Search Results (138)

This study aimed to develop natural, safe, and effective antimicrobial packaging materials for extending the shelf life of chilled pork during refrigeration. Emodin-chitosan (Em-Cs) composite films with varied concentrations were developed by combining the casting method with photodynamic inactivation technology, utilizing chitosan as the matrix and emodin as the functional photosensitizer for active packaging. The optical, mechanical, and barrier properties of the composite films were examined. The inhibitory effects of the samples on Escherichia coli, Salmonella Derby, Staphylococcus aureus, and Pseudomonas fragi under 450 nm blue light irradiation were evaluated. The results demonstrated that the Em-Cs composite film exhibited excellent transparency, mechanical strength, and water barrier properties, with good compatibility between emodin and chitosan. Under light irradiation, the composite film generates reactive oxygen species (ROS), whose bactericidal efficacy depends on the concentration of emodin and the duration of light exposure. When applied to chilled pork packaging, this composite film inhibited bacterial growth within the meat for 10 days, effectively retarding pH increase, lipid oxidation, and volatile basic nitrogen accumulation. The present study proposes a novel methodology for the application of photodynamic technology in the context of food preservation, and it presents a new type of natural antimicrobial packaging material for the preservation of chilled pork. Full article

The growing threat of antibiotic-resistant bacteria necessitates the development of alternative antimicrobial strategies. This study investigated the design and evaluation of novel photodynamic agents based on Rose Bengal (RB) conjugated to two plant lectins, Pisum sativum agglutinin (PSA) and Laburnum anagyroides agglutinin (LABA), for targeted photodynamic inactivation of Gram-positive and Gram-negative bacteria. Both conjugates demonstrated high singlet oxygen quantum yields compared with free RB. Antibacterial efficacy was assessed against methicillin-sensitive and methicillin-resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella paratyphi B under white LED illumination. PSA-RB exhibited superior bactericidal activity against all strains, whereas LABA-RB showed strain-specific efficacy, particularly against Gram-negative species. A binary mixture of PSA-RB and LABA-RB synergistically inactivated both MSSA and MRSA at RB concentrations of 6–10 nM and light doses of 3.1–7.8 J/cm². Complete killing of E. coli and S. paratyphi B was achieved at approximately half the RB concentrations needed for individual conjugates. PSA-RB activity primarily drove the inactivation of P. aeruginosa. Uptake studies revealed significantly enhanced accumulation of lectin-conjugated RB compared to free RB, with synergistic uptake observed for the conjugate mixture. These results suggest that lectin-based RB conjugates are effective antibacterial agents for photodynamic treatment, especially via the dual-targeting method. Full article

The article describes the interaction between 4-amino-1,8-naphthalic anhydride and the terminal amine groups of the first-generation poly(amidoamine) (PAMAM) dendrimer. Cotton fabric was treated with the newly obtained photoactive dendrimer (DA) to achieve its antimicrobial photodynamic inactivation. The photodynamic inactivation method is an innovative approach in which, upon irradiation with visible light, photosensitizers generate highly reactive oxygen species, specifically singlet oxygen (¹O₂), which destroys microbial cells. In the dark, the DA dendrimer strongly inhibits the development of the model bacteria Bacillus cereus (a Gram-positive bacterium) and Pseudomonas aeruginosa (a Gram-negative bacterium) in solution. Upon irradiation with visible light, the inhibition is significantly enhanced, achieving almost complete inactivation of B. cereus and 94% of P. aeruginosa. Cotton fabric was treated with the DA dendrimer at two concentrations (0.15% and 0.30% weight of fabric). It was found that the dendrimer molecules are adherent to the cellulose fiber surfaces and do not leach in washing. Treatment of the fabric with DA partially increases its hydrophobicity, which prevents the adhesion of some bacteria. In the dark, the treated fabric shows weak antibacterial activity because the dendrimer DA molecules are attached to the textile surface, and inactivation depends solely on the microorganism’s surface contact. However, upon irradiation, a significant increase in the fabric’s antimicrobial activity is observed, as the fixed dendrimer participates in the release of singlet oxygen, which effectively attacks microorganism cell membranes and components. For the fabric with the higher concentration (DA30), 94% inactivation of B. cereus and 89% inactivation of P. aeruginosa were achieved. Thus, a synergistic effect between photodynamic activity and increased hydrophobicity was achieved, making the modified cotton fabric an example of a high-tech textile with permanent, renewable disinfection. Full article

