3D-Printed Bone Implant Composition for Low-Temperature Strength
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Solution Overview
Problem
Existing bone cements like PMMA and calcium phosphate cements face issues such as high polymerization temperature, tissue necrosis risk, toxic monomer excretion, low injectability, low cohesion, brittleness, slow biodegradability, and low mechanical strength, limiting their effectiveness in tissue regeneration.
Innovation Solution
A polymer-phosphate-based composition comprising calcium phosphate powder, chitosan particles, and a block copolymer (PLGA-PEG-PLGA) is used for low-temperature 3D printing, with additives like plasticizers and emulsifiers to enhance viscosity and mechanical properties, and antimicrobial enzymes or growth factors for specific tissue regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PMMA acrylate cement is used for bone fixation, then mechanical strength and bonding speed are improved, but polymerization temperature increases causing tissue necrosis risk
Solution Approach 1:
The invention uses a composite material system combining calcium phosphate particles (providing mechanical strength and osteoconductivity) with a PLGA-PEG-PLGA block copolymer matrix (enabling low-temperature processing). This composite approach allows the cement to achieve adequate mechanical strength through the calcium phosphate reinforcement while the polymer matrix remains processable at low temperatures, thus resolving the contradiction between strength and temperature.
Solution Approach 2:
The invention changes the chemical composition parameters of the cement system by replacing PMMA with PLGA-PEG-PLGA block copolymer. This parameter change fundamentally alters the polymerization characteristics, enabling the cement to set at low temperatures (below 45°C) while maintaining mechanical integrity through the calcium phosphate-polymer composite structure.
2Reliability
If calcium phosphate cement is used for bone regeneration, then biocompatibility is improved, but mechanical strength and cohesion deteriorate
Solution Approach 1:
The invention creates a composite where calcium phosphate particles (providing biocompatibility and osteoconductivity) are embedded in a PLGA-PEG-PLGA polymer matrix (providing mechanical strength and cohesion). The polymer matrix acts as a binding agent that holds the calcium phosphate particles together, preventing disintegration in body fluids while maintaining biocompatibility through the use of biodegradable, biologically active components.
Solution Approach 2:
The PLGA-PEG-PLGA block copolymer acts as an intermediary material that bridges the gap between calcium phosphate particles and the surrounding biological environment. It provides mechanical support and cohesion to the calcium phosphate structure while being biocompatible and biodegradable, thus resolving the contradiction between mechanical strength and biocompatibility.
3Duration of action of stationary object
If calcium phosphate cement is used for bone filling, then biodegradability is improved, but injectability and cohesion worsen
Solution Approach 1:
The invention forms a composite system where biodegradable calcium phosphate particles are suspended in a viscoelastic PLGA-PEG-PLGA polymer matrix. The polymer matrix provides thixotropic properties that enable the cement to remain pumpable and injectable at low concentrations, while the calcium phosphate particles provide structural support. After injection, the composite sets to form a cohesive structure that maintains its integrity while gradually biodegrading.
Solution Approach 2:
The invention utilizes the dynamic thixotropic properties of the PLGA-PEG-PLGA polymer solution, which allows the cement to exhibit shear-thinning behavior during injection (becoming more fluid under shear stress) and then recover its viscosity after injection to provide cohesion and structural support. This dynamic property resolution enables both easy injectability and post-injection cohesion.
4Speed
If PMMA cement is used for implant fixation, then bonding speed is improved, but toxic monomer excretion occurs
Solution Approach 1:
The invention replaces the permanent PMMA polymer with biodegradable PLGA-PEG-PLGA block copolymer that undergoes hydrolytic degradation into non-toxic products (lactic acid, glycolic acid, and polyethylene glycol). These degradation products are naturally metabolized or excreted by the body, eliminating the long-term toxic monomer excretion problem while maintaining adequate bonding speed for clinical application.
Solution Approach 2:
The invention converts the potential harm of slow biodegradation into a benefit by using PLGA-PEG-PLGA that degrades at a controlled rate, providing temporary mechanical support during bone healing while gradually transferring load to the regenerating bone. The degradation process itself is beneficial, as it allows for natural bone regeneration and eliminates the need for second surgery to remove the implant.
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 composition allows for low-temperature 3D printing of tissue implants with improved mechanical strength, biocompatibility, and osteoconductive properties, reducing complications like necrosis and promoting bone healing.
Implementation Method 1
The polymer solution is a thixotropic, fully absorbable aqueous solution of PLGA-PEG-PLGA block copolymer
Implementation Method 2
injectable degradable calcium phosphate bone cement (CPC), which has wide clinical use as a biocompatible and osteoconductive bone cement with the ability to harden in vivo through chemical reactions under physiological conditions
Data Source
AI summary
The invention provides a composition for low-temperature 3D printing of tissue implants, which contains: - calcium phosphate powder, - chitosan particles, - aqueous solution of block copolymer (D,L-polylactide-co-polyglycolide)-b-poly(ethyleneglycol)-b-(D,L-polylactide-co-polyglycolide) (PLGA-PEG-PLGA). A kit and a method for preparing the composition are provided, as well as a method for printing tissue implants using the kit.