Folic Acid-conjugated Graphene Oxide loaded with Photosensitizers for Targeting Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) has emerged as an alternative and promising noninvasive treatment for cancer as well as non-cancer diseases, which involves the uptake of photosensitizers (PSs) by cancer cells followed by irradiation. The use of nanomaterials as carriers of PSs is a very promising approach to improve the development of PDT in clinical medicine. In this study, a novel folic acid-conjugated graphene oxide (GO) was strategically designed and prepared as targeting drug delivery system to achieve higher specificity. The second generation photosensitizer (PS) Chlorin e6 (Ce6) was effectively loaded into the system via hydrophobic interactions and π-π stacking. The nanocarriers can significantly increase the accumulation of Ce6 in tumor cells and lead to a remarkable photodynamic efficacy on MGC803 cells upon irradiation. These suggested that folic acid-conjugated GO loaded Ce6 had great potential as effective drug delivery system in targeting PDT.

Keywords: Chlorin e6; Drug delivery.; Folic acid; Graphene oxide; Photodynamic therapy.

Fig A

Scheme 1 Chemical structure of Ce6.

Fig B

Scheme 2. Photosensitizers Ce6 loaded by folic acid-conjugated graphene oxide.

Fig 1

(a) A tapping mode AFM image of graphene oxide (GO) sheets on mica surface, (b) the height profile of the AFM image, (c) TEM image of the GO, and (d) SEM image of the GO.

Fig 2

UV-vis spectra of the GO (1) and FA-GO (2) in aqueous solution.

Fig 3

Absorption spectra (a) and Fluorescence emission spectra (b) of FA-GO (1), Chlorin e6 (Ce6) (2), and FA-GO-Ce6(3) in water (The inset is the photographs of GO, FA-GO, and FA-GO-Ce6 in tubes).

Fig 4

Changes of the zeta potential of the GO-Ce6 composite suspensions as a function of the component ratio and illustration of formation the GO-Ce6 composite.

Fig 5

Selective uptake of GO-Ce6 and FA-GO-Ce6 in MGC803 cells at 30 min incubation of 50 μg/mL different nanocarriers (left: bright field, right: fluorescence). (a,b) Cells were treated with GO-Ce6 in RPMI-1640 medium without FA. (c,d) Cells were treated with FA-GO-Ce6 in RPMI-1640 medium with FA. (e,f) Cells were treated with FA-GO-Ce6 in RPMI-1640 medium without FA. All cells monitored by fluorescence microscopy.

Fig 6

The typical fluorescence emission spectra (a) and fluorescence image (b) of Cells treated with FA-GO-Ce6 in RPMI-1640 medium without FA.

Fig 7

TEM images of MGC803 cells incubated with 100 μL of FA-GO-Ce6 (50 μg/mL) for 24 h. (a,c) Low magnification; (b,d) High magnification. Arrows denote the FA-GO-Ce6. “pm” and “num” stand for plasma membrane and nuclear membrane.

Fig 8

In vitro photodynamic efficacy of FA-GO-Ce6. MGC803 cells were incubated with 0-100 μM FA-GO-Ce6 for 24 h at 37 ˚C in the dark prior to irradiation for 10 min with 632.8-nm He-Ne laser. Cell viability was determined by MTT assay. Data represent mean ± SD (n = 3). P < 0.05 for nonirradiated group versus irradiated group.

Fig C

Scheme 3. FA-GO-Ce6 endocytosed by MGC803 cells, endosome-containing FA-GO-Ce6 complexes were located around the nucleus, Ce6 escaped from the endosome into the cytoplasm.