Tricalcium phosphate and tricalcium phosphate/polycaprolactone particulate composite for controlled release of protein.

β-Tricalcium phosphate (β-TCP) with three different particle size ranges was used to study the effects of particle size and surface area on protein adsorption and release. Polycaprolactone (PCL) coating was applied on the particle systems to investigate its effect on particulate system properties from both structural and application aspects. The maximum loading of 27 mg/g was achieved for 100 nm particles. Bovine serum albumin (BSA) loading amount was controlled by varying the BSA loading solution concentration, as well as the sample powder's surface area. Increasing the surface area of the delivery powder significantly increased loading and release yield. Unlike the samples with low surface area, the lowest particle size samples showed sigmoidal release profile. This indicated that release was governed by different mechanisms for particles with different sizes. While the majority of samples showed no more than 50% release, the 550 nm particles demonstrated 100% release. PCL coating showed no significant ability to attenuate burst release in PBS. However, it led to a steadier release profile as compared to the bare TCP particles. FTIR analysis also proved that the secondary structure of BSA did not change significantly during the adsorption; however, minor denaturation was found during the release. The same results were found when PCL coating was applied on the TCP particles. We envision potential use of TCP and TCP+PCL systems in bone growth factor or orthopedic drug delivery applications in future bone tissue engineering application.