Biodegradable Hydrogel with Cyclic Benzylidene Acetal for pH-Controlled Degradation
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Solution Overview
Problem
Current biodegradable hydrogels struggle to accurately control degradation rates under different pH environments in the body, which is crucial for applications like surgical sealants and drug delivery, due to limitations in adjusting hydrolysis rates of acetal bonds and the presence of functional groups that affect crosslinking structures.
Innovation Solution
A biodegradable hydrogel with a cyclic benzylidene acetal structure is developed by crosslinking a polyalkylene glycol derivative with a crosslinking agent, allowing for precise control of hydrolysis rates through careful selection of substituents on the benzene ring and using monodispersed crosslinking agents to ensure high structural uniformity and controlled degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydrolyzable ester bond is introduced into polyethylene glycol to create a biodegradable hydrogel, then the hydrogel can decompose in the body and be discharged, but the degradation rate cannot be accurately controlled under different pH environments
Solution Approach 1:
The patent introduces a hydrolyzable acetal bond instead of an ester bond, changing the chemical parameter of the hydrolyzable group. The acetal bond's hydrolysis rate is highly sensitive to pH changes, allowing precise control of degradation rate by adjusting the acetal bond's molecular structure (e.g., substituent groups on the benzene ring) to match different pH environments in the body.
Solution Approach 2:
The patent creates a composite structure by combining polyethylene glycol with a hydrolyzable acetal bond-containing crosslinking agent. This composite material integrates the biocompatibility of polyethylene glycol with the pH-sensitive hydrolysis properties of the acetal bond, achieving both biodegradability and controlled degradation rate.
2Manufacturing precision
If the crosslink density is changed to adjust the hydrolysis rate, then the degradation rate can be modified, but the mechanical strength and network structure of the hydrogel are impaired
Solution Approach 1:
The patent extracts the function of rate control from the crosslink density parameter and assigns it to the chemical structure of the hydrolyzable bond. By using an acetal bond with tunable hydrolysis sensitivity to pH, the degradation rate can be controlled independently of the crosslink density, allowing mechanical strength to be optimized separately without compromising degradation control.
3Reliability
If a hydrogel is used as a drug delivery carrier, then the drug can be delivered to specific sites, but the drug release rate cannot be precisely controlled in different pH environments
Solution Approach 1:
The patent changes the pH-sensitive parameter from generic hydrolysis to acetal bond hydrolysis, which exhibits pronounced pH-dependent kinetics. By selecting acetal bonds with different molecular structures (e.g., varying substituents on the benzene ring), the hydrolysis rate can be precisely tuned to match the pH conditions at different drug delivery sites, enabling controlled drug release.
4Manufacturing precision
If functional groups are introduced to adjust hydrolysis rate, then degradation control is improved, but the crosslinking structure and uniformity are affected
Solution Approach 1:
The patent applies local quality by introducing functional groups (substituents) specifically on the benzene ring of the acetal bond structure. These localized substituent groups (e.g., electron-withdrawing or electron-donating groups at specific positions) precisely modulate the electron density and steric hindrance around the acetal bond, controlling its hydrolysis rate without disrupting the overall crosslinking network uniformity.
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
This approach enables accurate control of degradation rates under various pH conditions, ensuring the hydrogel maintains functionality until needed and degrades rapidly when no longer required, enhancing medical efficiency and reducing side effects in applications such as surgical sealants and drug delivery.
Implementation Method 1
a biodegradable hydrogel in which a hydrolyzable ester bond is introduced into polyethylene glycol has been developed
Data Source
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AI summary
To provide a biodegradable hydrogel having an acetal structure whose hydrolysis rate under different pH environments in the living body can be accurately controlled. A hydrogel obtained by crosslinking a polyalkylene glycol derivative having a cyclic benzylidene acetal structure represented by formula (1) shown below with a crosslinking agent. In formula (1), R1 and R6 are each independently a hydrogen atom or a hydrocarbon group; R2, R3, R4 and R5 are each independently an electron-withdrawing or electron-donating substituent or a hydrogen atom; s is 1 or 2, t is 0 or 1, and s + t is 1 or 2; P1 is a polyalkylene glycol having the number of terminals from 2 to 8; Z1 and Z2 are each independently a selected divalent spacer; W1 is an integer of 2 to 8 and is equal to the number of terminals of the polyalkylene glycol; and X1 is a chemically reactive functional group.