene foil. The authors indicated that the cracks and holes developed on the surface of PP films were due to photodegradation, which was enhanced by saline water. As one can observe in Figure 9A, the antimicrobial coating was undoubtedly visible on the PP film’s surface as a thoroughly and homogeneously applied layer with small holes and inclusions. Similar observations have been made in a previous study [30], during which homogenous layers of the coatings were clearly observed on the PP foil. The only difference was that their surface was more rough. The usage of a varnish based on an organic solvent (containing ZnO nanoparticles and TiO2 as active agents) as the coating carrier, applied on a hydrophobic PP film, could have been the reason. Similarly, in another study, small holes were visible on the surface of PLA film which was homogeneously covered with ethyl cellulose containing hydrophobic subcritical CO2 raspberry seed extract (with and without ZnO nanoparticles) [42]. The holes and inclusions were also observed [28] on the surface of PBS film coated with HPMC containing subcritical CO2 buckthorn extract. The HPMC layer with Achillea millefolium L., Hippophae rhamnoides L., and Hypericum L. extracts [29] was noted to be smoother than HPMC with TTO. Additionally, spherical and convex particles were observed on its surface. Taking into consideration the influence of Q-SUN irradiation on the surface of the HPMC layer containing TTO, it has been noticed that the irradiation smoothened the coating and made it more compact. These findings were not in agreement with the previous works [29,30], which showed that UV aging had no significant influence on the morphology of the active layers. However, in another study, accelerated aging [28] did influence the morphology of a coating containing buckthorn extract, leading to the migration of the antimicrobial agents to the surface and the formation of larger amounts of the spots in the top coating. Macieja et al. [28] confirmed that accelerated aging caused the erosion of HPMC layer, presumably exposing the active substances in the coatings and increasing their antimicrobial effectiveness. The results of this work confirmed that, despite the smoothening and compacting of the coating caused by Q-SUN irradiation, it became more active against selected bacterial strains. Additionally, small holes, inclusions and folds were visible on its surface (Figure 9B). It may be suggested that TTO could have migrated to the surface’s folds and be partially released, increasing the coating’s antibacterial effectiveness. Summarizing, as was mentioned by Macieja et al. [28], accelerated irradiation can have a beneficial impact on improving the antimicrobial properties of the coated films. The authors suggest that controlled, slow release of active agents on the active coatings’ surface make them more effective over time.

3.3. P. syringae Count Visualization by SEM

The review of the results from the experiment performed on non-covered PP film indicated that there was no bacterial overgrowth of the copper grids, with singular, elongated P. syringae cells (with their morphology altered by the phage’s attack) being observable on the surface of the copper grids (Figure 10). This confirmed that the phage was active, as it inhibited the growth of host cells, and that the PP film had no impact on the activity of the Φ6 particles. Similar findings were noticed for the Q-SUN-irradiated neat PP film (Figure 11). In this case, the presence of singular bacterial cells on the copper grid proved that the irradiated PP also did not have an impact on bacteriophage effectiveness. As seen in Figure 12, the Φ6 lysate previously incubated with the TTO-containing active coating did not show noticeable bactericidal action, allowing the bacteria to freely grow on the grids. The bacterial mass was clearly visible on the surface of the copper grid, proving their good adhesion to the structure. This observation confirmed that the Φ6 phage had been deactivated by the coating with TTO. Additionally, it was noticed that Q-SUN irradiation did not deteriorate the antiviral properties of the active coating (Figure 13). The irradiated coating was active and it inactivated the bacteriophage, as confirmed by the ample presence of P. syringae cells immobilized on the surface of copper grid. Similar results were noted in the previous study [30] which showed that in the case of neat PP films, the active phage influenced the host’s growth and caused the lack of viable bacterial cells on surface of the copper grid. On the other hand, P. syringae cells were visible after an active coating containing ZnO nanoparticles and TiO2 inactivated the Φ6 particles.

