Optical Signal Changes Research Articles

Dual-mode iodine sensing: Colorimetric and electrochemical detection methods using functionalized gold nanoparticles

Iodine in natural and treated waters exists mainly as iodide, iodate, and molecular iodine (I2). I2 is a highly volatile and reactive species impacting biological and chemical systems. Iodine, a vital micronutrient, is essential for human and animal growth and metabolism. It also plays a crucial role in synthesising artificial adrenaline within the metabolic processes of humans and animals. It is also widely used as an antiseptic, disinfectant, and for emergency water disinfection. Moreover, iodine deficiency can result in various diseases, especially hypothyroidism and goitre. Given its critical functions, it is imperative to have a straightforward, dependable, and efficient method for monitoring iodine levels. This study introduces a simple and innovative I2 detection system based on its reactivity, toxicity, and role as an indicator of oxidative conditions in water. It operates in terms of based on optical and electrochemical signal changes, utilising the anti-aggregation mechanism of gold nanoparticles (AuNPs) and 6-mercaptohexanol (MHA) for sensitive and selective detection under mild conditions. I2 determination is achieved by observing the colour change in AuNPs, which is influenced by competitive interactions between MHA, I2, and AuNPs. The optical detection system, with its low detection limit (LOD=260 nM), is based on the straightforward observation of colour changes. On the other hand, the electrochemical detection method utilises changing redox peaks observed in anodic region, providing selective and sensitive I2 detection (LOD=100 nM). The probe effectively detects the presence of I2 in real water samples as a practical application. Moreover, the proposed method revolutionises I2 detection by incorporating a smartphone for signal reading, eliminating the need for specialised equipment and significantly reducing the detection cost. This cost-effective approach carries the potential to expedite on-site and naked-eye I2 detection, opening up new possibilities for research and application.

Deciphering the Interplay between Local and Global Dynamics of Anodic Metal Oxidation.

The stark difference between global and local metal oxidation dynamics underscores the need for methodologies capable of performing precise sub-μm-scale and wide-field measurements. In this study, we present reflective microscopy as a tool developed to address this challenge, illustrated by the example of chronoamperometric Fe oxidation in a NaCl solution. Analysis at a local scale of 10 s of μm has revealed three distinct periods of Fe oxidation: the initial covering of the metal interface with a surface film, followed by the electrochemical conversion of the formed surface film, and finally, the in-depth oxidation of Fe. In addition, thermodynamic calculations and the quantitative analysis of changes in optical signal (light intensity), correlated with variations in refractive indexes, suggest the initial formation of maghemite, followed by its subsequent conversion to magnetite. The reactivity maps for all three periods are heterogeneous, which can be attributed to the preferential oxidation of certain crystallographic grains. Notably, at the global scale of 100 s of μm, reactivity initiates at the electrode border and progresses toward its center, demonstrating a unique pattern that is independent of the local metal structure. This finding underscores the significance of simultaneously employing sub-μm-precise, quantitative, and wide-field measurements for a comprehensive description of metal oxidation processes.

Development of dual-mode ELISA based on ALP-catalyzed APP hydrolysis for IL-6 detection

Sensitive and accurate detection of interleukin 6 (IL-6) is crucial for the early diagnosis of cerebral infarction to improve patient survival rates. However, the low-abundance of IL-6 in cerebral infarction presents a significant challenge in developing effective diagnosis method. Herein, we studied and analyzed the strong fluorescence property of 4-aminophenol phosphate (APP) and developed an enzyme-linked immunosorbent assay (ELISA) for IL-6 detection. The detection was based on the integration of optical signal change induced by alkaline phosphatase (ALP)-catalyzed APP hydrolysis and ALP-mediated ELISA. The generated colorimetric signal of 4-aminophenol, APP hydrolysis product, was used for ELISA of IL-6 with a detection limit of 0.1 ng/mL, and the visual detection of IL-6 was achieved. The changes in APP fluorescence have a good linear relationship with the logarithm of IL-6 concentration in the range of 0.005 ng/mL to 5.0 ng/mL, with a detection limit of 0.001 ng/mL, which was 100 times lower than that of conventional pNPP-based ELISA. Furthermore, the constructed ELISA effectively distinguished between samples from patients with cerebral infarction and volunteers with non-cerebral infarction, and the severity of symptoms was well distinguished based on IL-6 measurement. The dual-mode ELISA demonstrated high feasibility of low-abundance biomarker detection and displayed good potential for accurate in vitro diagnosis.

