Enzyme multilayers on colloid particles: Assembly, stability, and enzymatic activity

Colloidal biocatalysts, comprising polystyrene (PS) carrier particles coate d with enzyme multilayers, were fabricated via the layer-by-layer self-asse mbly method. Glucose oxidase (GOD), horseradish peroxidase (POD), or prefor med enzyme-polyelectrolyte complexes were assembled in alternation with opp ositely charged polyelectrolytes onto PS particles. Microelectrophoresis, s ingle-particle light scattering, and transmission electron microscopy confi rmed stepwise growth of the multilayer films on the colloid particles. The high surface area Enzyme multilayer-coated particles were successfully empl oyed as specific enzyme reactors (i.e., as catalysts). Whereas no loss in a ctivity was observed for the enzymes immobilized directly onto particle sur faces, precomplexing the enzymes with polymer in solution drastically reduc ed their activity (by up to 70%). The enzymatic activity (per particle) was found to increase with the number of enzyme layers immobilized, irrespecti ve of whether the enzyme was precomplexed. However, particles coated with p reformed enzyme-polyelectrolyte complexes displayed a significantly lower e nzymatic activity than those fabricated by the direct adsorption of free en zyme. Multicomponent films of GOD and POD on colloid particles were also pr epared, and sequential enzymatic catalysis was demonstrated. Furthermore, e xperiments were conducted with particles exhibiting both magnetic and catal ytic functions. These particles, premodified with a layer of magnetic nanop articles to impart a magnetic property and subsequently coated with enzyme multilayers, were repeatedly used as catalysts following their rapid and ea sy separation with a magnet. Such biocolloids are expected to find applicat ions in biotechnology.