Layered Polymer Coating for Stable Heparin Attachment
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Solution Overview
Problem
Current surface coatings for medical devices using anticoagulant entities like heparin face challenges with stability and biological activity, particularly due to leaching and adverse reactions, necessitating improved methods for maintaining thromboresistance without systemic heparinization.
Innovation Solution
A process involving a layered coating of cationic and anionic polymers, where the outer layer comprises an anticoagulant entity, with specific molecular weight and charge density characteristics, and application at controlled salt concentrations to enhance the covalent attachment and biological activity of heparin on medical device surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If heparin is covalently bound to the surface, then stability is improved, but biological activity may be reduced
Solution Approach 1:
The patent applies local quality by creating a layered coating structure where different regions have different properties: the cationic polymer layer provides covalent bonding sites for stable attachment, while the anionic polymer layer maintains biological activity through ionic interactions. This spatial differentiation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
The patent uses composite materials by combining cationic and anionic polymers in a layered structure. The cationic polymer (e.g., polyallylamine) provides structural stability and covalent bonding capability, while the anionic polymer (e.g., polyacrylic acid) maintains heparin's biological activity. This composite approach resolves the contradiction between stability and activity.
2Reliability
If heparin is applied to the surface, then thromboresistance is improved, but leaching occurs reducing long-term function
Solution Approach 1:
The patent applies preliminary action by pre-modifying the surface with cationic polymer layers that contain covalent bonding sites before heparin application. This preliminary preparation ensures that heparin is immediately and permanently anchored to the surface, preventing leaching from the outset and ensuring long-term thromboresistance.
Solution Approach 2:
The cationic polymer acts as an intermediary between the surface and heparin. It provides covalent bonding sites that permanently anchor heparin to the surface, preventing leaching while maintaining heparin's thromboresistant activity. The intermediary layer resolves the contradiction between immediate function and long-term stability.
3Reliability
If systemic heparin administration is used, then anticoagulant effect is achieved, but adverse reactions and monitoring requirements increase
Solution Approach 1:
The patent extracts the anticoagulant function from the systemic circulation and localizes it to the device surface through heparin coating. This extraction eliminates the need for systemic heparin administration, thereby removing adverse reactions and monitoring requirements while maintaining the anticoagulant effect at the point of contact.
Solution Approach 2:
The coated device provides its own anticoagulant function through the heparin layer, eliminating the need for external systemic administration. The device serves itself by maintaining thromboresistance locally without requiring patient intervention or monitoring, thereby eliminating adverse reactions associated with systemic therapy.
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 process results in a stable, thromboresistant surface that maintains anticoagulant activity and reduces adverse reactions, potentially eliminating the need for systemic heparin administration, while ensuring long-term bioactivity and compatibility.
Implementation Method 1
The process involves treating the surface with a cationic polymer, then treating the surface with an anionic polymer, and finally treating the outermost layer of cationic polymer with an anticoagulant entity, thereby to covalently attach the anticoagulant entity to the outermost layer of cationic polymer
Implementation Method 2
Heparin is a polysaccharide carrying negatively charged sulfate and carboxylic acid groups on the saccharide units. Ionic binding of heparin to polycationic surfaces was thus attempted
Data Source
AI summary
According to the invention there is provided inter alia a process for the manufacture of a solid object having a surface comprising a layered coating of cationic and anionic polymer wherein the outer coating layer comprises an anticoagulant entity, comprising the steps of:i) treating a surface of the solid object with a cationic polymer;ii) treating the surface with an anionic polymer;iii) optionally repeating steps i) and ii) one or more times;iv) treating the surface with a cationic polymer; andv) treating the outermost layer of cationic polymer with an anticoagulant entity, thereby to covalently attach the anticoagulant entity to the outermost layer of cationic polymer; wherein, the anionic polymer is characterized by having (a) a total molecular weight of 650 kDa-10,000 kDa; and (b) a solution charge density of >4 μeq/g; and wherein, step ii) is carried out at a salt concentration of 0.25 M-5.0 M.