Spectral analysis of multiple scattering factors of turbid media for glucose measurement using near-infrared spectroscopy.

Near-infrared (NIR) diffuse reflectance spectroscopy has been widely used for non-invasive glucose measurement in humans, as glucose can induce a significant and detectable optical signal change in tissue. However, the scattering-dominated glucose spectrum in the range of 1000 to 1700nm is easily confused with many other scattering factors, such as particle density, particle size, and tissue refractive index. Our aim is to identify the subtle distinctions between glucose and these factors through theoretical analysis and experimental verification, in order to employ suitable methods for eliminating these interferences, thus increasing the accuracy of non-invasive glucose measurement. We present a theoretical analysis of the spectra of 1000 to 1700nm for glucose and some scattering factors, which is then verified by an experiment on a 3% Intralipid solution. We found that both the theoretical and experimental results show that the effective attenuation coefficient of glucose has distinct spectral characteristics, which are distinct from the spectra caused by particle density and refractive index, particularly in the range of 1400 to 1700nm. Our findings can offer a theoretical foundation for eliminating these interferences in non-invasive glucose measurement, aiding mathematical methods to model appropriately and enhance the accuracy of glucose prediction.

High-durability organic electrochromic devices based on in-situ-photocurable electrochromic materials

•Organic electrochromic materials with in situ photocuring features were proposed •The electrochromic film and device showed attractive durability and calendar life •A high-resolution electrochromic photolithographic patterning was demonstrated Electrochromic materials can undergo electrochemically driven redox processes resulting in optical signal changes, and they have shown attractive application potential in smart windows, wearable electronics, electronic papers, etc. However, their research and development (R&D) are still limited due to the lack of suitable materials and processing strategies to achieve high durability. Here, in-situ-photocurable electrochromic molecules were designed and synthesized to overcome the aforementioned challenges. Compared with the existing doping mode and polymerization mode, in-situ-photocured electrochromic films and devices showed superior durability (e.g., adhesion, multi-dimension stability, and full-contrast calendar life of >120 days) and remarkable overall performance (e.g., transparency = ∼90%, optical modulation = 72.7%, and full-contrast cycle life > 21,000). Furthermore, a high-resolution electrochromic photolithography for micro-nano patterning (recognizable pattern size: ∼2 μm, the best electrochromic resolution to date) was successfully achieved. Based on this, some potential applications in multi-level information encryption and tunable secondary colors were demonstrated. Electrochromic materials can undergo electrochemically driven redox processes resulting in optical signal changes, and they have shown attractive application potential in smart windows, wearable electronics, electronic papers, etc. However, their research and development (R&D) are still limited due to the lack of suitable materials and processing strategies to achieve high durability. Here, in-situ-photocurable electrochromic molecules were designed and synthesized to overcome the aforementioned challenges. Compared with the existing doping mode and polymerization mode, in-situ-photocured electrochromic films and devices showed superior durability (e.g., adhesion, multi-dimension stability, and full-contrast calendar life of >120 days) and remarkable overall performance (e.g., transparency = ∼90%, optical modulation = 72.7%, and full-contrast cycle life > 21,000). Furthermore, a high-resolution electrochromic photolithography for micro-nano patterning (recognizable pattern size: ∼2 μm, the best electrochromic resolution to date) was successfully achieved. Based on this, some potential applications in multi-level information encryption and tunable secondary colors were demonstrated.

