Dual-modal background-free sensing platform with ultrafast kinetic response for propofol visual detection in body fluids

Rapid and quantitative detection of propofol in body fluids is of great significance in ensuring medical safety and curbing drug abuse. Fluorimetry is an effective method for the detection of propofol. However, background fluorescence generated by short-wavelength excitation compromises detection sensitivity, and slow kinetic responses lead to prolonged detection time. In this study, a background-free, rapid-response upconversion nanoprobe excited by near-infrared light was developed for the quantitative detection of propofol. Leveraging lanthanide-doped upconversion nanoparticles (UCNPs) and the ultrafast chromogenic reaction between propofol and diazonium salts, the chromogenic product can selectively quench green upconversion luminescence (UCL) within 1 s while preserving red UCL. Consequently, a highly sensitive, multi-signal output sensing system with ultrafast kinetic response capabilities was established. The designed sensing platform systematically eliminated autofluorescence, thus enhancing detection sensitivity. Under optimized conditions, the limit of detection (LOD) was determined to be 105 nM for colorimetric mode and 34 nM for luminescent mode. A portable sensing device was further fabricated, exhibiting excellent sensitivity and rapid detection capabilities, which offered a novel approach for detecting drug concentrations in human body fluids. This study provides a new approach for the rapid on-site detection of drug concentrations in body fluids.