Search Results (265)

Background/Objectives: The rapid emergence of multidrug-resistant (MDR) bacteria has increased the demand for non-antibiotic antibacterial strategies. Although photothermal therapy (PTT) and photodynamic therapy (PDT) are promising alternatives, each modality alone may show limited antibacterial efficacy. This study aimed to construct a flexible dual-light-responsive nanofibrous membrane integrating PTT and PDT for improved in vitro antibacterial activity against MDR bacteria. Methods: A silica nanofibrous membrane (SNF) was prepared by electrospinning followed by calcination. An Fe-doped sulfonated TpPa covalent organic framework (SCOF-Fe) was then grown in situ on the SNF surface via an interfacial diffusion strategy to obtain SNF@SCOF-Fe. The membrane was characterized in terms of morphology, structure, optical absorption, photothermal performance, Fe loading, Fe leaching, and reactive oxygen species (ROS) generation. In vitro antibacterial activity against supplier-reported MDR Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) was evaluated under 420 nm, 808 nm, and dual-light (420 + 808 nm) irradiation. Results: Fe doping broadened the optical absorption of the COF-functionalized membrane into the near-infrared region and improved its photothermal response. Under dual-light irradiation, SNF@SCOF-Fe generated singlet oxygen, superoxide radicals, and hydroxyl radicals, together with a greater temperature increase than the undoped membrane. Within 15 min, SNF@SCOF-Fe achieved antibacterial rates of 99.29% against E. coli and 99.62% against MRSA. In addition, controlled dual-light cytocompatibility testing yielded 78.76% viability in L929 fibroblasts and 82.86% viability in MC38 murine colon carcinoma cells after SNF@SCOF-Fe treatment. Conclusions: SNF@SCOF-Fe combines dual-light-triggered photothermal heating and ROS generation within a flexible nanofibrous membrane and demonstrated effective in vitro antibacterial activity against two representative resistant bacteria. These findings support further investigation of SNF@SCOF-Fe as a light-responsive antibacterial membrane in relevant in vitro and in vivo models. Full article

Porphyromonas gingivalis (P. gingivalis) is a primary pathogen in periodontitis, yet its elimination is limited by complex anatomical structures. Photodynamic therapy (PDT) is a promising adjunct, but its antimicrobial efficacy is compromised in the acidic microenvironment induced by P. gingivalis. Given that 2′,4′,5′,7′-tetraiodofluorescein (TIF) exhibits robust and stable photodynamic activity under acidic conditions, this study investigated the antibacterial effect of TIF-mediated PDT (TIF-PDT) against P. gingivalis. P. gingivalis ATCC 33277 was treated with TIF (5, 10, 20, and 40 μM), light (525 nm), or both. Reactive oxygen species (ROS) generation was assessed at pH 4.5 or 7.4. Bacterial viability and membrane integrity were evaluated by colony-forming unit (CFU) assay and LIVE/DEAD staining. CFU assays demonstrated that TIF-PDT groups achieved an approximately 4-log reduction in bacterial viability compared to the DEMI, Light, and TIF groups, with no dark cytotoxicity and light-alone effects. LIVE/DEAD staining revealed bright yellow fluorescence in the TIF-PDT (40 μM), indicating membrane damage and significantly lower survival rates than controls. TIF-PDT at 10, 20, and 40 μM produced ROS under both neutral and acidic conditions, exhibited low dark cytotoxicity, and demonstrated potent antibacterial activity against P. gingivalis in vitro, suggesting its potential as an acid-tolerant photosensitizer for periodontitis adjunctive therapy. Full article

