Antimicrobial activity of cationic water-soluble porphyrin against multidrug-resistant bacteria in biofilms and canine skin samples.

Multidrug-resistant (MDR) microorganisms pose a threat to animal health, particularly in integumentary diseases, which can be caused by multiple organisms and often manifest as biofilms, hindering treatment effectiveness. We evaluated the antimicrobial activity of antimicrobial photodynamic therapy (aPDT) using a water-soluble tetra-cationic porphyrin (4-H2TMeP) against MDR bacteria cultured in biofilm and in mono and polyculture grown on canine skin samples. We utilized 4-H2TMeP porphyrin against MDR Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus pseudintermedius. A non-cytotoxic concentration of 4-H2TMeP (40 µM), previously shown to be effective in vitro against these bacteria cultured in solution, was employed. Biofilms were treated with 4-H2TMeP and subjected to light irradiation for 30, 60, and 90 min. Monocultures on canine skin samples were treated with 4-H2TMeP and irradiated for 30 (S. pseudintermedius), 60 (E. coli), or 60 and 90 min (P. aeruginosa). Polycultures of S. pseudintermedius and E. coli were treated with light for 60 and 90 min. The efficacy of aPDT was evaluated by plating light-exposed biofilms, mono and polycultures of bacteria obtained from skin samples exposed to light and kept in the dark. Colony-forming units were counted after 24 h of incubation at 37 °C. aPDT using 4-H2TMeP reduced bacterial concentrations of S. pseudintermedius and E. coli biofilms. Additionally, it significantly reduced bacterial concentrations cultivated on skin samples, with a particular emphasis on S. pseudintermedius. These findings indicate that aPDT with 4-H2TMeP is a promising alternative treatment against MDR bacteria in animal skin infections and should be further explored through in vivo research.

In vitro antimicrobial, antibiofilm photodynamic activity, and molecular dynamic simulations of tetra-cationic porphyrinmembrane interactions against foodborne microorganisms.

This manuscript presents a new report on the in vitro antimicrobial photo-inactivation of foodborne microorganisms (Salmonella spp. and Listeria monocytogenes) using tetra-cationic porphyrins. Isomeric tetra-cationic porphyrins (3MeTPyP, 4MeTPyP, 3PtTPyP, and 4PtTPyP) were tested, and antimicrobial activity assays were performed at specific photosensitizer concentrations under dark and white-light LED irradiation conditions. Among the tested bacterial strains, 4MeTPyP exhibited the highest efficiency, inhibiting bacterial growth within just 60 min at low concentrations (17.5 µM). The minimal inhibitory concentration of 4MeTPyP increased when reactive oxygen species scavengers were present, indicating the significant involvement of singlet oxygen species in the photooxidation mechanism. Furthermore, the checkerboard assay testing the association of 4MeTPyP showed an indifferent effect. Atomic force microscopy analyses and dynamic simulations were conducted to enhance our understanding of the interaction between this porphyrin and the strain's membrane.

Antibiofilm action using water-soluble tetra-cationic porphyrin and antibacterial photodynamic therapy against Moraxella spp. from cattle.

Infectious bovine keratoconjunctivitis (IBK) is the most important eye disease in ruminants worldwide. Moraxella bovis and Moraxella bovoculi can form biofilm and are frequently isolated from affected animals. Antimicrobials are used worldwide to treat clinical cases of IBK, although they have limited success in clearing the infection. Therefore, photodynamic therapy using porphyrins as photosensitizing molecules is an alternative method to eliminate microorganisms, including biofilms. We evaluated the antibacterial activity of a zinc(II) metalloporphyrin (ZnTMeP) against M. bovis and M. bovoculi biofilms since this compound can efficiently inactivate planktonic Moraxella spp. This study was carried out with two reference strains of Moraxella spp. (M. bovis: ATCC® 10900 and M. bovoculli: ATCC® BAA1259). The antibacterial activity of 4.0 µM of the ZnTMeP porphyrin was evaluated on forming and consolidate biofilms with three 30-min cycles of white-light exposure for three days. The ZnTMeP porphyrin reduced M. bovis and M. bovoculi biofilm formation. In addition, ZnTMeP partially destroyed consolidated M. bovoculi biofilms in the second white-light irradiation cycle, although the porphyrin had no effect against the consolidated biofilm of M. bovis. Despite the biofilm still not being completely inactivated, our findings are promising and encourage further experiments using the phototherapy protocol.

