LSPR based detection based on Hybridization Chain Reaction for miRNA detection

Circulating microRNAs are attracting great attention for their possible role as biomarkers in diagnosis and follow-up based on nucleic acids detection. DNA based biosensors can offer powerful tools at this purpose, overcoming the common drawbacks faced by the lab-based techniques. In DNA based sensing, isothermal amplifications such as Hybridization Chain Reaction (HCR) can lead to the improvement of the sensitivity through enhancement of the response. HCR is a completely isothermal and Enzyme-free self-assembling reaction involving a few species of hairpin-like DNA strands in solution [1]. HCR was previously reported as effective amplification method in the detection of DNA pathogens employing SPR technology [2]. Target detection and the self-assembly on the surface of metallic nanoparticles can be detected monitoring the shift in the LSPR peak due to a change in the refractive index [3]. Herein we report the combination of HCR and a LSPR method based on immobilized gold nanoparticles for the specific detection of microRNAs [4]. The specificity of the assay was obtained by employing a hairpin-like probe, able to efficiently trigger the amplification upon detection of the specific target. Time required for the overall detection was less then 1 h and the limit of detection achieved was improved by 3 orders of magnitude in presence of the HCR amplification. No successful examples of HCR combined with such LSPR based sensing are present in literature. The sensor we propose can offer a solid and robust alternative to the existing methods, does not require in principle specialized operators, components are easily available and cost-effective, allowing point-of-care applications an large-scale production.