Low Fluorescence Enzyme Matrices Based on Microfabricated SU-8 Films for a Phenol Micro-Biosensor Application

Abstract

In this contribution, the possibility of using SU-8 photoresist, a polymer widely used in MEMS applications, for the development of inexpensive and disposable optical phenol micro-biosensors is explored. The immobilisation of the enzyme, the encapsulation of the indicator and the patterning of the SU-8 were accomplished simultaneously in a simple one step microfabrication process. The enzyme still showed activity after encapsulation in SU-8 although the process involved its embedding in a hard and rigid epoxy resin matrix. This was carried out by measuring the signal of an oxygen-sensitive indicator (ruthenium-complex) through monitoring of the enzymatic oxidation of phenol which consumes oxygen. Films without enzyme showed negligible variation in fluorescence intensity upon phenol addition, whereas films with encapsulated enzyme and oxygen-sensitive fluorescent indicators showed a very clear change in fluorescence intensity upon addition of phenol. The current work demonstrates a new concept of a low cost immobilisation technique in combination with the microfabrication process for biosensor technology.