同步辐射X射线成像技术在脑成像研究中的应用

脑疾病的诊疗、 探索高级脑功能机制和理解意识本源对脑科学研究具有重要意义. 成像技术在阐明脑科学神经系统结构和功能中发挥了重要作用. 迄今, 核磁共振成像、 光学成像和电子显微镜成像技术已为脑科学研究提供了强有力的手段, 取得了突出的进展. 同步辐射X射线显微成像技术具有高分辨率、 快成像速度和高穿透深度等优点, 是一类与已有技术互补的新型脑成像技术. 本文介绍了核磁共振波谱、 光学显微镜和电子显微镜等成像方法在脑成像领域中的应用, 重点阐述了同步辐射X射线成像的优势以及在脑结构成像和功能成像中的应用. 在此基础上, 展望了同步辐射X射线成像应用于脑科学研究的未来发展方向, 讨论了该技术在绘制人脑联接图谱中的优势及可行性.     

Molecular Targeting of Epidermal Growth Factor Receptor (EGFR) and Vascular Endothelial Growth Factor Receptor (VEGFR)

Epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR) are two extensively studied membrane-bound receptor tyrosine kinase proteins that are frequently overexpressed in many cancers. As a result, these receptor families constitute attractive targets for imaging and therapeutic applications in the detection and treatment of cancer. This review explores the dynamic structure and structure-function relationships of these two growth factor receptors and their significance as it relates to theranostics of cancer, followed by some of the common inhibition modalities frequently employed to target EGFR and VEGFR, such as tyrosine kinase inhibitors (TKIs), antibodies, nanobodies, and peptides. A summary of the recent advances in molecular imaging techniques, including positron emission tomography (PET), single-photon emission computerized tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI), and optical imaging (OI), and in particular, near-IR fluorescence imaging using tetrapyrrolic-based fluorophores, concludes this review.     

Single-molecule monitoring in living cells by use of fluorescence microscopy

Monitoring single molecules in living cells is becoming a powerful tool for study of the location, dynamics, and kinetics of individual biomolecules in real time. In recent decades, several optical imaging techniques, for example epi-fluorescence microscopy, total internal reflection fluorescence microscopy (TIRFM), confocal microscopy, quasi-TIRFM, and single-point edge excitation subdiffraction microscopy (SPEED), have been developed, and their capability of capturing single-molecule dynamics in living cells has been demonstrated. In this review, we briefly summarize recent advances in the use of these imaging techniques for monitoring single-molecules in living cells for a better understanding of important biological processes, and discuss future developments.     

Reversible Chemical Reactions for Single‐Color Multiplexing Microscopy

Recent developments in biology demand an increasing number of simultaneously imaged structures with standard fluorescence microscopy. However, the number of multiplexed channels is limited for most multiplexing modalities, such as spectral multiplexing or fluorescence‐lifetime imaging. We propose extending the number of imaging channels by using chemical reactions, controlling the emissive state of fluorescent dyes. As proof of concept, we reversibly switch a fluorescent copper sensor to enable successive imaging of two different structures in the same spectral channel. We also show that this chemical multiplexing is orthogonal to existing methods. By using two different dyes, we combine chemical with spectral multiplexing for the simultaneous imaging of four different structures with only two spectrally different channels. We characterize and discuss the approach and provide perspectives for extending imaging modalities in stimulated emission depletion microscopy, for which spectral multiplexing is technically demanding.     

Introduction to Infrared and Raman-Based Biomedical Molecular Imaging and Comparison with Other Modalities

Molecular imaging has rapidly developed to answer the need of image contrast in medical diagnostic imaging to go beyond morphological information to include functional differences in imaged tissues at the cellular and molecular levels. Vibrational (infrared (IR) and Raman) imaging has rapidly emerged among the molecular imaging modalities available, due to its label-free combination of high spatial resolution with chemical specificity. This article presents the physical basis of vibrational spectroscopy and imaging, followed by illustration of their preclinical in vitro applications in body fluids and cells, ex vivo tissues and in vivo small animals and ending with a brief discussion of their clinical translation. After comparing the advantages and disadvantages of IR/Raman imaging with the other main modalities, such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography/single-photon emission-computed tomography (PET/SPECT), ultrasound (US) and photoacoustic imaging (PAI), the design of multimodal probes combining vibrational imaging with other modalities is discussed, illustrated by some preclinical proof-of-concept examples.     

