Microfluidic electrochemical immunosensor for the trace analysis of cocaine in water and body fluids

Abstract

Quick but accurate testing and on-the-spot monitoring of cocaine in oral fluids and urine continues to be an important toxicological issue. In terms of drug testing, a number of devices have been introduced into the market in recent decades, notably for workplace inspection or roadside testing. However, these systems do not always fulfill the requirements in terms of reliability, especially when low cut-off levels are required. With respect to surface water, the presence of anthropogenic small organic molecules such as prescription and over-the-counter pharmaceuticals as well as illicit drugs like cannabinoids, heroin, or cocaine, has become a challenge for scientists to develop new analytical tools for screening and on-site analysis because many of them serve as markers for anthropogenic input and consumer behavior. Here, a modular approach for the detection of cocaine is presented, integrating an electrochemical enzyme-linked immunosorbent assay (ELISA) performed on antibody-grafted magnetic beads in a hybrid microfluidic sensor utilizing flexible tubing, static chip and screen-printed electrode (SPE) elements for incubation, recognition, and cyclic voltammetry measurements. A linear response of the sensor vs. the logarithm of cocaine concentration was obtained with a limit of detection of 0.15 ng/L. Within an overall assay time of 25 minutes, concentrations down to 1 ng/L could be reliably determined in water, oral fluids, and urine, the system possessing a dynamic working range up to 1 mg/L.

Molecularly Imprinted Nanoparticles Based Sensor for Cocaine Detection

“…As shown in Table 2, most of the developed biosensors are able to detect cocaine in trace concentration and in a wide range of sample matrices (mostly biological samples). Recently, sub µM limit of detection has been achieved by using bioderived [55,56,59] or hybrid nanozyme receptors [53]. However, the nanoMIPs used in this work guarantees higher stability against environmental factors that usually affect bioderived receptors (protein, antibodies and aptamers), such as high or low temperatures and enzymatic degradation.…”

Aptasensors for Point-of-Care Detection of Small Molecules

“…However, when cocaine is present, the negatively charged AuNPs approach the electrode surface, which results in inhibited electron transfer and the redox probe current decreases [ 59 ]. Even the most recent immunosensor for cocaine biosensing (0.49 nM [ 60 ]) is not able to compete with the LOD of 100 pM exhibited by the presented aptasensor. This drastic improvement of LOD over the past years highlights the high versatility of aptasensing technology.…”

Screen-Printed Electrodes (SPE) for In Vitro Diagnostic Purpose

“…Some scientists found a way to merge the ELISA principle with SPEs in order to construct a hybrid microfluidic sensor capable of detect traces of cocaine in water and body fluids [ 67 ]. New and improved diagnosis methods can also be obtained by combining molecular techniques for the amplification of specific sequences and functionalized screen-printed electrodes to detect the amplified product.…”