Immobilization of biomolecules in sol-gels: Biological and analytical applications

The encapsulation or generation of new surfaces that can fix biomolecules firmly without altering their original conformations and activities is still challenging for the utilization of biochemical functions of active biomolecules. Presently, sol-gel chemistry offers new and interesting possibilities for the promising encapsulation of heat-sensitive and fragile biomolecules (enzyme, protein, antibody and whole cells of plant, animal and microbes); mainly, it is an inherent low temperature process and biocompatible. The typical sol-gel process initiates by the hydrolysis of M(OR) 4 and is performed in the presence of the active biomolecule. Hydrolysis and condensation of the M-monomers in the presence of an acid or base catalyst trigger cross-linking with formation of amorphous MO 2 , a porous inorganic matrix that grows around the biomolecule in a three-dimensional manner. This class of sol-gel matrices possesses chemical inertness, physical rigidity, negligible swelling in aqueous solution, tunable porosity, high photochemical and thermal stability, and optical transparency. These attractive features have led to intense research in the optical and electrochemical biosensors, which may be useful for medical, environmental and industrial applications. On the other hand, sol-gel encapsulated organelles have been transplanted to the living systems, and plant/animal/microbial cells have also been employed for the production of commercially important metabolites. This review article highlights the advantages, recent developments, applications and future perspectives of sol-gel immobilized biomolecules, which includes enzymes, antibodies, microorganisms, plant and animal cells.