Photodynamic Inactivation Of Bacteria Research Articles

Photodynamic inactivation of bacteria: Why it is not enough to excite a photosensitizer

BackgroundThe development of multidrug resistance (MDR) in infectious agents is one of the most serious global problems facing humanity. Antimicrobial photodynamic therapy (APDT) shows encouraging results in the fight against MDR pathogens, including those in biofilms. MethodsPhotosensitizers (PS), monocationic methylene blue, polycationic and polyanionic derivatives of phthalocyanines, electroneutral and polycationic derivatives of bacteriochlorin were used to study photodynamic inactivation of Gram-positive and Gram-negative planktonic bacteria and biofilms under LED irradiation. Zeta potential measurements, confocal fluorescence imaging, and coarse-grained modeling were used to evaluate the interactions of PS with bacteria. PS aggregation and photobleaching were studied using absorption and fluorescence spectroscopy. ResultsThe main approaches to ensure high efficiency of bacteria photosensitization are analyzed. ConclusionsPS must maintain a delicate balance between binding to exocellular and external structures of bacterial cells and penetration through the cell wall so as not to get stuck on the way to photooxidation-sensitive structures of the bacterial cell.

Porphyrin-based covalent organic polymers with customizable photoresponses for photodynamic inactivation of bacteria

Porphyrin-linked covalent organic polymers (COPs) provide a reliable photocatalytic platform, while photodynamic inactivation (PDI) induced by reliable porphyrin-based COPs is considered to be an effective method to resist microbial contamination. Herein, three tunable porphyrin-based covalent organic polymers (H2-Por-COPs, OH-Por-COPs, and Zn-Por-COPs) are designed and employed for the PDI of Staphylococcus aureus and Escherichia coli under visible light illumination. Interestingly, singlet oxygen (1O2) generation by the Por-COPs can be manipulated via intramolecular regulation with the order Zn-Por-COP > OH-Por-COP > H2-Por-COP. With rationally tune, the Zn-Por-COP demonstrated remarkable antibacterial activity against Staphylococcus aureus (kill percentage 99.65 % ± 0.24 %) and Escherichia coli (kill percentage 97.25 % ± 1.78 %) in only 15 min under visible-light irradiation. Density functional theory (DFT) calculations and photophysical tests showed that the presence of electron-donating -OH groups on the aromatic linkers and Zn2+ ions in porphyrin units narrowed the HOMO-LUMO gap, enhancing both light absorption, intersystem crossing (ISC) and 1O2 generation for more efficient bacteria inactivation. This work can be applied to efficiently screen suitable photosensitizers and provides a rational regulatory strategy for PDI of pathogenic bacteria.

Cotton fabrics modified with molybdenum nanoclusters for photodynamic inactivation of bacteria and viruses

Design of self-sterilizing materials for protecting surfaces from pathogenic microorganisms is of profound interest in the medical community. In this study, we have prepared textile materials composed of cotton fabrics and octahedral molybdenum cluster complex, [{Mo6I8}(DMSO)6](NO3)4 (DMSO – dimethyl sulfoxide), with photoactivated antibacterial, antifungal, and antiviral properties. These uniformly colored fabrics were prepared via the impregnation of cotton fabrics with solution of dissolved cluster complex. Strong bonding of cluster molecules to cotton provided high stability of the materials with negligible washing out during the washing with a laundry detergent. The obtained fabrics produced singlet oxygen at the surface upon light irradiation, and the production persisted after repeated irradiation cycles. The fabrics showed photoinduced antipathogenic activity against Gram-positive and Gram-negative bacteria, fungi, COVID-19 (SARS-CoV-2), and influenza B viruses.

