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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.

Defining and visualizing the three-dimensional (3D) structures of pharmaceuticals provides a new and important tool to elucidate the phenomenal behavior and underlying mechanisms of drug delivery systems. The mechanism of drug release from complex structured dosage forms, such as bilayer osmotic pump tablets, has not been investigated widely for most solid 3D structures. In this study, bilayer osmotic pump tablets undergoing dissolution, as well as after dissolution in a desiccated solid state were examined, and visualized by synchrotron radiation micro-computed tomography (SR-μCT). In situ formed 3D structures at different in vitro drug release states were characterized comprehensively. A distinct movement pattern of NaCl crystals from the push layer to the drug layer was observed, beneath the semi-permeable coating in the desiccated tablet sample. The 3D structures at different dissolution time revealed that the pushing upsurge in the bilayer osmotic pump tablet was directed via peripheral “roadways”. Typically, different regions of the osmotic front, infiltration region, and dormant region were classified in the push layer during the dissolution of drug from tablet samples. According to the observed 3D microstructures, a “subterranean river model” for the drug release mechanism has been defined to explain the drug release mechanism.

Changes in structure of oral solid dosage forms (OSDF) elementally determine the drug release and its therapeutic effects. In this research, synchrotron radiation X-ray micro-computed tomography was utilized to visualize the 3D structure of enteric coated pellets recovered from the gastrointestinal tract of rats. The structures of pellets in solid state and in vitro compendium media were measured. Pellets in vivo underwent morphological and structural changes which differed significantly from those in vitro compendium media. Thus, optimizations of the dissolution media were performed to mimic the appropriate in vivo conditions by introducing pepsin and glass microspheres in media. The sphericity, pellet volume, pore volume and porosity of the in vivo esomeprazole magnesium pellets in stomach for 2 h were recorded 0.47, 1.55 × 108 μm3, 0.44 × 108 μm3 and 27.6%, respectively. After adding pepsin and glass microspheres, the above parameters in vitro reached to 0.44, 1.64 × 108 μm3, 0.38 × 108 μm3 and 23.0%, respectively. Omeprazole magnesium pellets behaved similarly. The structural features of pellets between in vitro media and in vivo condition were bridged successfully in terms of 3D structures to ensure better design, characterization and quality control of advanced OSDF., Graphical abstract The differences in dynamic structure of enteric pellets during dissolution in vitro and in vivo were first observed. By introducing pepsin and glass microspheres into pharmacopoeia medium, the structures of pellets were bridged.Image 1

Currently, Radio Frequency Identification (RFID) is one of the key technologies to realize the Internet of Things (IoT), which is widely used in our daily life. However, there are some security threats such as impersonation attack, replay attack in existed RFID systems. In addition, most physical-layer authentication methods for RFID systems are mainly to authenticate tags without authenticating the user. In this paper, we present the design and implementation of Au-Hota, a system that can authenticate the tag and the user simultaneously, and can resist replaying attack and impersonation attack that cannot be solved by most physical-layer methods. Our idea is to assign a unique identifier to the user based on the inductive coupling between two adjacent tags. When the user draws the identity identifier on the tag, different identity identifiers correspond to unique phase features so that simultaneous authentication of the tag and the user can be achieved under the premise of ensuring security. The system is fully compatible with Ultra High Frequency (UHF) RFID systems without any modification. We implement a prototype of the system and conduct extensive experiments to evaluate performance. Our results demonstrate that the system has good authentication performance.

Characterizing interactions between microbial cells and their specific inhibitory drugs is essential for developing effective drugs and understanding the therapeutic mechanism. Functional metal nanoclusters can be effective inhibitory agents against microorganisms according to various characterization methods, but quantitative three-dimensional (3D) spatial structural analysis of intact cells is lacking. Herein, using coherent X-ray diffraction imaging, we performed in situ 3D visualization of unstained

Effective methods for visualizing neurovascular morphology are essential for understanding the normal spinal cord and the morphological alterations associated with diseases. However, ideal techniques for simultaneously imaging neurovascular structure in a broad region of a specimen are still lacking. In this study, we combined Golgi staining with angiography and synchrotron radiation micro-computed tomography (SRμCT) to visualize the 3D neurovascular network in the mouse spinal cord. Using our method, the 3D neurons, nerve fibers, and vasculature in a broad region could be visualized in the same image at cellular resolution without destructive sectioning. Besides, we found that the 3D morphology of neurons, nerve fiber tracts, and vasculature visualized by SRμCT were highly consistent with that visualized using the histological method. Moreover, the 3D neurovascular structure could be quantitatively evaluated by the combined methodology. The method shown here will be useful in fundamental neuroscience studies. Supplementary Information The online version contains supplementary material available at 10.1007/s12264-021-00715-7.

