Nano‐in‐Micro Smart Hydrogel Composite for a Rapid Sensitive Immunoassay

A smart composite bead‐based immunosensor with an intrinsic signal enhancement capability is developed using droplet microfluidics. The temperature‐induced volume phase transition properties of poly(N‐isopropylacrylamide) allows the signal concentration of the nanosensors embedded within the microgel matrix in a rapid manner (≈5 s). A simple yet highly effective detection method is therefore achieved without complex enzyme‐based signal amplification.

Abstract

Immunoassays are an important tool in various bioanalytical settings, such as clinical diagnostics, biopharmaceutical analysis, environmental monitoring, and food testing. An enzyme‐linked immunosorbent assay (ELISA) is usually used to amplify immunoassay signals; however, it requires labor‐intensive and time‐consuming procedures, which hinders its application to rapid cytokine detection. In this study, a nano‐in‐micro composite system, where immunosensing polystyrene beads (≈320 nm) are incorporated within a stimuli‐responsive microgel matrix (≈40 µm) via microfluidics, is investigated. The intrinsic volume phase‐transition change properties of the smart microgels allows an enzyme‐free enhanced immunoassay, enabling instant enhancement in signal‐to‐noise ratios of ≈5‐fold. This nano‐in‐micro hydrogel composite offers a simple yet highly effective method for sensitive and multiplexed cytokine analysis without complex enzyme‐based signal amplification steps, greatly benefitting advanced immune medicine.

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