A method for making an enzyme encapsulated in a porous silicate matrix. An anhydrous preparation of tetramethylorthosilicate begins to hydrolyse as soon as it is in contact with an aqueous enzyme solution. The newly formed hydroxy groups of the silicate condense with themselves and with hydroxymethyl groups to form a water-sol phase, and then a gel that entraps the enzyme. The result is a glass-like transparent solid that may have uses in biotechnology, e.g. in a biosensor.