2.10. Turbidimetric Gelation Kinetics

ECM hydrogel gelation kinetics were evaluated by means of turbidimetric analysis, according to experimental methods already reported by several studies [27,28,29]. Optical density was measured at 405 nm from 100 μL samples of neutralized dECM of three different batches in triplicate (total amount of 9 samples) every 5 min for up to 2 h using a pre-heated to 37 °C UV-visible spectrophotometer (TECAN Spark Control, Mannedorf, Switzerland). Mean absorbance values and standard error of the mean (s.e.m.) were calculated from test repetitions at each time point. Normalized absorbance (An) was determined by the following equation:

where At is the absorbance measured at a specific time point, A0 is the initial absorbance, and Amax is the maximum absorbance. Gelation kinetics parameters were calculated from experimental curves: the time to half gelation t1/2 was defined as the time when 50% of the maximum absorbance value is measured, the gelation rate (S) was defined as the slope of the linear region of the gelation curve, and the lag time (tlag) was defined as the intercept of the line with S slope with 0% absorbance.