Engineering and Characterization of Micropatterned Hydrogel Scaffolds Using Magnetic Templating

Peripheral nerve injury affects one million people worldwide every year and leads to motor, sensor, and autonomic function loss. Damaged peripheral nerves have difficulty regenerating and reconnecting without guidance and structure when the gap is greater than three centimeters in length. A scalable, readily available scaffold is needed to guide tissue regeneration in peripheral nerve injury. Our lab aims to fabricate aligned microporous channels in hydrogels to guide cell growth in nerve regeneration. We use microfluidics to fabricate magnetic alginate microparticles (MAMs) to be used as sacrificial templates for the aligned channels in the hydrogel. The templated hydrogels are created using magnetic templating in which MAMs are first placed in a pre-hydrogel solution. The MAMs are aligned using a magnetic field before the hydrogel is crosslinked. The MAMs are then dissolved from the hydrogel leaving empty aligned channels.

Previously, our lab has studied the effect of magnetic templating on hydrogel properties and assessed templated scaffold potential in guiding cell migration in vitro. However, this has been accomplished with only one sized MAM and resulting channel diameter. Thus, the role of topographical cues, specifically channel diameter, on cell migration remains to be evaluated. In this study, we produced MAMs of varying sizes (30 – 60 µm) by altering the flow rates of the droplet and continuous solutions during microfluidic production. After templating glycidyl methacrylate hyaluronic acid/collagen-based hydrogels and clearing MAMs, we characterized the bulk mechanical properties of hydrogels as a function of MAM size. We found no significant difference in the steady state relaxation modulus of the hydrogels when the MAMs were aligned parallel to the indentation tip, and all values where comparable (~1.4 kPa) to native nerve tissue (2 kPa). We also characterized the areal density of chains in these hydrogels using confocal microscopy and fluorescent dyes to fill microporous channels. The data suggests there is a significant difference in areal density with regards to MAM size, but there is no apparent correlation. Future studies aim to analyze steady state relaxation modulus as the indentation tip is perpendicular to channels and to evaluate Schwann cell migration as a function of channel diameter.