Hydrogen peroxide as an additive to curcumin on the photodynamic inactivation of bacteria: a preliminary study

Photodynamic inactivation (PDI) of microorganisms has been shown as a promising alternative against the spread of resistant bacteria. It has been used not only in clinical applications, but also in the public health sector, for water and wastewater disinfection. In order to improve efficiency, recent research has focused on novel photosensitizing materials, as well as chemical additives. To our knowledge, however, hydrogen peroxide (a widely known standalone disinfectant) has not been employed combined with curcumin (a vegetal-based and environmental-friendly photosensitizer) for PDI seeking for future environmental applications. In this sense, this study aimed to assess whether there were any competitive or cooperative effects by the simultaneous use of curcumin and hydrogen peroxide on the PDI of Staphylococcus aureus, in in-vitro batch tests. Photobleaching for individual and combined factors was performed in order to compare results of inactivation with changes in chemical aspects in solution under blue light irradiation. One may think that the combination may add strength to PDI due to hydrogen peroxide being a natural supplier of oxygen. However, antagonistic effects were found in combined treatments, implying that such combination is non profitable. The results indicate that special care is necessary when considering combining techniques.

An AIE-active bacterial inhibitor and photosensitizer for selective imaging, killing, and photodynamic inactivation of bacteria over mammalian cells.

Photodynamic therapy is becoming increasingly popular for combat of bacteria. In the clinical photodynamic combat of bacteria, one critical issue is to avoid the potential damage to the host since the reactive oxygen species produced by photosensitizers are also harmful to mammalian cells. In this work, we report an aggregation-induced-emission-active bacterial inhibitor and photosensitizer, OEO-TPE-MEM (OTM), for the imaging, killing, and light-enhanced inactivation of bacteria. OTM could efficiently bind to and kill Gram-positive bacteria, while its affinity to Gram-negative bacteria is lower, and a higher OTM concentration is required for killing Gram-negative bacteria. OTM is also an efficient photosensitizer and could efficiently sensitize the production of reactive oxygen species, which enhances its killing effect on both Gram-positive and Gram-negative bacteria. More interestingly, OTM is very biocompatible with normal mammalian cells both in the dark and under light irradiation. OTM in mice models with bacteria-infected wounds could promote the healing of infected wounds without affecting their organs and blood parameters, which makes it an excellent candidate for clinical applications.

Photosensitiser-incorporated microparticles for photodynamic inactivation of bacteria.

Antimicrobial resistance is an ever-growing global concern, making the development of alternative antimicrobial agents and techniques an urgent priority to protect public health. Antimicrobial photodynamic therapy (aPDT) is one such promising alternative, which harnesses the cytotoxic action of reactive oxygen species (ROS) generated upon irradiation of photosensitisers (PSs) with visible light to destroy microorganisms. In this study we report a convenient and facile method to produce highly photoactive antimicrobial microparticles, exhibiting minimal PS leaching, and examine the effect of particle size on antimicrobial activity. A ball milling technique produced a range of sizes of anionic p(HEMA-co-MAA) microparticles, providing large surface areas available for electrostatic attachment of the cationic PS, Toluidine Blue O (TBO). The TBO-incorporated microparticles showed a size-dependent effect on antimicrobial activity, with a decrease in microparticle size resulting in an increase in the bacterial reductions achieved when irradiated with red light. The >6 log10Pseudomonas aeruginosa and Staphylococcus aureus reductions (>99.9999%) achieved within 30 and 60min, respectively, by TBO-incorporated >90μm microparticles were attributed to the cytotoxic action of the ROS generated by TBO molecules bound to the microparticles, with no PS leaching from these particles detected over this timeframe. TBO-incorporated microparticles capable of significantly reducing the bioburden of solutions with short durations of low intensity red light irradiation and minimal leaching present an attractive platform for various antimicrobial applications.

Breaking the Photostability and pH Limitation of Halo-Fluoresceins through Chitosan Conjugation.

Halo-fluoresceins are widely used in cell and tissue staining, intracellular sensing, and photodynamic therapy, but their notorious photo-instability and pH dependence restrict their applications, especially in long-term visible light exposure and acidic environments. To overcome these limitations, here a strategy is proposed of conjugating chitosan with the carboxyl group of halo-fluorescein (CS-halofluorescein). The cross-linked polymer chains and the hydrogen-bonding networks of chitosan help shielding out 1 O2 from direct attacking the encapsulated halo-fluoresceins, leading to atwo orders of magnitude lower photobleaching rate. Meanwhile, the condensation of primary amines of chitosan with the carboxyl group on halo-fluorescein blocks the pH-dependent intramolecular spirocyclization, leading to pH-inert fluorescein derivatives. The greatly improved photostability and pH inertness of CS-halofluoresceins can be harvested for aerobic photoredox synthesis and photodynamic bacteria inactivation in extremely acidic media. Moreover, food additive nature of chitosan and erythrosine (TIF) and excellent film-forming property of chitosan allow coating-based light-assisted preservation of perishable fruits, leading to appreciably extended shelf life of fruits (e.g., perishable strawberry, rt: > 3 days; 4°C: > 5 days).

