2 4 6 trinitrobenzene sulfonic acid tnbsa

The activating reagents for amide bond formation, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and N-hydroxysuccinimide (NHS) were supplied by Acros Organics (Geel, Belgium). N-isopropylacrylamide (NIPAM) and 2,2′-azobis(isobutyronitrile) (AIBN) obtained from Showa Chemical (Tokyo, Japan) were recrystallized from n-hexane and methanol, respectively. Hyaluronic acid (HA) (average molecular weight = 1.3 × 10⁶ Da) was purchased from Bloomage Freda Biopharm Co. (Jinan, China). Alcian blue, Safranin O, 2-morpholinoethane sulfonic acid (MES), 2-aminoethanethiol (AET), 2,4,6-trinitrobenzene sulfonic acid (TNBSA), and Dulbecco’s modified Eagle’s medium/nutrient mixture F-12 (DMEM-F12) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Fetal bovine serums (FBS) and Live/Dead cell viability/cytotoxicity kit were obtained from Thermo Fisher Scientific (Waltham, MA, USA). For methyl tetrazolium salt (MTS) assays, the CellTiter96 AQueous One Solution Cell Proliferation Assay kit was obtained from Promega (Madison, WI, USA).

Branched PEI with molecular weights of 25 and 750 kDa as well as 2,4,6-trinitrobenzenesulfonic acid (TNBSA) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Dulbecco’s modified Eagle medium (D-MEM), trypsin-EDTA, fetal bovine serum (FBS), phosphate-buffered saline (PBS) were obtained from Gibco (Carlsbad, CA, USA). Pyrrole and ammonium persulfate (APS) were purchased from Acros (Geel, Belgium) and Showa (Tokyo, Japan), respectively.

Crotonic anhydride (CA),
itaconic anhydride (IA), methacrylic anhydride (MA), type A gelatin
from porcine skin (gel strength ∼175 g Bloom), benzalkonium
chloride (BAC), deuterium oxide, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (MTT reagent), fluorescein sodium salt (NaFl), glutaraldehyde
solution (25% in H₂O, grade II), glycine, 1 M hydrochloric
acid solution, sodium bicarbonate, sodium dodecyl sulfate (SDS), 2,4,6-trinitrobenzenesulfonic
acid (TNBSA, 5% in H₂O), and trypan blue (0.4% solution)
were purchased from Sigma-Aldrich (Gillingham, U.K.). Dimethyl sulfoxide
(DMSO), Dulbecco’s modified eagle medium (DMEM), fetal bovine
serum (FBS), penicillin-streptomycin (10000 U/mL), phosphate-buffered
saline (PBS) tablets (which were used to make 100 mL of 1× PBS
solution in deionized water, pH 7.40), sodium hydroxide, and trypsin-EDTA
(0.25% solution) were purchased from Fisher Scientific (Loughborough,
U.K.). All other chemicals were of analytical grade and used without
further purification. Dialysis tubing with a molecular weight cutoff
of 12–14 kDa was purchased from Medicell Membranes Ltd. (London,
U.K.). Deionized water was used throughout the experiments involving
aqueous solutions.