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. 2021 Jun 29;4:101. doi: 10.1038/s42004-021-00538-7

Fig. 2. Growth of hydrogels from enzyme particles on surfaces, at the air–water interface or in motion.

Fig. 2

a Hydrogel on ground watermelon seeds (2) in a solution of 1 = urea, 3 = ETTMP 1300 (+ acid), 4 = PEGDA 700 with the initial concentrations: [urea] = 0.075 M, [PEGDA] = 0.2 M and [ETTMP] = 0.15 M. b Hydrogel on seeds trapped at the air-water interface along with inactive husk. c Hydrogel growth on a seed sinking to the bottom of the cuvette. d Position of hydrogel and pH front in time, inset shows solution with and without pH indicator (image size = 14 × 12 mm). eg Reaction-diffusion simulations of the urea-urease reaction with particle diameter = 1 mm and with [urea] = 0.075 M, [H+] = 2 mM: e Position of pH front in time (pH > 7) and f pH profile and g ammonia, carbon dioxide, and acid profile at 500 min of reaction time.