This review explores the synergistic integration of edible coatings and non-thermal preservation technologies as a multifaceted approach to maintaining food quality, safety, and sustainability. Edible coatings—composed of polysaccharides, proteins, lipids, or composite biopolymers—serve as biodegradable barriers that control moisture, gas, and solute transfer while acting as carriers for bioactive compounds such as antimicrobials and antioxidants. Meanwhile, non-thermal techniques, including high-pressure processing, cold plasma, ultrasound, photodynamic inactivation, modified atmosphere packaging, and irradiation, offer microbial inactivation and enzymatic control without compromising nutritional and sensory attributes. When combined, these technologies exhibit complementary effects: coatings enhance the stability of bioactives and protect surface quality, while non-thermal treatments boost antimicrobial efficacy and promote active compound penetration. The review highlights their comparative advantages over individual treatments—improved microbial inhibition, nutrient retention, and sensory quality. It further discusses the possible mechanisms through which edible coatings and selected hurdles induced microbial decontamination. Finally, the study identified major drawbacks and provided strategic recommendations to overcome these limitations, including optimizing coating formulations for specific food matrices, tailoring process parameters to minimize adverse physicochemical changes, and conducting pilot-scale validations to bridge the gap between laboratory success and industrial application. Full article

Chronic wound infections associated with resistant polymicrobial biofilms are often refractory to conventional therapies with sustained healing time. This study evaluated the efficacy of non-antibiotic treatments including Methylglyoxal—MGO—Light-Emitting Diode—LED—and Complex Magnetic Fields—CMFs—alone/combined against the biofilms of two polymicrobial mixes (MIX 1, MIX 2) containing S. aureus, P. aeruginosa and C. albicans using the Lubbock chronic wound biofilm model. At 24 h after treatment, the effects were evaluated by (i) CFU/mg reduction, (ii) Confocal Laser Scanning Microscopy—CLSM—and (iii) Scanning Electron Microscopy—SEM. All treatments significantly reduced biofilms in terms of CFU/mg in both mixes versus the controls, 24 h after treatment. MGO showed remarkable activity, especially against P. aeruginosa. In MIX 1, LED/MGO + LED was highly effective against C. albicans. The combinations MGO + LED/MGO + CMFs enhanced the antibiofilm activity compared to each single treatment against S. aureus and P. aeruginosa, in both MIX1/MIX2. CLSM and SEM analysis showed biofilm disaggregation and reduction in cell viability with combined treatments, and Candida hyphal inhibition after CMFs application. In conclusion, the results demonstrate that MGO, alone or combined with LED or CMFs, shows high efficacy against resistant biofilms in the LCWB model 24 h after treatment, and encourage further studies on potential non-antibiotic and eco-friendly strategies as future alternative therapeutic approaches for chronic wound infections. Full article

Photodynamic inactivation (PDI) represents a promising strategy to overcome bacterial resistance by combining light, oxygen, and a photosensitizer (PS) to generate reactive oxygen species (ROS) that damage essential cellular components. Combining PDI with conventional antibiotics (ATBs) may further enhance bacterial eradication through complementary mechanisms. In this study, the tetracationic 5,10,15,20-tetra(4-N,N,N-trimethylammoniophenyl)porphyrin (TMAP⁴⁺) was evaluated in combination with ATBs: ampicillin (AMP) and rifampicin (RIF) against Staphylococcus aureus and cephalexin (CFX) against Escherichia coli. The photostability of all agents was assessed under the experimental irradiation conditions, and no evidence of physical interaction between TMAP⁴⁺ and the ATBs was detected. AMP and CFX remained photostable, while RIF exhibited only minimal photodegradation under white light, confirming its stability during PDI treatments. The antimicrobial assays revealed that irradiation significantly enhanced the bactericidal activity of TMAP⁴⁺. When combined with ATBs, photoactivated TMAP⁴⁺ led to a pronounced reduction in the minimum inhibitory concentration (MIC) values of AMP and RIF for S. aureus and of CFX for E. coli, indicating additive effects. Growth curve analyses corroborated these results, showing delayed bacterial growth and decreased maximal optical densities in the combined treatments compared to single agents. Overall, these findings demonstrate that the photodynamic process can potentiate the antimicrobial effect of conventional ATBs without compromising their stability, supporting the potential of PS–ATB combination therapies as a valuable approach to improve antibacterial efficacy and mitigate ATB resistance. Full article