Investigation of the Few‐Layer Black Phosphorus Degradation by the Photonic Measurements

AbstractFew‐layer black phosphorus (FLBP) is a 2D material that gains worldwide interest for its possible applications, mainly in electronics and optoelectronics. However, as FLBP is prone to a degradation process under environmental conditions, there is a need for a monitoring method allowing investigation of its surface quality. Among many techniques, optoelectronic ones have unique advantages of fast response, non‐contact, and non‐invasive operation. In this paper, a photonic method is presented for this purpose with a focus on the earliest stages of the degradation process. Measurements are performed using a fiber‐optic interferometer working at the wavelength of 1310 nm. Series of material characterization measurements, including scanning electron microscopy, X‐ray photoelectron spectroscopy, and Raman spectroscopy investigations are performed to examine the FLBP using a well‐established methodology. Two samples—with liquid exfoliated FLBP and with layers of supernatant—prepared in two different production processes are investigated over 3 h. A detailed presentation of the degradation process is provided. The results prove that the surface monitoring of FLBP is possible by registering optical signal changes correlated with the changes in optical parameters caused by the proceeding degradation process.

Properties of REM sleep alterations with epilepsy.

It is usually assumed that individuals rest during sleep. However, coordinated neural activity that presumably requires high energy consumption is increased during REM sleep. Here, using freely moving male transgenic mice, the local brain environment and astrocyte activity during REM sleep were examined using the fibre photometry method with an optical fibre inserted deep into the lateral hypothalamus, a region that is linked with controlling sleep and metabolic state of the entire brain. Optical fluctuations of endogenous autofluorescence of the brain parenchyma or fluorescence of sensors for Ca2+ or pH expressed in astrocytes were examined. Using a newly devised method for analysis, changes in cytosolic Ca2+ and pH in astrocytes and changes in the local brain blood volume (BBV) were extracted. On REM sleep, astrocytic Ca2+ decreases, pH decreases (acidification) and BBV increases. Acidification was unexpected, as an increase in BBV would result in efficient carbon dioxide and/or lactate removal, which leads to alkalinization of the local brain environment. Acidification could be a result of increased glutamate transporter activity due to enhanced neuronal activity and/or aerobic metabolism in astrocytes. Notably, optical signal changes preceded the onset of the electrophysiological property signature of REM sleep by ∼20-30 s. This suggests that changes in the local brain environment have strong control over the state of neuronal cell activity. With repeated stimulation of the hippocampus, seizure response gradually develops through kindling. After a fully kindled state was obtained with multiple days of stimuli, the optical properties of REM sleep at the lateral hypothalamus were examined again. Although a negative deflection of the detected optical signal was observed during REM sleep after kindling, the estimated component changed. The decrease in Ca2+ and increase in BBV were minimal, and a large decrease in pH (acidification) emerged. This acidic shift may trigger an additional gliotransmitter release from astrocytes, which could lead to a state of hyperexcitable brain. As the properties of REM sleep change with the development of epilepsy, REM sleep analysis may serve as a biomarker of epileptogenesis severity. REM sleep analysis may also predict whether a specific REM sleep episode triggers post-sleep seizures.

A Principal Approach to the Detection of Radiation-Induced DNA Damage by Circular Dichroism Spectroscopy and Its Dosimetric Application

Using cholesteric liquid-crystalline dispersion (CLCD) of DNA, we demonstrate that the molecularly organized systems may be used both for qualitative assessment of the degree of radiation-induced DNA damage, as well as for detection of radiation doses in a very wide range. The doses up to 500 Gy do not cause any significant changes in optical signals of DNA in solution. However, when irradiated molecules are used to prepare the CLCD by addition of crowding polymer, a clear correlation of its optical signals with an absorbed dose is observed. For example, at a dose of 500 Gy, a maximum drop in the circular dichroism (CD) signal for DNA solution and for CLCD formed from preliminary irradiated molecules is ≈20% and ≈700%, respectively. This approach can also be used to expand the dosimetric capabilities of DNA CLCD. Compared to the case of irradiation of ready-made DNA CLCD, formation of the dispersed system from irradiated DNA allows to increase its sensitivity by more than 2 orders of magnitude. A similar decrease in the CD signal (≈1.45-fold) is observed in these systems at the doses of 100 kGy and 200 Gy, respectively. This principal approach seems to be relevant for other biomolecules and molecularly organized systems.