The first evidence of antibiofilm action of Proteus mirabilis with tetra-cationic porphyrins containing cisplatin by antimicrobial photodynamic therapy.

Biofilms are responsible for up to 80% of antimicrobial-resistant nosocomial infections. Most of these infections are associated with medical devices such as urinary catheters, and in this context, it is estimated that 90-100% of patients who undergo long-term catheterization develop infections. Proteus mirabilis, the most prevalent microorganism, is responsible for 20-45% of these infections. Thus, this study aimed to evaluate, for the first time, the antimicrobial and antibiofilm effects of cationic porphyrins on P. mirabilis. Neutral porphyrins 3-H2TPyP and 4-H2TpyP and tetra-cationic derivatives 3-cis-PtTPyP and 4-cis-PtTPyP were evaluated in broth microdilution tests to determine the minimum inhibitory and bactericidal concentrations. Time-kill curves, checkerboard test, reactive oxygen species (ROS) scavenger assays, conventional biofilm formation, and biofilm assay with catheters were also performed. The microdilution tests showed greater efficacy against P. mirabilis when 3-cis-PtTPyP was exposed to white-light conditions; this also occurred when the microbial time-kill curve was performed at 0, 2, 6, and 12 h. The radical superoxide species was possibly responsible for photoinactivation in the ROS scavenger assays. In biofilm assays (conventional and catheter), 3-cis-PtTPyP obtained better results when irradiated with a white-light source. In the checkerboard assay, the same compound showed no differences when tested in association with ciprofloxacin hydrochloride. Our findings lead us to conclude that antimicrobial photodynamic therapy and cationic porphyrins obtained positive results and are promising alternatives to treat P. mirabilis biofilms.

DNA-Interactive and Damage Study with meso-Tetra(2-thienyl)porphyrins Coordinated with Polypyridyl Pd(II) and Pt(II) Complexes.

We report the DNA-binding properties of three porphyrins with peripheral thienyl substituents (TThPor, PdTThPor and PtTThPor). The binding capacity of each porphyrin with DNA was determined by UV-Vis and steady-state fluorescence emission spectroscopy combined with molecular docking calculations. The results suggest that the interaction of these compounds probably occurs via secondary interactions via external grooves (minor grooves) around the DNA macromolecule. Moreover, porphyrins containing peripheral Pd(II) or Pt(II) complexes (PdTThPor and PtTThPor) were able to promote photo-damage in the DNA.

Charge effect of water-soluble porphyrin derivatives as a prototype to fight infections caused by Acinetobacter baumannii by aPDT approaches.

In the last decade, Acinetobacter baumannii has emerged as a pathogen associated with infections in intensive care units worldwide, especially due to its ability to resist an extensive list of antibiotics. In this context, porphyrins have emerged as an important strategy in photodynamic therapy, since they are a group of tetrapyrrolic compounds with important photochemical and photobiological activities. In this study, the antimicrobial photodynamic activity of meso-tetra(4-N-methyl-pyridyl)porphyrin (H2TMePyP+) and meso-tetra(4-sulfonatophenyl)porphyrin (H2TPPS‒) was evaluated against A. baumannii by minimum inhibitory concentration (MIC), anti-biofilm activity, and the interaction with antibiotics after exposure to white-light LED irradiation. The cationic derivative H2TMePyP+ was more potent (MIC = 0.61 µM) than H2TPPS‒, with anti-biofilm activity and increased the antimicrobial activity of ciprofloxacin and amikacin. Given these findings, the tetra-cationic porphyrins can be assumed as prototypes to optimize and develop new agents by promoting oxidative stress and inducing free radical production.

Peripheral tetra-cationic Pt(II) porphyrins photo-inactivating rapidly growing mycobacteria: First application in mycobacteriology.

