Bioresorbable Bone Implants Using Nanoscale Hydroxyapatite and Polylactide
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Solution Overview
Problem
Current composite bone implants made from synthetic hydroxyapatite and polymers like polylactide lack adequate biomechanical strength and are not fully biodegradable, making them unsuitable for effective bone regeneration and implantation.
Innovation Solution
A method involving the preparation of a mixture of synthetic hydroxyapatite with a particle size not exceeding 50 nm and granulated polylactide, followed by cryogenic milling and hydrostatic pressing to create implants with a microstructure that mimics natural bone, achieving mechanical properties similar to natural bone tissue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synthetic hydroxyapatite is used to make bone implants, then biocompatibility and bioactivity are improved, but impact strength decreases and Young's modulus becomes too high
Solution Approach 1:
The patent applies composite materials by combining hydroxyapatite particles with a polymer matrix (such as polylactide or polyepsilon-caprolactone) to create a composite implant material. This composite structure allows the implant to benefit from the high biocompatibility and osteoconductivity of hydroxyapatite while the polymer matrix provides flexibility and improved impact strength, thereby resolving the contradiction between biocompatibility and mechanical strength.
Solution Approach 2:
The patent employs parameter changes by controlling the particle size of hydroxyapatite (using nanoscale particles with diameter of 1-100 nm) and adjusting the composition ratio between hydroxyapatite and polymer components. By changing these parameters, the patent optimizes both the biological performance (enhanced osteoconductivity with nanoscale particles) and mechanical properties (improved toughness through polymer matrix), thus resolving the contradiction between biocompatibility and strength.
2Strength
If ceramic particles are added to polymer composite, then compressive strength and Young's modulus increase, but brittleness increases
Solution Approach 1:
The patent applies parameter changes by using nanoscale hydroxyapatite particles (1-100 nm diameter) instead of conventional larger particles, and by optimizing the polymer-to-ceramic ratio. The nanoscale dimension of particles enhances stress distribution and reduces stress concentration points, thereby increasing compressive strength while maintaining toughness and reducing brittleness compared to conventional composite materials.
Solution Approach 2:
The patent applies local quality by ensuring uniform distribution of nanoscale hydroxyapatite particles throughout the polymer matrix through controlled mixing processes. This uniform local distribution prevents particle agglomeration and stress concentration, allowing the composite to achieve high compressive strength while maintaining ductility and resistance to brittle failure.
3Reliability
If hydroxyapatite particle size is reduced to nanoscale, then osteoconductive properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies the intermediary principle by using surfactants or coupling agents during the mixing process to facilitate uniform dispersion of nanoscale hydroxyapatite particles in the polymer matrix. These intermediary substances prevent particle agglomeration and simplify the manufacturing process, making it feasible to work with nanoscale particles without excessive complexity in mixing and processing.
Solution Approach 2:
The patent applies parameter changes by optimizing the nanoparticle size range (1-100 nm) and controlling the surface characteristics of hydroxyapatite particles. By standardizing these parameters and establishing controlled atmosphere processing conditions, the patent reduces manufacturing variability and complexity while maintaining the enhanced osteoconductive properties provided by nanoscale particles.
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 method results in bioresorbable implants with enhanced mechanical properties and osteoconductive capabilities, facilitating bone regeneration and allowing for the production of complex shapes like bone screws, with improved biocompatibility and biodegradability.
Implementation Method 1
the obtained mixture is milled cryogenically at a temperature no higher than -150°C
Implementation Method 2
the dried granulate is placed in sealed elastic mould and compacted under pressure not less than 25 MPa and not more than 200 Mpa
Data Source
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AI summary
The method of producing implants comprising a step of mixing hydroxyapatite with polylactide and a step of forming the implant from the mixture obtained. In the mixture preparation step, the dried synthetic hydroxypatite with a particle size not exceeding 50 nm is mixed with a granulated polylactide having a particle size not exceeding 0.5 mm. The proportion of hydroxyapatite in the mixture is from 60% to 90% by weight. The obtained mixture is grinded cryogenically at a temperature no higher than -150°C and the obtained granulate is dried at a temperature no higher than 100°C. In the step of implant forming, the dried granulate is placed in sealed elastic moulds and pressed under pressure not less than 25 MPa and not more than 200 MPa. The implant consists of a substantially homogeneous mixture of polylactide with hydroxyapatite and contains from 60% to 90% by weight of hydroxyapatite, the particle size of which does not exceed 50 nm, and the molar ratio of calcium to phosphorus in these particles is from 1.57 to 1.62. The porosity of the implant is uniform throughout the volume and ranges from 1 to 30%, with the pore size being in the range of 10 μm to 250 μm.