Lovastatin release from polycaprolactone coated β-tricalcium phosphate: Effects of pH, concentration and drug-polymer interactions

The approach of local drug delivery from polymeric coating is currently getting significant attention for both soft and hard tissue engineering applications for sustained and controlled release. The chemistry of the polymer and the drug, and their interactions influence the release kinetics to a great extent. Here, we examine lovastatin release behaviour from polycaprolactone (PCL) coating on p-tricalcium phosphate (beta-TCP). Lovastatin was incorporated into biodegradable water insoluble PCL coating. A burst and uncontrolled lovastatin release was observed from bare beta-TCP, whereas controlled and sustained release was observed from PCL coating. A higher lovastatin release was observed pH 7.4 as compared to pH 5.0. Effect of PCL concentration on lovastatin release was opposite at pH 7.4 and 5.0. At pH 5.0 lovastatin release was decreased with increasing PCL concentration, whereas release was increased with increasing PCL concentration at pH 7.4. High Ca2+ ion concentration due to high solubility of beta-TCP and degradation of PCL coating were observed at pH 5.0 compared to no detectable Ca2+ ion release and visible degradation of PCL coating at pH 7.4. The hydrophilic-hydrophobic and hydrophobic-hydrophobic interactions between lovastatin and PCL were found to be the key factors controlling the diffusion dominated release kinetics of lovastatin from PCL coating over dissolution and degradation processes. Understanding the lovastatin release chemistry from PCL will be beneficial for designing drug delivery devices from polymeric coating or scaffolds. (c) 2013 Elsevier B.V. All rights reserved.