In this manuscript, we report, for the first time, the photoinactivation evaluation of tetra-cationic porphyrins with peripheral Pt (II)-bpy complexes in the photodynamic inactivation (PDI) of rapidly growing mycobacterial strains (RGM). Two different isomeric Pt (II)-porphyrins were synthetized and applied. PDI experiments in the strains of Mycobacteroides abscessus subsp. Abscessus (ATCC 19977), Mycolicibacterium fortuitum (ATCC 6841), Mycobacteroides abscessus subsp. Massiliense (ATCC 48898), and Mycolicibacterium smegmatis (ATCC 700084) conducted with adequate concentration (without aggregation) of photosensitizers (PS) under white-light illumination for 90 min showed that the most effective PS significantly reduced the concentration of viable mycobacteria. The present results show that positively charged porphyrins at the meta position (3-PtTPyP) are more efficient PS against M. abscessus, M. fortuitum, M. massiliense, and M. smegmatis. The effectiveness of the molecule as PS for PDI studies is also clear with mycobacteria, which is strongly related with the porphyrin peripheral charge and coordination platinum (II) compounds and consequently their solubility in physiological media. Tetra-cationic PS may be promising anti-mycobacterial PDI agents with potential applications in medical clinical cases and bioremediation.

Metal center ion effects on photoinactivating rapidly growing mycobacteria using water-soluble tetra-cationic porphyrins.

Rapidly growing mycobacteria (RGM) are pathogens that belong to the mycobacteriaceae family and responsible for causing mycobacterioses, which are infections of opportunistic nature and with increasing incidence rates in the world population. This work evaluated the use of six water-soluble cationic porphyrins as photosensitizers for the antimicrobial photodynamic therapy (aPDT) of four RGM strains: Mycolicibacterium fortuitum, Mycolicibacterium smeagmatis, Mycobacteroides abscessus subs. Abscessus, and Mycobacteroides abscessus subsp. massiliense. Experiments were conducted with an adequate concentration of photosensitizer under white-light irradiation conditions over 90 min and the results showed that porphyrins 1 and 2 (M = 2H or ZnII ion) were the most effective and significantly reduced the concentration of viable mycobacteria. The present work shows the result is dependent on the metal-center ion coordinated in the cationic porphyrin core. Moreover, we showed by atomic force microscopy (AFM) the possible membrane photodamage caused by reactive oxygen species and analyzed the morphology and adhesive force properties. Tetra-positively charged and water-soluble metalloporphyrins may be promising antimycobacterial aPDT agents with potential applications in medical clinical cases and bioremediation.

Antimicrobial activity and safety applications of meso-tetra(4-pyridyl)platinum(II) porphyrin.

Tetra-platinated(II) porphyrin hexafluorophosphate compound (4-PtTPyPor) was synthetized and along 5,10,15,20-tetrakis(4-pyridyl)porphyrin (4-TPyPor), evaluated about the antimicrobial activity and safety. The effect was evaluated with and without light exposition. The antimicrobial activity was analyzed by microdilution and growth curve method. The assays showed an increase of antimicrobial potential caused by porphyrins with light exposition comparing the treatment without light irradiation. The biocompatibility was tested by MTT, ROS production, dsDNA on culture medium and hemolysis. All platinum porphyrin concentrations showed hemolytic activity under light exposition. The ROS measurement doesn't showed statistic difference between treatments and control. The picogreen assay demonstrates a reduction of dsDNA on culture medium with cells treated with porphyrins under light irradiation. The study demonstrated that the platinated porphyrins might be promising microbial photodynamic inactivation with potential applications in wastewater treatment, biofilm control and bioremediation.

Mono and dinuclear platinum and palladium complexes containing adamantane-azole ligands: DNA and BSA interaction and cytotoxicity.

