主催: The Japanese Society for Dental Materials and Devices
Introduction: Our previous study showed that hydroxyapatite (HAp) synthesized in the presence of aspartic acid (Asp) changed the morphology and crystallinity of synthesized HAp. FTIR results indicated that Asp was included in the synthesized HAp. However, the mechanism how Asp is uptaken in the HAp is not fully understood. To understand this mechanism, the adsorption/desorption of Asp onto/from HAp particles was examined. Materials and Methods: For the adsorption study, 200 mg of HAp powder was mixed with 40 ml of PBS containing Asp (0.05-0.25 mol/l) by stirring for 2 h at a controlled pH 7.4 at 800C. For the desorption study, 10 mg of HAp powder synthesized in the presence of Asp (HAp-Asp, 0.05-0.5 mol/l) was mixed with 10 ml of PBS or 5-20 mmol/l NaCl dissolved PBS by 1 h stirring. In both the adsorption and the desorption study, Asp in the supernatant liquid was collected and measured by UV-VIS spectrophotometer. FTIR analysis of precipitated particles was also performed to confirm the adsorption/desorption of Asp onto/from HAp. Results and Discussion: Adsorption study showed that adsorbed amount of Asp onto normal HAp increased linearly with increase of Asp concentration (0.05-0.25 mol/l) in the solution. FTIR data of precipitated particles confirmed the adsorption of Asp onto normal HAp. To understand whether Asp in HAp-Asp is either a simple adsorption or not, we evaluated the desorption of Asp from HAp-Asp. If it is a simple Asp adsorption onto HAp, Asp release from HAp-Asp would be possible by altering the ionic strength of solutions. However, different ionic strength (NaCl, 5-20 mmol/l) dissolved in PBS did not enhance the desorption of Asp from HAp-Asp (0.05-0.5 mol/l). Therefore, it might be considered that Asp in HAp-Asp is physically packed in the apatite structure so that it cannot be released from HAp-Asp.
