Real-Time Biosensor Platform: Fully Integrated Device for Impedimetric Assays

An impedimetric biosensor platform for bioaffinity assays has been developed that is based on real-time, label-free electrochemical detection performed via a direct interface to electronic digital data processing. The sensor array consists of 15 gold microelectrode pairs (Fig. 1) that are enclosed in three reaction chambers and biofunctionalized with specific probes. The impedance change caused by specific capture of target analyte molecules on the functionalized electrode surface is recorded in real time. The measuring instrument is capable of continuous and simultaneous stimulation and recording of all electrodes on the array. A corresponding mathematical algorithm and a software package for data analysis have been developed. The software performs (i) filtering of the instrument noise, and (ii) extraction of the exponential component of the impedance signal. Thus, the algorithm can quantify both rate of target to probe binding, and target to probe affinity. The described fully integrated platform can be used as a basic research tool for development of various bio-affinity impedimetric assays. To facilitate such applications, we have developed a streamlined manufacturing technology, and a set of assay protocols for detection of microbes based on nucleic acid hybridization. The assay was shown to detect and distinguish between two closely related but different Escherichia coli strains. The assay sensitivity was sufficient for reliable measurements of specific PCR products amplified from microbial genomic DNA. The sensor array platform is adaptable for detection of a wide range of analytes of practical significance, and it has potential for further integration with amplification (i.e. PCR) and sample preparation modules.