Polyacrylamide Microgel Hydrogel Synthesis

Polyacrylamide
hydrogels were prepared using two different compositions: (1) 3 wt
% acrylamide, 0.12 wt % N,N′-methylene
bis(acrylamide) (MBAm), 0.15 wt % tetramethylethylenediamine (TEMED),
and 0.15 wt % ammonium persulfate (APS) in ultrapure water (18.2 MΩ
resistivity); and (2) 5 wt % acrylamide, 0.2 wt % N,N′-methylenebis(acrylamide) (MBAm), 0.15
wt % tetramethylethylenediamine (TEMED), and 0.15 wt % ammonium persulfate
(APS) in ultrapure water (18.2 MΩ resistivity). Bulk hydrogels
polymerized in two 50 mL polystyrene conical vials (100 mL total)
and equilibrated in ultrapure water for at least 24 h before they
were mechanically fragmented into 110 μm diameter microgel particles
(Figure S1) following previous methods.^{25 (link),32 (link)} Our methods are also similar to previously established extrusion
fragmentation protocols.^{25 (link),32 (link)−36 (link)} Microgel particles were classified by size using Stokes’
sedimentation and quantified with microscopy (Figure S2). Solutions of about 50 vol % microgel particles
were equilibrated in cell culture media for at least 24 h prior to
testing.