5 ml syringe

The bladder phantom was constructed by cutting down the barrel of a 5 mL syringe (Becton Dickinson Infusion Therapy AB, Helsingburg, Sweden) to 2 mL. The tube was closed by inserting rubber plungers from two 5 mL syringes on both ends, such that volume adjustment was possible by moving the rubber plungers. The catheter was introduced into the bladder phantom through one of the plungers with a needle from a Vasofix Safety IV Catheter.

The valley topological PCs is composed of a 5 mm thick glass ceiling and a 25.4 mm thick acrylic plate containing cylindrical cavities distributed in 2D honeycomb lattices. The channel height (distance h_c between the glass ceiling and the acrylic plate) can be adjusted by changing the heights of four spacers placed at the four corners of the acrylic plate for supporting the glass ceiling. The cavities are fabricated through milling and have the same diameter of 8.7 mm and the same depth of 18 mm. The cavity centers are located at the vertices of a honeycomb with the distance D = 21.1 mm. The effective depth of each cavity can be tuned by pumping water into/out of the cavity with a syringe (Becton Dickinson, 5 ml Syringe) through a port connected to the bottom of the cavity or by directly pipetting water with a high precision pipette (Fisherbrand™ Elite Pipette with an error less than 2 µL). In our proof-of-concept design, the channel height and cavity volumes are manually controlled, but automated tuning using a microcontroller is clearly possible.

Electrospinning was performed in a Nanon 101A electrospinning setup (NANON Supply, MECC, Fukuoka, Japan). A 5-mL syringe (Becton-Dickinson, Franklin Lakes, NJ, USA) and an 18-gauge blunt metallic needle (NANON Supply, MECC, Fukuoka, Japan) were connected to approximately 10 cm of Teflon tube (Cole-Parmer Instrument Company, Vernon Hills, IL, USA) to deliver the solution with a feed rate of 0.3 mL/h. Then, 18 kV of voltage over 150 mm of distance was applied to stretch the solution, and the produced fibers were collected on flat aluminum sheet. The collected samples were kept for two days at room temperature for natural drying before performing any characterization test.

Polyvinylpyrrolidone (PVP K-90, Mw 360,000, Sigma-Aldrich, St. Louis, MO, USA) solutions were prepared in Milli-Q water with stirring overnight at room temperature. VLP (5 mg) which had been dialyzed against PBS was added to a 30% w/v PVP solution at a 1:1 ratio and mixed by magnet stirring for 20 min. The solution was drawn into a 5-mL syringe (Becton Dickinson, Franklin, NJ, USA) with blunted needle (18 G) and attached to an infusion pump (Fusion Touch 100, Chemyx Inc., Stafford, TX, USA) to deliver the solution at a constant flow rate of 0.1 mL h⁻¹. The live terminal of a high voltage power supply was attached to the needle and was set to generate an electrical potential of 24 kV. A grounded metal wheel collector was placed 15 cm from the needle tip and rotated at approximately 10 rpm. A strip of aluminum foil was placed around the circumference of the wheel, to which nanofiber was deposited. Nanofiber mats were stored at room temperature on the aluminum foil in a zip-locked bag containing silica gel. Nanofibers were stored for up to seven days prior to biological assays.

Bone marrow was harvested from the femur and tibia by isolating the leg bones, snipping the top and bottom of each bone to expose the bone marrow, and flushing the bone marrow with cRPMI using a 5 ml syringe fitted with a G18 needle. Isolated bone marrows were pelleted at 500 × g for 10 min prior to resuspension in cRPMI and filtration through a 100 um cell strainer set over a 50 ml conical. Cells that did not flow through the filter were mechanically dissociated using the flat end of the plunger from a 5 ml syringe (BD Biosciences) prior to washing with DPBS. Cells were pelleted by centrifugation at 500 × g for 5 min prior to RBC lysis with ACK Lysis Buffer (Gibco). Cells were resuspended in cRPMI prior to cell counting. All samples were processed at room temperature and stored at 4 °C unless otherwise noted.