[Fluorescence resonance energy transfer between gentamycin and water-soluble CdTe QDs]

The water-soluble CdTe quantum dots (QDs) were prepared by using mercaptopropionic acid (MPA) as stabilizer in the aqueous system. Fluorescence resonance energy transfer (FRET) system was constructed between gentamycin (acceptor) and water-soluble CdTe QDs (donor). The maximal emission wavelength was 690 nm, and the line width of the fluorescence spectrum was very narrow (with the full width at half-maximum about 10 nm) and symmetric. The transfer of resonance energy from the CdTe QDs to gentamycin (GT) resulted in the fluorescence quenching of the QDs, corresponding to the increase in the concentration of GT. Several factors that impacted the fluorescence spectra of the FRET system, such as the excitation wavelength (305-425 nm), pH(5.0-11.0), ions (0-0.1 mmol x L(-1) PBS; 0-0.5 mmol x L(-1) NaCl), time (1-120 min), temperature (5-50 degrees C), and concentration of GT (2-80 mg x L(-1)), were investigated and refined. The linear ranges of GT concentration were 2-20 mg x L(-1), r = 0.986 7. Fourier transform infrared spectroscopy (FTIR) and high-performance liquid chromatography (HPLC) were used for confirming the chemical construction and relative specificity, respectively. The results indicated that sulfur and oxygen atoms in MPA molecules took part in coordination with rich Cd2+ on the surface of the nanoparticles. Meanwhile the results also demonstrated that the hydrogen bond between carboxyl of mercaptopropionic acid on the surface of quantum dots and amidocyanogen of GT mainly contributes to combining CdTe with GT. The combination ratio between GT and CdTe QDs is 0.35 to 1.0 according to HPLC. GT as an enhancement has first been applied to the determination of the bovine serum albumin (BSA) labeled with CdTe QDs, and the fluorescence intensity of the labeled BSA with GT is 6 times higher than the control. The proposed method might offer an attractive potential for use in future, because it is sensitive and rapid.