Photothermal Stimuli-Responsive Hydrogel Containing Safranine for Mastitis Treatment in Veterinary Using Phototherapy

Abstract

Safranine-O (Sf) is a photosensitizer (PS) displaying a remarkable potential for photodynamic therapy (PDT). In this work, we have used the combination of Sf with F127 Pluronic and Carbopol (C934P) to obtain a stimuli-responsive hydrogel (SR-Sf). This thermoresponsive-photoactive nanostructured system was prepared by two different methods: direct addition (DA) and solid dispersion (SD). Both SR-Sf have had their physical and chemical properties evaluated for veterinary applications, especially considering their ability to be used as a commercial product, aiming at the prophylactic or therapeutic treatment of breast gland infections. In general, the rheological and mechanical properties, as well as the sol–gel transition temperature, indicated suitable properties for using them as a topical system in veterinary (and human) applications. The ex vivo release studies showed a satisfactory permeation profile of the SR-Sf hydrogel, reaching the full length of the overall skin toward the dermis within 30 min of application (989 μm). The in vitro studies showed photodynamic inactivation using Sf-F127 with a significant reduction in isolated colonies. The in vivo case report with dairy goat demonstrated that the SR-Sf hydrogel veterinary use platform emerged as an innovative approach for the treatment of local infections without generating antibiotic residues in the milk produced.