Synthesis of dinuclear oxadiazole-adamantane platinum(II) and palladium(II) complexes (PtO, PdO) and mononuclear thiazolidine derivative complexes (PtT, PdT) was described. Characterization was performed by elemental analysis, infrared, UV-visible, 1H, 13C, 195Pt NMR spectra, MS spectroscopy and single crystal X-ray diffraction. The cytotoxicity by MTT assay against tumor and normal cell lines with or without extracellular GSH was also investigated. In general, mononuclear complexes containing thiazolidine-adamantane ligands were more cytotoxic than oxadiazole-adamantane derivatives. PtT complex proved to be as active as cisplatin. Dinuclear compounds were considered inactive to cells in evaluated conditions, due to their high stability with ligands in a chelated and bridged way. Results suggest that GSH cannot be considered a target. DNA- and BSA-binding interactions were evaluated using UV-visible and fluorescence spectroscopy, intercalating dyes and molecular docking. Upon coordination to platinum(II), the cytotoxic effect was appreciably improved against tested cell lines, in comparison to free thiazolidine ligand. Comparing thiazolidine derivatives, it is noticeable that the less active compound (PdT) presents stronger interaction with BSA, while PtT has the weaker interaction with BSA and relatively strong binding to isolated DNA, resulting in the most cytotoxic complex. This work shows that the presence of metal is significant but it should be available for interaction. The high lability of palladium complex made this stay retainable in BSA and two metal atoms do not increase activity if it is not able to do any interaction.

Photophysical, photobiological, and mycobacteria photo-inactivation properties of new meso-tetra-cationic platinum(II) metalloderivatives at meta position.

In this manuscript, we report the photo-inactivation evaluation of new tetra-cationic porphyrins with peripheral Pt(II) complexes ate meta N-pyridyl positions in the antimicrobial photodynamic therapy (aPDT) of rapidly growing mycobacterial strains (RGM). Four different metalloderivatives were synthetized and applied. aPDT experiments in the strains of Mycobacteroides abscessus subsp. Abscessus (ATCC 19977), Mycolicibacterium fortuitum (ATCC 6841), Mycobacteroides abscessus subsp. Massiliense (ATCC 48898), and Mycolicibacterium smegmatis (ATCC 700084) conducted with adequate concentration of photosensitizers (PS) under white-light conditions at 90 min (irradiance of 50 mW cm-2 and a total light dosage of 270 J cm-2) showed that the Zn(II) derivative is the most effective PS significantly reduced the concentration of viable mycobacteria. The effectiveness of the molecule as PS for PDI studies is also clear with mycobacteria, which is strongly related with the porphyrin peripheral charge and coordination platinum(II) compounds and consequently about the presence of metal center ion. This class of PS may be promising antimycobacterial aPDT agents with potential applications in medical clinical cases and bioremediation.

Vanadium(V) complexes derived from triphenylphosphonium and hydrazides: cytotoxicity evaluation and interaction with biomolecules.

The development of coordination compounds with antineoplastic therapeutic properties is currently focused on non-covalent interactions with deoxyribonucleic acid (DNA). Additionally, the interaction profiles of these compounds with globular plasma proteins, particularly serum albumin, warrant thorough evaluation. In this study, we report on the interactions between biomolecules and complexes featuring hydrazone-type imine ligands coordinated with vanadium. The potential to enhance the therapeutic efficiency of these compounds through mitochondrial targeting is explored. This targeting is facilitated by the derivatization of ligands with triphenylphosphonium groups. Thus, this work presents the synthesis, characterization, interactions, and cytotoxicity of dioxidovanadium(V) complexes (C1-C5) with a triphenylphosphonium moiety. These VV-species are coordinated to hydrazone-type iminic ligands derived from (3-formyl-4-hydroxybenzyl)triphenylphosphonium chloride ([AH]Cl) and aromatic hydrazides ([H2L1]Cl-[H2L5]Cl). The structures of the five complexes were elucidated through single-crystal X-ray diffraction and vibrational spectroscopies, confirming the presence of dioxidovanadium(V) species in various geometries with degrees of distortion (τ = 0.03-0.50) and highlighting their zwitterionic characteristics. The molecular structural stability of C1-C5 in solution was ascertained using 1H, 19F, 31P, and 51V-nuclear magnetic resonance. Moreover, their interactions with biomolecules were evaluated using diverse spectroscopic methodologies and molecular docking, indicating moderate interactions (Kb ≈ 104 M-1) with calf thymus DNA in the minor groove and with human serum albumin, predominantly in the superficial IB subdomain. Lastly, the cytotoxic potentials of these complexes were assessed in keratinocytes of the HaCaT lineage, revealing that C1-C5 induce a reduction in metabolic activity and cell viability through apoptotic pathways.