Exploring the three-dimensional (3D) morphology of neurons is essential to understanding spinal cord function and associated diseases comprehensively. However, 3D imaging of the neuronal network in the broad region of the spinal cord at cellular resolution remains a challenge in the field of neuroscience. In this study, to obtain high-resolution 3D imaging of a detailed neuronal network in the mass of the spinal cord, the combination of synchrotron radiation micro-computed tomography (SRμCT) and the Golgi-cox staining were used. We optimized the Golgi-Cox method (GCM) and developed a modified GCM (M-GCM), which improved background staining, reduced the number of artefacts, and diminished the impact of incomplete vasculature compared to the current GCM. Moreover, we achieved high-resolution 3D imaging of the detailed neuronal network in the spinal cord through the combination of SRμCT and M-GCM. Our results showed that the M-GCM increased the contrast between the neuronal structure and its surrounding extracellular matrix. Compared to the GCM, the M-GCM also diminished the impact of the artefacts and incomplete vasculature on the 3D image. Additionally, the 3D neuronal architecture was successfully quantified using a combination of SRμCT and M-GCM. The SRμCT was shown to be a valuable non-destructive tool for 3D visualization of the neuronal network in the broad 3D region of the spinal cord. Such a combinatorial method will, therefore, transform the presentation of Golgi staining from 2 to 3D, providing significant improvements in the 3D rendering of the neuronal network. Supplementary Information The online version contains supplementary material available at 10.1007/s00418-020-01949-8.

Defining and visualizing the three-dimensional (3D) structures of pharmaceuticals provides a new and important tool to elucidate the phenomenal behavior and underlying mechanisms of drug delivery systems. The mechanism of drug release from complex structured dosage forms, such as bilayer osmotic pump tablets, has not been investigated widely for most solid 3D structures. In this study, bilayer osmotic pump tablets undergoing dissolution, as well as after dissolution in a desiccated solid state were examined, and visualized by synchrotron radiation micro-computed tomography (SR-μCT).

Characterizing the three-dimensional (3D) morphological alterations of microvessels under both normal and seizure conditions is crucial for a better understanding of epilepsy. However, conventional imaging techniques cannot detect microvessels on micron/sub-micron scales without angiography. In this study, synchrotron radiation (SR)-based X-ray in-line phase-contrast imaging (ILPCI) and quantitative 3D characterization were used to acquire high-resolution, high-contrast images of rat brain tissue under both normal and seizure conditions. The number of blood microvessels was markedly increased on days 1 and 14, but decreased on day 60 after seizures. The surface area, diameter distribution, mean tortuosity, and number of bifurcations and network segments also showed similar trends. These pathological changes were confirmed by histological tests. Thus, SR-based ILPCI provides systematic and detailed views of cerebrovascular anatomy at the micron level without using contrast-enhancing agents. This holds considerable promise for better diagnosis and understanding of the pathogenesis and development of epilepsy.

Accumulating evidence indicates the critical importance of cerebrovascular dysfunction in the pathogenesis of Alzheimer's disease (AD). However, systematic comparative studies on the precise brain vasculature of wild-type and AD model mice are still rare. Using an image-optimization method for analysing Micro-Optical Sectioning Tomography (MOST) data, we generated cross-scale whole-brain 3D atlases that cover the entire vascular system from large vessels down to smallest capillaries at submicron resolution, for both wild-type mice and a transgenic (APP/PS1) mouse model of AD. In addition to distinct vascular patterns in different brain regions, we found that the main vessels of the molecular layer of the hippocampal dentate gyrus (DG-ml) undergo abrupt changes in both diameter and branch angle, spreading a unique comb-like pattern of capillaries. By using a quantitative analysis workflow, we identified in the hippocampus of AD mice an overall reduction of the mean vascular diameter, volume fraction and branch angle, with most significant impairment in the DG-ml. In addition, virtual endoscopy revealed irregular morphological features in the vessel lumen of the AD mice, potentially contributing to the impairment of blood flow. Our results demonstrate the capability of high-resolution cross-scale evaluation of brain vasculature and underscore the importance of studying hippocampal microcirculation for understanding AD pathogenesis.

Macrophage phenotype conversion is crucial for improving post-traumatic angiogenesis and tissue repair. Biomaterials with the ability of skewing macrophage phenotype have attracted widespread attention in the field of tissue engineering. The aim of this study was to transform macrophage phenotype by a three-step process; anodizing, drug loading and coating with polyelectrolyte multilayer (PEM) films. Interleukin (IL)-4, an anti-inflammatory cytokine, was loaded into titania nanotubes (TNTs) on the titanium surface. Subsequently, sodium alginate (ALG) and chitosan (CS) were alternately assembled onto IL-4-loaded TNTs and cross-linked with genipin/calcium chloride, finally forming cross-linked PEM films. The IL-4 release profile and cellular immune response of the modified surface was investigated. In the simulated biological solution, only 20% of IL-4 were detected in the first 3 days, with a sustained release of approximately 5 ng over 10 days. The results of gene expression and protein secretion in macrophages indicated that IL-4-loaded PEM films significantly attenuated the inflammatory activity of macrophages at the later stage through down-regulating the mRNA and protein levels of inflammatory markers. In summary, IL-4 was controlled released from the cross-linked PEM films deposited on the nanotubes, leading to the temporal conversion of macrophage phenotype.

