Diethylaminoethyl dextran

The following chemicals were purchased from Sigma-Aldrich and used as received: glucose oxidase (GOx) from Aspergillus niger, diethylaminoethyl-dextran (DEAE-dextran, M_w = 500 kDa), rhodamine isothiocyanate (RITC), fluorescein isothiocyanate (FITC), fluorescein isothiocyanate labelled diethylaminoethyl-dextran (FITC-DEAE-dextran, M_w = 70 kDa), potassium carbonate, monopotassium and dipotassium phosphate, toluene, sodium hydroxide, hydrochloric acid (37%), bovine serum albumin (BSA, heat shock fraction, >98%), α-d-glucose (96%), and poly-l-lysine hydrobromide (pLL, (C₆H₁₂N₂O)_n, 4–15 kDa, monomer M_w = 208.1 g mol⁻¹). Adenosine 5-triphosphate disodium salt hydrate (ATP, C₁₀H₁₄N₅Na₂O₁₃P₃, 551.1 g mol⁻¹) was purchased from Carbosynth Limited and 3-[methoxy(polyethyleneoxy)propyl]trimethoxysilane (90%, 6–9 PE units) was purchased from abcr GmbH, Gute Chemie.

Plaque assays were performed as described previously^{10 (link), 11 (link)}. Briefly, Madin-Darby canine kidney (MDCK) cells (Lonza, Walkersville, MD, USA) were maintained at 37 °C in a humidified 5% CO₂ chamber under stationary conditions. Each well of a 6-well plate was seeded with 1 × 10⁶ cells and cultured in α-minimum essential medium (MEM; GIBCO/Invitrogen, Carlsbad, CA, USA) containing 10% foetal bovine serum (FBS), 100 units/mL penicillin (GIBCO), and 100 μg/mL streptomycin (GIBCO). After two washes with serum-free Dulbecco’s modified Eagle’s medium (DMEM; GIBCO/Invitrogen), the cells were maintained in serum-free DMEM at 37 °C for 1 h. Then, each well was overlaid with 200 μL of diluted BAL (10⁻³, 10⁻⁴, and 10⁻⁵ dilutions) and incubated at 37 °C for 1 h. After one wash in serum-free DMEM, the cells were overlaid with serum-free DMEM containing 0.8% agarose (Becton, Dickinson and Company, Sparks, MD, USA), 0.1% diethylaminoethyl-Dextran (Sigma-Aldrich), and 7 μg/mL trypsin (Sigma-Aldrich). The cells were cultured at 37 °C for 72 h, fixed in 10% formaldehyde (Wako Pure Chemical Industries, Ltd., Osaka, Japan), and then stained with 0.037% methylene blue (Wako Pure Chemical Industries, Ltd.). Each experiment was performed in duplicate.