Multi-Component Analysis of Protein- and DNA-Coated Magnetic Nanoparticles Using Electrochemical Impedance Spectroscopy with Interdigitated Electrode Sensors.

The characterization of cancer and other diseases can be aided by the development of reusable electrochemical sensors that provide broad biomarker expression information in real time. We describe an interdigitated electrode (IDE) sensor array that can be used for rapid detection of multiple biomarkers, including human midkine (MDK), HIV gp41 peptide, mAb 7B2, and single-stranded DNA (ssDNA), using electrochemical impedance spectroscopy (EIS) with coated nanoparticles (NPs). These targets represent potential biomarkers for identifying malignant cancer, HIV infection, and DNA mutation. Targets were detected by coating NPs with an antibody, a protein, and ssDNA to capture them from solution. Interacting proteins attached to the nanoparticles were then analyzed with EIS to identify interaction on the surface. In many biological contexts, more than one partner can interact with selected targets, so the determination of the identity of the interacting component is critical for interpretation. In a controlled system, we verify impedance data clusters based on the identity of the protein coated on the surface of the NPs. Data clusters corresponding to protein identity were clearly bifurcated using the impedance spectrum and unsupervised principal component analysis (PCA). NPs clustered based on surface modification, suggesting individual proteins have unique EIS spectral characteristics that can be used for identification.