Using Living Cells As A Controllable Biosynthesizer Of Quantum Dots For Biodetection

The well-known nanotechnology that has been developed rapidly in recent decades is expected to be one of the hottest areas in the future. The synthesis and application of florescent semiconductor nanocrystals that were so called quantum dots (QDs) have attracted much attention in lots of different areas. Though the conventional synthesis of nanomaterials could obtain the high quality QDs, still many problems exist in conventional method of synthesis, which usually requires high temperatures (around 200-300℃) and the use of combustible, explosive,and toxic organic reagents, such as trioctylphosphane (TOP) or trioctylphosphane oxide (TOPO), under an oxygen-and water-free atmosphere. Such synthesis methods are environmentally unfriendly, inefficient, and can be unsafe. QDs synthesized by these methods must be water-solubility modified before applications, which restricted the development of the QDs.In recent years, natural and highly efficient biosystems have exhibited their potential to establish a platform for fabrication of materials to address these problems. Inspiring from the biosystem and biomimicking the individual functions of organics will help humanity to realize the intelligent design and fine-tune the properties of materials. Based on these, this thesis has tried to solve seemingly intractable chemical problems through biology as the following:(1) A novel route for the controllable biosythesis of fluorescent CdSe QDs has been demonstrated by aboratively coupling unrelated intracellular biochemical reactions in an appropriate space and time sequence. By such a method, CdSe QDs, emitting at a variety of single fluorescence wavelengths, can be intracellularly, controllably synthesized at just 30℃instead of at 300℃with combustible, explosive, and toxic organic reagents, demonstrating an example of how to solve seemingly intractable chemical synthesis problems through biology.(2) Based on the work of the living yeast cells as a controllable biosynthesizer for fluorescent quantum dots, the N-Azidoacetyl-a,b-D-glucamine was used as a part of the carbon sources for incubating the yeast cells to obtained the GluNAz-yeast cells through the sugar metabolism by the living yeast cell themselves. This GluNAz-fluorescent yeast cells could be used for the "click" reactions with alkynyl FITC by Cu(I) catalyst. By this approach, the "clickable" fluorescent yeast biodetection has been constructed and the synthesis and modification of QDs could be realized simultaneously, which is a notable breakthrough in the nanoscientific area.(3) Based on the work of the living yeast cells as a controllable biosynthesizer for fluorescent quantum dots, the metabolism of Na2Se03 and detoxification of Pb2+ were biomimic in vitro to obtain the appropriate valence states of Se and Pb for synthesize the PbSe nanocubes. By this approach, the size tunable and shape controlled PbSe nanocubes could be synthesized at just 90℃in aqueous phase instead of at 200℃with combustible, explosive, and toxic organic reagents.(4) HPLC-MS method was firstly used to demonstrate the mechanism of the PbSe nanocubes with XRD and TEM. The key factor in the shape-control of PbSe nanocubes has been confirmed. The crystallization pathway also has been demonstrated as kinetic-controlled non-classical crystallization, which is similar with the natural biogenic minerals in living cells. This result implied that the biochemical reaction mimicking in vitro is similar with that of the living cells.