Biossíntese e investigação in vitro e ex vivo de nanopartículas de prata sobre enterococcus faecalis

Abstract

Enterococcus faecalis plays an important role in persistent endodontic infections, contributing to its high resistance to calcium hydroxide (Ca(OH)2), the main intracanal drug in dentistry. Thus, the development of new antimicrobial formulations is of fundamental importance, nanomaterials containing silver have been standing out and biogenic synthesis presents itself as an alternative to reducing the toxicity of nanoparticles (NPs). The aim of this research was to synthesize silver NPs with red propolis from Alagoas (NPsAg-PV) to evaluate their antibacterial potential against E. faecalis. NPsAg-PV were synthesized by the reduction of silver salts by hydroalcoholic extract of red propolis from Alagoas (EHPV), characterized in the form of colloidal suspension by ultraviolet and visible spectrophotometry (UV-Vis), dynamic light scattering (EDL) technique and zeta potential. The colloid was subjected to centrifugation and taken to an oven to obtain the NPs in powder form. The antimicrobial activity against E. faecalis was observed by the determination of MIC and MBC performed by microdilution in broth. Were evaluated Ca(OH)2; EHPV; silver nanoparticles (NPsAg), synthesized by the chemical method; NPsAg+EHPV; NPsAg-PV and the combinations Ca(OH)2+EHPV; Ca(OH)2+NPsAg; Ca(OH)2+NPsAg+EHPV and Ca(OH)2+NPsAg-PV. Following the ex vivo evaluation of substances for experimental periods of 1, 3 and 7 days on biofilm formed for 21 days in dentin of extracted human teeth. Spectral analysis showed absorbance of 425 and 421 nm, after 24 h and 72 h, respectively, characteristic values of the formation of spherical silver NPs. The EDL showed a diameter of 132.5 nm ± 1.19 and a polydispersion index (PDI) of 0.266, suggesting the homogeneity in the distribution of NPs in terms of diameter, the zeta potential was -61 mV ± 1.59, indicating the stability of the silver colloid, regarding the tendency to agglomeration. In vitro, compared to Ca(OH)2 paste, the NPsAg-PV isolated exhibited 16 times the bacteriostatic effect and 32 times the bactericidal effect, the NPsAg-PV associated with Ca(OH)2 bacteriostatic activity 2 times higher. The ex vivo assay demonstrated the effectiveness of the substances at 2,000 μg/mL on E. faecalis biofilm, observing CFUs only for NPsAg within one day. Therefore, it is possible to affirm that the red propolis from Alagoas used as a stabilizing and coating agent for silver NPs contributed to the improvement of its antimicrobial activity.