New Cationic Liposomes as Vehicles of m-Tetrahydroxyphenylchlorin in Photodynamic Therapy of Infectious Diseases

Abstract

Antimicrobial photodynamic therapy is emerging as a promising therapeutic modality for bacterial infections. For optimizing the antibacterial activity of the photosensitizer m-tetrahydroxyphenylchlorin, it has been encapsulated in mixed cationic liposomes composed of different ratios of dimyristoyl- sn-glycero-phosphatidylcholine and any of four cationic surfactants derived from l-prolinol. The delivery efficiency of the different liposomes formulations has been evaluated on a methicillin-resistant Staphylococcus aureus bacterial strain (MRSA), and one of the tested formulations shows a biological activity comparable to that of the free chlorin. In order to rationalize the physicochemical parameters of the carriers that control the biological activity, the new liposome formulations have been characterized by measuring (a) the zeta potential, (b) their capability of chlorin entrapping efficiency, i.e. entrapment efficacy, (c) the effect of storage on chlorin entrapment and (d) the localization of chlorin in the bilayer. The correlation of the physicochemical and biological features of formulations has allowed us to rationalize, to some extent, some of the parameters that may control the interactions with the biological environment.

Olive Oil-Based Delivery of Photosensitizers for Bacterial Eradication

“…Liposome or micelle-entrapped hematoporphyrin and chlorin e6 were found to be effective against several Gram-positive bacteria, including methicillin-resistant S. aureus (Tsai et al, 2009 Encapsulation of photosensitizers into liposomes does not always result in enhancement compared to the free-form cytotoxic activity. The activity of m-tetrahydroxyphenylchlorin in liposomal form was comparable to the free form activity of PACT inactivation of a methicillin-resistant S. aureus strain (Bombelli et al, 2008). When tested against methicillinresistant S. aureus, chlorophyll a was reported to be more efficient in free form than in a liposomal formulation, whereas hematoporphyrin as well as a positively charged PS 5-[4-(1-dodecanoylpyridinium)]-10,15,20-triphenyl-porphyrin were less effective in free form than upon encapsulation in liposomes.…”

Hypericin- and mTHPC-mediated photodynamic therapy for the treatment of cariogenic bacteria

“…While the vast majority of reports concern its high efficiency to destroy cancer cells [24], effects on bacteria are anecdotal and only include successful treatment of methicillin-resistant Staphylococcus aureus with a liposomal mTHPC formulation [25].…”

Can Nanotechnology Shine a New Light on Antimicrobial Photodynamic Therapies?

“…For example, their zeta potential is a determinant parameter influencing their aggregation. It has been showed that values close to zero induce their aggregation, thereby reducing the antimicrobial activity [53], on the contrary if these values are too high (>40 Mv), dark toxicity is present [54], whereas negative potentials result in repulsion between bacterial cells and nanoparticles. An important parameter is the surface charge of liposomes [55].…”