Biology subjects

Sileo, L.

Publications and source records attributed to Sileo, L..

6 recordsLinked to original sources

bioRxiv2022

Deep brain cancer metastasis detection with wide-volume Raman spectroscopy through a single tapered fiber

We propose a low-invasive method to enable implantable, large volume Raman spectroscopy in arbitrarily deep brain regions of the mouse brain. Using a single tapered fiber as thin as 1 m at the tip, we identified diagnostic markers of brain metastasis - the most frequent brain tumor in human adults - with overall accuracy [≥] 90%. We view our approach as a promising complement to the existing palette of tools for optical interrogation of the brain.

neuroscience↗

bioRxiv2020

Integrated tapered fibertrode for simultaneous control and readout of neural activity over small brain volumes with reduced light-induced artefacts

Recognizing the neural patterns underlying different brain functions is essential to achieve a more comprehensive view on how small sets of neurons organize in complex 3D networks to determine different behaviours. In this framework, optogenetic techniques have been successfully proven as a powerful tool to control brain functions achieving millisecond temporal resolution and cell-type specificity, by combining the use of light-gated opsins and ad-hoc light delivery optoelectronic devices. However, targeting small brain volumes with simultaneous electrical recording results in the introduction of photoelectric artefacts, in particular when light emission and recoding sites are very close one to each other. In this work we take advantage of the photonic properties of tapered fibers to present a fully integrated fibertrode to target small brain volumes with abated photoelectric noise. The device hosts a light emitting window just below a recording pad, and exploits the angled light emission from the window to achieve simultaneous activation and electrical readout of small groups of cells with no photoelectric artifacts in vivo. Despite the highly non-planar surface of the fiber taper, windows size, shape and electrodes impedance can be modulated by controlling the fabrication parameters during focused ion beam milling and deposition, thus resulting in a versatile, integrated and customizable optogenetic tool for neurobiology studies in closed-loop configuration over small brain volumes.

neuroscience↗

bioRxiv2020

Ray tracing models for estimating light collection properties of microstructured tapered optical fibers for optical neural interfaces

Tapered optical fibers (TFs) were recently employed for depth-resolved monitoring of functional fluorescence in sub-cortical brain structures, enabling light collection from groups of a few cells through small optical windows located on the taper edge [1]. Here we present a numerical model to estimate light collection properties of microstructured TFs implanted in scattering brain tissue. Ray tracing coupled with Henyey-Greenstein scattering model enables the estimation of both light collection and fluorescence excitation fields in three dimensions, whose combination is employed to retrieve the volume of tissue probed by the device.

bioengineering↗

bioRxiv2018

Multipoint and large volume fiber photometry with a single tapered optical fiber implant

Techniques to monitor functional fluorescence signal from the brain are increasingly popular in the neuroscience community. However, most implementations are based on flat cleaved optical fibers (FFs) that can only interface with shallow tissue volumes adjacent to the fiber opening. To circumvent this limitation, we exploit modal properties of tapered optical fibers (TFs) to structure light collection over the wide optically active area of the fiber taper, providing an approach to efficiently and selectively collect light from the region(s) of interest. While being less invasive than FFs, TF probes can uniformly collect light over up to 2 mm of tissue and allow for multisite photometry along the taper. Furthermore, by micro-structuring the non-planar surface of the fiber taper, collection volumes from TFs can also be engineered arbitrarily in both shape and size. Owing to the abilities offered by these probes, we envision that TFs can set a novel, powerful paradigm in optically targeting not only the deep brain, but, more in general, any biological system or organ where light collection from the deep tissues is beneficial but challenging because of tissue scattering and absorption.

neuroscience↗

bioRxiv2017

Exploiting modal demultiplexing properties of tapered optical fibers for tailored optogenetic stimulation

Optogenetic control of neural activity in deep brain regions requires precise and flexible light delivery with non-invasive devices. To this end, Tapered Optical Fibers (TFs) represent a minimally-invasive tool that can deliver light over either large brain volumes or spatially confined subregions. This work links the emission properties of TFs with the modal content injected into the fiber, finding that the maximum transversal propagation constant (kt) and the total number of guided modes sustained by the waveguide are key parameters for engineering the mode demultiplexing properties of TFs. Intrinsic features of the optical fiber (numerical aperture and core/cladding diameter) define the optically active segment of the taper (up to [~]3mm), along which a linear relation between the propagating set of kt values and the emission position exists. These site-selective light-delivery properties are preserved at multiple wavelengths, further extending the range of applications expected for tapered fibers for optical control of neural activity.

neuroscience↗

bioRxiv2016

Dynamically controlled light delivery over large brain volumes through tapered optical fibers

Optogenetics promises spatiotemporal precise control of neural processes using light. However, the spatial extent of illumination within the brain is difficult to control and cannot be adjusted using standard fiber optics. We demonstrate that optical fibers with tapered tips can be used to illuminate either large brain volumes or dynamically selectable subregions. Remotely adjusting the light input angle to the fiber varies the light-emitting portion of the taper over several millimeters without movement of the implant. We use this mode to activate dorsal versus ventral striatum of individual mice and reveal different effects of each manipulation on motor behavior. Conversely injecting light over the full numerical aperture of the fiber results in light emission from the entire taper surface, achieving broader and more efficient optogenetic activation of neurons when compared to the standard flat-faced fiber stimulation. Thus, tapered fibers permit focal or broad illumination that can be precisely and dynamically matched to experimental needs.

neuroscience↗