Neurovascular injury is often observed in traumatic brain injury (TBI). However, the relationship between mechanical forces and vascular injury is still unclear. A key question is whether the complex anatomy of vasculature plays a role in increasing forces in cerebral vessels and producing damage. We developed a high-fidelity multiscale finite element model of the rat brain featuring a detailed definition of the angioarchitecture. Controlled cortical impacts were performed experimentally and in-silico. The model was able to predict the pattern of blood–brain barrier damage. We found strong correlation between the area of fibrinogen extravasation and the brain area where axial strain in vessels exceeds 0.14. Our results showed that adjacent vessels can sustain profoundly different axial stresses depending on their alignment with the principal direction of stress in parenchyma, with a better alignment leading to larger stresses in vessels. We also found a strong correlation between axial stress in vessels and the shearing component of the stress wave in parenchyma. Our multiscale computational approach explains the unrecognised role of the vascular anatomy and shear stresses in producing distinct distribution of large forces in vasculature. This new understanding can contribute to improving TBI diagnosis and prevention.

Cavities and the architectures inside tablet play a decisive role for the permeation of water within tablet to initiate disintegration phenomenon. The present study aims to establish inner structure characterization methodology based on synchrotron radiation X-ray microcomputed tomography (SR-μCT) for microcrystalline cellulose (MCC) tablets and to correlate the cavities and 'their attributes to tablet disintegration phenomenon. The three-dimensional (3D) morphological architecture and quantitative data of single particles for 12 specifications of MCC, and respective MCC tablets' cavities structure were obtained through advanced SR-μCT studies. The image processing techniques were established to study the morphology of voids and porosity in an axial and radial direction based on the highly resolved 3D structure of tablets. The in-situ visualization of morphological disintegration behavior indicates that there were two patterns of disintegrations, which can be cataloged as laminating type (LT) and splitting type (ST) disintegrations. The principal component analysis (PCA) was used for multivariate data analysis to get the meaningful correlation among disintegration behaviors, cavities morphology, single particles attributes, and the cavities spatial arrangement within the tablets. These findings have deepened insights into inner structures of tablets and single particle structural attributes to tablet disintegration, reflecting the mechanism of disintegration mode, and the significance of pharmaceutical structure evaluated via SR-μCT.

Smart microstructure design of dosage forms such as microcapsules that protect the microorganism, can improve probiotics survival from gastric pH challenges and prolong their shelf life. In this study, synchrotron radiation X-ray microcomputed tomography (SR-μCT) was applied to quantitatively reveal the material distributions and functional structures of bifidobacterium and lactobacillus microcapsules. The shell layer, middle protective layer, and the microorganisms as particles in the center layer were extracted and visualized. All the microorganisms were encapsulated by the shell completely, which prevents them from being destroyed by external environments. However, the non-uniform thickness of the shell and typical defects in the microcapsules were observed. The quantitative analysis and characterization of internal microstructures provide evidence of the need for further improvement in formulations and processing technologies for the structured system to deliver living microorganisms.

Inflammatory response occurring between tissues and implants after implantation has attracted increasing attention because it can cause local tissue necrosis and even implant failure. Macrophages play a key role in all stages of inflammation. Pro-inflammatory (M1) and anti-inflammatory (M2) macrophages comprise two main phenotypes and the switch from M1 to M2 at specific time points is important for wound healing and tissue regeneration. Therefore, we hypothesized that biomaterial systems capable of facilitating macrophage phenotype switching should attenuate inflammation and enhance healing. To this end, a system of double hydrogel layers on titania nanotubes (TNT) was prepared as reservoir to modulate the release of interleukin-4 (IL-4) and interferon-γ (IFN-γ). In this system, IL-4, an anti-inflammatory cytokine, was loaded in TNT and IFN-γ, a pro-inflammatory cytokine, was located between two hydrogel layers of chitosan/β-glycerophosphate disodium and carboxymethyl chitosan/genipin. IFN-γ released rapidly in 3 days, whereas IL-4 exhibited a sustained release profile. In culture with mesenchymal stem cells and macrophages, this system displayed good cytocompatibility and significantly promoted cell proliferation. Macrophage phenotype switch was determined by ELISA, FACS and PCR. The results manifested that IFN-γ released from the system stimulated switching of macrophages to M1 in 3 days, whereas sustained release of IL-4 polarized macrophages to M2 after 4 days. This system can modulate macrophage phenotype switching from M1 to M2 by sequential action of the two cytokines, and might be used to research immune response between tissues and implants. The present study also provided a novel strategy for designing functional biomaterials.

