Biocompósitos de quitosana e derivados/nanohidroxiapatita reticulados com epicloridrina e dopados com zinco para potencial aplicação em engenharia tecidual

Abstract

Biomaterials based on calcium phosphate represent a promising alternative in tissue regeneration. Placement of membrane-shaped biomaterials on the periodontal defects prevents the bone regeneration and repair process from being harmed by the proliferation of epithelial cells from the gum tissue, allowing osteoprogenitor cells to increase and differentiate within the isolated area. The present study reports the synthesis of biocomposites based on polymeric matrices of chitosan (QUI), O-carboxymethyl chitosan (CMQ) or glycol chitosan (GLI-Q) with nanoparticles of hydroxyapatite (nHA) synthesized in aqueous route chemically modified with epichlorohydrin (ECH) and doped with Zn2+. The structure, morphology and crystallinity of the components and biocomposites modified were extensively characterized. In vitro swelling and degradation assays were performed. Viability and cellular activity tests were performed with different cell lines, using 3-4,5-dimethyl-thiazol-2-il]-2,5-diphenyltetrazolium bromide, assay of Alkaline Phosphatase Activity and LIVE/DEAD. In vivo experiment allowed analysis of the effect of the biocomposites in the bone repair in rats tibia. Results showed that the binders used during the synthesis played an important role on the mechanisms of nucleation kinetics and growth of HA particles at nanometer scale. Differences in the size of nHA produced without binder were observed, with QUI, CMQ and GLI-Q with average sizes of 335±70nm, 220±50nm, 90±20nm and 74±15nm, respectively. Analysis through FTIR and XRD indicated that hydroxyapatite was the predominant phase of calcium phosphate produced. Crosslinking with ECH was detected by significant differences observed by FTIR, identifying a decrease of the band in 1.030cm-¹ attributed to the C6-OH type stretching and by the significant decrease in swelling and solubilization of the crosslinked biocomposites. Biocomposites crosslinked with ECH and doped with Zn²+ presented satisfactory results in the cytotoxicity and cellular viability assays. In the in vivo assay, biocomposites increased the bone formation in the defects after 7 days of insertion, emphasizing the biocomposites crosslinked with 10% of ECH and doped with Zn²+. Results showed that the biocomposites presented promising characteristics for applications in bone tissue engineering