Progress of Interdigitated Array Microelectrodes Based Impedance Immunosensor

A review on impedimetric immunosensors for pathogen and biomarker detection

Since the discovery of antibiotics in the first quarter of the twentieth century, their use has been the principal approach to treat bacterial infection. Modernized medicine such as cancer therapy, organ transplantation or advanced major surgeries require effective antibiotics to manage bacterial infections. However, the irresponsible use of antibiotics along with the lack of development has led to the emergence of antimicrobial resistance which is considered a serious global threat due to the rise of multidrug-resistant bacteria (Wang et al. in Antibiotic resistance: a rundown of a global crisis, pp. 1645-1658, 2018). Currently employed diagnostics techniques are microscopy, colony counting, ELISA, PCR, RT-PCR, surface-enhanced Raman scattering and others. These techniques provide satisfactory selectivity and sensitivity (Joung et al. in Sens Actuators B Chem 161:824-831, 2012). Nevertheless, they demand specialized personnel and expensive and sophisticated machinery which can be labour-intensive and time-consuming, (Malvano et al. in Sensors (Switzerland) 18:1-11, 2018; Mantzila et al. in Anal Chem 80:1169-1175, 2008). To get around these problems, new technologies such as biosensing and lab-on-a-chip devices have emerged in the last two decades. Impedimetric immunosensors function by applying electrochemical impedance spectroscopy to a biosensor platform using antibodies or other affinity proteins such as Affimers (Tiede et al. in Elife 6(c):1-35, 2017) or other binding proteins (Weiss et al. in Electrochim Acta 50:4248-4256, 2005) as bioreceptors, which provide excellent sensitivity and selectivity. Pre-enrichment steps are not required and this allows miniaturization and low-cost. In this review different types of impedimetric immunosensors are reported according to the type of electrode and their base layer materials, either self-assembled monolayers or polymeric layers, composition and functionalization for different types of bacteria, viruses, fungi and disease biomarkers. Additionally, novel protein scaffolds, both antibody derived and non-antibody derived, used to specifically target the analyte are considered.

An interdigital array microelectrode aptasensor based on multi-walled carbon nanotubes for detection of tetracycline

In this study an impedance aptasensor was designed for sensitive, selective, and fast detection of tetracycline (TET) based on an interdigital array microelectrode (IDAM). The IDAM was integrated with impedance detection to miniaturize the conventional electrodes, enhance the sensitivity, shorten the detection time, and minimize interfering effects of non-target analytes in the solution. Due to their excellent conductivity, good biocompatibility, the multi-walled carbon nanotubes (MWCNTs) were used to modify the IDAM to immobilize TET aptamer effectively. The proposed aptasensor produced a sensitive impedance change which was characterized by the electrochemical impedance spectroscopy (EIS). With the addition of TET, the formation of TET-aptamer complex on the surface of MWCNTs modified electrode resulted in an increase of electron transfer resistance (R _et). The change of R _et depends on the concentration of TET, which is applied for the quantification of TET. A wide linear range was obtained from 10^-9 to 10^-3 M. The linear regression equation was y(ΔR) = 21.310 × x(LogC) (M) + 217.25. It was successfully applied to detect TET in real milk samples.

Impedimetric Immunosensing in a Porous Volumetric Microfluidic Detector

A sensitive and rapid impedemetric immunosensor is demonstrated utilizing porous volumetric microfluidic detection elements and silver enhanced gold nanoparticle probes. The porous detection elements significantly increase capture probe density and decrease diffusion length scales compared to conventional planar sensors to improve target capture efficiency and enhance impedance signal. In this work, a packed bed of silica beads functionalized with antibody probes serves as a porous sensor element within a thermoplastic microchannel, with an interdigitated gold electrode microarray used to measure impedance changes caused by the concentration dependent formation of silver aggregates. The measured impedance change is independent of electrode spacing, enabling a device with low resolution electrodes to achieve a sandwich immunoassay detection limit between 1-10 ng/mL with a 4-log dynamic range, with a total assay time of 75 min.

Aptasensors modified by antimony tin oxide nanoparticle-chitosan based on interdigitated array microelectrodes for tetracycline detection

Aptasensors modified by antimony tin oxide nanoparticle-chitosan (nano ATO-CS) based on interdigitated array microelectrodes (IDAMs) were developed for the detection of tetracycline.