Evaluation of pegylated lipid nanocapsules versus complement system activation and macrophage uptake

Pegylated Nanocapsules Produced by an Organic Solvent-Free Method: Evaluation of their Stealth Properties

PURPOSE

To develop from an original process, a novel generation of stealth lipidic nanocapsules in order to improve the lipophilic drug delivery in accessible sites.

MATERIALS AND METHODS

Nanocapsules covered by PEG1500 stearate were obtained by a low energy emulsification method. Conductivity measurements and ternary diagram were performed to describe the formulation mechanism. Hemolytic dosage CH50 and pharmacokinetic study in rats have been achieved in order to study the stealth properties of nanocapsules.

RESULTS

Transition from an O/W emulsion to a w/O/W emulsion was necessary to produce PEG1500 stearate nanocapsules. Interestingly nanocapsules with a size around 26 nm and a polydispersity index inferior to 0.1 were obtained. The CH50 test has revealed a very weak complement consumption in the presence of such nanocapsules. Moreover, after intravenous injection into rats, PEG1500 stearate nanocapsules exhibited long circulating properties. The experimental data support the concept of steric repulsion of the surface towards proteins, displayed by nanocapsules covered with PEG1500 stearate. These in vivo results were in agreement with the PEG1500 density calculated at the nanocarrier surface.

CONCLUSIONS

Injectable drug carriers have been developed. Their long-circulating properties could confer them a strong potential for lipophilic drug targeting.

Parameters influencing the stealthiness of colloidal drug delivery systems

Over the last few decades, colloidal drug delivery systems (CDDS) such as nano-structures have been developed in order to improve the efficiency and the specificity of drug action. Their small size permits them to be injected intravenously in order to reach target tissues. However, it is known that they can be rapidly removed from blood circulation by the immune system. CDDS are removed via the complement system and via the cells of the mononuclear phagocyte system (MPS), after their recognition by opsonins and/or receptors present at the cell surface. This recognition is dependent on the physicochemical characteristics of the CDDS. In this study, we will focus on parameters influencing the interactions of opsonins and the macrophage plasma membrane with the surface of CDDS, whereby parameters of the polymer coating become necessary to provide good protection.