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The spinal cord (SC) is crucial for a myriad of somatosensory, autonomic signal processing, and transductions. Understanding the SC vascular structure and function thus plays an integral part in neuroscience and clinical research. However, the dense layers of myelinated ascending axons on the dorsal side inconveniently grant the SC tissue with high optical scattering property, which significantly hinders the imaging depth of the SC vasculature in vivo. Commonly used antiscattering techniques such as multiphoton fluorescence microscopy have low imaging speed and cannot capture the rapid vascular particle flow without significant motion blur. Here, advantage of the high penetration of near‐infrared (NIR)‐II fluorescence is taken to demonstrate a deep SC vascular structural image stack up to 350 µm, comparable to two‐photon microscopy. Furthermore, the red blood cells are labelled with the clinically approved NIR dye indocyanine. The combination of a fast NIR camera and indocyanine green‐red blood cells (RBCs) makes it possible to attain high‐speed 100 frame‐per‐second NIR‐II imaging to identify the corresponding changes in RBC velocity during the external hind leg stimulus. For the first time, it is established that the NIR‐II region would be a promising spectral window for SC imaging. NIR‐II fluorescence microscopy has excellent potential for clinical and basic science research on SC. [ABSTRACT FROM AUTHOR]

Due to the great demand of throughput and reliability for multimedia applications in Fifth Generation (5G) networks, many broadcasting systems adopt the Millimeter Wave (mmWave) technology to address the lack of the spectrum resources. As one of 5G-PPP projects, Internet of Radio Light (IoRL) project adopts 40GHz mmWave band to support a high-speed and stable Ultra-High-Definition (UHD) television broadcasting service in the indoor environment. Because of the high frequency property, mmWave bands usually suffers from the high path loss and the penetration loss. Thus, in order to overcome these issues, directional antennas are employed to provide additional power gain while increasing transmission distance. However, the mmWave with directional antennas brings additional problems, such as limited transmission angle and more multipath effects. Therefore, in this paper, for better understanding of impact factors on the signal quality and transmission coverage of the directional 40GHz mmWave band in the indoor environment, a measurement campaign is introduced in detail and the channel characteristics are measured and analysed in varying cases. The mainly concerned characteristics are path loss, shadow fading, average Power Delay Profile (PDP), Root-Mean-Square (RMS) delay spread, arrival rate and coherence bandwidth. All Measured characteristic values are summarised in three tables at the end of this paper. Besides of these, as a reference of channel analysis and a metric of signal quality and effective coverage, Error Vector Magnitude (EVM) of received signal in each case is measured and discussed. Moreover, a simulation is performed based on a statistical channel model to validate the measured results. [ABSTRACT FROM AUTHOR]

Rodents are popular biological models for physiological and behavioral research in neuroscience and rats are better models than mice due to their higher genome similarity to human and more accessible surgical procedures. However, rat brain is larger than mice brain and it needs powerful imaging tools to implement better penetration against the scattering of the thicker brain tissue. Three-photon fluorescence microscopy (3PFM) combined with near-infrared (NIR) excitation has great potentials for brain circuits imaging because of its abilities of anti-scattering, deep-tissue imaging, and high signal-to-noise ratio (SNR). In this work, a type of AIE luminogen with red fluorescence was synthesized and encapsulated with Pluronic F-127 to make up form nanoparticles (NPs). Bright DCDPP-2TPA NPs were employed for in vivo three-photon fluorescent laser scanning microscopy of blood vessels in rats brain under 1550 nm femtosecond laser excitation. A fine three-dimensional (3D) reconstruction up to the deepness of 600 μ m was achieved and the blood flow velocity of a selected vessel was measured in vivo as well. Our 3PFM deep brain imaging method simultaneously recorded the morphology and function of the brain blood vessels in vivo in the rat model. Using this angiography combined with the arsenal of rodent's brain disease, models can accelerate the neuroscience research and clinical diagnosis of brain disease in the future. [ABSTRACT FROM AUTHOR]

Multiphoton microscopy has been a powerful tool in brain research, three-photon fluorescence microscopy is increasingly becoming an emerging technique for neurological research of the cortex in depth. Nonhuman primates play important roles in the study of brain science because of their neural and vascular similarity to humans. However, there are few research results of three-photon fluorescence microscopy on the brain of nonhuman primates due to the lack of optimized imaging systems and excellent fluorescent probes. Here we introduced a bright aggregation-induced emission (AIE) probe with excellent three-photon fluorescence efficiency as well as facile synthesis process and we validated its biocompatibility in the macaque monkey. We achieved a large-depth vascular imaging of approximately 1 mm in the cerebral cortex of macaque monkey with our lab-modified three-photon fluorescence microscopy system and the AIE probe. Functional measurement of blood velocity in deep cortex capillaries was also performed. Furthermore, the comparison of cortical deep vascular structure parameters across species was presented on the monkey and mouse cortex. This work is the first in vivo three-photon fluorescence microscopic imaging research on the macaque monkey cortex reaching the imaging depth of ∼1 mm with the bright AIE probe. The results demonstrate the potential of three-photon microscopy as primate-compatible method for imaging fine vascular networks and will advance our understanding of vascular function in normal and disease in humans. [ABSTRACT FROM AUTHOR]

An introduction to an article published within the issue about the imaging of deep spinal cord using near-infrared fluorescent microscopy is presented.