Antimicrobial photodynamic therapy is a method that utilizes photodynamic inactivation of microorganisms exposed to a photosensitizer irradiated by a specific wavelength, followed by the formation of reactive oxygen species and subsequent oxidative stress. In contrast to antibiotics, which are generally efficient against specific microorganisms, photodynamic inactivation exhibits efficacy against a wide range of bacteria, representing a promising and non-invasive alternative to treating infections caused by pathogens of different origins. This study compares the antibacterial efficacy of five different photosensitizers, including TMPyP, Protoporphyrin IX, PdTPPS₄, Methylene Blue, and ZnPCS₂, against eight representatives of various pathogens, including Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa, Gram-positive bacteria Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium, MRSA and Bacillus subtilis. An optimal irradiation protocol was developed based on growth curve measurements involving double irradiation. To induce the photodynamic effect, we utilized LED emitters with wavelengths of 414 nm and 660 nm, chosen to align with the photophysical properties of the photosensitizers. Additionally, the research included assessments of the radiation’s phototoxicity and the photosensitizers’ dark toxicity against specific microorganisms. The optical properties of the photosensitizers were analyzed using absorption spectrophotometry. The effectiveness of photodynamic inactivation was assessed by determining the minimum inhibitory and bactericidal concentrations. This study aimed to identify the most suitable photosensitizer for clinical application, considering the toxicity of the photosensitizer, the radiant exposure, and its efficacy in photodynamic inactivation. Full article

Carbon quantum dots (CQDs) have attracted considerable attention as versatile fluorescent nanomaterials in the domains of food safety and preservation, primarily due to their tunable photoluminescence, high aqueous dispersibility, and favorable biocompatibility. Although numerous reviews have documented the synthesis and extensive applications of CQDs, a focused critical assessment specifically addressing how rational surface functionalization and heteroatom doping impact their performance within complex food matrices remains absent. This review provides a targeted analysis of the interplay between the functional design of CQDs, including both surface group engineering and elemental doping, and their practical efficacy in food-related applications. Initially, a concise overview of the fundamental aspects of CQDs relevant to their functionality is presented, emphasizing the origin and role of surface chemical groups and pivotal photophysical sensing mechanisms. Subsequently, the core of the review critically evaluates recent advancements (particularly those from 2022 onward) in the use of functionalized CQDs for detecting food contaminants (such as heavy metals, pesticide residues, antibiotic residues, pathogens, and additives) and in food preservation techniques, including active packaging, antioxidative and antimicrobial coatings, and photodynamic inactivation. Through a systematic comparison of analytical figures of merit and the effects of various matrices across different design approaches, we delineate both the established capabilities and the current limitations of CQD-based technologies in realistic food systems. The review concludes by identifying ongoing challenges, specifically, batch-to-batch consistency, the long-term safety profile of CQDs in food-contact applications, and the translation gap from laboratory innovation to industrial practice, and outlines prospective research directions. The overarching aim of this work is to provide a structured framework for understanding how deliberate functional design can lead to improved performance, thereby guiding the rational development of next-generation CQD-based materials for ensuring food quality and public health. Full article

Antimicrobial resistance (AMR) is emerging as one of the most serious global health problems, necessitating the urgent development of alternative approaches to pathogen control. The present study describes the synthesis and characterization of a novel iodinated BODIPY derivative (BODIPY5), designed as a highly efficient photosensitizer for antimicrobial photodynamic inactivation (aPDI). The molecular design of the compound involves the introduction of two iodine atoms into the BODIPY5 core, which induces a “heavy atom effect”, accelerates the intersystem transition from the singlet to the triplet state, and leads to increased generation of singlet oxygen upon irradiation with visible light. Photophysical measurements show a significant fluorescence quenching of BODIPY5 compared to its unsubstituted counterpart, which is a direct indicator of increased photodynamic activity. The compound’s antimicrobial efficacy was tested in a homogeneous medium and after immobilization on cotton textiles via physical adsorption. In solution, BODIPY5 nearly eliminated the model bacterial strains B. cereus and P. aeruginosa at a low concentration of 10 µg/mL under light, with cell viability below 1%. The functionalized cotton fabric exhibits pronounced self-disinfection properties, retaining high photodynamic activity against the Gram-negative pathogen P. aeruginosa. Scanning electron microscopy results confirm extensive morphological damage and loss of structural integrity in bacterial cells on the treated textile following irradiation. The non-specific mechanism of action, which generates reactive oxygen species (¹O₂) in situ, prevents the development of bacterial resistance and makes the developed material a promising candidate for use in hospital environments, including antibacterial clothing and protective equipment. Full article

