The encapsulation of biomolecules, e.g. enzymes, whole living cells or microorganisms in sol-gel derived monolithic silica, has been widely studied in recent years. Upon encapsulation, biomolecules retain their spectroscopic properties and biological activity. Sol-gel matrices are thermally and chemically stable and can be obtained in a variety of forms, such as optically transparent monoliths, granulates, microparticles or thin films. Sol-gel immobilization is characterized by physical entrapment without chemical modification. Immobilizing substances by physically trapping in individual pore of a matrix permits their molecules to be isolated and stabilized. The advantages of sol-gel encapsulated biologicals might give them applications such as optical and electrochemical sensors, diagnostic devices, catalysts, and even bioartificial organs. While the relatively large biomolecules are immobilized within the silica network, small ions or molecules are transported into the interior of the matrix.