Porous silicon nitride-based drug delivery carrier

Tetracalcium phosphate/monetite biocement was modified with the addition of 30 wt% highly porous silicon nitride/alpha-tricalcium phosphate (alpha-TCP) microgranules. The volume ratio of Si3N4 and alpha-TCP in microgranules was 1:1 and showed good in vitro simulated body fluid bioactivity with precipitation of hydroxyapatite particles. The intention of addition of microgranules to the biocement was to have a carrier of drug, which can be released into the body in due time. Granules prepared by the freeze granulation of starting mixture of silicon nitride and calcium phosphate and subsequent sintering at 1100 degrees C have a suitable pore structure for the foreseen use. The pore volume was almost 1000 mm(3)/g with the open porosity of 77 vol%. This porosity and the biocompatible composition of silicon nitride-based granules gave a chance to fabricate a suitable composite cement for dexamethasone (DMZ) drug release into the human body. An accelerated release of dexamethasone from composite cement was observed and the full amount of DMZ was released from the composite biocement after 10 days. The presented results are a good base to adjust the total drug release time by the mixing of an appropriate amount of drug infiltrated ceramic granules with the tetracalcium phosphate/monetite cement.