Colored Cellulose Nanoparticles with High Stability and Easily Modified Surface for Accurate and Sensitive Multiplex Lateral Flow Assay.

Decentralized testing using multiplex lateral flow assays (mLFAs) to simultaneously detect multiple analytes can significantly enhance detection efficiency, reduce cost and time, and improve analytic accuracy. However, the challenges, including the monochromatic color of probe particles, interference between different test lines, and reduced specificity and sensitivity, severely hinder mLFAs from wide use. In this study, we prepared polydopamine (PDA)-coated dyed cellulose nanoparticles (dCNPs@P) with tunable colors as the probe for mLFAs. Cellulose nanoparticles (CNPs) were synthesized with uniform spheric shapes and tunable sizes. Dye molecules were loaded on CNPs via a mature industrial dyeing method. The PDA shell provided a reactive surface for facile receptor conjugation and protected the dye from leaking. dCNPs@P displayed a higher signal intensity than gold nanoparticles. They also had higher stability to tolerate salt and varied pH. The dCNP@P-based mLFAs were successfully applied to detect multiple mycotoxins in cereals and determine the levels of inflammatory biomarkers to differentiate between viral and bacterial infections. The tests represented high specificity and accuracy and were more sensitive than the tests using gold nanoparticles. The quantified detection was accessible by measuring the intensities of the colorimetric or photothermal signals. Overall, this study provides a practical system solution for mLFAs based on colored dCNPs@P.