Synthesis and characterization of new acid-functionalized porphyrins displaying antimicrobial activity against gram positive bacteria, yeasts and filamentous fungi with or without ultra-high irradiance

The antimicrobial activity of new acid-functionalized porphyrins, with or without ultra-high irradiance, was investigated. Antibacterial efficacy was evaluated against Staphylococcus aureus (methicillin-resistant or methicillin-sensitive strains) and antifungal efficacy was evaluated against the yeast Candida albicans and the filamentous fungi Aspergillus fumigatus. Overall, the porphyrins tested are more effective against S. aureus. The best results were obtained with zinc diacid porphyrins 4 and 5 after only 3 min of ultra-high irradiation (500 mW/cm2, 405 nm), demonstrating that acid-functionalized porphyrins are promising as novel antimicrobial drugs for surface disinfection.

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.

A Novel Strategy Based on Zn(II) Porphyrins and Silver Nanoparticles to Photoinactivate Candida albicans

Background

Photodynamic inactivation (PDI) is an attractive alternative to treat Candida albicans infections, especially considering the spread of resistant strains. The combination of the photophysical advantages of Zn(II) porphyrins (ZnPs) and the plasmonic effect of silver nanoparticles (AgNPs) has the potential to further improve PDI. Here, we propose the novel association of polyvinylpyrrolidone (PVP) coated AgNPs with the cationic ZnPs Zn(II) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin or Zn(II) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin to photoinactivate C. albicans.

Methods

AgNPs stabilized with PVP were chosen to allow for (i) overlap between the NP extinction and absorption spectra of ZnPs and (ii) favor AgNPs-ZnPs interaction; prerequisites for exploring the plasmonic effect. Optical and zeta potential (ζ) characterizations were performed, and reactive oxygen species (ROS) generation was also evaluated. Yeasts were incubated with individual ZnPs or their respective AgNPs-ZnPs systems, at various ZnP concentrations and two proportions of AgNPs, then irradiated with a blue LED. Interactions between yeasts and the systems (ZnP alone or AgNPs-ZnPs) were evaluated by fluorescence microscopy.

Results

Subtle spectroscopic changes were observed for ZnPs after association with AgNPs, and the ζ analyses confirmed AgNPs-ZnPs interaction. PDI using ZnP-hexyl (0.8 µM) and ZnP-ethyl (5.0 µM) promoted a 3 and 2 log₁₀ reduction of yeasts, respectively. On the other hand, AgNPs-ZnP-hexyl (0.2 µM) and AgNPs-ZnP-ethyl (0.6 µM) systems led to complete fungal eradication under the same PDI parameters and lower porphyrin concentrations. Increased ROS levels and enhanced interaction of yeasts with AgNPs-ZnPs were observed, when compared with ZnPs alone.

Conclusion

We applied a facile synthesis of AgNPs which boosted ZnP efficiency. We hypothesize that the plasmonic effect combined with the greater interaction between cells and AgNPs-ZnPs systems resulted in an efficient and improved fungal inactivation. This study provides insight into the application of AgNPs in PDI and helps diversify our antifungal arsenal, encouraging further developments toward inactivation of resistant Candida spp.

Effect of the nature of the chelated metal on the photodynamic activity of metalloporphyrins

Coordination of metal ions by the tetrapyrrolic macrocyclic ring of porphyrin-based photosensitizers (PSs) affects their photophysical properties and consequently, their photodynamic activity. Diamagnetic metals increase the singlet oxygen quantum yield while paramagnetic metals have the opposite effect. Since singlet oxygen is considered the main cell-damaging species in photodynamic therapy (PDT), the nature of the chelated cation would directly affect PDT efficacy. This expectation, however, is not always supported by experimental results and numerous exceptions have been reported. Understanding the effect of the chelated metal is hindered because different chelators were used. The aim of this work was to investigate the effect of the nature of chelated cation on the photophysical and photodynamic properties of metalloporphyrins, using the same tetrapyrrole core as a chelator of Ag(II), Cu(II), Fe(III), In(III), Mn(III), or Zn(II). Results demonstrated that with the exception of Ag(II), all paramagnetic metalloporphyrins were inefficient as generators of singlet oxygen and did not act as PSs. In contrast, the coordination of diamagnetic ions produced highly efficient PSs. The unexpected photodynamic activity of the Ag(II)-containing porphyrin was attributed to reduction of the chelated Ag(II) to Ag(I) or to demetallation of the complex, caused by cellular reductants and/or by exposure to light. Our results indicate that in biological systems, where PSs localize to various organelles and are subjected to the action of enzymes, reactive metabolites, and reducing or oxidizing agents, their physicochemical and photosensitizing properties change. Consequently, the photophysical properties alone cannot predict the anticancer efficacy of a PS.

