The sol-gel process opens new possibilities in the field of biotechnology. Enzymes such as glucose oxydase and lipase can be trapped within sol-gel glasses without loosing their bioactivity. Small analytes diffuse through the pores of the silica matrix allowing in-situ biocatalytic reactions to be performed. Escherichia coli bacteria have also been encapsulated. Their cellular organization is preserved and they still exhibit noticeable enzymatic activity, even on dried xerogels. Antibody-antigen recognition has been shown to be feasible within 'sol-gel matrices and whole cell protozoa have been used as antigens for blood tests with human sera.