Graduate Research
Drug release kinetics from hydroxyapatite polymer composites
    One of the most exciting and rewarding research areas of materials science involves the applications of materials to health care, especially to reconstructive surgery. The importance of biomaterials can be well realized from an economical aspect, that is, in terms of an estimate of total health care expenditure around the world. It was also reported that the United States total health care expenditure for the year 2000 was approximately 14 billion US dollars. Out of this, 9 billion US dollars was for biomaterials. With continuous changes in lifestyle as well as with increasing life expectancy, the requirement of biomaterials increases day by day in both developed and developing nations, than at the beginning of this century. Therefore, the development of biomaterials and related devices is important.

    The field of biomaterials is multidisciplinary, and the design of biomaterials requires the synergistic interaction of materials science, biological science, chemical science, medical science and mechanical science.

    Calcium phosphates, especially hydroxyapatite (HAp) and tricalcium phosphate (TCP), have been extensively used in bone tissue engineering due to their morphological similarity with the natural bone and their excellent biocompatibility and bioactivity. Porous scaffolds made of them have been used as candidates for their stimulation of bone formation and bone bonding. Their compositional resemblance induces biological response similar to those during natural bone remodelling. 

    Sustained and controlled release of any drug over desired period of time from implant material is an important factor for effective osteogenesis. Therefore, any burst release of drug is not desired in achieving this goal. Bioactive and biodegradable polymer coating over CaP ceramic scaffolds is an approach to prevent the burst release.

    In this study, the effects of pH, concentration and polymer interaction with drugs were studied. The study aims to develop controlled and sustained release kinetics of the drug from the polymer coatings on the calcium phosphates. The study aims to investigate the rimary factor involved in controlling the release kinetics from these samples.

Drug release kinetics and enhanced osteointegration from surface modified metal implants
    In modern history, metals have been used as implants since more than 100 years ago when Lane first introduced metal plate for bone fracture fixation in 1895 (Lane, W.A. Some remarks on the treatment of fractures. Brith Med J , 1895,1, 861). In the early development, metal implants faced corrosion and insufficient strength problems. Shortly after the introduction of the 18-8 stainless steel in 1920s, which has had far-superior corrosion resistance to anything in that time, it immediately attracted the interest of the clinicians. Thereafter, metal implants experienced vast development and clinical use.

    Among different metallic biomaterials, titanium and its alloy exhibit most suitable features for biomedical implants. Its density is only 4.5g/cm3 compared to 7.9g/cm3 for 316 stainless steel and 8.3g/cm3 for cast CoCrMo alloys. Titanium alloys, in particular Ti-6Al-4V, are widely used as bone substitutes for orthopedic applications under load bearing conditions, such as hip joint replacement and dental roots, due to their biocompatibility, good corrosion resistance and mechanical properties. In addition, currently, functionalities such as superelasticity and shape memory characteristics are also required for titanium alloys used in biomedical applications. Titanium alloyed with Ni, i.e. Nitinol, forms alloys having shape memory effect which makes them suitable in various applications such as dental restoration wiring.

    The bulk properties of biomaterials, such as non-toxicity, corrosion resistance or controlled degradability, modulus of elasticity, and fatigue strength have long been recognized to be highly relevant in terms of the selection of the right biomaterials for a specific biomedical application. In case of implantation, interaction between the biological environment and artificial material surfaces plays an extremely important role. In general, surface modification to titanium medical devices are carried out to develop specific surface properties that are suitable for the particular biological environment without changing the bulk properties of the metal.

    This study aims to investigate the various types of coating on the titanium alloys with hydroxyapatite and different polymers and provide a comparative data them to lead to a sustained drug release kinetics and also develop a multifunctional device towards load bearing applications. The study also aims to show enhanced osteointegration with the surface modification of the load implants made from titanium alloys.