Abstract
Optical fibers are widely used in bioimaging systems as flexible endoscopes that are capable of low-invasive penetration inside hollow tissue cavities. Here, we report on the technique that allows magnetic resonance imaging (MRI) of hollow-core microstructured fibers (HC-MFs), which paves the way for combing MRI and optical bioimaging. Our approach is based on layer-by-layer assembly of oppositely charged polyelectrolytes and magnetite nanoparticles on the inner core surface of HC-MFs. Incorporation of magnetite nanoparticles into polyelectrolyte layers renders HC-MFs visible for MRI and induces the red-shift in their transmission spectra. Specifically, the transmission shifts up to 60 nm have been revealed for the several-layers composite coating, along with the high-quality contrast of HC-MFs in MRI scans. Our results shed light on marrying fiber-based endoscopy with MRI to open novel possibilities for minimally invasive clinical diagnostics and surgical procedures in vivo.
Highlights
Optical bioimaging via using fibre-optic endoscopes has supplied a large number of opportunities for retrieving information from remote and delicate places enabling accurate visualization of pathologies, neural activity, tissue structure and many others
We consider the hollow-core microstructured fibers (HC-MFs) containing five functional concentric layers of capillaries and the external buffer layer (Fig. 1 (a)) drawn from the custom-made soft glass with the refractive index n = 1.519 at the wavelength 550 nm [24]
We start with hermetic coupling of the HC-MF to the pipette dispenser tip which is used to fill the fiber with polyelectrolytes and magnetite nanoparticles (MNPs)
Summary
Optical bioimaging via using fibre-optic endoscopes has supplied a large number of opportunities for retrieving information from remote and delicate places enabling accurate visualization of pathologies, neural activity, tissue structure and many others. The study of so complex system as a brain in vivo whose functioning is still mainly unknown requires extremely exact spatial operating with endoscopic probes in real time Such opportunity can be provided by magnetic resonance imaging (MRI). LbLA is realized by the “bottom-up” principle, allowing accurate variations in the thickness and the chemical composition of the coating as well as the volume fraction of nanoparticles This technique has been applied to cover glass, quarz and silicon substrates by composite multilayers containing polyelectrolytes and MNPs [10,11,12,13,14]. As contrast agents for MRI, we chose magnetite (Fe3O4) nanoparticles which are fully compatible with our technique of LbLA and have a strong magnetic susceptibility The latter, in particular, provides a large signal-to-noise ratio, allowing for visibility of HC-MFs in lowmagnetic-field MRI scanners.
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