Naphthalimide-based AIE probe for direct and rapid detection of HSA in urine sample

Human serum albumin (HSA) is an important indicator for diagnose of renal injury. In this study, an AIE-active fluorescent probe (NI2) based on hindered amine modifying 1,8-naphthalimide molecule was designed for directly detecting HSA in urine samples without any pretreatment. NI2 exhibits red AIE fluorescence around 600 nm which is longer than previous reports based on 4-amino-1,8-naphthalimide derivatives contributed to its twisted intramolecular charge transfer (TICT) structure. An N-methyl pyridium cation group was introduced to interact with HSA for forming the aggregates with the "turn on" signal. Interestingly, the emission enhancement factor (I/I0) can increase obviously by addition of a mount of heparin. An optimized working medium with 5 mu M heparin as additive was provided in which NI2 could detect HSA within a wide concentration range (0-10 mu M) in the raw urine samples without any pretreatment. This protocol is rapidly (<60 s) and sensitively (LOD = 0.254 mu M) that meets the requirement of liquid biopsy technology.