Hydroxyapatite composite from natural materials prepared by hydrothermal processing

• Natural materials - cockle shells could be source of hydroxyapatite composite. • Obtained composite forming a microporous structure with an extensive inner surface. • Hydroxyapatite composite obtained by hydrothermal processing was chemically stable. • Composite material (Hydroxyapatite + mullite) may be applied as an implant material. This paper presents a hydrothermal method of obtaining hydroxyapatite (HAp) from natural material – shells of shellfish. The method of deriving hydroxyapatite from shellfish shells is based on the interaction between phosphate compounds and shells, which are made of calcium carbonate (aragonite). X-Ray, SEM and EDS analysis, electrokinetic potential and electric conductivity measurements, were used to characterize the properties of the material. X-Ray analysis confirmed that the hydroxyapatite was created in the process of synthesis of calcium compounds. The obtained composite was composed of 1 µm grains forming a microporous structure with an extensive inner surface. The zeta potential for the obtained hydroxyapatite composite at pH 7.00 was -7.5 mV and is similar to the potential of the healthy bone. The chemical stability analysis of the HAp material was carried out based on the changes in the pH of the simulated body fluid. During the seventeen days of tests the pH was almost unchanged. Electrical conductivity of the distilled water at a temperature of 36.5°C was about 0.65 mS. Based on the kinetics examinations it will be possible to determine the composite suitability for its application as an implant material in medicine.