Morphology of sol–gel derived nano-coated coralline hydroxyapatite

Abstract

Current bone graft materials are mainly produced from coralline hydroxyapatite (HAp). Due to the nature of the conversion process, commercial coralline HAp has retained coral or CaCO 3, and the structure possesses nanopores within the inter-pore trabeculae, resulting in high dissolution rates. Under certain conditions these features reduce durability and strength and are not utilised where high structural strength is required. To overcome these limitations, a new coral double-conversion technique has been developed. The technique involves a two-stage application route where, in the first stage, complete conversion of coral to pure HAp is achieved. In the second, a new sol–gel-derived HAp nano-coating is directly applied to cover the micro- and nano-pores within the intra-pore material, whilst maintaining the large pores. Biaxial strength was improved two-fold due to this unique double treatment. This application is expected to result in enhanced durability and longevity due to the monophasic hydroxyapatite structure and strength in the physiological environment. It is anticipated that this new material can be applied to load-bearing bone graft applications where high strength requirements are pertinent.