This study reports the development of chitosan-based (CS) films incorporating riboflavin (RF) as a natural photosensitizer to create sustainable, light-activated antimicrobial packaging materials. The films were prepared by solvent casting, and their photochemical behavior under blue LED light (450 nm) was investigated, including RF photodegradation kinetics and structural changes in the film-forming solution analyzed by ¹H NMR spectroscopy. Mechanical, thermal, optical, and barrier properties were also characterized to assess packaging suitability. Upon illumination, CS/RF films generated reactive oxygen species, particularly singlet oxygen (¹O₂), leading to visible color changes and significant antimicrobial activity against Pseudomonas fluorescens. Bacterial growth was reduced by up to 97% after 120 min of irradiation (0.92 J cm⁻²), with efficacy observed at both room temperature and 4 °C. The incorporation of RF did not alter the films’ mechanical properties, while thermal stability was preserved, optical transparency was modulated, and excellent oxygen barrier performance was maintained, although water vapor permeability remained moderate. These findings demonstrate that CS/RF films combine functionality and sustainability, offering a promising strategy for extending food shelf life through light-activated antimicrobial action. Validation under real storage conditions is recommended to confirm their potential in diverse food systems. Full article

Photodynamic therapy (PDT) is a promising antimicrobial strategy whose efficacy depends largely on the photosensitizers (PSs) used. While conventional PDT relies on a single PS, recent studies suggest that combining different PSs may improve outcomes by introducing complementary mechanisms. However, such combinations also add complexity, as timing, composition, and PS interactions must be considered alongside bacterial structures, uptake pathways, and light dosimetry. This study investigated the effects of PSs, methylene blue (MB), Photodithazine (PDZ), and their combinations on the PDT of Gram-negative bacterium Klebsiella pneumoniae. MB-mediated PDT demonstrated greater antibacterial effectiveness than PDZ-PDT. The combination of MB and PDZ produced varying results. When applied simultaneously, PDZ dose-dependently decreased MB’s antibacterial activity. Sequential treatment with PDZ followed by MB showed only slight antagonism compared to MB alone, while the reverse order (MB → PDZ) nearly abolished MB’s activity. Since both PSs are activated at the same wavelength (660 nm), their combined use was not additive. Photobleaching was performed on individuals and combined PSs to compare inactivation results with changes in chemical properties under red light (660 nm). This study highlights the limitations of using two photosensitizers together in antimicrobial photodynamic therapy and emphasizes the need for further optimization of combination protocols. Full article

Clavibacter michiganensis causes significant crop losses in tomatoes, and the disease may be transferred by plant seeds. This study evaluates the efficacy of Photodynamic Inactivation (PDI) with a water-soluble hypericin derivative, developed as a complex with polyvinylpyrrolidone (high hypericin-loaded PVP, HHL-PVP), as a decontamination strategy for tomato seeds. HHL-PVP was chosen for its overall stability, as the complex remains stable in solution for over 950 days, maintains its absorption capacity after illumination with 200 J·cm⁻², and produces reactive oxygen species (ROS) even at concentrations as low as 1 µM. PDI against C. michiganensis with 5 μM HHL-PVP, 10 min drug to light interval (DLI), and illumination with red light (600–700 nm, 100 J·cm⁻²) exceeded the antimicrobial effect of a 99.9% reduction in liquid culture. Increasing the DLI to 24 h did not alter the photokilling effect. A 14 h light/10 h dark cycle in white light (118 J·cm⁻²) with 0.3 µM HHL-PVP inhibited the growth of C. michiganensis by more than 6 log₁₀ steps, indicating that HHL-PVP has a stable and long-lasting photokilling effect. The combination of HHL-PVP with potassium iodide (KI, 100 mM) completely eradicated C. michiganensis in liquid culture with red and white light, indicating KI’s role in enhancing phototoxicity. Tomato seed photodynamic decontamination using 1.0 µM HHL-PVP activated by 200 J·cm⁻² white light inactivated >5 log₁₀ of C. michiganensis, without diminishing sprouting. An addition of 100 mM KI increased the percentage of sprouted seedlings and inactivated 100% of bacteria. These results demonstrate that HHL-PVP-mediated PDI combined with KI could be highly effective as a preventative strategy in tomato protection against C. michiganensis. Full article

