Assemblable Paper-Based Microfluidic Devices Functionalized with Silver Nanoparticles: Advances and Prospects in Solid‑Phase Spectroscopy and Digital Colorimetry

This paper discusses the opportunities and prospects for apassemblable plying assemblable paper-based microfluidic systems modified with silver nanoparticles of various morphologies to the determination of biologically active compounds by diffuse reflectance spectroscopy and digital colorimetry. The combination of the adsorption properties of cellulose with the unique optical properties of silver nanoparticles, arising from the phenomenon of localized surface plasmon resonance, within a single analytical device, is shown to offer a promising platform for the development of resource-efficient and rapid chemical analysis test systems. The applicability of the developed paper-based microfluidic systems was demonstrated for the determination of biologically active compounds representing three priority classes: peroxides (using hydrogen peroxide as a model analyte), organic sulfur-containing compounds (using cysteamine as a model analyte), and flavonoids (using rutin as a model analyte). The morphology of the silver nanoparticles was found to influence the sensitivity and selectivity of the colorimetric determination of the target compounds. The feasibility of recording the analytical signal using a smartphone camera was also demonstrated. The achieved limits of detection ranged from 0.2 to 2.3 μg for diffuse reflectance spectroscopy and from 0.4 to 2.0 μg for digital colorimetry, depending on the nature of the analyte. The proposed approach was successfully applied to the determination of peroxides, biologically active organic sulfur-containing compounds, and flavonoids in pharmaceutical products and dosage forms, dietary supplement samples, as well as cosmetic products.