Tetrazine Ligation on Semiconductor Quantum Dots Requires Specific Surface Coating and Tagging Architectures

Area of Science:

• Nanotechnology
• Bioconjugation Chemistry
• Materials Science

Background:

• Tetrazine ligation is a click chemistry reaction suitable for nanoparticle bioconjugation.
• Optimization of nanoparticle surface chemistry and functional group tagging is crucial for successful conjugation.
• Limited knowledge exists on maximizing conjugation efficiency for quantum dots (QDs).

Purpose of the Study:

• To investigate and optimize tetrazine ligation for quantum dot bioconjugation.
• To evaluate various QD surface coatings and functionalization strategies.
• To provide recommendations for successful nanoparticle bioconjugation.

Main Methods:

• Preparation and testing of diverse QD coatings including dithiol-anchored ligands, PEG, dextran, amphiphilic polymers, and coordinating polymers.
• Functionalization of coatings with norbornene (Nb), trans-cyclooctene (TCO), or tetrazine groups.
• Assessment of ligation efficiency with small-molecule dyes and antibodies.
• Evaluation of nonspecific binding using immunofluorescent labeling on a cancer cell line.

Main Results:

• Nb-appended ligands lost reactivity upon QD binding.
• Both amphiphilic and coordinating polymer coatings showed reactivity with small-molecule dyes.
• Antibody ligation efficiency varied significantly based on dienophile (Nb/TCO), its location (QD/antibody), and polymer type (amphiphilic/coordinating).
• Coordinating polymers allowed versatile ligation but increased nonspecific binding; amphiphilic polymers avoided this issue.

Conclusions:

• Surface chemistry and functional group choice critically impact tetrazine ligation efficiency for QD bioconjugation.
• Amphiphilic polymer coatings provide a balance of versatile ligation and low nonspecific binding.
• Recommendations are provided for maximizing successful tetrazine ligation in nanoparticle bioconjugate preparation.