The photophysical, photobiological, and DNA/HSA-binding properties of corroles containing carbazole and phenothiazine moieties.

This study characterized four corrole derivatives, namely Cbz-Cor, MetCbz-Cor, PTz-Cor, and PTzEt-Cor, examining their photophysical, electrochemical, photobiological, and biomolecule-binding properties. Experimental photophysical data of absorption and emission elements correlated with a theoretical analysis obtained through time-dependent density functional theory (TD-DFT). As for the photophysical properties, we observed lower fluorescence quantum yields and discernible differences between the excited and ground states, as indicated by Stokes shift values. Natural Transition Orbit (NTO) plots presented high occupied molecular orbital - low unoccupied molecular orbital (HOMO-LUMO) densities around the tetrapyrrolic macrocycle in all examples. Our findings demonstrate that corroles maintain stability in solution and offer photostability (<20 %), predominantly in DMSO(5 %)/Tris-HCl (pH 7.4) buffer solution. Furthermore, the singlet oxygen (1O2) quantum yield and log POW values underscore their potential application in photoinactivation approaches, as these corroles serve as effective ROS generators with more lipophilic features. We also evaluated their biomolecular binding capacity towards salmon sperm DNA and human serum albumin using spectroscopic techniques and molecular docking analysis for sustenance. Concerning biomolecule interaction profiles, the corrole derivatives showed a propensity for interacting in the minor grooves of the double helix DNA due to secondary forces, which were more pronounced in site III of the human serum protein.

Toxicological assessment of photoactivated tetra-cationic porphyrin molecules under white light exposure in a Caenorhabditis elegans model.

Photodynamic therapy (PDT) utilizes the potential of photosensitizing substances to absorb light energy and produce reactive oxygen species. Tetra-cationic porphyrins, which have organic or coordination compounds attached to their periphery, are heterocyclic derivatives with well-described antimicrobial and antitumoral properties. This is due to their ability to produce reactive oxygen species and their photobiological properties in solution. Consequently, these molecules are promising candidates as new and more effective photosensitizers with biomedical, environmental, and other biomedical applications. Prior to human exposure, it is essential to establish the toxicological profile of these molecules using in vivo models. In this study, we used Caenorhabditis elegans, a small free-living nematode, as a model for assessing toxic effects and predicting toxicity in preclinical research. We evaluated the toxic effects of porphyrins (neutral and tetra-cationic) on nematodes under dark/light conditions. Our findings demonstrate that tetra-methylated porphyrins (3TMeP and 4TMeP) at a concentration of 3.3 µg/mL (1.36 and 0.93 µM) exhibit high toxicity (as evidenced by reduced survival, development, and locomotion) under dark conditions. Moreover, photoactivated tetra-methylated porphyrins induce higher ROS levels compared to neutral (3TPyP and 4TPyP), tetra-palladated (3PdTPyP and 4PdTPyP), and tetra-platinated (3PtTPyP and 4PtTPyP) porphyrins, which may be responsible for the observed toxic effects.

Daylight photodynamic inactivation of cattle tick Rhipicephalus microplus by porphyrins: An alternative for the ectoparasite control.

The bovine tick Rhipicephalus microplus, a primary ectoparasite of veterinary concern, contributes significantly to disease transmission and reduced cattle productivity, resulting in substantial economic losses. The overuse of chemical acaricides has led to the emergence of resistant strains, posing a considerable challenge to veterinary medicine. Consequently, the development of alternative parasite control methods is essential to ensure livestock quality and enhance food safety worldwide. Our study introduces an innovative approach to photodynamic inactivation (PDI) of the bovine tick, harnessing natural daylight for a potential field application. Reproductive parameters (female and egg mass, egg production index, and larval hatch) were evaluated in engorged female ticks under photodynamic action using the hematoporphyrin (HP) and tetra-cationic porphyrins free-base meso-tetra-ruthenated (4-pyridyl) (RuTPyP) and its zinc(II) complex (ZnRuTPyP) as photosensitizers (PS). The results showed that there was no significant difference between the groups treated with tetra­ruthenium porphyrins and the control group. However, HP exhibits a control percentage of 97.9% at a concentration of 2.5 µmol.L-1, aligning with the expected control rates achieved by conventional chemical acaricides. Photophysical and physicochemical parameters such as the number of singlet oxygen produced and lipophilicity were discussed for each PS and related to tick control percentages. Furthermore, the interaction between HP and chitin, an important macromolecule presents in the tick's cuticle, considered as the primary target tick structure during PDI was observed by the absorption and fluorescence emission spectroscopic techniques. Therefore, the results presented here extend the potential for controlling R. microplus through photodynamic inactivation while utilizing sunlight as a source of natural irradiation.

