Preparation, physico-chemical and biological in vitro evaluation of bovine pericardium combined with silk fibroin/chitosan via freeze-drying and irradiation

Author(s)

Roberta Polak

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2010-06-24

Examining board members

Ronaldo Nogueira de Moraes Pitombo; Olga Zazuco Higa; Bronislaw Polakiewicz

• Advisor: Ronaldo Nogueira de Moraes Pitombo

Abstract

In this work, electron beam irradiation was studied as a crosslinker of bovine pericardium tissue (BP). The treatment of BP with chitosan and silk fibroin was also the goal of this study. Samples of BP were freeze-dried and irradiated in an electron beam accelerator using different doses and dose rates. Samples were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Raman spectroscopy, water uptake tests, scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile tests and evaluation as biofunctionality. After analysis, it was concluded that irradiation of the tissue in the absence of oxygen promotes crosslinking of collagen fibers. On the other hand, in the presence of oxygen the chain scission of the collagen fibers was observed, and both samples suffered a decrease in their mechanical properties. It was also concluded that irradiation, both in the absence or presence of oxygen, promotes the adhesion and proliferation of endothelial cells throughout the tissue. In the second part of this work, lyophilized BP were incorporated into chitosan, silk fibroin solutions and mixtures of chitosan/silk fibroin in the ratio of 1:3, 1:1, 3:1. Then, the samples were again lyophilized and submitted to irradiation. These samples were characterized by Raman spectroscopy, and tested for their cytotoxicity, biofunctionality, and calcification. After washing the biomaterial with aqueous solution (NaCl 0.9%), the samples did not show cytotoxicity. Biofunctionality test showed that PQSFI samples (all proportions) promoted the adhesion and growth of endothelial cells. All samples induced calcification, but they exhibited a Ca/P ratio lower than hydroxyapatite. (AU)