*2.3. Zeta Potential*

A 6 mg amount of elastin was dissolved in a 3 mL phosphate buffer (pH 7.5, 400 mM) at 4 ◦C. Additionally, 3 mL of collagen (1 mL R and 2 mL G, each 4 mg/mL stock solution) was mixed with 3 mL of the phosphate buffer (pH 7.5, 400 mM) at 4 ◦C. Both solutions were subjected to zeta potential measurements on a NanoZS (Malvern) zetasizer with a backscatter optical arrangement (173◦). Each condition was measured three times by preparing a fresh solution each time. Each sample (1 mL) was left for 120 s in the instrument, which was precooled at 4 ◦C, to reach the thermal equilibrium. Each sample was measured eight times with twenty runs and a 30 s delay between the measurements.