Many published literature sources have described the histopathological characteristics of post-traumatic syringomyelia (PTS). However, three-dimensional (3D) visualization studies of PTS have been limited due to the lack of reliable 3D imaging techniques. In this study, the imaging efficiency of propagation-based synchrotron radiation microtomography (PB-SRµCT) was determined to detect the 3D morphology of the cavity and surrounding microvasculature network in a rat model of PTS. The rat model of PTS was established using the infinite horizon impactor to produce spinal cord injury (SCI), followed by a subarachnoid injection of kaolin to produce arachnoiditis. PB-SRµCT imaging and histological examination, as well as fluorescence staining, were conducted on the animals at the tenth week after SCI. The 3D morphology of the cystic cavity was vividly visualized using PB-SRµCT imaging. The quantitative parameters analyzed by PB-SRµCT, including the lesion and spared spinal cord tissue area, the minimum and maximum diameters in the cystic cavity, and cavity volume, were largely consistent with the results of the histological assessment. Moreover, the 3D morphology of the cavity and surrounding angioarchitecture could be simultaneously detected on the PB-SRµCT images. This study demonstrated that high-resolution PB-SRµCT could be used for the 3D visualization of trauma-induced spinal cord cavities and provides valuable quantitative data for cavity characterization. PB-SRµCT could be used as a reliable imaging technique and offers a novel platform for tracking cavity formation and morphological changes in an experimental animal model of PTS.

Microcrystalline cellulose (MCC) is one of the most important excipients due to its outstanding binding and tableting properties. Owing to the absence of high resolution characterization techniques at the single particle scale, 3D (three dimension) microstructure of MCC and its effects on formulation performance remain unexamined. The aim of this work was to establish a methodology for single particles of MCC type 102 based on synchrotron radiation X-ray micro computed tomography (SR-μCT), principal component analysis (PCA) and partial least square discriminant analysis (PLSDA). Scanning electron microscopy, SR-μCT, powders properties together with tensile strength (TS), disintegration time (DT), Kawakita plots and force/displacement profiles of tablets were measured. PCA-PLSDA was applied to evaluate the structural classification of MCC particles on the basis of 2D and 3D SR-μCT derived images. The studied MCCs were found to differ in the TS, DT, Kawakita plot and force/displacement, while box ratio and Feret ratio had major influence on the principal components, but the angle of repose, bulk and tapped density did not exhibit significantly. These findings verified that different samples of MCCs from alternative suppliers have morphological diversity when assessed at the individual particle level, which could result into variation in powder properties and tableting performance.

Graphical Abstract Unlabelled image, This study investigated the formulation mechanism of microspheres via internal surfactant distribution. Eudragit L100 based microspheres loaded with bovine serum albumin were prepared by solid in oil in oil emulsion solvent evaporation method using acetone and liquid paraffin system containing sucrose stearate as a surfactant. The fabricated microspheres were evaluated for encapsulation efficiency, particle size, production yield, and in vitro release characteristics. The internal structures of microspheres were characterized using synchrotron radiation X-ray microcomputed tomography (SR-µCT). The enhanced contrast made the sucrose stearate distinguished from Eudragit to have its three dimensional (3D) distribution. Results indicated that the content and concentration determined the state of sucrose stearate and had significant influences on the release kinetics of protein. The dispersity of sucrose stearate was the primary factor that controlled the structure of the microspheres and further affected the encapsulation efficiency, effective drug loading, as well as in vitro release behavior. In conclusion, the 3D internal distribution of surfactant in microspheres and its effects on protein release behaviors have been revealed for the first time. The highly resolved 3D architecture provides new evidence for the deep understanding of the microsphere formation mechanism.

The multiple-unit sustained-release (MUSR) dosage forms containing numerous sustained-release subunits present a reliable choice for oral formulation of controlled release systems. As a typical MUSR, the metoprolol succinate sustained-release tablet is an advanced system with limited researches devoted to relating its structure to the drug release phase other than the preparation process and modulation to the release behaviors. This research details a three-dimension method to image the internal structure and detail drug release features of commercial metoprolol succinate sustained-release tablets and component individual single pellets. As such, a new perspective for MUSR dosage form is provided. Using high energy synchrotron radiation X-ray microcomputed tomography (SR-μCT), the in-situ structure parameters were obtained nondestructively. It was demonstrated that the average number of spherical pellets in a tablet was 853 ± 12 (n = 3). The average volume of the pellets was 0.09 ± 0.01 mm3, the diameter was 0.55 ± 0.03 mm, and the sphericity was 0.87 ± 0.06. These data reflected the numerical features of pellets in MUSR tablets, which were helpful for reverse engineering to MUSR. Based on the three dimensional model generated by image processing and analysis software, the pellet structures were divided into three layers of typical depot sustained release system: pellet core, drug-containing layer and outer film. The dynamic structural features determined refer to the changes of structures in pellets during in vitro drug release, with evidence that the coating layer on the pellets maintained a spherical morphology whilst numerous valleys appeared on the surface. The material constitution and distribution in coating layer were evaluated by synchrotron radiation-based Fourier transform infrared mapping and results indicated a composition of hydroxypropyl methylcellulose dispersed in ethyl cellulose. Knowledge of these structural characteristics confirmed that the mechanism of sustained drug release was membrane controlled and consistent with the drug release profiles. In conclusion, the structural investigation provided knowledge of the intrinsic quality of metoprolol succinate sustained-release tablets and offers guidance for reverse engineering of MUSR.

