Phase transitioning hydrogels
Inventors
Kita, Kristin B. • Smith, Nigel G. • Lowman, Anthony M. • Fussell, Garland W. • Keane, Michael F.
Assignees
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Publication Number
US-8703157-B2
Publication Date
2014-04-22
Expiration Date
Abstract
A method of forming and the resulting hydrogel composition comprising poly(vinyl alcohol) at a final concentration of about 20% (w/w) to about 65% (w/w) and polyethylene glycol at a final concentration of about 2% (w/w) to about 20% (w/w), wherein the hydrogel composition has a total polymer content, above about 30% (w/w), higher than the total polymer content of a precursor polymer solution formulated prior to the formulation of the hydrogel composition. The hydrogel composition may further comprise poly(vinyl pyrrolidone) at a final concentration of about 0.10% (w/w) to about 0.75% (w/w).
Core Innovation
A phase-transition hydrogel composition is provided that comprises polyvinyl alcohol having a molecular weight of about 145,000 Da, mixed together with water and polyethylene glycol, and separated into a solid phase and a liquid supernatant phase. The solid phase comprises a total polymer content of about 70% to about 80% by weight of the solid phase and water in an amount of about 20% to about 30% by weight of the solid phase. The liquid supernatant phase comprises a total polymer content of about 33% to about 42% by weight of the liquid supernatant phase and water in an amount of about 58% to about 67% by weight of the liquid supernatant phase.
The total polymer content in the solid phase comprises about 20% to about 65% by weight of polyvinyl alcohol and about 2% to about 20% by weight of polyethylene glycol, and the hydrogel composition has a compressive chord modulus of about 450 kPa to about 5,000 kPa. In the documented description, phase separation is induced by cooling a precursor polymer solution that is produced by mixing polyethylene glycol with a heated aqueous poly(vinyl alcohol) solution, with the resulting hydrogel achieving a higher total polymer content than the precursor polymer solution.
The hydrogel composition can optionally remove the liquid supernatant phase, and dependent embodiments describe additional components such as poly(vinyl pyrrolidone) and a radiopaque component. The disclosed formulation is reported to include phase-transition behavior with melt transitions (DSC), rheology and viscosity behavior with an increase in elasticity near a transition region, and osmotic pressure behavior relevant to implant environments.
Claims Coverage
Two independent claims are provided. Both claims focus on poly(vinyl alcohol) (about 145,000 Da) and polyethylene glycol hydrogels that phase-separate into a solid phase and a liquid supernatant with specified polymer/water partitioning, and that require a compressive chord modulus in a defined range.
Poly(vinyl alcohol)/polyethylene glycol phase-separated hydrogel with defined solid and liquid polymer partitions
A hydrogel composition comprising polyvinyl alcohol having a molecular weight of about 145,000 Da mixed together with water and polyethylene glycol, separated into a solid phase and a liquid supernatant phase, wherein the solid phase comprises a total polymer content of about 70% to about 80% by weight of the solid phase and water in an amount of about 20% to about 30% by weight of the solid phase, and wherein the liquid supernatant phase comprises a total polymer content of about 33% to about 42% by weight of the liquid supernatant phase and water in an amount of about 58% to about 67% by weight of the liquid supernatant phase.
Solid-phase polymer composition and compressive chord modulus
The hydrogel composition has a solid phase total polymer composition of about 20% to about 65% by weight of polyvinyl alcohol and about 2% to about 20% by weight of polyethylene glycol, wherein the hydrogel composition has a compressive chord modulus of about 450 kPa to about 5,000 kPa.
Precursor polymer solution heating, PEG addition, cooling, phase separation, and optional supernatant removal
A hydrogel composition formulated by first preparing and heating an aqueous solution of polyvinyl alcohol, then adding the polyethylene glycol to form a precursor polymer solution, cooling the precursor polymer solution, and allowing a phase separation to occur, thereby producing the hydrogel composition comprising a solid phase and a liquid supernatant phase, wherein the hydrogel composition optionally removes the liquid supernatant phase.
Overall claim coverage centers on creating a poly(vinyl alcohol) (about 145,000 Da)/polyethylene glycol hydrogel that phase-separates into a solid phase and a liquid supernatant with defined polymer and water fractions, and that exhibits a compressive chord modulus of about 450 kPa to about 5,000 kPa; one independent claim additionally requires a defined precursor processing sequence and allows optional removal of the liquid supernatant.
Stated Advantages
Improved compression modulus and injectability relative to PVA-only controls [as described in the provided summary].
Radiopacity for visualization [as described in the provided summary].
Swelling and dry-mass stability under osmotic conditions [as described in the provided summary].
Documented Applications
Spinal disc nucleus replacement [as described in the provided summary].
Other implant applications [as described in the provided summary].
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