Electrospun Polyurethane Membrane for Cell Encapsulation
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Solution Overview
Problem
Current materials fail to meet the desirable characteristics needed for the encapsulation of cellular materials within the body, such as facilitating vascularization, allowing glucose and insulin molecule flux, preventing immune cell access, and supporting cells for extended periods while allowing easy removal.
Innovation Solution
A biocompatible membrane comprising a porous, nonwoven network of thermoplastic polyurethane polymer fibers formed by electrospinning, which acts as a size-selective membrane allowing the passage of solute molecules like glucose while preventing larger particles like cells, and is used to encapsulate therapeutic agents including cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a membrane with small pore size is used to prevent immune cell access, then cell protection is improved, but nutrient and molecule flux is reduced
Solution Approach 1:
The patent employs a porous membrane with specifically controlled pore size (50-500 nm) that allows selective passage of molecules while blocking immune cells. The porous structure enables nutrient and molecule flux through the membrane while the pore size exclusion prevents larger immune cells from accessing the encapsulated therapeutic cells, thus resolving the contradiction between protection and flux.
2Quantity of substance
If a membrane with high porosity is used to allow molecule flux, then nutrient exchange is improved, but cell containment is reduced
Solution Approach 1:
The membrane utilizes a porous structure with controlled pore sizes (50-500 nm) that permits efficient molecule and nutrient flux while the interconnected porous network and fiber mat structure prevent cell escape. The porosity is optimized to allow molecular transport while the physical architecture of the porous matrix retains therapeutic cells within the encapsulation device.
3Object-affected harmful factors
If a membrane with small fiber diameter is used to create small pores, then cell protection is improved, but mechanical strength is reduced
Solution Approach 1:
The patent employs a flexible fibrous mat structure formed by electrospinning that creates a thin film-like encapsulation. The flexible nanofiber network provides adequate mechanical strength for implantation and function while maintaining small pore sizes for cell protection. The continuous fibrous structure distributes mechanical loads across the network, providing sufficient strength despite the thin and porous nature of the membrane.
Solution Approach 2:
The membrane is constructed as a composite structure combining polymer nanofibers into a mat architecture. This composite approach allows the material to simultaneously exhibit small pore sizes for cell protection and adequate mechanical strength through the interconnected fibrous network, resolving the contradiction between protection and strength.
4Object-affected harmful factors
If a dense membrane structure is used to prevent cell escape, then containment is improved, but vascularization is reduced
Solution Approach 1:
The patent utilizes a porous fibrous mat structure that balances containment and vascularization. The porous architecture with interconnected pores allows host tissue infiltration and vascularization while the overall membrane structure prevents cell escape. The porosity enables host cells and vessels to penetrate into the encapsulation device, establishing vascular supply without compromising the containment function.
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 membrane effectively shields encapsulated cells from the host's immune system, allows necessary nutrient and molecule exchange, and supports cell viability and function for extended periods, addressing the limitations of existing materials.
Implementation Method 1
a porous, nonwoven network of thermoplastic polyurethane polymer fibers formed by electrospinning
Implementation Method 2
The membrane comprises pores of a suitable size such as to allow the passage of solute molecules such as glucose, but to prevent the passage of larger particles such as cells
Implementation Method 3
the membrane can shield any encapsulated cells from the host's immune system
Data Source
AI summary
The invention relates to a therapeutic composition comprising an inner portion and a biocompatible membrane fully or partially surrounding the inner portion. The biocompatible membrane comprises at least two layers: a first layer of a porous, nonwoven network of thermoplastic polyurethane polymer fibers formed by electrospinning and having a porosity of greater than or equal to 50%; an average pore diameter of less than 5 μm; and has a thickness in the range of 10 μm to 250 μm; and a second layer of a porous, nonwoven network of thermoplastic polymer fibers formed by electrospinning. The second layer has a mean average fiber diameter of the second layer is greater than the mean average fiber diameter in the first layer, and/or wherein the average pore diameter of the second layer is greater than the average pore diameter of the first layer. The inner portion comprises a therapeutic agent. The invention also relates to uses of the membrane and therapeutic composition, for instance, to encapsulate therapeutic cells.