Copolymer Quantum Dot Ligands for Water Solubility and Stability

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Solution Overview

Problem

Current ligands used for making quantum dots (QDs) water-soluble face challenges such as colloidal stability issues, especially at high dilutions, due to ligand desorption, leading to aggregation and non-specific adsorption, which hampers their effectiveness in bio-imaging applications.

Innovation Solution

A copolymer ligand with a dithiol anchoring moiety and a sulfobetaine hydrophilic moiety is developed, providing strong affinity to the QD surface, enhancing colloidal stability and resistance to desorption, even under dilute and high-salinity conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If ligand exchange is performed to make QDs water-soluble, then water solubility is improved, but colloidal stability deteriorates due to ligand desorption

Engineering Contradiction:

Improvewater solubilityVSAvoidcolloidal stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent uses a copolymer ligand comprising both hydrophilic monomers (for water solubility) and thiol-containing monomers (for strong binding to QD surface). This composite structure allows the ligand to simultaneously provide water solubility and strong anchoring to the quantum dot surface, preventing desorption and maintaining colloidal stability in aqueous environments.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The ligand structure is designed with different functional regions: the thiol-containing portions locally anchor to the QD surface with high affinity, while the hydrophilic portions extend into the aqueous medium to provide solubility. This local differentiation of functional properties within the single ligand molecule resolves the contradiction between solubility and stability.

Inventive Principle:

Principle #3Local quality

2Reliability

If ligand affinity for QD surface is increased to prevent desorption, then colloidal stability is improved, but non-specific adsorption worsens

Engineering Contradiction:

Improvecolloidal stabilityVSAvoidnon-specific adsorption

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the ligand structure by incorporating zwitterionic moieties alongside thiol groups. The zwitterionic character provides strong electrostatic interactions with the QD surface (improving stability) while also creating a highly solvated interface that reduces non-specific protein adsorption. This parameter change in ligand chemistry simultaneously addresses both concerns.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The new ligand significantly improves the colloidal stability and intracellular retention of QDs, maintaining stability over a wide pH range and high salt concentrations, thus enhancing their performance in bio-imaging applications.

Implementation Method 1

one anchoring monomer comprising a first moiety MA having affinity for the surface of a nanocrystal

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

one hydrophilic monomer comprising a second moiety MB having a high water solubility

Methodology Applied

Scientific EffectSolvation: Solvation

Data Source

PatentEP2859352B1Enhanced affinity ligands

Publication Date: 2024.05.08 NEXDOT

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AI summary

The present invention relates to ligands, nanocrystal complexed with said ligands and their use for bio-imaging.