br Further the Raman spectra help
Further, the Raman spectra help to study the structural variations
Fig. 2. XRD spectra of graphite, GO and RGO prepared by Euphorbia milii leaf extract.
Fig. 3. Raman spectra of graphite, GO before and after reduction by Euphorbia milii leaves extract.
before and after the GO reduction. Raman spectra of graphite, GO, and after reduction by Euphorbia milii leaves extract were presented in Fig. 3. As presumed, the graphite Raman spectrum has exhibited a significant G-band at about 1582 cm−1 which upon reduced by Eu-phorbia milii leaf extract, the peak became wide and shifted to 1597 cm−1 followed by prominent D-peak. Interestingly, the Raman spectrum of RGO presented an elevated D/G intensity ratio in QC 6352 to GO (0.94) with the increase in the D/G intensity ratio (0.98, 1.02, 1.08, and 1.17) with the increase of time. This variation attributes to the change in the electronic conjugation state, which in turn implies the raise in the number of sp2 carbon with the GO deoxygenating by Eu-phorbia milii leaves extract.
The TEM images representing the surface morphology of the GO and RGO were represented in Fig. 4. Initially the surface of the GO na-nosheet as shown in Fig. 4a, was smooth. Furthermore, after the
addition of Euphorbia milii leaves extract to the GO solution, followed by incubation for respective time, the GO nanosheet surface became rough (Fig. 4b). Thus there is an apparent evidence of assembly of plant polyphenols the GO nanosheet surface. AFM imaging was further performed in order to analyze the surface roughness of GO nanosheet as well as to know the mean thickness of the GO and RGO prepared using Euphorbia milii leaves extract. The thick-nesses of pure GO was observed to be around 1 nm, which was uniform throughout the height of mono-layer graphene sheet as shown in Fig. 5. Moreover, the thickness of RGO after loading with paclitaxel drug ef-ficiently increased to 10–15 nm, which attributed to the protein at-tachment on the GO nanosheet surface.
Fig.6 displayed the FT-IR spectra for GO, RGO, and RGO/PTX. As shown in Fig.6, GO exhibited the C]O stretching vibration peaks were
Fig. 5. AFM images and height profiles for (A) RGO and (B) PTX drug loaded RGO.
Fig. 7. Graph representing cell viability as a function of (a) RGO and (b) RGO/PTX in culture media.
PTX spectrum, could be accredited to the CeO ester, –COO, CeH aro-matic, C]O amide, and C]O ester respectively. Therefore, from this data, we could conclude the efficient loading of Paclitaxel on RGO.
The free RGO presented no substantial cytotoxicity against A549-Human lung cancer cell lines as shown in Fig. 7(A). However, as in Fig. 7(B), after the addition of RGO/PTX, an evident decline in the cell viability was noticed. Further with the increase in the concentration of RGO/PTX to 200??g/mL, the cell viability reduced to 29%. Even more increase in the concentration to 500??g/mL of RGO/PTX, the cell via-bility also showed rapid reduction to 10%. Based on this, we can con-clude that the increased concentration of RGO/PTX decreased the cell viability of A549 cell lines tremendously.
Fluorescence microscopic examination was also performed to fur-ther confirm the cell viability results. As shown in Fig. 8(A), control group has presented the largest number of viable cells. Further addition of RGO at different concentrations like 1??g/mL, 10??g/mL, and 100??g/mL, A549 cells evidenced no apparent morphological varia-tions (Fig. 8B-C). A maximum viable cell count was exhibited in the control group as in Fig. 9(A). While increase in the concentration of RGO/PTX to100??g/mL, the viable A549 cells declined rapidly as in Fig. 9(B). However, even more increase in the concentration of RGO/ PTX to 200 and 500??g/mL, very limited number of viable cells was observed which were represented in Figs. 9(C) and 9(D). Based on these experimental findings, it was obvious that RGO/PTX demonstrated very significant antitumor efficacy against A549 cells thus could be an ideal choice for tumor-targeted chemotherapy.
In conclusion, RGO nanosheets loaded with PTX were efficiently prepared by making use of Euphorbia milii leaves extract. Thus obtained RGO/PTX nanosheets were characterized to study their structural morphology and were further investigated for their cytotoxicity assay against A549cell lines. Even with low concentrations (200??g/mL), the RGO/PTX have reported momentous inhibition of the growth rate of A549 cells. Henceforth, RGO/PTX nanocomposites as expected have significant potential to be used in the lung carcinoma targeted che-motherapy.
Authors are thankful to the National Natural Science Foundation Project (NO.81273647), the Fujian Natural Science Foundation Project (NO.2013J01365), the Key Project of the Youth Talents of the Fujian Health System (2015-ZQN-ZD-2), the Co-construction Science Project of the National Commission of Health and Family Planning (WKJ-FJ-19) for providing fund and research facilities to do this research work.