Chemical & Biomedical Imaging最新文献

Synaptic vesicle transport by motor proteins along microtubules is a crucially active process underlying neuronal communication. It is known that microtubules are destabilized by tau-hyperphosphorylation, which causes tau proteins to detach from microtubules and form neurofibril tangles. However, how tau-phosphorylation affects the transport dynamics of motor proteins on the microtubule remains unknown. Here, we discover that the long-distance unidirectional motion of vesicle-motor protein multiplexes (VMPMs) in living cells is suppressed under tau-hyperphosphorylation, with the consequent loss of fast vesicle-transport along the microtubule. The VMPMs in hyperphosphorylated cells exhibit seemingly bidirectional random motion, with dynamic properties far different from those of VMPM motion in normal cells. We establish a parsimonious physicochemical model of VMPM’s active motion that provides a unified, quantitative explanation and predictions for our experimental results. Our analysis reveals that, under hyperphosphorylation conditions, motor protein multiplexes have both static and dynamic motility fluctuations. The loss of fast vesicle-transport along the microtubule can be a mechanism of neurodegenerative disorders associated with tau-hyperphosphorylation.

Gram-negative bacteria produce outer membrane vesicles (OMVs) that play a critical role in cell–cell communication and virulence. OMVs have emerged as promising therapeutic agents for various biological applications such as vaccines and targeted drug delivery. However, the full potential of OMVs is currently constrained by inherent heterogeneities, such as size and cargo differences, and traditional ensemble assays are limited in their ability to reveal OMV heterogeneity. To overcome this issue, we devised an innovative approach enabling the identification of various characteristics of individual OMVs. This method, employing fluorescence microscopy, facilitates the detection of variations in size and surface markers. To demonstrate our method, we utilize the oral bacterium Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) which produces OMVs with a bimodal size distribution. As part of its virulence, A. actinomycetemcomitans secretes leukotoxin (LtxA) in two forms: soluble and surface associated with the OMVs. We observed a correlation between the size and toxin presence where larger OMVs were much more likely to possess LtxA compared to the smaller OMVs. In addition, we noted that, among the smallest OMVs (<100 nm diameter), the fractions that are toxin positive range from 0 to 30%, while the largest OMVs (>200 nm diameter) are between 70 and 100% toxin positive.

The introduction of super-resolution microscopy (SRM) has significantly advanced our understanding of cellular and molecular dynamics, offering a detailed view previously beyond our reach. Implementing SRM in biophysical research, however, presents numerous challenges. This review addresses the crucial aspects of utilizing SRM effectively, from selecting appropriate fluorophores and preparing samples to analyzing complex data sets. We explore recent technological advancements and methodological improvements that enhance the capabilities of SRM. Emphasizing the integration of SRM with other analytical methods, we aim to overcome inherent limitations and expand the scope of biological insights achievable. By providing a comprehensive guide for choosing the most suitable SRM methods based on specific research objectives, we aim to empower researchers to explore complex biological processes with enhanced precision and clarity, thereby advancing the frontiers of biophysical research.

Antisense oligonucleotide (ASO) represents a class of practical tools for targeting undruggable oncogenes with several candidates currently undergoing clinical investigation. The advancement of antisense therapeutics necessitates comprehensive approaches for evaluating their efficacy and improving their accuracy. Molecular imaging techniques offer a qualitative and quantitative means to assess therapeutics at the molecular, cellular, and in vivo levels, as well as to elucidate biodistribution and pharmacokinetics. These capabilities play a pivotal role in enhancing therapeutic evaluation and efficiency. This review systematically explores the current landscape of ASO delivery by leveraging a synergistic combination of imaging techniques and delivery vehicles to enhance oligonucleotide distribution and accumulation at tumor sites and thereby optimizing therapeutic outcomes.

Methylene blue (MB) is an FDA (Food and Drug Administration)-approved contrast agent with donor–acceptor (D–A) structure integrated with carbonyl-containing nitrogen-heterocycles. MB can be converted into MBH (protonated MB) by protonation, which not only induces the fluorescence emission red-shifted from the first near-infrared window (NIR-I, 650–950 nm) to the second near-infrared window (NIR-II, 1000–1700 nm) but also achieves ACQ-to-AIE conversion. MB has been successfully demonstrated in hyperacidemia imaging with an extremely low pH value (<1).

