Direct Water-phase Synthesis of Lead Sulfide Quantum Dots Encapsulated by β-Lactoglobulin for In Vivo Second Near Infrared Window Imaging with Reduced Toxicity

Compared to traditional fluorescence imaging in the visible and NIR-I regions (700-900 nm), second near infrared window (NIR-II, 1000-1400 nm)-based optical imaging offers reduced photon scattering, deeper tissue penetration and lower auto-fluorescence. Despite the excellent imaging capabilities, current NIR-II probes have not yet reached their full potential for biomedical imaging applications due to weak quantum yields, low water solubility and suboptimal biocompatibility. To address these factors, NIR-II fluorescent PbS quantum dots (QDs) encapsulated by β-lactoglobulin (LG) are conveniently prepared via a one-pot microwave-assisted synthesis. The as-prepared LG-PbS QDs feature excellent aqueous dispersibility, high quantum yield and favorable biocompatibility. In vivo imaging experiments show that LG-PbS QDs are superbly suitable for real-time and high-resolution in vivo imaging; these features make these QDs extremely promising for use in various bioimaging applications.