| Numerous biosensing chemistries have been developed. The first is one where redox polymers and enzymes are deposited in a layer-by-layer manner taking advantage of electrostatic interactions between cationic redox polymers and anionic enzymes. The next scheme also used electrostatic interactions for the immobilization of enzymes. Oxidases were electrostatically entrapped in hyperbranched, poly(acrylic acid) films. The third scheme initially employed covalent coupling, via Michael-type reactions, of acrylated poly(ethylene glycols) and highly aminated poly(allylamine) to form multiple layers. Subsequently, glucose oxidase was used as a replacement for these components to form a covalently coupled multilayer structure containing the enzyme. The fourth and final biosensor development scheme was based on thin poly(ethylene glycol) films that were spin-coated and photopolymerized on various substrates. Of all the tested schemes, the electrostatic layer-by-layer scheme proved to be the simplest to implement resulting in highly reproducible responses. Thus, this technique was used to deposit sensing layers on photolithographically patterned gold electrode arrays, resulting in redundant biosensor arrays that demonstrated standard deviations less than 20%. Finally, the possibility of developing an algorithm based on principal component analysis was explored to detect faulty sensors within an array along with attempting to identify the specific mechanism of failure in real time. |
