Studying the spatially resolved immobilisation of enzymes on a capacitive field-effect structure by means of nano-spotting

Conventional methods for enzyme immobilisation onto sensor surfaces often use dip-, drop- or spin-coating techniques. In this study, a nano-spotting technique has been investigated for a patterned, spatially resolved deposition of enzymes onto a capacitive field-effect electrolyte-insulator-semiconductor (EIS) sensor and compared with the drop-coating method. Therefore, four different sensor arrangements covered with immobilised penicillinase as a model enzyme have been studied: (i) The sensor surface fully drop-coated, (ii) half drop-coated, (iii) half nano-spotted and (iv) fully nano-spotted with penicillinase. The sensors have been electrochemically characterised in pH buffers and penicillin solutions by means of impedance-spectroscopy, capacitance-voltage and constant-capacitance methods.