Rose bengal-decorated rice husk-derived silica nanoparticles enhanced singlet oxygen generation for antimicrobial photodynamic inactivation.

The online version contains supplementary material available at 10.1007/s10853-023-08194-z.

Photodynamic Inactivation of Bacteria and Biofilms with Benzoselenadiazole-Doped Metal-Organic Frameworks.

Bacterial biofilms are difficult to treat due to their resistance to traditional antibiotics. Although photodynamic therapy (PDT) has made significant progress in biomedical applications, most photosensitizers have poor water solubility and can thus aggregate in hydrophilic environments, leading to the quenching of photosensitizing activity in PDT. Herein, a benzoselenadiazole-containing ligand was designed and synthesized to construct the zirconium (IV)-based benzoselenadiazole-doped metal-organic framework (Se-MOF). Characterizations revealed that Se-MOF is a type of UiO-68 topological framework with regular crystallinity and high porosity. Compared to the MOF without benzoselenadiazole, Se-MOF exhibited a higher 1O2 generation efficacy and could effectively kill Staphylococcus aureus bacteria under visible-light irradiation. Importantly, in vitro biofilm experiments confirmed that Se-MOF could efficiently inhibit the formation of bacteria biofilms upon visible-light exposure. This study provides a promising strategy for developing MOF-based PDT agents, facilitating their transformation into clinical photodynamic antibacterial applications.

Phytochemicals-based edible coating for photodynamic preservation of fresh-cut apples

Nature-derived chemicals have recently gained increased attention to settle down the challenges in the food industry. Quercetin has long been used as a natural medicine but its photoactivity has been neglected. In this work, by combining photodynamic bacteria inactivation (PDI) with an edible coating (Pectin/Quercetin) derived from FDA-approved chemicals, extend shelf-life and protected commercial quality of fresh-cut apples were achieved. Firstly, the potential photoactivated antibacterial performance of Quercetin (a natural plant flavonoid) was clarified with the treatment of a simulated sunlight lamp, realizing antibacterial efficacy of 100 % towards S. aureus (50 min) and L. monocytogenes (80 min) with light treatment. To develop safe and effective preservation of fresh-cut apples, Pectin/Quercetin edible coatings with 100 μmol/L quercetin were adopted. The results showed that the prepared edible coatings form a protective barrier over the surface of apples, effectively resisting bacterial infection and extending shelf life to 10 days while maintaining good commercial quality (including preferable color, keeping 100 % hardness, 80 % sugar content and 17.3 % weightlessness rate). Therefore, the prepared light-driven Pectin/Quercetin in this work has the potential to develop as fresh-cut fruit preservation technology.

Antimicrobial curcumin-mediated photodynamic inactivation of bacteria in natural bovine casing

Background: Outbreaks related to food contamination by resistant microorganisms is a worldwide concern that, motivates industries and research institutions to search for affordable solutions. Among the solutions that have been proposed, Photodynamic Inactivation (PDI) of microorganisms has gained prominence, among other aspects, because it is easy to apply and does not generate microbial resistance.Methods: In this study, we used the association between curcumin solubilized with Tween and light in the photodynamic inactivation process, using light-emitting diodes with a wavelength of 430 nm for decontamination S. Typhimurium and K. pneumoniae from bovine casings used as wrappers for meat products. The result was verified by counting and comparing the number of colony-forming units of the treatment concerning the negative control.Results: The solubilizer, Tween 80, used does not change the optical absorption of curcumin. An optical fluence of 150J/cm2 induces a microbial log reduction of 3.8±0.2 and 2.7±0.1 for S. Typhimurium, and K. pneumoniae contaminated guts, respectively. For the 200μM concentration of curcumin, the PDI provided a microbial log reduction of 3.16±0.03 for S. Typhimurium. For K. pneumoniae, the minimal inhibitory concentration of curcumin occurs up to 12.5μM, causing an microbial log reduction of 2.08±0.03.Conclusion: Both curcumin and tween are already used as additives in food production and do not pose health risks at the concentrations used. Furthermore, in the case of the material studied, the addition of curcumin favors the organoleptic quality associated with the color of the food, unlike the green or blue photossensitizers. The results pave the way for possible application of curcumin in finished meat products.

