Spatially Confined/Ligand-Directed Ultrabright NIR-AIE Nanoprobe for In Vitro Rapid Detection and In Situ Imaging of Bacterial Septic Arthritis.

Bacterial infection is a major threat to joint surgery and can lead to amputation or death. However, advanced tools for early, rapid, and accurate identification of joint-infecting bacterial species remain limited. Here, we report a universal strategy for fabricating ultrabright near-infrared (NIR) AIEgen fluorescent probes (PPANPs) that enable lateral flow assay (LFA)-based rapid bacterial identification in joint fluid before surgery, as well as in situ imaging diagnosis and photothermal antibacterial intervention in the joint cavity. Structurally, PPANPs display a core-shell-shell architecture, in which aggregated NIR AIEgens form the fluorescent core, NIR lead sulfide (OA-PbS) forms the inner shell, and poly(maleic anhydride-alt-1-octadecene) (PMAO) forms the outer shell. This spatially confined design combines physical confinement, ligand-mediated molecular organization, and cooperative luminescence within the PbS-AIE hybrid nanoassembly, promoting compact and ordered AIE packing and thereby enhancing NIR fluorescence intensity, quantum yield, and photothermal performance compared with conventional embedding methods. s a diagnostic platform, PPANP-labeled LFA achieves 100% sensitivity for Staphylococcus aureus (S. aureus) identification within 10 min, outperforming standard plate culture (>96 h). Moreover, PPANPs enable rapid in situ imaging of S. aureus infection in mouse joints within 30 min and exhibit potent photothermal antibacterial activity in vitro under low-power-density laser irradiation.