3.4. FT-IR Analysis

Spectroscopic examination of the neat PP film (Figure 14A) showed that there were two main regions observed in the FTIR spectra that extended through (1) ranges from 3000 to 2800 cm−1 and (2) ranges from 1500 to 1300 cm−1. The absorption peaks at 2949 and 2917 cm−1 might be stimulated by the stretching of C–H asymmetric single bonds. In addition, spectra peaks at 1455, 1376 and 945 cm−1 can be associated with CH3–CH2–induced absorption. The described spectrum (Figure 14A) is characteristic of PP film, which was confirmed by other authors [30,45,46,47,48]. The results of the study showed that differences in the chemical composition and morphology of PP films (PP) after Q-SUN irradiation were not observed using FT-IR, confirming that accelerated irradiation had no influence on non-covered PP film samples (Figure 14B). However, these PP films were exposed solely to UV-irradiation. Ranjan et al. [44] demonstrated that if PP samples are irradiated in different media, the changes may be seen not only on SEM images, but also in the FTIR spectra. The authors showed that a reduction in absorption peaks between 2947 cm−1 to 2838 cm−1 was noticed for samples exposed to double distilled water and potable water, which may indicate the breakdown of C–H bonds caused by exposure to ultraviolet radiation. The nearly total absence of ions in double-distilled water and their very low concentration in potable water increased the aggressiveness of these media in when it came to degrading the samples. High-energy ultraviolet radiation absorbed by plastics (e.g., PP) can cause the excitation of photons, subsequently creating free radicals. In the presence of oxygen, these free radicals form oxygen hydroperoxides which are capable of breaking the double bonds of the backbone chain and eventually form hydroxyl and carbonyl groups.
Gallart-Mateu et al. [48] performed spectroscopic analyses of tea tree oil. The authors observed an absorption band at 3470 cm−1 (which corresponds to O–H vibration), three strong bands at 2961, 2921 and 2876 cm−1 (caused by C–H and –CH2– vibrations, as well as from asymmetric –CH(CH3) stretching vibration), some weaker bands in the range between 1690 and 1580 cm−1 (which seem to correspond to the alkene functional group (C=C)), as well as another three strong bands located at 1468, 1444 and 1378 cm−1 (which match the –CH2– and –CH3 scissoring vibration). On the other hand, Da Silva et al. [49] observed a peak at 2942 cm−1, corresponding to the stretching of C–H bonds from HPMC chains, as well as a peak at 1747 cm−1 attributed to C=O bonding of carboxylic acid and oleic acid. Considering these authors’ results and the findings of the current work, it is tempting to suggest that the peaks seen on the spectra (Figure 15A,B) may be attributed to both HPMC and tea tree oil. As emphasized in these two figures, the FTIR spectrum for the HPMC coating with TTO revealed a broad band around the range of 3700–3100 cm−1 attributed to axial stretching of –OH groups, with a peak maximum at 3470 cm−1 for the HPMC with TTO layer. In the case of the 2922 cm−1 peak, its absorption is consistent with C–H single bond stretching. Moreover, a spectral peak at 1737 cm−1 was seen, stimulated by C=C double bond stretching. Similar results were described in the previous work which utilized FT-IR to confirm the presence of the antimicrobial coatings based on HPMC on the surface of PLA [31] and PP films [30,42].
The previous work [30] did not confirm any impact of Q-SUN irradiation on the active coatings. However, the antimicrobial layers described in it contained ZnO nanoparticles with shielding properties, which might have led to the conservation of their activity. Figure 15B and Figure 16B show FT-IR spectra of the coated PP film after Q-SUN irradiation. As both Figures show, the accelerated irradiation did not alter the chemical composition of the HPMC coating with TTO even though it did slightly improve its antibacterial activity against certain bacterial species. It is tempting to suggest that the coatings’ activity improvement (caused by Q-SUN irradiation) might have been achieved not by a change in their chemical composition, but by an alteration of their morphology (migration of active agents to the surface of the coatings).

