Study on organically modified SiO2 xerogel as a drug carrier for delivering hydrophobic agents
Biocompatible and biodegradable nano-hybrids are becoming increasingly important as drug-loaded implants and drug-eluting coatings for biomedical devices. The key successful point of the drug-loaded implantable devices for biomedical application is not only the sufficient encapsulation efficiency for clinical use, but also the controlled release of bioactive agents to exert therapeutic effect. However, the surface of silica xerogel exhibits a hydrophilic character which is unfavorable for the encapsulation of hydrophobic agents. On this basis, a novel organically modified SiO2/glycerol hybrid with biodegradable nature was successfully fabricated and employed as a vehicle to encapsulate amphiphilic bioactive agent, i.e., ibuprofen (IBU). The IBU loading efficiency and release behaviors from the novel SiO2/glycerol hybrid was investigated in terms of glycerol content and the pH value in the synthetic process. Preliminary results showed that both two synthetic parameters significantly affected the porosity, pore size and micro-environment of the nanostructure of the SiO2/glycerol hybrid. Subsequently, drug encapsulation efficiency and release behaviors were altered. Moreover, the glycerol reacted with SiO2 to form SiO2-glycerol complex demonstrating a weakly cross-linked structure, which significantly altered the nanostructure and subsequent drug release behaviors of the modified SiO2 xerogel. A novel chemically modified SiO2/glycerol/DMSO nano-hybrid was successful synthesized by incorporating various content of DMSO in the sol-gel process, and proposed to encapsulate a partially hydrophobic anti-tumor drug, such as doxorubicin (DOX). The DOX encapsulation efficiency of the hybrid xerogel was higher than that of pristine SiO2 xerogel. In addition, the polar aprotic solvent, DMSO significantly affected the nanostructure of the SiO2/glycerol/DMSO nano-hybrid, resulting in various drug release behaviors. Interestingly, the SiO2/glycerol/DMSO nano-hybrid demonstrated a flexible characteristic which is suitable for the drug-eluted coating employed for stent. These results demonstrate that the newly organically modified SiO2 xerogel showed an enhanced encapsulation efficiency of hydrophobic agents, and a variety of drug controlled release behaviors.