Synthesis of CdSe quantum dots using selenium dioxide as selenium source and its interaction with pepsin

Area of Science:

• Materials Science
• Biochemistry
• Nanotechnology

Background:

• Quantum dots (QDs) offer unique optical properties for biological sensing.
• Cadmium Selenide (CdSe) QDs are widely studied for their photoluminescence.
• Understanding QD-protein interactions is crucial for bio-imaging and drug delivery applications.

Purpose of the Study:

• To develop a novel aqueous synthesis method for thioglycolic acid (TGA)-capped CdSe QDs.
• To investigate the interaction between synthesized CdSe QDs and the enzyme pepsin using fluorescence spectroscopy.
• To analyze the conformational changes in pepsin induced by CdSe QDs.

Main Methods:

• Aqueous synthesis of TGA-capped CdSe QDs using selenium dioxide and sodium borohydride.
• Fluorescence spectroscopy to study the quenching mechanism of pepsin by CdSe QDs.
• Calculation of Stern-Volmer quenching constant (Ksv), binding constant (KA), and binding sites (n).
• Application of Foster's non-radiative energy transfer theory to determine binding distance (r).
• Synchronous fluorescence spectra analysis to assess changes in pepsin's secondary structure.

Main Results:

• Successful synthesis of TGA-capped CdSe QDs in an aqueous medium.
• Evidence of CdSe QDs causing fluorescence quenching in pepsin, primarily due to CdSe-pepsin complex formation.
• Quantification of binding parameters (Ksv, KA, n) and binding distance (r) between CdSe QDs and pepsin.
• Demonstration that CdSe QDs induce alterations in the secondary structure of pepsin.

Conclusions:

• The developed aqueous synthesis method provides stable CdSe QDs for biological applications.
• CdSe QDs interact with pepsin, leading to fluorescence quenching and conformational changes.
• The study provides insights into QD-protein interactions, relevant for biosensing and nanomedicine development.