A Fully Integrated, Ready-to-Use Distance-Based Chemosensor for Visual Quantification of Multiple Heavy Metal Ions

• Published in: Analytical chemistry (Washington) 2022-11, Vol.94 (46), p.15925-15929
• Main Authors: Wang, Gaobo, Li, Jiaheng, Wu, Siying, Jiang, Tianyi, Chen, Ting-Hsuan
• Format: Article
• Language: English
• Subjects: Biosensing Techniques - methods; Capillary flow; Chemical sensors; Chemistry; Chemoreceptors; Contamination; Copper; Deoxyribozymes; DNA, Catalytic - chemistry; Drinking water; Gravity; Heavy metals; Ions - chemistry; Lead; Liquid flow; Magnetic separation; Magnetic separators; Metal concentrations; Metal ions; Metals, Heavy; Microfluidics; Microparticles; Polystyrene; Polystyrene resins; Selectivity; Water; Water analysis; Water sampling
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.2c04712

Point-of-care devices offering quantitative results with simple steps would allow great useability for untrained end-users. Here, we report a ready-to-use chemosensor integrating automatic sample metering, on-chip reaction, gravitational–magnetic separation, and a distance-based readout for visual quantification of multiple heavy metal ions. Deoxyribozymes (DNAzymes), probe-modified magnetic microparticles (MMPs), and polystyrene microparticles (PMPs) are preloaded into a microfluidic chip and freeze-dried. After the water sample is collected with automatic volume metering, the particles are resuspended, and the MMPs and PMPs hybridize with DNAzyme at its two termini, forming the “MMPs-DNAzyme-PMPs” structure. When target metal ions are present, the DNAzymes are cleaved, yielding an increased number of free PMPs. All on-chip reactions are controlled by stopping the liquid flow at capillary valves and bursting it with hand-controlled tilting. Using the chip with a gravitational–magnetic separator, the free PMPs are separated from “MMPs-DNAzyme-PMPs” and accumulate into the trapping channel with a nozzle, forming a visual bar with growing distances proportional to the concentration of target metal ions. The achieved limit of detection (LOD) values for Cu2+ (103.1 nM), Pb2+ (69.5 nM), and Ag+ (793.6 nM) are below the maximum contamination levels. High selectivity of 100-fold, 200-fold, and 20-fold against interference is obtained. Moreover, by integrating three identical channels in parallel, simultaneous detection of the above-mentioned heavy metal ions in fresh and tap water samples is also achieved with high accuracy. Together, this fully integrated and easily operated platform embodies excellent potential for rapid, on-site sensing by unskilled users.