Can Porphyrin-Triphenylphosphonium Conjugates Enhance the Photosensitizer Performance Toward Bacterial Strains?

Antimicrobial photodynamic treatment (aPDT) offers an alternative option for combating microbial pathogens, and in this way, addressing the challenges of growing antimicrobial resistance. In this promising and effective approach, cationic porphyrins and related macrocycles have emerged as leading photosensitizers (PS) for aPDT. In general, their preparation occurs via N-alkylation of nitrogen-based moieties with alkyl halides, which limits the ability to fine-tune the features of porphyrin-based PS. Herein, is reported that the conjugation of porphyrin macrocycles with triphenylphosphonium units created a series of effective cationic porphyrin-based PS for aPDT. The presence of positive charges at both the porphyrin macrocycle and triphenylphosphonium moieties significantly enhances the photodynamic activity of porphyrin-based PS against both Gram-positive and Gram-negative bacterial strains. Moreover, bacterial photoinactivation is achieved with a notable reduction in irradiation time, exceeding 50%, compared to 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP), used as the reference and known as good PS. The improved capability of the porphyrin macrocycle to generate singlet oxygen combined with the enhanced membrane interaction promoted by the presence of triphenylphosphonium moieties represents a promising approach to developing porphyrin-based PS with enhanced photosensitizing activity.

TMPyP binding evokes a complex, tunable nanomechanical response in DNA

TMPyP is a porphyrin capable of DNA binding and used in photodynamic therapy and G-quadruplex stabilization. Despite its broad applications, TMPyP's effect on DNA nanomechanics is unknown. Here we investigated, by manipulating λ-phage DNA with optical tweezers combined with microfluidics in equilibrium and perturbation kinetic experiments, how TMPyP influences DNA nanomechanics across wide ranges of TMPyP concentration (5-5120 nM), mechanical force (0-100 pN), NaCl concentration (0.01-1 M) and pulling rate (0.2-20 μm/s). Complex responses were recorded, for the analysis of which we introduced a simple mathematical model. TMPyP binding, which is a highly dynamic process, leads to dsDNA lengthening and softening. dsDNA stability increased at low (<10 nM) TMPyP concentrations, then decreased progressively upon increasing TMPyP concentration. Overstretch cooperativity decreased, due most likely to mechanical roadblocks of ssDNA-bound TMPyP. TMPyP binding increased ssDNA's contour length. The addition of NaCl at high (1 M) concentration competed with the TMPyP-evoked nanomechanical changes. Because the largest amplitude of the changes is induced by the pharmacologically relevant TMPyP concentration range, this porphyrin derivative may be used to tune DNA's structure and properties, hence control the wide array of biomolecular DNA-dependent processes including replication, transcription, condensation and repair.

Photodynamic treatment of Staphylococcus aureus with non-iron hemin analogs in the presence of hydrogen peroxide

Bacteria subjected to antiseptic or antibiotic stress often develop tolerance, a trait that can lead to permanent resistance. To determine whether photodynamic agents could be used to counter tolerance, we evaluated three non-iron hemin analogs (M-PpIX; M = Al, Ga, In) as targeted photosensitizers for antimicrobial photodynamic inactivation (aPDI) following exposure to sublethal H2O2. Al-PpIX is an active producer of ROS whereas Ga- and In-PpIX are more efficient at generating singlet oxygen. Al- and Ga-PpIX are highly potent aPDI agents against S. aureus and methicillin-resistant strains (MRSA) with antimicrobial activity (3 log reduction in colony-forming units) at nanomolar concentrations. The aPDI activities of Al- and Ga-PpIX against S. aureus were tested in the presence of 1 mM H2O2 added at different stages of growth. Bacteria exposed to H2O2 during log-phase growth were less susceptible to aPDI but bacteria treated with H2O2 in their postgrowth phase exhibited aPDI hypersensitivity, with no detectable colony growth after treatment with 15 nM Ga-PpIX.

TMPyP-mediated photoinactivation of Pseudomonas aeruginosa improved in the presence of a cationic polymer

Pseudomonas aeruginosa is one of the most refractory organisms to antibiotic treatment and appears to be one of the least susceptible to photodynamic treatment. TMPyP is effective in the photoinactivation of P. aeruginosa, and the co-administration with the cationic polymer Eudragit®-E100 (Eu) potentiates this effect against isolates both sensitive and resistant to antibiotics. The fluorescent population (>98%) observed by flow cytometry after exposure to Eu + TMPyP remained unchanged after successive washings, indicating a stronger interaction/internalization of TMPyP in the bacteria, which could be attributed to the rapid neutralization of surface charges. TMPyP and Eu produced depolarization of the cytoplasmic membrane, which increased when both cationic compounds were combined. Using confocal laser scanning microscopy, heterogeneously distributed fluorescent areas were observed after TMPyP exposure, while homogeneous fluorescence and enhanced intensity were observed with Eu + TMPyP. The polymer caused alterations in the bacterial envelopes that contributed to a deeper and more homogeneous interaction/internalization of TMPyP, leading to a higher probability of damage by cytotoxic ROS and explaining the enhanced result of photodynamic inactivation. Therefore, Eu acts as an adjuvant without being by itself capable of eradicating this pathogen. Moreover, compared with other therapies, this combinatorial strategy with a polymer approved for pharmaceutical applications presents advantages in terms of toxicity risks.

