Periodic Macroporous Hydroxyapatite-Containing Calcium Phosphates

Three-dimensionally ordered macroporous materials containing the bioceramic hydroxyapatite as well as other calcium phosphate and carbonate phases have been synthesized using close-packed poly(methyl methacrylate) latex spheres (256−375 nm diameter) as templates. The interstitial spaces of the colloidal crystal were penetrated by a water/alcohol cosolvent solution of calcium nitrate and phosphoric acid. Calcination in the range 475−1000 °C removed the polymer and promoted crystallization of calcium phosphate phases in the pore walls. The materials were characterized by powder X-ray diffraction, FT-IR spectroscopy, and SEM. The best combination of composition and three-dimensional order was found in a crystalline hydroxyapatite/tricalcium phosphate templated with 375-nm spheres and calcined at 700 °C. An in vitro antibiotic drug release application was tested using this product.