Polymer dots enable deep in vivo multiphoton fluorescence imaging of microvasculature

Semiconducting polymer dots for multifunctional integrated nanomedicine carriers

The expansion applications of semiconducting polymer dots (Pdots) among optical nanomaterial field have long posed a challenge for researchers, promoting their intelligent application in multifunctional nano-imaging systems and integrated nanomedicine carriers for diagnosis and treatment. Despite notable progress, several inadequacies still persist in the field of Pdots, including the development of simplified near-infrared (NIR) optical nanoprobes, elucidation of their inherent biological behavior, and integration of information processing and nanotechnology into biomedical applications. This review aims to comprehensively elucidate the current status of Pdots as a classical nanophotonic material by discussing its advantages and limitations in terms of biocompatibility, adaptability to microenvironments in vivo, etc. Multifunctional integration and surface chemistry play crucial roles in realizing the intelligent application of Pdots. Information visualization based on their optical and physicochemical properties is pivotal for achieving detection, sensing, and labeling probes. Therefore, we have refined the underlying mechanisms and constructed multiple comprehensive original mechanism summaries to establish a benchmark. Additionally, we have explored the cross-linking interactions between Pdots and nanomedicine, potential yet complete biological metabolic pathways, future research directions, and innovative solutions for integrating diagnosis and treatment strategies. This review presents the possible expectations and valuable insights for advancing Pdots, specifically from chemical, medical, and photophysical practitioners' standpoints.

All fiber-based illumination system for multi-exposure speckle imaging

Monitoring blood flow is critical to treatment efficacy in many surgical settings. Laser speckle contrast imaging (LSCI) is a simple, real-time, label-free optical technique for monitoring blood flow that has emerged as a promising technique but lacks the ability to make repeatable quantitative measurements. Multi-exposure speckle imaging (MESI) is an extension of LSCI that requires increased complexity of instrumentation, which has limited its adoption. In this paper, we design and fabricate a compact, fiber-coupled MESI illumination system (FCMESI) that is substantially smaller and less complex than previous systems. Using microfluidics flow phantoms, we demonstrate that the FCMESI system measures flow with an accuracy and repeatability equivalent to traditional free space MESI illumination systems. With an in vivo stroke model, we also demonstrate the ability of FCMESI to monitor cerebral blood flow changes.

Segmentation-Less, Automated, Vascular Vectorization

Recent advances in two-photon fluorescence microscopy (2PM) have allowed large scale imaging and analysis of blood vessel networks in living mice. However, extracting network graphs and vector representations for the dense capillary bed remains a bottleneck in many applications. Vascular vectorization is algorithmically difficult because blood vessels have many shapes and sizes, the samples are often unevenly illuminated, and large image volumes are required to achieve good statistical power. State-of-the-art, three-dimensional, vascular vectorization approaches often require a segmented (binary) image, relying on manual or supervised-machine annotation. Therefore, voxel-by-voxel image segmentation is biased by the human annotator or trainer. Furthermore, segmented images oftentimes require remedial morphological filtering before skeletonization or vectorization. To address these limitations, we present a vectorization method to extract vascular objects directly from unsegmented images without the need for machine learning or training. The Segmentation-Less, Automated, Vascular Vectorization (SLAVV) source code in MATLAB is openly available on GitHub. This novel method uses simple models of vascular anatomy, efficient linear filtering, and vector extraction algorithms to remove the image segmentation requirement, replacing it with manual or automated vector classification. Semi-automated SLAVV is demonstrated on three in vivo 2PM image volumes of microvascular networks (capillaries, arterioles and venules) in the mouse cortex. Vectorization performance is proven robust to the choice of plasma- or endothelial-labeled contrast, and processing costs are shown to scale with input image volume. Fully-automated SLAVV performance is evaluated on simulated 2PM images of varying quality all based on the large (1.4×0.9×0.6 mm3 and 1.6×108 voxel) input image. Vascular statistics of interest (e.g. volume fraction, surface area density) calculated from automatically vectorized images show greater robustness to image quality than those calculated from intensity-thresholded images.

Multiscale fluorescent tracking of immune cells in the liver with a highly biocompatible far-red emitting polymer probe

The development of innovative immune cell therapies relies on efficient cell tracking strategies. For this, multiscale fluorescence-based analyses of transferred cells into the host with complementary techniques, including flow cytometry for high-throughput cell analysis and two-photon microscopy for deep tissue imaging would be highly beneficial. Ideally, cells should be labelled with a single fluorescent probe combining all the properties required for these different techniques. Due to the intrinsic autofluorescence of most tissues and especially the liver, far-red emission is also an important asset. However, the development of far-red emitting probes suitable for two-photon microscopy and compatible with clearing methods to track labelled immune cells in thick samples, remains challenging. A newly-designed water-soluble far-red emitting polymer probe, 19K-6H, with a large Stokes shift, was thus evaluated for the tracking of primary immune CD8 T cells. These cells, prepared from mouse spleen, were efficiently labelled with the 19K-6H probe, which was internalized via endocytosis and was highly biocompatible at concentrations up to 20 μM. Labelled primary CD8 T cells were detectable in culture by both confocal and two-photon microscopy as well as flow cytometry, even after 3 days of active proliferation. Finally, 19K-6H-labelled primary CD8 T cells were injected to mice in a classical model of immune mediated hepatitis. The efficient tracking of the transferred cells in the liver by flow cytometry (on purified non-parenchymal cells) and by two-photon microscopy on 800 μm thick cleared sections, demonstrated the versatility of the 19K-6H probe.