Multiphoton microscopy and nanoparticle-assisted photodynamic therapy are two important areas in biophotonics research. In this paper, we combined these two technologies together. Photosensitizer (HPPH) doped colloidal mesoporous silica nanoparticles were synthesized and systematically characterized. Based on a confocal microscope equipped with a 1560 nm femtosecond laser, we showed: (1) direct three-photon luminescence from HPPH doped nanoparticles, which were uptaken by tumor cells, and (2) cytotoxicity towards tumor cells by HPPH under three-photon excitation. Nanoparticle-assisted three-photon photodynamic therapy can be a promising technology for disease diagnosis and in vivo/clinical therapy. [ABSTRACT FROM AUTHOR]

Fluorescence imaging in the second near-infrared window (NIR-II, 900–1880 nm) with less scattering background in biological tissues has been combined with the confocal microscopic system for achieving deep in vivo imaging with high spatial resolution. However, the traditional NIR-II fluorescence confocal microscope with separate excitation focus and detection pinhole makes it possess low confocal efficiency, as well as difficultly to adjust. Two types of upgraded NIR-II fluorescence confocal microscopes, sharing the same pinhole by excitation and emission focus, leading to higher confocal efficiency, are built in this work. One type is fiber-pinhole-based confocal microscope applicable to CW laser excitation. It is constructed for fluorescence intensity imaging with large depth, high stabilization and low cost, which could replace multiphoton fluorescence microscopy in some applications (e.g., cerebrovascular and hepatocellular imaging). The other type is air-pinhole-based confocal microscope applicable to femtosecond (fs) laser excitation. It can be employed not only for NIR-II fluorescence intensity imaging, but also for multi-channel fluorescence lifetime imaging to recognize different structures with similar fluorescence spectrum. Moreover, it can be facilely combined with multiphoton fluorescence microscopy. A single fs pulsed laser is utilized to achieve up-conversion (visible multiphoton fluorescence) and down-conversion (NIR-II one-photon fluorescence) excitation simultaneously, extending imaging spectral channels, and thus facilitates multi-structure and multi-functional observation. [ABSTRACT FROM AUTHOR]

The significance of performing large‐depth dynamic microscopic imaging in vivo for life science research cannot be overstated. However, the optical throughput of the microscope limits the available information per unit of time, i.e., it is difficult to obtain both high spatial and temporal resolution at once. Here, a method is proposed to construct a kind of intravital microscopy with high optical throughput, by making near‐infrared‐II (NIR‐II, 900–1880 nm) wide‐field fluorescence microscopy learn from two‐photon fluorescence microscopy based on a scale‐recurrent network. Using this upgraded NIR‐II fluorescence microscope, vessels in the opaque brain of a rodent are reconstructed three‐dimensionally. Five‐fold axial and thirteen‐fold lateral resolution improvements are achieved without sacrificing temporal resolution and light utilization. Also, tiny cerebral vessel dilatations in early acute respiratory failure mice are observed, with this high optical throughput NIR‐II microscope at an imaging speed of 30 fps. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Significantly reduced tissue scattering of fluorescence signals in the second near-infrared (NIR-II, 1,000–1,700 nm) spectral region offers opportunities for large-depth in vivo bioimaging. Nowadays, most reported works concerning NIR-II fluorescence in vivo bioimaging are realized by wide-field illumination and 2D-arrayed detection (e.g., via InGaAs camera), which has high temporal resolution but limited spatial resolution due to out-of-focus signals. Combining NIR-II fluorescence imaging with confocal microscopy is a good approach to achieve high-spatial resolution visualization of biosamples even at deep tissues. In this presented work, a NIR-II fluorescence confocal microscopic system was setup. By using a kind of aggregation-induced emission (AIE) dots as NIR-II fluorescent probes, 800 μm-deep 3D in vivo cerebrovascular imaging of a mouse was obtained, and the spatial resolution at 700 μm depth could reach 8.78 μm. Moreover, the time-correlated single photon counting (TCSPC) technique and femtosecond laser excitation were introduced into NIR-II fluorescence confocal microscopy, and in vivo confocal NIR-II fluorescence lifetime microscopic imaging (FLIM) of mouse cerebral vasculature was successfully realized. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) participate in many physiological processes, the abnormality of which will cause chronic diseases and pathologies such as diabetes and obesity. It is crucial to monitor the distribution of LDs at high spatial resolution and large depth. Herein, we carried three-photon imaging of LDs in fat liver. Owing to the large three-photon absorption cross-section of the luminogen named NAP-CF3 (1. 6 7 × 1 0 − 7 9 cm6 s2), three-photon fluorescence fat liver imaging reached the largest depth of 80 μ m. Fat liver diagnosis was successfully carried out with excellent performance, providing great potential for LDs-associated pathologies research. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) fluorescence imaging is an important imaging technology in deep-tissue biomedical imaging and related researches, due to the low absorption and scattering of NIR excitation and/or emission in biological tissues. Laser scanning confocal microscopy (LSCM) plays a significant role in the family of fluorescence microscopy. Due to the introduction of pinhole, it can provide images with optical sectioning, high signal-to-noise ratio and better spatial resolution. In this study, in order to combine the advantages of these two techniques, we set up a fluorescence microscopic imaging system, which can be named as NIR-LSCM. The system was based on a commercially available confocal microscope, utilizing a NIR laser for excitation and a NIR sensitive detector for signal collection. In addition, NIR fluorescent nanoparticles (NPs) were prepared, and utilized for fluorescence imaging of the ear and brain of living mice based on the NIR-LSCM system. The structure of blood vessels at certain depth could be visualized clearly, because of the high-resolution and large-depth imaging capability of NIR-LSCM. [ABSTRACT FROM AUTHOR]

