Liposomes as drug delivery systems for photoinactivation of methicillin-resistant Staphylococcus aureus (MRSA)

MIRETTI MARIANA; GONZÁLEZ GRAGLIA M. ANTONELLA; GUALDESI M. SOLEDAD; VARA JIMENA; BAUMGARTNER M.

Congreso; LI Reunión Anual de la Sociedad Argentina de Biofísica.; 2023

Staphylococcus aureus (S. aureus) is part of the normal microbiota; it can cause infections ranging from superficial skin and localized abscesses to severe infections such as osteomyelitis, endocarditis, and other life-threatening diseases. Methicillin-resistant S. aureus (MRSA) is resistant to many antibiotics such as methicillin, penicillin, cefazolin, cefoxitin, and other common antibiotics. [1]Antimicrobial photodynamic therapy (aPDT) has emerged over the last decade as an alternative to eliminate pathogens, principally those antimicrobials resistant. The aPDT involves a photosensitizer (PS) (innocuous in the darkness), light, and oxygen. The excitation of PS leads to the generation of singlet oxygen and other reactive oxygen species (ROS) capable of reacting with biomolecules, producing cell damage and microbial inactivation.[2] Among PS, phthalocyanines (Pcs) are considered excellent PS. However, the efficiency of Pcs in aqueous media decreases due to their lipophilic nature and limited solubility in water, leading to aggregates forming. Incorporating Pcs in delivery systems such as liposomes (LP) improves solubility and reduces aggregation. LP are vesicles biocompatible and biodegradable, constituted by phospholipid bilayers surrounding an aqueous compartment. Thus, hydrophobic PSs can be entrapped in the center of phospholipid bilayers.[3] In this work, aPDT was applied using Zn(II) phthalocyanine (ZnPc) loaded into liposomes against MRSA. LP are composed of DPPC and cholesterol. LP mean size of control and loaded with ZnPc was ~130 nm. In the dark, the MRSA viability was not affected. As expected, control liposomes did not show activity against MRSA successfully. ZnPc free was not effective in eliminating MRSA. Indeed, liposomes loaded with ZnPc photoinactivated MRSA. Thus, combining DPPC-col liposomes with ZnPc allows photoinactivating MRSA.