Food spoilage and contamination are major global challenges, reducing food quality, safety, and availability, causing significant economic losses. This study evaluates the photodynamic and sonodynamic antibacterial activities of grape leaf extracts from Beer and Hanut Orcha varieties. The extracts were tested against Staphylococcus aureus and Escherichia coli under illumination and ultrasonic activation. The results demonstrated that the photodynamic and sonodynamic treatments significantly enhanced the antibacterial efficacy of the extracts when higher concentrations of the extracts and prolonged exposure led to complete bacterial eradication. Separation of the extracts using RP-18 cartridges (Yicozoo Energy Technology Co., Ltd., Xi’an, China) enabled us to get an active fraction containing components responsible for antimicrobial effects. Singlet oxygen generation measurements confirmed the involvement of reactive oxygen species in bacterial inactivation under illumination. Using HPLC/MS, the active components responsible for the photodynamic properties of the extracts were identified as quercetin 3’-O-glucuronide and pheophorbide a. The findings suggest that these natural extracts, in combination with photodynamic and sonodynamic activation, represent promising alternatives to conventional antibiotics. Further studies should focus on the isolation of active individual compounds, the improvement of treatment parameters, and the investigation of molecular mechanisms to facilitate the development of practical applications in medicine and food preservation. Full article

Photodynamic inactivation and antimicrobial photodynamic therapy (PDI/APDT) based on the toxic properties of reactive oxygen species (ROS), which are generated by a number of photoexcited dyes, are promising for preventing and treating infections, especially those associated with drug-resistant pathogens. The negatively charged bacterial cell surface attracts polycationic photosensitizers, which contribute to the vulnerability of the bacterial plasma membrane to ROS. The integrity of the plasma membrane is critical for the viability of the bacterial cell. Polycationic phthalocyanines are regarded as promising photosensitizers due to their high quantum yields of ROS generation (mainly singlet oxygen), high extinction coefficients in the far-red spectral range, and low dark toxicity. For application in PDI/APDT, the wide range of possibilities of modifying the chemical structure of phthalocyanines is particularly valuable, especially by introducing various peripheral and non-peripheral substituents into the benzene rings. Depending on the type and location of such substituents, it is possible to obtain photosensitizers with different photophysical properties, photochemical activity, solubility in an aqueous medium, biocompatibility, and tropism for certain structures of photoinactivation targets. In this study, we tested novel water-soluble Zn (II) phthalocyanines bearing four 4-((diethylmethylammonium)methyl)phenoxy substituents with symmetric and asymmetric charge distributions for photodynamic antibacterial activity and compared them with those of water-soluble octacationic zinc octakis(cholinyl)phthalocyanine. The obtained results allow us to conclude that the studied tetracationic aryloxy-substituted Zn(II) phthalocyanines effectively bind to the oppositely charged cell wall of the Gram-negative bacteria E. coli. This finding is supported by data on bacteria’s zeta potential neutralization in the presence of phthalocyanine derivatives and fluorescence microscopy images of stained bacterial cells. Asymmetric substitution influences the aggregation and fluorescent characteristics but has little effect on the ability of the studied tetracationic phthalocyanines to sensitize the bioluminescent E. coli K12 TG1 strain. Both symmetric and asymmetric aryloxy-substituted phthalocyanines are no less effective in PDI than the water-soluble zinc octakis(cholinyl)phthalocyanine, a photosensitizer with proven antibacterial activity, and have significant potential for further studies as antibacterial photosensitizers. Full article

Fermented vegetables, which are valued for their distinctive organoleptic properties and nutritional profile, are susceptible to quality deterioration during processing and storage because microorganisms inhabit vegetable raw materials. The metabolic processes of these microorganisms may induce texture degradation, chromatic alterations, flavor diminution, and spoilage. Conventional inactivation methods employing thermal sterilization or chemical preservatives achieve microbial control through nonselective inactivation, inevitably compromising the regional sensory characteristics conferred by indigenous fermentative microbiota. Recent advances in existing antimicrobial technologies offer promising alternatives for selective microbial management in fermented vegetable matrices. Existing modalities, including cold plasma, electromagnetic wave-based inactivation (e.g., photodynamic inactivation, pulsed light, catalytic infrared radiation, microwave, and radio frequency), natural essential oils, and lactic acid bacterial metabolites, demonstrate targeted pathogen inactivation while maintaining beneficial microbial consortia essential for quality preservation when properly optimized. This paper explores the applications, mechanisms, and targeted microbes of these technologies in fermented vegetable ingredients, aiming to provide a robust theoretical and practical framework for the use of selective inactivation strategies to manage the fermentation process. By assessing their impact on the initial microbial community, this review aims to guide the development of methods that ensure product safety while safeguarding the characteristic flavor and quality of fermented vegetables. Full article