4. Conclusions

The conducted research supports the notion that tea tree oil is a potent antiviral agent that can be efficiently used in HPMC-based coatings. It is worth underlining that the non-irradiated coating demonstrated very high antiviral effectiveness, as evidenced by the complete elimination of Φ6 phage particles after their incubation with the active coating. Moreover, Q-SUN irradiation did not decrease the antiviral activity of the coating. It confirms that the coating can be applied as an external layer of packaging materials. In terms of their antibacterial activity, the non-irradiated coating was able to cause a moderate reduction in B. cereus and E. coli growth, as well as a slight reduction in C. albicans growth. However, the irradiated coating was not only able to decrease the numerosity of E. coli and S. aureus, but also completely inhibited the growth of B. cereus, confirming that Q-SUN irradiation improved the antibacterial activity of the layer. It can be concluded that this coating could be applied as an internal layer on packaging materials and used only after irradiation. FT-IR analysis demonstrated clear differences between the spectra of uncoated and coated foils, corroborating the presence of the coating on the surface of the polypropylene film. Furthermore, no distinction could be observed between irradiated and non-irradiated films, confirming that Q-SUN irradiation did not alter the chemical composition of the coating, even though it had a slight impact on its morphology, contributing to an increase in its activity against selected bacterial strains.
To summarize, the created coating may be applied as the external coating of an active packaging material, as it exhibits significant antiviral properties. However, due to a low-to-moderate antibacterial and antifungal effectiveness of the non-irradiated version of coating, it could still be improved. The future pathways to modifying the material may be based on the addition of another active compound which may increase the coating’s activity through exerting a synergistic effect.

Author Contributions

Conceptualization, W.J. and M.M.; methodology, M.M. and W.J.; software; formal analysis, M.M. and W.J.; investigation, W.J., D.M. and M.M.; resources, M.M.; data curation, W.J. and M.M.; writing—original draft preparation, W.J. and M.M.; reagents/materials preparation: W.J., D.M.; writing—review and editing, W.J. and M.M.; visualization, W.J. and M.M.; supervision, M.M.; funding acquisition, M.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Acknowledgments

Certain graphics used in this article have been acquired from the following sources: Falcon-type tube: created by Diogo Losch de Oliveira (scidraw.io). 96-well plate template: Sigma-Aldrich/Merck KGaA (Burlington, MA, USA).

