Adjustably bioresorbable sol-gel derived SiO₂ matrices for release of large biologically active molecules

Amorphous, sol-gel derived SiO₂ are known to biocompatible and bioresorbable materials. Bioresorbable materials have potential applications as implants or injectable matrices in the controlled delivery of biologically active agents in the living tissue. Bioresorbable matrices provide desirable properties, e.g., extra removal operations that have to be done with biostable matrices are avoided and the release of large therapeutic molecules can be controlled by matrix degradation rather than by diffusion. New important groups of drugs, such as biotechnically-produced peptides and proteins, are potential to be encapsulated in bioresorbable SiO₂, because they are typically larger in size and their direct oral administration without protecting matrix is difficult due to digestion. The methods to achieve a wide range of SiO ₂ bioresorption rates (from days to months) are introduced in this study. This is done by a "conventional" alkoxy-based sol-gel method at protein-friendly conditions by adjusting the precursor ratios, aging of the sol and by using different preparation methods (casting, spray-drying and freeze-drying). The prepared morphologies include implantable monolithic sticks and injectable microspheres. The importance of chemical structure is shown in comparison with the specific surface area and pore volume.