Biology subjects

Balena, A.

Publications and source records attributed to Balena, A..

4 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↗

bioRxiv2021

Influence of anatomical features of different brain regions on the spatial localization of fiber photometry signals

Fiber photometry is widely used in neuroscience labs for in vivo detection of functional fluorescence from optical indicators of neuronal activity with a simple optical fiber. The fiber is commonly placed next to the region of interest to both excite and collect the fluorescence signal. However, the path of both excitation and fluorescence photons is altered by the uneven optical properties of the brain, due to local variation of the refractive index, different cellular types, densities and shapes. Nonetheless, the effect of the local anatomy on the actual shape and extent of the volume of tissue that interfaces with the fiber has received little attention so far. To fill this gap, we measured the size and shape of fiber photometry efficiency field in the primary motor and somatosensory cortex, in the hippocampus and in the striatum of the mouse brain, highlighting how their substructures determine the detected signal and the depth at which photons can be mined. Importantly, we show that the information on the spatial expression of the fluorescent probes alone is not sufficient to account for the contribution of local subregions to the overall collected signal, and it must be combined with the optical properties of the tissue adjacent to the fiber tip.

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↗