Water-soluble dual lysosome/mitochondria-targeted fluorescent probe for detection of SO2 in water, food, herb, and live cells

In this paper, we present a new donor-π bridge-acceptor type fluorescent probe, MIB, which bears two organelle-targeted groups, namely positively charged benzothiazole group for mitochondria and morpholine moiety for lysosomes. In aqueous solution, the nucleophilic addition of HSO3- (as SO2 donor) to MIB blocked its long-range π-conjugation and ICT process and resulted in significant optical signal changes (blue-shifted UV absorbance and fluorescence), which enabled colorimetric and ratiometric fluorescent detection of HSO3- with high selectivity and sensitivity (detection limit of 63.15 nM). MIB offers obvious advantages of good water-solubility, fast response time (within 1 min), unique dual lysosome/mitochondria targeting capability and has been applied to the sensing of endogenous and exogenous SO2 in live cells through fluorescent imaging. In addition, the proposed probe has been utilized for the determination of bisulfite in real water, food and herbal medicine samples, showing good recovery (91.45 % − 109.3 %) and precision.

Response Mechanism of Hyperpolarization-Based Polyion Nanosensors.

The last decade has witnessed a rapid development of nano- and microparticle-based optical ion sensors, including ion-selective optodes (ISOs). While the application of nano-ISOs has shown promising performance for sensing inorganic ions, polyion sensing using nanoscale ISOs has encountered significant interference in complex samples such as blood plasma. Recently, we have reported on a new polyion sensing principle that operates through a novel mechanism to overcome this challenge. The new sensing mechanism showed improved characteristics not observed with conventional ion-exchange type sensors, but the precise mechanism of operation remained thus far unclear. This paper aims to clarify how protamine, the arginine-rich target polycation, behaves during optical signal transduction to give dramatically improved selectivity. Based on thermodynamic data, sensor performance and ζ-potential analysis, two discrete phases of protamine extraction are identified. Initially, protamine extracts into the bulk nanosensor phase, a process that is concurrent with the optical signal change. This is then followed by protamine accumulation onto the nanosensor surface, which starts only upon saturation of the optical signal change. The data indicate that the improved selectivity is due to the inability of small ions to form a sufficiently strong interaction with an active sensing ingredient, DNNS-. Any exchange of one inorganic cation for another therefore remains optically silent, suppressing matrix effects. Moreover, the recognition of protamine is shown to be an exhaustive extraction process, making the response independent of the nature and concentration of the initial small cation in the nanosensor phase.

Stabilizing liquid crystal droplets with hydrogel films and its application in monitoring adenosine triphosphate

Liquid crystal droplets have shown unique response performance due to their exclusive optical properties and dispersion. However, the stability of LC droplets during storage and application needs to be improved. Here, we report a novel LC droplet sensing platform to improve the stability of LC droplets significantly. By embedding LC droplets into polyacrylamide hydrogel films, the LC droplets can be preserved for four months without noticeable volume loss and any aggregation even in the absence of surfactant. Interestingly, LC droplets exhibit remarkable stability even in ethanol and N,N-Dimethylformamide aqueous solution. Besides, the mechanical properties of hydrogel film do not reduce after embedding LC droplets. Specifically, the introduction of LC droplets improves the elasticity of the hydrogel film. As a sensing platform, the response performance of the LC droplet-embedded hydrogel film is investigated. After being exposed to ATP solution as low as 1 ng/mL, LC droplets can generate optical signal changes which can be observed by the naked eye. The strategy presented here provides a new sight for the design of LC droplet sensors and contributes to the practical application of LC droplet sensors.

