Silica particles derived from the sol-gel method is an inorganic material that is uniquely suited to encapsulation of biomolecules for drug delivery. Not only is sol-gel derived silica biocompatible, it has the ability to stabilize encapsulated biomolecules through immobilization. Additionally, the nature of the sol-gel synthesis provides that the particle size, surface area, and pore size of the silica can be easily controlled through various synthesis methods. Although there is a fairly large body of work on using sol-gel derived silica as matrices for controlled drug delivery, all the diffusion characterizations have been qualitative and difficult to compare between research groups. This study will present quantitative methods for calculating diffusion coefficients for biomolecules through nanoparticles.

Specifically, this study compares the diffusion of Proteinase K through silica nanoparticles synthesized through three different drying methods, producing particles with varying surface areas (SA) and pore diameters (d): xerogel (SA ~ 100 m^2/g, d ~ 3 nm), ambigel (SA ~ 170 m^2/g, d ~ 4 nm), and aerogel (SA ~ 800 m^2/g, d ~ 25 nm). Additionally, this study will show that the different synthesis methods not only affect the rate of diffusion, but also the ability of the silica matrix to stabilize Proteinase K.