Magnetic nanoparticles in primary neural cell cultures are mainly taken up by microglia

Abstract

Background Magnetic nanoparticles (MNPs) offer a large range of applications in life sciences. Applications in neurosciences are one focus of interest. Unfortunately, not all groups have access to nanoparticles or the possibility to develop and produce them for their applications. Hence, they have to focus on commercially available particles. Little is known about the uptake of nanoparticles in primary cells. Previously studies mostly reported cellular uptake in cell lines. Here we present a systematic study on the uptake of magnetic nanoparticles (MNPs) by primary cells of the nervous system. Results We assessed the internalization in different cell types with confocal and electron microscopy. The analysis confirmed the uptake of MNPs in the cells, probably with endocytotic mechanisms. Furthermore, we compared the uptake in PC12 cells, a rat pheochromocytoma cell line, which is often used as a neuronal cell model, with primary neuronal cells. It was found that the percentage of PC12 cells loaded with MNPs was significantly higher than for neurons. Uptake studies in primary mixed neuronal/glial cultures revealed predominant uptake of MNPs by microglia and an increase in their number. The number of astroglia and oligodendroglia which incorporated MNPs was lower and stable. Primary mixed Schwann cell/fibroblast cultures showed similar MNP uptake of both cell types, but the Schwann cell number decreased after MNP incubation. Organotypic co-cultures of spinal cord slices and peripheral nerve grafts resembled the results of the dispersed primary cell cultures. Conclusions The commercial MNPs used activated microglial phagocytosis in both disperse and organotypic culture systems. It can be assumed that in vivo application would induce immune system reactivity, too. Because of this, their usefulness for in vivo neuroscientific implementations can be questioned. Future studies will need to overcome this issue with the use of cell-specific targeting strategies. Additionally, we found that PC12 cells took up significantly more MNPs than primary neurons. This difference indicates that PC12 cells are not a suitable model for natural neuronal uptake of nanoparticles and qualify previous results in PC12 cells.

Development of a nanomaterial bio-screening platform for neurological applications

“…Parallel derivation of all glial types for the model from a single primary source, as achieved here, avoids problems with cell lines which are often of unknown provenance (origin and treatment history) 31 and altered physiology, 32 potentially leading to dramatically different nanoparticle uptake dynamics and toxicity profiles compared with primary cells. 16 Our method also ensures that constituent cells possess identical ages/anatomical origins, with culture under identical conditions. Further, by achieving defined cellular stoichiometry with high reproducibility, direct intercellular comparisons can be reliably drawn.…”

“…12 In terms of widely used current approaches, live animal models are biologically relevant but involve significant ethical issues, technical complexity and expense, whilst being low-throughput. 16 and reducing their predictive utility.…”

New findings about iron oxide nanoparticles and their different effects on murine primary brain cells

“…[18][19][20] SPIOs are taken up by activated microglia in primary and mixed cell cultures in a time-, concentration-, and temperaturedependent manner. 21,22 This raises the possibility of sustained microglial activation that can prove to be severely disruptive to neural function. [23][24][25] Interestingly, other studies have demonstrated that cellular reactions critically depend on the respective particle properties, including composition, size, and biocompatibility.…”

Using a 3-D multicellular simulation of spinal cord injury with live cell imaging to study the neural immune barrier to nanoparticle uptake

“…Microglia have been shown to dominate uptake versus other neural cell types due to their comparatively rapid and extensive particle uptake profiles [9]. This has been demonstrated for different NP types, using defined glial co-cultures [9], undefined co-cultures of primary neurons and glial cells, and more complex transverse organotypic spinal cord slices (intact tissue) co-cultured with peripheral nerve grafts [10]. Together, it is estimated that the glial cells account for up to 99.5% of cellular uptake of NPs, with microglia shown to be responsible for the majority of this uptake in vivo [11].…”