Measuring Particle Size Distribution by Asymmetric Flow Field Flow Fractionation: A Powerful Method for the Preclinical Characterization of Lipid-Based Nanoparticles.

Particle size distribution and stability are key attributes for the evaluation of the safety and efficacy profile of medical nanoparticles (Med-NPs). Measuring particle average size and particle size distribution is a challenging task which requires the combination of orthogonal high-resolution sizing techniques, especially in complex biological media. Unfortunately, despite its limitations, due to its accessibility, low cost, and easy handling, batch mode dynamic light scattering (DLS) is still very often used as the only approach to measure particle size distribution in the nanomedicine field. In this work the use of asymmetric flow field flow fractionation coupled to multiangle light scattering and dynamic light scattering detectors (AF4-MALS-DLS) was evaluated as an alternative to batch mode DLS to measure the physical properties of lipid-based nanoparticles. A robust standard operating procedure (SOPs) developed by the Nanomedicine Characterization Laboratory (EUNCL) was presented and tested to assess size stability, batch to batch consistency, and the behavior of the lipid-based nanoparticles in plasma. Orthogonal sizing techniques, such as transmission electron microscopy (TEM) and particle tracking analysis (PTA) measurements, were performed to support the results. While batch mode DLS could be applied as a fast and simple method to provide a preliminary insight into the integrity and polydispersity of samples, it was unsuitable to resolve small modifications of the particle size distribution. The introduction of nanoparticle sorting by field-flow fractionation coupled to online DLS and MALS allowed assessment of batch to batch variability and changes in the size of the lipid nanoparticles induced by the interaction with serum proteins, which are critical for quality control and regulatory aspects. In conclusion, if a robust SOP is followed, AF4-MALS-DLS is a powerful method for the preclinical characterization of lipid-based nanoparticles.

Transport of nanoparticulate TiO2 UV-filters through a saturated sand column at environmentally relevant concentrations.

The fate of sunscreen residues released during bathing activities around recreational areas is an emerging concern regarding the potential ecotoxicity of some of their ingredients, including nanoparticulate TiO2 UV-filters. To assess the extent of contamination in the natural medium, sand-packed column experiments were carried out with bare TiO2 engineered nanoparticles (ENPs) and two commercial nano-TiO2 UV-filters coated with either SiO2 (hydrophilic) or a combination of Al2O3 and simethicone (amphiphilic). The high sensitivity of (single particle)ICPMS online monitoring of the breakthrough curves made it possible to inject the ENPs at trace levels (2-100 µg L-1) in eluents composed of 10-3 and 10-2 M NaCl and pHs of 5.7 and 7.8. The deposition of all ENPs in the sand increased with the ionic strength and decreased with the pH of the carrier. Both bare and SiO2-coated ENPs showed a clear control by the electrostatic interactions between the particles and the quartz grains surfaces, in partial agreement with classical DLVO theory. Unexpectedly high rates of transfer were observed with the amphiphilic UV-filter, which could be explained by the addition of a contribution to the DLVO model to account for the steric repulsion between the sand collector and the polysiloxane surface layer of this ENP. These results demonstrate the major role played by the coating of UV-filters regarding their fate in porous media like soils, sediments and aquifers.

Chitosan-lipid nanoparticles (CS-LNPs): Application to siRNA delivery.

To benefit from the biocompatibility of lipid nanoparticles associated with the transfection ability of chitosan, small chitosan lipid nanoparticles (CS-LNPs) dedicated to SiRNA delivery were formulated by an easy-to-implement one-step process. Formulations of CS-LNPs (lipid core stabilized by a shell comprising phospholipids/cationic lipids and hydrophobically modified chitosan) were optimized for their physico-chemical properties (size, zeta potential, colloidal stability) according to their shell composition. In particular, amphiphilic chitosan with various molecular weight and C12 degrees of substitution, and different phospholipids and cationic lipids (lecithin, DOTAP, DOPE) were included at the particle surface at different ratios. The ability of the particles for SiRNA complexation, NIH3T3 cell transfection, and ERK1 downregulation, were studied. Lipid nanoparticles formulated with 15,000g/mol 2% C12 substituted chitosan, DOTAP and DOPE, mediated 40% ERK1 downregulation efficiency, comparable to lipofectamine™ RNAimax, while displaying no cytotoxicity up to 500µg/mL.