Ammonium persulfate

Acrylamide solution (30% in water), N-N´-methylenebisAcrylamide solution (2% in water), ammonium persulfate (1% in water), and N,N,N´,N´-tetramethylethylenediamine (≥98%, p.a.) were purchased from Carl Roth GmbH (Karlsruhe, Germany). All other chemicals were purchased from Sigma-Aldrich (Steinheim, Germany). Iron(II) chloride tetrahydrate and carboxymethyl dextran sodium salt were used as received without further purification. To prepare a 5% hydrogen peroxide solution (5 wt% in H₂O₂), hydrogen peroxide solution (30 wt% in H₂O₂) was diluted with five parts of deionized water. Deionized water was generally produced using a Mill-Q A10 system (Millipore, Billerica, MA, USA) and used for both synthesis and for preparation of solutions and dispersions.

Phosphate buffered saline (PBS) pH 7.4 consisted of sodium chloride, potassium chloride, disodium hydrogen phosphate, and potassium dihydrogen phosphate (all AppliChem, Darmstadt, Germany). For the preparation of the 2% PAA gel, the individual components were added one after the other volumetrically to a glass beaker and mixed with a glass rod, and gel formation took place within 30 min. Reduction of ammonium persulfate (Carl Roth GmbH, Karlsruhe, Germany) by adding TEMED (Carl Roth GmbH, Karlsruhe, Germany) results in radical formation and polymerization of the acrylamide monomers. The bisacrylamide (Rotiphorese^®, Carl Roth GmbH, Karlsruhe Germany) provides crosslinking of the otherwise linear framework, resulting in a gel structure. To prepare the 0.15% HA gel, hyaluronic acid (MW 350 kDa) and agar (both Caesar & Loretz GmbH, Hilden, Germany) were each suspended separately in PBS 7.4 and boiled until a clear solution was obtained. Subsequently, both solutions were mixed and cold-stirred to room temperature. The composition of the individual hydrogels is listed in Table 1. Compared to the original HA gel, the concentration of the gel-forming components was reduced by 25% each to adjust the viscosity.

N,Nʼ-methylenebis(acrylamide) (MBAA, 99%; Sigma-Aldrich), poly(ethyleneglycol)diacrylate (PEGDA, Mn = 250, 575, 700; Sigma-Aldrich); ethyleneglycoldimethacrylate (≥97%; TCI), N,N,Nʼ,Nʼ-tetramethylethylendiamine (TMEDA, ≥99.5%; Sigma-Aldrich), ammoniumpersulfate (APS, 98%; Roth), 3-sulfopropylmethacrylate potassium (98%; Sigma-Aldrich), 3-sulfopropylacrylate potassium (Sigma-Aldrich), 2-acrylamido-2-methyl-1-propanesulfonicacid (99%; Sigma-Aldrich), (vinylbenzyl)trimethylammonium chloride (99%; ACROS Organics), [2-(acryloyloxy)ethyl]trimethylammonium chloride (80 wt.% in H₂O; Aldrich), [2-(methacryloyloxy)ethyl]trimethylammonium chloride (75 wt.% in H₂O; Aldrich), 2-hydroxyethylmethacrylate (97%; Alfa Aesar), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammoniumhydroxide (95%; Sigma-Aldrich), 2-methacryloyloxyethylphosphorylcholine (97%; Sigma-Aldrich), 1-vinylimidazole (≥99%; Alfa Aesar), bromoethane(≥99%; Sigma-Aldrich), amino-2-propanol(93%; TCI), methacrylicanhydride (94%; Alfa Aesar) were all used as received without further treatment. 1-Vinyl-3-ethyl-imidazoliumbromide (VEtImBr) and 2-Hydroxypropyl methacrylamide (HPMAA) were prepared according to published procedures.[21 (link),22 (link)]