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Yasin, M.; Younis, A.; Javed, T.; Akram, A.; Ahsan, M.; Shabbir, R.; Ali, M.M.; Tahir, A.; El-Ballat, E.M.; Sheteiwy, M.S.; et al. River Tea Tree Oil: Composition, Antimicrobial and Antioxidant Activities, and Potential Applications in Agriculture. Plants 2021, 10, 2105. [Google Scholar] [CrossRef]
  2. Moreno, A.L.M.; de Moraes Melo Neto, C.L.; Coelho Goiato, M.; Moreno, N.V.A.; Dos Santos, D.M.; de Lima, C.C.; Lopes Motta, R.H.; Ramacciato, J.C. Effect of Chlorhexidine and Tea Tree Oil on Reducing the Number of Oral Microorganisms. Eur. J. Dent. 2024, 18, 397–400. [Google Scholar] [CrossRef]
  3. Iacovelli, F.; Romeo, A.; Lattanzio, P.; Ammendola, S.; Battistoni, A.; La Frazia, S.; Vindigni, G.; Unida, V.; Biocca, S.; Gaziano, R.; et al. Deciphering the Broad Antimicrobial Activity of Melaleuca alternifolia Tea Tree Oil by Combining Experimental and Computational Investigations. Int. J. Mol. Sci. 2023, 24, 12432. [Google Scholar] [CrossRef]
  4. Brun, P.; Bernabè, G.; Filippini, R.; Piovan, A. In Vitro Antimicrobial Activities of Commercially Available Tea Tree (Melaleuca alternifolia) Essential Oils. Curr. Microbiol. 2019, 76, 108–116. [Google Scholar] [CrossRef]
  5. Lakatos, M.; Apori, S.O.; Dunne, J.; Tian, F. The Biological Activity of Tea Tree Oil and Hemp Seed Oil. Appl. Microbiol. 2022, 2, 534–543. [Google Scholar] [CrossRef]
  6. Haines, R.R.; Putsathit, P.; Tai, A.S.; Hammer, K.A. Antimicrobial Effects of Melaleuca alternifolia (Tea Tree) Essential Oil against Biofilm-Forming Multidrug-Resistant Cystic Fibrosis-Associated Pseudomonas aeruginosa as a Single Agent and in Combination with Commonly Nebulized Antibiotics. Lett. Appl. Microbiol. 2022, 75, 578–587. [Google Scholar] [CrossRef]
  7. Sudjana, A.N.; Carson, C.F.; Carson, K.C.; Riley, T.V.; Hammer, K.A. Candida albicans Adhesion to Human Epithelial Cells and Polystyrene and Formation of Biofilm Is Reduced by Sub-Inhibitory Melaleuca alternifolia (Tea Tree) Essential Oil. Med. Mycol. 2012, 50, 863–870. [Google Scholar] [CrossRef]
  8. Oliveira, M.S.; Paula, M.S.A.; Machado Cardoso, M.; Silva, N.P.; Diniz Tavares, L.C.; Gomes, T.V.; Lopes Porto, D.; Soares, C.F.; Aragão Fabri, A.R.L.; Diniz Tavares, G.; et al. Exploring the antimicrobial efficacy of tea tree essential oil and chitosan against oral pathogens to overcome antimicrobial resistance. Microb. Pathog. 2024, 196, 107006. [Google Scholar] [CrossRef] [PubMed]
  9. Badra, M.M.; Taktaka, N.E.N.; Badawy, M.E.I. Comparison of the Antimicrobial and Antioxidant Activities of Tea Tree (Melaleuca alternifolia) Oil and its Main Component Terpinen-4-ol with their Nanoemulsions. Egypt. J. Chem. 2023, 66, 111–120. [Google Scholar] [CrossRef]
  10. Terzi, V.; Morcia, C.; Faccioli, P.; Valè, G.; Tacconi, G.; Malnati, M. In Vitro Antifungal Activity of the Tea Tree (Melaleuca alternifolia) Essential Oil and Its Major Components against Plant Pathogens. Lett. Appl. Microbiol. 2007, 44, 613–618. [Google Scholar] [CrossRef] [PubMed]
  11. Roana, J.; Mandras, N.; Scalas, D.; Campagna, P.; Tullio, V. Antifungal Activity of Melaleuca alternifolia Essential Oil (TTO) and Its Synergy with Itraconazole or Ketoconazole against Trichophyton rubrum. Molecules 2021, 26, 461. [Google Scholar] [CrossRef]
  12. Francisconi, R.S.; Huacho, P.M.M.; Tonon, C.C.; Bordini, E.A.F.; Correia, M.F.; Sardi, J.D.C.O.; Spolidorio, D.M.P. Antibiofilm Efficacy of Tea Tree Oil and of Its Main Component Terpinen-4-Ol against Candida albicans. Braz. Oral Res. 2020, 34, e050. [Google Scholar]
