Mu1803

Capgel was coated with poly-L-lysine (PLL) to create a polyelectrolyte complex (PEC) “skin” on the hydrogel (Capgel-PLL). Briefly, in a biosafety cabinet, sterilized Capgel blocks were transferred onto a sterile Petri dish. A sterile scalpel was then used to dice the blocks into ~2 mm × 2 mm × 2 mm Capgel pieces. Sterile solutions of 0.05% (w/v), 30–70 kDa PLL; Sigma-Aldrich, MO, USA) were made, and filter sterilized (Nalgene, NY, USA). Once sterilized, 10 mL of PLL solution were added to a 15 mL conical tube together with diced Capgel pieces made from five (5) blocks and allowed to rotate on an orbital shaker (Orbitron Rotator II, Boekel, PA, USA), overnight, at room temperature. The Capgel pieces were then rinsed with three 30 min washes of 40 mL sterilized ddH₂O on an orbital shaker. Depending on the experiment, the pieces were submerged in saline or DMEM cell culture media (Gibco, Waltham, MA, USA) and allowed to soak at 37 °C overnight. Then, Capgel-PLL pieces were loaded into 25 G tuberculin syringes (26046, EXELint, Redondo Beach, CA, USA) and extruded onto 10 cm plastic Petri dishes for imaging using a stereo microscope with a digital camera (MU1803, AmScope, Irvine, CA, USA), or extruded into culture plates for cell studies.

Confocal fluorescence imaging was performed on the Capgel–BITES by transferring them to a glass-bottom petri dish (Fluorodish^TM- Sigma-Aldrich, St. Louis, MO, USA) with a plastic spatula. A Zeiss 710 laser scanning confocal microscope at 20× and 40× magnification was used to acquire images with the Zen 2010 software (Zeiss; Jena, Germany). The samples were excited with a 405 nm wavelength for NucBlue and 488 nm for ActinGreen 488 and z-stacks were acquired in both channels. Differential interference contrast (DIC) imaging was also performed to view cells in the context of the Capgel–BITES capillary structure. The images were overlaid, and maximum-intensity z-projections, 3D projections, and orthogonal views were processed using ImageJ. DIC movies/videos were captured using confocal microscopy and processed with the Zen 2010 software. Images of mosquito stylet mouthparts inside BITES were taken with a stereo microscope equipped with a digital camera (MU1803, AmScope, Irvine, CA, USA).

The histological analysis was performed as described previously [49 (link)]. In brief, at the end of the experiment, muscle tissues were prepared from mice, fixed in 10% neutral buffered formalin, embedded in paraffin. After serial 6 µm thick sections, tissue sections were deparaffinized using hot water and stained with hematoxylin and eosin (Vector Laboratories Inc., Newark, CA, USA). H and E-stained tissue sections were observed under a light microscope (AmScope, T690C-PL, Irvine, CA, USA), and images were taken with a microscopic digital camera (AmScope, MU-1803, Irvine, CA, USA).

We use a TIRM to measure the potential energy of a DNA-coated PS sphere near a glass surface. The microscope is designed and custom built in our lab. A detailed optical train is included in Supplementary Fig. S1. Light from a linearly polarized 632.8-nm laser (HeNe, 30 mW, Lumentum) is directed toward the glass-water interface at 70^∘ incident angle to generate an evanescent field. The laser is coupled to the measuring cell using an asymmetric dove-shaped glass prism (63^∘/70^∘, H-K9L, Tower Optical Corporation), with the 70^∘ side surface facing the incident beam and the top surface in contact with glass slide through immersion oil.
The scattered light is collected using a 50 × long working distance objective (Mitutoyo Apo Plan 50×, 0.55NA, 13 mm WD). A plate beamsplitter (50:50, Thorlabs) is put in the collection path to split the collected light into two directions, with one going into a photomultiplier tube (PMT) photon counter (Hamamatsu, H7421-40) and the other forming images on a CMOS camera (AMScope, MU1803). We use a National Instruments counter (USB-6341) to output the received photon frequencies. For frequency counting, we use the “target photon number” method in which the counter counts up to a certain number of photons to calculate a frequency. The target photon number is typically set to be 1000.