Biology subjects

Sui, K.

Publications and source records attributed to Sui, K..

6 recordsLinked to original sources

bioRxiv2024

Soft biocompatible polymer optical fiber tapers for implantable neural devices

Optical fibers are between the most common implantable devices for delivering light in the nervous system for optogenetics and infrared neural stimulation applications. Tapered optical fibers, in particular, can offer homogeneous light delivery to a large volume and spatially resolved illumination compared to standard flat-cleaved fibers while being minimally invasive. However, the use of tapers for neural applications has up to now been limited to silica optical fibers, whose large Youngs modulus can cause detrimental foreign body response in chronic settings. Here, we present the fabrication and optimization of tapered fiber implants based on polymer optical fibers (POFs). After numerically determining the optimal materials and taper geometry, we fabricated two types of POFs by thermal fiber drawing. The fabrication of the taper was achieved by chemical etching of the fibers, for which several solvents previously reported in literature have been tested. The influence of different parameters on the etching process and on the quality of the obtained tapers was also investigated. The large illumination volume of the produced high-quality taper-based implants was finally tested in vitro in a brain phantom.

neuroscience↗

bioRxiv2024

Lifting the degeneracy of optical fiber neural interfaces for optogenetics and electrophysiology by using axialtrodes

Modulating and recording neuronal activity are essential for probing brain function and developing therapies for neurological disorders. However, conventional flat-end optical fibers--widely used for deep brain access-- interact with neural tissue only at their distal tip, limiting spatial resolution across brain layers. To overcome this constraint, we introduce the microfluidic axialtrode: a soft, multimodal neural interface created by controllably angle-cleaving a thermally drawn, multimaterial optical fiber integrated with multiple metal electrodes and microfluidic channels. We demonstrate in vivo that this design enables spatially distributed optogenetics, multisite electrophysiological recording, and targeted drug delivery along the fibers axis, allowing simultaneous interaction with multiple neuronal layers. The axial configuration increases the functional interface with brain tissue, while the soft polymer construction and reduced cross-sectional footprint significantly suppress the inflammatory response compared to conventional silica fibers. Integration with a 3D-printed scaffold, fabricated from FDA-approved biocompatible resin, provides mechanical stability and compatibility with standard experimental hardware. The monolithic integration of these features positions the axialtrode as a scalable and versatile platform for next-generation neural interfacing.

neuroscience↗

bioRxiv2024

In vivo evaluation of thermally drawn biodegradable optical fibers as brain neural interfaces

Optical fiber technology has a critical role in modern neuroscience towards understanding the complex neuronal dynamics within the nervous system. In this study, we manufactured amorphous thermally drawn poly D, L-lactic acid (PDLLA) optical fibers in different diameters. These fibers were then implanted into the lateral posterior (LP) region of the mouse brain for 4 months, allowing us to assess their degradation characteristics. The gradual dissolution of the implanted PDLLA optical fibers in the brain was confirmed by optical microscope and scanning electron microscopy (SEM), molecular weight measurements, and light transmission spectroscopy. The results indicate that the degradation rate was mainly pronounced during the first week. Degradation after 4 months resulted in the formation of micropores on the surface of the implanted fiber within the gray matter region of the brain. Moreover, the current PDLLA optical fiber implant offers efficient light transmission in the short-wavelength near-infrared (SW-NIR) range. SW-NIR enables deeper tissue penetration and reduced light scattering, making it ideal for optogenetics and functional imaging with therapeutic potential in neurological disorders. We believe that the provided PDLLA optical fiber in this study constitutes a promising candidate for the development of next-generation biocompatible, soft, and biodegradable bi-directional neural interfaces

bioengineering↗

bioRxiv2024

Mid-infrared photoacoustic brain imaging enabled by cascaded gas-filled hollow-core fiber lasers

