A paper-based point-of-care device for the detection of cysteine using gold nanoparticles from whole blood

Abstract

We present a colorimetric probe based on polyvinylpyrrolidone-capped gold nanoparticles (PVP–AuNPs) that is sensitive and selective for cysteine (Cys). A microfluidic paper-based analytical device (μ-PAD) with embedded dried PVP–AuNPs at the polyethersulfone (PES) paper surface is used for Cys detection. When thiol molecules attach to PVP–AuNPs in the presence of Cys, they clump together, and this causes the solution's color to shift from red to blue within 5 minutes. The device is capable of detecting Cys levels between 1.0 μM and 50.0 μM with a limit of detection (LOD) of 0.2 μM under optimized conditions. The stability of the μ-PAD was tested for 100 days, demonstrating re-dispersibility to detect Cys levels in blood. Dried PVP–AuNP–μPADs were integrated with blood plasma separation modules for point-of-care (POC) Cys detection. Consequently, the device shows potential as a self-sustaining, quantification platform with a recovery percentage ranging from 98.44 to 111.9 in clinical samples.