HOLLOW HYDROXYAPATITE MICROSPHERES FOR CONTROLLED DELIVERY OF PROTEINS

摘要

Hollow hydroxyapatite (HA) microspheres were prepared by reacting solid microspheres of a lithium-calcium-borate glass (106-150 microns) for 2 days in K_2HPO_4 solution (0.02 M; 37°C), and evaluated as a controlled delivery device for a model protein, bovine serum albumin (BSA). The as-prepared HA microspheres had a hollow core with a diameter equal to 0.6 the external diameter, a surface area of ∨100 m~2/g, and a mesoporous shell wall (pore size of = 13 nm). After loading the hollow HA microspheres with a solution of BSA, release of the BSA into a medium of phosphate-buffered saline (PBS) was measured as a function of time using a micro bicinchoninic acid (BCA) protein assay reagent. BSA release initially increased linearly with time, but almost ceased after 24-48 hours. Modification of the BSA release kinetics was achieved by altering the microstructure of the shell wall of the as-prepared HA microspheres using a controlled heat treatment (5 h at 600°C-900°C). Sustained release of BSA was achieved over than 7-14 days from HA microspheres heated for 5 h at 600°C. The potential application of these hollow HA microspheres as a device for controlled local delivery of protein growth factors and drugs is discussed.