Dry-reagent microfluidic biosensor for simple detection of NT-proBNP via Ag nanoparticles

The diagnosis of many diseases requires monitoring of biomarker levels over a period of time instead of assessing their concentration only once. For example, in case of heart failure determination, the levels of N-terminal prohormone brain natriuretic peptide (NT-proBNP) in blood vary so strongly amongst individuals, that the current procedure of one-time measurement in combination with clinical examination does not allow for accurate assessment of disease severity and progression. Our microfluidic biosensor addresses key characteristics of desirable home-tests which include low limits of detection, small sample volume (less than 10 mL), simple detection strategies, and ready-to-go all-dried long-term stable reagents. Here, electrochemically superior silver nanoparticles (AgNP) were dried directly within the microfluidic channel in a matrix of trehalose sugar doped with Na2SO3 as oxygen scavenger. This successfully prevented AgNP oxidation and enabled dry and ready-to-use storage for at least 18 weeks. Based on this, laser-cut flow chips were developed containing all bioassay reagents needed in a ready-togo dry format. An oxidation-reduction stripping voltammetry strategy was used for highly sensitive quantification of the AgNPs as electrochemical label. This microfluidic biosensor demonstrated limits of detection for NT-proBNP of 0.57 ng mL-1 with a mean error of 6% (n > 3) in undiluted human serum, which is below the clinically relevant cut-off of 1 ng mL-1. This practical approach has the potential to substitute commonly used lateral-flow assays for various biomarkers, as it offers low patient sample volumes hence supporting simple finger-prick strategies well-known also for other electrochemical biosensors, and independence from the notorious variability in fleece fabrication. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The microfluidic biosensor has key characteristics of desirable home-tests, including low limits of detection, small sample volume, simple detection strategies, and long-term stable reagents. It can accurately assess the severity and progression of diseases.