Imaging In Live Mice Research Articles

Actinidia chinensis polysaccharide interferes with the epithelial-mesenchymal transition of gastric cancer by regulating the nuclear transcription factor-κB pathway to inhibit invasion and metastasis.

To investigate the mechanisms of the effect of Actinidia chinensis polysaccharide (ACPS) on the invasion and metastasis of gastric cancer cells. BGC-823-Luc gastric cancer cells stably transfected with a luciferase gene were used to establish an insitutransplanted tumor mouse model. A live mouse imaging system was used to observe tumor growth, and hematoxylin and eosin staining was applied to analyze tissue histopathology. Transwell and scratch wound assays were performed to examine the invasive and migratory ability of BGC-823 cells. Immunofluorescence, confocal microscopy, immunohistochemistry, and Western blot assays were used to analyze the expressions of the nuclear transcription factor-κB (NF-κB) signaling pathway and epithelial-mesenchymal transition (EMT)-related proteins. ACPS significantly inhibited the growth of subcutaneously transplanted BGC-823-Luc gastric cancer tumors in nude mice and reduced inflammatory cell infiltration in tumor tissues. ACPS inhibited Epidermal Growth Factor-induced invasion, migration, and morphological changes in the cytoskeleton of BGC-823 cells. ACPS inhibited gastric cancer EMT and decreased the expression of matrix metallopeptidase 9, N-cadherin and p-NF-κB p65 in transplanted tumor tissues. ACPS inhibited the expression of matrix metalloproteinases and vascular adhesion factors in BGC-823 cells, promoted p65-NF-κB nuclear translocation, and regulated proteins associated with the NF-κB p65 pathway. ACPS inhibited gastric cancer invasion and metastasis both in vivo and in vitro, which evidenced the inhibition of gastric cancer EMT viaregulating the NF-κB inflammatory pathway.

Regiospecific Coelenterazine Analogs for Bioassays and Molecular Imaging.

Bioluminescence (BL) generated by luciferase-coelenterazine (CTZ) reactions is broadly employed as an optical readout in bioassays and in vivo molecular imaging. In this study, we demonstrate a systematic approach to elucidate the luciferase-CTZ binding chemistry with a full set of regioisomeric CTZ analogs, where all the functional groups were regiochemically modified. When the chemical structures were categorized into Groups 1-6, the even-numbered Groups (2, 4, and 6) of the CTZ analogs are found to be exceptionally bright with NanoLuc enzyme. A CTZ analogue M2 was the brightest with NanoLuc and the reason was deciphered by a computational analysis of the binding modes. We also report that (i) the regioisomeric CTZ analogs collectively create unique intensity patterns according to each marine luciferase, (ii) the quantitative structure-activity relationship analysis revealed the roles of respective functional groups of CTZ analogs, and (iii) the regioisomeric CTZ analogs also exert red shifts of the BL spectra and color variation: that is, the λmax values are near 500 nm with NanoLuc, near 530 nm with ALuc16, and near 570 nm with RLuc86SG. The advantages of the regioisomeric CTZ analogs were finally demonstrated using (i) a dual-luciferase system with M2-specific NanoLuc and native CTZ-specific ALuc16, (ii) an estrogen activatable single-chain BL probe by imaging, and (iii) BL imaging of live mice bearing tumors expressing NanoLuc and RLuc8.6SG. This study is the first systematic approach to elucidate the regiochemistry in BL imaging studies. This study provides new insights into how CTZ analogs regiochemically work in BL reporter systems and guides the specific applications to molecular imaging.

(Invited) Designing Quantum Dots for Multiplexed Deep-Tissue Imaging in the NIR-II

The combination of bright, tunable semiconductor quantum dots (QDs) emitting in the shortwave infrared or second near infrared window (SWIR/NIR-II, 1000 – 1600 nm) and InGaAs camera-equipped preclinical imagers opens the door to non-invasive, multiplexed, deep tissue imaging in live mice. While imaging in the NIR-I is like imaging through fog due to highly scattering tissue, imaging in the SWIR/NIR-II is more like imaging through pond water, enabling deeper imaging with much improved resolution. We synthesized multiple PbS/CdS core/shell QDs with emission wavelengths spanning 1000-1600 nm. These particles have been encapsulated in lipid-PEG micelles and up to three colors (so far) dosed into nude mice for imaging on a Photon Etc IR VIVO imager equipped with a hyperspectral Bragg grating and 6 bandpass filters, enabling demixing of the discrete colors. We have obtained exceptionally clear images of lymphatic drainage and the vasculature system, including visualization of lymphatic valve opening in videos. Interestingly, following intravascular injection, the liver and spleen are very visible and distinct, enabling the non-invasive visualization of a key nanomedicine drug delivery parameter (i.e., are the nanoparticles accumulating in the liver or the spleen?). Image processing investigations are expanding our ability to demix colors as well as to determine the average depth of the contrast agent, based on the wavelength-dependent attenuation of the photoluminescence based on water absorption. In addition to the photophysical advantages of using QDs for NIR-II, elemental analysis of blood and tissue samples enables quantitative biodistribution and pharmacokinetic studies. Ongoing work involves the application of this imaging approach to assess the impact nanomaterial surface properties and route of delivery on their pharmacokinetics and the use of deep tissue paired agent imaging for non-invasive “optical biopsy” of orthotopic tumors. Current data are already visually stunning, and ongoing imaging highlights new opportunities for research with every experiment! Figure 1

Red Fluorescent Molecule with Aggregation-Induced Emission Based on Dehydroabietic Acid Diarylamine for Bioimaging.