Apoptosis imaging by radionuclide probes

Apoptosis has attracted more and more research interests due to the critical role it played in the human health. Also, it is often confused with other types of cell death. Thus, methods that enable sensitive detection and noninvasive visualized imaging of apoptosis will be of enormous benefit in the development of new diagnostics, therapies and patient management. During the past decades, with the development of apoptosis understanding and molecular imaging modalities, a large collection of imaging agents based on well-defined molecular markers and/or physiological features have been developed and tested in preclinical and clinical studies. In this review, we mainly discuss radionuclide imaging probes, ranging from simple attachments of reporter moieties to proteins and peptides, to rationally designed probes that allow multimodal imaging. Furthermore, we briefly outline the current status of clinical translation and attempt to give an outlook on the further study.     

Listen to the chemical and histological information in biological tissue

Photoacoustic imaging (PAI), as an emerging biomedicine diagnostic technique that has been developed quickly in the past decade, inherits the high spatial resolution of ultrasonography in imaging deep tissue and the high sensitivity of optical imaging in evaluating tissue chemical and physiological information. In this paper, after introducing the basic principles of PAI including both photoacoustic tomography and photoacoustic microscopy, we will review some recent progress of PAI in biomedicine and demonstrate the capability of PAI in detecting the chemical compositions and in evaluating the histological microstructures in biological tissue.     

Sensitive and selective tumor imaging with novel and highly activatable fluorescence probes.

Selective and sensitive tumor imaging in vivo is one of the most requested methodologies in medical sciences. Although several imaging modalities have been developed including positron emission tomography (PET) and magnetic resonance (MR) imaging for the detection of tumors, none of these modalities can activate the signals upon being accumulated or uptaken to tumor sites. Among these modalities, only optical fluorescence imaging has a marked advantage, that is, their signals can be dramatically increased upon detecting some biological features. In this short review, I will introduce some recent strategies for activatable optical fluorescence imaging of tumors, and discuss their advantages over other modalities.     

Infrared and Raman imaging of biological and biomimetic samples

Established methods for imaging of biological or biomimetic samples, such as fluorescence and optical microscopy, magnetic resonance imaging (MRI), X-ray tomography or positron emission tomography (PET) are currently complemented by infrared (both near-IR and mid-IR) as well as Raman spectroscopic imaging, whether it be on a microscopic or macroscopic scale. These vibrational spectroscopic techniques provide a wealth of information without a priori knowledge of either the spectral data or the composition of the sample. Infrared radiation does not harm the organism, no electric potential needs to be applied, and the measurements are not influenced by electromagnetic fields. In addition, no extrinsic labeling or staining, which may perturb the system under investigation, has to be added. The immense volume of information contained in spectroscopic images requires multivariate analysis methodologies in order to effectively mine the chemical and spatial information contained within the data as well as to analyze a time-series of images in order to reveal the origin of a chemical or biochemical process. The promise and limitations of this new analytical tool are surveyed in this review.     

Bioimaging Based on Nucleic Acid Nanostructures

Nucleic acid nanostructures with structural programmability, spatial addressability and excellent biocompatibility have drawn much attention in various biomedical applications, such as bioimaging, biosensing and drug delivery. In this review, we summarize the recent research progress in the field of bioimaging based on nucleic acid nanostructures with different imaging models, including fluorescent imaging(FI), magnetic resonance imaging(MRI), photoacoustic imaging(PAI) and positron emission tomography/computed tomography(PET/CT) imaging. We also discuss the remaining challenges and further opportunities involved in the bioimaging research based on nucleic acid nanostructures.     

