Silica-polyethylene glycol matrix synthesis by sol-gel method and evaluation for diclofenac diethyloammonium release.

Modified silica-polyethylene glycol xerogels were prepared by the sol-gel method to explore the possibilities of using these polymers as drug delivery systems. The synthesis was performed at room temperature and under atmospheric pressure using tetraethylorthosilicate (TEOS) as a precursor, low-molecular polyethylene-glycol (600) as a modifier, and acetic acid as a catalyst. The composition in a mole ratio of the initial sols corresponds to TEOS:H(2)O:EtOH:CH(3)COOH:PEG = 1:4:6:0.005:0.147. Diclofenac diethyloammonium was used as a model drug and encapsulated in predoping sol-gel process. After 5 days of gelation time of matrices at room temperature two different forms of xerogels were obtained: monolithic form of pellet and cracked, irregular-shaped of particles. The rate of release from the both forms of xerogels was controlled by the rate of diffusion of the drug through the pores. The dissolution testing for the loaded irregular-shaped xerogels showed an initial burst release followed by sustained release. The degradation of the PEG/silica xerogels followed a zero-order kinetics.