We see the potential of extracellular vesicles, but also recognize the difficulty in their isolation, especially from large sample of biofluids such as bioreactor medium. In this research we tested if we can use asymmetric field-flow field fractionation to isolate the extracellular vesicles. As of now, isolating extracellular vesicles directly from biofluids in a continuous flow for integration into bioreactors is impossible.
Instead, biofluids must be first collected and processed, adding viability and labor. Our device, designed for extracellular vesicle isolation from large-volume biofluids, enables integration with bioreactors for continuous flow and automation. We found liquid viscosity might impact extracellular vesicles isolation using asymmetric field-flow fractionation.
We're exploring if adapting biofluid and buffer flows to viscosity can enhance isolation. To begin, place an oxidized COC slide on a PDMS mold for the top channel of the device. Place the assembly into a mold-in-place jig.
Then tighten the jig with a torque wrench set to 0.3 newton meters. Connect the PTFE tube to the inlet of the mold. Fill the device with 1, 000 millibars of pressure, maintained by a piso electric pump situated in the pressure system.
Place the jig with the glass slide up into the mask aligner and expose it to 850 millijoules dosed with an ND33 filter. Now bring the structured OSTE in contact with the membrane having 11.8%poor density, ensuring that the channels are fully covered by the membrane. Place a clean glass slide on top of the membrane.
Apply a pressure of 1.6 kilopascals from the top to ensure even bonding. Then place the assembly membrane side up onto a hot plate at 60 degrees Celsius. Next, align the structure OSTE layer with the top channel assembly.
Ensure that the top and bottom layers are aligned and the OSTE bottom layer is in contact with the membrane. Use a microscope to visually evaluate the device for any defects. Once done, fill two five milliliters syringes with two milliliters of hydrogen peroxide.
Fit the syringes on a syringe pump. Next, connect 14-centimeter-long PTFE tubing to the syringes with the syringe needles. Connect the tubing to the device inlets with lure connectors.
Connect 20-centimeter-long PEEK tubing to the outlets of the device. Then connect the other end of the PEEK tubing to a waste container. On the instrument screen, press settings, then choose system set, followed by syringe.
Then click on the back button and choose parameters to input a flow speed of 500 microliters per minute. Collect the flow through in a waste container. Next, fill two new five-milliliter syringes with two milliliters of ethanol.
Replace the used syringes with the ethanol-filled syringes, then start the pump. Similarly, fill syringes with five milliliters of 20-nanometer-filtered PBS. Connect them to the pump and flush out the device with four milliliters of the PBS solution.
Unplug the tubing from the device. Enclose the inlets and outlets with lure plugs. The next day, flush the PBS filled device with four milliliters of filtered PBS.
Collect the last milliliter of the flow through from both outlets in a two-milliliter protein low-binding tube. Store at four degrees Celsius as a blank for particles introduced by the device. Replace the PBS-filled syringes with air-filled ones.
Then purge the device with four milliliters of air until all the liquid has exited the device and tubing. To test urine samples, first, collect 100 milliliters a morning urine from each donor in sterile containers. Separate each sample into two 50-milliliter tubes.
Centrifuge the tubes at 2, 000 G for 15 minutes at room temperature. Then collect the supernatant. Centrifuge the supernatant at 10, 000 G for 30 minutes at room temperature to remove any particulates.
Collect the supernatant into new tubes. Fill a 20-milliliter syringe with a prepared urine sample. Then connect it to the sample inlet of the device.
Next, fill another 20-milliliter syringe with 20 milliliters of filtered DEPC-treated PBS and connect it to the buffer inlet of the device. Transfer the flow through to 100, 000 molecular weight cutoff concentration tubes separately and centrifuge the tubes to concentrate 100 microliters each. Then transfer the concentrates to 0.5 milliliter micro centrifuge tubes.
Vortex the concentrates for 30 seconds, then spin for 10 seconds in the centrifuge. Transfer 25 microliters of each sample into new labeled tubes. Freeze them at minus 80 degrees Celsius for long-term storage.
The OSTE COC device showed better total particle recovery from biofluids relative to ultracentrifugation. The recovery using the R port of the OSTE COC device was slightly higher than size exclusion chromatography and ultracentrifugation alone. An equivalent size distribution was found between the different methodologies with the exception of ultracentrifugation, which showed a bigger particle size distribution.
The total particle recovery from both device ports exhibited superior performance.