A Vanadium(V) complexes derived from pyridoxal/salicylaldehyde. Interaction with CT-DNA/HSA, and molecular docking assessments.

With the increasing development of metallopharmaceuticals, coordination compounds become viable alternatives for therapeutic uses. Despite the importance of platinum derivatives in this area, first-row transition metals complexes are welcome due to their characteristics. Vanadium is a promising metal in this context, as it has a range of compounds with different biological applications, including anticancer therapeutic effects. In this effort, the study of interactions between coordination compounds with deoxyribonucleic acid and with human serum albumin is fundamental. In this way, ten iminic ligands were synthesized by condensing p-substituted aromatic benzohydrazides (OH, CH3, H, NO2, and NH2) with salicylaldehyde (L1As-L5As) or pyridoxal hydrochloride (L1P-L5P). These ligands have characteristics that allow the tridentate coordination of vanadium cations, leading to the formation of ten vanadium(V) complexes (C1As-C5As and C1P-C5P) with different structural features, all characterized by single-crystal X-ray diffraction, UV-Vis and infrared spectroscopies, and cyclic voltammetry. In addition, the complexes were tested for their interactions with calf thymus deoxyribonucleic acid and human serum albumin by spectroscopic assays and molecular docking calculations. These new results can contribute to further research and provide different ways to design new vanadium complexes with biological applications.

Antileishmanial activity of tetra-cationic porphyrins with peripheral Pt(II) and Pd(II) complexes mediated by photodynamic therapy.

Leishmaniasis is a neglected disease that impacts more than one billion people in endemic areas of the globe. Several drawbacks are associated with the currently existing drugs for treatment such as low effectiveness, toxicity, and the emergence of resistant strains that demonstrate the importance of looking for novel therapeutic alternatives. Photodynamic therapy (PDT) is a promising novel alternative for cutaneous leishmaniasis treatment because its topical application avoids potential side effects generally associated with oral/parenteral application. A light-sensitive compound known as photosensitizer (PS) interacts with light and molecular oxygen to generate reactive oxygen species (ROS), which promote cell death by oxidative stress through PDT approaches. Here, for the first time, we demonstrate the antileishmanial effect of tetra-cationic porphyrins with peripheral Pt(II)- and Pd(II)-polypyridyl complexes using PDT. The isomeric tetra-cationic porphyrins in the meta positions, 3-PtTPyP, and 3-PdTPyP, exhibited the highest antiparasitic activity against promastigote (IC50-pro = 41.8 nM and 46.1 nM, respectively) and intracellular amastigote forms (IC50-ama = 27.6 nM and 38.8 nM, respectively) of L. amazonensis under white light irradiation (72 J cm-2) with high selectivity (SI > 50) for both forms of parasites regarding mammalian cells. In addition, these PS induced the cell death of parasites principally by a necrotic process in the presence of white light by mitochondrial and acidic compartments accumulation. This study showed that porphyrins 3-PtTPyP and 3-PdTPyP displayed a promising antileishmanial-PDT activity with potential application for cutaneous leishmaniasis treatment.

Antimicrobial photodynamic in vitro inactivation of Enterococcus spp. and Staphylococcus spp. strains using tetra-cationic platinum(II) porphyrins.