The increasing reliance on light-based antimicrobial technologies, such as antimicrobial blue light (aBL) and antimicrobial photodynamic inactivation (aPDI), underscores the urgent need to comprehend bacterial survival strategies beyond conventional resistance. Two key phenotypes—tolerance and resilience—have emerged as critical but often conflated mechanisms by which bacteria withstand oxidative and photodynamic stress. While tolerance refers to delayed bacterial killing without changes in MIC, resilience encompasses the active restoration of cellular function after transient stress exposure. Both phenomena may impair treatment outcomes and contribute to long-term persistence, even in the absence of genetic resistance. This review dissects the molecular mechanisms underlying tolerance and resilience, with a focus on their relevance to bacterial responses to reactive oxygen species generated by light-based or chemical stressors. The regulatory and effector overlap between these phenotypes is examined, including antioxidant defense systems, DNA repair pathways, and metabolic rewiring. Furthermore, the role of phenotypic heterogeneity and cross-stress protection in blurring the boundary between survival and recovery is discussed, highlighting challenges in experimental interpretation. Finally, the implications of these adaptive strategies are evaluated in the context of antimicrobial efficacy and safety, with an emphasis on kinetic assays and multidimensional profiling as tools to capture complex treatment outcomes. Clarifying the distinction between tolerance and resilience may help guide the development of robust and evolutionarily stable antimicrobial phototherapies. Full article

Yeasts of the genus Candida (C.) and the bacterium Staphylococcus aureus (S. aureus) are among the most common pathogens responsible for infections that are difficult to treat, including those resistant to standard therapy. In recent decades, this has become an increasing clinical problem. In response to the limitations of traditional procedures, antimicrobial photodynamic therapy (aPDT), which combines light, a photosensitizer, and oxygen, is gaining growing interest. The aim of this study was to evaluate the in vitro effectiveness of aPDT using a 635 nm diode laser in combination with toluidine blue O (TBO) against Candida spp. and S. aureus. Reference strains of C. albicans, C. glabrata, C. krusei, and S. aureus were subjected to aPDT. In phase I of this study, the optimal TBO incubation time was assessed with constant laser parameters. In phase II, the impact of the physical parameters of the laser, irradiation time, and output power, was analyzed, with the TBO incubation time set based on the phase I results, to evaluate the degree of microbial reduction (CFU/mL). Statistical analyses were then conducted to assess significance. TBO-mediated aPDT significantly reduced microbial viability, depending on incubation time and laser settings. The minimal effective incubation times were 10 min for Candida spp. and 5 min for S. aureus. The highest pathogen inactivation efficacy was observed at an output power of 400 mW and an irradiation time of 120 s. The use of the photosensitizer or laser alone did not result in significant antimicrobial effects. TBO-mediated aPDT may serve as an effective complement to conventional antimicrobial therapy and, in selected cases (e.g., drug resistance), has the potential to partially or fully replace it. The observed minimal effective incubation times provide a practical baseline, but further statistical comparisons are required to determine whether these durations are truly optimal. Full article

Hydrogel materials have become an efficient, bioactive, and multifunctional alternative with great potential for biomedical applications. In this work, photoactive films were successfully designed for optical processing, and their photoactivity was tested in photodynamic therapy (PDT), such as antimicrobial patches. The stimulus-response hydrogel films are made of a hydrophilic polymer based on vinyl monomers, specifically 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AAm), in a 1:1 molar ratio, along with the photochromic agent, 3,3-dimethylindolin-6′-nitrobenzoespiropirano (BSP), and a crosslinking agent, N,N’-methylenebisacrylamide (MBA). These hydrogel films were successfully created using the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (IRGACURE 2959), MBA, and BSP in different concentrations (0.1, 0.3, and 0.5 mol%), which were later tested in photodynamic therapy (PDT) with the photosensitizer Ru(bpy)₂²⁺ against Staphylococcus aureus. The results showed that, while free Ru(bpy)₂²⁺ needed concentrations of 4–8 µg/mL to eliminate methicillin-sensitive (MSSA) strains, only partial inactivation was achieved for methicillin-resistant (MRSA) strains. The addition of the hydrogel films with BSP improved their effectiveness, lowering the minimum inhibitory concentration (MIC) to 2 µg/mL to fully inactivate MSSA and MRSA strains. These findings demonstrate that the combined use of hydrogel films containing BSP and Ru(bpy)₂²⁺ within a hydrogel matrix not only boosts antimicrobial activity but also highlights the potential of these photoactive films as innovative photosensitive antimicrobial coatings. This synergistic effect of BSP and Ru(bpy)₂²⁺ indicates that these materials are promising candidates for next-generation antimicrobial coatings and creative photosensitive materials. Full article