The essentiality of macrophages for biomaterial-mediated osteogenesis has been increasingly recognized. However, it is still unclear what is the specific role and molecular mechanisms of macrophages and material properties in the regulation of osteogenesis. As an interdisciplinary field exploring the cross-talk between immune and skeletal systems, osteoimmunology has shifted the perspective of bone substitute materials from immunosuppressive materials to immunomodulatory materials. To fabricate an immunomodulatory Ti implant, alginate/chitosan multilayer films were fabricated on the surface of titania nanotubes (TNTs) to control the release of an anti-inflammatory cytokine interleukin (IL)-4 according to our previous work. The osteogenic effects and regulation mechanisms of the immunomodulatory Ti implants were investigated in vitro in different BMSCs culture modes. Alginate/chitosan multilayer-coated samples (with or without IL-4 loading) showed better direct osteogenic ability than TNTs by promoting biomineralization and up-regulating osteogenic gene expression (BMP1α, ALP, OPN, OCN) of BMSCs. Notably, material-induced macrophage polarization, M1 and M2, enhanced early and mid-stage osteogenesis of BMSCs via distinct pathways: M1 activated both BMP6/SMADs and Wnt10b/β-catenin pathways; while M2 activated TGF-β/SMADs pathway. Material surface properties dominated in regulating late osteogenesis probably due to the surface chemical composition (alginate, chitosan and Ca2+, etc.). Due to synergistic effects of material-induced inflammatory microenvironment and material surface properties, IL-4-loaded samples exhibited superior osteogenic capability through co-activation of three signaling pathways. The in vivo studies in rat bone defect model revealed that IL-4-loaded immunomodulatory implants successfully achieved macrophage phenotypic transition from pro-inflammatory M1 to anti-inflammatory M2 and subsequently improved new bone formation.

β-artemether (ARM) is a widely used anti-malarial drug isolated from the Chinese antimalarial plant, Artemisia annua. The solvent effects on crystal habits and dissolution of ARM were thoroughly investigated and discussed herein. The ARM was recrystallized in nine different solvents of varied polarity, namely, methanol, ethanol, isopropanol, tetrahydrofuran, dichloromethane, trichloromethane, ethyl acetate, acetone and hexane by solvent evaporation method. The obtained crystals were morphologically characterized using scanning electron microscope (SEM). The average sizes of crystals were 1.80–2.64 μm calculated from microscopic images using Image-Pro software. No significant change in chemical structure was noticed after recrystallization and the specific band at 875 cm−1 wavenumber (C–O–O–C) confirmed the presence of most sensitive functional group in the ARM chemical structure. The existence and production of two polymorphic forms, polymorph A and polymorph B, was confirmed by differential scann...

The orifice drilled in the membrane as a channel for drug delivery is the key functional part of the osmotic pumps for a controlled drug release system. Reported conventional microscopic evaluations of these orifices have been limited to measurement of two-dimensional cross-section diameters. This study was aimed at establishing a novel method to measure quantitatively the three-dimensional architectures of orifices based on synchrotron radiation X-ray microcomputed tomography (SR-μCT). Quantitative analysis of architectures extracted from captopril osmotic pumps drilled by a range of operating parameters indicated that laser power correlated with the cross section area, volume, surface area and depth of the orifices, while scanning speed of laser beam showed inverse relationships with the above structure characters. The synchrotron radiation based Fourier transform infrared microspectroscopy mapping showed that there was no apparent chemical change in the surrounding area of the orifice compared with the normal membrane region. Thus SR-μCT was successfully applied to marketed felodipine osmotic pumps for architectural evaluation of the orifices. In conclusion, the first three-dimensional structural insight of orifices in osmotic pump tablets by SR-μCT and structural reconstruction for the architectures has provided deeper insight into improving the design of advanced osmotic pumps for controlled drug release.

Many spinal cord circulatory disorders present the substantial involvement of small vessel lesions. The central sulcus arteries supply nutrition to a large part of the spinal cord, and, if not detected early, lesions in the spinal cord will cause irreversible damage to the function of this organ. Thus, early detection of these small vessel lesions could potentially facilitate the effective diagnosis and treatment of these diseases. However, the detection of such small vessels is beyond the capability of current imaging techniques. In this study, an imaging method is proposed and the potential of phase-contrast imaging (PCI)- and attenuation-contrast imaging (ACI)-based synchrotron radiation for high-resolution tomography of intramedullary arteries in mouse spinal cord is validated. The three-dimensional vessel morphology, particularly that of the central sulcus arteries (CSA), detected with these two imaging models was quantitatively analyzed and compared. It was determined that both PCI- and ACI-based synchrotron radiation can be used to visualize the physiological arrangement of the entire intramedullary artery network in the mouse spinal cord in both two dimensions and three dimensions at a high-resolution scale. Additionally, the two-dimensional and three-dimensional vessel morphometric parameter measurements obtained with PCI are similar to the ACI data. Furthermore, PCI allows efficient and direct discrimination of the same branch level of the CSA without contrast agent injection and is expected to provide reliable biological information regarding the intramedullary artery. Compared with ACI, PCI might be a novel imaging method that offers a powerful imaging platform for evaluating pathological changes in small vessels and may also allow better clarification of their role in neurovascular disorders.

