Biomarker assays provide early detection and identification of disease, which enables timely delivery of individualized treatment strategies to patients. These assays also have the potential to track progression, regression, and recurrence of disease. Detection is typically achieved using an enzyme-linked immunosorbent assay platform, but such assays suffer from poor detection limits and a restricted dynamic range.

The small molecule immunoassay facilitates label-free analyte detection with antibodies. It utilizes two non-linear methods – enhanced second harmonic correlation spectroscopy and enhanced second harmonic imaging – for detection and identification of small molecules. Surface immobilized antibody arrays detect the small molecules, eliminating the need for a second antibody. The assay can be used for diagnostic testing, environmental screening, and drug screening.