Semiconductor Nano-molecular Beacon Probes

Recently, semiconductor nanocrystals had attracted many attentions from science researchers. Semiconductor nanocrystals, or quantum dots (QDs), showed unique size-dependent optical properties and were of great interest for applications in light-emitting diode (LED), optoelectronic devices and for biolabeling. Specially, as fluorescence labelings, there is a brand-new, potential applied foreground in the field of nano-biotecnology and biosensor.This paper mainly researched the synthetic route of CdTe quantum dots and the synthesis of molecular beacon (MB) with CdTe (fluorophore) and DABCYL (quencher).1. Synthesis of CdTe. TGA was added as the stabilizer in the solution of CdCl2, under stirring, followed by adjusting the pH to the appropriate values. Then the mixture was refluxed at 90 ℃, we obtained different size of CdTe QDs at different refluxing time. The CdTe QDs grew with the increasing of refluxing time, the peak of absorption and fluorescence emission spectra moved into near-IR at the same tendency. The size of CdTe QDs which were refluxed 2 hours was 2~3nm, characterized by STM and TEM. We researched the growing of CdTe QDs by changing the reaction condition (Cd2+: HTe-, concentration of reactant, quantity of TGA and pH).2. The synthesis of molecular beacon. CdTe QDs, DNA and EDC were added into the phosphate-buffered saline (PBS) solution, reacted for 24 h at room temperature. In this period, carboxyl on the CdTe reacted with amido on DNA. This paper also researched the influence of gel-concentration to DNA electrophoresis, pH to the fluorescence of CdTe, EDC to the conjugation between CdTe and DNA. The fluorescence intensity of MB was lower than pure CdTe, and after the hybridization between the QD-conjugated MB and their target molecules, the fluorescence intensity of MB grew higher than before. This proved that the Forster resonance energy transfer (FRET) was built.