Recycled Synthesis of Whey-Protein-Capped Lead Sulfide Quantum Dots as the Second Near-Infrared Reporter for Bioimaging Application

Chen, Jun; Kong, Yifei; Feng, Shaoqing; Chen, Chen; Wo, Yan; Wang, Wei; Dong, Yu; Wu, Ziying; Li, Yunxia; Chen, Shiyi

Recycled Synthesis of Whey-Protein-Capped Lead Sulfide Quantum Dots as the Second Near-Infrared Reporter for Bioimaging Application

2016

Owing to their high emission intensity and size-based tunability, lead sulfide (PbS) quantum dots (QDs) have been employed in a broad spectrum of biological applications especially for the second near-infrared (NIR-II) biological imaging. However, the toxicity of Pb²⁺ ions remains an unavoidable risk factor during both preparation and biological applications. Here, we have developed an economical and environmentally friendly synthetic route with a recycle setup to prepare whey-protein-capped PbS QDs. Furthermore, the final Pb²⁺ ions were allowed to react with excess S²– ions and produce nontoxic precipitate in the end, which helped to avoid polluting the environment. After surface modification with protein, both our prepared QDs and the final reaction wastes demonstrated low toxicity in following both in vitro and in vivo experiments. Notably, the conversion efficiency of Pb²⁺ ions into PbS QDs in this study was almost 3 times than that of a one-time reaction without recycle. In addition, each batch of as-prepared PbS QDs featured good stability and bright fluorescence at the NIR-II window in in vivo imaging experiments. Our work shows a novel green strategy for the sustainable synthesis of biocompatible QDs that contain heavy metal, especially for considering the follow-up biological applications.

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