Antimicrobial blue light (aBL) within the visible violet–blue spectrum has emerged as a promising non-chemical strategy for microbial control, yet its performance across environmentally realistic matrices and surfaces remains insufficiently characterised. Here, we evaluate a continuous-exposure aBL LED system operating within the visible 407–421 nm range for its antimicrobial efficacy against Escherichia coli K-12 MG1655 and Bacillus cereus NCTC 11143 across liquid cultures, agar surfaces, and representative built-environment materials (glass and steel bar). Bacterial inactivation was quantified using culture-based enumeration and flow cytometric viability profiling. The system delivered a controlled irradiance of 0.72 mW/cm² at 58 cm, corresponding to cumulative doses of 2.59–62.23 J cm⁻² over 1–24 h of exposure. Significant, time-dependent reductions in viability were observed across all matrices relative to fluorescent-light controls, with near-complete or complete loss of recoverable cells on solid surfaces following prolonged exposure. Flow cytometric analyses revealed progressive transitions from viable to injured and dead cell populations, consistent with photodynamic inactivation mediated by endogenous photosensitiser activation and reactive oxygen species generation. These findings demonstrate that continuous visible-light aBL illumination can achieve effective multisurface microbial inactivation under moderate irradiance conditions compatible with occupied environments, supporting its translational potential as a sustainable, non-chemical decontamination strategy for healthcare, food-processing, and built environments. Full article

Background/Objectives: Multidrug-resistant (MDR) Enterobacter spp. are critical pathogens within the ESKAPE group, frequently exhibiting resistance to carbapenems. Antimicrobial photodynamic therapy (aPDT) represents a promising non-antibiotic strategy to circumvent these resistance mechanisms. This scoping review aims to map the current evidence regarding the efficacy of aPDT in inactivating Enterobacter spp., identifying the most effective photosensitizers (PS), light parameters, and existing research gaps. Methods: A systematic search was performed across PubMed, Scopus, and Google Scholar (2013–2025) following PRISMA-ScR guidelines and registered on OSF. Studies were included if they evaluated aPDT against Enterobacter spp. (in vitro or in vivo) and provided quantitative data on microbial reduction. Data was extracted using a standardized charting form covering bacterial strains, PS type, light source, and viability reduction. The results from the eligible sources of evidence were synthesized narratively to address the review objectives. Results: Despite the clinical priority of Enterobacter, only seven studies met the eligibility criteria. Methylene Blue remains the most frequently studied PS, achieving reductions of 3–8 log₁₀. Emerging evidence highlights the synergistic efficacy of monocationic chlorins and graphene-based nanomaterials in enhancing the bactericidal effect of light-based treatments. Notably, aPDT demonstrated the ability to inactivate carbapenemases, the bacterial enzymes responsible for carbapenem resistance. However, only two studies evaluated in vivo applications, primarily within dental settings. Conclusions: aPDT is a promising method against MDR Enterobacter spp. and bypasses traditional resistance mechanisms. However, the limited number of studies indicates a significant knowledge gap. Future research should focus on standardized in vivo protocols and the synergy between aPDT and conventional antibiotics to support clinical translation. Full article

The increasing prevalence of antimicrobial resistance, together with recurring infectious disease outbreaks, has intensified the need for alternative strategies to control microbial infections beyond conventional antibiotic therapies. Antimicrobial photodynamic therapy has emerged as a promising non-antibiotic approach in which light-activated photosensitising compounds generate reactive oxygen species that induce oxidative damage to microbial cells. Plant-derived photosensitisers have attracted increasing attention due to their structural diversity, biocompatibility, natural abundance, and potential for sustainability. Natural compounds such as curcumin, hypericin, chlorophyll derivatives, flavonoids, anthraquinones, and riboflavin exhibit favourable photochemical properties that enable efficient production of reactive oxygen species upon irradiation with visible light. Through radical- and singlet-oxygen-mediated photochemical pathways, these molecules exhibit broad-spectrum antimicrobial activity against bacteria, fungi, viruses, and biofilm-associated microorganisms. This review examines the photophysical properties and mechanisms of reactive oxygen species generation associated with plant-derived photosensitisers, together with key factors influencing their antimicrobial performance. Recent advances in nanocarrier-based delivery systems, dual-wavelength activation strategies, and synergistic combination therapies are also discussed for their potential to improve photostability, enhance reactive oxygen species generation, and increase microbial inactivation efficiency. Finally, current progress, challenges, and future research directions for advancing plant-derived photosensitisers in antimicrobial photodynamic therapy are discussed. Full article