SignificanceExtending the photoacoustic microscopy (PAM) into the mid-infrared (MIR) molecular fingerprint region constitutes a promising route towards label-free imaging of biological molecular structures. Realizing this objective requires a high-energy nano-second MIR laser source. However, existing MIR laser technologies are limited to either low pulse energy or free-space structure which is sensitive to environmental conditions. Fiber lasers are promising technologies for PAM for their potential of offering both high pulse energy and robust performance against environmental conditions. However, MIR high energy fiber laser has not yet been used for PAM because it is still at the infant research stage. AimWe aim to employ the emerging gas-filled anti-resonant hollow-core fiber (ARHCF) laser technology for MIR-PAM for the purpose of imaging myelin-rich regions in a mouse brain. ApproachThis laser source is developed with a [~]2.75 J high-pulse-energy nano-second laser at 3.4 m, targeting the main absorption band of myelin sheaths, the primary chemical component of axons in the central nervous system. The laser mechanism relies on two-orders gas-induced vibrational stimulated Raman scattering (SRS) for nonlinear wavelength conversion, starting from a 1060 nm pump laser to 1409 nm through the 1st order Stokes generation in the nitrogen-filled 1st stage ARHCF, then, from 1409 nm to 3.4 m through the 2nd stage hydrogen-filled ARHCF. ResultsThe developed Raman laser was used for the first time for transmission-mode MIR-PAM of mouse brain regions containing rich myelin structures. ConclusionsThis work pioneers the potential use of high-energy and nano-second gas-filled ARHCF laser source to MIR-PAM, with a first attempt to report this kind of fiber laser source for PAM of lipid-rich myelin regions in a mouse brain. The proposed ARHCF laser technology is also expected to generate high-energy pulses at the ultraviolet (UV) region, which can significantly improve the lateral resolution of the PAM.

neuroscience↗

bioRxiv2022

Mapping whole brain effects of infrared neural stimulation with positron emission tomography

The combination of neuroimaging and targeted neuromodulation is a crucial tool to gain a deeper understanding of neural networks at a circuit level. Infrared neurostimulation (INS) is a promising optical modality that allows to evoke neuronal activity with high spatial resolution without need for the introduction of exogenous substances in the brain. Here, we report the use of whole-brain functional [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) imaging during INS in the dorsal striatum, performed using a multifunctional soft neural probe. We demonstrate the possibility to identify multi-circuit connection patterns in both cortical and subcortical brain regions within a single scan. By using a bolus plus infusion FDG-PET scanning protocol, we were able to observe the metabolic rate evolution in these regions during the experiments and correlate its variation with the onset of the INS stimulus. Due to the focality of INS and the large amount of viable molecular targets for PET, this novel approach to simultaneous imaging and stimulation is highly versatile. This pilot study can pave the way to further understand the brain connectivity on a global scale.

neuroscience↗

bioRxiv2022

Opsin-free optical neuromodulation and electrophysiology enabled by a soft monolithic infrared multifunctional neural interface

Controlling neuronal activity with high spatial resolution using multifunctional and minimally invasive neural interfaces constitutes an important step towards developments in neuroscience and novel treatments for brain diseases. While infrared neuromodulation is an emerging technology for controlling the neuronal circuitry, it lacks soft implantable monolithic interfaces capable of simultaneously delivering light and recording electrical signals from the brain while being mechanically brain-compatible. Here, we have developed a soft fibre-based device based on high-performance thermoplastics which are >100-fold softer than silica glass. The presented fibre-implant is capable of safely neuromodulating the brain activity in localized cortical domains by delivering infrared laser pulses in the 2 m spectral region while recording electrophysiological signals. Action and local field potentials were recorded in vivo in adult rats while immunohistochemical analysis of the tissue indicated limited microglia and monocytes response introduced by the fibre and the infrared pulses. We expect our devices to further enhance infrared neuromodulation as a versatile approach for fundamental research and clinically translatable therapeutic interventions.

neuroscience↗