Polylactide-Meso-Substituted Arylporphyrin Composites: Structure, Properties and Antibacterial Activity

The structural features and antibacterial properties of polymer-porphyrin composites were investigated. Meso-substituted arylporphyrin 0.2-0.5 wt.% was immobilized in a polylactide matrix. The immobilization of porphyrin causes a bathochromic shift and splitting of the Soret band. This study of the morphology of the obtained composites demonstrated a uniform distribution of the meso-substituted arylporphyrin in the polylactide matrix. It was determined by the X-ray diffraction analysis that porphyrin does not affect the α-form of polylactide crystalline formations. However, its addition into the polymer somewhat reduces the melting point (by 1-2 °C) and the degree of crystallinity of polylactide (by 3-4%). The elastic characteristics of the resulting systems were determined by the ultrasonic method, and a decrease in the density of the samples with an increase of the arylporphyrin content was shown. According to the results of the biological test, the dark toxicity of the obtained composites against the microorganisms Staphylococcus aureus, Salmonella Typhimurium and Escherichia coli was shown. Immobilizates containing 0.4 and 0.5 wt.% porphyrin showed the best antibacterial effect. The antibacterial activity of the studied composites makes it possible to attribute the polylactide-porphyrin systems to promising materials in the field of medicine and bioengineering.

Photoinactivation of Yeast and Biofilm Communities of Candida albicans Mediated by ZnTnHex-2-PyP4+ Porphyrin

Candida albicans is the main cause of superficial candidiasis. While the antifungals available are defied by biofilm formation and resistance emergence, antimicrobial photodynamic inactivation (aPDI) arises as an alternative antifungal therapy. The tetracationic metalloporphyrin Zn(II) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin (ZnTnHex-2-PyP⁴⁺) has high photoefficiency and improved cellular interactions. We investigated the ZnTnHex-2-PyP⁴⁺ as a photosensitizer (PS) to photoinactivate yeasts and biofilms of C. albicans strains (ATCC 10231 and ATCC 90028) using a blue light-emitting diode. The photoinactivation of yeasts was evaluated by quantifying the colony forming units. The aPDI of ATCC 90028 biofilms was assessed by the MTT assay, propidium iodide (PI) labeling, and scanning electron microscopy. Mammalian cytotoxicity was investigated in Vero cells using MTT assay. The aPDI (4.3 J/cm²) promoted eradication of yeasts at 0.8 and 1.5 µM of PS for ATCC 10231 and ATCC 90028, respectively. At 0.8 µM and same light dose, aPDI-treated biofilms showed intense PI labeling, about 89% decrease in the cell viability, and structural alterations with reduced hyphae. No considerable toxicity was observed in mammalian cells. Our results introduce the ZnTnHex-2-PyP⁴⁺ as a promising PS to photoinactivate both yeasts and biofilms of C. albicans, stimulating studies with other Candida species and resistant isolates.

Investigation of powerful fungicidal activity of tetra-cationic platinum(II) and palladium(II) porphyrins by antimicrobial photodynamic therapy assays

This manuscript reports enhanced antimicrobial photoinactivation using tetra-cationic porphyrins with peripheral platinum(II) and palladium(II) complexes against fungal dermatophyte strains. Six different positively charged porphyrins were used and applied in antimicrobial photodynamic therapy experiments (aPDT) against dermatophyte fungi colonies. The microbiological tests were conducted with an adequate concentration of photosensitizer (PS) under white-light irradiation for 120 min and the most effective PS meta isomer 3PtP significantly reduced the concentration of viable fungal colony. In this way, tetra-cationic porphyrins containing platinum(II)-bipyridyl complexes may be promising fungicidal aPDT agents with potential applications in future clinical cases.

Efficient photodynamic inactivation of Leishmania parasites mediated by lipophilic water-soluble Zn(II) porphyrin ZnTnHex-2-PyP4

BACKGROUND

Photodynamic inactivation (PDI) is emerging as a promising alternative for cutaneous leishmaniasis (CL). The chemotherapy currently used presents adverse effects and cases of drug resistance have been reported. ZnTnHex-2-PyP⁴⁺ is a porphyrin with a high potential as a photosensitizer (PS) for PDI, due to its photophysical properties, structural stability, and cationic/amphiphilic character that can enhance interaction with cells. This study aimed to investigate the photodynamic effects mediated by ZnTnHex-2-PyP⁴⁺ on Leishmania parasites.

METHODS

ZnTnHex-2-PyP⁴⁺ stability was evaluated using accelerated solvolysis conditions. The photodynamic action on promastigotes was assessed by (i) viability assays, (ii) mitochondrial membrane potential evaluation, and (iii) morphological analysis. The PS-promastigote interaction was studied. PDI on amastigotes and the cytotoxicity on macrophages were also analyzed.

