Hydroxyapatite (HA) was coated onto pure magnesium (Mg) with an MgF(2) interlayer in order to reduce the surface corrosion rate and enhance the biocompatibility. Both MgF(2) and HA were successfully coated in sequence with good adhesion properties using the fluoride conversion coating and aerosol deposition techniques, respectively. In a simulated body fluid (SBF), the double layer coating remarkably enhanced the corrosion resistance of the coated Mg specimen. The in vitro cellular responses of the MC3T3-E1 pre-osteoblasts were examined using a cell proliferation assay and an alkaline phosphatase (ALP) assay, and these results demonstrated that the double coating layer also enhanced cell proliferation and differentiation levels. In the in vivo study, the HA/MgF(2) coated Mg corroded less than the bare Mg and had a higher bone-to-implant contact (BIC) ratio in the cortical bone area of the rabbit femora 4 weeks after implantation. These in vitro and in vivo results suggested that the HA coated Mg with the MgF(2) interlayer could be used as a potential candidate for biodegradable implant materials.

SYNOPSISTo improve the physical properties of starch-filled polyolefin, starch was modified into more hydrophobic material by the introduction of cholesterol unit, and the different starchcompositioned high-density polyethylene (HDPE) films were prepared with addition of either native starch or modified starch to compare their physical properties. The addition of either native starch or modified starch resulted in decreased crystallinities in all the different composite films containing starch. Interestingly, HDPE-blown films containing more than 10% native starch (HDPE/ST) showed a steeper decrease in crystallinity than correspondent HDPE containing the modified starch (HDPE/MS). Improvement of the dispersion and adhesion in HDPE/MS and HDPE/ST were also observed; but at high starch content, the HDPE/MS films showed higher tensile strength and elongation than the HDPE/ST. The degradation of HDPE/MS films in active sludge condition was much faster than that of the HDPE/ST films, although the degradation rate of HDPE/MS films in a-amylase condition were slower than the one of HDPE/ST films. 0 1996 John Wiley & Sons, Inc.