The samples dispersed in the gel-precursor solutions were diluted 100 times using the same alkaline buffer and placed inside the cuvettes for the measurement of ζ-potential in a Malvern Zetasizer Nano (Alfatest, Milan, Italy). Analyses were performed at 25 °C and average and standard deviation values were calculated with Excel (n = 6). TEM analyses TEM micrographs were acquired on Jeol, JEM 2100, Japan, at 100 kV. TEM grids (SPI, West Chester, USA) were treated for 20 min in a UV-ozone cleaner (UV-Ozone Procleaner Plus) to make the grids hydrophilic. Sample aliquots (~20 μL) were deposited on top of a copper grid for 30 s. Then, water was precisely removed from the gel samples and the grid was placed for 30 s in contact onto a drop of 2%