New Materials Based on Cationic Porphyrins Conjugated to Chitosan or Titanium Dioxide: Synthesis, Characterization and Antimicrobial Efficacy

Abstract

The post-functionalization of 5,10,15-tris(1-methylpyridinium-4-yl)-20-(pentafluorophenyl)porphyrin tri-iodide, known as a highly efficient photosensitizer (PS) for antimicrobial photodynamic therapy (aPDT), in the presence of 3- or 4-mercaptobenzoic acid, afforded two new tricationic porphyrins with adequate carboxylic pending groups to be immobilized on chitosan or titanium oxide. The structural characterization of the newly obtained materials confirmed the success of the porphyrin immobilization on the solid supports. The photophysical properties and the antimicrobial photodynamic efficacy of the non-immobilized porphyrins and of the new conjugates were evaluated. The results showed that the position of the carboxyl group in the mercapto units or the absence of these substituents in the porphyrin core could modulate the action of the photosensitizer towards the bioluminescent Gram-negative Escherichia coli bacterium. The antimicrobial activity was also influenced by the interaction between the photosensitizer and the type of support (chitosan or titanium dioxide). The new cationic porphyrins and some of the materials were shown to be very stable in PBS and effective in the photoinactivation of E. coli bacterium. The physicochemical properties of TiO2 allowed the interaction of the PS with its surface, increasing the absorption profile of TiO2, which enables the use of visible light, inactivating the bacteria more efficiently than the corresponding PS immobilized on chitosan.

Antimicrobial Photodynamic Therapy in the Control of COVID-19

“…The promising results of aPDT on inactivation of viruses, namely against those with an envelope, like the coronaviruses [29,33], accompanied by the possibility to immobilize easily prepared PSs on insoluble inert materials such as nano/microparticles, films and polymers [28,31,[93][94][95][96] suggest that this principle can be applied to wastewater treatment to inactivate microorganisms, including SARS-CoV-2. According to the literature, different PSs already proved to be effective to photoinactivate microorganisms, including viruses, in samples of secondary-treated wastewater [97][98][99].…”

Protonation of meso-Tetraphenylporphyrin and Its β-Functionalized Derivatives by Photogenerators of Acidity in Toluene and Polymer Film

“…[32,33] In addition, results of this study are of interest for biochemical applications, since protonated forms of porphyrins are widely studied in antibacterial photodynamic therapy. [34][35][36]…”

Porphyrin as Diagnostic and Therapeutic Agent

“…Some studies have aimed at addressing these short-comings, but to date there is no clinical evidence (which would allow for aPDT as primary treatment modality) and there is no certainty that re-growth following aPDT will not occur. Moreover, there are limited reports on the efficacy of porphyrin conjugated systems on multi-resistant microbial strains [62,63,64].…”