Electrochemical-based enzyme immobilization methods are a convenient way of immobilizing enzymes on microelectrodes, albeit one restricted only to amperometric sensors. They enable the immobilization to be localized at one electrode (the working electrode), frequently offer some control of the thickness of the resultant film, and may offer significant interference rejection properties. Furthermore, the immobilization can usually be performed from aqueous solution near neutral pH and can coat complex or otherwise inaccesible surfaces, such asin situdetectors. Although in principle they could be used in mass production to perform on-wafer level modifications (i.e., to immobilize enzyme in separate regions of a whole silicon wafer, prior to dicing it into separate devices) they are usually used only in the final stages on sensor fabrication to modify individual devices. As with the photochemical-based immobilization (seeChapter 11 ), electrochemical techniques do require some specialized equipment. In this chapter, we shall describe two depositions, one entrapment in an electrochemically grown polymer, the other electrochemically aided crosslinking.
