Bioceramics and Biocomposites from Marine Sources

Abstract

Advanced technologies and biocomplexity offer new dimensions for the development of novel medical products obtained from marine resources. Because several biomaterials can be derived from synthetic or natural sources, this area offers a very large variety of natural species that may be used for biomedical applications, including tissue engineering, drug delivery and surgery. The marine environment is a natural collector of porous materials the porosity of which varies from submicron to millimeter. The production of hydroxyapatite from synthetic chemicals can sometimes lead to a costly work and sea creatures may represent an alternative way to produce very fine and even nano-structured biomaterials. Rapana venosa is, in this sense, a study marine organism because its shell is made of aragonite that can be converted into bioceramic powder, which can subsequently be used for biomedical applications. The indirect use of marine organisms was tackled according to different routes: synthetic precursor casts using biomorphic moulds, chemical conversion of the inorganic marine matrix into a biomorphic substitute, and self-assembly of nanoparticles via chemical and molecular interactions. The chemical conversion is the most developed practice to obtain biomaterials for bone regeneration. It can be realized by hydrothermal synthesis or hydrothermal hot pressing. Both methods suppose a pre-treatment to remove the organic matrix of the skeleton. Hydrothermal synthesis involves heating the marine skeletons under alkaline conditions at a specific temperature pressure in either a reaction vessel or an autoclave. The temperature and pressure have an important significance concerning material structure properties of final product in terms of degree of crystallinity, grain size, and specific surface area. The temperature has an importance on the crystallite size (50-150 nm), and in general, the optimal temperature ranges between 200-250°C. Hydrothermal hot pressing is the process used in the fabrication of some commercial bone substitutes from coral sources and involves the solidification of synthetic hydroxyapatite powder. Some experimental results related to the processing of Rapana venosa snail shell in order to obtain hydroxyapatite for medical applications are presented at the end. In conclusion, preliminary results obtained by us show that this snail shell appears to be suitable to be used as raw material for obtaining hydroxyapatite.