Microfluidic Impedance Biosensor Chips Using Sensing Layers Based on DNA-Based Self-Assembled Monolayers for Label-Free Detection of Proteins

Abstract

A microfluidic chip for electrochemical impedance spectroscopy (EIS) is presented as bio-sensor for label-free detection of proteins by using the example of cardiac troponin I. Troponin I is one of the most specific diagnostic serum biomarkers for myocardial infarction. The microfluidic impedance biosensor chip presented here consists of a microscope glass slide serving as base plate, sputtered electrodes, and a polydimethylsiloxane (PDMS) microchannel. Electrode functionalization protocols were developed considering a possible charge transfer through the sensing layer, in addition to analyte-specific binding by corresponding antibodies and reduction of nonspecific protein adsorption to prevent false-positive signals. Reagents tested for self-assembled monolayers (SAMs) on gold electrodes included thiolated hydrocarbons and thiolated oligonucleotides, where SAMs based on the latter showed a better performance. The corresponding antibody was covalently coupled on the SAM using carbodiimide chemistry. Sampling and measurement took only a few minutes. Application of a human serum albumin (HSA) sample, 1000 ng/mL, led to negligible impedance changes, while application of a troponin I sample, 1 ng/mL, led to a significant shift in the Nyquist plot. The results are promising regarding specific detection of clinically relevant concentrations of biomarkers, such as cardiac markers, with the newly developed microfluidic impedance biosensor chip.

Label-Free Physical Techniques and Methodologies for Proteins Detection in Microfluidic Biosensor Structures

“…Also, in this work, the optical structure is made of glass and the microfluidic channel is realized in PDMS [ 62 ]. Alsabbagh et al, reported an impedance-based biosensor realized on a glass substrate bonded with a PDMS microfluidic channel [ 63 ]. Bavil et al, used the same material combination to realize a microfluidic microparticle-labeled impedance sensor array for enhancing immunoassay sensitivity [ 64 ].…”

A Review on Microfluidics-Based Impedance Biosensors

“…Before measuring the impedance signal, the authors used dielectrophoretic force to capture nanoprobes (Gal-1 antibody) on the surface of the microelectrode, in order to improve the sensitivity of the sensor. Alsabbagh et al designed a microfluidic impedance biosensor for the detection of myocardial infarction proteins by electrochemical impedance spectroscopy [122]; in particular, Troponin I, which is a biomarker for the diagnosis of myocardial infarction, was targeted. Self-assembled thiolated oligonucleotides tested on gold electrodes were found to perform better, as they improved the performance of the impedance signal.…”

Progress, Opportunities, and Challenges of Troponin Analysis in the Early Diagnosis of Cardiovascular Diseases

“…Electrochemical impedance spectroscopy (EIS) is a technique that relies on its high sensitivity for the quantity and conductivity of the surface absorbing material. As is true for the previous described techniques, EIS is also explored for troponin analysis. − …”