Changes in the Activity of Osteoblast Like Cells with Sol - Gel Derived Hydroxyapatite and Zirconia Nanocoatings

When producing implant materials, achievement of optimal bioactivity and biocompatibility are essential. Nanocoatings can provide an efficient cost effective way to alter the interactions of the implant material with its destined "host" environment. Nanocoatings of sol-gel derived carbonated hydroxyapatite (HAp) and zirconia were produced in this study. The surfaces were characterised by Fourier transform infrared spectroscopy (FTIR) and light microscopy. Cell adhesion, proliferation and viability, as well as expression of alkaline phosphatase (ALP is an indicator of bone formation) were assessed as indicators of biocompatibility. Our results have shown that sol-gel derived nano crystalline HAp acts as an ideal surface for implant coatings. Introduction Implant materials are being increasingly designed to provide optimal pore structure for osteointegration, and a subsequent increase in the bone to implant bond [1]. Increases in the bioactivity have been achieved by the creation of micro and nano-textured surfaces. While these provide a surface conducive to bone ingrowth, the material used needs more study with regard to the effect on cell activity and the changes which occur to intracellular processes in the presence of these implant materials. This work reports a series of characterisation studies to observe the changes occurring to 2 osteoblast cell lines (Mg63 and Saos-2) when cultured on sol-gel derived nanocoated surfaces, which can be used as implant coatings. Sol-gel coating is described as any chemical procedure capable of producing ceramic oxides, nonoxides and mixed oxides from solutions. The advantages of the sol-gel technique are numerous. It results in a stoichiometric, homogeneous and pure coating due to mixing on the molecular scale; reduced firing temperatures due to small particle sizes with high surface areas; it has the ability to produce uniform fine-grained structures; the use of different chemical routes (alkoxide or aqueousbased); and their ease of application to complex shapes with a range of coating techniques: dip, spin, and spray coating. Materials and Methods Preparation and Characterisation of Coated Surfaces. Glass cover slips are spin with an alkoxide-derived sol-gel carbonate hydroxyapatite (CHAp), and sol gel-zirconia oxide solutions followed by firing to 550°C [2]. Characterisation of the surfaces is conducted using light microscopy as well as Fourier transform infrared spectroscopy (FTIR) All FTIR data has been obtained using a Nicolet magna IRE 760, measurements were conducted using diffuse powder reflectance, with a KBr reference. Thickness of the coatings is dependent on the number of layers and is varied between 70 300nm. Osteoblast Cell Culturing and Bio-Assays. Human osteosarcoma cell lines Mg63 and Saos-2 (ATCC, USA) were plated onto coated glass coverslips as well as uncoated glass coverslip as a control. The control coverslips are also fired to remove variations between samples due to possible bioactivity changes of the glass with firing. After plating onto the surfaces, Mg63 and Saos-2 cells were grown at intervals of 1, 3, 5, and 7 days, in Eagles Minimum Essential Media (Sigma) with