Figure 2a: ATR-FTIR spectra of GO, P123 and rGO-P123. Figure 2b: ATR-FTIR spectra of GO, PEI and rGO-PEI. These spectra confirm the obtention of the graphene oxide (GO), and the polymer-functionalized reduced graphene oxide (Pluronic P123, rGO-P123 and Polyethyleneimine, rGO-PEI).
Figure 3: Raman spectra of graphite, GO, rGO-P123 and rGO-PEI. The Raman results confirm the presence of the polymers on rGO.
Figure 4: PXRD patterns of grafite, GO, rGO-P123 and rGO-PEI. The Powder X-ray diffraction shows the GO was reduced and functionalized.
Figures 5 and 6: TEM images of rGO-P123 and rGO-PEI, respectively. TEM images showed a two-dimensional morphology composed of thin, wrinkled and overlapping sheet-like structures of rGO-P123 and rGO-PEI.
Figures 7 and 8: SEM images of rGO-P123 and rGO-PEI, respectively. SEM images of rGO-P123 and rGO-PEI revealed smooth, folded and crumpled sheet-like structures.
Figures 9a: TGA curves of rGO-P123 and precursors. Figure 9b: TGA curves of rGO-PEI and precursors. From TGA, an amount of 2.43 mg mg-1 of Pluronic® P123 was anchored on the surface of rGO to obtain rGO-P123, while 0.78 mg mg-1 of PEI recovered the rGO surface to yield rGO-PEI.
Figure 12: UV-Vis spectra of AmB dispersed in different proportions of PBS:DMSO. These spectra were performed to choose the best mixture of PBS and DMSO to ensure AmB will be used in its monomeric form.
Figure 14a: ATR-FTIR spectra of rGO-P123-AmB. Figure 14b: ATR-FTIR spectra of rGO-PEI-AmB. Figures 14 show AmB (amphotericin B) was incorporated in rGO-P123 and rGO-PEI.
Figure 15: Phase-contrast optical microscopy images of RAW264.7 macrophages: (a) control and (b) PBS:DMSO (60:40) control and after 72 h of treatment with (c) rGO-PEI 5 µg mL-1 , (d) rGO-P123 5 µg mL-1 , (e) rGO-PEI 15 µg mL-1 , (f) rGO-P123 15 µg mL-1 , (g) rGO-PEI-AmB 5 µg mL-1 and (h) rGO-P123-AmB 5 µg mL-1. Figure 15 shows the rGO-PEI is not toxic to the macrophages.
Figure 17a: Absorption spectra of AmB at different concentrations in PBS:DMSO (60:40) obtained at RT. Figure 17b: standard curve of AmB obtained from the absorption spectra using the absorption maximum at λ = 389 nm. This standard curve was used to estimate the amount of AmB loaded and released from rGO-P123-AmB and rGO-PEI-AmB.