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

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.

Evaluation of Eosin-Methylene Blue as a Photosensitizer for Larval Control of Aedes aegypti by a Photodynamic Process

Aedes aegypti (Ae. aegypti) is a competent vector for transmitting important viral diseases such as yellow fever, dengue, chikungunya, and Zika. Several strategies have been applied to avoid Ae. aegypti proliferation by using environmental management, biological, and chemical approaches. However, the development of new methods for effective control of the insect vector population is still needed. Photodynamic control is an alternative way to control the vector population by using a physical approach based on the larval phototoxicity of a photosensitizer. In this context, the present study evaluated the use of eosin-methylene blue (EMB) as a new photosensitizer for photodynamic control of Ae. aegypti larval populations. The photodynamic assays were performed submitting Ae. aegypti third-instar larvae to different EMB concentrations (0.0, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 µg mL−1) in combination of three different light doses (24.3, 48.6, and 97.2 J cm−2) under either white-light radiation from RGB LEDs or sunlight. The results demonstrated that EMB presented a rapid internalization into the larvae and was phototoxic. The photodynamic action induced 100% of larval mortality after about 40 min of sunlight irradiation even using low EMB concentration (0.5 µg mL−1). The findings reveal EMB as an effective photoactive compound to control larval populations of Ae. aegypti by photodynamic process induced by either sunlight or white-light from RGB LEDs.