Figure 4. Particle size distribution of modified hydrogels and starting materials (A) and surface charge of different hydrogels and their components (B).
The samples were dissolved in methanol, and the size distribution and ζ potential were recorded. The measurement for ALG shows particles with a large size of 1540 nm. The ζ potential measured consistently higher value of -13.8 mV. The particle size measured for VG is 280 nm and has a relatively high ζ potential value of +34.9. As Figure 4 shows, the size distribution for VGALG revealed a particle size of 485 nm, and a ζ potential of -19.8 mV, indicating the robust binding of VG to ALG. The polydispersity index (PDI), a parameter for non-uniform particle distribution, shows a slightly higher result of 0.580, which also supports the non-uniform distribution of VGALG particles in the dissolution media. The measured size distribution for VGCB8ALG was 165 nm, and the ζ potential value shifted to +14.4 mV, indicating the guest-host interaction in VGCB8ALG.[12] The manipulation in the size and charge of hydrogels upon the addition of CB8 explains the results of cellular internalization below.
Optical Properties (Functionalization, Encapsulation, Implementation for Cellular Uptake, and Rigidity Enhancement)
The solid UV–Visible spectra (Figure S4 in the Supporting Information) showed a slight difference in the band gap (0.06 eV) between the two hydrogels with the addition of CB8. Yet, both indicated distinct optical properties with onsets at approximately 700 nm compared to the published data for unmodified ALG with 212 and 271 nm peaks.[30]
The excitation and emission spectra were recorded for the new hydrogels VGALG and VGCB8ALG in Figure 5 and found to be consistent with the solid UV–Visible data.