Injectable PolyHIPE Scaffolds for Bone Grafts
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Solution Overview
Problem
Current materials for three-dimensional scaffolds are not injectable, lack proper porosity, and have limitations in compressive strength and modulus, making them unsuitable for in vivo use in tissue engineering applications, particularly for bone grafts, as they often require toxic diluents and high cure temperatures.
Innovation Solution
Development of injectable polyHIPEs that cure at physiological temperatures, providing high porosity, sufficient compressive strength, and modulus, using biodegradable macromers like propylene fumarate dimethacrylate (PFDMA) with appropriate viscosity and hydrophobicity, and a surfactant like polyglycerol polyricinoleate (PGPR) to form stable emulsions without toxic diluents, allowing for in situ crosslinking and formation of rigid, porous scaffolds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional polymerization methods are used to create three-dimensional scaffolds, then the scaffolds can achieve structural integrity, but they require toxic diluents and high cure temperatures that make them unsuitable for in vivo use
Solution Approach 1:
The patent changes the polymerization parameters by using photoinitiated polymerization at physiological temperatures instead of conventional thermal polymerization, and by replacing toxic diluents with water as the continuous phase in the emulsion system, thereby achieving structural integrity without toxic or high-temperature harmful factors
Solution Approach 2:
The patent creates a composite emulsion system consisting of an organic phase containing polymerizable monomers and an aqueous continuous phase, stabilized by surfactants. This composite structure allows the formation of porous scaffolds with structural integrity while using non-toxic water-based components and enabling polymerization at physiological temperatures through photoinitiation
2Stability of the object's composition
If conventional scaffold materials are used, then structural stability can be achieved, but they lack proper porosity for cellular infiltration and nutrient transport
Solution Approach 1:
The patent employs a high internal phase emulsion (HIPE) where an organic phase dispersed in an aqueous continuous phase forms droplets that, upon polymerization, create a highly porous three-dimensional network structure. The porous structure achieves porosity exceeding 70% while maintaining structural stability through the crosslinked polymer network
Solution Approach 2:
The patent pre-forms the emulsion structure with the desired porosity and pore size distribution before polymerization occurs. The surfactant-stabilized emulsion droplets are arranged in a space-filling structure that templates the final porous scaffold architecture, ensuring proper porosity for cellular infiltration and nutrient transport is achieved before the material sets
3Strength
If conventional materials are used for in vivo scaffolds, then structural strength can be achieved, but they are not injectable and require additional modifications before use
Solution Approach 1:
The patent creates a dynamic system where the emulsion maintains a pumpable, injectable consistency in its pre-polymerized state, then transforms into a rigid, structurally strong scaffold upon photoinitiated polymerization in situ. This dynamic transition from fluid to solid state enables the material to be injected through syringes and then develop the mechanical strength required for load-bearing applications
Solution Approach 2:
The patent utilizes a phase transition from a liquid emulsion phase to a solid polymer network phase through photopolymerization. The emulsion remains in a liquid state during injection, then undergoes phase transition to a rigid solid structure after implantation, achieving both injectability and structural strength without requiring additional modifications
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 resulting polyHIPE scaffolds exhibit high porosity, mechanical strength, and cytocompatibility, enabling their use as injectable tissue-engineered bone grafts that can withstand physiological loads and degrade complementarily for tissue regeneration.
Implementation Method 1
The resulting biodegradable molecule may be synthesized to have an appropriate viscosity and hydrophobicity for emulsification. Synthesis includes use of a surfactant.
Implementation Method 2
The process also includes incubation of the one or more HIPEs at about 37° C., which provides, in one form a crosslinking reaction of an unsaturated double bond of certain side groups
Implementation Method 3
continuous phase polymerization for maintaining a desired emulsion geometry
Data Source
AI summary
Materials and methods for preparing three dimensional scaffolds are described. The materials, as improved high internal phase emulsions (HIPES), and the polymerization thereof may be suitable for injection prior to curing and when in an injectable form may be for site-directed in vivo use, curing after injection. In addition, said materials before curing may be engineered as a tissue substitution or enhancement and/or to include cell encapsulation. Said materials described herein form a monolith after curing and are biodegradable and porous after curing. Said materials are made from starting molecules using a process that does not rely on toxic solvents or monomers. Making of said materials to form the emulsion take advantage of one or more surfactants for HIPE stability. In addition, said materials cure at temperatures appropriate for use in an in vivo or in situ environment.