The Nano-hydroxyapatite/polyamide (n-HA/PA) composite can be used for tissue engineering and bone repair or substitute. This biocomposite is prepared by co-solution, co-precipitation method and water treatment under normal atmospheric pressure. The n-HA crystals uniformly distribute in the composite with a crystal size of 10-20 nm in diameter by 70-90 nm in length. The nHA/PA composite has good homogeneity, high n-HA content (65 wt %), and high bioactivity. Strong molecule interactions and chemical bonding are present between the n-HA and PA in the composite, which are verified by Infra red, X-ray photo-electronic spectroscopy and X-ray diffraction. The composite has excellent mechanical properties close to the natural bone. An n-HA/PA composite scaffold was made by utilizing thermally induced phase inversion processing technique. medical economic
The macrostructure and morphology as well as mechanical strength of the scaffolds were characterized. Mesenchymal stem cells (MSCs) derived from bone marrow of neonatal rabbits were cultured, expanded and seeded on n-HA/PA scaffolds. The MSC/scaffold constructs were cultured for up to 7 days and the adhesion, proliferation and differentiation of MSCs into osteoblastic phenotype were determined using MTT assay, alkaline phosphates (ALP) activity and collagen type I immunohistochemical staining and SEM. The results confirm that n-HA/PA scaffolds are biocompatible and have no negative effects on the MSCs in vitro. To investigate the in vivo biocompatibility and osteogenesis of the composite scaffolds, both pure n-HA/PA scaffolds and MSC/scaffold constructs were implanted in rabbit mandibles and studied histologically and microradiographically. The results show that n-HA/PA composite scaffolds exhibit good biocompatibility and extensive osteoconductivity with host bone. Moreover, the introduction of MSCs to the scaffolds dramatically enhanced the efficiency of new bone formation, especially at the initial stage after implantation. In long term (more than 12 weeks implantation), however, the pure scaffolds show as good biocompatibility and osteogenesis as the hybrid ones. All these results indicate that the scaffolds fulfill the basic requirements of bone tissue engineering scaffold, and have the potential to be applied in orthopedic, reconstructive and maxillofacial surgery.
The use of composite materials for biomedical applications offers many new options and possibilities for implants design with wide range of mechanical and biological properties. The implant structure and its interactions with the surrounding tissues can be optimized by varying the constituents, the type and distribution of the reinforcing phase and adding coupling agents. In many biomedical applications, the research and the testing of composites has been introduced and highly developed. The use of these materials requires a complete understanding of the objectives and limitations involved. The major critical issues which need further research and experimentations are summarized as follows:
1. There are not enough reliable experiments supporting the long-term performance of composites with respect to traditional materials, e.g. there are no adequate standards for the assessment of composites fatigue performance.
2. The design of composite materials and components is far more complex than that of conventional monolithic materials. There are no satisfactory standards yet for the testing of the biocompatibility of composite implants because the ways in which the different components of a composite material interact to control the overall response to an implant are not completely understood.
3. The available fabrication methods may limit the possible reinforcement configurations, may be time consuming, expensive, highly skilled and may require special cleaning and sterilization processes.