Structural and functional imaging of brains

Abstract

Analyzing the complex structures and functions of brain is the key issue to understanding the physiological and pathological processes. Although neuronal morphology and local distribution of neurons/blood vessels in the brain have been known, the subcellular structures of cells remain challenging, especially in the live brain. In addition, the complicated brain functions involve numerous functional molecules, but the concentrations, distributions and interactions of these molecules in the brain are still poorly understood. In this review, frontier techniques available for multiscale structure imaging from organelles to the whole brain are first overviewed, including magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), serial-section electron microscopy (ssEM), light microscopy (LM) and synchrotron-based X-ray microscopy (XRM). Specially, XRM for three-dimensional (3D) imaging of large-scale brain tissue with high resolution and fast imaging speed is highlighted. Additionally, the development of elegant methods for acquisition of brain functions from electrical/chemical signals in the brain is outlined. In particular, the new electrophysiology technologies for neural recordings at the single-neuron level and in the brain are also summarized. We also focus on the construction of electrochemical probes based on dual-recognition strategy and surface/interface chemistry for determination of chemical species in the brain with high selectivity and long-term stability, as well as electrochemophysiological microarray for simultaneously recording of electrochemical and electrophysiological signals in the brain. Moreover, the recent development of brain MRI probes with high contrast-to-noise ratio (CNR) and sensitivity based on hyperpolarized techniques and multi-nuclear chemistry is introduced. Furthermore, multiple optical probes and instruments, especially the optophysiological Raman probes and fiber Raman photometry, for imaging and biosensing in live brain are emphasized. Finally, a brief perspective on existing challenges and further research development is provided.

Aggregation-Induced Emission (AIE), Life and Health

“…In vivo imaging techniques allow scientists to study and understand the dynamic and complex biological processes such as tumor growth, gene expression, and drug delivery in living animal models, with real-time, in situ and noninvasive characteristics. , In addition, the applied experimental objects are closer to the actual condition, which can better simulate the physiological and pathological processes of the organism. Significant advancements have been made in in vivo imaging to overcome its current limitations by NIR, multiphoton and PAI equipment, which have expanded its applications and increased its potential for clinical translation. − Considering the successful demonstration of several rising examples for in vitro and ex vivo visualization, AIE probes are anticipated to offer good imaging performance in live animals.…”

Self‐assembly at Liquid‐Liquid Interface: A New SERS Substrate for Analytical Sensing†

“…[ 90‐92 ] High similarity in chemical structure among neurotransmitters, for example, epinephrine (EP), norepinephrine (NE), and dopamine (DA), makes the great interferences for selective detection. [ 93‐95 ] In addition, the amount of neurotransmitters is generally trace in central nervous system, resulting in the high demand for sensitive detection. To realize sensitive and selective detection of EP in a complex system, AuNPs were modified with α,β‐nitriloacetic acid and Fe(NO 3 ) 3 to form the AuNP‐(Fe‐NTA) sensor (Figure 6B).…”

Implantable Electrochemical Sensors for Brain Research

“…Chemical signals such as ions, neurotransmitters, and reactive oxygen species (ROS) in the living brain are closely related to the physiological and pathological processes in living systems. Therefore, the development of in vivo brain sensors that can accurately and stably quantify chemical signals help humans understand the working mechanism of the brain. − Although optical methods such as fluorescent contrast agents for visible and infrared light have been developed extensively for brain imaging, , they are still limited by the depth of tissue penetration and tissue autofluorescence. In recent years, advances in materials science and instrumentation facilitated the development of implantable electrochemical microelectrode technology, which allowed scientists to monitor chemical signals in the brain with high spatial and temporal resolution. − Unfortunately, the current in vivo electrochemical sensors still face several challenges due to the complexity of the brain environment.…”