Liver injury, caused by factors like viral hepatitis and drug overdose, poses a significant health risk, with current diagnostic methods lacking specificity, increasing the need for more precise molecular imaging techniques. Herein, we present an activatable semiconducting liver injury reporter (SLIR) for early and accurate diagnosis of liver injury. The SLIR, which is composed of semiconducting polymers with an electron-withdrawing quenching segment, remains nonfluorescent until it encounters biothiols such as cysteine in the liver. SLIR accumulates efficiently in the liver and respond rapidly to biothiols, allowing accurate and early detection of liver damage. The recovery of SLIR fluorescence negatively reflects the dynamics of oxidative stress in the liver and provides information on the severity of tissue damage. Thus, the specificity of SLIR, the fast response, and the efficient targeting of the liver make it a promising tool for the precise diagnosis of liver damage at an early stage.

Liver injury, caused by factors like viral hepatitis and drug overdose, poses a significant health risk, with current diagnostic methods lacking specificity, increasing the need for more precise molecular imaging techniques. Herein, we present an activatable semiconducting liver injury reporter (SLIR) for early and accurate diagnosis of liver injury. The SLIR, which is composed of semiconducting polymers with an electron-withdrawing quenching segment, remains nonfluorescent until it encounters biothiols such as cysteine in the liver. SLIR accumulates efficiently in the liver and respond rapidly to biothiols, allowing accurate and early detection of liver damage. The recovery of SLIR fluorescence negatively reflects the dynamics of oxidative stress in the liver and provides information on the severity of tissue damage. Thus, the specificity of SLIR, the fast response, and the efficient targeting of the liver make it a promising tool for the precise diagnosis of liver damage at an early stage.

Biological gasotransmitters (small molecules of gases) play important roles in signal transduction mechanisms and disease treatments. Although a large number of small-molecule donors have been developed, visualizing the release of small molecules remains challenging. Owing to their unique optical properties, fluorophores have been widely applied in cellular imaging and tracking. Researchers have used various fluorophores to develop small-molecule donors with fluorescent activity for visualizing the release of small molecules and their related therapies. These include fluorophores and their derivatives such as boron-dipyrromethene (BODIPY), coumarin, 1,8-naphthalimide, hemicyanine, porphyrin, rhodamine, and fluorescein. In this review, we summarize the design concepts of functional fluorescent small-molecule donors in terms of different types of fluorophores. Then, we discuss how these donors release small molecules, and the imaging modalities and biomedical applications facilitated by their fluorescent properties. With the systematic discussion of these publications, we hope to provide useful references for the development of more practical, advanced fluorescent small-molecule donors in the future.

Metal-supported ultrathin ferrous oxide (FeO) has attracted immense interest in academia and industry due to its widespread applications in heterogeneous catalysis. However, chemical insight into the local structural characteristics of FeO, despite its critical importance in elucidating structure–property relationships, remains elusive. In this work, we report the nanoscale chemical probing of gold (Au)-supported ultrathin FeO via ultrahigh-vacuum tip-enhanced Raman spectroscopy (UHV-TERS) and scanning tunneling microscopy (STM). For comparative analysis, single-crystal Au(111) and Au(100) substrates are used to tune the interfacial properties of FeO. Although STM images show distinctly different moiré superstructures on FeO nanoislands on Au(111) and Au(100), TERS demonstrates the same chemical nature of FeO by comparable vibrational features. In addition, combined TERS and STM measurements identify a unique wrinkled FeO structure on Au(100), which is correlated to the reassembly of the intrinsic Au(100) surface reconstruction due to FeO deposition. Beyond revealing the morphologies of ultrathin FeO on Au substrates, our study provides a thorough understanding of the local interfacial properties and interactions of FeO on Au, which could shed light on the rational design of metal-supported FeO catalysts. Furthermore, this work demonstrates the promising utility of combined TERS and STM in chemically probing the structural properties of metal-supported ultrathin oxides on the nanoscale.

The ribosome, a 2.6 megadalton biomolecule measuring approximately 20 nm in diameter, coordinates numerous ligands, factors, and regulators to translate proteins with high fidelity and speed. Understanding its complex functions necessitates multiperspective observations. We developed a dual-FRET single-molecule Förste Resonance Energy Transfer method (dual-smFRET), allowing simultaneous observation and correlation of tRNA dynamics and Elongation Factor G (EF-G) conformations in the same complex, in a 10 s time window. By synchronizing laser shutters and motorized filter sets, two FRET signals are captured in consecutive 5 s intervals with a time gap of 50–100 ms. We observed distinct fluorescent emissions from single-, double-, and quadruple-labeled ribosome complexes. Through comprehensive spectrum analysis and correction, we distinguish and correlate conformational changes in two parts of the ribosome, offering additional perspectives on its coordination and timing during translocation. Our setup’s versatility, accommodating up to six FRET pairs, suggests broader applications in studying large biomolecules and various biological systems.