Multifunctional Hydrogels with Reversible 3D Ordered Macroporous Structures

Three‐dimensionally ordered macroporous (3DOM) hydrogels prepared by colloidal crystals templating display highly reversible shape memory properties, as confirmed by indirect electron microscopy imaging of their inverse replicas and direct nanoscale resolution X‐ray microscopy imaging of the hydrated hydrogels. Modifications of functional groups in the 3DOM hydrogels result in various materials with programmed properties for a wide range of applications.

and CuBr (or CuCl) was added. The flask was then degassed and back filled with nitrogen thrice. The

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flask was allowed to warm up to room temperature and an initial sample (t = 0) was collected by syringe. The flask was then placed in an oil bath thermostated at the desired temperature. At timed intervals, samples of the reaction mixtures were taken for 1 H NMR and GPC measurements. The polymerization was stopped by opening the flask and exposing the catalyst complex in the solution to air. Poly(N-isopropylacrylamide) (PNIPAM) was synthesized according to a previously reported procedure. 7 Poly(lauryl methacrylate) was synthesized according to a previously reported procedure. [8][9] Figure S1. (a) SEM image and (b) the particle size histogram with a Gaussian size distribution fit (solid        S26 resulting BCA assay mixture was added to each sample in the wells. The samples were incubated at 37 °C for 30 min, and the absorption at 562 nm was measured using a TECAN infinite M1000 plate reader.
The obtained calibration curve is shown in Figure S16.  Table 1. 25 μL of every sample were transferred into a 96 flat bottom transparent polystyrol well plate. BCA protein assay kit solutions B and A were mixed in a ratio of 1/50 (v/v). 200 μL of the resulting BCA assay mixture was added to each sample in the wells. The samples were incubated at 37 °C for 30 min, and the absorption at 562 nm was measured using a TECAN infinite M1000 plate reader. The obtained calibration curve is shown in Figure S17. S28 reaction was monitored photometrically through the measurement of the extinction coefficient at 247 nm. In the following discussion, one unit is defined as the amount of enzyme releasing 1 μmol N-α-ptosyl-L-arginine per minute under the denoted conditions.
A TAME stock solution was prepared (189 mg TAME in 50 mL water). The enzyme is dissolved in HCl aqueous solution (1 mM) with an enzyme concentration of 5.5 μg/mL. For the activity measurements, a 1.5 mL quartz cuvette with 75 μL TAME stock solution, 200 μL enzyme solution (1.1 μg enzyme), and 1225 μL Tris buffer was prepared. The obtained curve was shown in Figure S18. The resulting slope of the linear regression is 0.0155 min -1 . By using equation 1, the activity of natural trypsin was calculated to be 587.1 units.
For the evaluation of the activity of the hydrogel-trypsin sample, 0.6 mg of the sample containing 6.6 μg of enzyme (data from BCA assay) was added to a mixture of 75 μl TAME stock solution, 100 μL HCl aqueous solution (1 mM), and 1325 μL Tris buffer. The extinction at 247 nm was acquired at timed intervals. Between each acquisition, the suspension was homogenized by shaking. The obtained curve is shown in Figure S19. The resulting slope of the linear regression is 0.06553 min -1 , which corresponds to 24.3 units per mg of enzyme for hydrogel-trypsin.
The enzyme activity was determined from the slope of the obtained linear curve according to eq. 1.
[ ] / 247 Enzyme activity = 1.5 0.54 0 where E 247 is the extinction at 247 nm, t is the reaction time, 0.54 is the extinction of 1 μmol N-α-ptosyl-L-arginine, W 0 is the initial weight of enzyme in mg per 0.1 mL solution, 1.5 is the total volume of sample in mL.  The catalysis activity of the Au NPs loaded 3DOM hydrogels was measured by using a model reaction of the catalytic reduction of 4-nitrophenol into 4-aminophenol with NaBH 4 . The UV-vis spectroscopy was used to monitor the reduction process, and the results are shown in Figure 5d. The characteristic absorption peak of 4-nitrophenol located at 400 nm decreased quickly upon the addition of the catalysts to the reaction mixture. Meanwhile, a new peak at 290 nm appeared that was attributed to the formation of 4-aminophenol. Since the concentration of NaBH 4 greatly exceeded 4-nitrophenol and the catalyst and remained essentially constant during the reduction, the kinetics of this reduction was supposed to follow pseudo-first-order to the concentration of 4-nitrophenol, and the kinetic equation can be defined by eq. 2: where t is the reaction time, A 0 is the initial absorbance at time zero, A t is the absorbance at time t, A ∞ is the absorbance when the reaction is completed, and k ap is the apparent rate constant. 13 As seen in Figure   S26, the linear-fit plot coincides with eq. 2, indicating pseudo-first-order kinetics for this reduction. The values of k ap = 6.5 10 -4 s -1 , which was comparable with, or higher than, some other types of supported metal nanocatalysts, such as dendrimer-metal nanocomposites (10 −5 ∼10 −1 s −1 ) [13][14] and SiO 2 -Pt nanohybrids (∼10 −3 s −1 ). 15 The high values determined for k ap in the successive cycles of catalytic reduction demonstrated the high catalytic activity of Au NPs loaded 3DOM hydrogels.