Hydrazine hydrate 100

Hydrogel based substrates were prepared using chemically modified polyacrylamide and soft lithography. Round glass cover slips (18 mm Diameter) were sonicated and individually placed in a 12‐well tissue culture polystyrene plate, treated with 0.5% 3‐Aminopropyl triethoxysilane (APTS) (Sigma Aldrich A3648) for 3 min then with 0.5% Glutaraldehyde (Sigma Aldrich G6257) for 30 min. The cover slips were thoroughly air dried with the treated surface up. For the polyacrylamide hydrogel coating, 40% solution of Acrylamide (Sigma Aldrich A3553) and 2% solution of Bisacrylamide (Sigma Aldrich 146072) were prepared in distilled water. Solutions pertaining to various elastic modulus were prepared as described in the table.^[72] The stiffness solution was sandwiched between a hydrophobic glass slide and the treated cover slip. 10% Ammonium Persulfate (APS) and Tetramethylethylenediamine (TEMED) (Sigma Aldrich, 1.10732) were used for polymerization in a covered, moist environment. Cover slips were carefully picked up then treated with hydrazine hydrate 100% (Acros organics 196715000) for up to 1 h to convert amide groups in polyacrylamide to reactive hydrazide groups and then 1 h incubation in a 5% solution of Glacial acetic acid is done before patterning. DI washes performed between each chemical treatment.