In vitro & in vivo correlation of release behavior of andrographolide from silica and PEG assisted silica gel matrix

Silica xerogel and its PEG assisted derivatives were prepared by sol–gel method for controlled release of andrographolide. In vitro and in vivo release of andrographolide from the nano porous silica as well as PEG modified silica matrix were studied. Drug release from the matrix increased with increasing percentage of PEG and followed a biphasic pattern. The in vitro release profile followed zero order kinetics with erosion of the matrix for the first six hours and higuchi model with the diffusion mechanism for rest of the time period. Pharmacokinetic data revealed sustained release of the drug from silica–drug composite with higher elimination t1/2 than the pure drug. For all the formulations Level A in vitro-in vivo correlation (IVIVC) was established with (R2) > 0.98. Histology of different organs was carried out following in vivo administration of the drug-carrier composite. The histological examination demonstrated absence of any inflammatory or degenerative response with the formulations. Fourier transform infrared (FTIR) data revealed the coexistence of andrographolide in the silica matrix. Transmission electron microscope (TEM) images also unfold the repose matrix structure in PEG assisted derivatives than the pure matrix. This study discloses that silica gel and PEG assisted derivatives could be used as a biocompatible and sustained release device for andrographolide.