Preparation of novel hemostatic material containing spherical porous hydroxyapatite/alginate granules

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A novel and biocompatible hemostatic material was prepared by mixing porous spherical hydroxyapatite (Ca10(PO4)6(OH)2; HAp)/alginate (AG) granules with a random copolymer of ethylene oxide and propylene oxide (EPO). Two kinds of HAp powders with different particle shapes, i.e., whisker-like HAp (w-HAp; mean long-axis length, 38.0 µm; short-axis length, 1.90 µm) and nanometer-sized HAp (n-HAp; approximate sizes, 0.03 µm × 0.05 µm) were used for the preparation of granules. The HAp–AG granules with diameters of 1.5 to 3.0 mm were prepared through (i) introduction of the spherical droplets containing 2 mass% sodium alginate and HAp particles (w-HAp or n-HAp; HAp/AG = 1.0) into 1 mol·dm−3 CaCl2 solution by using a syringe, (ii) freezing of resulting spherical gels at −80°C and (iii) drying of gels at −50°C for 24 h. The water absorptions of w-HAp/AG and n-HAp/AG granules after 3 d immersion at 37.0°C were 217 mass% and 66 mass%, respectively, indicating that the porosities of the former granules were higher than those of the latter. The stanching times of blood, which were evaluated by measuring how soon the papers on the EPO gels with 60 mass% HAp (i.e., w-HAp and n-HAp)/AG granules got wet by the simulated blood that came out on top of the porous HAp cube (porosity, 70%; mean pore size, 200 µm) due to the capillary force, were estimated to be approximately 5 h.