  13. Cox, S.D.; Mann, C.M.; Markham, J.L.; Bell, H.C.; Gustafson, J.E.; Warmington, J.R.; Wyllie, S.G. The Mode of Antimicrobial Action of the Essential Oil of Melaleuca alternifolia (Tea Tree Oil). J. Appl. Microbiol. 2000, 88, 170–175. [Google Scholar] [CrossRef] [PubMed]
  14. Nazzaro, F.; Fratianni, F.; De Martino, L.; Coppola, R.; De Feo, V. Effect of Essential Oils on Pathogenic Bacteria. Pharmaceuticals 2013, 6, 1451–1474. [Google Scholar] [CrossRef] [PubMed]
  15. Romeo, A.; Iacovelli, F.; Scagnolari, C.; Scordio, M.; Frasca, F.; Condò, R.; Ammendola, S.; Gaziano, R.; Anselmi, M.; Divizia, M.; et al. Potential Use of Tea Tree Oil as a Disinfectant Agent against Coronaviruses: A Combined Experimental and Simulation Study. Molecules 2022, 27, 3786. [Google Scholar] [CrossRef]
  16. Schnitzler, P.; Schön, K.; Reichling, J. Antiviral Activity of Australian Tea Tree Oil and Eucalyptus Oil against Herpes Simplex Virus in Cell Culture. Pharmazie 2001, 56, 343–347. [Google Scholar]
  17. Astani, A.; Reichling, J.; Schnitzler, P. Comparative Study on the Antiviral Activity of Selected Monoterpenes Derived from Essential Oils. Phyther. Res. 2010, 24, 673–679. [Google Scholar] [CrossRef] [PubMed]
  18. Gavanji, S.; Sayedipour, S.S.; Larki, B.; Bakhtari, A. Antiviral Activity of Some Plant Oils against Herpes Simplex Virus Type 1 in Vero Cell Culture. J. Acute Med. 2015, 5, 62–68. [Google Scholar] [CrossRef]
  19. Li, X.; Duan, S.; Chu, C.; Xu, J.; Zeng, G.; Lam, A.; Zhou, J.; Yin, Y.; Fang, D.; Reynolds, M.; et al. Melaleuca alternifolia Concentrate Inhibits in Vitro Entry of Influenza Virus into Host Cells. Molecules 2013, 18, 9550–9566. [Google Scholar] [CrossRef]
  20. Pyankov, O.V.; Usachev, E.V.; Pyankova, O.; Agranovski, I.E. Inactivation of Airborne Influenza Virus by Tea Tree and Eucalyptus Oils. Aerosol Sci. Technol. 2012, 46, 1295–1302. [Google Scholar] [CrossRef]
  21. Reichling, J. Antiviral and Virucidal Properties of Essential Oils and Isolated Compounds—A Scientific Approach. Planta Med. 2022, 88, 587–603. [Google Scholar] [CrossRef]
  22. Shao, Q.; Huang, J.; Li, J. Intracellular Replication Inhibitory Effects of Tea Tree Oil on Vesicular Stomatitis Virus and Anti-Inflammatory Activities in Vero Cells. Front. Vet. Sci. 2021, 8, 759812. [Google Scholar] [CrossRef]
  23. Garozzo, A.; Timpanaro, R.; Bisignano, B.; Furneri, P.M.; Bisignano, G.; Castro, A. In Vitro Antiviral Activity of Melaleuca alternifolia Essential Oil. Lett. Appl. Microbiol. 2009, 49, 806–808. [Google Scholar] [CrossRef]
  24. Tang, T.; Bidon, M.; Jaimes, J.A.; Whittaker, G.R.; Daniel, S. Coronavirus membrane fusion mechanism offers a potential target for antiviral development. Antiviral Res. 2020, 178, 104792. [Google Scholar] [CrossRef]
  25. Hammer, K.A.; Carson, C.F.; Riley, T.V.; Nielsen, J.B. A Review of the Toxicity of Melaleuca alternifolia (Tea Tree) Oil. Food Chem. Toxicol. 2006, 44, 616–625. [Google Scholar] [CrossRef]
  26. Bekhof, A.M.W.; van Hunsel, F.P.A.M.; van de Koppel, S.; Woerdenbag, H.J. Safety Assessment and Adverse Drug Reaction Reporting of Tea Tree Oil (Melaleuca aetheroleum). Phyther. Res. 2023, 37, 1309–1318. [Google Scholar] [CrossRef]
  27. Mizielińska, M.; Nawrotek, P.; Stachurska, X.; Ordon, M.; Bartkowiak, A. Packaging Covered with Antiviral and Antibacterial Coatings Based on ZnO Nanoparticles Supplemented with Geraniol and Carvacrol. Int. J. Mol. Sci. 2021, 22, 1717. [Google Scholar] [CrossRef] [PubMed]
  28. Macieja, S.; Zdanowicz, M.; Mizielińska, M.; Jankowski, W.; Bartkowiak, A. Poly(butylene succinate) Film Coated with Hydroxypropyl Methylcellulose with Sea Buckthorn Extract and Its Ethosomes—Examination of Physicochemical and Antimicrobial Properties Before and After Accelerated UV Aging. Polymers 2025, 17, 1784. [Google Scholar] [CrossRef]
