Enzyme-responsive shape memory polymers
Inventors
Henderson, James • Mather, Patrick T. • Buffington, Shelby
Assignees
Publication Number
US-11512417-B2
Publication Date
2022-11-29
Expiration Date
2039-03-28
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Abstract
An enzyme responsive shape memory polymer formed from a glassy, cross-linked shape memory polymer that incorporates ester bonds that are responsive to the present of an enzyme. PCL-based polyurethanes (featuring simple alternation of PCL diol and lysine-based diisocyanate) are degradable by Amano lipase PS. A non-degradable thermoplastic elastomer may be dual electrospun with a polycaprolactone based TPU with the fixing phase compressed so that the composite is ready for enzymatically triggered contraction. Alternatively, the elastomer may be a PCL copolymer-based polyurethane amorphous elastomer that is both degradable and elastomeric and put into compression so that upon enzymatic degradation of the elastomeric phase the scaffold expands.
Core Innovation
The invention describes an enzyme-responsive shape memory polymer system that integrates biological stimuli with synthetic materials to create hybrid feedback systems. Specifically, it provides shape memory polymer composites that undergo programmed shape change or mechanical force application in direct response to enzymatic activity under isothermal and cytocompatible conditions. The core material innovation uses glassy, cross-linked shape memory polymers containing ester bonds, such as poly(ε-caprolactone) (PCL)-based polyurethanes, which are degradable by certain enzymes, including Amano lipase PS.
The problem addressed is the absence of enzyme-responsive shape memory polymers that can react to biological stimuli under cell culture or physiological conditions. Previous stimuli-responsive materials could only be triggered by non-biological cues like temperature or light, limiting their integration into synthetic/living feedback systems. There was a need for shape memory polymers that respond to enzymatic stimuli, enabling materials that can undergo controlled, cell- or tissue-driven shape changes while remaining cytocompatible.
The system typically consists of a composite fiber mat formed by dual electrospinning two polymers: a degradable polymer (such as PCL, acting as a shape fixer) and a non-degradable elastomer (such as an aromatic polyether-based thermoplastic polyurethane like PELLETHANE®, acting as the memory component). Once programmed into a temporary shape through heating, stretching, and cooling, the composite maintains the temporary form until exposed to the enzyme, which selectively degrades the fixing phase. This degradation releases the elastomeric phase to recover the original shape, enabling enzyme-triggered contraction or expansion, depending on the specific material arrangement and composition.
Claims Coverage
The independent claims cover two main inventive features: a composition of an enzyme-responsive shape memory polymer system and a method for producing such a system.
Composite fiber mat with enzyme-degradable and non-degradable polymers enabling enzyme-triggered shape memory effect
A composite fiber mat consists of at least two sets of intermingled fibers: the first set made from a polymer with a transition temperature that allows the mat to be fixed into a temporary shape, and the second set made from a different polymer that applies a biasing force when the mat is in the temporary shape. The key inventive feature is that the first polymer is degradable by an enzyme, while the second is resistant to degradation by that enzyme. This configuration allows the temporary shape to be retained until enzymatic degradation of the fixing polymer triggers recovery to the original shape.
Method for forming dual-fiber enzyme-responsive shape memory polymer mats via dual electrospinning and programming
A method involves providing a first polymer that is degradable by an enzyme and a second polymer that is not degradable by the enzyme. Dual electrospinning of solutions containing each polymer forms a composite fiber mat with intermingled fibers of both polymers. The method includes heating the mat above the transition temperature of the first polymer, fixing the mat into a temporary shape while the second set of fibers provide a biasing force, and, optionally, exposing it to the enzyme to degrade the first set of fibers and cause shape recovery.
The claims broadly cover both the material composition and the manufacturing method of enzyme-responsive, dual-fiber shape memory polymer systems, establishing enablement for enzyme-triggered shape memory and recovery through selective degradation.
Stated Advantages
The invention enables shape memory polymers to respond directly to enzymatic activity, facilitating material actuation under cytocompatible and isothermal conditions suitable for biological integration.
The system allows for controlled, programmable shape change or mechanical force application triggered by biological stimuli rather than external physical triggers.
The materials and processes demonstrated are cytocompatible, supporting cell viability both during and after shape recovery triggered by enzymatic activity.
The technology advances understanding of structure-property relationships at interfaces between synthetic materials and living systems, enabling exploration of new material phenomena.
Documented Applications
Drug delivery vehicles that affect target cells or organs through controlled release modulated by the physiological status of the cells or organs.
Scaffolds that guide tissue regeneration by altering material and mechanical properties in response to properties and behavior of regenerating tissue.
Platforms for stem cell culture that maintain stem cell phenotype or promote differentiation in response to the phenotypic state of the cells.
Decision-making biosensors ('sense and treat') that use feedback systems to control patient treatment.
Synthetic/living feedback systems where both material and cellular behavior can mutually influence each other in fundamental biomaterials research.
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