The control of supramolecular systems requires a thorough understanding of their dynamics, especially on a molecular level. It is extremely difficult to determine the thermokinetic parameters of supramolecular systems, such as drug-cyclodextrin complexes with fast association/dissociation processes by experimental techniques. In this paper, molecular modeling combined with novel mathematical relationships integrating the thermodynamic/thermokinetic parameters of a series of isomeric multiconfigurations to predict the overall parameters in a range of pH values have been employed to study supramolecular dynamics at the molecular level. A suitable form of Eyring's equation was derived and a two-stage model was introduced. The new approach enabled accurate prediction of the apparent dissociation/association (k(off)/k(on)) and unbinding/binding (k-r/kr) rate constants of the ubiquitous multiconfiguration complexes of the supramolecular system. The pyronine Y (PY) was used as a model system for the validation of the presented method. Interestingly, the predicted k(off) value ((40 ± 1) × 10(5) s(-1), 298 K) of PY is largely in agreement with that previously determined by fluorescence correlation spectroscopy ((5 ± 3) × 10(5) s(-1), 298 K). Moreover, the k(off)/k(on) and k-r/kr for flurbiprofen-β-cylcodextrin and ibuprofen-β-cyclodextrin systems were also predicted and suggested that the association processes are diffusion-controlled. The methodology is considered to be especially useful in the design and selection of excipients for a supramolecular system with preferred association and dissociation rate constants and understanding their mechanisms. It is believed that this new approach could be applicable to a wide range of ligand-receptor supramolecular systems and will surely help in understanding their complex mechanism.

The structure of solid drug delivery systems has considerable influence on drug release behaviors from particles and granules and also impacts other properties relevant to release characteristics such as taste. In this study, lipid-based microspheres of acetaminophen were prepared to mask the undesirable taste of drug and therefore to identify the optimal formulation for drug release. Synchrotron radiation X-ray computed microtomography (SR-μCT) was used to investigate the fine structural architectures of microspheres non-destructively at different sampling times during drug release test, which were simultaneously determined to quantitatively correlate the structural data with drug release behaviors. The results demonstrated that the polymeric formulation component, namely, cationic polymethacrylate (Eudragit E100), was the key factor to mask the bitter taste of acetaminophen by inhibiting immediate drug release thereby reducing the interaction intensity of the bitter material with the oral cavity taste buds. The structure and morphology of the microspheres were found to be influenced by the shape and particle size of the drug, which was also an important factor for taste-masking performance. The quantitative analysis generated detailed structural information which was correlated well with drug release behaviors. Thus, SR-μCT has been proved as a powerful tool to investigate the fine microstructure of particles and provides a new approach in the design of particles for taste masking.

The unique physiochemical properties of non-spherical carriers play a significant role in their functions and offer distinct advantages as drug delivery systems, including drug loading, stability and targeting. Herein, a simple method to fabricate non-spherical Pickering emulsion droplets (NSPEDs) by cyclodextrins (CDs) mediated molecular self-assembly is reported. The non-spherical shapes controlled by the type and content of oils/CDs were evaluated by the average roundness (Rave) figures. The stability and physicochemical properties of castor oil (CO)-CDs emulsions, including creaming, viscosity and size distribution with different Rave values were characterized. The Pickering emulsion droplets with different Rave values were fabricated through mixing CDs with twelve common oils. The type of oils showed varied dependence of Rave on the content of oils/CDs. Rave increased when reducing the content of oils or raising the content of CDs. The CO-CDs emulsions with larger Rave exhibited higher creaming index, stronger viscosity, smaller size, and thus possessed better stability. The size distributions at 1 μm representing the excess oil-CD microcrystals in the continuous phase became larger with increase in Rave values, indicating that the formation of NSPEDs was mainly ascribed to the excess microcrystals in the emulsions. Finally, the formation mechanism of NSPEDs directed by CDs mediated self-assembly was validated by directly dispersing the microcrystals in water and diluting the obtained emulsions. Cryo scanning electron microscope experiments were also carried out to demonstrate the presence of microcrystals at the oil–water interface. The presented work provided an efficient approach to fabricate and control the shape of droplets in Pickering emulsions for potential new applications as a drug delivery system.

