Silicon-polymer hybrid materials for drug delivery

Silicon and its oxides are widely used in biomaterials research, tissue engineering and drug delivery. These materials are highly biocompatible, easily surface functionalized, degrade into nontoxic silicic acid and can be processed into various forms such as micro- and nano-particles, monoliths, membranes and micromachined structures. The large surface area of porous forms of silicon and silica (up to 1200 m(2)/g) permits high drug loadings. The degradation kinetics of silicon- and silica-based materials can be tailored by coating or grafting with polymers. Incorporation of polymers also improves control over drug-release kinetics. The use of stimuli-responsive polymers has enabled environmental stimuli-triggered drug release. Simultaneously, silicon microfabrication techniques have facilitated the development of sophisticated implantable drug-delivery microdevices. This paper reviews the synthesis, novel properties and biomedical applications of silicon polymer hybrid materials with particular emphasis on drug delivery. The biocompatible and bioresorptive properties of mesoporous silica and porous silicon make these materials attractive candidates for use in biomedical applications. The combination of polymers with silicon-based materials has generated a large range of novel hybrid materials tailored to applications in localized and systemic drug delivery.