Improved on-chip impedimetric immuno-detection of subpopulations of cells toward single-cell resolution

Abstract

International audienceImpedance spectroscopy has gained interest for the quantitative detection of specific cells mainly due to a label-free detection and their miniaturization capability required for integration on chip and development of point-of-care diagnostics. In this paper, we report the study of impedimetric microfluidic devices with improved sensitivity targeting the immuno-detection of cells. The sensitivity of our system was evaluated in terms of the capacity of the electrodes to trap monocytes by immune-reaction with CD14 antibody immobilized on micro-electrode surface. All measurements were performed in faradic mode using a redox probe. The sensitivity was evaluated as a function of the impedance increase recorded at 100 Hz caused by the insulating character of the cell trapped on electrodes. Analyses first confirmed that the sensing performances were significantly improved by using microfluidic. This increase could originate from an increase in the probability of cell trapping and a better organization of cells on the electrode due to the laminar flow. The great sensitivity was recorded with interdigitated electrodes for which the influence of the gap value was evaluated. The maximum sensitivity was reached with the smallest inter-electrodes gap tested (50 µm). This performance was in part attributed to the redox cycling taking place between neighboring fingers that was strongly affected when cells were trapped on the electrodes edges. Furthermore we also demonstrate that the slice of cell concentration for which the sensitivity is maximized is correlated to the area of electrodes. Moreover, the smallest area of interdigitated electrode (0.1 mm length) allowed the detection of as low as 5 cells per m

3D Interdigitated Vertically Aligned Carbon Nanotube Electrodes for Electrochemical Impedimetric Biosensing

“…VACNTs have previously been used as IDEs for capacitors with VACNT heights ranging from 34 to 70 μm with a 20–35 μm gap between electrodes. − Although such tall heights are not typically reported for electrochemical biosensors, our previous work with an oral cancer biomarker had a VACNT electrode height of about 75 μm and gap of 25 μm . Smaller gap width between tall VACNT electrodes may likely improve sensitivity, a relationship that has previously been shown with planar electrodes …”

“…Microfluidic IDE sensors have also been shown to be more sensitive than static IDE sensors. 25 The exposed Cr leads provide the means for electrical contact within the plane of the sensor substrate to allow a 3D printed microfluidic channel to be clamped over the sensor (see also Figure S5, Supporting Information). Although fluorescence showed better coverage using the microchannel ( Figure S6, Supporting Information), initial electrochemical tests with the microfluidic channel demonstrated little improvement over static F-SA and F-biotin binding.…”

“…13 Smaller gap width between tall VACNT electrodes may likely improve sensitivity, a relationship that has previously been shown with planar electrodes. 25 Previous IDE sensors were made entirely of VACNTs, including the interdigitated fingers and the electrical leads. 13 A redox sensor for dopamine was constructed with a VACNT electrode height of 0.66 µm and 3 µm gap, where the fingers of VACNT IDEs were grown directly on metallic electrical leads.…”

“…This work performs a parameter study to determine the impact of VACNT height, gap width, and electrode geometry pattern (IDE vs SE) on the sensitivity of VACNT biosensors. The topic of electrode height is emphasized because the trend of gap width has previously been explored for planar electrodes . The previous oral cancer sensor was made of all VACNT, but here, an underlying chromium layer is used for electrical leads to improve stability, reduce internal resistance, and provide a potential path for integration with a microfluidic channel.…”

Functional Polymers Structures for (Bio)Sensing Application—A Review

“…Due to this, in this review we describe LOC devices based on the impedimetric method, where polymers and biological receptors are present. Manczak et al reported an impedimetric microfluidic device for sensitive immune-detection of cells [129]. The sensitivity of the described method was estimated as the ability of the electrodes to trap monocytes by specific immune-reaction with CD14 antibody immobilized on the modified-electrode surface, resulting in a change in impedance The electrode had been modified with mixture of 11-mercaptoundecanoic acid (MUA), mercaptohexanol (MH) and a mixture of aqueous solutions of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl-carbodiimide) (EDC).…”