Criteria impacting the cellular uptake of nanoparticles: a study emphasizing polymer type and surfactant effects.

A detailed understanding of the particle-cell interaction is essential and of immense interest in order to create a "specific carrier" for each particular application. In this paper, the effect of the surfactant type (non-ionic vs ionic) and polymer nature on the cellular uptake of fluorescent polystyrene and poly(L-lactide) nanoparticles was studied on HeLa cells. Nanoparticles in a size range from 100 to 160 nm were synthesized by the miniemulsion process. The particles were detected in cells by confocal laser scanning fluorescence microscopy and flow cytometry. It was found that the influence of the surface charge is greater than that of the polymer type itself. In fact, particles stabilized with cationic surfactant were incorporated in a large number irrespective of polymer type. Cellular pathways at ultrastructural level were studied by transmission electron microscopy in more detail to shed light on the particle-cell interaction based on the material properties. The criteria governing the cellular uptake of nanoparticles based on the polymer and surfactant types are finally established.

Disposition of charged nanoparticles after their topical application to the skin.

The objective of this preliminary investigation was to examine the disposition of charged nanoparticles on and within the skin following their topical application and to explore whether the formulations have potential utility for the local delivery of an associated 'active' substance. Three nanoparticles (approx. 100 nm in diameter) were investigated: cationic amino-functionalized polystyrene, an anionic carboxyl-functionalized polystyrene and anionic poly-(L-lactide), into each of which the fluorophore N-(2,6-diisopropylphenyl)perylene-3,4-dicarboximine (PMI) was incorporated. Formulations were applied to excised porcine skin in vitro for 6 h. After cleaning the skin surface following treatment, the skin was either examined by laser scanning confocal microscopy or subjected to repeated tape-stripping and subsequent analysis of the removed stratum corneum (SC) for the presence of PMI. The cationic nanoparticles showed clear affinity for the negatively charged skin surface (in contrast to the anionic carriers) and delivered a significantly greater amount of the model 'active' agent (PMI) into the SC.