We review the growing field of entrapment of purified enzymes, whole c
ells, antibodies, and other proteins in sol-gel matrices prepared from
metal alkoxides. Basic aspects of the nature of the trapping and its
effects on the dopant activity are discussed, and various applicative
uses of these novel bioactive materials are presented, including senso
rs, biosensors, electrodes, immunoadsorbents, optical components, envi
ronment-related materials, and biotechnology-related materials. Outloo
k of potential applications and future directions of this field are pr
ovided throughout the review.