Adsorption/desorption of acidic and basic proteins on needle-like hydroxyapatite filter prepared by slip casting

The adsorption/desorption of proteins, such as the bovine serum albumin (BSA) as an acidic protein and the lysozyme chloride (LYZ) as a basic protein, was investigated with the needle-like hydroxyapatite(N-HAp) filters after fired at several fixed temperatures. The filters were prepared by a slip casting with the aqueous N-HAp(commercial powder:Ca/P=1.54) slips supplemented with calcium hydroxide [Ca(OH)2] for the lack of calcium. The cast filters were fired in H2O vapor at the range of 600–1200 °C. The adsorbed amounts were measured with the N-HAp fired filters. For both the BSA and LYZ, the adsorbed amounts increased with increasing the fired temperatures. Furthermore, the proteins desorption was also investigated by a column chromatograph using the linear gradient method with the sodium phosphate buffer solution (PBS). The PBS concentration at which the BSA was desorbed from the filters was independent to the firing temperature of the filters. However, for the LYZ, the PBS concentration increased with increasing the fired temperatures. From the results, it was found on the filters fired more than 1000 °C that the LYZ adsorbed stronger to the HAp filters than the BSA.