A point-of-care test for miR-129–5p detection at sub-atto molar concentrations exploiting plasmonic pollen probes combined with complementary DNA

MicroRNAs represent an emerging class of biomarkers that can be correlated with pathological situations. Precise and rapid detection of these biomarkers via Point-of-Care Tests (POCT) can be crucial for early disease identification or monitoring of medical treatments. In this work, an ultra-highly sensitive biosensing strategy for POCT, based on hybrid plasmonic phenomena in pollen-based nanostructures covered by gold, combined with a specific bioreceptor layer, is presented. The miRNA detection is carried out in just 15 min by hybridization, without any target amplification or complex enhancement, simply by diluting the sample in a suitable buffer. As a proof of concept, miR-129–5p is selected as possibly correlated with Atrophic Lateral Sclerosis (ALS) and its detection is performed in buffer and diluted human serum, achieving a limit of detection (LOD) of approximately 100 zM. The proposed POCT is characterized via X-ray Photoelectron Spectrocopy (XPS) and microRAMAN, dose-response curves, selectivity tests, and test in real samples. Moreover, the detection of miR-129–5p in ALS serum patients has been compared with qRT-PCR to highlight the impressive performances obtained with the POCT, just diluting the sample, without any additional treatment. These experimental results will open a new class of POCT with ultra-high sensitivity, ultra-high specificity, and ultra-fast response, all exploiting simple equipment and nanoplasmonic biochips. Specifically, considering the advantages of using diluted real samples and the achieved detection range, the proposed sensing approach could be useful for enhancing cancer diagnosis by detecting mature circulating miRNA in various body fluids.