Magnetic Field-Modulated Plasmonic Scattering of Hybrid Nanorods for FFT-Weighted OCT Imaging in NIR-II.

We report a method for fast Fourier transform (FFT)-weighted optical coherence tomography (OCT) in the second biological tissue transparency window by actively modulating the plasmonic scattering of Fe3O4@Au hybrid nanorods using magnetic fields. Instead of tracking the nanoparticles' lateral displacement in conventional magnetomotive OCT imaging, we monitor the nanorod rotation and optical signal changes under an alternating magnetic field in real time. The coherent rotation of the nanorods with the field produces periodic OCT signals, and the FFT is then used to convert the periodic OCT signals in the time domain to a single peak in the frequency domain. This allows automatic screening of nanorod signals from the random biological noises and reconstruction of FFT-weighted images using a computer program based on a time-sequence image set. Compared with conventional magnetomotive OCT, the FFT-weighted imaging technique creates enhanced OCT images with dB-scale contrast over an order of magnitude higher than the original images.

Porphyrin COF and its mechanical pressing-prepared carbon fiber hybrid membrane for ratiometric detection, removal and enrichment of Cd2+

A nitrogen (N), oxygen (O)-rich porphyrin-based covalent organic framework (COF), in which interlayer porphyrin molecules are vertically stacked, is prepared and characterized. As-prepared N,O-rich TpTph COF shows a high adsorption capacity for Cd2+ due to the abundant coordination sites. More interesting, it is found that the formation of COF enlarges the porphyrin ring center space, thus facilitating the Cd2+coordination, and the resulting optical signal changes make the ratiometric detection of Cd2+ possible. Furthermore, using carbon fiber (CF) filaments, which are obtained from low cost and easy-to-obtain actived carbon mask, as support, porphyrin COF-based CF@TpTph membrane is prepared through in-situ growth of COF on the support followed by simple mechanical pressing. The CF@TpTph membrane is demonstrated to work well for both Cd2+ removal and enrichment from soil and water samples, and shows the advantages of ease of handling, robust stability, reduced secondary pollution risk to samples, and good reusability. This work provides a powerful tool for Cd2+ removal and enrichment, exhibits that preparing porphyrin-based COFs is a feasible way to promote the interactions between porphyrin ring and Cd2+, and demonstrates that mechanical pressing is a promising strategy for the design of COF-based monolithic materials to promote the practical applications of COFs.

D-π-A Dual-Mode Probe Design for the Detection of nM-Level Typical Oxidants.

Although a set of functional molecules with the D-π-A structure has been explored as optical probes for the detection of target analytes, it remains a great challenge to elaborately design a single probe for distinguishing different analytes by their intrinsic oxidation or reduction capabilities and thus to generate distinct optical responses. Here, a unique TCF-based probe (DMA-CN) containing two unsaturated double bonds in the π-conjugation bridge and TCF with different reaction activities that could be cut off by KMnO4 and NaClO in varying degrees was developed, causing remarkably distinguishable responses for both fluorescence and colorimetric channels to discriminate KMnO4 and NaClO from each other. The fluorescence and colorimetric limits of detection (LODs) of the proposed DMA-CN toward KMnO4 were calculated as 60 and 91 nM, respectively, while those for NaClO were 13.3 and 214 nM, and all the optical signal change can be observed within 1 s with good specificity. Based on the proposed probe design strategy, a well-fabricated test strip was proven to be promising for the rapid, in-field detection and risk management. We expect that the present probe design methodology would provide a powerful strategy for efficient probe exploration, especially for discriminating the substances with similar oxidizing properties.

