Iron-Chelated Silk Microfiber/Hydrogel Composites as Injectable, Magnetically Aligned Cell Guidance Scaffolds.

Area of Science:

• Biomaterials Science
• Neuroscience
• Regenerative Medicine

Background:

• Anisotropic composites combining magnetically aligning architectures and injectable hydrogels are promising for spinal cord injury (SCI) scaffolds.
• Existing magneto-responsive scaffolds often rely on magnetic nanoparticles, posing potential challenges.
• There is a need for effective, minimally invasive delivery systems that promote neural regeneration and protection.

Purpose of the Study:

• To explore ferric iron-chelated silk fibroin microfibers (Fe³⁺-mSF) as a magnetic nanoparticle-free alternative for magneto-responsive biomaterial scaffolds.
• To evaluate the stability, mechanical properties, cytocompatibility, and neuroregenerative potential of Fe³⁺-mSF-laden hydrogels.
• To demonstrate the in situ magnetic alignment of these composites for potential SCI treatment.

Main Methods:

• Silk fibroin microfibers were functionalized via iron chelation.
• Stability was assessed at physiological pH, with iron release monitored over time.
• Injectability, gelation kinetics, swelling, and cytocompatibility (SH-SY5Y cells) of hydrogel composites were evaluated.
• Neuroregenerative biomarker expression was analyzed.
• Magnetic alignment of Fe³⁺-mSF/hydrogel composites was demonstrated using an MRI machine.

Main Results:

• Fe³⁺-mSF exhibited stability at physiological pH with minimal iron release over 7-day and 3-month periods.
• Incorporation of Fe³⁺-mSF did not compromise hydrogel injectability, gelation, or swelling.
• Fe³⁺-mSF demonstrated cytocompatibility with neuronal analog cells.
• Magnetic alignment of Fe³⁺-mSF/hydrogel composites was successfully achieved in situ.
• Minimal changes in neuroregenerative biomarker expression were observed upon Fe³⁺-mSF addition.

Conclusions:

• Ferric iron-chelated silk fibroin microfibers represent a stable, nanoparticle-free, magneto-responsive component for injectable hydrogel scaffolds.
• These Fe³⁺-mSF-laden hydrogels maintain desirable material properties and support neuronal cell viability.
• The system allows for in situ magnetic alignment, offering a promising approach for developing advanced neuroregenerative scaffolds for spinal cord injury.