原位冷冻电子断层扫描的发展及在生物研究方面的应用

对生物大分子复合物的研究和结构分析对于全面了解其功能和生物学意义至关重要.冷冻电子显微镜在提供生物大分子结构及大分子分布等方面起到重要的作用.近年来,冷冻电子显微镜的硬件和软件的发展进一步提高了冷冻电子显微镜的有效性,使其对各种生物结构、蛋白质结构的解析更加准确快捷.但是,对于生物系统来说,蛋白质和大分子复合物等均处于复杂的生理环境中,因此原位检测生物分子的三维结构对于生物体系和结构生物学具有重要意义.冷冻电子断层扫描作为一种功能强大的技术,可以无需标记直接通过冷冻样品的固有衬度识别生物大分子的结构,并且可在原位生理环境中对生物分子进行纳米级分辨率的三维成像.本文综述了与冷冻电子断层扫描相关的样品制备和数据处理技术,并总结了冷冻电子断层扫描技术在分离的大分子复合物和整个细胞或组织中的生物学应用.     

Functional tumor imaging based on inorganic nanomaterials

Inorganic nanomaterials have attracted substantial research interest due to their unique intrinsic physicochemical properties.We highlighted recent advances in the applications of inorganic nanoparticles regarding their imaging efficacy, focusing on tumor-imaging nanomaterials such as metal-based and carbon-based nanomaterials and quantum dots. Inorganic nanoparticles gain excellent in vivo tumor-imaging functions based on their specific characteristics of strong near-infrared optical absorption and/or X-ray attenuation capability. The specific response signals from these novel nanomaterials can be captured using a series of imaging techniques, i.e., optical coherence tomography(OCT), X-ray computed tomography(CT) imaging, two-photon luminescence(TPL), photoacoustic tomography(PAT), magnetic resonance imaging(MRI), surface-enhanced Raman scattering(SERS) and positron emission tomography(PET). In this review, we summarized the rapid development of inorganic nanomaterial applications using these analysis techniques and discussed the related safety issues of these materials.     

Challenges in Applying Photoemission Electron Microscopy to Biological Systems†

Photoemission electron microscopy (PEEM) is a unique surface‐sensitive instrument capable of providing real‐time images with high spatial resolution. While similar to the more common electron microscopies, scanning electron microscopy and transmission electron microscopy, the imaging technology relies on the photogeneration of electrons emitted from a sample through light excitation. This imaging technique has found prominence in surface and materials sciences, being well suited for imaging flat surfaces, and changes that occur to that surface as various parameters are changed (e.g. temperature, exposure to reactive gases). Biologically focused PEEM received significant attention in the 1970s, but was not aggressively advanced since that pioneering work. PEEM is capable of providing important insights into biological systems that extend beyond simple imaging. In this article, we identify and establish important issues that affect the acquisition and analysis of biological samples with PEEM. We will briefly review the biological impact and importance of PEEM with respect to our work. The article also concludes with a discussion of some of the current challenges that must be addressed to enable PEEM to achieve its maximum potential with biological samples.     

Emerging applications of near-infrared fluorescent metal nanoclusters for biological imaging

Recent advances in the development of near-infrared fluorescent metal nanoclusters for bioimaging applications have been thoroughly overviewed.     

Physical and chemical analysis of elemental sulfur formation during galena surface oxidation

The surface oxidation of sulfide minerals, such as galena (PbS), in aqueous solutions is of critical importance in a number of applications. A comprehensive understanding of the formation of oxidation species at the galena surface is still lacking. Much controversy over the nature of these oxidation products exists. A number of oxidation pathways have been proposed, and experimental evidence for the formation of elemental sulfur, metal polysulfides, and metal-deficient lead sulfides in acidic conditions has been shown and argued. This paper provides further insight into the electrochemical behavior of galena at pH 4.5. Utilizing a novel experimental system that combines in situ electrochemical control and AC mode atomic force microscopy (AFM) surface imaging, the formation and growth of nanoscopic domains on the galena surface are detected and examined at anodic potentials. AFM phase images indicate that these domains have different material properties to the underlying galena. Continued oxidation results in nanoscopic pitting and the formation of microscopic surface domains, which are confirmed to be elemental sulfur by Raman spectroscopy. Further clarification of the presence of elemental sulfur is provided by Cryo-XPS. Polysulfide and metal-deficient sulfide could not be detected within this system.     

Recent advances in electron tomography: TEM and HAADF-STEM tomography for materials science and semiconductor applications.

