Polyethylene Glycol-Chitosan Oligosaccharide-Coated Superparamagnetic Iron Oxide Nanoparticles: A Novel Drug Delivery System for Curcumin Diglutaric Acid

Abstract

Curcumin diglutaric acid-loaded polyethylene glycol-chitosan oligosaccharide-coated superparamagnetic iron oxide nanoparticles (CG-PEG-CSO-SPIONs) were fabricated by co-precipitation and optimized using a Box-Behnken statistical design in order to achieve the minimum size, optimal zeta potential (≥ ±20 mV), and maximum loading efficiency and capacity. The results demonstrated that CG-PEG-CSO-SPIONs prepared under the optimal condition were almost spherical in shape with a smooth surface, a diameter of 130 nm, zeta potential of 30.6 mV, loading efficiency of 83.3%, and loading capacity of 8.3%. The vibrating sample magnetometer results of the optimized CG-PEG-CSO-SPIONs showed a superparamagnetic behavior. Fourier transform infrared spectroscopy and X-ray diffraction analyses indicated that the CG physically interacted with PEG-CSO-SPIONs. In addition, the CG-PEG-CSO-SPIONs could be stored dry for up to 12 weeks or in aqueous solution for up to 4 days at either 4 °C or 25 °C with no loss of stability. The CG-PEG-CSO-SPIONs exhibited a sustained release profile up to 72 h under simulated physiological (pH 7.4) and tumor extracellular (pH 5.5) environments. Furthermore, the CG-PEG-CSO-SPIONs showed little non-specific protein binding in the simulated physiological environment. The CG-PEG-CSO-SPIONs enhanced the cellular uptake and cytotoxicity of CG against human colorectal adenocarcinoma HT-29 cells compared to free CG, and more CG was delivered to the cells after applying an external magnetic field. The overall results suggest that PEG-CSO-SPIONs have potential to be used as a novel drug delivery system for CG.

Keywords: chitosan oligosaccharide; curcumin diglutaric acid; drug delivery systems; polyethylene glycol; superparamagnetic iron oxide nanoparticles.

Figure 1

Chemical structure of curcumin diglutaric acid (CG).

Figure 2

Plackett-Burman: Pareto charts revealing the significance of the factors on the determined responses. Significance of the given factor (X_1–5) on the particle size (Y₁), zeta potential (Y₂), LE (Y₃), and LC (Y₂). The blue and orange colors indicated the negative and positive effects, respectively. The transparency inside both blue and orange demonstrated the mainly significant effect at p < 0.05.

Figure 3

The 3D-RSPs and contour plots showing the effects of the CTAB (X₁), CSO (X₂), and PEG (X₃) concentrations on the responses of the (A–D) particle size (Y₁), (E–H) zeta potential (Y₂), (I–L) LE (Y₃), and (M–P) LC (Y₄).

Figure 4

Representative TEM images (8000× magnification) of (A) SPIONs and (B) CG-PEG-CSO-SPIONs.

Figure 5

Representative FT-IR spectra of the CG powder; PEG-CSO-SPIONs and CG-PEG-CSO-SPIONs.

Figure 6

Representative XRD patterns of SPIONs, PEG-CSO-SPIONs; CG powder, and CG-PEG-CSO-SPIONs.

Figure 7

Representative VSM analysis showing the magnetic behavior of (A) SPIONs and CG-PEG-CSO-SPIONs and (B) the localization of CG-PEG-CSO-SPIONs near an external magnet. (M−) Without magnet; (M+) with magnet.

Figure 8

In vitro cumulative CG release from CG-PEG-CSO-SPIONs in the pH 5.5 and 7.4 RM over 72 h. Data are shown as the mean ± SD from three replications.

Figure 9

In vitro protein (BSA) binding onto the (A) CSO-SPIONs; PEG-CSO-SPIONs; CG-PEG-CSO-SPIONs, and (B) a representative TEM image of the CG-PEG-CSO-SPIONs before and after incubation with the BSA solution.

Figure 10

Particle size and zeta potential of CG-PEG-CSO-SPIONs after (A) four days of aqueous storage (short term stability) and (B) after 12 weeks of dry storage (long term stability) at 4 °C or 25 °C. Data are shown as the mean ± SD, derived from three replications.

Figure 11

HT-29 cell viability after treatment with control (PEG-CSO-SPIONs), free CG, and CG-PEG-CSO-SPIONs for 24 h. Data are shown as the mean ± SD, derived from four trials.

Figure 12

Representative CLSM images of CG uptake by HT-29 cells after 24 h of treatment with CG-PEG-CSO-SPIONs or free CG.

Figure 13

Magnetic targeting delivery analyzed in terms of the (A) HT-29 cell viability using the MTT assay (data are shown as the mean ± SD, derived from 3 trials) and (B) representative CLSM images of HT-29 cells after incubation with free CG or CG-PEG-CSO-SPIONs at 40 µg CG/mL for 24 h with (M+) or without (M−) an external magnetic field.