Abstract
Built upon previously gained knowledge, a novel, layer by layer assembled carbon nanotube sensor for detection of two analytes is discussed. The main idea is to functionalize the carbon nanotubes with different enzymes and bio-polymers to build a multi-functional series of interfaces, which are sensitive to their respective substrates. Organophosphorus hydrolase and glucose oxidase should be separately, covalently immobilized onto multi-walled carbon nanotubes (MWNT-OPH and MWNT-GOx) for catalytic hydrolysis of the model organophosphate, paraoxon (PX) and catalytic oxidation of β-D-glucose. The catalytic response of the different layers was characterized by amperometry with redox mediator. While the sensor to simultaneously detect both glucose and paraoxon is not inherently practical, the experiment shows the possibility for co-interfacing multiple enzymes on the same platform. This may be very important to allow for the detection of several substrates, through the use of numerous biocatalysts on separate layers. Additionally, this approach might be applied for systems where several biocatalysts are assembled to work in a consecutive mode and the product of previous reaction might be a substrate for the next one.