Violacein/poly(ϵ-caprolactone)/chitosan nanoparticles against bovine mastistis: Antibacterial and ecotoxicity evaluation

Abstract

The nanocarrier was synthesized by nanoprecipitation, using poly(-caprolactone) (PCL) as polymer, Tween 80 as surfactant and the biopolymer chitosan (CS) as a charge modification agent. Charge, size and morphology were analyzed by zeta potential, photo correlation spectroscopy (PCS), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Bactericidal assays were carried out using a resistant strain of Staphylococcus aureus, and the acute ecotoxicity tests were performed with Daphnia similis. The nanoparticle without CS (PCLnp) exhibited an average size of 200 nm and zeta potential of −4.28 mV, while the nanoparticle with 0.04% (w/v) of CS (CS_PCLnp) had 250 nm and +21.3 mV. Both were stables for at least 30 days. 200 μg mL−1 violacein was encapsulated in CS_PCLnp, which was dissolved in the polymer matrix, a shown by DSC analysis. The minimal inhibitory concentration against S. aureus of CS_PCLnp-vio was 25 μmol L−1, while for free violacein it was > 25 μmol L−1. Nanoparticles exhibited an EC50 between 0.3 – 1.1 μmol L−1 with Daphnia, while free violacein was around 3.3 – 5.0 μmol L−1. Thus, it was possible to control the charge of the nanoparticles, without extreme changes in size and that it is possible also to encapsulate a powerful antibactericidal compound such as violacein in nanoparticle.