Chitosan-based silver nanoparticles: A study of the antibacterial, antileishmanial and cytotoxic effects

Silver nanoparticles have been studied as an alternative for treatment of microbial infections and leishmaniasis, without promoting induction of microbial or parasite resistance. In this study, chitosan-based silver nanoparticles were synthesized from silver nitrate (AgNO ₃ ), sodium borohydride as a reducing agent, and the biopolymer chitosan as a capping agent. The chitosan-based silver nanoparticles were characterized by ultraviolet–visible, Fourier transform infrared, dynamic light scattering, zeta potential, atomic force microscopy, and transmission electron microscope. The antibacterial assay was performed by determination of the minimum inhibitory concentration. The antileishmanial and the cytotoxic effects induced by AgNO ₃ , chitosan, and chitosan-based silver nanoparticles were analyzed by resazurin and MTT colorimetric assays, respectively. AgNO ₃ , chitosan, and chitosan-based silver nanoparticles induced a marked activity against all bacterial strains and promastigote forms of Leishmania amazonensis at minimum inhibitory concentrations ranging from 1.69 to 3.38 µg Ag/mL. Interestingly, the chitosan-based silver nanoparticles presented less cytotoxicity than the AgNO ₃ alone and were more active against L. amazonensis than solely chitosan. Furthermore, the cytotoxic concentrations (CC ₅₀ ) of both chitosan and chitosan-based silver nanoparticles against macrophages were significantly higher than the IC ₅₀ against promastigotes. Thus, the chitosan-based silver nanoparticles represent a promising alternative for the treatment of microbial infections and leishmaniasis.