Small and stable sulfobetaine zwitterionic quantum dots for functional live-cell imaging

Area of Science:

• Nanotechnology
• Biotechnology
• Materials Science

Background:

• Semiconductor quantum dots (QDs) are valuable fluorescent probes for bioimaging.
• Previous QD coatings had limitations in stability and non-specific adsorption, hindering their application.
• Polyethylene glycol (PEG) coatings are common but have drawbacks.

Purpose of the Study:

• To develop a novel surface coating for QDs to overcome limitations in bioimaging.
• To create QDs with enhanced stability, low non-specific adsorption, and preserved optical properties.
• To demonstrate the utility of these new QDs in tracking live-cell receptor dynamics.

Main Methods:

• Developed a heterobifunctional ligand: bidentate zwitterionic dihydrolipoic acid-sulfobetaine (DHLA-SB).
• Coated semiconductor quantum dots (QDs) with DHLA-SB ligands.
• Functionalized DHLA-SB QDs with streptavidin (SA) for biomolecule conjugation.
• Applied SA-functionalized QDs to track cannabinoid receptor 1 (CB1R) intracellular recycling in live cells using SA-biotin interactions.

Main Results:

• DHLA-SB coated QDs exhibited small sizes, low non-specific adsorption, and maintained optical properties.
• These QDs demonstrated excellent stability across various pH and salinity conditions.
• Streptavidin-functionalized QDs selectively targeted cell surface receptors with negligible non-specific binding.
• The internalization of CB1R into endosomes was successfully tracked, showing preserved cellular activity.

Conclusions:

• DHLA-SB ligands provide a superior surface coating for quantum dots in bioimaging.
• These novel QDs offer a robust and versatile alternative to PEG-coated nanoparticles.
• The developed QDs enable precise tracking of receptor dynamics in live cells without compromising cellular function.