Acid-stimulated bioassembly of high-performance quantum dots in Escherichia coli

Abstract

Biogenic quantum dots (Bio-QDs) with good luminescence properties and inherent biocompatibility are highly desirable for life science studies and hybrid solar-to-chemical production applications, but controlled bio-assembly is still challenging. Here, we report a facile and effective acid stimulation strategy that enables drastically enhanced production of CdS_xSe_1−x Bio-QDs in Escherichia coli. Lowering the pH from 7.5 to 4.5 resulted in a 25-fold higher Bio-QDs yield within 3.5 hours and significantly improved the Bio-QDs' fluorescence lifetime (133 ns) and quantum yield (7.3%) to a level far greater than those of the existing Bio-QDs. The enhanced Bio-QD production was associated with an increased production of reduced thiols in response to acid stress that trigger reactive oxygen species generation. The abundant reduced thiols in turn stimulated the uptake and transformation of Cd and Se into Bio-QDs. The resulting Bio-QDs, with uniform size (3.3 ± 0.2 nm), outstanding fluorescence properties and high biocompatibility, showed good performance for non-destructive bioimaging of zebrafish in vivo. Our work opens a facile and generally applicable avenue for boosting Bio-QD assembly by imposing appropriate environmental stress, which may bring Bio-QDs a step closer to practical application.