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.