RESULTS

ZnTnHex-2-PyP⁴⁺, under submicromolar concentration, led to immediate inactivation of more than 95% of promastigotes. PDI promoted intense mitochondrial depolarization, loss of the fusiform shape, and plasma membrane wrinkling in promastigotes. Fluorescence microscopy revealed a punctate PS labeling in the parasite cytoplasm. PDI also led to reductions of ca. 64% in the number of amastigotes/macrophage and 70% in the infection index after a single treatment session. No noteworthy toxicity was observed on mammalian cells.

CONCLUSIONS

ZnTnHex-2-PyP⁴⁺ is stable against demetallation and more efficient as PS than the ethyl analogue ZnTE-2-PyP⁴⁺, indicating readiness for evaluation in in vivo studies as an alternative approach to CL.

GENERAL SIGNIFICANCE

This report highlighted promising photodynamic effects mediated by ZnTnHex-2-PyP⁴⁺ on Leishmania parasites, opening up perspectives for applications in CL pre-clinical assays and PDI of other microorganisms.

Novel Cationic Meso-Arylporphyrins and Their Antiviral Activity against HSV-1

This work is devoted to the search for new antiherpes simplex virus type 1 (HSV-1) drugs among synthetic tetrapyrroles and to an investigation of their antiviral properties under nonphotodynamic conditions. In this study, novel amphiphilic 5,10,15,20-tetrakis(4-(3-pyridyl-n-propanoyl)oxyphenyl)porphyrin tetrabromide (3a), 5,10,15,20-tetrakis(4-(6-pyridyl-n-hexanoyl)oxyphenyl)porphyrin tetrabromide (3b) and known 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetraiodide (TMePyP) were synthesized, and their dark antiviral activity in vitro against HSV-1 was studied. The influence of porphyrin’s nanosized delivery vehicles based on Pluronic F127 on anti-HSV-1 activity was estimated. All the received compounds 3a, 3b and TMePyP showed virucidal efficiency and had an effect on viral replication stages. The new compound 3b showed the highest antiviral activity, close to 100%, with the lowest concentration, while the maximum TMePyP activity was observed with a high concentration; porphyrin 3a was the least active. The inclusion of the synthesized compounds in Pluronic F-127 polymeric micelles had a noticeable effect on antiviral activity only at higher porphyrin concentrations. Action of the received compounds differs by influence on the early or later reproduction stages. While 3a and TMePyP acted on all stages of the viral replication cycle, porphyrin 3b inhibited viral replication during the early stages of infection. The resulting compounds are promising for the development of utilitarian antiviral agents and, possibly, medical antiviral drugs.

Metalloporphyrins in Medicine: From History to Recent Trends

The history of metalloporphyrins dates back more than 200 years ago. Metalloporphyrins are excellent catalysts, capable of forming supramolecular systems, participate in oxygen photosynthesis, transport, and used as contrast agents or superoxide dismutase mimetics. Today, metalloporphyrins represent complexes of conjugated π-electron system and metals from the entire periodic system. However, the effect of these compounds on living systems has not been fully understood, and researchers are exploring the properties of metalloporphyrins thereby extending their further application. This review provides an overview of the variety of metalloporphyrins that are currently used in different medicine fields and how metalloporphyrins became the subject of scientists' interest. Currently, metalloporphyrins utilization has expanded significantly, which gave us an opprotunuty to summarize recent progress in metalloporphyrins derivatives and prospects of their application in the treatment and diagnosis of different diseases.

Antibacterial Activity of Synthetic Cationic Iron Porphyrins

Widespread antibiotic resistance demands new strategies for fighting infections. Porphyrin-based compounds were long ago introduced as photosensitizers for photodynamic therapy, but light-independent antimicrobial activity of such compounds has not been systematically explored. The results of this study demonstrate that synthetic cationic amphiphilic iron N-alkylpyridylporphyrins exert strong bactericidal action at concentrations as low as 5 μM. Iron porphyrin, FeTnHex-2-PyP, which is well tolerated by laboratory animals, efficiently killed Gram-negative and Gram-positive microorganisms. Its bactericidal activity was oxygen-independent and was controlled by the lipophilicity and accumulation of the compound in bacterial cells. Such behavior is in contrast with the anionic gallium protoporphyrin IX, whose efficacy depends on cellular heme uptake systems. Under aerobic conditions, however, the activity of FeTnHex-2-PyP was limited by its destruction due to redox-cycling. Neither iron released from the Fe-porphyrin nor other decomposition products were the cause of the bactericidal activity. FeTnHex-2-PyP was as efficient against antibiotic-sensitive E. coli and S. aureus as against their antibiotic-resistant counterparts. Our data demonstrate that development of amphiphilic, positively charged metalloporphyrins might be a promising approach in the introduction of new weapons against antibiotic-resistant strains.

