Search Results (124)

Crystalline TiO₂ films were synthesized on hydrophilic glass substrates by Peroxo sol–gel and sedimentation (S1–S4) and compared with conventional sol–gel protocols (S5–S10). The films were deposited on soda-lime glass and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and UV–Vis absorption. Photocatalytic activity was evaluated through the inactivation of multidrug-resistant Escherichia coli and Salmonella Typhimurium, and the removal of chemical oxygen demand (COD) from greywater under UV irradiation. The obtained films exhibited anatase crystallinity, crystallite sizes of ~60 nm, and grain sizes between 1.5 and 3.0 µm. S1 films showed a bandgap of 3.26 eV (380 nm). Under UV exposure, S1 reduced E. coli and S. Typhimurium by 4.78 and 3.00 Log₁₀ units, respectively, at pH 5.0 after 30 min, while COD decreased to 380 mg L⁻¹ compared to 433 mg L⁻¹ with UV photolysis alone. Increasing TiO₂ loading and extending irradiation to 120 min further enhanced bacterial inactivation (93 and 78% for E. coli and S. Typhimurium), COD (33%), NH₄⁺ (90%), and H₂S (89%) oxidation, outperforming UV-light controls. These results indicate that S1 films exhibited superior crystallinity, photocatalytic performance, and bacterial inactivation compared to other protocols, although complete mineralization was not achieved. Full article

Antimicrobial Blue Light (aBL) can be used to control the growth of pathogens in several applicative fields, from sanitization of inert surfaces to human skin treatment and from industry to food. Though the mechanism of action is still unknown, it has been hypothesized that specific wavelengths can activate potential endogenous photosensitizers in microbial cytoplasm and/or envelope. In turn, this photooxidative stress could induce inactivation of macromolecules resulting in bacterial killing. In this work, we investigated the effect of radiometric parameters of light at 410 nm on Escherichia coli K-12 MG1655, a strain rather tolerant to blue light irradiation. Interestingly, by changing the radiometric parameters of aBL protocol, different rates of killing were observed. Irradiation at 100 J/cm² caused a variable antimicrobial effect depending on the irradiance values. We observed an “irradiance effect”: namely, at higher irradiance values, the inhibitory effect is reduced. On the other hand, at increasing fluences the bactericidal rate increases. In addition, the shift from continuous to pulsed light could enhance the antimicrobial activity of protocols using higher irradiance values. Taken together, these results underline the importance of defining radiometric parameters to ensure the efficacy of aBL treatments and emphasize the importance of further research into the aBL mechanism. 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

Antimicrobial resistance (AMR) is one of the most critical challenges to global public health in the 21st century, posing a significant threat to healthcare systems and human health due to treatment failure and high mortality. The World Health Organization (WHO) estimates that, without effective interventions, AMR-associated infections could cause 10 million deaths annually and economic losses of up to 100 trillion US dollars by 2050. The rapid spread of drug-resistant strains, especially in hospital and community settings, has significantly reduced the efficacy of traditional antibiotics. With the continuous advancements in relevant research, bacteriophage (Phage) therapy is constantly innovating in the antimicrobial field. The application of frontier technologies, such as phage cocktails and engineered phages, has significantly enhanced the broad spectrum and high efficiency of phage therapy, which is gradually becoming a new generation of tools to replace antibiotics and effectively combat pathogenic bacteria. However, phage therapy is facing several challenges, including phage inactivation by gastric acid, enzymes, ultraviolet light, and mechanical stress, as well as the potential risk of bacterial phage resistance. Advanced encapsulation technologies such as electrospun fibers, liposomes, chitosan nanoparticles, and electrospray provide solutions to these problems by protecting phage activity and enabling controlled release and targeted delivery. This review addresses phage therapeutic studies of Salmonella, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes, summarizes the recent advances in phage research, and details the current development and applications of encapsulated phage technologies across various delivery modes. Full article

Photocatalytic pathogen inactivation is gaining increasing importance due to the rising number of microbial species resistant to conventional antibacterial agents. Titanium dioxide (TiO₂)-based photocatalysts have emerged as a promising solution, being not only potent antibacterial agents but also environmentally friendly and capable of simultaneously degrading organic pollutants. This review summarizes recent advances in the antibacterial performance of different TiO₂ modifications, including commercial nanopowders, nanoparticles with various morphologies, thin films, composites, and polymer-supported nanostructures, all primarily activated under UV light. Given the limited ability of pristine TiO₂ to harvest solar radiation, we also highlight the most recent strategies for designing visible-light-responsive TiO₂, such as doping, incorporation of plasmonic metal nanoparticles, formation of heterostructures, and interfacial charge transfer complexes. In addition, we discuss the fundamental structural features of TiO₂, the mechanisms of reactive oxygen species (ROS) generation involved in bacterial inactivation, and kinetic models describing antibacterial efficiency. These insights aim to advance the understanding and development of eco-friendly, cost-effective, and sustainable photocatalytic disinfection technologies. 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

