Paper-based device for Colorimetric Detection of Ovarian Cancer Biomarker miRNA-665
Institutions: Swiss Federal Institute of Technology Zürich (ETH)
Jessica Ooi Sui Ying is a hall tutor at University of Nottingham Malaysia Campus, whose current project revolves around developing an assay to detect the presence of an ovarian cancer biomarker called miRNA-665 in human serum. MicroRNAs (miRNA) are short ribonucleic acids (RNA) which have emerged as potential cancer biomarkers. However, these are usually present in small amounts in the bloodstream. Therefore, miRNAs must first be amplified before they can be detected. This may be achieved using microarrays or reverse transcriptase polymerase chain reaction (RT-PCR). Unfortunately, these standard methods are time-consuming, laborious and require special equipment and expertise. Unlike these methods, my proposed assay aims to eliminate the need for complicated protocols, expensive equipment and highly skilled personnel.
The assay will utilise specially-designed DNA probes to recognise and amplify this miRNA. If miRNA-665 is present, the DNA probes will be triggered to assemble into larger branched DNA in a process called hybridisation chain reaction (HCR). For the detection step, the assay will exploit a special optical property of gold nanoparticles (AuNPs) and the difference in its interaction with short DNA probes compared to large, branched double-stranded DNA structures. Due to a phenomenon called localised surface plasmon resonance, gold nanoparticles that are dispersed in solution appear red but turn blue when aggregated. Conveniently, mixing the branched DNA with AuNPs is expected to cause the latter to aggregate in the solution yielding a visible colour signal that indicates presence of miRNA-665.
The MAKNA Cancer Research Award 2020 is currently funding Jessica’s research to
a) establish the utility of combining DNA probes and AuNPs in a tube-based assay
b) validate the assay with serum samples and c) compare the assay sensitivity with that of a standard method (RT-PCR).
As a sequel to this, Jessica is proposing to transfer the aforementioned mechanism to a paper-based analytical device (PAD) that also generates quantifiable colour signals. This will further bolster its use as a biosensor in both rural and urban settings. To help her achieve this, she hopes to learn essential skills during an attachment with a research group abroad renowned for developing paper-based diagnostic technologies.