Nanoengineered Nonenzymatic Paper‐Based Fluorescent Platform for Pre‐Dilution‐Free and Visual Real‐Time Home Monitoring of Urea for Early Warning of Abnormal Nitrogen‐Based Unhealthy Issues

Abstract Distorted urea levels indicate several liver, kidney, or metabolic diseases; however, traditional clinical urea detection relies on urease‐based methods enslaved to well‐known limitations of high‐price, unstable properties, complicated sample pretreatment and analysis procedures, and difficult visual real‐time monitoring. Herein, nonenzymatic paper‐based fluorescent materials (UFP‐BP) are strategically integrated with an on‐demand fluorescent‐sensor (UFP) self‐aggregated nanoparticle on commercial filter paper for pre‐dilution‐free and visual real‐time urea monitoring. The UFP is synthesized and self‐aggregated into the fluorescent nanoparticles for selective urea recognition. Then, the nanoparticles are interstitially loaded on filter paper to nanoengineer the UFP‐BP, achieving selective quantitative urea detection in the normal concentration range (10–1000 m m ). UFP and UFP‐BP can successfully monitor urea levels in real rat urine, artificial simulants, and milk. The proposed sensing platform, integrated with smartphones, offers accurate, quantitative, nonenzymatic, noninvasive, pre‐dilution‐free, on‐site, rapid, low‐cost, easy‐to‐operate, real‐time visual urea detection in food samples and human body fluids. The designed sensing system can provide early warnings of abnormal nitrogen‐based health issues.