Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA105

Poster Communications

Metal oxide nanoparticles: size role in membrane interactions

D. Zanella3, E. Bossi3,1, R. Gornati3,1, N. Faria2, J. Powell2, G. Bernardini3,1

1. The Protein Factory Research Center, Politecnico of Milano and University of Insubria, Milan, Italy. 2. Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom. 3. Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy.

  • Fig.1: A) Membrane Parameters. Co3O4 NPs: Controls n=76, 5min n=25, 20 min n=30, Aggregated n=44, all from at least 2 batches. B) Co3O4 NPs Transmembrane Current Values: same n values reported in A. C) NiO NPs Transmembrane Current Values: Controls n=53, 5min n=34, 20min n=47, from 2 batches. Statistical analysis: One-Way ANOVA/Bonferroni-Holm post-hoc test

  • Fig.2: Hydrodynamic size determined over time by SLS (representative experiments)

Nano scale modifies the physical-chemical characteristics of metal particles in comparison with the original bulk materials and alters the type and scale of the interactions with biological materials. The modified properties may alter interactions with cell membranes allowing non-endocytotic nanoparticles (NPs) entrance. This pathway has been recently documented for commercially available Co3O4 and Fe3O4 NPs1,2. Metal oxide NPs have therefore been analysed, to investigate this mechanism of permeation that can be important both under the toxicological and the translational point of view. In the present work, cobalt and nickel-based NP interactions with Xenopus laevis oocyte membranes were characterized by Two-Electrode Voltage Clamp; resting potential, membrane capacitance, membrane resistance and current-voltage relationships were measured at different times from the beginning of the exposure to NPs, using the protocols described previously2. Oocytes exposed to Co3O4 NPs presented significant reductions of membrane resistance and resting potential within 5 min from the beginning of the treatment. These reductions disappeared in oocytes exposed for 20 min (Fig.1A). NiO NPs failed to elicit any relevant change in membrane parameters. Oocytes were then exposed to Co3O4 NPs in aggregated form (30 minutes after sonication NPs were aggregated), and no significant differences were measured in membrane resistance and resting potential, highlighting the role of particles characteristics in the first 5 min after sonication in determining the biological effects. The transmembrane currents at the voltage of-120 mV and +40 mV are reported in Fig.1B-C. Static Light Scattering (SLS) and Laser-Doppler Microelectrophoresis were used to determine the physical and chemical properties of the NPs in the experimental medium. Both NPs had neutral z-potentials (Co3O4 =0,5±0,05 mV and NiO =0,045±0,018 mV, n=3, mean±S.E.M.), thus aggregating in the medium. Hydrodynamic size distributions (Fig.2) showed differences among the NPs: Co3O4 NPs possessed a submicron population for at least 5 min and NiO NPs possessed a submicron population for 20 minutes. The submicron population of Co3O4 NPs was smaller than 200 nm, while NiO NPs were always above 250 nm. The main difference determined in physical and chemical properties between Co3O4 and NiO NPs is colloidal size, which is most likely to play a significant role in passive permeation mechanisms.

Where applicable, experiments conform with Society ethical requirements