Electron tomography is a well-established technique for three-dimensional structure determination of (almost) amorphous specimens in life sciences applications. With the recent advances in nanotechnology and the semiconductor industry, there is also an increasing need for high-resolution three-dimensional (3D) structural information in physical sciences. In this article, we evaluate the capabilities and limitations of transmission electron microscopy (TEM) and high-angle-annular-dark-field scanning transmission electron microscopy (HAADF-STEM) tomography for the 3D structural characterization of partially crystalline to highly crystalline materials. Our analysis of catalysts, a hydrogen storage material, and different semiconductor devices shows that features with a diameter as small as 1-2 nm can be resolved in three dimensions by electron tomography. For partially crystalline materials with small single crystalline domains, bright-field TEM tomography provides reliable 3D structural information. HAADF-STEM tomography is more versatile and can also be used for high-resolution 3D imaging of highly crystalline materials such as semiconductor devices.     

Coherent anti-Stokes Raman scattering microscopy for polymers

Coherent anti-stokes Raman scattering (CARS) microscopy is a label-free chemical imaging modality capable of interrogating local molecular composition, concentration, and even orientation. In comparison to traditional Raman spectroscopy/imaging, CARS generates signals that are typically orders-of-magnitude stronger, enabling high-throughput and large-area imaging with superior spectroscopic fidelity. In this review, we present an overview of CARS microscopy as applied to polymer science, covering such timely and important topics as drug release and reaction kinetics to 3D molecular structures and orientation. We also discuss outstanding opportunities and challenges to using CARS microscopy as a quantitative measurement method.     

Towards highly efficient,intelligent and bimodal imaging probes: Novel approaches provided by lanthanide coordination chemistry

Gd³⁺ complexes are widely used as contrast enhancing agents in medical magnetic resonance imaging (MRI). In recent years, new fields have emerged in their development. The general tendency of using higher magnetic fields in biomedical and clinical MRI for a better signal to noise ratio calls for new contrast agents specifically optimized for such high field applications. Molecular imaging, aiming at the non-invasive visualisation of expression and function of bioactive molecules, requires imaging probes that provide a specific magnetic response to a particular molecular event. Finally, bimodal imaging may allow for combining the excellent resolution of MRI with a good sensitivity of other imaging modalities, such as optical methods. It requires bimodal imaging probes that satisfy requirements for both modalities within a single molecule. Here we review our latest efforts to develop novel lanthanide-based contrast agents in these specific fields and demonstrate the possibilities offered by lanthanide coordination chemistry.     

Multimodality Imaging Agents with PET as the Fundamental Pillar

Positron emission tomography (PET) provides quantitative information in vivo with ultra‐high sensitivity but is limited by its relatively low spatial resolution. Therefore, PET has been combined with other imaging modalities, and commercial systems such as PET/computed tomography (CT) and PET/magnetic resonance (MR) have become available. Inspired by the emerging field of nanomedicine, many PET‐based multimodality nanoparticle imaging agents have been developed in recent years. This Minireview highlights recent progress in the design of PET‐based multimodality imaging nanoprobes with an aim to overview the major advances and key challenges in this field and substantially improve our knowledge of this fertile research area.     

Gold Nanorods as Contrast Agents for Biological Imaging: Optical Properties,Surface Conjugation and Photothermal Effects†

Gold nanorods (NRs) have plasmon‐resonant absorption and scattering in the near‐infrared (NIR) region, making them attractive probes for in vitro and in vivo imaging. In the cellular environment, NRs can provide scattering contrast for darkfield microscopy, or emit a strong two‐photon luminescence due to plasmon‐enhanced two‐photon absorption. NRs have also been employed in biomedical imaging modalities such as optical coherence tomography or photoacoustic tomography. Careful control over surface chemistry enhances the capacity of NRs as biological imaging agents by enabling cell‐specific targeting, and by increasing their dispersion stability and circulation lifetimes. NRs can also efficiently convert optical energy into heat, and inflict localized damage to tumor cells. Laser‐induced heating of NRs can disrupt cell membrane integrity and homeostasis, resulting in Ca²⁺ influx and the depolymerization of the intracellular actin network. The combination of plasmon‐resonant optical properties, intense local photothermal effects and robust surface chemistry render gold NRs as promising theragnostic agents.