Background: Oral biofilms are a major etiological factor in dental caries, periodontal disease, peri-implantitis, and endodontic infections. Increasing antimicrobial resistance and the limitations of conventional therapies have intensified interest in antimicrobial photodynamic therapy (aPDT). Hypericin, a natural photosensitizer derived from Hypericum perforatum, demonstrates potent reactive oxygen species generation and broad antimicrobial activity; however, its dental applications remain insufficiently synthesized. Objective: To systematically evaluate the antimicrobial efficacy, treatment parameters, safety, and clinical potential of hypericin-mediated aPDT against oral biofilms and infections in dentistry. Methods: This systematic review was conducted according to PRISMA 2020 and registered in PROSPERO CRD42024617727. Electronic searches of PubMed/MEDLINE, Embase, Scopus, and the Cochrane Library (January 2010 to December 2025) were performed. Studies assessing hypericin-mediated aPDT in oral or dental contexts were included. Methodological quality was evaluated using a predefined nine-domain risk-of-bias tool. Results: Eleven studies met the inclusion criteria. Hypericin-mediated aPDT demonstrated strong antimicrobial effects, achieving up to 99% planktonic inactivation and significant biofilm reduction across bacterial and fungal species. Activity was particularly pronounced against Gram-positive organisms, including Staphylococcus aureus and Enterococcus faecalis. However, efficacy against mature biofilms was variable and often dependent on formulation and irradiation parameters. Most studies showed moderate methodological quality, with frequent deficiencies in reporting light calibration and dosimetry. Advanced delivery systems, including liposomal and nanoparticle formulations, improved photodynamic performance. Conclusions: Hypericin-mediated aPDT shows promising antimicrobial activity against oral pathogens and biofilms, with favorable selectivity and safety profiles. Nevertheless, the evidence remains predominantly preclinical and heterogeneous. Standardized protocols and well-designed clinical trials are required before routine dental implementation can be recommended. Full article

Staphylococcus aureus is a major foodborne pathogen that poses persistent challenges to food safety. Antimicrobial photodynamic treatment (PDT) has emerged as a promising non-thermal antimicrobial strategy capable of effectively inactivating S. aureus, though accumulating evidence suggests that the bacteria may initiate adaptive responses to the PDT or even develop tolerance. However, the metabolic mechanisms underlying bacterial responses to PDT exposure, particularly under sub-lethal conditions, remain poorly understood. Thus, in the current study, untargeted metabolomics based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) and gas chromatography–mass spectrometry (GC–MS) were employed to characterize intracellular metabolic alterations in S. aureus following curcumin-mediated PDT (40 µM curcumin, 425 nm blue light at intensity of 0.198 J cm⁻²). The obtained results revealed a clear separation between the control and PDT-treated groups, indicating sub-lethal PDT induced pronounced metabolic perturbations while preserving partial cellular viability. A total of 97 significantly differential metabolites were identified, encompassing a range of key metabolites associated with amino acid biosynthesis, lipid metabolism, and nucleotide metabolism, indicating the PDT-induced metabolic alterations in pathways could be associated with stress adaptation, membrane integrity, and energy metabolism. Collectively, these findings demonstrate that PDT, even at sub-lethal doses, induces extensive metabolic dysregulation in S. aureus, which potentially represent critical bactericidal vulnerability points target by PDT, yet may paradoxically participate in adaptive metabolic responses that support bacterial survival under PDT exposure. Further investigations are therefore warranted to elucidate the relationships among PDT-induced metabolic perturbations, bacterial inactivation, and long-term phenotypic adaptation. Overall, this work may provide mechanistic insight into PDT-induced antimicrobial action and support further optimization of PDT as an effective non-thermal intervention for food safety and preservation. Full article