Hydrophilic matrix tablets are the most commonly used dosage forms to fabricate oral controlled-release systems. It is highly desirable to design delivery system with novel mechanism to achieve sustained drug release through a simplified preparation process. The chitosan–anionic polymers based matrix tablets is assumed to produce self-assembly in the gastrointestinal tract, then transferring into film-coated tablets from original matrix type. But its dynamic behavior during dissolution process and the on-going internal microstructural changes during drug release were still in the dark. In this study, by using synchrotron radiation X-ray micro-tomography (SR-μCT) with phase contrast imaging, the micro-structure characteristics of chitosan–λ-carrageenan (CS–λ-CG) matrix based tablets during the dissolution were successfully elucidated for the first time. The qualitative and quantitative analyses of intensity distribution distinguished a hydrated CS–λ-CG layer from a solid core. Visualization based on 3D models provided quantitative details on the micro-structural characteristics of hydration dynamics. After CS–λ-CG matrix tablets were immersed in simulated gastric fluid (SGF) pH 1.2 medium for 0.5–2.0 h, the hydrated layer transformed into a gel layer and a solid swollen layer. The erosion front, swelling front, and solvent penetration front were also defined from the distinguishable micro-structures. More importantly, once the matrix tablet was transferred from SGF to the simulated intestinal fluid (SIF) pH 6.8 medium, a new layer with the enhanced strength and compactness in comparison to common gels was formed on the surface of tablets. The temporal and spatial variation of 3D models further provided direct evidence for this cross-linking behavior, the new layer was composed of CS–λ-CG polyelectrolyte complexes (PEC) which subsequently dominated release mechanisms. In summary, the phase contrast SR-μCT technique was utilized to investigate the hydration dynamics of CS–λ-CG matrix tablets which was supposed to provide a novel drug release mechanism. Based on the structure feature obtained from the high contrast image, different hydration region was distinguished and the cross-linked film was identified and visualized directly for the first time.

There has been increasing interest in using high-resolution micro-tomography to investigate the morphology of neurovascular networks in the central nervous system, which remain difficult to characterize due to their microscopic size as well as their delicate and complex 3D structure. Synchrotron radiation X-ray imaging, which has emerged as a cutting-edge imaging technology with a high spatial resolution, provides a novel platform for the non-destructive imaging of microvasculature networks at a sub-micrometre scale. When coupled with computed tomography, this technique allows the characterization of the 3D morphology of vasculature. The current review focuses on recent progress in developing synchrotron radiation methodology and its application in probing neurovascular networks, especially the pathological changes associated with vascular abnormalities in various model systems. Furthermore, this tool represents a powerful imaging modality that improves our understanding of the complex biological interactions between vascular function and neuronal activity in both physiological and pathological states.

The shapes of particles and their distribution in tablets, controlled by pretreatment and tableting process, determine the pharmaceutical performance of excipient like lubricant. This study aims to provide deeper insights to the relationship of the morphology and spatial distribution of stearic acid (SA) with the lubrication efficiency, as well as the resulting tablet property. Unmodified SA particles as flat sheet-like particles were firstly reprocessed by emulsification in hot water to obtain the reprocessed SA particles with spherical morphology. The three-dimensional (3D) information of SA particles in tablets was detected by a quantitative and non-invasive 3D structure elucidation technique, namely, synchrotron radiation X-ray micro-computed tomography (SR-µCT). SA particles in glipizide tablets prepared by using unmodified SA (GUT), reprocessed SA (GRT), as well as reference listed drug (RLD) of glipizide tablets were analyzed by SR-µCT. The results showed that the reprocessed SA with better flowability contributed to similarity of breaking forces between that of GRT and RLD. SA particles in GRT were very similar to those in RLD with uniform morphology and particle size, while SA particles in GUT were not evenly distributed. These findings not only demonstrated the feasibility of SR-µCT as a new method in revealing the morphology and spatial distribution of excipient in drug delivery system, but also deepened insights of solid dosage form design into a new scale by powder engineering., Graphical abstract Image, graphical abstract

One unusual and challenging scientific field that has received only cursory attention to date is the three-dimensional (3D) microstructure and spatial distribution of drug(s) and formulation materials in solid dosage forms. This study aims to provide deeper insight into the relationships between the microstructure of multiple-unit pellet system (MUPS) tablets and the spatial distribution of the active pharmaceutical ingredient (API) and excipients to facilitate the design of quantitative models for drug delivery systems. Synchrotron radiation X-ray microcomputed tomography (SR-μCT) was established as a 3D structure elucidation technique, which, in conjunction with liquid chromatography coupled to mass spectrometry (LC-MS) or liquid chromatography with evaporative light-scattering detector (LC-ELSD) enables chemical analysis of tablets. On the basis of the specific interior construction of theophylline MUPS tablets, the spatial distribution of materials was acquired by quantifying microregion samples that had been validated by SR-μCT for their locations in the MUPS tablets. The 3D structure of the MUPS tablets was catalogued as three structural domains: a matrix layer (ML), a protective cushion layer (PCL), and pellets (PL). Compared with the components in the ML, components in the PL had a larger proportion of theophylline, sucrose, and diethyl phthalate and a smaller proportion of lactose and sodium lauryl sulfate, whereas glyceryl monostearate was found to account for a large portion of the PCL. Microstructural characterization-guided zonal chemical determination represents a new approach for quality assessment and the development of drug delivery systems with in-depth insight into their constituent layers on a new scale.

