Modified Electrospinning and Cross-linking of Recombinant Spider Silk Proteins

One of the most innovative techniques for creating robust fibers is that of electrospinning. Using this technique our dope (solubilized spider silk proteins) is placed into a syringe and a positive electrode is attached to it while the target (rotating spindle/funnel or stationary target) has the negative electrode attached. With the electrodes in place an electric field is created. This then forces the dope droplet at the end of the syringe to be ejected at an incredibly quick rate. The quick ejection rate creates an elongation factor that induces nanofiber formation generating mats comprised of thousands of nanofibers. Traditionally electrospinning produces a mat that must then be processed into yarns/fibers. Our group has modified our electrospinner to be able to produce a continuous multi-fiber yarn comprised of several hundred nanofibers (approximately 150-300 nanofibers). This continuous yarn is then reeled outside of the electrospinner and collected onto a spindle for further processing. To further enhance the spider silk fibers (and other spider silk materials) our group is employing a technique traditionally used to analyze protein-protein interactions. The method is known as photo-induced cross-linking of unmodified proteins (PICUP). PICUP creates cross-links between two amino acids within the proteins present creating bridges. This amino acids cross-link is how our spider silk proteins will be reinforced internally. By incorporating two additives to our dopes then irradiating them with a high power light source, two amino acids are covalently cross-linked enhancing their mechanical properties. To increase the efficiency of this reaction our lab created the C.L.I.P. (Cross-Link Initiating Photodiode), a 200w LED light source designed to stay at low temperatures regardless of the run time. Using the C.L.I.P. some of our materials have already seen a seven to ten fold increase in mechanical properties, as well as being able to tailor the properties to fibers by either decreasing their strain or increasing their stress