Thermogelling Polymer Blends for Minimally Invasive Hydrogel Implants
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Solution Overview
Problem
Current methods for implanting hydrogels in mammals require invasive surgical procedures, lacking minimally invasive techniques for site-specific insertion.
Innovation Solution
Development of thermogelling hydrogels composed of poly(N-isopropyl acrylamide) (PNIPAAm) and a second polymer, such as polyvinyl alcohol or polyethylene glycol, which are injectable as liquids at room temperature and solidify in situ at body temperature, allowing for percutaneous or minimally invasive implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional surgical methods are used for hydrogel implantation, then reliable implant placement is achieved, but patient trauma and recovery time increase
Solution Approach 1:
The hydrogel composition's phase transition temperature is precisely controlled to be just below body temperature (37°C). At room temperature, the hydrogel remains in a liquid state for easy injection, but automatically transitions to a solid gel state upon contact with body heat, enabling minimally invasive implantation while maintaining reliable placement through thermally-induced solidification
Solution Approach 2:
The invention exploits the liquid- to solid-phase transition of the hydrogel triggered by body temperature. The hydrogel is injected as a liquid through needles or catheters, then undergoes thermal gelation in situ to form a solid implant. This phase transition enables both minimally invasive delivery and reliable structural formation without surgical trauma
2Ease of operation
If thermogelling hydrogels are injected as liquids at room temperature, then minimally invasive implantation is enabled, but the hydrogel must transition to solid state reliably at body temperature
Solution Approach 1:
The hydrogel's lower critical solution temperature (LCST) is optimized to fall within the physiological temperature range (34-38°C). This parameter control ensures the hydrogel remains liquid at room temperature for easy injection through needles or catheters, then reliably transitions to solid state upon contact with body heat, achieving both ease of delivery and reliable in situ formation
Solution Approach 2:
The hydrogel performs self-gelation upon contact with body temperature without requiring external triggers, crosslinking agents, or surgical intervention. The thermal environment of the body automatically initiates the liquid-to-solid transition, making the implantation process simple while ensuring reliable solidification at the target site
3Strength
If polymer blends are used to achieve appropriate mechanical properties, then biomimetic performance improves, but formulation complexity increases
Solution Approach 1:
The invention uses composite hydrogel formulations combining poly(N-isopropyl acrylamide) with complementary polymers (such as polyvinyl alcohol, polyethylene glycol, or polyacrylamide) to achieve desired mechanical properties. These polymer blends provide tunable rheology and elasticity while maintaining the thermogelling behavior, enabling biomimetic performance without excessive formulation complexity
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
Enables the creation of solid hydrogel implants in situ without the need for surgical invasion, providing a range of biomedical applications including disc replacement and augmentation, wound care, and drug delivery.
Implementation Method 1
solutions comprising temperature-sensitive blends or copolymers of poly(N-isopropyl acrylamide) ('PNIPAAm') and a second polymer... undergoes thermal transition just below body temperature (generally, from about 29 degrees C. to about 37 degrees C.) to form a solid hydrogel
Implementation Method 2
Hydrogels are three-dimensional, water-swollen structures composed of mainly hydrophilic homopolymers or copolymers
Data Source
AI summary
Thermogelling polymers are described containing poly (n-isopropyl acrylamide). Solutions of this polymer, copolymers or mixtures of the polymer with a second polymer such as poly(ethylene glycol), poly (vinyl pyrrolidone) or poly(vinyl alcohol) are liquids at room temperature and solids at body temperature. Thus, also provided are methods of implanting a hydrogel into a mammal by injecting the solution as a liquid at a temperature below body temperature into a selected site in the mammal at a temperature below body temperature, which then undergoes thermal phase transition to form a solid hydrogel in situ in the body as the implant warms to body temperature. Methods for using these thermal gelling materials in various applications including nucleus pulposus replacement/augmentation, wound care, disk replacement, cartilage replacement, joint replacement, surgical barriers, gastrointestinal devices, cosmetic and reconstructive surgery, and breast enlargement are also provided.