Tunable silk: using microfluidics to investigate sequence-structure-property relationships
Kinahan, Michelle Elizabeth
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Silk is an ancient material that is produced in nature by both silkworms and spiders and has been used in textiles for thousands o·f years. Stronger than steel and tougher than Kevlar, silk fibers possess a unique combination of strength and elasticity. Silk is also biodegradable and biocompatible, and has been the focus of research areas ranging from fiber optics to tissue regeneration. While textile applications utilize raw silkworm silk, biomedical applications rely primarily on regenerated silk, which is derived from silkworm cocoons and reprocessed into the desired material. Additionally, there has been much progress in the area of recombinant silk technology, where genetically engineered proteins are inspired by or mimic: native silk sequences. However, despite major advancements in silk engineering, native silk spinning - a remarkable process that takes place at ambient temperature and pressure- is still not completely understood. Given these gaps in knowledge, it remains a challenge in the field to fabricate a regenerated or recombinant material that can mimic the outstanding properties of native silks. We have developed a novel microfluidic silk processing technique that mimics aspects of silkworm spinning to transform aqueous silk solution into fibers in a highly controlled manner. By altering flow parameters within the device and utilizing post-spin processing, we can tune properties such as fiber diameter and Young's modulus across a broad range for tailored applications. Unlike alternative processing methods, we can fabricate a fiber from as little as 50 micro-liters of silk solution or spin continuously for up to two hours to produce a non-woven mesh from a single fiber approximately 6.5 meters long. Using this device we have fabricated regenerated silk fibers to investigate cell behavior, incorporated silk fibers into cell sheets to provide structural support, and fabricated non-woven silk meshes for use as structural support layers for multi-layer tissue constructs. We have also spun multiple variants of recombinant silk-like sequences. We have optimized this device for use as a low-volume sequence screening tool as part of a combined computational and experimental approach to further the understanding of both native and recombinant silk protein folding and hierarchical assembly.
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