Abstract
Time-resolved quantitative colocalization analysis is a method based on confocal fluorescence microscopy allowing for a sophisticated characterization of nanomaterials with respect to their intracellular trafficking. This technique was applied to relate the internalization patterns of nanoparticles i.e. superparamagnetic iron oxide nanoparticles with distinct physicochemical characteristics with their uptake mechanism, rate and intracellular fate.The physicochemical characterization of the nanoparticles showed particles of approximately the same size and shape as well as similar magnetic properties, only differing in charge due to different surface coatings. Incubation of the cells with both nanoparticles resulted in strong differences in the internalization rate and in the intracellular localization depending on the charge. Quantitative and qualitative analysis of nanoparticles-organelle colocalization experiments revealed that positively charged particles were found to enter the cells faster using different endocytotic pathways than their negative counterparts. Nevertheless, both nanoparticles species were finally enriched inside lysosomal structures and their efficiency in agarose phantom relaxometry experiments was very similar.This quantitative analysis demonstrates that charge is a key factor influencing the nanoparticle-cell interactions, specially their intracellular accumulation. Despite differences in their physicochemical properties and intracellular distribution, the efficiencies of both nanoparticles as MRI agents were not significantly different.
Highlights
The interaction of nanomaterials with cells and tissues is a key factor when considering their translation into clinical applications
Adsorptive attachment of poly(ethylene imine) (PEI) to stabilize the NPs in solution completed the synthesis of positively charged γ-Fe2O3-PEI NPs
It is important to point out that coupling PEI to the γ-Fe2O3 NPs turned out to be essential to stabilize the NPs generated by aqueous co-precipitation in solution
Summary
The interaction of nanomaterials with cells and tissues is a key factor when considering their translation into clinical applications. An effective accumulation of nanoparticles (NPs) inside certain tissues is beneficial for a great number of applications, such as hyperthermia, contrast enhancement in magnetic resonance imaging, cell tracking or theranostics [1,2,3,4,5,6,7]. Cationic NPs have been found to display excellent properties for tracking applications as they enter cells with higher effectiveness [12] due to the interaction with the negatively charged glycocalix [13]. Negatively charged NPs are massively incorporated by cells In this respect it has to be mentioned that charged NPs strongly interact with serum proteins to form a protein corona [18,19,20,21], whose formation depends on the NP charge. The rate of NP uptake is important, as insufficient cellular accumulation of NPs e.g. magnetic NPs can lead to deficient usage for example as imaging probes [22]
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