Engineering\nan Ionic Aggregation-Induced Luminescence-Labeled\nFluorescence Lateral Flow Immunoassay for C‑Reactive Protein\nin Human Plasma

The surge of lateral flow immunoassays (LFAs) stimulates\nresearchers\nto explore the novel vibrant aggregation-induced emission luminogen\n(AIEgen)-doped nanoparticles to improve the accuracy and reliability\nof LFAs. However, the loading amount of AIEgens currently used for\nthe LFA in microspheres is limited due to their symmetrical large\nconjugated skeleton structure, which significantly reduces the fluorescence\nbrightness of the signal reporter in the LFA. Herein, an ionic AIEgens\nwith a donor–acceptor type was developed as the signal reporter\nof the LFA for C-reactive protein (CRP). Ionic AIEgens are unable\nto enter the hydrophobic cavity of polystyrene nanoparticles (PS)\nbecause of their low hydrophobic nature. By altering ionic AIEgens\nwith extended alkyl chains, it is possible to increase their hydrophobicity,\nthereby potentially increasing the loading capacity within PS. Notably,\nthe fluorescent nanoparticles (denoted as AIE<sub>TPA</sub>NPs) formed\nby embedding (<i>E</i>)-4-(4-(diphenylamino)styryl)-1-octadecylpyridin-1-ium\niodide (TPA) in PS showed orange-red fluorescence emission and have\nhigh fluorescence quantum yield. Anti-CRP antibody (mAb1) could be\neffectively conjugated to the surface of AIE<sub>TPA</sub>NPs by an\namino-carboxyl reaction, resulting in AIE<sub>TPA</sub>NPs-mAb1. The\nAIE<sub>TPA</sub>NPs-mAb1 exhibited a fluorescence emission at 613\nnm, a point detectable by the naked eye with minimal background interference.\nThe entire analysis was accomplished in just 10 min, achieving a limit\nof detection of 4.06 ng/mL for CRP. The AIE<sub>TPA</sub>NPs-mAb1-based\nLFA demonstrates excellent stability and specificity and fully meets\nthe requirements for clinical diagnosis.