Sedimentation of non-homogeneous systems is the typical phenomenon indicating the physical instability as a key measure to the quality control of the preparation products. Currently, the determination methods for the sedimentation of non-homogeneous preparations are based on manual measurement or semi-quantitative observation, lacking of either automation or quantitative dynamic analysis. The purpose of this research was to realize automatic and quantitative monitoring of the sedimentation dynamics for non-homogenous systems as suspension, emulsions at laboratory level. Non-contact measurement method has been established to determine the sedimentation behaviors in a standard quartz tube for sedimentation, with internal diameter and height 23 mm and 215 mm, respectively, with controlled temperature and light intensity. As high performance camera has been equipped, the sedimentation images with high spatial and temporal resolution could be acquired, which can continuously capture sedimentation images with the resolution of 2048 × 2048 pixel at a maximum rate of 60 slides/s. All the pictures were processed to extract the luminance matrix top-down along the fixed vertical midline of each picture, which implied sedimentation characteristics of the system at the moment the picture was taken. Combining all the luminance matrixes along vertical middle lines of the pictures, a time-luminance matrix profile was obtained. Digital image processing techniques were used to eliminate interference and establish a three-dimensional surface model of the sedimentation dynamics. Then, the derivative mutation algorithm has been developed for the intelligent identification of sedimentation interface with threshold optimization so as to quantitatively analyze the sedimentation dynamics with visualization. The sedimentation curve and sedimentation dynamic equation of the non-homogeneous system were finally outputted by numerical fitting. The methodology was validated for great significance in determinations of small volume samples, parallel control multiple batches, and long period of time automatic measurement.

The present study establishes a visualization method for the measurement of the distribution and localization of protein/peptide constituents within a single poly-lactide-co-glycolide (PLGA) microsphere using synchrotron radiation–based Fourier-transform infrared spectromicroscopy (SR-FTIR). The representative infrared wavenumbers specific for protein/peptide (Exenatide) and excipient (PLGA) were identified and chemical maps at the single microsphere level were generated by measuring and plotting the intensity of these specific bands. For quantitative analysis of the distribution within microspheres, Matlab software was used to transform the map file into a 3D matrix and the matrix values specific for the drug and excipient were extracted. Comparison of the normalized SR-FTIR maps of PLGA and Exenatide indicated that PLGA was uniformly distributed, while Exenatide was relatively non-uniformly distributed in the microspheres. In conclusion, SR-FTIR is a rapid, nondestructive and sensitive detection technology to provide the distribution of chemical constituents and functional groups in microparticles and microspheres., Graphical abstract A visualization method is investigated for the measurement of the distribution and localization of protein/peptide within single microsphere by SR-FTIR. Chemical maps at the single microsphere level were generated by the intensity of specific infrared bands. The relative infrared intensity ratios and optical path normalization provided internal material distribution.

The complex pathology of chronic thoracic spinal cord compression involves vascular and neuroarchitectural repair processes that are still largely unknown. In this study, we used synchrotron radiation microtomography (SRμCT) to quantitatively characterize the 3D temporal-spatial changes in the vascular and neuronal network after chronic thoracic spinal cord compression in order to obtain further insights into the pathogenesis of this disease and to elucidate its underlying mechanisms. Direct 3D characterization of the spinal cord microvasculature and neural microstructure of the thoracic spinal cord was successfully reconstructed. The significant reduction in vasculature and degeneration of neurons in the thoracic spinal cord visualized via SRμCT after chronic compression were consistent with the changes detected by immunofluorescence staining. The 3D morphological measurements revealed significant reductions of neurovascular parameters in the thoracic spinal cord after 1 month of compression and became even worse after 6 months without relief of compression. In addition, the distinct 3D morphological twist and the decrease in branches of the central sulcal artery after chronic compression vividly displayed that these could be the potential triggers leading to blood flow reduction and neural deficits of the thoracic spinal cord. Our findings propose a novel methodology for the 3D analysis of neurovascular repair in chronic spinal cord compression, both qualitatively and quantitatively. The results indicated that compression simultaneously caused vascular dysfunction and neuronal network impairment, which should be acknowledged as concurrent events after chronic thoracic spinal cord injury. Combining neuroprotection with vasoprotection may provide promising therapeutic targets for chronic thoracic spinal cord compression.

Multi-pellet formulations are advantageous for the controlled release of drugs over single-unit dosage forms. To understand the diffusion controlled drug release mechanism, the pellet structure and drug release from a single pellet (not at dose level) were studied using synchrotron radiation X-ray computed microtomography (SR-μCT) and a sensitive LC/MS/MS method. The purpose of this article is to introduce a powerful, non-invasive and quantitative technique for studying individual pellet microstructures and to investigate the relationship between the microstructure and drug release from single pellets. The data from the single pellet dissolution measurements demonstrated that the release profile of capsules containing approximately 1,000 pellets per unit dose was the summation of the release profiles of the individual pellets. The release profiles of single tamsulosin hydrochloride (TSH) pellets formed three groups when a cluster analysis was performed, and the dissolution rate of the individual pellets correlated well with the combined effects of the drug loading, volume and surface area of the pellets (R(2) = 0.9429). In addition, the void microstructures within the pellet were critical during drug release. Therefore, SR-μCT is a powerful tool for quantitatively elucidating the three-dimensional microstructure of the individual pellets; because the microstructure controls drug release, it is an important parameter in the quality control of multi-pellet formulations.