Universal Detector Measures Major Biomolecule Classes

A new electrochemical assay measures all major types of biomolecules, including small molecules, nucleic acids, and proteins, Shana O. Kelley and coworkers at the University of Toronto report (Nat. Chem., DOI: 10.1038/nchem.1367). Other electrochemical sensors that measure electrostatic changes have been suitable for charged biomolecules but are insensitive to small molecules. The “neutralizer displacement” assay avoids that problem. Kelley and coworkers tethered an array of ligand-binding DNA probe molecules to an electrode surface along with neutralizer molecules, which are conjugates of peptide nucleic acids and cationic amino acids. These neutralizers bind to and suppress the charge of the DNA probe molecules. Intentional base-pair mismatches in the probe-neutralizer complex ensure that analytes bind the probe more tightly than the neutralizer does. Analyte binding displaces the neutralizer and changes the electrode surface charge, which is measured with an electrochemical catalytic reporter system. Kelley and coworkers detected a range of clinically relevant analytes, including nucleic acids, thrombin, adenosine triphosphate, cocaine, and even bacterial cells.