An asymmetric coating composed of gelatin and hydroxyapatite for the delivery of water insoluble drug

An asymmetric coating composed of gelatin and hydroxyapatite on Ti6Al4V alloy implant was prepared to control the release of water-insoluble drug ibuprofen and improve the surface properties of the implant. The asymmetric coating developed into a thin dense outer layer and a thick porous inner layer using a dip-coating method and a succedent phase-inversion process. The drug loading ranged from 10 to 30% (w/w), and depended on the immersion time and drug concentration in the quenching solution. The in vitro release from this system was always at an approximately zero-order rate and at least lasted for 30 days. The in vitro studies in SBF revealed that the coating could induce the formation of apatite, and was fully covered after 14 days soaking in SBF solution. This asymmetric coating had better bioactivity of inducing the formation of apatite in vitro, compared with pure gelatin coating and bare Ti6Al4V implant.