We prepared the crosslinking reagents as 0.5 M MES hydrate buffer adjusted at pH 5.5 with NaOH, 5 % adipic acid dihydrazide (ADH) in MilliQ water, and 1 µg/µl N-(3-Dimethylaminopropyl)-N'ethylcarbodiimide hydrochloride (EDC) dissolved in MilliQ water. Next, we mixed 1 ml of the prepolymer, 50 mM of MES buffer, 1.83 mM of ADH, and 18.9 µM of EDC. Shaking was critical to avoid early crosslinking before freezing the sample. We filled polydimethylsiloxane (PDMS) circular moulds (chambers measuring 2 mm in height and 10 mm in diameter, enclosed between two squared 24x24 mm cover glasses) with the final prepolymer solution. Then, we stored the samples at -20 ºC for 24 hours. Finally, we thawed the resulting cryogels at room temperature and sterilised them by autoclave.