pH-Responsive Self-Healing Hydrogels via Boronate-Catechol Complexation
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Solution Overview
Problem
Current stimuli-responsive hydrogels lack stability and mechanical properties, as they are either physically bonded or non-responsive under physiological conditions, necessitating a material that integrates stability with responsiveness and self-healing capabilities.
Innovation Solution
Development of pH-responsive, self-healing hydrogels formed through boronic acid-catechol complexation, using cross-linked polymers with catechol moieties and boronic acid-containing cross-linkers to create covalent boronate ester bonds, which are reversible under acidic conditions, allowing for self-healing and stability under physiological conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If physical (non-covalently bonded) hydrogels are used to achieve stimuli-responsiveness, then the hydrogels can respond to external triggers like pH and temperature, but they lack stability and have poor mechanical properties
Solution Approach 1:
The patent merges the stimuli-responsive capability of physical hydrogels with the stability of covalent cross-linking by incorporating boronic acid-catechol dynamic covalent bonds. These bonds provide reversible cross-linking that responds to pH changes while maintaining structural integrity through covalent bonding, thus combining the advantages of both physical and chemical hydrogels.
Solution Approach 2:
The patent employs dynamic covalent bonds (boronic acid-catechol complexation) that can reversibly form and break under different pH conditions. This dynamic nature allows the hydrogel to respond to stimuli while maintaining stability, as the bonds can rearrange without complete dissociation, providing both responsiveness and reliability.
2Reliability
If covalently cross-linked hydrogels are used to achieve stability, then the hydrogels have good mechanical properties, but they lack stimuli-responsiveness and self-healing capabilities
Solution Approach 1:
The patent uses dynamic covalent bonds (boronic acid-catechol complexation) instead of static covalent bonds. These bonds can reversibly form and break in response to pH changes, enabling stimuli-responsiveness while maintaining the stability and mechanical strength associated with covalent cross-linking. The dynamic nature allows self-healing through bond reformation.
Solution Approach 2:
The patent exploits pH parameter changes to control the formation and breakdown of boronic acid-catechol bonds. At physiological pH, the bonds form providing stability; at lower pH, they break enabling responsiveness and self-healing. This parameter-dependent behavior resolves the contradiction between stability and stimuli-responsiveness.
3Adaptability or versatility
If boronic acid-catechol complexation is used to form covalent bonds, then the hydrogels achieve self-healing and stimuli-responsiveness, but the complexation reaction requires pH higher than the pKa of the reagents which is not generally reported under physiological conditions
Solution Approach 1:
The patent modifies the pH parameter to optimize boronic acid-catechol complexation. By using phenyl boronic acid (pKa ~8.8) and controlling pH above this value, the patent enables efficient complexation and self-healing. The pH control strategy allows the reaction to proceed under conditions that support both physiological relevance and effective bond formation.
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 hydrogels exhibit high stability at alkaline pH and self-healing properties, with the ability to dissociate and reform under acidic conditions, making them suitable for various biomedical applications such as drug delivery and tissue engineering.
Implementation Method 1
The complexation of diols and boronic acid in aqueous solution results in reversible covalent bonding through the formation of a boronate ester linkage
Implementation Method 2
this complexation reaction occurs at solution pH which is higher than the pKa of the two reagents used
Data Source
AI summary
Biocompatible hydrogels made from cross-linked catechol-borate ester polymers are disclosed, along with methods of synthesizing and using such hydrogels. The hydrogels of the present invention are prepared by boronic acid-catechol complexation between catechol-containing macromonomers and boronic acid-containing cross-linkers. The resulting hydrogels are pH-responsive and self-healing, and can be used in a number of different biomedical applications, including in surgical implants, in surgical adhesives, and in drug delivery systems is data provides further evidence of the viability of using the disclosed hydrogels for in vivo in biomedical applications.