Smartphone-assisted bioenzyme-nanozyme-chromogen all-in-one test strip with enhanced cascade signal amplification for convenient paraoxon sensing

Monitoring of pesticide residues in food and environmental matrices is undoubtedly crucial to guarantee food safety and ecological health, yet how to realize their sensitive and convenient detection is still challenging. Herein, we propose an all-in-one test strip that elaborately integrates bioenzyme, nanozyme and chromogen together, and achieve the highly sensitive and convenient sensing of pesticide residues assisted by a smartphone. A sequential self-assembly strategy was first explored to acquire an integrative bioenzyme-nanozyme-chromogen assembly, and then the assembly was confined in a biocompatible hydrogel to construct the test strip. Thanks to both the proximity and confinement effects, a ∼1.2-fold improvement of the cascade catalytic efficiency was gained to benefit high-sensitivity detection. More importantly, since all the sensing elements, including target recognition units and signal amplification modules, were rationally integrated in the test strip, detection operation was significantly simplified, making it possible for in-field rapid analysis. Besides, the microenvironment provided by the alginate hydrogel carrier endowed the test strip with an excellent sensing stability. By taking paraoxon as a typical pesticide, high-performance detection of the target was accomplished via the smartphone-assisted all-in-one test strip. Moreover, the test strip was successfully applied for paraoxon detection in various real samples and exhibited good correlations with commercial kits, demonstrating its great prospect for practical applications. Our work not only offers a new tool for the high-sensitivity and convenient monitoring of pesticide residues, but will also inspire the development of efficient multi-enzyme sensing platforms.