title: Extracellular microbial synthesis of biocompatible CdTe quantum dots.
abstract: An efficient bacterial synthesis method to harvest cadmium telluride (CdTe) quantum dots (QDs) with tunable fluorescence emission using Escherichia coli is demonstrated. Ultraviolet-visible, photoluminescence, X-ray diffraction and transmission electron microscopy analysis confirmed the superior size-tunable optical properties, with fluorescence emission from 488 to 551 nm, and the good crystallinity of the as synthesized QDs. A surface protein capping layer was confirmed by hydrodynamic size, zeta potential and Fourier transform infrared spectroscopy measurements, which could maintain the viability (92.9%) of cells in an environment with a QD concentration as high as 2 microM. After functionalization with folic acid the QDs were used to image cultured cervical cancer cells in vitro. Investigations of bacterial growth and morphology and the biosynthesis of CdTe QDs in Luria-Bertani medium containing E. coli-secreted proteins showed that extracellular synthesis directly relied on the E. coli-secreted proteins, and a mechanism for protein-assisted biosynthesis of QDs is proposed. This work provides an economical approach to fabricate highly fluorescent biocompatible CdTe QDs via an environmentally friendly production process. The biosynthesized QDs may have great potential in broad bio-imaging and bio-labeling applications.
authors.affiliation: School of Chemical and Biomedical Engineering and Center for Advanced Bionanosystems, Nanyang Technological University, 70 Nanyang Drive, Singapore 637457, Singapore.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Bao
authors.forename: Zhisong
authors.initials: Z
authors.lastname: Lu
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Cui
authors.forename: Yan
authors.initials: Y
authors.lastname: Qiao
authors.forename: Jun
authors.initials: J
authors.lastname: Guo
authors.forename: James M
authors.initials: JM
authors.lastname: Anderson
authors.forename: Chang Ming
authors.initials: CM
authors.lastname: Li
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis*; D019187:Cadmium Compounds / Q000138:chemical synthesis*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D010316:Particle Size; D045663:Quantum Dots; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013691:Tellurium
chemical_list: D001672:Biocompatible Materials; D019187:Cadmium Compounds; D013691:Tellurium; C028337:cadmium telluride