The in vitro sustained release profile and antitumor effect of etoposide-layered double hydroxide nanohybrids

Abstract

Magnesium-aluminum layered double hydroxides intercalated with antitumor drug etoposide (VP16) were prepared for the first time using a two-step procedure. The X-ray powder diffraction data suggested the intercalation of VP16 into layers with the increased basal spacing from 0.84-1.18 nm was successful. Then, it was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, and transmission electron microscopy. The prepared nanoparticles, VP16-LDH, showed an average diameter of 62.5 nm with a zeta potential of 20.5 mV. Evaluation of the buffering effect of VP16-LDH indicated that the nanohybrids were ideal for administration of the drugs that treat human stomach irritation. The loading amount of intercalated VP16 was 21.94% and possessed a profile of sustained release. The mechanism of VP16-LDH release in the phosphate buffered saline solution at pH 7.4 is likely controlled by the diffusion of VP16 anions from inside to the surface of LDH particles. The in vitro cytotoxicity and antitumor assays indicated that VP16-LDH hybrids were less toxic to GES-1 cells while exhibiting better antitumor efficacy on MKN45 and SGC-7901 cells. These results imply that VP16-LDH is a potential antitumor drug for a broad range of gastric cancer therapeutic applications.

Keywords: antitumor effect; drug delivery; etoposide; layered double hydroxides; sustained release.

Figure 1

Molecular formula of etoposide (VP16). Abbreviation: VP16, etoposide.

Figure 2

X-ray powder diffraction patterns for Mg/Al-LDH and VP16-LDH. (A) X-ray powder diffraction pattern for Mg/Al-LDH. (B) X-ray powder diffraction pattern for VP16-LDH. Abbreviations: Mg/Al-LDH, magnesium-aluminum layered double hydroxides; LDH, layered double hydroxide; VP16, etoposide.

Figure 3

Schematic model of monolayer packing of VP16 drug molecules in the LDH interlayer space. Abbreviations: VP16, etoposide; LDH, layered double hydroxide.

Figure 4

The FT-IR spectra for VP16, VP16-LDH, and Mg/Al-LDH. (A) FT-IR spectra for VP16. (B) FT-IR spectra for VP16-LDH. (C) FT-IR spectra for Mg/Al-LDH. Abbreviations: VP16, etoposide; LDH, layered double hydroxide; Mg/Al-LDH, magnesium-aluminum layered double hydroxides; FT-IR, Fourier transform infrared.

Figure 5

TG/DTA curves of VP16-LDH. Abbreviations: au, arbitrary unit; TG, thermogravimetry; DTA, differential thermal analysis; VP16, etoposide; LDH, layered double hydroxide.

Figure 6

Particle size distribution and zeta potential distribution of LDH and VP16-LDH nanoparticles. (A and B) Particle size distribution and zeta potential distribution of LDH and (C and D) VP16-LDH nanoparticles. Abbreviations: VP16, etoposide; LDH, layered double hydroxide.

Figure 7

TEM images of nanohybrids. (A) Mg/Al-LDH crystals. (B) VP16-LDH nanohybrid crystals. Abbreviations: TEM, transmission electron microscope; Mg/Al-LDH, magnesium-aluminum layered double hydroxides; LDH, layered double hydroxide; VP16, etoposide.

Figure 8

Titration curves of VP16-LDH. Note: V represents the added volume of 1 mol/L HCl aqueous solution. Abbreviations: VP16, etoposide; LDH, layered double hydroxide.

Figure 9

The in vitro release profiles of VP16 from VP16-LDH and physical mixture in buffer solutions at different pH values. Abbreviations: VP16, etoposide; LDH, layered double hydroxide.

Figure 10

Fitting the VP16-LDH release data at ph 7.4 to different kinetic equations. (A) Zero-order, (B) first-order, (C) parabolic diffusion model, and (D) modified Freundlich model. Abbreviations: VP16, etoposide; LDH, layered double hydroxide; t, time.

Figure 11

Fitting the VP16-LDH release data at pH 4.6 to different kinetic equations. (A) Zero-order, (B) first-order, (C) parabolic diffusion model, and (D) modified Freundlich model. Abbreviations: VP16, etoposide; LDH, layered double hydroxide; t, time.

Figure 12

The effect of LDH, VP16, and VP16-LDH of different VP16 concentrations on GES-1 cells and MKN45 and SGC-7901 tumor cells after 48 hours of incubation. (A) Cytotoxicity of LDH, VP16, and VP16-LDH of different VP16 concentrations to GES-1 cells after 48 hours. The effect of LDH, VP16, and VP16-LDH of different VP16 concentrations on the growth of MKN45 (B) and SGC-7901 (C) tumor cells after 48 hours. Notes: Results represent the means of three independent experiments, and error bars represent the standard error of the mean. N = 3; *P < 0.05; **P < 0.001. Abbreviations: LDH, layered double hydroxide; VP16, etoposide.