Bioactive enzyme–metal composites: The entrapment of acid phosphatase within gold and silver

This paper is concerned with the entrapment of an enzyme within an aggregated metallic matrix and the development of a bioactive enzyme–metal composite. Whereas the use of organic polymers and metal oxides for the preparation of enzymatically active materials is well developed, the third principle enzyme–material combination, namely protein–metal bulk, has not yet been reported. A new methodology for the entrapment of organic molecules and polymers within metals has been employed for the preparation of bioactive acid phosphatase@gold and acid phosphatase@silver, according to which room temperature reduction of the metal cation is carried out in the presence of the enzyme to be entrapped. Protectability of the entrapped enzyme against harsh conditions is shown: the acidic enzyme is kept alive under basic conditions.