Spatially Directed Biosynthesis of Quantum Dots via Spidroin Templating in Escherichia coli.

Spatially directed synthesis of quantum dots (QDs) is intriguing yet challenging in organisms, due to the dispersed feature of templating biomolecules and precursors. Whether this task could be accomplished by biomolecular condensates, an emerging type of membraneless compartments in cells remains unknown. Here we report synthetic protein condensates for templated synthesis of QDs in bacterium Escherichia coli. This was realized by overexpression of spider silk protein to bind precursor ions and recruit other necessary components, which induced the spidroin to form more β-sheet structures for assembly and maturation of the protein condensates. This in turn enabled formation and co-localization of the fluorescent QDs to "light up" the condensates, and alleviated cytotoxicity of the precursor heavy metal ions and resulting QDs. Thus, our results suggest a new strategy for nanostructure synthesis and deposition in subcellular compartments with great potential for in situ applications.