Labeled avidin bound to water-soluble nanocrystals by electrostatic interactions

Semiconducting nanocrystals of three different sizes capped with 3-mercaptopropionic acid were synthesized in aqueous solutions. They can efficiently bind to an avidin biomolecule by the electrostatic attraction. The conjugation of avidin leads to a red shift and a decrease in the intensity of the fluorescence emission spectra of the nanocrystals. Moreover, the red shift of the fluorescence spectra of the bioconjuates depends strongly on the pH, ionic strength, quantity of avidin, and nanocrystal size.