Paracrine signalling of inflammatory cytokines from an in vitro blood brain barrier model upon exposure to polymeric nanoparticles

Abstract

Nanoparticle properties, such as small size relative to large highly modifiable surface area, offer great promise for neuro-therapeutics and nanodiagnostics. A fundamental understanding and control of how nanoparticles interact with the blood-brain barrier (BBB) could enable major developments in nanomedical treatment of previously intractable neurological disorders, and help ensure that nanoparticles not intended to reach the brain do not cause adverse effects. Nanosafety is of utmost importance to this field. However, a distinct lack of knowledge exists regarding nanoparticle accumulation within the BBB and the biological effects this may induce on neighbouring cells of the Central Nervous System (CNS), particularly in the long-term. This study focussed on the exposure of an in vitro BBB model to model carboxylated polystyrene nanoparticles (PS COOH NPs), as these nanoparticles are well characterised for in vitro experimentation and have been reported as non-toxic in many biological settings. TEM imaging showed accumulation but not degradation of 100 nm PS COOH NPs within the lysosomes of the in vitro BBB over time. Cytokine secretion analysis from the in vitro BBB post 24 h 100 nm PS COOH NP exposure showed a low level of proinflammatory RANTES protein secretion compared to control. In contrast, 24 h exposure of the in vitro BBB endothelium to 100 nm PS COOH NPs in the presence of underlying astrocytes caused a significant increase in pro-survival signalling. In conclusion, the tantalising possibilities of nanomedicine must be balanced by cautious studies into the possible long-term toxicity caused by accumulation of known 'toxic' and 'non-toxic' nanoparticles, as general toxicity assays may be disguising significant signalling regulation during long-term accumulation.

Size, shape, and flexibility influence nanoparticle transport across brain endothelium under flow

“…Carboxylated polystyrene (PS) nanoparticles were chosen as a model particle due to their low toxicity in many biological systems, their negligible degradation over the timescales being studied, and their widespread use in research settings, which has resulted in thorough characterization and a diverse body of work to facilitate comparisons …”

Central nervous system toxicity of metallic nanoparticles

“…Transferrin-containing gold NPs can enter and accumulate in the brain parenchyma after systemic administration in mice through a receptor-mediated transcytosis pathway. 5 Furthermore, the accumulation of 100 nm PS-COOH NPs within the lysosomes of the in vitro BBB was observed by Raghnaill et al 6 Iron oxide (IO) NPs, ZnO NPs, and titanium dioxide (TiO 2 ) NPs have also been found to be translocated to the brain in various animal models. observed the accumulation of TiO 2 NPs in the mouse hippocampus after intragastric administration, and this accumulation led to hippocampal apoptosis and impairment in spatial recognition memory.…”

A TEM protocol for quality assurance of in vitro cellular barrier models and its application to the assessment of nanoparticle transport mechanisms across barriers

“…1), 10,11 epithelial and endothelial cells established on transwells are usually polarised and prompted to communicate (via signalling molecules) between the apical and basolateral chambers, such that they can acquire sufficient differentiation to function as barriers. [7][8][9][12][13][14] Tight junctions expressed in these in vitro models are usually thought to be a critical standard with which to discriminate a welldifferentiated barrier from loosely associated barriers. Due to cell polarisation, endogenous bio-markers, such as junctional proteins, and transport related proteins that are specifically expressed in vivo, are subsequently expressed in these barriers.…”