Papers by Keyword: Calcium Deficient Apatite

Abstract: Damages to articular cartilage that are caused by trauma, age-related diseases (arthritis, arthrosis) and/or physical stress pose major medical problems. A possible solution is to introduce a biodegradable sponge-like scaffold containing cartilage-forming cells. In the current work we developed a model for a partially calcified functional biomedical membrane with a gradient of calcium phosphate crystal density to form the interface between bone and a sponge-like cell containing scaffold for cartilage regeneration. The membrane consists of a biocompatible, biodegradable, partially calcified hydrogel, in our case gelatin was used. One part is an organic-inorganic nanocomposite consisting of nanocrystalline calcium phosphate particles, formed in situ within the hydrogel, while the other part is the hydrogel without inorganic crystals. The experimental method used was one-dimensional single diffusion. Gelatin gels containing calcium or phosphate ions, respectively, were exposed from the upper side to a solution of the other constituent ion (i.e. a sodium phosphate solution was allowed to diffuse into a calcium containing gel and vice versa). Scanning electron microscopy (E-SEM), EDX, XRD and ATR-FTIR spectroscopy confirmed the existence within the gel of a density gradient of carbonate apatite crystals, with a dense top layer extending several microns into the gel. Ca/P atomic ratios were in the range characteristic of calcium deficient apatites. The effect of different experimental parameters on the calcification process within the gelatin membranes is discussed.

Abstract: Calcium-deficient hydroxylapatite (CDHA) powders with Ca/P ratios from1.5 to 1.67 were synthesized by wet-chemical method. Rietveld structure refinement was performed on the X-ray diffraction data and Fourier transform infrared spectroscopy was used to characterize molecular and crystal structure of CDHA. With the decrease of Ca/P ratio, the crystallite size and crystallinity decreased, but the acid phosphate content and amount of vacancies in hydroxyapatite hexagonal structure increased. The disorder of CDHA structure increase indicated calcium-deficiency and HPO4 replacement resulted in disorder of crystal in apatite structure. The more calcium is deficient, the more disorder or imperfect in CDHA structure