Optimization of a Solid-Phase Extraction Procedure for the Analysis of Drug-Loaded Lipid Nanoparticles and its Application to the Determination of Leakage and Release Profiles

Abstract

To understand and predict the efficacy and toxicity of nanoparticle-based drugs in vivo, the free and entrapped forms of the drug have to be determined using suitable characterization methods. Herein, a solid-phase extraction (SPE) method combined with high-performance liquid chromatography (HPLC) measurements were used to separately quantify free and entrapped cyclosporine A (CsA) in 50 and 120 nm-sized lipid nanoparticles (NPs). Combined with colloidal stability measurements, HPLC quantification of the free and entrapped drug, separated using SPE, was used to monitor the stability of the nanotherapeutics under storage or physiological conditions. The SPE method was proven not to alter the core-shell template of the lipid nanocarriers. Method validation demonstrated suitable linearity, repeatability, accuracy, and specificity to quantify the free, entrapped, and total drug. Under storage conditions, the %free and %entrapped CsA remained constant over 9 weeks for both NPs. Under physiological conditions, the release profile was similar for both buffers/mediums used, indicating a biphasic mode of release. The validated SPE method was proven to be suitable for the determination of a wide range of free versus entrapped compounds.

Keywords: Lipid nano-emulsion; Quality control; Separation techniques; Stability.