Gemcitabine-Loaded Magnetically Responsive Poly(ε-caprolactone) Nanoparticles against Breast Cancer

Abstract

A reproducible and efficient interfacial polymer disposition method has been used to formulate magnetite/poly(ε-caprolactone) (core/shell) nanoparticles (average size ≈ 125 nm, production performance ≈ 90%). To demonstrate that the iron oxide nuclei were satisfactorily embedded within the polymeric solid matrix, a complete analysis of these nanocomposites by, e.g., electron microscopy visualizations, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, electrophoresis, and contact angle goniometry was conducted. The magnetic responsive behaviour of these nanoparticles was quantitatively characterized by the hysteresis cycle and qualitatively investigated by visualization of the colloid under exposure to a 0.4 T magnet. Gemcitabine entrapment into the polymeric shell reported adequate drug loading values (≈11%), and a biphasic and pH-responsive drug release profile (≈ four-fold faster Gemcitabine release at pH 5.0 compared to pH 7.4). Cytotoxicity studies in MCF-7 human breast cancer cells proved that the half maximal inhibitory concentration of Gem-loaded nanocomposites was ≈ two-fold less than that of the free drug. Therefore, these core/shell nanoparticles could have great possibilities as a magnetically targeted Gemcitabine delivery system for breast cancer treatment.

Keywords: Gemcitabine; breast cancer; core/shell; drug loading; magnetic drug delivery; magnetite; pH-responsive drug release; poly(ε-caprolactone); polymer-coated nanoparticle.

Figure 1

(a) Chemical co-precipitation to prepare Fe₃O₄ nanoparticle (NPs) [32], and, (b) formulation of the core/shell NPs by interfacial polymer disposition [25,27]. Inset: structure of the Gemcitabine (Gem)-loaded Fe₃O₄/poly(ε-caprolactone) (PCL) (core/shell) NPs.

Figure 2

(a) Zeta potential (ζ, mV) of the nanocomposites of Fe₃O₄:PCL weight proportions ranging from 4:1 to 1:4, Fe₃O₄ NPs, and PCL NPs, in water (pH ≈ 6), and (b) zeta potential (ζ, mV) of Fe₃O₄ NPs (○), PCL NPs (□), and Fe₃O₄/PCL NPs (▲, of 2:4 Fe₃O₄:PCL weight ratio) as a function of the molar concentration of KNO₃ at pH ≈ 6. Lines are a guide to the eye and have no other significance.

Figure 3

(a) High resolution transmission electron microscopy (HRTEM) and (b) high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images of the magnetic nanocomposites (of 2:4 Fe₃O₄:PCL weight ratio); (c) energy dispersive X-ray (EDX) Fe element mapping analysis of the sample in (b), and (d) EDX spectra of these particles. Bar lengths: 50 nm.

Figure 4

Infrared spectra of Fe₃O₄ NPs (black line), PCL NPs (light grey line), and nanocomposites (dark grey line, of 2:4 Fe₃O₄:PCL weight ratio).

Figure 5

(a) Contact angle (θ, degrees) of water, formamide, and diiodomethane on Fe₃O₄, PCL, and Fe₃O₄/PCL (of 2:4 Fe₃O₄:PCL weight ratio) particle layers, and (b) ΔG_SLS (solid–liquid interfacial energy of interaction) values (mJ/m²) and hydrophobic/hydrophilic character of the NPs.

Figure 6

In vitro release of Gem (%) from the magnetic nanocomposites (of 2:4 Fe₃O₄:PCL weight ratio), as a function of the incubation time at 37.0 ± 0.5 °C, in citrate-phosphate buffers of 7.4 ± 0.1 (∆) and of pH 5.0 ± 0.1 (▲). Inset: Gem released (%) up to t = 10 h.

Figure 7

In vitro cytotoxicity of the Fe₃O₄/PCL NPs (of 2:4 Fe₃O₄:PCL weight ratio) in: (a) CCD-18 human colon fibroblast cells, and (b) MCF-7 human breast cancer cells. Cell lines were kept in contact with the particles for 48 h (black column) and 72 h (light grey column).

Figure 8

In vitro cytotoxicity of free Gem (black column) and Gem-loaded magnetic nanocomposites (of 2:4 Fe₃O₄:PCL weight ratio) (light grey column) in MCF-7 human breast cancer cells, after 72 h of exposure to a wide range of NP concentrations (up to 25 μM equivalent Gem concentration). Statistical analysis was done using Student’s t-test considering 95% confidence interval. The statistical test was significant, ** p < 0.05, compared with the free Gem-treated group.

Figure 9

(a) Hysteresis cycle of the Fe₃O₄/PCL NPs (of 2:4 Fe₃O₄:PCL weight ratio, ▲); (b) visual observation of an aqueous dispersion (0.5%, w/v) of these particles on a 400 mT permanent magnet (located close to the right lateral flat surface of the glass vial), and (c) optical microphotographs of the aqueous colloids under the influence of this magnetic field (in the direction of the arrow).