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

Municipal wastewaters pose a severe risk to the environment and human health when discharged untreated. This is due to their high content of pathogens, such as viruses and bacteria, which can cause diseases like cholera. Herein, the research and development of porphyrin-modified polyethersulfone (PES) ultrafiltration (UF) membranes was conducted to improve bacterial inactivation in complex municipal wastewater and enhance the fouling resistance and filtration performance. The synthesis and fabrication of porphyrin nanofillers and the resultant membrane characteristics were studied. The incorporation of porphyrin-based nanofillers improved the membrane’s hydrophilicity, morphology, and flux (247 Lm⁻² h⁻¹), with the membrane contact angle (CA) decreasing from 90° to ranging between 58° and 50°. The membrane performance was monitored for its flux, antifouling properties, reusability potential, municipal wastewater, and humic acid. The modified membranes demonstrated an effective application in wastewater treatment, achieving notable antibacterial activity, particularly under light exposure. The In-BP@SW/PES membrane demonstrated effective antimicrobial photodynamic effects against both Gram-positive S. aureus and Gram-negative E. coli. It achieved at least a 3-log reduction in bacterial viability, meeting Food and Drug Administration (FDA) standards for efficient antimicrobial materials. Among the variants tested, membranes modified with In-PB@SW nanofillers exhibited superior antifouling properties with flux recovery ratios (FRRs) of 78.9% for the humic acid (HA) solution and 85% for the municipal wastewater (MWW), suggesting a strong potential for long-term filtration use. These results highlight the promise of porphyrin-functionalized membranes as multifunctional tools in advanced water treatment technologies. Full article

Microbial contamination of food can lead to faster spoilage and infections. Therefore, disinfection processes are required that have a low detrimental effect on the nutritional content. Concerning radiation disinfection, two spectral ranges have recently become important. The Far-UVC spectral range, with a wavelength below 230 nm and visible violet light. In this study, leaf spinach was used to investigate the extent to which these radiations inactivate Escherichia coli, but also to determine if the vitamin C or chlorophyll content was reduced. Frozen spinach leaves (Spinacia oleracea) were contaminated with E. coli × pGLO and irradiated with either a 222 nm krypton chloride lamp or 405 nm LEDs. The achieved bacterial reduction was determined by plating the irradiated samples on agar plates and subsequent colony counting. The vitamin C concentration was determined by means of redox titration, and the concentrations of chlorophyll a and chlorophyll b were determined using spectrometry. Both irradiations exhibited a strong antimicrobial impact on E. coli. The average log reduction doses were about 19 mJ/cm² (222 nm) and 87 J/cm² (405 nm), respectively. The vitamin C concentration decreased by 30% (222 nm) or 20% (405 nm), and the chlorophyll concentrations decreased by about 25%. Both irradiation approaches are able to substantially reduce microorganisms on spinach leaves by two orders of magnitude, but this is associated with a reduction in the nutrient content. Full article

The emergence of multidrug-resistant (MDR) bacteria and biofilm-associated infections has created a significant hurdle for conventional antibiotics, prompting the exploration of alternative strategies. Photodynamic therapy (PDT), a technique that utilizes photosensitizers activated by light to produce ROS, has emerged as a beacon of hope in the fight against MDR microorganisms. Among the natural photosensitizers, hypocrellins (A and B) have shown remarkable potential with their dual-mode photodynamic action, generating ROS via both Type I (electron transfer) and Type II (singlet oxygen) pathways. This unique action disrupts bacterial biofilms and inactivates MDR pathogens. The amphiphilic nature of hypocrellins further enhances their promise, enabling deep biofilm penetration and ensuring potent antibacterial effects even in hypoxic environments, surpassing the capabilities of synthetic photosensitizers. This study critically examines the antimicrobial properties of hypocrellin-based PDT, emphasizing its mechanisms, advantages over traditional antibiotics, and effectiveness against MDR pathogens. Comparative analysis with other photosensitizers, the role of nanotechnology-enhanced delivery systems, and future clinical applications are explored. Its combination with nanotechnology enhances therapeutic outcomes, providing a viable alternative to conventional antibiotics. Further clinical research is essential to optimize its application and integration into antimicrobial treatment protocols. Full article

Free-standing copper oxide (Cu₂O)-copper hydroxide (Cu(OH)₂) nanocomposites with enhanced catalytic and antibacterial functionalities were synthesized on copper mesh using a green method based on spinach leaf extract and glycerol. EDX, SEM, and TEM analyses confirmed the chemical composition and morphology. The resulting Cu2O-Cu(OH)₂@Cu mesh exhibited notable hydrophobicity, achieving a contact angle of 137.5° ± 0.6, and demonstrated the ability to separate thick oils, such as HD-40 engine oil, from water with a 90% separation efficiency. Concurrently, its photocatalytic performance was evaluated by the degradation of methylene blue (MB) under a weak light intensity of 5 mW/cm², achieving 85.5% degradation within 30 min. Although its application as a functional membrane in water treatment may raise safety concerns, the mesh showed significant antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria under both dark and light conditions. Using the disk diffusion method, strong bacterial inhibition was observed after 24 h of exposure in the dark. Upon visible light irradiation, bactericidal efficiency was further enhanced—by 17% for S. aureus and 2% for E. coli. These findings highlight the potential of the Cu₂O-Cu(OH)₂@Cu microfibers as a multifunctional membrane for industrial wastewater treatment, capable of simultaneously removing oil, degrading organic dyes, and inactivating pathogenic bacteria through photo-assisted processes. Full article

