Zwitterionic biocompatible quantum dots for wide pH stability and weak nonspecific binding to cells

Area of Science:

• Biomaterials Science
• Nanotechnology
• Life Sciences

Background:

• Water-soluble quantum dots (QDs) face limitations in life science applications due to poor colloidal stability and nonspecific biomatter interactions.
• Improving QD stability and reducing cell membrane interactions are crucial for their effective use in biological systems.

Purpose of the Study:

• To compare the colloidal stability and cell interactions of zwitterionic d-penicillamine-coated QDs (DPA-QDs) with carboxylated 11-mercaptoundecanoic acid-coated QDs (MUA-QDs).
• To evaluate the potential of DPA-QDs for enhanced applications in life sciences.

Main Methods:

• Studied colloidal stability of DPA-QDs and MUA-QDs across a physiological pH range (5-9) using single molecule fluorescence experiments.
• Investigated nonspecific interactions with living Mono Mac 6 cells by exposing cells to both types of QDs and assessing their association and removal.
• Evaluated chemical stability of DPA-QDs under oxidizing conditions.

Main Results:

• DPA-QDs demonstrated no aggregation between pH 5-9, while MUA-QDs aggregated below pH 9.
• Charge-neutral DPA-QDs exhibited weak cell membrane interactions and were easily removed by buffer flushing.
• Highly charged MUA-QDs strongly associated with cells and were difficult to remove.
• DPA-QDs showed high chemical stability, even in oxidizing conditions.

Conclusions:

• Zwitterionic DPA-QDs offer significant advantages over MUA-QDs in terms of colloidal stability and reduced nonspecific cell interactions.
• The charge-neutral surface and steric effects of DPA ligands contribute to their improved performance.
• DPA-QDs represent a promising advancement for water-soluble quantum dot applications in the life sciences.