Characterization of different functionalized lipidic nanocapsules as potential drug carriers

Abstract

Lipid nanocapsules (LNC) based on a core-shell structure consisting of an oil-filled core with a surrounding polymer layer are known to be promising vehicles for the delivery of hydrophobic drugs in the new therapeutic strategies in anti-cancer treatments. The present work has been designed as basic research about different LNC systems. We have synthesized-and physico-chemically characterized-three different LNC systems in which the core was constituted by olive oil and the shell by different phospholipids (phosphatidyl-serine or lecithin) and other biocompatible molecules such as Pluronic(®) F68 or chitosan. It is notable that the olive-oil-phosphatidyl-serine LCN is a novel formulation presented in this work and was designed to generate an enriched carboxylic surface. This carboxylic layer is meant to link specific antibodies, which could facilitate the specific nanocapsule uptake by cancer cells. This is why nanoparticles with phosphatidyl-serine in their shell have also been used in this work to form immuno-nanocapsules containing a polyclonal IgG against a model antigen (C-reactive protein) covalently bounded by means of a simple and reproducible carbodiimide method. An immunological study was made to verify that these IgG-LNC complexes showed the expected specific immune response. Finally, a preliminary in vitro study was performed by culturing a breast-carcinoma cell line (MCF-7) with Nile-Red-loaded LNC. We found that these cancer cells take up the fluorescent Nile- Red molecule in a process dependent on the surface properties of the nanocarriers.

Keywords: drug delivery; immuno-nanocapsules; lipid nanocapsules; nanocarriers.

Figure 1

Transmission electron microscopy photography of the EPI nanocapsules.

Figure 2

Absorbance change after 300 s (λ = 570 nm) due to aggregation induced by different C-reactive protein (CRP) concentrations: (○) PhS-1 mgIgG/m²; (□) PhS-2.5 mgIgG/m². Reaction medium: 13 mM borate (pH 8.0), 150 mM NaCl, 1 mg/mL NaN₃, 1 mg/mL BSA. The starting point of optical absorbance for all experiments was 0.5.

Figure 3

Electrophoretic mobility vs. pH for (▵) EPI; (□) CS; and (○) PhS nanocapsules.

Figure 4

Electrophoretic mobility vs. pH for (■) PhS; (○) PhS-1 mgIgG/m²; and (▵) PhS-2.5 mgIgG/m² IgG.

Figure 5

Stability factor vs. calcium chloride concentration (mM) at pH 7.4: (■) 1 mg/m² IgG-PhS; (●) 2.5 mg/m² IgG-PhS. Solid lines help to locate the CCC values, while dashed lines point to the CSC data.

Figure 6

Aggregation kinetics of the (□) EPI; (○) CS; (▵) PhS; (■) PhS-1 mg/m² IgG; and (●) PhS-2.5 mg/m² IgG nanocapsules when immersed in DMEM medium supplemented with fetal bovine serum (FBS).

Figure 7

Emission spectrum of Red Nile in olive oil and water, and inside different nanoparticles. (black line) EPI; (dashed line) CS; (dotted line) PhS; (dash-dot line) Olive oil; (gray line) water.

Figure 8

Relative fluorescent intensity of the MCF7 cell line when incubated with Nile-Red-loaded nanocapsules for 30 min and 2 h. Control refers to that incubation performed only with cells.

Figure 9

Scheme detailing the preparation of the particles.