Photodynamic Inactivation of Bacteria in Ionic Environments Using the Photosensitizer SAPYR and the Chelator Citrate†.

Many studies show that photodynamic inactivation (PDI) is a powerful tool for the fight against pathogenic, multiresistant bacteria and the closing of hygiene gaps. However, PDI studies have been frequently performed under standardized invitro conditions comprising artificial laboratory settings. Under real-life conditions, however, PDI encounters substances like ions, proteins, amino acids and fatty acids, potentially hampering the efficacy of PDI to an unpredictable extent. Thus, we investigated PDI with the phenalene-1-one-based photosensitizer SAPYR against Escherichia coli and Staphylococcus aureus in the presence of calcium or magnesium ions, which are ubiquitous in potential fields of PDI applications like in tap water or on tissue surfaces. The addition of citrate should elucidate the potential as a chelator. The results indicate that PDI is clearly affected by such ubiquitous ions depending on its concentration and the type of bacteria. The application of citrate enhanced PDI, especially for Gram-negative bacteria at certain ionic concentrations (e.g. CaCl2 or MgCl2 : 7.5 to 75 mmol L-1 ). Citrate also improved PDI efficacy in tap water (especially for Gram-negative bacteria) and synthetic sweat solution (especially for Gram-positive bacteria). In conclusion, the use of chelating agents like citrate may facilitate the application of PDI under real-life conditions.

Lung surfactant negatively affects the photodynamic inactivation of bacteria—in vitro and molecular dynamic simulation analyses

In the context of the rapid increase of antibiotic-resistant infections, in particular of pneumonia, antimicrobial photodynamic therapy (aPDT), the microbiological application of photodynamic therapy (PDT), comes in as a promising treatment alternative since the induced damage and resultant death are not dependent on a specific biomolecule or cellular pathway. The applicability of aPDT using the photosensitizer indocyanine green with infrared light has been successfully demonstrated for different bacterial agents invitro, and the combination of pulmonary delivery using nebulization and external light activation has been shown to be feasible. However, there has been little progress in obtaining sufficient invivo efficacy results. This study reports the lung surfactant as a significant suppressor of aPDT in the lungs. In vitro, the clinical surfactant Survanta® reduced the aPDT effect of indocyanine green, Photodithazine®, bacteriochlorin-trizma, and protoporphyrin IX against Streptococcus pneumoniae. The absorbance and fluorescence spectra, as well as the photobleaching profile, suggested that the decrease in efficacy is not a result of singlet oxygen quenching, while a molecular dynamics simulation showed an affinity for the polar head groups of the surfactant phospholipids that likely impacts uptake of the photosensitizers by the bacteria. Methylene blue is the exception, likely because its high water solubility confers a higher mobility when interacting with the surfactant layer. We propose that the interaction between lung surfactant and photosensitizer must be taken into account when developing pulmonary aPDT protocols.

Photonic Crystal-Enhanced Photodynamic Antibacterial Therapy

Photonic Crystal-Enhanced Photodynamic Antibacterial Therapy

Rose bengal-integrated electrospun polyacrylonitrile nanofibers for photodynamic inactivation of bacteria

Rose bengal-integrated electrospun PAN nanofibers displayed high antimicrobial efficacy against both Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria under white light irradiation. This methodology offers a feasible strategy for water disinfection.

