Molecularly Imprinted Polymer Sensor for Nanomolar Ethyl Carbamate Detection

Overview

VeriPrime has discovered a possible link between ethyl carbamate (EC) in cattle feed and late-stage cattle death, which costs American farmers $700 million a year. They have asked our group to design and fabricate molecularly imprinted polymer (MIP) electrochemical sensors to detect EC at nanomolar concentrations. The sensors must be specific to EC only and be constructed with the fact that the end users are not chemists in mind. The process should be streamlined and repeatable, and low enough cost to suggest market viability.

Objectives

The team’s objective was to develop a molecularly imprinted polymer (MIP) sensor for the detection of ethyl carbamate (EC) in solutions with concentrations in the nanomolar range. We looked to create a calibration curve based on the relationship between solutions with known EC concentrations and changes in current observed after a voltage is applied.

Approach

This project was a continuation of the Fall 2022 Capstone project. We used the standard operating procedure developed by the fall team for making the monomer, washing, and calibration solutions, the polymerization process, and the calibration process. However we had to mak medications to the original SOP to mitigate electrolyte over-saturation. We used cyclic voltammetry to deposit and grow film of poly(o-aminophenol) onto the working electrode. We then washed the sensor in a H2SO4 washing solution to clear EC from the binding sites and dried them at room temperature. Finally, we attempted to make a calibration curve using phosphate buffer solution (PBS) and ethyl carbamate solutions of varying concentrations by measuring the current of the ferricyanide redox reaction using cyclic voltammetry. The final goal was to calculate the limit of detection using the calibration curve, though issues arose with this. At a few points during the process, optical and scanning electron microscopy were used to ensure that the polymer film was successfully deposited onto the electrode and observe any differences between the electrodes. The team also participated in weekly meetings with VeriPrime to discuss goals, results, progress, and feedback.

Outcomes

After the modifications of the calibration process, the team was able to successfully develop a working electrode to detect EC and a calibration curve. However, we ran into issues with film reproducibility. A theory is the washing solution is too concentrated for the ceramic Metrohm electrodes. We believe by diluting the wash it is possible to get a more reproducible film and reproducible graphs.