Search

Variation of the brain temperature is strongly affected by blood flow, oxygen supply, and neural cell metabolism. Localized monitoring of the brain temperature is one of the most effective ways to correlate brain functions and diseases such as stroke, epilepsy, and mood disorders. While polymer optical fibers (POFs) are considered ideal candidates for temperature sensing in the brain, they have never been used so far in vivo. Here, we developed for the first, to the best of our knowledge, time an implantable probe based on a microstructured polymer optical fiber Bragg grating (FBG) sensor for intracranial brain temperature mapping. The temperature at different depths of the brain (starting from the cerebral cortex) and the correlation between the brain and body core temperature of a rat were recorded with a sensitivity of 33 pm/°C and accuracy <0.2°C. Our in vivo experimental results suggest that the proposed device can achieve real-time and high-resolution local temperature measurement in the brain, as well as being integrated with existing neural interfaces.

Optical neural interfaces combining optogenetics and electrophysiology have been demonstrated as powerful tools for distinguishing the causal roles of neural circuits in the nervous system. Functional optrodes for multipoint stimulation and recording have already been demonstrated in the brain. However, soft and flexible multimodal optrodes for the purpose of probing the spinal cord have remained undeveloped. Here, we present the design and fabrication of a novel optrode for multi-site optical stimulation and electrical recording in the spinal cord by combining optical fiber drawing of polymer material, laser micromachining, and integration of tungsten microelectrodes in a monolithic fiber-based structure. The results from space-resolved scattering measurements, electrochemical impedance spectroscopy, and an acute in vivo electrophysiology experiment in an anesthetized rodent suggest this probe as a potential novel interface, which can serve as a part of therapeutic strategies against neurological conditions and injury in the spinal cord. • A novel soft, spatially resolved optrode for the spinal cord has been developed. • The optrode is suitable for optical stimulation and electrophysiological recording. • In vivo electrophysiological recordings from a rat's spinal cord have been performed. [ABSTRACT FROM AUTHOR]

Abstract The production of chalcogenide microstructured optical fibers with low optical losses, due to the broad transparency window of these glasses in the mid-IR, can allow for new breakthroughs in various research fields, e.g. new mid-IR laser sources and mid-IR spectroscopy. In this framework, high purity chalcogenide glasses are needed in order to minimize absorption losses. In this study, Ge 10 As 22 Se 68 samples were prepared using a double distillation method, using different combinations of chlorides and metals as getters for the physico-chemical elimination of carbon, oxygen and hydrogen impurities. Comparing the attenuation spectra of the different samples, the choice of the getters seems to be indeed a significant factor in the quality of the glass. A holey fiber has been realized by casting method using the best sample, showing that the method is suitable for this composition and that the attenuation before and after the casting are comparable. Highlights • Synthesis of high purity chalcogenide glasses by double distillation was investigated. • The performances of different getters have been compared. • The chalcogenide MOF with lowest attenuation reported until now has been produced. [ABSTRACT FROM AUTHOR]

The mid-infrared spectral region is of great technical and scientific importance in a variety of research fields and applications. Among these studies, mid-infrared supercontinuum generation has attracted strong interest in the last decade, because of unique properties such as broad wavelength coverage and high coherence, among others. In this paper, the intrinsic optical properties of different types of glasses and fibers are presented. It turns out that microstructured chalcogenide fibers are ideal choices for the generation of mid-infrared supercontinua. The fabrication procedures of chalcogenide microstructured fibers are introduced, including purification methods of the glass, rod synthesis processes, and preform realization techniques. In addition, supercontinua generated in chalcogenide microstructured fibers employing diverse pump sources and configurations are enumerated. Finally, the potential of supercontinua for applications in mid-infrared imaging and spectroscopy is shown. [ABSTRACT FROM AUTHOR]

• We proposed a new CYTOP fiber-based implant for brain temperature measurement. • The brain temperature measurement is achieved by the inscribed fiber Bragg gratings. • The proposed implant is free from cross-sensitivity from humidity or microstrain. Brain temperature is a vital physiological parameter that has a great effect on metabolic processes, enzymatic activity, neurotransmitter function, blood flow regulation, neuroprotection, and cognitive performance. In this framework, the development of accurate and reliable brain temperature measurement tools is crucial in brain-related treatment and research, such as neurosurgery, therapeutic hypothermia, and the understanding of brain function and pathologies. Here, we developed the first large-core flexible low optical loss CYTOP polymer optical fiber (POF)-based brain temperature probe operating in the telecommunication spectral range. The temperature measurements were achieved by detecting the reflected spectrum from a fiber Bragg grating (FBG) directly inscribed at the tip of the POF using femtosecond pulses. A fluorinated ethylene propylene (FEP) tube was thermally drawn and used as a sleeve around the FBG structure to eliminate the cross-sensitivity with humidity and microstrain perturbations. The assembled POF implant has a sensitivity of 14.3 pm/°C. The local temperature of the cerebral cortex, corpus callosum, and striatum in a rat brain was measured in vivo. The results indicate that the deep brain regions have higher temperature than the top cortical ones with a relatively linear relationship between the brain structure depth and its temperature. In addition, the rectal body core temperature was detected in parallel with the brain temperature measurement to further validate the developed device. We believe that the presented CYTOP POF-based implantable temperature probe opens the way towards the development of flexible and stable tools for accurate brain temperature recording where large-core fiber-based neural devices are required. [ABSTRACT FROM AUTHOR]