Abstract
Magnetosomes are membrane-enclosed iron oxide crystals biosynthesized by magnetotactic bacteria. As the biomineralization of bacterial magnetosomes can be genetically controlled, they have become promising nanomaterials for bionanotechnological applications. In the present paper, we explore a novel application of magnetosomes as nanotool for manipulating axonal outgrowth via stretch-growth (SG). SG refers to the process of stimulation of axonal outgrowth through the application of mechanical forces. Thanks to their superior magnetic properties, magnetosomes have been used to magnetize mouse hippocampal neurons in order to stretch axons under the application of magnetic fields. We found that magnetosomes are avidly internalized by cells. They adhere to the cell membrane, are quickly internalized, and slowly degrade after a few days from the internalization process. Our data show that bacterial magnetosomes are more efficient than synthetic iron oxide nanoparticles in stimulating axonal outgrowth via SG.
Highlights
IntroductionThe mechanosensitivity of cells determines a specific response to mechanical stimulation
We developed a new methodology for stretching the axon shaft from the “inside” by developing a force of about 10 pN, which is similar or lower than those endogenously generated by the growth cone, pointing that the generation of such extremely low mechanical forces is an endogenous mechanism of axonal outgrowth [5,6]
Many studies demonstrated that magnetic nanoparticles are an efficient tool for magnetizing axons, and the subsequent application of a magnetic field gradient can generate such extremely low forces that drive productive axonal outgrowth [5,6,56,66,67]
Summary
The mechanosensitivity of cells determines a specific response to mechanical stimulation. Mechanosensitivity is essential to all cells, studies were mainly devoted to clarify signal mechanotransduction in those cells that play a fundamentally mechanical role. In the last decades, the pivotal role of mechanical force in the neuron development has been clarified and has attracted much attention. Neurons are mechanosensitive cells over three distinct ranges of force magnitude [4]. They are even more mechanosensitive than other non-neuronal cell type, by sensing, probing and responding to pico-Newton (pN) forces [5]. Our team demonstrated that the generation of pN forces modulates neurite elongation, sprouting, and neuron maturation [5,6]
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