Enabling magnetic resonance imaging of hollow-core microstructured optical fibers via nanocomposite coating

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.

Functionalized Microstructured Optical Fibers: Materials, Methods, Applications

“…The light-guiding mechanism in such fibers is described via Fabry-Perot resonances. In accordance with this model, the maximal decoupling of the core and cladding modes that correspond to the maxima in the fiber transmission occurs at: In contrast to conventional optical fibers made from silica and its doped materials, where lightguiding is achieved through total internal reflection, MOFs and their group of hollow-core MOFs (HC-MOFs) represent a separate class of photonic bandgap fibers, for which the guidance is accomplished by coherent Bragg scattering [8,33] that forms well-defined permitted and prohibited regions for photon propagation within the central core of the fiber [1,15]. This results in the appearance of transmission peaks and dips in the spectra of HC-MOFs, demonstrating that only specific wavelength bands are confined into the central core and allowed to propagate [34,35].…”

“…The further development of MOF-based sensors gave rise to a new research direction for the tuning of optical properties. Various approaches have been proposed and realized for MOF modification [77]; different solid [15,16,[78][79][80][81] and liquid materials [82] were injected into the fiber hollow regions. Among others, one can highlight such well-described approaches for the injection of host materials such as pressure-assisted melt filling ( Figure 12) [79], chemical vapor deposition [83], and direct fiber drawing [77].…”

“…Recently, the technique of polyelectrolyte LBL deposition, originally applied for the preparation of nanofilms [13,58] and later used for the formation of microcapsules [91][92][93][94], as well as the functionalization of planar surfaces [95], have been adapted for the surface modification of optical fibers [96]. These can either be buffer layers [15,16] with a controlled value of surface potential for better particle adsorption or the sensitive layers by themselves [97]. A nanoscale thickness accuracy is possible by varying a set of parameters such as, among others polyelectrolyte concentration, adsorption time, ionic strength, solvent composition, and temperature [58].…”

“…A technique that allows magnetic resonance imaging of hollow-core MOF samples was demonstrated for the case of LBL assembly of oppositely charged polyelectrolytes and magnetite nanoparticles on the inner surface of hollow-core, opening new prospects for fiber-based endoscopic devices with magnetic resonance imaging that can potentially lead to minimally invasive medical diagnostics and surgical procedures in vivo [15]. Based on a similar approach of host materials deposition inside MOF samples, we reported a novel type of functionalized MOF sample whose capillaries were coated with silica submicron particles (SiO 2 ) with different diameters (300, 420, and 900 nm) and layers of poly(diallyldimethylammonium chloride).…”

“…In this work, we review the various types of functionalization techniques of MOFs that have enabled the improvement of their performance and have created new perspectives for the use of cases of plasmonic nanoparticles and metal nanowires. The novel technique of layer-by-layer (LBL) [13] deposition, previously used mainly for the deposition of thin films onto planar substrates and adapted for the functionalization of fiber surfaces, in order to make the attachment of target molecules or particles possible, or for the creation of areas sensitive to a specific medium, is also considered [14][15][16]. This review concentrates on the different methods used for the modifications of optical fibers and highlights the novel functionalities which go beyond the manipulation of transmitted light, revealing the innovative applications of these structures, rather than investigating the origins of the underlying physical phenomena.…”