Design of a Metallacycle‐Based Supramolecular Photosensitizer for In Vivo Image‐Guided Photodynamic Inactivation of Bacteria

AbstractBacterial infection is one of the greatest threats to public health. In vivo real‐time monitoring and effective treatment of infected sites through non‐invasive techniques, remain a challenge. Herein, we designed a PtII metallacycle‐based supramolecular photosensitizer through the host‐guest interaction between a pillar[5]arene‐modified metallacycle and 1‐butyl‐4‐[4‐(diphenylamino)styryl]pyridinium. Leveraging the aggregation‐induced emission supramolecular photosensitizer, we improved fluorescence performance and antimicrobial photodynamic inactivation. In vivo studies revealed that it displayed precise fluorescence tracking of S. aureus‐infected sites, and in situ performed image‐guided efficient PDI of S. aureus without noticeable side effects. These results demonstrated that metallacycle combined with host‐guest chemistry could provide a paradigm for the development of powerful photosensitizers for biomedicine.

Design of a Metallacycle-Based Supramolecular Photosensitizer for In Vivo Image-Guided Photodynamic Inactivation of Bacteria.

Bacterial infection is one of the greatest threats to public health. In vivo real-time monitoring and effective treatment of infected sites through non-invasive techniques, remain a challenge. Herein, we designed a PtII metallacycle-based supramolecular photosensitizer through the host-guest interaction between a pillar[5]arene-modified metallacycle and 1-butyl-4-[4-(diphenylamino)styryl]pyridinium. Leveraging the aggregation-induced emission supramolecular photosensitizer, we improved fluorescence performance and antimicrobial photodynamic inactivation. In vivo studies revealed that it displayed precise fluorescence tracking of S. aureus-infected sites, and in situ performed image-guided efficient PDI of S. aureus without noticeable side effects. These results demonstrated that metallacycle combined with host-guest chemistry could provide a paradigm for the development of powerful photosensitizers for biomedicine.

Fluorescence Imaging and Photodynamic Inactivation of Bacteria Based on Cationic Cyclometalated Iridium(III) Complexes with Aggregation-Induced Emission Properties.

Antibacterial photodynamic therapy (PDT) is one of the emerging methods for curbing multidrug-resistant bacterial infections. Effective fluorescent photosensitizers with dual functions of bacteria imaging and PDT applications are highly desirable. In this study, three cationic and heteroleptic cyclometalated Ir(III) complexes with the formula of [Ir(CˆN)2 (NˆN)][PF6 ] are prepared and characterized. These Ir(III) complexes named Ir(ppy)2 bP, Ir(1-pq)2 bP, and Ir(2-pq)2 bP are comprised of three CˆN ligands (i.e., 2-phenylpyridine (ppy), 1-phenylisoquinoline (1-pq), and 2-phenylquinoline (2-pq)) and one NˆN bidentate co-ligand (bP). The photophysical characterizations demonstrate that these Ir(III) complexes are red-emitting, aggregation-induced emission active luminogens. The substitution of phenylpyridine with phenylquinoline isomers in the molecules greatly enhances their UV and visible-light absorbance as well as the photoinduced reactive oxygen species (ROS) generation ability. All three Ir(III) complexes can stain both Gram-positive and Gram-negative bacteria efficiently. Interestingly, even though Ir(1-pq)2 bP and Ir(2-pq)2 bP are constitutional isomers with very similar structures and similar ROS generation ability in buffer, the former eradicates bacteria much more effectively than the other through white light-irradiated photodynamic inactivation. This work will provide valuable information on the rational design of Ir(III) complexes for fluorescence imaging and efficient photodynamic inactivation of bacteria.

Carbon Dots as an Emergent Class of Antimicrobial Agents.