Nanoparticle-assisted near-infrared (NIR) bioimaging and two-photon fluorescence microscopy (TPFM) are two important technologies in biophotonic research. In this work, we synthesize the dye named 2-(4-bromophenyl)-3-(4-(4-(diphenylamino)styryl)phenyl)fumaronitrile (TPABDFN), which had a large two-photon absorption cross-section and bright NIR emission. The dyes were then encapsulated with poly(styrene- co -maleic anhydride) (PSMA), forming fluorescent nanoparticles. The TPABDFN-PSMA nanoparticles possessed high chemical and optical stability, good biocompatibility, as well as large two-photon absorption cross-section (5.56 × 10 5 GM). Furthermore, we combined NIR bioimaging and TPFM together, and utilized TPABDFN-PSMA nanoparticles as fluorescent contrast agents for two-photon excited NIR microscopic imaging, with a 1040 nm-femtosecond laser. In vivo angiography of mice ear and brain was performed. Due to the deep penetration capability of both 1040 nm-excitation and NIR emission light, a very large in vivo microscopic imaging depth (∼1.2 mm) was achieved. NIR emissive and biocompatible TPABDFN-PSMA nanoparticles have great potential in disease diagnosis and clinical therapies, where deep-tissue imaging is required. [ABSTRACT FROM AUTHOR]

The cerebrovasculature plays an essential role in neurovascular and homeostatic functions in health and disease conditions. Many efforts have been made for developing vascular thrombosis methods to study vascular dysfunction in vivo, while technical challenges remain, such as accuracy and depth‐selectivity to target a single vessel in the cerebral cortex. Herein, this paper first demonstrates the evaluation and quantification of the feasibility and effects of Rose Bengal (RB)‐induced photothrombosis with 720–1070 nm ultrafast lasers in a raster scan. A flexible and reproducible approach is then proposed to employ a 1070 nm ultrafast laser with a spiral scan for producing RB‐induced occlusion, which is described as precision ultrafast laser‐induced photothrombosis (PLP). Combine with two‐photon microscopy imaging, this PLP displays highly precise and fast occlusion induction of various vessel types, sizes, and depths, which enhances the precision and power of the photothrombosis protocol. Overall, the PLP method provides a real‐time, practical, precise, and depth‐selected single‐vessel photothrombosis technology in the cerebral cortex with commercially available optical equipment, which is crucial for exploring brain vascular function with high spatial‐temporal resolution in the brain. [ABSTRACT FROM AUTHOR]

This paper presents the technical performance results of a measurement campaign from a 5G indoor millimeter Wave (mmWave) and Visible Light Communications (VLC) multi component carrier system, which was developed in a Horizon 2020 research project called Internet of Radio-Light (IoRL). The measurement campaign was performed in the famous Integer House laboratory at the Innovation Park in Building Research Establishment in Watford, U.K., which represents a typical European home environment. It includes four field test results: 1) VLC received signal quality measured as Error Vector Magnitude (EVM) against coverage, 2) mmWave received signal quality measured as EVM against coverage, 3) VLC location accuracy against a prescribed grid using received signal strength, 4) Comparison of measured and simulated Electromagnetic Field (EMF) strength against coverage. This measurement campaign not only tests the system concept in a realistic indoor home environment but also provides analysis of the results with practical recommendations on further technical enhancements required to improve the system performance and insights into viable commercial solutions and applications. Other environments in which this technology could be deployed were envisaged as: underground train platforms and tunnels, museums and supermarkets. [ABSTRACT FROM AUTHOR]

