Vacuum oven

Fluorescent histochemical staining with confocal microscopy was used to quantify two select ROS. An Amplex Red Hydrogen Peroxide/Peroxidase Assay Kit (A22188, Molecular Probes, Eugene, OR) was used to detect hydrogen peroxide (Mohanty et al., 1997), and aminophenyl fluorescein (A36003, Molecular Probe. Inc., Eugene, OR) was used to detect hydroxyl radical (Setsukinai et al., 2003), according to the manufacturer's instructions. Briefly, the collected kernels were immersed in above‐mentioned fluorescent dyes and infiltrated in the dark using a vacuum oven (VWR Scientific, Neobits, Inc., Sunnyvale, CA) for 2 h and kept in vacuum overnight. Afterwards, the kernels were rinsed in 50 μm PBS buffer twice, and fluorescence was then detected using an Olympus BX41 spectrofluorometer (Olympus, Waltham, MA) coupled with a camera as previously described by Yang et al. (2015).

Sulfuric acid, potassium permanganate, hydrogen peroxide, and 0.5 M ethylenediaminetetraacetic acid (EDTA) solution were purchased from Fisher Scientific. Tin chloride pentahydrate (SnCl₄∙5H₂O), nickel chloride hexahydrate (NiCl₂∙6H₂O), palladium chloride (PdCl₂), and chloroplatinic acid (H₂PtCl₆) were purchased from Alfa Aesar. Graphite powders (microfyne grade) were purchased from Dixon Inc. All chemicals were used as received without further purification.
A Labconco freeze drying chamber (FreeZone 1) was used for the lyophilization of the graphene oxide hydrogels. The Labcono lyophilizer was operated at a temperature of −52 °C under a pressure of 0.02 mbar. VWR vacuum oven was used for the vacuum drying of GO powders. BRANSON digital horn sonifier was used to disperse GO in water. A Thermo Scientific tube furnace (Lindberg Blue M) was used for the hydrogen reduction of the freeze-dried graphene oxide aerogels.

Penta(ethylene glycol) (EG₅) (2.00 g, 8.39 mmol) was added to a round bottom flask (RBF) equipped with a magnetic stirrer with freshly distilled DCM. Re-crystallized p-toluenesulfonyl chloride (1.76 g, 9.23 mmol) and triethyl amine (1.74 mL, 12.6 mmol) were added to the RBF and left to stir overnight. The next day, the reaction mixture was washed three times with a saturated solution of aqueous sodium chloride. The organic layer was extracted and dried with sodium sulfate. Silica gel chromatography was used to purify the singly tosylated EG₅ (Tos₁-EG₅OH) from the doubly tosylated EG₅ and unmodified EG₅ using ethyl acetate as the eluent. The Tos₁-EG₅OH fraction was dried in vacuo (vacuum oven from VWR, Radnor, PA, USA) and its chemical composition was verified using ¹H NMR (Figure S1 in SI).

The colon was carefully dissected and the colonic tissue 1 cm distal to the cecum was fixed in pre-chilled Carnoy’s solution containing 60% ethanol, 30% acetic acid, and 10% chloroform for 2 ~ 4 h on ice. The tissue was then rinsed under running distilled water to remove excess Carnoy’s solution, placed in 70% FLEX (Richard-Allan Scientific, San Diego CA, USA) and stored at 4°C until ready to process. Before processing, the colon tissue was placed in a cassette. The cassette was then put in a beaker containing 80% FLEX and incubated at room temperature for 30–60 min. The tissue was processed in a STP 120 tissue processor (ThermoFisher Scientific, Carlsbad, CA, USA) with a program set up as follows: 80% FLEX for 30 min once, 100% FLEX for 30 min twice, clear rite for 30 min twice, and paraffin type 9 wax (Richard-Allan Scientific) for 20 min twice. Cassettes were removed from the processor and put into a beaker containing paraffin type 9 wax. Wax was degassed for 10 min in a vacuum oven (VWR Scientific Inc., Bridgeport, NJ, USA) with the vacuum pressure set at 17.5 inHg and temperature at 60°C. The degas procedure was repeated once followed by embedding using a HistoStar embedding equipment (ThermoFisher Scientific).

PDMS resin and crosslinker (Dow Sylgard 184) were mixed at a weight ratio of 10:1. PDMS was degassed under vacuum (VWR vacuum oven) at room temperature for 30 min. 25 g of the PDMS was poured into a 100 mm petri dish (VWR) and cured at 60 °C for 24 h. PDMS strips were cut to either 34.8 mm long by 6 mm wide (unbent) or 36.3 mm long by 6 mm wide (bent) to fit into a standard 6 well plate (VWR). Elastomer surface abrasion was done by wiping 50X full 360° rotations with a Kim-wipe tissue in direction parallel to the axis of bending. The patterned surface cracks were generated by ‘press embossing’ (EVG 520 semi-automated Hot Embosser) a saw-tooth topography (30 µm pitch) against newly cast PDMS. All PDMS samples were cleaned by rinsing in DI water and ethanol sequentially, 5X.