Polyurethane composite sheet, a method of making such composite sheet, and use thereof in making a medical implant
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Solution Overview
Problem
Current synthetic heart valve prostheses face challenges in achieving biostability, biocompatibility, and hemocompatibility while maintaining high pliability, formability, toughness, strength, and fatigue resistance, limiting their clinical success and durability.
Innovation Solution
A polyurethane composite sheet reinforced with biocompatible high-strength polymer fibers, comprising a biostable polyurethane elastomer with polysiloxane segments and a woven or braided fabric, exhibiting non-linear uniaxial tensile behavior, is developed to address these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bioprosthetic valves use xenograft materials like chemically crosslinked bovine or porcine pericardium, then the valves can be made as collapsible/expandable prostheses suitable for minimally invasive techniques, but the valves experience calcification leading to thickening and stiffening, limiting lifetime to about 7-10 years
Solution Approach 1:
The patent uses a composite structure consisting of a polyurethane matrix combined with textile reinforcement (woven or non-woven fabric). This composite material provides both the flexibility needed for minimally invasive implantation and the durability to resist calcification and degradation over time, thereby extending valve lifetime while maintaining ease of deployment
2Duration of action of stationary object
If mechanical valves are made from metal-carbon combinations, then high durability is achieved, but the valves are prone to infection, inflammation and thrombosis, requiring lifelong anti-coagulation medication and open-heart surgery
Solution Approach 1:
The patent changes the material parameters by using biocompatible polyurethane elastomers with specific molecular structures (polysiloxane segments, polycarbonate segments) that inherently resist thrombosis and inflammation. The material surface properties are optimized to be blood-compatible, eliminating the need for lifelong anticoagulation while maintaining mechanical durability
Solution Approach 2:
The patent applies different material compositions to different parts of the valve structure. The polyurethane matrix provides blood-contacting surfaces with thromboresistant properties, while the textile reinforcement provides structural strength. This localized functional differentiation allows the valve to resist harmful biological reactions while maintaining durability
3Duration of action of stationary object
If synthetic materials are used to increase valve lifetime beyond 5-10 years, then durability is improved, but achieving biostability, biocompatibility, and hemocompatibility while maintaining high pliability, formability, toughness, and fatigue resistance becomes challenging
Solution Approach 1:
The patent combines polyurethane elastomer matrix with textile reinforcement to create a composite material that simultaneously achieves extended lifetime and high reliability. The polyurethane provides biocompatibility and elasticity, while the textile framework provides structural integrity and fatigue resistance, together meeting all requirements for long-lasting reliable valve function
Solution Approach 2:
The patent optimizes the molecular parameters of the polyurethane elastomer by incorporating specific segments (polysiloxane, polycarbonate) that enhance biostability and resistance to degradation. The material composition is tuned to achieve the right balance between longevity and biocompatibility, with controlled crosslinking density and molecular weight to prevent both premature failure and harmful biological reactions
Data Source
AI summary
Disclosed herein is a polyurethane composite sheet comprising o a biocompatible and biostable polyurethane elastomer comprising polysiloxane segments, the polyurethane forming a continuous matrix of the sheet; and o a woven or braided fabric having a thickness of 15-150 μm and comprising biocompatible, high-strength polymer fibers; wherein the composite sheet comprises 10-90 mass % of polyurethane, has a thickness of 25-250 μm and an areal density of 5-300 g/m2; and wherein the composite sheet has, in at least one direction, non-linear uniaxial tensile behavior characterized by a 1%-secant modulus of 20-200 MPa, a hardening transition point at 10-45%, and a tensile strength of at least 25 MPa (measured in water at 37° C.).