Specific and Sensitive Determination of Folic Acid by Label-Free Chemosensors with Microscope Glass Slips as Single-Use Consumables

Abstract

Folic acid (FA) and its other forms known as folates are small molecules vital for humans. The high demand for increasingly sensitive methods of measuring folate concentrations is due to the fact that abnormal levels of FA cause severe health disorders. Besides, folates are used as recognition molecules in targeted drug delivery. The majority of FA measuring techniques are rather expensive, laborious, sometimes not sufficiently sensitive and specific, and often employ consumables that are too costly to be single-use for routine medical diagnostics. Here, we present a procedure for transformation of a simple microscope cover glass slip without deposition of any metal or dielectric films into a cost-efficient chemosensor chip interrogated by spectral correlation interferometry for highly sensitive measurements of the concentration of small molecules, as well as a feasibility study of long-term monitoring of such molecules in a flow mode. The obtained chips were tested for folate detection. The highly specific and sensitive measurements can be performed in real-time in a wide dynamic range of 0.9–220,000 pM. The developed method and single-use consumables are promising for concentration measurements of low molecular weight substances in pharmaceuticals and in vitro diagnostics.

Keywords

• optical chemosensors
• label-free interferometry
• real-time detection
• small molecules
• haptens
• competitive assay