Papers by Author: Karen A. Hing

Abstract: The success or failure of a bioactive ceramic implant material in the body depends on a complex interaction between a synthetic foreign body and the host. These interactions occur at many levels from the nano-structural level, where subtle changes in surface physio-chemistry substantially alters the nature of the biomaterial-host tissue interface, to the meso- or macrostructural level where dependence on porosity mediates bioactivity through its effect on nutrient transfer and scaffold mechanics. Thus the factors that control the biological response to implant materials are a complex combination of mechanical, physical and chemical attributes which when combined favorably lead to ‘bioactivity’ in a material, or more correctly a ‘bioactive’ response to the material. This is illustrated in the successful use of porous bioactive ceramic scaffolds as synthetic bone graft substitute materials, where micro and meso-porosity, bulk and surface chemistry are manipulated to provide a framework that is highly conducive to the process of bone regeneration, balancing bone apposition and remodeling. Moreover, we now have the opportunity to developing an understanding of the complex balance of forces at play during bone grafting through investigation of these biological responses.

Abstract: In this study silicon release from SiHA into tissue culture medium was investigated under static and semi-dynamic conditions. The effect of silicon release under semi-dynamic conditions on alkaline phosphatase activity (ALP) and collagen I (CICP) expression by osteoblast like cells (HOS TE85) was also examined. Under static conditions a low level of silicon was released within 24 hours, this initial level dropped over 3-7 days but subsequently increased again by 10-14 days. Under semi-dynamic conditions silicon was released within 24 hours and was subsequently reduced with each medium change until equilibrating at close to 0 after 10 days. ALP and CICP showed significant variation in expression between culture conditions. In direct contact with SiHA ALP peaked at day 10 and CICP was constantly elevated. Cells grown in the presence of but not on SiHA expressed progressively decreasing levels of ALP from 7-14 days, with CICP peaking at day 10. On thermanox (TMX) ALP constantly increased and CICP peaked at day 10. The results indicate that silicon leaches out of the lattice of the SiHA crystal structure but may also be reprecipitated onto the substrate. We have also demonstrated that Si influences osteoblast metabolism and differentiation whether it is available as free silicon or 'bound' in the apatite lattice.