  29. Mizielińska, M.; Zdanowicz, M.; Tarnowiecka-Kuca, A.; Bartkowiak, A. The Influence of Functional Composite Coatings on the Properties of Polyester Films before and after Accelerated UV Aging. Materials 2024, 17, 3048. [Google Scholar] [CrossRef] [PubMed]
  30. Mizielińska, M.; Bartkowiak, A. The Influence of the Q-SUN and UV-B Irradiation on the Antiviral Properties of the PP Films Covered with the Coatings Based on ZnO Nanoparticles and TiO2. Coatings 2024, 14, 125. [Google Scholar] [CrossRef]
  31. Mizielińska, M.; Kowalska, U.; Salachna, P.; Łopusiewicz, Ł.; Jarosz, M. The Influence of Accelerated UV-A and Q-SUN Irradiation on the Antibacterial Properties of Hydrophobic Coatings Containing Eucomis comosa Extract. Polymers 2018, 10, 421. [Google Scholar] [CrossRef] [PubMed]
  32. Zhu, L.; Liu, Y.; Liu, J.; Qiu, X.; Lin, L. Preparation and characterization of tea tree essential oil microcapsule-coated packaging paper with bacteriostatic effect. Food Chem. 2024, 23, 101510. [Google Scholar] [CrossRef]
  33. Bizymis, A.P.; Giannou, V.; Tzia, C. Contribution of Hydroxypropyl Methylcellulose to the Composite Edible Films and Coatings Properties. Food Bioprocess Technol. 2023, 16, 1488–1501. [Google Scholar] [CrossRef]
  34. Lee, J.Y.; Lee, J.; Ko, S.W.; Son, B.C.; Lee, J.H.; Kim, C.S.; Park, C.H. Fabrication of Antibacterial Nanofibrous Membrane Infused with Essential Oil Extracted from Tea Tree for Packaging Applications. Polymers 2020, 12, 125. [Google Scholar] [CrossRef]
  35. E 2180-01; ASTM Standard Test Method for Determining the Activity of Incorporated Antimicrobial Agent(s) in Polymeric or Hydrophobic Materials. ASTM International: West Conshohocken, PA, USA, 2002.
  36. Bhetwal, A.; Maharjan, A.; Shakya, S.; Satyal, D.; Ghimire, S.; Khanal, P.R.; Parajuli, N.P. Isolation of Potential Phages against Multidrug-Resistant Bacterial Isolates: Promising Agents in the Rivers of Kathmandu, Nepal. BioMed Res. Int. 2017, 2017, 3723254. [Google Scholar] [CrossRef] [PubMed]
  37. Bonilla, N.; Rojas, M.J.; Cruz, G.N.F.; Hung, S.H.; Rohwer, F.; Barr, J.J. Phage on tap–a quick and efficient protocol for the preparation of bacteriophage laboratory stocks. PeerJ 2016, 4, e2261. [Google Scholar] [CrossRef] [PubMed]
  38. ISO 22196-2011; Measurement of Antibacterial Activity on Plastics and Other Non-Porous Surfaces. ISO: Geneva, Switzerland, 2021.
  39. Skaradzińska, A.; Ochocka, M.; Śliwka, P.; Kuźmińska-Bajora, M.; Skaradziński, G.; Friese, A.; Roschanski, N.; Murugaiyan, J.; Roesler, U. Bacteriophage amplification–A comparison of selected methods. J. Virol. Methods 2020, 282, 113856. [Google Scholar] [CrossRef]
  40. Messager, S.; Hammer, K.A.; Carson, C.F.; Riley, T.V. Sporicidal Activity of Tea Tree Oil. Aust. Infect. Control. 2006, 11, 112–121. [Google Scholar] [CrossRef]
  41. Valero, M.; Salmerón, M.C. Antibacterial Activity of 11 Essential Oils against Bacillus Cereus in Tyndallized Carrot Broth. Int. J. Food Microbiol. 2003, 85, 73–81. [Google Scholar] [CrossRef]
  42. Mizielińska, M.; Bartkowiak, A. The Influence of Zinc Oxide and Zinc Stearate on the Antimicrobial Activity of Coatings Containing Raspberry and Chokeberry Extracts. Molecules 2024, 29, 3493. [Google Scholar] [CrossRef]
  43. Mizielińska, M.; Ordon, M.; Burdajewicz, W.; Nawrotek, P.; Sternal, J.; Okręglicki, M. The Antifungal and Antiviral Activity of Coatings Containing Zinc Oxide Nanoparticles and Verbascum L. or Formitopsis betulina Extracts and Their Influence on the Quality of Strawberries after Storage. Coatings 2024, 14, 260. [Google Scholar] [CrossRef]
  44. Ranjan, V.P.; Goel, S. Recyclability of polypropylene after exposure to four different environmental conditions. Resour. Conserv. Recycl. 2021, 169, 105494. [Google Scholar] [CrossRef]
