Nanopartículas de prata sintetizadas através de méis de abelha sem ferrão (Melipona compressipes manaosensis) no reparo tecidual de feridas cutâneas infectadas em ratos wistar (Rattus novergicus albinus)

Abstract

When infected, skin wounds delay the healing process, becoming a public health problem. Stingless bee honey (SWB) has several therapeutic and curative purposes, mainly as an antimicrobial and healing agent, and silver nanoparticles (AgNPs) have been used. The objective of this research was to evaluate the tissue repair process of skin wounds infected with Staphylococcus aureus in an in vivo assay through the application of AgNPs synthesized from SWB honeys. Thirty-five samples of SWB honeys from rural producers in the state of Amazonas were used. These samples underwent physicochemical and biochemical analyses and evaluation of antibacterial activity using the well diffusion assay and Minimum Inhibitory Concentration (MIC) against strains of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Of the 35 samples, two samples named JUP1 and JUP2 from the bee species Melipona compressipes manaosensis that had the best antibacterial activities were selected for the synthesis of AgNPs. These AgNPs were characterized by dynamic light scattering (DLS), Zeta Potential (ZP), Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). Subsequently, the toxicity test of the synthesized AgNPs was performed by means of the in vivo dermal toxicity test. In addition, the in vitro ocular irritation toxicity test was performed. After performing the biosafety tests, the in vivo healing test was started with 60 rats of the species Rattus novergicus albinus that had skin wounds infected with Staphylococcus aureus that were evaluated for 7 and 14 days. After that, macroscopic and microscopic analyses of the wounds were performed according to the date of euthanasia of the animals. The results of the physicochemical and biochemical analysis of the honeys showed variations among the samples since the botanical origin, storage conditions, geographic location and others influence the quality of the honeys. The synthesis of AgNPs of the samples JUP1 and JUP2 was verified by the color change in the colloidal suspensions at concentrations of 3 and 5 mM at 80 ºC and confirmed from the absorption bands in the UV/Vis spectra that were 400 and 800 nm. In addition, similarities were observed between the diameters, surface charges and geometric shapes of the AgNPs. While in the FTIR spectrum of the chemical groups, the presence of phenolic compounds present in the honeys and that were capable of reducing and stabilizing the Ag+ ions is suggested. The acute dermal toxicity test did not show any signs of erythema/scabs or edema in the animals treated with AgNPs JUP1 and JUP2 during the 14 days of observation, and no signs of irritation were observed in the in vitro ocular toxicity test. In the in vivo microbiological analysis, there was variability in the S. aureus count between the groups. The wounds treated with AgNPs JUP1 and JUP2 did not show any evolution in perimeter when compared to those of the negative control group (NaCl 0.9%) and honey from sample JUP1, however, they had the greatest wound contractions in relation to the positive control group (neomycin sulfate) and honey from sample JUP2 on the 3rd and 7th day. In the analysis of fibroblasts, vascular density and collagen fibers, the majority of AgNP samples presented results similar to those described for the negative control group, but when visualizing the alignment of collagen fibers, there was greater parallelism of the collagen fibers of the groups treated with AgNP solutions, honey and positive control. Thus, this study contributes to the tissue repair of infected wounds with the therapeutic use of AgNPs, although healing is a complex mechanism.