Acrylamide

An acrylamide stock solution was prepared by dissolving 50 mg of powdered acrylamide (Sigma Chemical Co., St. Louis, MO, USA) in deionized water using a 50 mL volumetric flask to obtain a concentration of 1 mg/mL. Two working solutions were prepared by diluting the stock solution to obtain 50 µg/mL and 100 µg/mL in 10 mL of MRS broth in the screening stage.

A polyacrylamide hydrogel consisting of 15% acrylamide (Merck, Belgium) and 0.3% agarose derived cross linker (DGT Research Ltd., UK) was used as a diffusive hydrogel in a DGT probe. The recipe for making the diffusive gel can be found elsewhere^{63 (link)}. chelex-100 was used to prepare the resin gels according to the recipe obtained from DGT research Ltd: 1.6 gram chelex-100 resin was added to 4 mL of gel solution (mixed in advance and stored in a refrigerator at 4 °C), which is a mixture of acrylamide (40%, Merck, Belgium), acrylamide cross-linker (2%, DGT Research Ltd, UK) and MilliQ water. 24 µL ammonium persulfate (1%, Merck, Belgium) and 6 µL N,N,N,N-tetraethylenediamine (TEMED, Merck, Belgium) were added to the mixture and the mixed solution was casted into a glass assembly separated with a fixed thickness of Teflon spacer (0.04 cm). The assembly was placed in an oven at 45 °C for 1 h, and then the gel was peeled from the glass plates and hydrated in MilliQ water for at least one day before use.

Acrylamide (AM, ≥99%) and potassium persulfate (KPS, ≥99.0%) was purchased from Aldrich (Moscow, Russia) and used without further purification. The stabilized acrylic acid, obtained from Sigma-Aldrich (Moscow, Russia) was purified according to standard procedures by vacuum distillation. The purity of the initial AA was monitored by liquid adsorption chromatography. The synthesis and characteristics of new bifunctional copper and zinc containing monomers based on unsaturated acids (cinnamic and acrylic, respectively) and 4-phenyl-2,2′:6′,2″-terpyridine ligand were described earlier [40 (link)]. A schematic representation of the synthesized MCMs with pendent 4-phenyl-2,2′:6′,2″-terpyridine ligand is shown in Scheme 2. Water used as a solvent in all the experiments was distilled, deionized and deaerated by bubbling argon gas through it.

The monomers used for hydrogel preparation were acrylamide and acrylic acid from Aldrich with purities of 98.5% and 99.3%, respectively. Potassium hydroxide (KOH), 99%, was also purchased from Aldrich. As a photoinitiator, a mixture of 25% bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl pentylphosphineoxide and 75% 2-hydroxy-2-methyl-1-phenyl-propane-1-one (Irgacure 1700) from Ciba Speciality Chemicals Inc. was used. Glycerol diacrylate (DAG), 97% purity, was obtained from Industria Azteca Integral.

Tetraethyl orthosilicate (TEOS, 99%), cetyltrimethylammonium bromide (CTAB, 99%), N-isopropyl acrylamide (NIPAm, 97%), acrylamide (AAm, 98%), 3-glycidoxypropyl trimethoxysilane (GPTMS, 98%) azobisisobutyronitrile (AIBN, 98%), and doxorubicin hydrochloride (Dox), tetrahydrofuron (THF, 99%), toluene (98%), hydrochloric acid (HCl, 36%), sodium hydroxide (NaOH, 98%), ammonium nitrate (NH₄NO₃, 98%) were purchased from Aldrich Chemical Co., Saint Louis, MO, USA. All the chemicals were used as received. Human breast cancer cells, MDA-MB-231 (Korea cell line bank, Seoul, Republic of Korea), were purchased and used for this study.