Dorsal tongue porphyrin autofluorescence and Candida saprophytism: A prospective observational study

Aim

To investigate the correlation between the dorsal tongue porphyrin autofluorescence, revealed using VELscope, and Candida saprophytism.

Material and methods

Consecutive patients underwent an autofluorescence examination by the VELscope device to establish the presence or absence of porphyrin fluorescence. A tongue swab was collected for the Candida cultural test. Sensitivity, specificity, accuracy, negative predictive value and positive predictive value were calculated considering the oral swab as the gold standard. The degree of agreement between the two tests was calculated using Cohen's K coefficient.

Results

One hundred twenty-six patients were enrolled. Porphyrin fluorescence method showed a sensitivity of 78%, specificity of 76% and an accuracy of 78%. Negative predictive value and positive predictive value were respectively 90% and 59%. The strength of agreement between the two methods resulted to be moderate (k = 0.551).

Conclusions

Off-label use of tongue autofluorescence examination to detect the presence of Candida species is characterized by a loss of porphyrin fluorescence. The high negative predictive value of porphyrin fluorescence loss suggests its use in preliminary selection of Candida carriers, in order to plan preventive and therapeutic strategies.

Crossing the First Threshold: New Insights into the Influence of the Chemical Structure of Anionic Porphyrins on Plant Cell Wall Interactions and Photodynamic Cell Death Induction

In this study, our fundamental research interest was to understand how negatively charged porphyrins could interact with a plant cell wall and further act inside cells. Thus, three anionic porphyrins differing in their anionic external groups (carboxylates, sulfonates, and phosphonates) were tested. First, the tobacco cell wall was isolated to monitor in vitro its interactions with the three different anionic porphyrins. Unexpectedly, these negatively charged molecules were able to bind to the negatively charged cell wall probably by weak bonds such as hydrogen bonds and/or electrostatic interactions when the tetrapyrrolic core was protonated. Moreover, we showed that at the pH of spent culture medium (4.5), the neutrality of the carboxylated porphyrin (TPPC) facilitated its cell wall crossing while the diffusion of the two other sulfonated (TPPS) or phosphonated (TPPP) porphyrins that remained anionic was delayed. Once inside Tobacco Bright Yellow-2 (TBY-2) cells, TPPC induced higher levels of production of both H2O2 and malondialdehyde compared to TPPS after illumination. That result correlated well with strong cell death induction by photoactivated TPPC. Furthermore, reactive oxygen species-scavenging enzymes such as catalase, peroxidases, and superoxide dismutase were also strongly downmodulated in response to TPPC, while these enzymes were almost unchanged in response to photoactivated TPPS. To the best of our knowledge, this is the first study that took into account the whole story from interactions of porphyrins with a plant cell wall to their photodynamic activity inside the cells.

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.

Sublethal Photodynamic Treatment Does Not Lead to Development of Resistance

A promising new alternative approach for eradication of antibiotic-resistant strains is to expose microbes to photosensitizers, which upon illumination generate reactive oxygen species. Among the requirements for a potent, medically applicable photosensitizer, are high efficacy in killing microbes and low toxicity to the host. Since photodynamic treatment is based on production of reactive species which are potentially DNA damaging and mutagenic, it might be expected that under selective pressure, microbes would develop resistance. The aim of this study was to determine if antibacterial photodynamic treatment with a highly photoefficient photosensitizer, Zn(II) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin would lead to development of resistance. To answer that question, bacterial cultures were subjected to multiple cycles of sublethal photodynamic stress and regrowth, and to continuous growth under photodynamic exposure. Antibiotic-resistant Staphylococcus aureus and Escherichia coli clinical isolates were also tested for susceptibility to photodynamic inactivation and for development of resistance. Results demonstrated that multiple photodynamic exposures and regrowth of surviving cells or continuous growth under sublethal photodynamic conditions, did not lead to development of resistance to photosensitizers or to antibiotics. Antibiotic-resistant E. coli and S. aureus were as sensitive to photodynamic killing as were their antibiotic-sensitive counterparts and no changes in their sensitivity to antibiotics or to photodynamic inactivation after multiple cycles of photodynamic treatment and regrowth were observed. In conclusion, photosensitizers with high photodynamic antimicrobial efficiency can be used successfully for eradication of antibiotic-resistant bacterial strains without causing development of resistance.

Theoretical study on photophysical properties of three high water solubility polypyridyl complexes for two-photon photodynamic therapy

Two-photon photodynamic therapy (TP-PDT) is a very promising treatment that has drawn much attention in recent years due to its ability to penetrate deeper into tissues and minimize the damage to normal cells.