Despite the many governmental and medicinal restrictions created to combat the opioid epidemic in the United States, opioid abuse and overdose rates continue to rise. The development of an aptamer-based voltammetric sensor and biosensor is described in this dissertation. The aim was to develop a low-cost, sensitive, and specific aptamer-based sensor for on-site, label-free determination of codeine and fentanyl in biological fluids. To do this, the surfaces of screen-printed carbon electrodes (SPCE) were modified with gold nanoparticles (AuNPs), followed by the addition of single-stranded DNA aptamers. These were covalently bound to the electrode surface. Operations of the sensors were collected using an electroactive solution such as ferrocyanate was aspirated onto the detector, producing a steady current due to oxidation at the electrode surface. Upon target binding, the DNA aptamers coalesce. The resultant complex decreases access to the surface due to steric hindrance with a concomitant decrease in signal. Diffusion of the electroactive solution to the electrode surface increased when more significant target drug concentrations were present in the sweat. The generated electrical current was collected and analyzed via square wave voltammetry and electrochemical impedance spectroscopy.
Applying this aptasensing approach to modified commercial SPCEs permitted the detection of nanomolar concentrations of codeine and fentanyl in biological fluids. After providing proof-of-concept with a commercial SPCE, a paper-based SPCE was developed for the aptasensing of opioids. The performance of the paper-based sensor produces a current approximately 2x less than the commercial disposable sensor. Ultimately, the fabrication and development of this novel biosensor for the detection of opioids present a novel strategy for opioid detection through the use of disposable, paper-based, screen-printed carbon electrodes. Furthermore, the low cost and convenience of this procedure should further aid the development of related screening methods for forensic and medical applications.