  45. Prabowo, I.; Pratama, J.N.; Chalid, M. The effect of modified ijuk fibers to crystallinity of polypropylene composite. IOP Conf. Ser. Mater. Sci. Eng. 2017, 223, 012020. [Google Scholar] [CrossRef]
  46. Svoboda, P.; Trivedi, K.; Stoklasa, K.; Svobodova, D.; Ougizawa, T. Study of crystallization behaviour of electron beam-irradiated polypropylene and high-density polyethylene. R. Soc. Open Sci. 2021, 8, 202250. [Google Scholar] [CrossRef]
  47. Jung, M.R.; Horgen, F.D.; Orski, S.V.; Rodriguez C., V.; Beers, K.L.; Balazs, G.H.; Jones, T.T.; Work, T.M.; Brignac, K.C.; Royer, S.-J.; et al. Validation of ATR FT-IR to identify polymers of plastic marine debris, including those ingested by marine organisms. Mar. Pollut. Bull. 2017, 127, 704–716. [Google Scholar] [CrossRef]
  48. Gallart-Mateu, D.; Largo-Arango, C.D.; Larkman, T.; Garrigues, S.; de la Guardia, M. Fast authentication of tea tree oil through spectroscopy. Talanta 2018, 189, 404–410. [Google Scholar] [CrossRef]
  49. Da Silva, M.N.; de Matos Fonseca, J.; Feldhaus, H.K.; Soares, L.S.; Valencia, G.A.; de Campos, C.E.M.; Di Luccio, M.; Monteiro, A.R. Physical and morphological properties of hydroxypropyl methylcellulose films with curcumin polymorphs. Food Hydrocoll. 2019, 97, 105217. [Google Scholar] [CrossRef]
Applsci 15 10017 g001
Figure 1. PP film (A) and PP film covered with the active coating (B).
Figure 1. PP film (A) and PP film covered with the active coating (B).
Applsci 15 10017 g001
Applsci 15 10017 sch001
Scheme 1. Graphical representation of both methods used for assessing antiviral activity of the coatings.
Scheme 1. Graphical representation of both methods used for assessing antiviral activity of the coatings.
Applsci 15 10017 sch001
Applsci 15 10017 g002
Figure 2. The influence of HPMC coating with TTO on S. aureus growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001.
Figure 2. The influence of HPMC coating with TTO on S. aureus growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001.
Applsci 15 10017 g002
Applsci 15 10017 g003
Figure 3. The influence of HPMC coating with TTO on B. cereus growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001.
Figure 3. The influence of HPMC coating with TTO on B. cereus growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001.
Applsci 15 10017 g003
Applsci 15 10017 g004
Figure 4. The influence of HPMC coating with TTO on E. coli growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001.
Figure 4. The influence of HPMC coating with TTO on E. coli growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001.
Applsci 15 10017 g004
Applsci 15 10017 g005
Figure 5. The influence of HPMC coating with TTO on C. albicans growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001; ns—p > 0.5.
Figure 5. The influence of HPMC coating with TTO on C. albicans growth. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001; ns—p > 0.5.
Applsci 15 10017 g005
Applsci 15 10017 g006
Figure 6. The influence of HPMC coating with TTO on Φ6 titer. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001; ns—p > 0.5.
Figure 6. The influence of HPMC coating with TTO on Φ6 titer. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film. One-way ANOVA; ****—p < −0.0001; ns—p > 0.5.
Applsci 15 10017 g006
Applsci 15 10017 g007
Figure 7. The OD over time for the P. syringae after 15 h of incubation. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film.
Figure 7. The OD over time for the P. syringae after 15 h of incubation. C—PP film; QC—Q-SUN irradiated PP film; AC—HPMC coating with TTO on surface of PP film; QAC—Q-SUN irradiated, HPMC coating with TTO on surface of PP film.
