S. Narayana Kalkura, Crystal Growth Centre, Anna University, Chennai-60025
E-mail: kalkura@yahoo.com/kalkurasn@annauniv.edu
Common degradable and non-degradable implant materials can be divided into synthetically produced metals and metal alloys, ceramics, polymers, and composites or modified natural materials. Whereas non-resorbable materials like steel or titanium alloys are commonly used for prosthetic devices. Resorbable bone substitute materials are mainly investigated for their feasibility in bone replacement therapies.. Whether or not a material is biodegradable, its surface properties will influence the initial cellular events at the cell-material interface. Study of finding a substitution for the bone parts and repairing seriously damaged portions of the human body is a challenging area of multidisciplinary research.
The nano-scale changes in surface like grain size distribution, charge distribution is known to influence the biological performance of the biomaterial. Further, the porosities produced would help in the flow body fluids, bone tissue growth coupled with good biocompatibility. Hydroxyapatite (HAp, Ca10(PO4)6(OH)2), a bioceramic is the main constituent of the bones and teeth of vertebrates as well as almost all hard tissues of humans.. It has been widely used to reconstruct or substitute spoiled bone tissues. It has poor mechanical strength that limits its application in the load bearing areas and its low reactivity, leads to slow integration with bone. When applied as coating on metallic surfaces the dissolution rate in the body environment is high that results in the disappearance of the coating at an early stage after implantation. Conventional high temperature sintering of HAp may reduce its reactivity and also result in the conversion to its α-phase and calcium oxide, which is undesirable as it increases the dissolution rate in vivo. To tolerate the corrosive environment of the human body and to control the dissolution rate, surface modifications of the implant materials is being employed. The ion beam irradiation or implantation enables modification of the chemistry of the bioceramics in a reproducible way so as to optimize the bone response to the implant and improve biointeraction.
Synthesis of nano-HAp by various routes such as microwave, hydrothermal and sol-gel, will be discussed. The method of preparation of the samples influenced the bioactivity in a significant way The nitrogen implantation significantly enhanced permittivity, ac conductivity, photoluminescence and pore size. In addition, discussion on the irradiation studies using swift heavy ions on HAp will be presented. The surface was modified in most of the cases leading to considerable changes in surface properties. The ion implantation/irradiation could be used to modify the surface and tailor the properties to fabricate multifunctional materials.