Real-time liquid crystal-based creatinine sensor using a micro-patterned flexible substrate

ABSTRACT We propose a novel, simple, cost-effective sensor based on orientational transitions of nematic liquid crystals (LC) for real-time, quantitative, and sensitive detection of creatinine. A micro-well array structure on a polydimethylsiloxane (PDMS) substrate was fabricated to replace traditional copper grids stabilising a thin LC film, which contains 4-cyano-4ʹ-pentylbiphenyl (5CB) LC material and 4ʹ-hexylbiphenyl-4-carboxylic acid (HBA). The principle of the sensor is based on the ordering transition of LCs induced by enzymatic reactions of creatinine and creatinine deaminase (CD), resulting in an optical signal change. The orientational response of LCs was quantitatively monitored in the presence of different amounts of creatinine by cross-polarised optical microscopy and light transmittance measurement system in real time. Concentrations from 50 to 1100 μM of creatinine were successfully detected.

Optical recording of brain functions based on voltage-sensitive dyes

To better understand the spatial distribution of brain functions, we need to monitor and analyze neuronal activities. Electrophysiological technique has provided an important method for the exploration of some neural circuits. However, this method cannot simultaneously detect the activities of nerve cell groups. Therefore, methods that can monitor the spatial distribution of neuronal population activity are demanded to explore brain functions. Voltage-sensitive dyes (VSDs) shift their absorption or emission optical signals in response to different membrane potentials, allowing assessing the global electrical state of neurons. Optical recording technique coupled with VSDs is a promising method to monitor the brain functions by detecting optical signal changes. This review focuses on the fast and slow responses of VSDs to membrane potential changes and optical recordings utilized in the central nervous system. In this review, we attempt to show how VSDs and optical recordings can be used to obtain brain functional monitoring at high spatial and temporal resolution. Understanding of brain functions will not only greatly improve the cognition of information transmission of complex neural network, but also provide new methods of treating brain diseases such as Parkinson’s and Alzheimer’s diseases.

BitLight

This paper presents BitLight, a novel paradigm that uses the rapid flashing of a digital light processing (DLP) projector to encode an imperceptible mask temporally that, when sensed by a photodiode, uniquely specifies where the photodiode is located on the projected image. BitLight is inspired by the psychophysical phenomenon that the human visual system (HVS) cannot resolve rapid temporal changes in optical signals, so redundant optical signals could be inserted for tracking with some or little compromise on the original human perceived visual content. BitLight is the first to devise a bit-level temporal encoding to display RGB colors while also embedding tracking signals in a digital fashion. Compared to traditional visible-light-communication (VLC) systems that use frame-level encoding techniques such as luminance changes [10, 25, 26, 32] and alpha channel [16], the bit-level encoding of BitLight makes better use of the ultra-fine temporal division capabilities of DLP projectors to embed a much higher tracking data throughput and thus achieve faster localization speed. With our current prototype hardwares of a low-end microcontroller, cheap photodiodes, and a commercial off-the-shelfDLP projector, evaluation results have demonstrated an average of only 9.5ms to localize the sensor, versus 200ms by a comparison testbed that uses simple frame-level encodings.

Plasmonic Metasensors Based on 2D Hybrid Atomically Thin Perovskite Nanomaterials.

