Bodipy-Loaded Micelles Based on Polylactide as Surface Coating for Photodynamic Control of Staphylococcus aureus

Enrico Caruso,Chiara Scanferla,Lorella Izzo,Miryam Chiara Malacarne,Giovanni Vigliotta,Daniela Pappalardo,Viviana Teresa Orlandi,Eleonora Martegani

doi:10.3390/coatings11020223

Enrico Caruso, Chiara Scanferla + Show 6 more

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https://doi.org/10.3390/coatings11020223

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Abstract

Decontaminating coating systems (DCSs) represent a challenge against pathogenic bacteria that may colonize hospital surfaces, causing several important infections. In this respect, surface coatings comprising photosensitizers (PSs) are promising but still controversial for several limitations. PSs act through a mechanism of antimicrobial photodynamic inactivation (aPDI) due to formation of reactive oxygen species (ROS) after light irradiation. However, ROS are partially deactivated during their diffusion through a coating matrix; moreover, coatings should allow oxygen penetration that in contact with the activated PS would generate 1O2, an active specie against bacteria. In the attempt to circumvent such constraints, we report a spray DCS made of micelles loaded with a PS belonging to the BODIPY family (2,6-diiodo-1,3,5,7-tetramethyl-8-(2,6-dichlorophenyl)-4,4′-difluoroboradiazaindacene) that is released in a controlled manner and then activated outside the coating. For this aim, we synthesized several amphiphilic copolymers (mPEG–(PLA)n), which form micelles, and established the most stable supramolecular system in terms of critical micelle concentration (CMC) and ∆Gf values. We found that micelles obtained from mPEG–(PLLA)2 were the most thermodynamically stable and able to release BODIPY in a relatively short period of time (about 80% in 6 h). Interestingly, the BODIPY released showed excellent activity against Staphylococcus aureus even at micromolar concentrations.

Highlights

One of the route of pathogen dissemination is via contaminated surfaces, as most bacteria can survive for a long time even on the surface of objects
Nosocomial infections generated by contaminated surfaces are a great concern because common disinfectants used in routine cleansing are generally based on quaternary ammonium compounds (QACs), halogen releasing agents, and phenolics, in some cases resulting in ineffective killing of pathogenic bacteria, as their activity depends on several factors, including the surface contact period, pH, temperature, and amount and nature of the microorganism [1]
We synthesized several linear and branched block copolymers of general structure ABn (n = 1, 2, 4), where A is the poly(ethylene glycol)monomethylether and B represents the poly(lactide) (PLA) blocks, either atactic poly D,L-lactide (PD,LLA) or stereoregular polyL-lactide (PLLA) (Figure 1). mPEG–(PLA)n linear and branched copolymers were synthesized following a procedure already reported by some of us [19] and with the rationale of obtaining a similar molecular weight for the hydrophobic and hydrophilic part of the copolymer to foster the formation of micelles by copolymer self-assembling in water

Summary

Introduction

One of the route of pathogen dissemination is via contaminated surfaces, as most bacteria can survive for a long time even on the surface of objects. Nosocomial infections generated by contaminated surfaces are a great concern because common disinfectants used in routine cleansing are generally based on quaternary ammonium compounds (QACs), halogen releasing agents, and phenolics, in some cases resulting in ineffective killing of pathogenic bacteria, as their activity depends on several factors, including the surface contact period, pH, temperature, and amount and nature of the microorganism [1]. In the past two decades, to obtain decontamination systems, different antimicrobial substances have been incorporated in the bulk or in the coating of biomaterials. An excessive use of antibiotics leads to the development of antibioticresistant pathogens and could causes environmental contamination [3]

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