This manuscript presents the first report on antimicrobial photo-inactivation in vitro using tetra-cationic porphyrins with peripheral platinum(II) bipyridyl complexes against Gram-positive bacteria. Two isomeric tetra-cationic porphyrins (3TPyP and 4TPyP) were tested against clinically important bacterial species. The antimicrobial activity assays were performed at specific photosensitizer (PS) concentrations under dark and white-light LED irradiation conditions for 120 min. The porphyrin 3-PtTPyP was the most efficient PS against the bacteria tested, inhibiting bacterial growth in just 15 min and 30 min at low concentrations (3.75 and 0.45 µM). The minimal inhibitory concentration of the porphyrin increased in the presence of reactive oxygen species scavengers, indicating that singlet oxygen and radical species likely participated in the photo-oxidation mechanism. In addition, the checkerboard assay that tests the association of compounds, showed a synergistic effect, suggesting a potentiation of the antibacterial effect when porphyrin was tested in combination with ciprofloxacin and vancomycin. Thus, tetra-cationic porphyrins containing platinum(II) complexes are promising agents for microbial photo-inactivation as an alternative therapy against infections.

Photodynamic inactivation of different Candida species and inhibition of biofilm formation induced by water-soluble porphyrins.

BACKGROUND: Candida spp. is the main fungal genus related to infections in humans, and its treatment has become a challenge due to the production of biofilm and its resistance/multi-resistance profile to conventional antifungals. Antimicrobial photodynamic therapy stands out as a treatment characterized by a broad spectrum of antimicrobial action, being able to induce oxidative stress in pathogens, and porphyrins are photosensitizers with high selectivity to pathogens. Thus, this work aimed to analyze the photoinactivation of different species of Candida by two cationic (4-H2TMeP+ and 3-H2TMeP+) and one anionic (4-H2TPSP‒) porphyrins. MATERIALS AND METHODS: Microdilution assays were performed to determine the MIC100, with subsequent determination of MFC100. Determination of oxidative species was done through the use of scavengers, while biofilm morphological features were investigated using the atomic force microscopy. RESULTS: Cationic porphyrins were significantly efficient in inactivating Candida albicans and non-albicans species with 100% growth inhibition and fungicidal activity (MFC100/MIC100 ≤ 4.0). The cationic porphyrins were also able to interfere in Candida spp biofilm formation. The photo-oxidative mechanism activated by 3-H2TMeP+ in Candida spp. is concurrent with the production of singlet oxygen and oxygen radical species. In the AFM analysis, 3-H2TMeP+ was able to reduce yeast adhesion to the surface. CONCLUSIONS: Cationic porphyrins can photo-inactivate different species of Candida in both planktonic and biofilm-associated forms, and reduce the adhesion of these fungi to the surface.

Antimicrobial activity of water-soluble tetra-cationic porphyrins on Pseudomonas aeruginosa.

This manuscript presents the cytotoxicity, antimicrobial activity, antibiofilm preliminary properties, and associated therapy with commercial drugs using water-soluble tetra-cationic porphyrins against Pseudomonas aeruginosa. Two commercial tetra-cationic porphyrins were tested against a standard strain of P. aeruginosa 01 (PA01) in antibacterial activity assays under dark conditions and irradiated with white light for 120 min. Porphyrin 4-H2TMePor showed better antimicrobial activity and was chosen for further tests. Increased minimum inhibitory concentration was observed in the presence of reactive oxygen species, suggesting that photooxidation was mediated by the singlet oxygen production. In the time-kill curve assay, 4-H2TMePor inhibited bacterial growth in 90 min of irradiation. The checkerboard assay revealed synergistic interactions. Biofilms of the standard PA01 strain and three clinical isolates were formed. The biofilm destruction assay was more efficient for PA01, significantly reducing the biofilm biomass formed compared to the positive control. The associated treatment to destroy the biofilm potentiated a significant decrease in the biofilm biomass compared to the positive control. The photosensitizer did not damage human keratinocytes or mouse fibroblasts in the cytotoxicity assays, demonstrating the safety of using 4-H2TMePor. Atomic force microscopy indicated lower adhesion force, higher cell wall deformation, and higher dissipation energy in the treated control compared to untreated PA01. Given our findings, it is evident that water-soluble tetra-cationic porphyrins have excellent antimicrobial and a preliminary antibiofilm activity against Gram-negative bacteria, proving to be a potential photosensitizer for clinical use.