In this work, we have designed highly sensitive plasmonic metasensors based on atomically thin perovskite nanomaterials with a detection limit up to 10−10 refractive index units (RIU) for the target sample solutions. More importantly, we have improved phase singularity detection with the Goos–Hänchen (GH) effect. The GH shift is known to be closely related to optical phase signal changes; it is much more sensitive and sharp than the phase signal in the plasmonic condition, while the experimental measurement setup is much more compact than that of the commonly used interferometer scheme to exact the phase signals. Here, we have demonstrated that plasmonic sensitivity can reach a record-high value of 1.2862 × 109 µm/RIU with the optimum configurations for the plasmonic metasensors. The phase singularity-induced GH shift is more than three orders of magnitude larger than those achievable in other metamaterial schemes, including Ag/TiO2 hyperbolic multilayer metamaterials (HMMs), metal–insulator–metal (MIM) multilayer waveguides with plasmon-induced transparency (PIT), and metasurface devices with a large phase gradient. GH sensitivity has been improved by more than 106 times with the atomically thin perovskite metasurfaces (1.2862 × 109 µm/RIU) than those without (918.9167 µm/RIU). The atomically thin perovskite nanomaterials with high absorption rates enable precise tuning of the depth of the plasmonic resonance dip. As such, one can optimize the structure to reach near zero-reflection at the resonance angle and the associated sharp phase singularity, which leads to a strongly enhanced GH lateral shift at the sensor interface. By integrating the 2D perovskite nanolayer into a metasurface structure, a strong localized electric field enhancement can be realized and GH sensitivity was further improved to 1.5458 × 109 µm/RIU. We believe that this enhanced electric field together with the significantly improved GH shift would enable single molecular or even submolecular detection for hard-to-identify chemical and biological markers, including single nucleotide mismatch in the DNA sequence, toxic heavy metal ions, and tumor necrosis factor-α (TNFα).

Neurovascular coupling during deep brain stimulation

BackgroundDeep brain stimulation (DBS) is an effective treatment for movement disorders, yet its mechanisms of action remain unclear. One method used to study its circuit-wide neuromodulatory effects is functional magnetic resonance imaging (fMRI) which measures hemodynamics as a proxy of neural activity. To interpret functional imaging data, we must understand the relationship between neural and vascular responses, which has never been studied with the high frequencies used for DBS. ObjectiveTo measure neurovascular coupling in the rat motor cortex during thalamic DBS. MethodSimultaneous intrinsic optical imaging and extracellular electrophysiology was performed in the motor cortex of urethane-anesthetized rats during thalamic DBS at 7 different frequencies. We related Maximum Change in Reflectance (MCR) from the imaging data to Integrated Evoked Potential (IEP) and change in broadband power of multi-unit (MU) activity, computing Spearman’s correlation to determine the strength of these relationships. To determine the source of these effects, we studied the contributions of antidromic versus orthodromic activation in motor cortex perfusion using synaptic blockers. ResultsMCR, IEP and change in MU power increased linearly to 60 Hz and saturated at higher frequencies of stimulation. Blocking orthodromic transmission only reduced the DBS-induced change in optical signal by ∼25%, suggesting that activation of corticofugal fibers have a major contribution in thalamic-induced cortical activation. ConclusionDBS-evoked vascular response is related to both evoked field potentials as well as multi-unit activity.

Effects of mTOR inhibitors on neuropathic pain revealed by optical imaging of the insular cortex in rats

In the pain matrix, the insular cortex (IC) is mainly involved in discriminative sensory and motivative emotion. Abnormal signal transmission from injury site causes neuropathic pain, which generates enhanced synaptic plasticity. The mammalian target of rapamycin (mTOR) complex is the key regulator of protein synthesis; it is involved in the modulation of synaptic plasticity. To date, there has been no report on the changes in optical signals in the IC under neuropathic condition after treatment with mTOR inhibitors, such as Torin1 and XL388. Therefore, we aimed to determine the pain-relieving effect of mTOR inhibitors (Torin1 and XL388) and observe the changes in optical signals in the IC after treatment. Mechanical threshold was measured in adult male Sprague-Dawley rats after neuropathic surgery, and therapeutic effect of inhibitors was assessed on post-operative day 7 following the microinjection of Torin1 or XL388 into the IC. Optical signals were acquired to observe the neuronal activity of the IC in response to peripheral stimulation before and after treatment with mTOR inhibitors. Consequently, the inhibitors showed the most effective alleviation 4 h after microinjection into the IC. In optical imaging, peak amplitudes of optical signals and areas of activated regions were reduced after treatment with Torin1 and XL388. However, there were no significant optical signal changes in the IC before and after vehicle application. These findings suggested that Torin1 and XL388 are associated with the alleviation of neuronal activity that is excessively manifested in the IC, and is assumed to diminish synaptic plasticity.