Immobilization of enzymes by multilayer microcapsules

A method is described to obtain a new type of microcapsules for immobilization of enzymes or living cells. The wall of these capsules consists of several layers of poly(ethyleneimine) and poly(acrylic acid). The idea is that diverging properties of the whole assembly can be better controlled when the membrane is built up by several consecutive steps, each being optimized with respect to a special property, for example, permeability or mechanical strength. The encapsulation of acidic phosphatase and the cleavage of p ‐nitrophenyl phosphate was used as a model system. The charged capsules were characterized by their enzymatic activity, as a function of membrane composition (number and sequence of layers) and storing time. The permeability for the substrate and the retaining ability for the enzyme were also measured.