Albumin Hydrogel-Coated Mesoporous Silica Nanoparticle as a Carrier of Cationic Porphyrin and Ratiometric Fluorescence pH Sensor

Here, we report that a mesoporous silica nanoparticle (MSN) coated with a fluoresceine-labeled bovine serum albumin (F-BSA) hydrogel layer works as a temperature-responsive nanocarrier for tetrakis-N-methylpyridyl porphyrin (TMPyP) and as a fluorescence ratiometric pH probe. F-BSA hydrogel-coated MSN containing TMPyP (F-BSA/MSN/TMPyP) was synthesized by thermal gelation of denatured F-BSA on the external surface of MSN. The F-BSA hydrogel layer was composed of an inner hard corona layer and an outer soft layer and was stable under physiological conditions. F-BSA/MSN/TMPyP exhibited temperature-dependent exponential release of TMPyP. In this release profile, the MSN was found to be a suitable host for stable encapsulation of tetracationic TMPyP by electrostatic interactions, and the F-BSA hydrogel layer mediated the diffusion of TMPyP from the MSN pore interior into the solution phase. Increasing temperature promoted partitioning of TMPyP from the pore interior to the F-BSA hydrogel layer, from where it was spontaneously released into the bulk solution phase by cation exchange. F-BSA/MSN/TMPyP also gave a linear ratiometric fluorescence response (1.3 per pH unit) in the pH range from 6.1 to 8.9.

Antimicrobial Potency of Fmoc-Phe-Phe Dipeptide Hydrogels with Encapsulated Porphyrin Chromophores Is a Promising Alternative in Antimicrobial Resistance

Antimicrobial resistance (AMR) poses a significant global health risk as a consequence of misuse of antibiotics. Owing to the increasing antimicrobial resistance, it became imperative to develop novel molecules and materials with antimicrobial properties. Porphyrins and metalloporphyrins are compounds which present antimicrobial properties especially after irradiation. As a consequence, porphyrinoids have recently been utilized as antimicrobial agents in antimicrobial photodynamic inactivation in bacteria and other microorganisms. Herein, we report the encapsulation of porphyrins into peptide hydrogels which serve as delivery vehicles. We selected the self-assembling Fmoc-Phe-Phe dipeptide, a potent gelator, as a scaffold due to its previously reported biocompatibility and three different water-soluble porphyrins as photosensitizers. We evaluated the structural, mechanical and in vitro degradation properties of these hydrogels, their interaction with NIH3T3 mouse skin fibroblasts, and we assessed their antimicrobial efficacy against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria. We found out that the hydrogels are cytocompatible and display antimicrobial efficiency against both strains with the zinc porphyrins being more efficient. Therefore, these hydrogels present a promising alternative for combating bacterial infections in the face of growing AMR concerns.

Hydrophilic Biocompatible Fluorescent Organic Nanoparticles as Nanocarriers for Biosourced Photosensitizers for Photodynamic Therapy

Most photosensitizers of interest for photodynamic therapy-especially porphyrinoids and chlorins-are hydrophobic. To circumvent this difficulty, the use of nanocarriers is an attractive strategy. In this perspective, we have developed highly water-soluble and biocompatible fluorescent organic nanoparticles (FONPs) made from citric acid and diethyltriamine which are then activated by ethlynene diamine as nanoplatforms for efficient photosensitizers (PSs). Purpurin 18 (Pp18) was selected as a biosourced chlorin photosensitizer combining the efficient single oxygen generation ability and suitable absorption in the biological spectral window. The simple reaction of activated FONPs with Pp18, which contains a reactive anhydride ring, yielded nanoparticles containing both Pp18 and Cp6 derivatives. These functionalized nanoparticles combine solubility in water, high singlet oxygen generation quantum yield in aqueous media (0.72) and absorption both in the near UV region (FONPS) and in the visible region (Soret band approximately 420 nm as well as Q bands at 500 nm, 560 nm, 660 nm and 710 nm). The functionalized nanoparticles retain the blue fluorescence of FONPs when excited in the near UV region but also show deep-red or NIR fluorescence when excited in the visible absorption bands of the PSs (typically at 520 nm, 660 nm or 710 nm). Moreover, these nanoparticles behave as efficient photosensitizers inducing colorectal cancer cell (HCT116 and HT-29 cell lines) death upon illumination at 650 nm. Half maximal inhibitory concentration (IC50) values down to, respectively, 0.04 and 0.13 nmol/mL were observed showing the potential of FONPs[Cp6] for the PDT treatment of cancer. In conclusion, we have shown that these novel biocompatible nanoparticles, which can be elaborated from biosourced components, both show deep-red emission upon excitation in the red region and are able to produce singlet oxygen with high efficiency in aqueous environments. Moreover, they show high PDT efficiency on colorectal cancer cells upon excitation in the deep red region. As such, these functional organic nanoparticles hold promise both for PDT treatment and theranostics.

Nanomaterials for Disease Treatment by Modulating the Pyroptosis Pathway

Pyroptosis differs significantly from apoptosis and cell necrosis as an alternative mode of programmed cell death. Its occurrence is mediated by the gasdermin protein, leading to characteristic outcomes including cell swelling, membrane perforation, and release of cell contents. Research underscores the role of pyroptosis in the etiology and progression of many diseases, making it a focus of research intervention as scientists explore ways to regulate pyroptosis pathways in disease management. Despite numerous reviews detailing the relationship between pyroptosis and disease mechanisms, few delve into recent advancements in nanomaterials as a mechanism for modulating the pyroptosis pathway to mitigate disease effects. Therefore, there is an urgent need to fill this gap and elucidate the path for the use of this promising technology in the field of disease treatment. This review article delves into recent developments in nanomaterials for disease management through pyroptosis modulation, details the mechanisms by which drugs interact with pyroptosis pathways, and highlights the promise that nanomaterial research holds in driving forward disease treatment.

Kinetics, Equilibrium, and Thermodynamics for Conjugation of Chitosan with Insulin-Mimetic [meso-Tetrakis(4-sulfonatophenyl)porphyrinato]oxovanadate(IV)(4-) in an Aqueous Solution

This study investigated the conjugation of chitosan with the insulin-mimetic [meso-tetrakis(4-sulfonatophenyl)porphyrinato]oxovanadate(IV)(4-), VO(tpps), in an aqueous medium as a function of conjugation time, VO(tpps) concentrations, and temperatures. To validate the synthesis of chitosan-VO(tpps) conjugate, UV-visible and Fourier transform infrared spectrophotometric techniques were utilized. Conjugate formation is ascribed to the electrostatic interaction between the NH3+ units of chitosan and the SO3- units of VO(tpps). Chitosan enhances the stability of VO(tpps) in an aqueous medium (pH 2.5). VO(tpps) conjugation with chitosan was best explained by pseudo-second-order kinetic and Langmuir isotherm models based on kinetic and isotherm studies. The Langmuir equation determined that the maximal ability of VO(tpps) conjugated with each gram of chitosan was 39.22 μmol at a solution temperature of 45 °C. Activation energy and thermodynamic studies (Ea: 8.78 kJ/mol, ΔG: -24.52 to -27.55 kJ/mol, ΔS: 204.22 J/(mol K), and ΔH: 37.30 kJ/mol) reveal that conjugation is endothermic and physical in nature. The discharge of VO(tpps) from conjugate was analyzed in freshly prepared 0.1 mol/L phosphate buffer (pH 7.4) at 37 °C. The release of VO(tpps) from the conjugate is a two-phase process best explained by the Higuchi model, according to a kinetic analysis of the release data. Taking into consideration all experimental findings, it is proposed that chitosan can be used to formulate both solid and liquid insulin-mimetic chitosan-VO(tpps) conjugates.

A bioinspired silica nanocomposite for enhanced multidrug-resistant bacteria treatment and wash-free imaging

Bacterial infections have posed significant threats to public health due to the emergence of antibiotic resistance. In this work, a novel antibacterial composite nanomaterial based on spiky mesoporous silica spheres loaded with poly(ionic liquid)s and aggregation-induced emission luminogens (AIEgens) was designed for efficient multidrug-resistant (MDR) bacteria treatment and imaging. The nanocomposite exhibited excellent and long-term antibacterial activity towards both Gram-negative and Gram-positive bacteria. Meanwhile, fluorescent AIEgens facilitate real-time bacterial imaging. Our study provides a multifunctional platform and a promising alternative to antibiotics for combating pathogenic MDR bacteria.

Antimicrobial and Antibiofilm Photodynamic Action of Photosensitizing Nanoassemblies Based on Sulfobutylether-β-Cyclodextrin

Developing new broad-spectrum antimicrobial strategies, as alternatives to antibiotics and being able to efficiently inactivate pathogens without inducing resistance, is one of the main objectives in public health. Antimicrobial photodynamic therapy (aPDT), based on the light-induced production of reactive oxygen species from photosensitizers (PS), is attracting growing interest in the context of infection treatment, also including biofilm destruction. Due to the limited photostability of free PS, delivery systems are increasingly needed in order to decrease PS photodegradation, thus improving the therapeutic efficacy, as well as to reduce collateral effects on unaffected tissues. In this study, we propose a photosensitizing nanosystem based on the cationic porphyrin 5,10,15,20-tetrakis (N-methyl- 4-pyridyl)-21H,23H-porphyrin (TMPyP), complexed with the commerical sulfobutylether-beta-cyclodextrin (CAPTISOL®), at a 1:50 molar ratio (CAPTISOL®/TMPyP)50_1. Nanoassemblies based on (CAPTISOL®/TMPyP)50_1 with photodynamic features exhibited photo-antimicrobial activity against Gram-negative and Gram-positive bacteria. Moreover, results from P. aeruginosa reveal that CAPTISOL® alone inhibits pyocyanin (PYO) production, also affecting bacterial biofilm formation. Finally, we obtained a synergistic effect of inhibition and destruction of P. aeruginosa biofilm by using the combination of CAPTISOL® and TMPyP.

Design of A3B-Porphyrin Conjugates with Terpyridine as Potential Theranostic Agents: Synthesis, Complexation with Fe(III), Gd(III), and Photodynamic Activity

This paper reports on the design and synthesis of new multifunctional porphyrin-based therapeutic agents for potential therapeutic and diagnostic applications. Zinc complexes of A3B-type meso-arylporphyrins containing OH- and COOH- groups were modified with chelating ligands based on 4'-(4-methylphenyl)-2,2':6',2″-terpyridine derivatives in high yields. Novel complexes with Gd(III), Fe(III) were obtained for these conjugates. Aggregation behaviour in solutions of different solubilisers was studied to inform the selection of the optimal solubilising platform for the porphyrins obtained; their photophysical and photochemical properties were also characterised. Micellar Pluronic F127 formulation was found to be the most effective solubiliser for stabilising the fluorescence-active monomolecular form of the photosensitisers (PS). In vitro cytotoxicity of the compounds was studied on the HEP-2 cell line with and without irradiation for 1.5 and 24 h. As a result, the IC50 of compounds 12 and 14 at an irradiation dose of 8.073 J/cm2 was shown to be 1.87 ± 0.333 and 1.4 ± 0.152 μM, respectively; without irradiation, the compound had no toxic effect within the studied concentration range (1.5 h). A test for the inhibition of metabolic cooperation or promoter activity was also performed for the abovementioned compounds, showing the efficacy and safety of the conjugates obtained. Preliminary data have indicated the high potential of the new type of PS to be promising molecular theranostic agents.

In vitro porphyrin-based photodynamic therapy against mono and polyculture of multidrug-resistant bacteria isolated from integumentary infections in animals

Multidrug-resistant (MDR) organisms have been frequently isolated from integumentary lesions of animals, and these lesions are usually infected by more than one pathogen. This study evaluated an in vitro antimicrobial photodynamic therapy (aPDT) using two water-soluble tetra-cationic porphyrins (3-H₂TMeP and 4-H₂TMeP) against mono and polyculture of MDR bacteria isolated from dogs, cats, and horses. Ten isolates of MDR bacteria (two of each species: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia marcescens, and Staphylococcus pseudointermedius) were used to evaluate aPDT against the monoculture using a non-cytotoxic concentration of 3-H₂TMeP and 4-H₂TMeP porphyrins (40 µM), with 30 min of light irradiation in Gram-positive and 90 min for Gram-negative bacteria. The aPDT using the 4-H₂TMeP porphyrin was also tested against five different polycultures (Coagulase positive Staphylococcus (CPS) and Pseudomonas sp.; E. coli and Proteus sp.; Pseudomonas sp. and Proteus sp.; CPS and E. coli; and CPS and Proteus sp.) for 90 min. The efficacy of both treatments was evaluated by plating the solution exposed to light or kept in the dark and counting the colonies forming units after 24 h of incubation at 37 °C. Atomic force microscope analysis was used to map bacteria morphological changes and extract adhesion force parameters from the bacteria membranes. Only the 4-H₂TMeP porphyrin had antibacterial activity against MDR bacteria in monoculture, especially S. pseudointermedius and P. aeruginosa. In polyculture, the 4-H₂TMeP porphyrin reduced bacterial concentrations (p < 0.05) in the associations of E. coli and S. pseudointermedius, P. aeruginosa and S. pseudointermedius, and P. aeruginosa and P. mirabilis. These results showed that aPDT using 4-H₂TMeP is a good option for future associations of aPDT and other therapies or in vivo research.

Multi-component redox system for selective and potent antineoplastic activity towards ovarian cancer cells

Ovarian cancer is the deadliest gynecological cancer which rarely causes symptoms, and goes undetected until reaching the advanced stage of drug-resistant metastases. The cationic porphyrin meso-tetra(4-N-methylpyridyl)porphine (TMPyP) is a well-known photosensitizer (PS) used in photodyamic therapy (PDT) for curing cancer due to its strong affinity for DNA and high yield of reactive oxygen species (ROS) upon light activation. The practicality to irradiate tumor cells alone in the physiological system being slim (due to the close proximity of healthy cells and tumors), we looked for a variation in the PDT using a mixture of TMPyP with 1,5-dihydroxynapthalene (DHN) and Fe(III) ions at a mole ratio of 1:20:17 (drug combo) respectively in aqueous solution. The drug combo needs no photoactivation in H₂O₂ rich environment (mimicking the microenvironment of cancer/tumor), where it generates ȮH and juglone, the latter being a known potent anticancer agent. In vitro studies of the drug combo in drug resistant and sensitive ovarian cancer cell lines showed drastic growth inhibition and cell death compared to normal epithelial cells. The drug combo provides an effective and non-invasive alternative to conventional PDT, exploiting the cytosolic carcinogenic H₂O₂ to produce an efficient anticancer treatment. The unique action of cancer-specific cytotoxicity arises from the redox chemistry involving activation of Fe(III) as the oxidizing agent to generate juglone, which utilizes the cytosolic ROS in cancer cells against itself.

Kinetics and mechanism of formation of nickel(II)porphyrin and its interaction with DNA in aqueous medium

Kinetics between 5,10,15,20-tetrakis(N-methylpyridium-4-yl)porphyrin and Ni²⁺ species were investigated in aqueous solution at 25 ±1 °C in I = 0.10 M (NaNO₃). Speciation of Ni²⁺ was done in I = 0.10 M (NaNO₃) for knowing distribution of Ni²⁺ species with solution pH. Experimental data were compared with speciation diagram constructed from the values of hydrolysis constants of Ni²⁺ ion. Speciation data showed that hexaaquanickel(II) ions took place in hydrolysis reactions through formation of [Ni(OH₂)_6-n(OH)_n]^2-n species with solution pH. According to speciation of Ni²⁺ and pH dependent rate constants, rate expression can be written as: d[Ni(TMPyP)⁴⁺]/dt = (k₁[Ni²⁺_(aq)] + k₂[Ni(OH)⁺_(aq)] + k₃[Ni(OH)₂^o_(aq)] + k₄[Ni(OH)₃^-_(aq)])[H₂TMPyP⁴⁺], where k₁, k₂, k₃ and k₄ were found to be k₁ = (0.62 ± 0.22) × 10^-2; k₂ = (3.60 ± 0.40) × 10^-2; k₃ = (2.09 ± 0.52) × 10^-2, k₄ = (0.53 ± 0.04) × 10^-2 M^-1s^-1 at 25 ±1 °C, respectively. Formation of hydrogen bonding between [Ni(H₂O)₅(OH)]⁺ and [H₂TMPyP]⁴⁺ causes enhanced reactivity. Rate of formation of [Ni(II)TMPyP]⁴⁺ complex was to be 3.99 × 10^-2 M^-1s^-1 in I = 0.10 M, NaNO₃ (25 ± 1 °C). UV-Vis and fluorescence data suggested that [Ni(II)TMPyP]⁴⁺ and [H₂(TMPyP)]⁴⁺ interact with DNA via outside binding with self-stacking and intercalation, respectively.

SYNOPSIS

Bactericidal efficiency of porphyrin systems

Photodynamic Inactivation is an innovative technique used to combat bacterial and viral infections which involves the use of photosensitizing agents along with light to generate cytotoxic reactive oxygen species able to kill bacteria and viruses. In the first section of this minireview, porphyrin-based fluorophores are shown to be remarkable dye candidates for PDI (photodynamic inactivation) applications. The second section is dedicated to the description of porphyrin-based antimicrobial materials and their potentialities for industrial applications such as in food packaging or antimicrobial medical devices and hygiene. Finally, the failings and perspectives of PDI are analyzed to demonstrate how the PDI technique could be an efficient and ecologically friendly antimicrobial technique.

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.

Effect of structural variation on tumor targeting efficacy of cationically charged porphyrin derivatives: Comparative in-vitro and in-vivo evaluation for possible potential in PET and PDT

tetracationic (TMPyP) and tricationic porphyrin (TriMPyCOOHP) derivatives were synthesized, characterized and investigated for binding with DNA by Isothermal Titration Calorimetry as well as by UV-Vis spectroscopy in order to study the effect of structural variation on tumor targeting efficacy of cationically charged porphyrin derivatives. Fluorescence cell imaging studies performed in cancer cell lines corroborated the findings of aforementioned studies. Photocytotoxicity experiments in A549 cell lines revealed relatively higher light dependent cytotoxic effects exerted by TMPyP compared to TriMPyCOOHP. In-vivo experiments in tumor bearing animal model revealed relatively longer retention of ⁶⁸Ga-TMPyP in tumorous lesion compared to that of ⁶⁸Ga-TriMPyCOOHP. The study reveals that removal of one of the positive charges of the tetracationic porphyrin derivatives significantly reduces their DNA binding ability and cytotoxicity as well as brings changes in the pharmacokinetic pattern and tumor retention in small animal model.

The application of antimicrobial photodynamic inactivation on methicillin-resistant S. aureus and ESBL-producing K. pneumoniae using porphyrin photosensitizer in combination with silver nanoparticles

As resistance of bacterial strains to antibiotics is a major problem, there is a need to look for alternative treatments. One option is antimicrobial photodynamic inactivation (aPDI). The pathogenic cells are targeted by a nontoxic photosensitizer while the surrounding healthy tissue is relatively unaffected. The photosensitizer is activated by light of t appropriate wavelength resulting in the generation of reactive oxygen species that are cytotoxic for the pathogens. In this work, the photosensitizer TMPyP and silver nanoparticles (AgNPs) were investigated for their synergistic antibacterial effect. We tested these two substances on two bacterial strains, methicillin-resistant Staphylococcus aureus 4591 (MRSA) and extended-spectrum beta-lactamases-producing Klebsiella pneumoniae 2486 (ESBL-KP), to compare their effectiveness. The bacteria were first incubated with TMPyP for 45 min or 5 h, then irradiated with a LED source with the total fluence of 10 or 20 J/cm² and then placed in a microbiological growth medium supplemented with AgNPs. To accomplish the synergistic effect, the optimal combination of TMPyP and AgNPs was estimated as 1.56-25 μM for TMPyP and 3.38 mg/l for AgNPs in case of MRSA and 1.56-50 μM for TMPyP and 3.38 mg/l for AgNPs in case of ESBL-KP at 45 min incubation with TMPyP and fluence of 10 J/cm². Longer incubation and/or longer irradiation led to a decrease in the maximum values of the photosensitizer concentration to produce the synergistic effect. From this work it can be concluded that the combination of antimicrobial photodynamic inactivation with a treatment including silver nanoparticles could be a promising approach to treat bacterial infection.

Photodynamic activity attained through the ruptured π-conjugation of pyridyl groups with a porphyrin macrocycle: synthesis and the photophysical and photobiological evaluation of 5-mono-(4-nitrophenyl)-10,15,20-tris-[4-(phenoxymethyl)pyridine]-porphyrin and its Zn(ii) complex

This article compares a reported hydrophobic and photobiologically inert porphyrin synthon, (NPh)TPyP, bearing a single meso-4-nitrophenyl group and three meso-pyridyl groups (A₃B type) with a new photobiologically active metal-free porphyrin, P₃N, and its zinc-complex, P₃NZn, which bear a meso-4-nitrophenyl group along with three distal pyridyl groups. Both P₃N and P₃NZn experience ruptured π-conjugation with the porphyrin macrocycle and attain hydrophilicity, as indicated via density functional theory (DFT) calculations, becoming photobiologically active under in vitro conditions. The non-invasive photodynamic activity (PDA) predominantly shown by the zinc-complex P₃NZn (with higher hydrophilicity) towards KRAS-mutated human lung-cancer cells (A549) was studied. The results indicate the existence of intracellular singlet oxygen inflicted anticancer PDA, which is apparent through the upregulation of intracellular reactive oxygen species (ROS) and the downregulation of both intracellular superoxide dismutase (SOD) and intracellular reduced glutathione (GSH) levels. The trends obtained from both SOD and GSH assays were indicators of therapeutic defence against oxidative stress via neutralizing superoxide anions (SOA).

Water-soluble tetra-cationic porphyrins display virucidal activity against Bovine adenovirus and Bovine alphaherpesvirus 1

Porphyrins are photoactive compounds that can absorb the energy of light and transfer it to oxygen molecules, producing reactive oxygen species (ROS). Once produced, ROS may alter biological molecules and cellular mechanisms, leading to cell apoptosis or inactivation of microorganisms, such as bacteria, fungi, and viruses. Therefore, the objective of this study was to evaluate the in vitro virucidal activity of six tetra-cationic porphyrins against two bovine viruses (Bovine alphaherpesvirus 1, BoHV-1, enveloped; and Bovine adenovirus, BAV, non-enveloped). For this, viral suspensions were incubated with each porphyrin (H₂TMeP, ZnTMeP, and CuTMeP at 4.0 μM, NiTMeP at 5.0 μM, and CoClTMeP and MnClTMeP at 1.0 μM) and exposed to white-light irradiation for 0, 60, 120, and 180 min (BAV) or 0, 30, 60, 90, and 120 min (BoHV-1). Then, the remaining viral titers were determined by limiting dilution and compared with the control (virus + porphyrins without light exposition). The porphyrins H₂TMeP and ZnTMeP showed the highest virucidal activity against both viruses. ZnTMeP inactivated BoHV-1 after 30 min of photoactivation and H₂TMeP after 60 min. The BAV was photo-inactivated by both porphyrins at 180 min of white-light exposition. CuTMeP, NiTMeP, and CoClTMeP porphyrins had weak virucidal activity against BoHV-1 and MnClTMeP showed no virucidal activity against both viruses. These results indicated that free-base H₂TMeP and ZnTMeP porphyrins present virucidal activity against non-enveloped and enveloped viruses, opening the possibility for their use to inactivate viruses on surfaces, biological substrates, and solutions.

Porphyrins as Colorimetric and Photometric Biosensors in Modern Bioanalytical Systems

Advances in porphyrin chemistry have provided novel materials and exciting technologies for bioanalysis such as colorimetric sensor array (CSA), photo-electrochemical (PEC) biosensing, and nanocomposites as peroxidase mimetics for glucose detection. This review highlights selected recent advances in the construction of supramolecular assemblies based on the porphyrin macrocycle that provide recognition of various biologically important entities through the unique porphyrin properties associated with colorimetry, spectrophotometry, and photo-electrochemistry.

Sulfobutylether-β-cyclodextrin/5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphine nanoassemblies with sustained antimicrobial phototherapeutic action

Nowadays, novel less-expensive nanoformulations for in situ-controlled and safe delivery of photosensitisers (PSs) against opportunistic pathogens in body-infections areas need to be developed. Antimicrobial photodynamic therapy (aPDT) is a promising approach to treat bacterial infections that are recalcitrant to antibiotics. In this paper, we propose the design and characterization of a novel nanophototherapeutic based on the trade cyclodextrin CAPTISOL® (sulfobutylether-beta-cyclodextrin, SBE-βCD) and 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphine tetrakis(p-toluenesulfonate) (TMPyP) to fabricate efficient biocompatible systems for aPDT. Spherical nanoassemblies of about 360 nm based on CAPTISOL®/TMPyP supramolecular complexes with 1:1 stoichiometry and apparent equilibrium binding constant (K_b ≅ 1.32 × 10⁵ M^-1) were prepared with entrapment efficiency of ≅ 100% by simple mixing in aqueous media and freeze-drying. These systems have been characterized by complementary spectroscopy and microscopy techniques. Time resolved fluorescence pointed out the strong interaction of porphyrin monomer within nanoassemblies (τ₂ ≅ 11 ns with an amount of ca 90%) and scarce self-aggregation of porphyrins have been observed. Singlet oxygen comparative determination (ϕ_{Δ CAPTISOL}®_/TMPyP = 0.58) assessed their photodynamic potential. Release and photostability studies have been carried out under physiological conditions pointing out the role of CAPTISOL® to sustain porphyrin release for more than 2 weeks and to protect PS from photodegradation. Finally, photoantimicrobial activity of nanoassemblies vs free porphyrin have been investigated against Gram-negative P. aeruginosa, E. coli and Gram-positive S. aureus. The proposed nanosystems were able to photokill both Gram-positive and -negative bacterial cells similarly to TMPyP at MBC₉₀ = 6 µM of TMPyP and at 42 J/cm² light dose. However, with respect to the less selective free TMPyP in biological sites, nanoassemblies exhibit sustained release properties and a higher photostability thus optimizing the PDT effect at the site of action. These results can open routes for in vivo translational studies on nano(photo)drugs and nanotheranostics based on less expensive formulations of CD and PS.

Excited state electron transfer in A2 and A2B2 functionalized zinc porphyrins carrying rigid and flexible β-pyrrole π-extended substituents

Optical absorption and emission, electrochemical, and photochemical properties of peripherally functionalized with flexible and rigid [Formula: see text]-extended substituents on A2 and A2B2 type zinc porphyrins is investigated. The significance of rigid [Formula: see text]-substituents over flexible ones in governing the spectral properties is unraveled. Flexible [Formula: see text]-substituents on the porphyrin ring caused appreciable spectral broadening compared to porphyrin carrying rigid [Formula: see text]-substituents. Further, supramolecular dyads are formed by coordinating phenyl imidazole functionalized fullerene, C[Formula: see text]Im. The calculated binding constants for the 1:1 complexes is in the order of 2–7 × 105 M[Formula: see text] suggesting stable complex formation. Free-energy calculations performed according to the Rehm–Weller approach suggested possibility of excited state electron transfer in these dyads. Femtosecond transient absorption studies of the dyads performed in [Formula: see text]-dichlorobenzene showed evidence of occurrence of electron transfer from the singlet-excited state that was in competition with the intersystem crossing process to populate the triplet-excited state of porphyrins.

Enhanced photodynamic therapy and fluorescence imaging using gold nanorods for porphyrin delivery in a novel in vitro squamous cell carcinoma 3D model

Nanocomposites of gold nanorods (Au NRs) with the cationic porphyrin TMPyP (5,10,15,20-tetrakis(1- methyl 4-pyridinio)porphyrin tetra(p-toluenesulfonate)) were investigated as a nanocarrier system for photodynamic therapy (PDT) and fluorescence imaging. To confer biocompatibility and facilitate the cellular uptake, the NRs were encapsulated with polyacrylic acid (PAA) and efficiently loaded with the cationic porphyrin by electrostatic interaction. The nanocomposites were tested with and without light exposure following incubation in 2D monolayer cultures and a 3D compressed collagen construct of head and neck squamous cell carcinoma (HNSCC). The results showed that Au NRs enhance the absorption and emission intensity of TMPyP and improve its photodynamic efficiency and fluorescence imaging capability in both 2D cultures and 3D cancer constructs. Au NRs are promising theranostic agents for delivery of photosensitisers for HNSCC treatment and imaging.

Synthesis, characterization and modeling of self-assembled porphyrin nanorods

Porphyrin nanorods were prepared by ion-association between free-base meso 5,10,15,20-tetrakis-(4-[Formula: see text]-methylpyridinium)porphyrin cations and tetraphenylborate anions. The nanorods have variable lengths (up to a few micrometers long) and diameters ([Formula: see text]50–500 nm). Their structure at the molecular level was elucidated by combining multinuclear solid state NMR spectroscopy, synchrotron X-ray powder diffraction and DFT calculations.

Synthesis of highly water soluble tetrabenzoporphyrins and their application toward photodynamic therapy

Novel tetraaryl-(pyridinium-4-yl)-tetrabenzoporphyrins have been successfully synthesized via a Heck-based sequence reaction. These tetrabenzoporphyrins were substituted with eight pyridyl groups at the fused benzene rings. Methylation of the pyridyl groups with methyl iodide afforded highly water soluble tetrabenzoporphyrins carrying eight ionic groups. The extended [Formula: see text]-conjugation broadened and red-shifted the absorption band of these porphyrins to 650–750 nm. These cationic tetrabenzoporphyrins showed non-toxicity in the dark up to 100 uM. High phototoxicity with IC[Formula: see text] values lower than 18 [Formula: see text]M were obtained for these tetrabenzoporphyrins.

Advances in aPDT based on the combination of a porphyrinic formulation with potassium iodide: Effectiveness on bacteria and fungi planktonic/biofilm forms and viruses

The increasing world-wide rate of antibiotic resistance as well as the capacity of microorganisms to form biofilms, have led to a higher incidence of mortal infections that require alternative methods for their control. Antimicrobial photodynamic therapy (aPDT) emerged as an effective solution against resistant strains. The present work aims to evaluate the aPDT efficiency of a photosensitizer (PS) based on a low-cost formulation constituted by five cationic porphyrins (FORM) and its potentiation effect by KI on a broad spectrum of microorganisms under white light (380–700 nm, 25 W/m[Formula: see text]. The aPDT assays were performed with different concentrations of FORM (0.1 to 5.0 [Formula: see text]M) and 100 mM of KI on planktonic and biofilm forms of gram-positive (methicillin resistant Staphylococcus aureus–MRSA) and gram-negative (Escherichia coli resistant to chloramphenicol and ampicillin) bacteria, of the fungi Candida albicans and on a T4-like bacteriophage as a mammalian virus model. The results indicate that the FORM alone is an efficient PS to photoinactivate not only gram-negative and gram-positive bacteria, but also C. albicans, in planktonic and biofilm forms, and T4-like phage at low concentrations (<5.0 [Formula: see text]M). The presence of KI enhanced the photodynamic effect of this FORM for all microorganisms on the planktonic form, allowing the reduction of PS concentration and treatment time. The results also show that the combination FORM/KI is highly efficient in the elimination of already well-established biofilms of E. coli,S. aureus and C. albicans. This effect is probably associated with longer-lived iodine reactive species produced during the aPDT treatment.