Segmented P-dioxanone Copolymers for Soft Absorbable Sutures
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Solution Overview
Problem
Current absorbable polymers for surgical sutures and medical devices face challenges in maintaining mechanical properties post-implantation, particularly in achieving soft monofilament fibers with high thermal stability and extended breaking strength retention while avoiding thermal instability and low initial strength.
Innovation Solution
Development of semi-crystalline, p-dioxanone-rich block copolymers of p-dioxanone and epsilon-caprolactone with a segmented A-B-A structure, where the middle segment is fully amorphous and composed of 60-95 mole percent epsilon-caprolactone, allowing for high thermal stability and softness, and end segments are polymerized p-dioxanone, enabling the production of monofilaments with improved handling characteristics and prolonged strength retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional absorbable polymers are used to make monofilament sutures, then the sutures can be soft and pliable, but the mechanical properties are not retained long term post-implantation
Solution Approach 1:
The copolymer is segmented into distinct blocks: soft amorphous blocks containing epsilon-caprolactone units provide pliability, while hard crystalline blocks containing p-dioxanone units provide strength retention. This segmentation allows each block to fulfill its specific function independently, resolving the contradiction between softness and long-term mechanical property retention
Solution Approach 2:
Different regions of the polymer chain have different properties: the amorphous regions provide softness and flexibility for handling, while the crystalline regions provide structural integrity and long-term strength retention in vivo. This local differentiation of material properties within the same polymer enables both soft monofilament construction and prolonged mechanical property retention
2Temperature
If high p-dioxanone content copolymers are used, then thermal stability is improved, but the material becomes too stiff for soft monofilament fabrication
Solution Approach 1:
The polymer structure incorporates localized hard crystalline p-dioxanone blocks for thermal stability and strength, interspersed with soft amorphous blocks containing epsilon-caprolactone for flexibility. This local quality differentiation allows the material to exhibit both high thermal stability and softness simultaneously, enabling soft monofilament fabrication with adequate thermal performance
Solution Approach 2:
The copolymer acts as a composite material at the molecular level, combining rigid p-dioxanone segments with flexible epsilon-caprolactone segments. This composite structure provides the thermal stability of high p-dioxanone content while the epsilon-caprolactone segments maintain softness, resolving the contradiction between thermal stability and fabricability into soft monofilaments
3Ease of operation
If epsilon-caprolactone content is increased to improve softness, then monofilament fabrication is improved, but thermal stability and mechanical property retention deteriorate
Solution Approach 1:
The copolymer is segmented into alternating hard and soft blocks, where epsilon-caprolactone-rich amorphous segments provide softness and ease of monofilament fabrication, while p-dioxanone-rich crystalline segments maintain thermal stability. This segmentation allows high epsilon-caprolactone content (60-90%) for softness without sacrificing thermal stability, as the p-dioxanone blocks remain intact to provide structural integrity
Solution Approach 2:
The invention changes the compositional parameters by incorporating 60-90% epsilon-caprolactone units in the amorphous blocks while maintaining sufficient p-dioxanone content (10-40%) in the crystalline blocks. This parameter optimization achieves the desired softness for monofilament fabrication while preserving adequate thermal stability through the crystalline p-dioxanone segments
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 novel copolymers result in monofilaments that are exceptionally soft and pliable with extended breaking strength retention, offering improved handling and thermal stability, suitable for long-term absorbable medical applications such as sutures and meshes, while maintaining mechanical properties necessary for effective medical use.
Implementation Method 1
The novel segmented, semicrystalline, synthetic, absorbable copolymers... consist of lactone monomers... wherein the p-dioxanone is a major component
Implementation Method 2
segmented A-B-A structure, where the middle segment is fully amorphous and composed of 60-95 mole percent epsilon-caprolactone... and end segments are polymerized p-dioxanone
Data Source
Figure 1
Figure 2
AI summary
Novel p-dioxanone-rich ABA triblock copolymers of p-dioxanone and epsilon-caprolactone, wherein the "B" block is a copolymer of epsilon-caprolactone and a minor amount of lactone monomer, and absorbable devices for long term medical applications are disclosed. The novel polymer compositions are useful for long term absorbable surgical sutures, and other medical devices.