Sistema híbrido macroporoso para enxertos ósseos aloplásticos

Abstract

In medicine and dentistry, there is an increasing need for new biomaterials that can gain predictable and controlled tissue responses. For instance, biomaterials serving, as bone graft substitutes should initiate new bone formation, after which they should get resorbed and replaced by bone tissue. A variety of synthetic bone grafts from composites based on biodegradable polymers and hydroxyapatite (HA) has been the subject of considerable scientific and clinical interest. The biodegradable polymer/ceramics composites have gained acceptance in dentistry and medicine for repairing bone and periodontal defects with advantages relatively to autografts and allografts such as unlimited supply, low cost and absence of immunugenicity. In experimental studies hydroxyapatite (HA) have shown excellent bone forming and mineralizing properties, but their application into periodontal tissue defects has been difficult. The use of biodegradable polymers such as aliphatic polyesters to obtain homogeneous injectable composite materials has become a common practice in medicine field. Poly(ε-caprolactone) (PCL) has been used in several medical applications, but as such they do not enhance the bone tissue regeneration. The main objective of this work was to develop and to test novel biologically active composites based on hydroxyapatite (HA) and macroporous PCL:I2 with potential for use in bone repair. The monomer ε-caprolactone (ε-CL) was polymerized in bulk in the presence of HA using I2 as a catalyst to form a macroporous polyester (PCL) having a weight-average molecular weight (Mw) of 32,900 g.mol-1. The PCL:I2/HA composite had macropore structure and pore sizes that are closely controlled during the ring-opening polymerization of ε-caprolactone monomer. The PCL:I2/HA composite was sterilized by gamma rays from a 60Co source at 25 kGy and their osteoinductive property was evaluated after implantation in the rabbit tibia. Quantitative data for histomorphometric evaluation was collected with microscopic observation on the stained bone sections and computational vision analysis. The in vitro citotoxicity to CHO cells based on cell viability with Chinese hamster ovary cells (CHO) and antimicrobial activities against xiv Escherichia coli and Staphylococcus aureus were examined. The tested PCL:I2/HA composite showed better antimicrobial activity against E. coli than against S. aureus. The newly developed HA ceramic with macroporous PCL:I2 improves bone tissue recolonization after 20 days of implantation. The histological analysis after PCL:I2/HA implantation revealed an osteoinductive material that supported bone cell growth suggesting a potentially bioactive composite.