Air Filter Devices Including Nonwoven Meshes of Electrospun Recombinant Spider Silk Proteins

The overall goal of the following experiment is to improve commercial filter materials by deposition of spider silk nonwoven meshes for filtration of small particles. First, dissolve the lyophilized recombinant spider silk proteins in HFIP to produce an appropriate spinning dope. Then electro spin the solution onto different filter materials, which are there by coated with the silk and nonwoven layer.

Next, treat the silk sub micrometer fibers with ethanol vapor in order to induce stable water and soluble structures in order to soften the nonwovens for subsequent handling. Humidified the samples with water vapor results indicate a clear dependency of spinning duration and thus layer thickness on the filter efficiency based on particle filtration measurements Compared to melt blowing of synthetic polymers. Electro spinning provides fibers that are about 10 times smaller in diameter with a smaller size distribution.

Importantly, using biocom biodegradable spiders, nano fibers lowers the putative health risk accomp with other polymer fibers. So this method can provide hypertension in the field of technical filtration. It can also be applied to medical systems such as wound coverage devices where spider silk, non-woven meshes can support wound healing.

We first had the idea for this method when we tried to produce spider silk fibers with different techniques. The low diameters obtained by electro spinning initiated the idea using them in air filtration devices To 20 milligrams of lyophilized protein at 200 microliters of HFIP and seal the vessel with perfil vortex, the spinning dope suspension for one minute shake to clear the solution and incubate at room temperature overnight. To prepare the electro spinning device, place the filter material on top of the counter electrode, preset the voltage of both the electrode and the counter electrode.

Then set the volume flow. Since toxic HFIP will be evaporated, make sure the electro spinning device is connected to a fume hood. In order to generate a well-defined tailor cone grind the sharp tip of a 20 gauge needle to a residual length of 30 millimeters.

Then connect the needle to a one milliliter syringe. Load the entire spinning dope into the syringe, then overlaid the dope with 100 microliters of air in order to allow the complete solution to be extruded during the spinning process. Next, attach the filled syringe to the syringe pump of the electro spinning device.

Carefully press the piston onto the syringe until a droplet appears at the tip of the needle. Now lock the piston. Set the distance between the tip of the needle and the counter electrode to between eight and 20 centimeters.

After connecting the high voltage source, start the syringe pump and remove the droplet from the opening of the needle. Activate all safety installations of the electro spinning device immediately and start the high voltage source. As soon as a new droplet appears.

Use a stopwatch to control spinning duration since electro spinning of recombinant spider silk proteins depends on humidity and temperature and adaptation of process parameters towards individual lab conditions might be necessary. After a defined time of electro spinning switch off the syringe pump. After 10 seconds, turn off the high voltage source to produce a nonwoven mesh.

For subsequent stability experiments. Use black paper instead of filter material. After five minutes of electro spinning, stop the process as shown earlier in a preheated 60 degree Celsius oven.

Vertically placed the filter substrates with nonwoven meshes. Allow a minimum distance of two centimeters between the samples and the walls of a lockable glass container that has two openings. For solvent introduction connect two 60 milliliter syringes, one filled with ethanol and one filled with water with silicone tubes pointing into the interior bottom of the post-treatment container.

Place the post-treatment container in the oven and add 60 milliliters of ethanol by extruding the syringe. Use a stopwatch to control treatment duration. Remove the ethanol with the syringe from the glass now at 60 milliliters of water from the second syringe over another 90 minutes.

Then remove the water and switch off the oven. In order to avoid droplets by condensation, only remove the container from the oven when it has completely cooled down. For stability tests, use silk nonwoven meshes spun on black paper or any other removable support.

Adjust double sticky adhesive tape. Then cut two frames out of cardboard. Press one frame onto the silk nonwoven mesh deposited on black paper.

Then cut off the excess nonwoven mesh and carefully remove the frame. Then attach the second frame. In the same way.

For the practical dip test, take the samples of the post pretreated and non-treated silk nonwoven mesh and dip them into deionized water. Note how the non-treated silk nonwoven mesh immediately dissolves. While the treated nonwoven mesh is stable, air dry.

The sample for SEM imaging, apply forea transform infrared spectroscopy to gain information about the structural changes of the silk proteins upon post-treatment of the non-woven meshes. Select for the transmittance mode set Scan for 800 to 4, 000 inverse centimeters. Measure 60 accumulations with average for each spectrum and one reference measure per spectrum.

For M, for quantitative analysis of the data, employ Fourier self deconvolution. Set the curves to the wave numbers between 1, 590 and 1, 705 inverse centimeters, and also include a baseline correction. Then calculate a local lease square fit as detailed by schu and colleagues in 2006.

Next, use SEM imaging to investigate fiber diameters and the morphology of silk fibers on different filter substrates and analyze the influence of the post-treatment on the fiber morphology. Use magnifications of 5, 000 to 25, 000 x in order to get sufficiently detailed images. First, place a proper fitting part of the filter material on the measuring area of the device.

Employ an acutron air permeability device according to the manufacturer’s instructions, and note the normed data. After collecting data from at least 10 different parts of the sample, calculate the arithmetic middle to determine filter efficiency. Use a proper machine with pressure control and particle counter, such as a universal particle sizer.

Handle the sample with care and do not touch the surface to prevent destruction of the non-woven mesh and avoid any pollution. Be sure to create enough samples of equal quality for performance measurements. Electro spinning of recombinant spider silk with concentrations of 10%weight per volume in HFIP on different filter materials such as polyamide, polypropylene, and polyester, resulted in smooth fibers with diameters ranging from 80 to 120 nanometers, allowing the formation of non-woven meshes on different filter materials.

Post-treatment with ethanol vapor did not lead to conspicuous morphological changes, thus establishing as a proper way of silk nonwoven post-treatment. Structural changes were detected using FTIR and subsequent FSD of Amid IB bands was performed to analyze single contribution peaks. Interestingly, post-treatment leads to an increase in beta sheet structures while the content of alpha helical and random coil structures decreases.

This result can be practically proven by dipping a post pretreated, non-woven mesh into water. As shown before, the spinning duration is the most important parameter concerning the application of silk non-woven meshes in filter materials extended spinning durations, and thus a higher number of fiber layers result in an exponential decrease of air. Likewise, the filtering efficiency of the silk containing filter materials of sub micrometer particles increases After its development.

This technique paved the way for researchers in the field of bio-inspired materials to explore their high potential in technical applications. After watching this video, you should have a good understanding of how to process recombinant spider silk proteins into sub micrometer, non-woven meshes. Useful for filtration of small particles.

Don’t Forget that working with HFIP can be extremely hazardous and precautions such as the usage of a fume should always be considered while performing the procedure.