Team:UCLA/Notebook/Materials/29 May 2015

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• Silk fibers from yesterday were soaked overnight in their respective coagulation baths (isopropanol and ethanol)
• Today, we placed the fibers in ddH2O to rinse them
• Took some samples onto microscope slides in order to image
• Left the rest of the fibers on weigh boats to dry off
• The silk is incredibly difficult to handle. We absolutely need a mechanical draw in order to handle the fibers better in the future!
• Fibers were extremely brittle.

• Overview of these fibers
  • 15% w/v silk dope
  • Spun into 70% v/v ethanol or isopropanol
  • Used a 1 mL syringe attached to 0.0005 inch inner diameter PEEK tubing
  • extruded at a nominal rate of 6 uL/min on the syringe pump
  • After spinning, left in coagulation bath overnight
  • Then bathed in water
  • Then taken out and left to dry

• Overall, it seems so far that ethanol is better than isopropanol as a coagulation bath. However, until we incorporate a mechanical post-spin draw, we can't say for sure.

Images of Silk spun into isopropanol

• 4x magnification

• 10x magnification

• 20x magnification

• 40x magnification
  • Those appear to be cracks

• 20x magnification
• Notice the split: we were probably imaging multiple fibers, instead of one. This shows how difficult it is to handle individual fibers while they're still wet!

• 40x magnification
• This is the edge of the fiber where we broke it.

Images of silk spun into ethanol

• 2x magnification

• 10x magnification

• 40x magnification
  • Notice how compared to the isopropanol spun fiber, the morphology is much more smooth and uniform for the ethanol fiber. I wonder how these would look under electron microscopy?

Meeting with Julian regarding hydrogels

• making hybrid hydrogels with native bombyx mori silk + Tamura, ABD, etc.
• yields of the recombinant protein
  • a few mg yield
  • in a buffer
  • fairly low concentration

• we'll likely vortex the solution to gelate

• Next week, we'll likely be making negative controls
  • have just a silk hydrogel
  • measure to see if any protein leaches out from the gel on its own
    • we would need to account for this
  • make silk + albumin hydrogel
    • measure how much albumin leaches out
  • make silk hydrogel, put albumin solution on top
    • measure how much albumin goes in/ leaches out without the albumin binding domain

• Experimental gels
  • make a hydrogel with albumin-binding-domain-silk in it
  • pipette a solution of albumin over the top, let it soak for a while into hydrogel. give it time to bind
  • remove albumin solution
  • pipette some saltwater/buffer solution on top
  • at various time points, take aliquots and assay to see how much protein leached out