Assessment of Gelation Kinetics and Stress-Relaxation Properties in Decellularized Lung Extracellular Matrix Hydrogels Using Oscillatory Rheology

1 Turn on the Discovery HR-2 Rheometer2 to implement oscillatory rheology measurements. 3 Pour 250 microliters of pre-gel digest solution 4 placed on ice onto a pre-cooled lower plate 5 to avoid rapid gelation. 6 Lower the 20 millimeter parallel plate 7 until the pre-gel solution forms a disc 8 with a one millimeter gap width between the two plates.

9 Set the strain at 0.1%and frequency to 0.5 hertz. 10 Measure storage and loss moduli over time 11 while heating the lower plate 12 to 37 degrees Celsius for 30 minutes 13 to observe gelation kinetics. 14 After the storage modulus value stops increasing 15 and reaches a plateau, 16 perform a creep recovery test 17 to assess the stress relaxation behavior of hydrogels.

18 Apply one Pascal shear stress to the hydrogel 19 for 15 minutes and measure the strain. 20 Then unload the sample from the stress 21 and record the change in strain values for 15 minutes. 22 Finally, draw a strain versus time graph 23 to show the stress relaxing behavior.

24 The average storage modulus 25 and loss modulus of hydrogels 26 produced by the freeze-thaw method 27 demonstrated significantly higher stiffness 28 compared to hydrogels produced 29 using the Triton X-100 method. 30 Creep recovery tests revealed 31 that hydrogels obtained from both methods 32 exhibited distinct stress responses 33 indicating different viscoelastic properties.