Low-Cost and Portable Biosensor Based on Monitoring Impedance Changes in Aptamer-Functionalized Nanoporous Anodized Aluminum Oxide Membrane

Abstract

We report a low-cost, portable biosensor composed of an aptamer-functionalized nanoporous anodic aluminum oxide (NAAO) membrane and a commercial microcontroller chip-based impedance reader suitable for electrochemical impedance spectroscopy (EIS)-based sensing. The biosensor consists of two chambers separated by an aptamer-functionalized NAAO membrane, and the impedance reader is utilized to monitor transmembrane impedance changes. The biosensor is utilized to detect amodiaquine molecules using an amodiaquine-binding aptamer (OR7)-functionalized membrane. The aptamer-functionalized membrane is exposed to different concentrations of amodiaquine molecules to characterize the sensitivity of the sensor response. The specificity of the sensor response is characterized by exposure to varying concentrations of chloroquine, which is similar in structure to amodiaquine but does not bind to the OR7 aptamer. A commercial potentiostat is also used to measure the sensor response for amodiaquine and chloroquine. The sensing response measured using both the portable impedance reader and the commercial potentiostat showed a similar dynamic response and detection threshold. The specific and sensitive sensing results for amodiaquine demonstrate the efficacy of the low-cost and portable biosensor.

Keywords: amodiaquine sensing; aptamers; low-cost impedance monitoring; malaria; point-of-care biosensor; point-of-care sensor.

Figure A1

DRT parameters setup shown in the MATLAB panel.

Figure 1

(A) SEM image of the gold-coated membrane, (B) Teflon cells for electrochemical experiments and the four-electrode setup, (C) sensor structure with four electrodes (RE—reference electrode, WE—working electrode, CE—counter electrode) during the process of aptamer immobilization and the impedance measurement.

Figure 2

Evaluation kit of the ADuCM350-based impedance reader and the connection between the reader and the electrochemical cell.

Figure 3

Impedance of the OR7-functionalized membrane exposed to no AMQ and 250 nM AMQ inside the electrochemical cell: (A) Bode plot measured using a commercial potentiostat, (B) Bode plot measured using a low-cost impedance reader, (C) DRT deconvolution of the Bode plot in (A), and (D) DRT deconvolution of the Bode plot in (B).

Figure 4

Sensing result of AMQ using both (A) potentiostat reference 600+ and (B) the ADuCM350-based impedance reader. AMQ LOD uses (C) potentiostat 600+ and (D) the ADuCM350-based impedance reader.

Figure 5

(A) Quenching mechanism of AMQ binding with OR7, (B) charge accumulation of CHQ physisorption onto NAAO membrane surface. (⊝ indicates surface negative charge and ⊕ indicates positive charge of AMQ and CHQ).