PEG-Hydrogel Coated Silica Aerogels: A Novel Drug Delivery System

摘要

A novel composite of silica aerogel-poly(ethylene glycol) PEG hydrogel was synthesized and its potential as a drug delivery system was investigated. The composite was synthesized by encapsulation of hydrophobic aerogels within PEG hydrogel via photoinitiated polymerization. Disks of aerogels were synthesized by the two step sol-gel method using tetraethylortosilicate (TEOS) as the silica precursor. After aging in ethanol, the alcogels were loaded with eosin-Y photoinitiator. The surface of eosin functionalized silica aerogels was then rendered hydrophobic using hexamethyldisilazane (HMDS) as the surface modification agent, and supercritical carbon dioxide (scCO_2) as the solvent. Hydrophobicity of aerogel was tuned by changing HMDS amount dissolved in ScCO_2 phase which resulted in the change of the contact angle between 0 and 128°. Hydrophobic or hydrophilic aerogels were then dipped into a PEG diacrylate prepolymer solution, and photopolymerization was carried out using visible light (514 nm). BET surface area and pore size distribution measurements showed that both hydrogel encapsulation and eosin-Y loading did not affect the pore structure of the aerogel. The potential of this composite as a drug delivery system was tested by Ketoprofen as a model drug. The results demonstrate that both drug loading capacity and drug release profiles could be tuned by changing the hydrophobicity of aerogels, and that drug loading capacity increases with decreased aerogel hydrophobicity while slower release rates are achieved with increased hydrophobicity from eosin functionalized aerogels. The effect of PEG concentration (0, 15 %, and 30 % w/w) in the prepolymer solution of the hydrogel coating on drug release rate from hydrophilic aerogel was also investigated. It was seen that as the PEG concentration increased, the drug release was retarded. The experimental results showed that drug release can be controlled with this novel aerogel-hydrogel composite system via changing hydrophobicity of the aerogel, and the concentration of the PEG in the hydrogel coating.