Flow induced stability of pluronic hydrogels: Injectable and unencapsulated nucleus pulposus replacement

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Biomedical Engineering

Background:

• Poloxamers (pluronics) are proposed as biomimetic substitutes for physiological gels.
• Concerns about hydrogel stability under fluid flow have limited their application.
• Understanding poloxamer gel behavior in physiological environments is crucial.

Purpose of the Study:

• To investigate the stability of poloxamer hydrogels under fluid flow.
• To determine if poloxamer hydrogels can serve as effective nucleus pulposus substitutes.
• To elucidate the mechanism of hydrogel stabilization at high flow rates.

Main Methods:

• Cryo-transmission electron microscopy (cryo-TEM) for structural analysis.
• Rapid X-ray imaging to observe gel dynamics under flow.
• Energy balance calculations to model micelle behavior.
• In vivo implantation in canine models following discectomy.

Main Results:

• Rapid flow rates stabilized poloxamer hydrogels against dissolution.
• Hydrogel response at high flow rates mimicked a solid, dissipating hydrodynamic forces.
• In vivo, the hydrogel remained intact for 3 months post-implantation in dogs.
• Radiographs confirmed prevention of disc space compression after implantation.

Conclusions:

• Poloxamer hydrogels exhibit an inverse dependence of dissociation rate on fluid velocity.
• These hydrogels act as deformable solids, resisting dissociation at high flow rates.
• Poloxamer hydrogels are a viable, stable alternative to nucleus pulposus in vivo.