Linear Polyurethane Hydrogel for Controlled Drug Release
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Solution Overview
Problem
Existing cross-linked and high-swelling thermoplastic polyurethane hydrogel polymers for controlled drug release have limitations such as restricted molecular weight capacity, suitability only for water-soluble drugs, short release times, and inability to process into various forms due to their thermoset nature, which restricts their application and versatility.
Innovation Solution
Development of low-swelling, linear polyurethane polymers synthesized by reacting polyethylene glycol with a diol and a difunctional isocyanate, allowing for melt processing and loading of drugs with varying solubility, including hydrophobic agents, and forming films or coatings, enabling extended release profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cross-linked polyurethane polymers are used to provide reproducible swelling characteristics, then swelling percent is improved (200-300%), but molecular weight capacity of absorbed drug is limited to below 3000 g/mol
Solution Approach 1:
The patent changes the fundamental parameter of polymer architecture from cross-linked to linear thermoplastic, and adjusts the PEG block length parameter to less than 4000 g/mol. This parameter change enables the polymer to achieve both adequate swelling (50-200%) and high molecular weight capacity (above 3000 g/mol), resolving the contradiction between swelling percent and molecular weight capacity.
2Stability of the object's composition
If cross-linked polyurethane polymers are used to achieve water-insolubility and hydrogel formation, then water-insolubility is improved, but processability into solid forms (films, foams, particles) becomes impossible
Solution Approach 1:
The patent inverts the conventional approach by using linear thermoplastic polyurethanes instead of cross-linked thermoset polyurethanes. This inversion maintains water-insolubility and hydrogel formation capability while enabling full processability into various solid forms including films, foams, particles, and pellets through melting and molding operations.
3Speed
If high-swelling thermoplastic polyurethane polymers (PEG 4000+) are used to achieve short-term release (10 min to few hours), then release speed is improved, but release time duration is limited to short-term only
Solution Approach 1:
The patent changes the PEG molecular weight parameter to less than 4000 g/mol and adjusts the hydrophobic compound content to 20-80 wt%, which modifies the swelling and degradation characteristics. This parameter change extends the release time from short-term (10 min to few hours) to prolonged release (days to weeks) while maintaining controlled release speed through the balanced hydrophobic-hydrophilic structure.
4Quantity of substance
If high PEG content polymers are used to achieve high swelling (600-1700%), then swelling capacity is improved, but mechanical strength in both dry and wet states is reduced
Solution Approach 1:
The patent optimizes the PEG content parameter to less than 50 wt% and balances it with 20-80 wt% hydrophobic compound. This parameter optimization achieves moderate swelling capacity (50-200%) while maintaining adequate mechanical strength in both dry and wet states, resolving the contradiction between swelling capacity and mechanical strength.
5Stability of the object's composition
If conventional cross-linked polyurethane polymers are used to achieve water-insolubility, then water-insolubility is improved, but ability to load hydrophobic drugs is poor
Solution Approach 1:
The patent creates a composite polymer structure combining hydrophilic PEG units (less than 50 wt%) with hydrophobic compounds (20-80 wt%). This composite structure maintains water-insolubility while providing both hydrophilic and hydrophobic regions that can interact with and load both water-soluble and hydrophobic drugs, significantly improving drug loading capability and versatility.
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 polymers provide controlled release of drugs with improved molecular weight capacity, extended release times, and enhanced processability, enabling the use of various drug forms and administration methods, including films, coatings, and implants, suitable for both hydrophilic and hydrophobic agents.
Implementation Method 1
The resultant thermoplastic polyurethane polymers are water-swellable to form a hydrogel
Implementation Method 2
Pharmaceutically active agents are loaded by contacting the polymer with an aqueous solution of pharmaceutically active agent, such that the solution becomes absorbed into the polymer
Implementation Method 3
Pharmaceutically active agents can be loaded by diffusion into the polymer matrix from an aqueous solution
Data Source
Figure 1~2
AI summary
A water-swellable linear polymer is made by reacting together a polyethylene oxide of number average molecular weight less than 4000, an aliphatic diol and a difunctional isocyanate. Controlled release composition comprises the polymer together with an active agent. The polymer is able to take up pharmaceutically active agents of molecular weight 200 to 20,000.