Visualising brain capillaries in magnetic resonance images via supramolecular self-assembly

We report the supramolecular self-assembly of one fluorescein and three Gd-chelate conjugated 8-arm polyethylene glycols (8-arm PEG-FGd₃) for visualising the capillaries of the brain in magnetic resonance imaging (MRI).

Effect of vascular structure on laser speckle contrast imaging

Laser speckle contrast imaging (LSCI) is a powerful tool for non-invasive, real-time imaging of blood flow in tissue. However, the effect of tissue geometry on the form of the electric field autocorrelation function and speckle contrast values is yet to be investigated. In this paper, we present an ultrafast forward model for simulating a speckle contrast image with the ability to rapidly update the image for a desired illumination pattern and flow perturbation. We demonstrate the first simulated speckle contrast image and compare it against experimental results. We simulate three mouse-specific cerebral cortex decorrelation time images and implement three different schemes for analyzing the effects of homogenization of vascular structure on correlation decay times. Our results indicate that dissolving structure and assuming homogeneous geometry creates up to ∼ 10x shift in the correlation function decay times and alters its form compared with the case for which the exact geometry is simulated. These effects are more pronounced for point illumination and detection imaging schemes, highlighting the significance of accurate modeling of the three-dimensional vascular geometry for accurate blood flow estimates.

Frontiers in Intravital Multiphoton Microscopy of Cancer

Background

Cancer is a highly complex disease which involves the co-operation of tumor cells with multiple types of host cells and the extracellular matrix. Cancer studies which rely solely on static measurements of individual cell types are insufficient to dissect this complexity. In the last two decades, intravital microscopy has established itself as a powerful technique that can significantly improve our understanding of cancer by revealing the dynamic interactions governing cancer initiation, progression and treatment effects, in living animals. This review focuses on intravital multiphoton microscopy (IV-MPM) applications in mouse models of cancer.

Recent Findings

IV-MPM studies have already enabled a deeper understanding of the complex events occurring in cancer, at the molecular, cellular and tissue levels. Multiple cells types, present in different tissues, influence cancer cell behavior via activation of distinct signaling pathways. As a result, the boundaries in the field of IV-MPM are continuously being pushed to provide an integrated comprehension of cancer. We propose that optics, informatics and cancer (cell) biology are co-evolving as a new field. We have identified four emerging themes in this new field. First, new microscopy systems and image processing algorithms are enabling the simultaneous identification of multiple interactions between the tumor cells and the components of the tumor microenvironment. Second, techniques from molecular biology are being exploited to visualize subcellular structures and protein activities within individual cells of interest, and relate those to phenotypic decisions, opening the door for "in vivo cell biology". Third, combining IV-MPM with additional imaging modalities, or omics studies, holds promise for linking the cell phenotype to its genotype, metabolic state or tissue location. Finally, the clinical use of IV-MPM for analyzing efficacy of anti-cancer treatments is steadily growing, suggesting a future role of IV-MPM for personalized medicine.

Conclusion

IV-MPM has revolutionized visualization of tumor-microenvironment interactions in real time. Moving forward, incorporation of novel optics, automated image processing, and omics technologies, in the study of cancer biology, will not only advance our understanding of the underlying complexities but will also leverage the unique aspects of IV-MPM for clinical use.

Multifunctional materials conjugated with near-infrared fluorescent organic molecules and their targeted cancer bioimaging potentialities

Near-infrared fluorescent dyes based on small organic molecules are believed to have a great influence on cancer diagnosis at large and targeted cancer cell bioimaging, in particular. NIR dyes-based organic molecules have notable characteristics features, such as high tissue penetration and low tissue autofluorescence in the NIR spectral region. Cancer targeted bioimaging relies significantly on the synthesis of highly specific molecular probes with excellent stability. Recently, NIR dyes have emerged as unique fluorescent probes for cancer bioimaging. These current advancements have overcome many limitations of conventional NIR probes e.g., poor photostability and hydrophilicity, insufficient stability and low quantum yield. The further potential lies in NIR dyes or NIR dyes-coated nanocarriers conjugated with cancer-specific ligand (e.g., peptides, antibodies, proteins or other small molecules). Multifunctional NIR dyes have synthesized, which efficiently accumulate in cancer cells without requiring chemical conjugation and also these dyes have presented novel photophysical and pharmaceutical properties for in vivo imaging. This review highlights the recently developed NIR dyes with novel applications in cancer bioimaging. We believe that these novel fluorophores will enhance our understanding of cancer imaging and pave a new road in cancer diagnosis and treatment.

Autoluminescence-Free Prostate-Specific Antigen Detection by Persistent Luminous Nanorods and Au@Ag@SiO2 Nanoparticles

The sensitive detection of biomarker with high selectivity and accuracy is of remarkable significance for the early screening and clinical diagnosis of malignant cancer. Persistent phosphors play a role in illumination-free biosensing owing to their unparalleled optical properties, which produces long-lasting luminescence without the illumination to eliminate the interference of autofluorescence and scattering light from biological matrix. In this study, ZnGeO:Mo persistent luminescence nanorods (PLNRs) were prepared and showed tunable luminescence intensity and decay patterns. An excitation-free luminescent aptasensor was proposed for the detection of prostate specific antigen (PSA) by using ZnGeO:Mo PLNRs as probes and Au@Ag@SiO₂ nanoparticles as quenchers. Under optimal conditions, the limit of detection for PSA was 9.2 pg mL^-1. This work creates a possibility for the preparation of multiplex colored persistent luminescence nanomaterials with desired decay patterns for multiple bioassay and time-resolved fluoroimmunoassay.