Synthesis and Characterization of Biopolymer/HA Nanocomposites for Biomedical Applications

Abstract

The idea of starting this research project was to elucidate the development procedure of a novel biocompatible nano composite that is directly linked to the properties of natural bone in terms of its composition, morphology, mechanical properties and biocompatibility. These nanocomposites are composed of hydroxyapatite (HA) and whitlockite (WH) nanoparticles embedded in polymeric matrix and hydrogels. The fabrication procedures used are of common use including pre-treatment of nanoparticles and embedding into biopolymers such as Cyclic olefenic copolymer and Collagen-PEGDMA hybrid matrix where effect of different loading ratios of HA nanoparticles and WH nanoparticles was investigated. Nano powders of HA were chemically synthesized under various processing conditions using surfactants with different charges and chain lengths such as CTAB (cationic) and SDS (anionic) surfactants were used in the synthesis procedures for regulating the nucleation and growth of the hydroxyapatite phase. The synthesis methods, mainly based on aqueous systems were used which are simple and can offer accurate control on the nano powders of various size and morphologies. The effect of different weight ratios of HA nanoparticles and WH was evaluated after successful fabrication of nanocomposites by dispersing these nanoparticles in polymeric matrices. TOPAS/HA, TOPAS/WH and Collagen-PEGDMA/HA nanocomposites were successfully prepared and further characterized. Solution casting procedure was used to construct these nano composites. Effect of various weight ratios was investigated on physical, chemical and mechanical properties of the nano composites. These nano composites were characterized through Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Compression testing, Biocompatibility testing including cell culture of bone/cartilage cell lines, antibacterial test, biodegradability, and swelling characteristics. The morphology of nanocomposites has been investigated using Scanning electron microscopy and Atomic force microscopy. Compression testing was performed on all type of nanocomposites to evaluate and optimize the mechanical strength. Cell culture was performed to evaluate the biocompatibility of these nanocomposites on bone cell lines in case of TOPAS/HA and TOPAS/WH while cartilage cell lines were used in the case of COl-PGD/HA nanocomposites. Swelling and degradation characteristics were also evaluated. It was revealed from this study thet the compressive strengths of nano composites can be enhanced with the addition of nanoparticles and optimized to make values comparable with the compressive strength of natural bone and cartilage tissues. In case of TOPAS/HA the increased values are 185 % from 0.26 to 0.74 MPa at the concentration of 10 wt%. Whearas in case of PGD-16/HA, up to 10 wt%, strength is enhanced ~ 90 % from 9 to 17.3 kPa. In case of TOPAS/WH increase of 0.2MPa to 1.7MPa in strength at lower concentration of WH upto 10wt% has been experimented. The biocompatibility data of cell viability on the whole, is above 90% in all nanocomposites and the values are even higher than 95%. In TOPAS/HA (10 wt%) exhibits the highest trend for cell viability of 99.9 ± , while in case of PGD-16/HA (10 wt%) the cell viability of hybrid composites is 100 % as compared to the TCP control group while the cell viability values are around 95-100% in case of TOPAS/WH (10wt%). These results make these nanocomposites suitable for biomedical applications.