Controlled drug delivery from porous hydroxyapatite grafts: an experimental and theoretical approach

Cylindrical hydroxyapatitic grafts at two different degree of porosity (60% and 40%) were tested as controlled drug delivery devices in order to evaluate the fundamental parameters which control release kinetics. The effect of device porosity, drug steric hindrance and drug loading on kinetics release has been appreciated using Ibuprofen-lysine and Hydrocortisone Na-succinate as non-steroidal and steroidal anti-inflammatory drug-models, respectively. The data put in evidence the difficulty for the more sterically hindered molecules to move throughout the microporosity of the ceramic graft. Furthermore, the results show how the higher drug load produces an initial higher release and how the less porous is the ceramic graft, the more evident is the initial burst release. A numerical approach, based on the use of the Finite Element Method, was adopted to describe the drug release kinetics from the porous ceramic graft. Numerical results on drug release in phosphate buffer saline solution were compared with experimental data and a good agreement was found. The importance of FEM modelling emerges as a predictive tool to study HA graft drug release performances in an efficient way, also in complex set-ups like the one here selected.