Applsci 15 10017 g007
Applsci 15 10017 g008
Figure 8. SEM micrographs of PP film surface (A) before irradiation; (B) after 24 h of Q-SUN irradiation.
Figure 8. SEM micrographs of PP film surface (A) before irradiation; (B) after 24 h of Q-SUN irradiation.
Applsci 15 10017 g008
Applsci 15 10017 g009
Figure 9. SEM micrographs of PP film coated with the coating containing TTO surface (A) before irradiation; (B) after 24 h of Q-SUN irradiation.
Figure 9. SEM micrographs of PP film coated with the coating containing TTO surface (A) before irradiation; (B) after 24 h of Q-SUN irradiation.
Applsci 15 10017 g009
Applsci 15 10017 g010
Figure 10. P. syringae culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the neat PP films).
Figure 10. P. syringae culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the neat PP films).
Applsci 15 10017 g010
Applsci 15 10017 g011
Figure 11. P. syringe culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the Q-SUN-irradiated neat PP films).
Figure 11. P. syringe culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the Q-SUN-irradiated neat PP films).
Applsci 15 10017 g011
Applsci 15 10017 g012
Figure 12. P. syringe culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the coating with TTO).
Figure 12. P. syringe culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the coating with TTO).
Applsci 15 10017 g012
Applsci 15 10017 g013
Figure 13. P. syringe culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the Q-SUN-irradiated coating with TTO).
Figure 13. P. syringe culture after its 15 h cultivation with Φ6 phage (after prior incubation of Φ6 with the Q-SUN-irradiated coating with TTO).
Applsci 15 10017 g013
Applsci 15 10017 g014
Figure 14. The FTIR spectra of PP film; (A) before Q-SUN irradiation; (B) after Q-SUN irradiation.
Figure 14. The FTIR spectra of PP film; (A) before Q-SUN irradiation; (B) after Q-SUN irradiation.
Applsci 15 10017 g014
Applsci 15 10017 g015
Figure 15. The FTIR spectra of HPMC coating with TTO; (A) before Q-SUN irradiation; (B) after Q-SUN irradiation.
Figure 15. The FTIR spectra of HPMC coating with TTO; (A) before Q-SUN irradiation; (B) after Q-SUN irradiation.
Applsci 15 10017 g015
Applsci 15 10017 g016
Figure 16. The FTIR spectra of: (A) non-coated and coated PP film; (B) irradiated and non-irradiated HPMC coating with TTO.
Figure 16. The FTIR spectra of: (A) non-coated and coated PP film; (B) irradiated and non-irradiated HPMC coating with TTO.
Applsci 15 10017 g016
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Jankowski, W.; Mizielińska, D.; Mizielińska, M. Influence of Q-SUN Irradiation on Antimicrobial and Antiviral Activity of Tea Tree Oil-Based Coatings on Polypropylene Films. Appl. Sci. 2025, 15, 10017. https://doi.org/10.3390/app151810017

AMA Style

Jankowski W, Mizielińska D, Mizielińska M. Influence of Q-SUN Irradiation on Antimicrobial and Antiviral Activity of Tea Tree Oil-Based Coatings on Polypropylene Films. Applied Sciences. 2025; 15(18):10017. https://doi.org/10.3390/app151810017

Chicago/Turabian Style

Jankowski, Wojciech, Dobrosława Mizielińska, and Małgorzata Mizielińska. 2025. "Influence of Q-SUN Irradiation on Antimicrobial and Antiviral Activity of Tea Tree Oil-Based Coatings on Polypropylene Films" Applied Sciences 15, no. 18: 10017. https://doi.org/10.3390/app151810017

APA Style

Jankowski, W., Mizielińska, D., & Mizielińska, M. (2025). Influence of Q-SUN Irradiation on Antimicrobial and Antiviral Activity of Tea Tree Oil-Based Coatings on Polypropylene Films. Applied Sciences, 15(18), 10017. https://doi.org/10.3390/app151810017

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop