New AB3-type porphyrins with piperidine and morpholine motifs; synthesis and photo-physicochemical and biological properties

In this study, new unsymmetrical meso-tetraaryl AB₃-type porphyrins 1 and 2 were successfully synthesized by the reaction of p-bromobenzaldehyde and p-hydroxybenzaldehyde with pyrrole in propionic acid. AB₃-type porphyrin building blocks with hydroxyl functionality (1 and 2) were further used to generate both covalently linked metal free and Zn(II) porphyrins 3-6 having piperidine and morpholine heterocyclic units. These novel compounds were characterized by using ¹H NMR, ¹³C NMR, FT-IR and MALDI-TOF spectrophotometry. The photophysical and photochemical properties of compounds 1-6 were investigated by employing UV-vis absorption and fluorescence emission spectroscopy in tetrahydrofuran (THF). From the view of biological properties, the antioxidant capacities of porphyrins were determined by using DPPH radical scavenging activity and 2 was determined as the most potent porphyrin analog with a value of 98.42% at 200 mg L^-1. All the targeted compounds displayed significant DNA nuclease activity. In addition, the antimicrobial potential of compounds 1-6 was also investigated by a micro-dilution process and 2 was found to be the most effective candidate against the tested microbial strains. The newly synthesized porphyrins also showed 100% microbial cell viability inhibition against E. coli at all examined concentrations. In terms of biofilm inhibition activity, the best results for the maximum photodynamic antimicrobial biofilm inhibition of S. aureus and P. aeruginosa were obtained by compound 2 with the values of 99.75% and 93.39%, respectively.

Novel meso-substituted porphyrin derivatives and its potential use in photodynamic therapy of cancer

Background

Photodynamic therapy (PDT) is an anticancer treatment that utilizes the interaction of light and a photosensitiser (PS), promoting tumour cell death mediated by generation of reactive oxygen species. In this study, we evaluated the in vitro photoactivity of four meso-substituted porphyrins and a porphyrin coupled to a fullerene.

Methods

The cell line employed was the LM3 mammary adenocarcinoma, and the PS with the best photokilling activity was administered to mice bearing the LM3 subcutaneously implanted adenocarcinoma. The TEMCP⁴⁺ porphyrin and its analogue TEMCC⁴⁺ chlorine contain four identical carbazoyl substituents at the meso positions of the tetrapyrrolic macrocycle and have A₄ symmetry. The TAPP derivative also has A₄ symmetry, and it is substituted at the meso positions by aminopropoxy groups. The DAPP molecule has ABAB symmetry with aminopropoxy and the trifluoromethyl substituents in trans positions. The TCP-C₆₀⁴⁺ dyad is formed by a porphyrin unit covalently attached to the fullerene C₆₀.

Results

The PSs are taken up by the cells with the following efficiency: TAPP> TEMCP⁴⁺ = TEMCC⁴⁺ > DAPP >TCP-C₆₀⁴⁺, and the amount of intracellular PS correlates fairly with the photodamage degree, but also the quantum yields of singlet oxygen influence the PDT outcome. TAPP, DAPP, TEMCC⁴⁺ and TEMCP⁴⁺ exhibit high photoactivity against LM3 mammary carcinoma cells, being TAPP the most active. After topical application of TAPP on the skin of mice bearing LM3 tumours, the molecule is localized mainly in the stratum corneum, and at a lower extent in hair follicles and sebaceous glands. Systemic administration of TAPP produces a tumour: normal skin ratio of 31.4, and high accumulation in intestine and lung.

Conclusion

The results suggest a potential use of topical TAPP for the treatment of actinic keratosis and skin adnexal neoplasms. In addition, selectivity for tumour tissue after systemic administration highlights the selectivity of and potentiality of TAPP as a new PS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08286-6.

Photophysical and Antibacterial Properties of Porphyrins Encapsulated inside Acetylated Lignin Nanoparticles

Lignin has recently attracted the attention of the scientific community, as a suitable raw material for biomedical applications. In this work, acetylated lignin was used to encapsulate five different porphyrins, aiming to preserve their photophysical properties, and for further use as antibacterial treatment. The obtained nanoparticles were physically characterized, through dynamic light scattering size measurement, polydispersity index and zeta potential values. Additionally, the photophysical properties of the nanoparticles, namely UV-vis absorption, fluorescence emission, singlet oxygen production and photobleaching, were compared with those of the free porphyrins. It was found that all the porphyrins were susceptible to encapsulation, with an observed decrease in their fluorescence quantum yield and singlet oxygen production. These nanoparticles were able to exert an effective photodynamic bactericide effect (blue-LED light, 450-460 nm, 15 J/cm2) on Staphylococcus aureus and Escherichia coli. Furthermore, it was achieved a photodynamic bactericidal activity on an encapsulated lipophillic porphyrin, where the free porphyrin failed to diminish the bacterial survival. In this work it was demonstrated that acetylated lignin encapsulation works as a universal, cheap and green material for the delivery of porphyrins, while preserving their photophysical properties.

Mechanistic aspects in the photodynamic inactivation of Candida albicans sensitized by a dimethylaminopropoxy porphyrin and its equivalent with cationic intrinsic charges

Photocytotoxic effect induced by 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (TAPP) and 5,10,15,20-tetrakis[4-(3-N,N,N-trimethylaminepropoxy)phenyl]porphyrin (TAPP⁺⁴) was examined in Candida albicans to obtain information on the mechanism of photodynamic action and cell damage. For this purpose, the photokilling of the yeast was investigated under anoxic conditions and cell suspensions in D₂O. Moreover, photoinactivation of C. albicans was evaluated in presence of reactive oxygen species scavengers, such as sodium azide and d-mannitol. The results indicated that singlet molecular oxygen was the main reactive species involved in cell damage. On the other hand, the binding and distribution of these porphyrins in the cells was observed by fluorescence microscopy. Morphological damage was studied by transmission electron microscopy (TEM), indicating modifications in the cell envelopment. Furthermore, deformed cells were observed after photoinactivation of C. albicans by toluidine blue staining. In addition, modifications in the cell envelope due to the photodynamic activity was found by scanning electron microscopy (SEM). Similar photodamage was observed with both porphyrin, which mainly produced alterations in the cell barriers that lead to the photoinactivation of C. albicans.

Porphyrins containing basic aliphatic amino groups as potential broad-spectrum antimicrobial agents

New porphyrin derivatives bearing basic aliphatic amino groups were synthesized from the condensation of meso-4-[(3-N,N-dimethylaminopropoxy)phenyl]dipyrromethane, pentafluorobenzaldehyde and 4-(3-N,N-dimethylaminopropoxy)benzaldehyde. The reaction was catalyzed by trifluoroacetic acid in acetonitrile. This approach was used to obtain porphyrins with different patterns of substitution, of which three of them were isolated: 5,15-di(4-pentafluorophenyl)-10,20-di[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (F₁₀APP), 5-(4-pentafluorophenyl)-10,15,20-tris[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (F₅APP) and 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (TAPP). The UV-vis spectroscopic characterizations and the photodynamic effect of these compounds were compared in N,N-dimethylformamide. These porphyrins showed red fluorescence emission with quantum yields of 0.09-0.15. Moreover, they sensitized the production of singlet molecular oxygen, reaching quantum yields values of 0.33-0.53. Photodynamic inactivation was studied in two bacteria, Staphylococcus aureus and Escherichia coli, and a yeast Candida albicans. High amount of cell-bound porphyrin was obtained at short times (<2 min) of incubation. After 15 min irradiation, a 7 log reduction of S. aureus was found for cells treated with 1 μM F₅APP. Similar photokilling was obtained in E. coli, but using 7.5 μM F₅APP and 30 min irradiation. Under these conditions, a decrease of 5 log was observed in C. albicans cells. An increase in cell survival was observed by addition of sodium azide, whereas a slight protective effect was found in the presence of D-mannitol. Moreover, the photoinactivation mediated by these porphyrins was higher in D₂O than in water. Thus, these porphyrins induced the photodynamic activity mainly through the intermediacy of O₂(¹Δ_g). In particular, F₅APP was a highly effective photosensitizer with application as a broad-spectrum antimicrobial. This porphyrin contains three basic aliphatic amino groups that may be protonated at physiological pH. In addition, it is substituted by a lipophilic pentafluorophenyl group, which confers an amphiphilic character to the tetrapyrrolic macrocycle. This effect can increase the interaction with the cell envelopment, improving the photocytotoxic activity against the microorganisms.

Synthesis and properties of 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl] chlorin as potential broad-spectrum antimicrobial photosensitizers

A novel 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]chlorin (TAPC) was synthesized by reduction of the corresponding porphyrin TAPP with p-toluenesulfonhydrazide, followed by selective oxidation with o-chloranil. Spectroscopic properties and the photodynamic activity of these photosensitizers were compared in N,N-dimethylformamide. An increase in the absorption band at 650nm was found for the chlorin derivative with respect to TAPP. These photosensitizers emit red fluorescence with quantum yields of 0.15. Both compounds were able to photosensitize singlet molecular oxygen with quantum yields of about 0.5. Also, the formation of superoxide anion radical was detected in the presence of TAPC or TAPP and NADH. Photodynamic inactivation was investigated on a Gram-positive bacterium Staphylococcus aureus, a Gram-negative bacterium Escherichia coli and a fungal yeast Candida albicans cells. In vitro experiments showed that TAPC or TAPP were rapidly bound to microbial cells at short incubation periods. These photosensitizers, without intrinsic positive charges, contain four basic amino groups. These substituents can be protonated at physiological pH, increasing the interaction with the cell envelopment. Photosensitized inactivation improved with an increase of both photosensitizer concentrations and irradiation times. After 15min irradiation, a 7 log reduction of S. aureus was found for treated with 1μM photosensitizer. Similar result was obtained with E. coli after using 5μM photosensitizer and 30min irradiation. Also, the last conditions produced a decrease of 5 log in C. albicans cells. Therefore, TAPC was highly effective as a broad-spectrum antimicrobial photosensitizer.

Photodynamic inactivation of Candida albicans by a tetracationic tentacle porphyrin and its analogue without intrinsic charges in presence of fluconazole

The photodynamic inactivation mediated by 5,10,15,20-tetrakis[4-(3-N,N-dimethylaminopropoxy)phenyl]porphyrin (TAPP) and 5,10,15,20-tetrakis[4-(3-N,N,N-trimethylaminepropoxy)phenyl]porphyrin (TAPP(4+)) were compared in Candida albicans cells. A strong binding affinity was found between these porphyrins and the yeast cells. Photosensitized inactivation of C. albicans increased with both photosensitizer concentration and irradiation time. After 30 min irradiation, a high photoinactivation (∼5 log) was found for C. albicans treated with 5 μM porphyrin. Also, the photoinactivation of yeast cells was still elevated after two washing steps. However, the photocytotoxicity decreases with an increase in the cell density from 10(6) to 10(8) cells/mL. The high photodynamic activity of these porphyrins was also established by growth delay experiments. This C. albicans strain was susceptible to fluconazole with a MIC of 1.0 μg/mL. The effect of photosensitization and the action of fluconazole were combined to eradicate C. albicans. After a PDI treatment with 1 μM porphyrin and 30 min irradiation, the value of MIC decreased to 0.25 μg/mL. In addition, a complete arrest in cell growth was found by combining both effects. TAPP was similarly effective to photoinactivate C. albicans than TAPP(4+). This porphyrin without intrinsic positive charges contains basic amino groups, which can be protonated at physiological pH. Moreover, an enhancement in the antifungal action was found using both therapies because lower doses of the agents were required to achieve cell death.

Selective photodynamic therapy based on aggregation-induced emission enhancement of fluorescent organic nanoparticles

Three binary molecule conjugates were designed and synthesized by conjugating a chromophore (3, 6-bis-(1-methyl-4-vinylpyridinium)-carbazole diiodide, BMVC) to mono-, bis- and trishydroxyl photosensitizers, respectively. BMVC plays the role of cancer cells recognizer; AIEE (aggregation-induced emission enhancement) generator and FRET (Fluorescence Resonance Energy Transfer) donor. The self assembling properties of these binary conjugates result in different degrees of AIEE and then achieve the formations of FONs (fluorescent organic nanoparticles), which present efficient FRET and singlet oxygen generations. Biologically, FONs-photosensitizers from these compounds were much more phototoxicities to cancer cell than to normal cell without significant dark toxicity. In addition, their intracellular fluorescent colors switching upon photo-excitation are expected to be used for further cell death biomarker applications. This improved photodynamic activity might be due to the aggregation of compounds in the cell that form FONs which can promote PDT (photodynamic therapy) and are observed in cancer cell but not normal cell.

Mechanisms of Escherichia coli photodynamic inactivation by an amphiphilic tricationic porphyrin and 5,10,15,20-tetra(4-N,N,N-trimethylammoniumphenyl) porphyrin

The mechanistic aspects of Escherichia coli photodynamic inactivation (PDI) have been investigated in bacteria treated with 5,10,15-tris[4-(3-N,N,N-trimethylammoniumpropoxy)phenyl]-20-(4-trifluoromethylphenyl)porphyrin iodide (A3B3+) and visible light. The photosensitization activity of A3B3+ porphyrin was compared with that of 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin p-tosylate (TMAP4+), which is an active tetracationic sensitizer to eradicate bacteria. The PDI damages on plasmid and genomic DNA were analyzed by electrophoresis. DNA photocleavage was observed after a long period of irradiation, when the bacterial cells are largely photoinactivated. Transmission electron microscopy (TEM) revealed structural changes with appearance of low density areas into the cells and irregularities in cell barriers, which could affect the normal cell membrane functionality. Also, damages on the cell-wall were not detected by scanning electron microscopy (SEM) and release of intracellular biopolymers was not found after PDI. These results indicate that the photodynamic activity of these cationic porphyrins produces DNA photodamage after a long period of irradiation. Therefore, an interference with membrane functions could be the main cause of E. coli photoinactivation upon short PDI treatments.

Photodynamic Therapy: Porphyrins and Phthalocyanines as Photosensitizers

The present work is focussed on the principles of photodynamic therapy (PDT), emphasizing the photochemical mechanisms of reactive oxygen species formation and the consequent biochemical processes generated by the action of reactive oxygen species on various biological macromolecules and organelles. This paper also presents some of the most used photosensitizers, including Photofrin, and the new prototypes of photosensitizers, analysing their physicochemical and spectroscopic properties. At this point, the review discusses the therapeutic window of absorption of specific wavelengths involving first- and second-generation photosensitizers, as well as the principal light sources used in PDT. Additionally, the aggregation process, which consists in a phenomenon common to several photosensitizers, is studied. J-aggregates and H-aggregates are discussed, along with their spectroscopic effects. Most photosensitizers have a significant hydrophobic character; thus, the study of the types of aggregation in aqueous solvent is very relevant. Important aspects of the coordination chemistry of metalloporphyrins and metallophthalocyanines used as photosensitizers are also discussed. The state-of-the-art in PDT is evaluated, discussing recent articles in this area. Furthermore, macrocyclic photosensitizers, such as porphyrins and phthalocyanines, are specifically described. The present review is an important contribution, because PDT is one of the most auspicious advances in the therapy against cancer and other non-malignant diseases.

Photodynamic therapy in the treatment of microbial infections: basic principles and perspective applications

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) appears to be endowed with several favorable features for the treatment of infections originated by microbial pathogens, including a broad spectrum of action, the efficient inactivation of antibiotic-resistant strains, the low mutagenic potential, and the lack of selection of photoresistant microbial cells. Therefore, intensive studies are being pursued in order to define the scope and field of application of this approach.

RESULTS

Optimal cytocidal activity against a large variety of bacterial, fungal, and protozoan pathogens has been found to be typical of photosensitizers that are positively charged at physiological pH values (e.g., for the presence of quaternarized amino groups or the association with polylysine moieties) and are characterized by a moderate hydrophobicity (n-octanol/water partition coefficient around 10). These photosensitizers in a micromolar concentration can induce a >4-5 log decrease in the microbial population after incubation times as short as 5-10 minutes and irradiation under mild experimental conditions, such as fluence-rates around 50 mW/cm2 and irradiation times shorter than 15 minutes.

CONCLUSIONS

PDT appears to represent an efficacious alternative modality for the treatment of localized microbial infections through the in situ application of the photosensitizer followed by irradiation of the photosensitizer-loaded infected area. Proposed clinical fields of interest of antimicrobial PDT include the treatment of chronic ulcers, infected burns, acne vulgaris, and a variety of oral infections.

Photodynamic inactivation of Escherichia coli immobilized on agar surfaces by a tricationic porphyrin

The photodynamic activity of 5,10,15-tris[4-(3-N,N,N-trimethylammoniumpropoxy)phenyl]-20-(4-trifluoromethylphenyl)porphyrin iodide (A3B3+) has been studied in vitro on a typical Gram-negative bacterium Escherichia coli immobilized on agar surfaces. The results obtained for the tricationic A3B3+ porphyrin were compared with those of 5,10,15,20-tetra(4-N,N,N-trimethylammoniumphenyl)porphyrin p-tosylate (TTAP4+), which is a standard active sensitizer established to eradicate E. coli in cellular suspension. The photobleaching of these porphyrins in solution was evaluated by decay in absorbance and in fluorescence. In both cases, a higher photostability was found for A3B3+ than for TTAP4+. Photodynamic inactivation capacities of these sensitizers were analyzed in E. coli cells immobilized on agar surfaces. Small colonies were treated with different amount of sensitizer (0-14 nmol) and irradiated with visible light for 3h. The light source used was either a projector or midday sun. The A3B3+ porphyrin produced a growth delay of E. coli colonies on agar surfaces. Similar result was obtained irradiating only one isolated colony through an optical fiber. Under these conditions, A3B3+ porphyrin shows a high activity to inactivate localized bacterial cells. The higher photodynamic activity of A3B3+ was confirmed by mechanical spreading of the colonies before treatment. This procedure produces complete inactivation of E. coli cells on the agar surface. Therefore, tricationic A3B3+ porphyrin is an interesting sensitizer with potential applications in photodynamic inactivation of bacteria growing as localized foci of infection.

Photodynamic inactivation of Escherichia coli by novel meso-substituted porphyrins by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl and 4-(trifluoromethyl)phenyl groups

The photodynamic effect of novel cationic porphyrins, with different pattern of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, have been studied in both solution bearing photooxidizable substrates and in vitro on a typical Gram-negative bacterium Escherichia coli. In these sensitizers, the cationic groups are separated from the macrocycle ring by a propoxy spacer. Thus, the charges have a high mobility and a minimal influence on photophysical properties of the porphyrin. These compounds produce singlet molecular oxygen, O2(1Delta(g)), with quantum yields of approximately 0.41-0.53 in N,N-dimethylformamide. In methanol, the l-tryptophan photodecomposition increases with the number of cationic charges in the sensitizer. In vitro investigations show that cationic porphyrins are rapidly bound to E. coli cells in approximately 5 min. A higher binding was found for A3B3+ porphyrin, which is tightly bound to cells still after three washing steps. Photosensitized inactivation of E. coli cellular suspensions follows the order: A3B3+ > A44+>> ABAB2+ > AB3+. Under these conditions, a negligible effect was found for 5,10,15,20-tetra(4-sulfonatophenyl)porphyrin (TPPS4(4-)) that characterizes an anionic sensitizer. Also, the results obtained for these new cationic porphyrins were compared with those of 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin (TTAP4+), which is a standard active sensitizer established to eradicate E. coli. The photodynamic activity of TTAP4+ is quite similar to that produced by A4(4+). Studies in an anoxic condition indicate that oxygen is necessary for the mechanism of action of photodynamic inactivation of bacteria. The higher photodynamic activity of A3B3+ was confirmed by growth delay experiments. Photodynamic inactivation capacities of these sensitizers were also evaluated in E. coli cells immobilized on agar surfaces. Under these conditions, A3B3+ porphyrin retains a high activity to inactivate localized bacterial cells. Therefore, tricationic porphyrin A3B3+ is an interesting sensitizer with potential applications in photodynamic inactivation of bacteria in liquid suspensions or on surfaces.