Spider Dragline Silk Inspired Man-Made Fibers with Unique Property

From artificial tissue scaffold and bones to the crafts in aviation and automotive, spider dragline silks are capable to spin their way in. Man-made fibers that resemble the structure and function of spider dragline silk and consistently produced in large quantities are demanding and will bring excitements in medical and engineering applications. We constructed the building blocks of native dragline silk (Spidroin 1, Spidroin 2) from Nephila clavipes and inserted into expression plasmids (pKM12 and pKLP36) and transfected tobacco Nicotiana tabacum. The plant derived mini-spidroins resembles native N-terminus and C-terminus and 8, 16, or 32 copies of consensus repeat domain of Spidroin1(Sp1) and Spidroin2(Sp2). We confirmed gene insertion and RNA transcription by PCR and reverse-transcriptase PCR, respectively. Mini-sdpridroins are purified through chitin binding domain, an affinity tag that binds onto chitin resin and self-cleavable after chemical activation.  

Freeze-dried mini-spidroins formed viscous gelatin-like fluids which exhibited extending continuum property. Immuno-detection of this fluid showed various degree of polymerization of mini-spidroin monomers. When treated with acid, cross-linked by glutaraldehyde and diluted in phosphate buffer (pH 7), the condensed mini-spidroin polyelectrolytes caused negatively charged counterion (gellan gum 0.5%) condensation, forming a thin proteinaceous film at the interface. The film can be pulled into fibers that resistant to water, methanol or ethanol. Single or a combination of various mini-spidroins resulted in various types of fibers. When observed under the microscope, the fibers are auto-florescent and “twisty” with micro-fibril ridges along the fiber axis. Tensile strength testing showed unique physical properties of these fibers.