Antimicrobial resistance is a recognized global challenge. Tools for bacterial detection can combat antimicrobial resistance by facilitating evidence-based antibiotic prescribing, thus avoiding their overprescription, which contributes to the spread of resistance. Unfortunately, traditional culture-based identification methods take at least a day, while emerging alternatives are limited by high cost and a requirement for skilled operators. Moreover, photodynamic inactivation of bacteria promoted by photosensitisers could be considered as one of the most promising strategies in the fight against multidrug resistance pathogens. In this context, carbon dots (CDs) have been identified as a promising class of photosensitiser nanomaterials for the specific detection and inactivation of different bacterial species. CDs possess exceptional and tuneable chemical and photoelectric properties that make them excellent candidates for antibacterial theranostic applications, such as great chemical stability, high water solubility, low toxicity and excellent biocompatibility. In this review, we will summarize the most recent advances on the use of CDs as antimicrobial agents, including the most commonly used methodologies for CD and CD/composites syntheses and their antibacterial properties in both in vitro and in vivo models developed in the last 3 years.

Vitamin K5 Is an Efficient Photosensitizer for Ultraviolet a Light Inactivation of Bacteria

Photodynamic inactivation of bacteria has been proven as an effective method to inactivate pathogenic bacteria. This study identified vitamin K5 (VK5) as an efficient photosensitizer for ultraviolet light A (UVA) induced bacterial inactivation.Six species of bacteria, including Bacillus cereus (vegetative form), Escherichia coli , Pseudomonas aeruginosa, Staphylococcus aureus , Staphylococcus epidermidis , Klebsiella pneumoniae , and two species of antibiotic-resistant bacteria, Pseudomonas aeruginosa and Staphylococcus aureus, were grown and mixed with VK5 and irradiated with UVA in phosphate buffered saline (PBS) in 6-well plates following our previous procedures (Xu & Vostal, 2014). A representative figure of bacterial reduction of VK5 and UVA irradiation treated E. coli , as determined by a colony forming unit (CFU) count, is shown in Figure 1. Increasing concentrations of VK5 from 0 to 1600 µmol l-1 with fixed UVA irradiation doses produce a concentration-depended reduction of bacteria. Similarly, a UVA dose response for bacterial reduction is evident with fixed VK5 concentrations. As shown in Table 1, UVA irradiation (5.8 J cm-2) with vitamin K5 (1600 µmol l-1) reduced the CFU of bacteria by three to seven logs. Antibiotic resistant bacteria (Pseudomonas A. and Staphylococcus A ) did not exhibit resistance to the bactericidal effects of UVA and vitamin K5 combination treatment.Efficacy of VK5 and UVA for bacterial reduction was also evident in plasma although higher concentrations of VK5 and UVA doses were required. VK5 (500 or 2000 µ mol l-1 ) in 35% or 50% bacteria spiked plasma diluted with Platelet Additive Solutions was exposed to UVA irradiation at 6 and 30 J cm-2. This treatment reduced Escherichia coli and Staphylococcus aureus CFU by up to seven logs as shown in Figures 2a and 2b, respectively.Reactive oxygen species, hydroxyl radicals (˙OH) and superoxide anion radicals (O2˙−), were found generated in vitamin K5 aqueous solution after UVA irradiation, suggesting these oxygen species may mediate the inactivation of the bacteria. The O2˙−was generated in UVA-irradiated-VK5 PBS solution. At a fixed UVA dose of 2.9 J cm-2, the generation of O2˙− coincided with an increase in VK5 concentration from 0 to 1000 µ mol l-1 (Figure 3a). The generation of O2˙− was further confirmed by carrying out quenching study with superoxide dismutase (SOD) as specific quenchers. The production of O2˙− was reduced as the SOD concentration was increased from 0 to 640 units ml-1 in a 500 µ mol l-1 VK5 solution irradiated with a UVA (2.9 J cm-2 ) (Figure 3b). VK5 and UVA light combination also caused the release of ˙OH as the VK5 concentrations increased from 0 to 1000 µ mol l-1 with a fixed UVA dose of 2.9 J cm-2 The generation of ˙OH was further confirmed by mannitol, a specific quencher for ˙OH. Less ˙OH was produced when mannitol concentration was increased from 0 to 1 mol l-1, in the presence of a fixed VK5 concentration of 500 µ mol l-1 and a UVA dose of 2.9 J cm-2.Vitamin K5 and UVA light treatment is an effective method for reduction of bacteria in solutions including plasma and may be an effective way to reduce transfusion transmitted septic reactions from contaminated plasma products. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.