Si-modified BHA bioceramics as a drug delivery system: Effect of modification method on structure and Rifampicin release

The work is devoted to the investigation of two different methods for introduction of silicon into ceramics, based on biogenic hydroxyapatite (BHA), on the structure and properties. Thus, porous samples of Si-modified BHA-based ceramics containing 2 or 5 wt.% Si were prepared by using two different precursors, i.e. polymethylsiloxane polyhydrate and fine silica (Aerosil? 200) powder. After the modification with silicon a marked change in the structure of material was observed. The use of Aerosil? 200 permits preparation of a more uniform structure as compared to that obtained by using polymethylsiloxane polyhydrate. However, the latter promotes an increase in both the porosity of samples (from 43 to 62.3%) and their solubility in saline (from 0.18 to 1.20wt.%/day) as compared to the results obtained after the modification with Aerosil? 200, where maximal porosity and solubility were 48.5% and 0.23wt.%/day, respectively. At the same time, the modification of hydroxyapatite ceramics with silicon using silica makes it possible to prolong release of a drug (e.g. Rifampicin) out of sample pores for the first 24 h as compared to the ceramicsmodified with polymethylsiloxane polyhydrate.