Herein, we report on the antimicrobial photodynamic effect of polymeric nanoparticles containing the endogenous photosensitizer protoporphyrin IX. Compared to equivalent doses of the free photosensitizer, we demonstrated that the photodynamic antimicrobial efficacy of PLGA (polylactic-co-glycolic acid) nanoparticles containing protoporphyrin IX (PpIX) against pathogenic Staphylococcus aureus (S. aureus) is preserved after encapsulation, while photobleaching is reduced. In addition, compared to equivalent doses of the free porphyrin, we show that a reduction in the cytotoxicity in mammalian cell cultures is observed when encapsulated. Therefore, the encapsulation of protoporphyrin IX reduces its photodegradation, while the released photosensitizer maintains its ability to generate reactive oxygen species upon light irradiation. The polymeric nanoencapsulation promotes aqueous solubility for the hydrophobic PpIX, improves its photostability and reduces the cytotoxicity, while providing an extended release of this endogenous photosensitizer.

1. Despite all the awareness campaigns and the active recommended reduction in antibiotic prescriptions and use, antimicrobial resistance remains in the top ten global public health threats for man...

Catechol moieties have been covalently coupled to the last-resort polypeptide antibiotic colistin via esterification and amidation reactions, inspired by the superior antimicrobial action of cefiderocol, i.e., a catechol-substituted siderophore cephalosporin. Among the tested strategies, the incorporation of the catechol motif by amidation reduces by 50% the minimum concentration to inhibit the growth of a clinical strain of uropathogenic Escherichia coli (E. coli) in its planktonic form. Its minimum bactericidal concentration is reduced by 25% after chemical modification. The tested modified antibiotic did not show cytotoxicity against human fibroblasts and keratinocytes at bactericidal doses. Additionally, due to the potential nephrotoxicity of colistin, the cytotoxicity of this catechol-substituted siderophore colistin was evaluated in a 3D model of human renal organoids showing no cytotoxicity at the doses tested. The chemical incorporation of catechol groups to existing antibiotics can reduce the doses to exert a fast antimicrobial action reducing the chances to develop antibiotic resistance.