Magnetically assisted colorimetric sensing of insulin and oligonucleotides in biofluids

Colorimetric approaches capable of detecting ultra-low concentrations of specific molecular targets in real sample matrices hold immense significance as point-of-need biosensors, especially in the post-pandemic era. To address this critical need, my dissertation research focuses on a magnetic particle-based colorimetric immunosensor for the picomolar detection of serum insulin by a two-antibody (capture and detection antibodies) sandwich assay format, which offers high selectivity to insulin. Colorimetric detection occurs through the enzymatic oxidation of a chromogenic substrate by the horseradish peroxidase-labeled detection antibody within the immuno-assembly. This method is applicable for detecting insulin in both type-I diabetes and healthy serum samples. Extending the protein immunosensor platform, we have developed a hybridization colorimetric sensor capable of detecting recombinantly synthesized RNA sequences of the SARS-CoV-2 virus as target molecules spiked in undiluted serum and saliva. To enhance sensitivity and further lower detection limits, we have integrated the colorimetric hybridization sensor with an electrochemical transducer for RNA detection and a surface plasmon transducer for small molecule detection.