Highly Sensitive Naked Eye Detectable Colorimetric Biosensors Made from Macroporous Framework Melamine Foams for Onsite and Simultaneous Detection of Multiple Environmental Hazards in Flowing Through Sensing Systems

Abstract Personal‐use, naked eye‐readable, low‐cost, highly sensitive, and selective biosensors for rapid detection of environmental toxicants are relevant for many application scenarios. Here, the recent developments of highly sensitive and naked eye distinguishable colorimetric sensors by using commercially available melamine foam (MF) as basic sensing materials for instant and volume‐responsive simultaneous detection of multiple targets in fluid systems are reported. The MF possesses a unique reticulated three‐dimensional (3D) macroporous framework structure enabling rapid mass transfer of large biomolecules through the structures in all directions, ensuring easy access of numerous active binding sites of the chemically modified framework to the proteins and target molecules, and subsequently providing significantly increased sensitive and volume‐responsive detection of target molecules in flowing through sensor systems. Promising results in direct, sandwich, and competitive ELISA tests demonstrated the great application potential of the materials. Besides, an additive and simultaneous detection of two targets in one system is achieved by using different layers of the sensor materials in a flowing‐through filtering device. The novel biosensors are expected to significantly improve the sensitivity and broaden the applications of ELISA in the rapid detections of trace amounts of toxicants in liquid and aerosol systems.