Date of Award


Document Type


Degree Name

Master of Science


Department of Systems Engineering and Management

First Advisor

Mark N. Goltz, PhD.


A biosensor for the detection of organophosphates in water was created by immobilizing acetylcholinesterase (AChE) on a carbon screen printed electrode using peptide nanotubes (PNT) and Nafion®. This sensor was used with acetylthiocholine (ASCh) substrate to detect the inhibitory effects of malathion. The stability of the encapsulated enzyme was measured over 50 days of storage at 4°C in a phosphate buffer solution. The oxidation of thiocholine, a product of the enzymatic reaction of ASCh and AChE, was used to measure the activity of the encapsulated enzyme. Cyclic voltammograms were taken in an ASCh and phosphate buffer solution, and the peak oxidation was used to measure the performance of the sensor. Amperometric studies were also conducted at 310 mV vs Ag/AgCl to measure the response of the sensors to ASCh and malathion. This research demonstrates that the use of PNTs and Nafion® allows the sensor to remain stable under these conditions for a much longer period than similar biosensors relying on adsorption alone, losing 17.3% and 14.2%, activity, respectively, after 50 days. Detection limits of as low as 48 nM of malathion were obtained using PNT, and 102 nM using PNT and Nafion®.

AFIT Designator


DTIC Accession Number