Detection of urinary microRNA biomarkers using diazo sulfonamide-modified screen printed carbon electrodes.

This paper describes a straightforward electrochemical method for rapid and robust urinary microRNA (miRNA) quantification using disposable biosensors that can discriminate between urine from diabetic kidney disease (DKD) patients and control subjects. Aberrant miRNA expression has been observed in several major human disorders, and we have identified a urinary miRNA signature for DKD. MiRNAs therefore have considerable promise as disease biomarkers, and techniques to quantify these transcripts from clinical samples have significant clinical and commercial potential. Current RT-qPCR-based methods require technical expertise, and more straightforward methods such as electrochemical detection offer attractive alternatives. We describe a method to detect urinary miRNAs using diazo sulfonamide-modified screen printed carbon electrode-based biosensors that is amenable to parallel analysis. These sensors showed a linear response to buffered miR-21, with a 17 fM limit of detection, and successfully discriminated between urine samples (n = 6) from DKD patients and unaffected control subjects (n = 6) by differential miR-192 detection. Our technique for quantitative miRNA detection in liquid biopsies has potential for development as a platform for non-invasive high-throughput screening and/or to complement existing diagnostic procedures in disorders such as DKD.

Electrochemical Detection and Quantification of Lithium Ions in Authentic Human Saliva Using LiMn2O4-Modified Electrodes.

We report an electrochemical sensor for the detection of lithium ions (Li+) in authentic human saliva at lithium manganese oxide (LiMn2O4)-modified glassy carbon electrodes (LMO-GCEs) and screen-printed electrodes (LMO-SPEs). The sensing strategy is based on an initial galvanostatic delithiation of LMO followed by linear stripping voltammetry (LSV) to detect the reinsertion of Li+ in the analyte. The process was investigated using powder X-ray diffraction and voltammetry. LSV measurements reveal a measurable lower limit of 50.0 µM in both LiClO4 aqueous solutions and synthetic saliva samples, demonstrating the applicability of the proposed analytical method down to low Li+ concentrations. Four different samples of authentic human saliva were then analyzed with the established sensing strategy using LMO-SPEs, showing good linearity over a concentration range up to 5.0 mM Li+ with high reproducibility (RSD < 7%) and applicability for routine monitoring purposes. The total time needed to analyze a sample is less than 3 min.