The global challenge of antimicrobial resistance (AMR) has been framed primarily in terms of genetic resistance mechanisms. Nevertheless, bacteria can also survive antimicrobial stress through phenotypic plasticity, resulting in transient, non-genetic states such as tolerance, persistence, and population-level resilience. These phenotypic states complicate diagnostic efforts, diminish antibiotic efficacy, and contribute to the chronic nature of infections even in the absence of heritable resistance. This review evaluates phenotypic plasticity as a significant yet underrecognized factor in AMR, with a focus on responses to oxidative and photodynamic stress. Key manifestations of plasticity are discussed, including morphological and metabolic remodeling such as filamentation, small-colony variants, and metabolic rewiring, as well as envelope- and biofilm-associated heterogeneity and regulatory flexibility mediated by gene networks and horizontal regulatory transfer. The review highlights plastic responses elicited by reactive oxygen species-mediated stress and antimicrobial photodynamic inactivation, where single-cell heterogeneity, biofilm and mucus barriers, and light-dependent cues influence bacterial survival. Case studies are presented to demonstrate how photodynamic strategies can induce transient protective states and act synergistically with antibiotics, revealing mechanisms of action that extend beyond conventional single-target therapeutic models. Drawing on evidence from single-cell analyses, biofilm ecology, and experimental evolution, this review establishes phenotypic plasticity as a central element in the chemical biology of AMR. Enhanced understanding of plasticity is essential for advancing diagnostics, informing the development of adjuvant therapies, and predicting bacterial responses to novel antimicrobial interventions. Full article

Cold atmospheric plasma (CAP) has emerged as a promising anticancer approach because of its ability to selectively eliminate malignant cells. Among the proposed mechanisms of this selectivity, the Bauer theory emphasizes the synergistic action of plasma-derived hydrogen peroxide (H₂O₂) and nitrite (NO₂⁻), leading to the transient generation of primary singlet oxygen (¹O₂). This early event inactivates membrane-bound catalase, allowing tumor cell-derived H₂O₂ and peroxynitrite to initiate a self-amplifying cycle that produces secondary ¹O₂, as a hallmark of CAP selectivity. To test this hypothesis, in this work, we monitored extracellular dissolved oxygen (DO) dynamics in HT-29 colorectal cancer cells treated with an argon plasma jet using time-resolved phosphorescence lifetime spectroscopy. Temporal variations in DO likely reflect the cumulative effect of rapid ¹O₂ production and its reactions with cells. A delayed surge in extracellular ¹O₂ was observed specifically in dying cancer cells within the 10–20 min window predicted by the model. Intracellular ROS imaging confirmed a strong correlation between intracellular ROS, extracellular ¹O₂ dynamics, and viability loss. Together, these results provide mechanistic validation of Bauer’s redox model and suggest that early oxygen dynamics after CAP exposure can serve as predictive markers for treatment efficacy in plasma or photodynamic therapies. Full article

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

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality that relies on the activation of photosensitizers (PS) by specific wavelengths of light to generate reactive oxygen species (ROS), resulting in localized cytotoxicity with relative sparing of healthy tissues. Depending on the PS properties, light dose, and intrinsic cellular features, PDT can elicit multiple cell death pathways, including apoptosis, necrosis, and autophagy. Increasing evidence indicates that PDT is also a potent inducer of ferroptosis, an iron-dependent form of regulated cell death driven by excessive lipid peroxidation (LPO), glutathione (GSH) depletion, and inactivation of glutathione peroxidase 4 (GPX4). PDT-derived ROS promote ferroptosis both indirectly by exhausting antioxidant defenses and directly by peroxidizing PUFAs within membrane phospholipids. At the same time, intense oxidative stress generated by PDT can activate adaptive responses such as mitophagy, a selective autophagic process that removes damaged mitochondria to limit ROS production and preserve redox homeostasis. Ferroptosis and mitophagy are therefore tightly interconnected, functioning as opposing yet complementary regulators of cell fate. PDT emerges as a key upstream modulator of the ferroptosis–mitophagy balance, as spatially and temporally confined oxidative stress can shift cellular responses from adaptive mitochondrial quality control to irreversible ferroptotic injury. Despite growing interest in both PDT and ferroptosis, their mechanistic interplay, particularly in relation to mitophagy, remains underexplored. This narrative review provides an integrated overview of current knowledge on how PDT influences ferroptosis and mitophagy, highlighting the molecular mechanisms that connect these pathways and discussing their implications for improving therapeutic efficacy and overcoming resistance. 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