Liquid biopsy represents an advanced non-invasive cancer detection system which analyzes biomarkers found in blood and other body fluids. MicroRNAs (miRNAs) are important biomarkers because they are stable, disease-specific, and have the potential to reflect tumor dynamics. The miRNA-107 plays an important role in the development and progression of prostate cancer (PCa), which makes it a potential target for early diagnosis and monitoring.
A low-cost paper-based electrochemical platform was developed for sensitive miRNA-107 detection, using in-house synthesized gold nanoparticles (AuNPs)-modified screen-printed electrodes (SPEs) to enhance conductivity and surface area. A DNA probe labeled with methylene blue (MB) was immobilized on SPEs via Au-S bonding. It was then rinsed with deionized (DI) water, and blocked with 6-mercapto-1-hexanol (MCH) to lower nonspecific binding. The platform works on “signal-off” square wave voltammetry (SWV) mechanism which decreases current upon addition of target miRNA hybridization. The key parameters AuNPs volume, probe concentration and frequency were optimized. The sensor has achieved detection limits of 1.8 nM in PBS and 1.0 nM in serum, with strong selectivity against non-target miRNAs.
The results show that this approach has a strong potential to be a rapid, reliable and cost-effective tool for PCa detection. It is portable and easy to use, making it suitable for resource-limited settings, and thus a practical solution for early diagnosis and monitoring at the point of care (POC).

Impact statement
POC devices have the potentiality to revolutionize the access to diagnosis and care. Liquid biopsy on chip means opportunity for all patients to get timely responses and interventions. MiRNAs represent very promising biomarkers in the field of liquid biopsy, and their decentralized monitoring can be performed at portable strips, similarly in simplicity to those utilized by diabetes patients to monitor blood glucose.