Effects of cooling conditions and chitosan coating on the properties of porous calcium phosphate granules produced from hard clam shells

The main inorganic components of clam shells are calcium carbonate and trace elements of magnesium, strontium, and zinc. Clam shells can be used as a calcium source to synthesize calcium phosphates, and these trace elements promote the growth of bone tissue and improve the performance of bioceramics. In this study, hydroxyapatite (HA) powders were synthesized from clam shells, and porous calcium phosphate granules were prepared through the gas foaming technique. In addition, the effects of a chitosan coating and cooling conditions on the strength of the porous granules were investigated. The results indicated that the samples produced under the furnace cooling condition were biphasic hydroxyapatite/β-tricalcium phosphate granules (HA/β-TCP), whereas the samples produced under the air-cooling condition were triphasic hydroxyapatite/β-tricalcium phosphate/α-tricalcium phosphate granules (HA/β-TCP/α-TCP). The compressive strength of the porous granules prepared through air cooling was 79% higher than that of the granules produced through furnace cooling. The compressive strength of the air-cooled sample after the subsequent application of the chitosan coating further increased by 21%. A degradability test revealed that the weight loss rate of the air-cooled samples was greater than that of the furnace-cooled samples, which was due to the presence of high-solubility α-TCP in the air-cooled samples.