Rapid and home-testable integrated colorimetric sensor for nitrite detection in urine

A portable, rapid and convenient intelligent detection platform for nitrite is proposed based on a polyacrylonitrile NO₂^- colorimetric sensor (PAN-NP) integrated with a smartphone for household urinary nitrite detection. The PAN-NP membrane was prepared from polymer polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) via electrospinning technology to protect the Griess reagent, resulting in prolonged stability for 30 days. Deep Convolutional Neural Network (DCNN) was utilized for color recognition to determine NO₂^- content, and it can detect NO₂^- in artificial urine over a concentration range 5.00-200.0 µM, with recoveries of 95.20-104.00% and accuracy of 99.50%. Compared to commercial test strip reflectance analysis, it lowers the detection limit for NO₂^- from 25.0 µM to 4.65 µM, facilitating earlier detection and treatment of urinary tract infections, and reducing the entire testing time to 2 min without complex preprocessing. This method has been successfully applied to detect nitrite in real urine samples, providing a reliable strategy for point-of-care testing of urinary nitrite and intelligent home health monitoring.