The traditional design strategies for highly bright solid‐state luminescent materials rely on weakening the intermolecular π–π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid‐state fluorescence. TBP‐e‐TPA with a molecular rotor in the end position of a planar core adopts a long‐range cofacial packing mode, which in the solid state is almost non‐emissive. By shifting molecular rotors to the bay position, the resultant TBP‐b‐TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid‐state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP‐b‐TPA nanoparticles were used for two‐photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid‐state fluorophores. [ABSTRACT FROM AUTHOR]

Many features of 5G are definitely important to the broadcasting service, including diverse content services such as follow-me TV, video-on-demand, but also gaming, Virtual reality (VR) and Augmented reality (AR) and many others. Meanwhile, those services depend more and more on the user’s position accuracy, especially in indoor environment. With the increase of broadcasting data traffic indoors, to obtain a highly accurate position is becoming a challenge because of the impact of radio interference. In order to support a high-quality indoor broadcasting service, a high-accuracy positioning, radiation-free, and high-capacity communication system is urgently needed. In this paper, a 5G indoor positioning system is proposed for museums. It utilizes unlicensed visible light of the electromagnetic spectrum to provide museum visitors with high-accuracy positioning, multiple forms of interaction services, and high-resolution multimedia delivery on a mobile device. The geographic data and the location-related data integrated into the 5G New Radio (NR) waveform are detailed. A general-purpose system architecture is provided and some basic techniques to enhance system performance are also investigated. A preliminary demonstration is built in the laboratory environment. It supports over 45.25 Mbps data rate and a mean positioning error of 0.18 m. [ABSTRACT FROM AUTHOR]

In this study, a portable confocal hyperspectral microscope is developed. In traditional confocal laser scanning microscopes, scan lens and tube lens are utilized to achieve a conjugate relationship between the galvanometer and the back focal plane of the objective, in order to achieve a better resolution. However, these lenses make it difficult to scale down the volume of the system. In our portable confocal hyperspectral microscope (PCHM), the objective is placed directly next to the galvomirror. Thus, scan lens and tube lens are not included in our system and the size of this system is greatly reduced. Furthermore, the resolution is also acceptable in many biomedical and food-safety applications. Through reducing the optical length of the system, the signal detection efficiency is enhanced. This is conducive to realizing both the fluorescence and Raman hyperspectral imaging. With a multimode fiber as a pinhole, an improved image contrast is also achieved. Fluorescent spectral images for HeLa cells/fingers and Raman spectral images of kumquat pericarp are present. The spectral resolution and spatial resolutions are about 0.4 nm and 2.19 µm, respectively. These results demonstrate that this portable hyperspectral microscope can be used in in-vivo fluorescence imaging and in situ Raman spectral imaging. [ABSTRACT FROM AUTHOR]

In this work, a series of new diketopyrrolopyrrole-based dyes have been synthesized by connecting tetraphenylethene to the diketopyrrolopyrrole core. All the four compounds exhibit good aggregation-induced emission property with nonemissive in the solution but strong red fluorescence in the aggregate or solid state. Also, these new dyes exhibit large two-photon absorption cross sections (σ), in which the σ data measured by the open aperture Z-scan technique are determined to be 150, 300, 1140 and 1016 GM for four dyes, respectively. In addition, compound with stilbene and four tetraphenylethene units ( DPP-TPE-3) was used as the luminogen and encapsulated into nanoparticles for cell imaging and two-photon excited fluorescence blood vessels imaging. The result indicates that it can be used as the effective fluorescence probe for bioimaging and has great potential for bioapplications. [ABSTRACT FROM AUTHOR]

Though commonly used, metal electrodes are incompatible with brain tissues, often leading to injury and failure to achieve long-term implantation. Here we report a subdural neural interface of hydrogel functioning as an ionic conductor, and elastomer as a dielectric. We demonstrate that it incurs a far less glial reaction and less cerebrovascular destruction than a metal electrode. Using a cat model, the hydrogel electrode was able to record electrical signals comparably in quality to a metal electrode. The hydrogel-elastomer neural interface also readily facilitated multimodal functions. Both the hydrogel and elastomer are transparent, enabling in vivo optical microscopy. For imaging, cerebral vessels and calcium signals were imaged using two-photon microscopy. The new electrode is compatible with magnetic resonance imaging and does not cause artifact images. Such a new multimodal neural interface could represent immediate opportunity for use in broad areas of application in neuroscience research and clinical neurology. [ABSTRACT FROM AUTHOR]