Recently, the urgency of combating antibiotic-resistant bacteria, viruses, and other pathogens has dramatically increased. With the development of nanotechnology, significant hopes are placed on nanoparticles with antimicrobial properties. The efficiency of such materials can be significantly enhanced through light-activated processes. In this study, we prepared composite ZnO-Ag nanoparticles and tested their ability to inhibit Staphylococcus aureus bacteria. The composite ZnO-Ag nanoparticles were fabricated using pulsed laser ablation of Zn and Ag targets in water using a nanosecond pulsed laser. During antibacterial tests, light-enhanced activation of the nanoparticles was achieved using low-power near UV (375 nm) and blue visible (410 nm) LED irradiation. For comparison, similar laser-fabricated ZnO nanoparticles were also tested. The combined use of nanoparticles and LED irradiation significantly increased the generation of reactive oxygen species. As a result, low nanoparticle concentrations (0.05 g/L) and low-power LED irradiation (0.17–0.22 W) significantly reduced the concentration of Staphylococcus aureus bacteria, including experiments with visible light irradiation. Compared to their ZnO counterparts, the use of ZnO-Ag composite particles led to an additional increase in antimicrobial activity. Full article

Background/Objectives: Photothermal therapy (PTT) is an emerging minimally invasive strategy in biomedicine that converts near-infrared (NIR) light into localized heat for the targeted inactivation of pathogens and tumor cells. Methods and Results: In this study, we report the synthesis and characterization of thermoresponsive nanogels composed of poly (N-isopropylacrylamide-co-N-isopropylmethylacrylamide) (PNIPAM-co-PNIPMAM) semi-interpenetrated with polypyrrole (PPy), yielding monodisperse particles of 377 nm diameter. Spectroscopic analyses—including ¹H-NMR, FTIR, and UV-Vis—confirmed successful copolymer formation and PPy incorporation, while TEM images revealed uniform spherical morphology. Differential scanning calorimetry established a volumetric phase transition temperature of 38.4 °C, and photothermal assays demonstrated a ΔT ≈ 10 °C upon 10 min of 850 nm NIR irradiation. In vitro antimicrobial activity tests against Pseudomonas aeruginosa (ATCC 15692) showed a dose-time-dependent reduction in bacterial viability, with up to 4 log CFU/mL. Additionally, gentamicin-loaded nanogels achieved 38.7% encapsulation efficiency and exhibited stimulus-responsive drug release exceeding 75% under NIR irradiation. Conclusions: Combined photothermal and antibiotic therapy yielded augmented bacterial killing, underscoring the potential of PPy-interpenetrated nanogels as smart, dual-mode antimicrobials. Full article

Klebsiella pneumoniae is a Gram-negative, encapsulated bacterium recognized by the World Health Organization (WHO) as a critical priority for new therapeutic strategies due to its increasing multidrug resistance (MDR). Antimicrobial photodynamic therapy (aPDT) has emerged as a promising alternative to antibiotics, exhibiting a broad spectrum of action and multiple molecular targets, and has been proposed for the treatment of clinically relevant infections such as pneumonia. However, despite excellent in vitro photodynamic inactivation outcomes, the success of in vivo therapy still faces challenges, particularly due to the presence of lung surfactant (LS) in the alveoli. LS entraps photosensitizers, preventing these molecules from reaching microbial targets. This study investigated the potential of indocyanine green (ICG) in combination with the biocompatible polymer Gantrez™ AN-139 for the photoinactivation of K. pneumoniae. Initial in vitro experiments demonstrated that aPDT with ICG alone is effective against K. pneumoniae in a concentration- and light dose-dependent manner, achieving total eradication at 75 µg/mL of ICG and 150 J/cm² of 808 nm light. When aPDT was performed with similar parameters in the presence of LS, no bacterial killing was observed. However, a significant synergistic effect was observed when ICG (25 µg/mL) was combined with a low concentration of Gantrez™ AN-139 (0.5% m/v) in the presence of dipalmitoylphosphatidylcholine (DPPC), the main component of LS. This formulation resulted in a substantial reduction (3.6 log₁₀) in K. pneumoniae viability. These findings highlight the potential of Gantrez™ AN-139 as an efficient carrier to enhance the efficacy of ICG-mediated aPDT against K. pneumoniae, even in the presence of lung surfactant, a necessary step before the in vivo experiments. Full article