Abstract
The manipulation of brain nerve terminals by an external magnetic field promises breakthroughs in nano-neurotechnology. D-Mannose-coated superparamagnetic nanoparticles were synthesized by coprecipitation of Fe(II) and Fe(III) salts followed by oxidation with sodium hypochlorite and addition of D-mannose. Effects of D-mannose-coated superparamagnetic maghemite (γ-Fe2O3) nanoparticles on key characteristics of the glutamatergic neurotransmission were analysed. Using radiolabeled L-[14C]glutamate, it was shown that D-mannose-coated γ-Fe2O3 nanoparticles did not affect high-affinity Na+-dependent uptake, tonic release and the extracellular level of L-[14C]glutamate in isolated rat brain nerve terminals (synaptosomes). Also, the membrane potential of synaptosomes and acidification of synaptic vesicles was not changed as a result of the application of D-mannose-coated γ-Fe2O3 nanoparticles. This was demonstrated with the potential-sensitive fluorescent dye rhodamine 6G and the pH-sensitive dye acridine orange. The study also focused on the analysis of the potential use of these nanoparticles for manipulation of nerve terminals by an external magnetic field. It was shown that more than 84.3 ± 5.0% of L-[14C]glutamate-loaded synaptosomes (1 mg of protein/mL) incubated for 5 min with D-mannose-coated γ-Fe2O3 nanoparticles (250 µg/mL) moved to an area, in which the magnet (250 mT, gradient 5.5 Т/m) was applied compared to 33.5 ± 3.0% of the control and 48.6 ± 3.0% of samples that were treated with uncoated nanoparticles. Therefore, isolated brain nerve terminals can be easily manipulated by an external magnetic field using D-mannose-coated γ-Fe2O3 nanoparticles, while the key characteristics of glutamatergic neurotransmission are not affected. In other words, functionally active synaptosomes labeled with D-mannose-coated γ-Fe2O3 nanoparticles were obtained.
Highlights
Nanoparticles have great biotechnological potential opening a wide range of new applications
The neat γ-Fe2O3 nanoparticles were used in control experiments with cells or were used as a base for the subsequent modification with D-mannose, hindering the agglomeration of the particles when stored for long time
It can be concluded that we obtained normally functioning synaptosomes labeled with D-mannosecoated γ-Fe2O3 nanoparticles, which can be manipulated by an external magnetic field
Summary
Nanoparticles have great biotechnological potential opening a wide range of new applications. Superparamagnetic iron oxide nanoparticles are considered as promising candidates to increase the efficiency of targeted drug delivery not because of the possibility to attach antibodies to their surfaces, and because of the possibly to use external magnetic guidance [3]. A key issue for enhancing of permeability of iron oxide nanoparticles through the cell membrane is the modification of their surface. In this context, biocompatible polymers can be attached to the surface of the nanoparticles to avoid their agglomeration and enhance their non-specific intracellular uptake [4]. Magnetic resonance imaging could be used for tracking labeled cells in vivo by using iron oxide nanoparticles coated by dextran [5,6]. Until the discontinuation of their manufacture, they had been used for study of migration of Endorem-labeled cells to a cortical photochemical lesion or compression of a spinal cord lesion in rats [8,9]
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