In this paper, molecules with AIE red light properties were designed by coupling dehydroabietic acid diarylamine and 2,3-diphenylfumaronitrile, which were designated 2DTPA-CN and 2TPA-CN. The emission wavelengths were 683nm and 701nm, respectively. The 2DTPA-CN and 2TPA-CN showed typical AIE characteristics with large Stokes shifts of 7.4 × 104 cm-1 and 6.7 × 104 cm-1, respectively. The obvious solvatochromism and electron cloud distributions of HOMO/LUMO in the ground and excited states both reveal the intramolecular charge transfer (ICT) effect. The 2DTPA-CN, boasting exceptional biocompatibility, was successfully prepared into nanoparticles (NPs), which were applied to tumor cell imaging, showing good bioimaging effects both in vitro imaging in live cells and in vivo imaging in live mice. The results demonstrated that it possesses significant potential as an effective bioimaging reagent for the detection of tumor cells. Furthermore, the incorporation of 2,3-diphenylfumaronitrile moieties to dehydroabietic acid diarylamine emerged as a proficient approach to broaden the emission wavelengths of rosin-based fluorescent materials.

Unlocking potential of oxytocin: improving intracranial lymphatic drainage for Alzheimer's disease treatment.

Background: The impediment to β-amyloid (Aβ) clearance caused by the invalid intracranial lymphatic drainage in Alzheimer's disease is pivotal to its pathogenesis, and finding reliable clinical available solutions to address this challenge remains elusive. Methods: The potential role and underlying mechanisms of intranasal oxytocin administration, an approved clinical intervention, in improving intracranial lymphatic drainage in middle-old-aged APP/PS1 mice were investigated by live mouse imaging, ASL/CEST-MRI scanning, in vivo two-photon imaging, immunofluorescence staining, ELISA, RT-qPCR, Western blotting, RNA-seq analysis, and cognitive behavioral tests. Results: Benefiting from multifaceted modulation of cerebral hemodynamics, aquaporin-4 polarization, meningeal lymphangiogenesis and transcriptional profiles, oxytocin administration normalized the structure and function of both the glymphatic and meningeal lymphatic systems severely impaired in middle-old-aged APP/PS1 mice. Consequently, this intervention facilitated the efficient drainage of Aβ from the brain parenchyma to the cerebrospinal fluid and then to the deep cervical lymph nodes for efficient clearance, as well as improvements in cognitive deficits. Conclusion: This work broadens the underlying neuroprotective mechanisms and clinical applications of oxytocin medication, showcasing its promising therapeutic prospects in central nervous system diseases with intracranial lymphatic dysfunction.

Mechanisms of skin vascular maturation and maintenance captured by longitudinal imaging of live mice

A functional network of blood vessels is essential for organ growth and homeostasis, yet how the vasculature matures and maintains homeostasis remains elusive in live mice. By longitudinally tracking the same neonatal endothelial cells (ECs) over days to weeks, we found that capillary plexus expansion is driven by vessel regression to optimize network perfusion. Neonatal ECs rearrange positions to evenly distribute throughout the developing plexus and become positionally stable in adulthood. Upon local ablation, adult ECs survive through a plasmalemmal self-repair response, while neonatal ECs are predisposed to die. Furthermore, adult ECs reactivate migration to assist vessel repair. Global ablation reveals coordinated maintenance of the adult vascular architecture that allows for eventual network recovery. Lastly, neonatal remodeling and adult maintenance of the skin vascular plexus are orchestrated by temporally restricted, neonatal VEGFR2 signaling. Our work sheds light on fundamental mechanisms that underlie both vascular maturation and adult homeostasis invivo.

Lead/cadmium-free near-infrared multifunctional nanoplatform for deep-tissue bimodal imaging and drug delivery

Well-designed multifunctional nanoplatforms integrating diagnosis and therapy capabilities are of significant importance in the emerging research area of theranostics, which is expected to have great impact on future medicine. Herein, we rationally designed and engineered a multifunctional NaGdF4:Nd3+@mSiO2 nanoplatform by loading ultrasmall NaGdF4:Nd3+ nanoparticles (∼4.1 nm in diameter) into relatively large-channel mesoporous SiO2 (mSiO2) nanospheres for the first time. Thanks to the unique combination of paramagnetic property, and the capability of being excited by near infrared (NIR) light in the first biological window (NIR-I: 700–950 nm) and emitting in the second biological window (NIR-II: 1000–1350 nm) in single-type nanoparticles of NaGdF4:Nd3+, the NaGdF4:Nd3+@mSiO2 nanoplatform realizes magnetic resonance and NIR photoluminescence dual-mode tumor imaging of live mice. In particular, this NIR-I excitation and NIR-II emission property enables in vitro NIR porcine tissue photoluminescence imaging up to 12 mm in thickness. Moreover, the unique three-dimensional mesoporous structure of the nanoplatform allows the efficient loading of doxorubicin molecules (DOX, a commonly used drug model) at a high level and demonstrates pH-responsive drug release behavior that is beneficial for cancer-targeted therapy. More importantly, this NIR-II emitting nanoplatform does not contain toxic heavy metals of lead (Pb) and cadmium (Cd) usually found in NIR-emitting nanoparticles and further, comprises a highly biocompatible, protective SiO2 network. As a result, the NaGdF4:Nd3+@mSiO2 nanoplatform demonstrates much less cytotoxicity, as compared to the counterpart containing Pb and/or Cd-based quantum dots. All these features endow the multifunctional NaGdF4:Nd3+@mSiO2 nanoplatform great potential in simultaneous disease imaging diagnostics and therapeutics.

Aminophosphate precursors for the synthesis of near-unity emitting InP quantum dots and their application in liver cancer diagnosis.

InP quantum dots (QDs) are a promising and environment-friendly alternative to Cd-based QDs for in vitro diagnostics and bioimaging applications. However, their poor fluorescence and stability severely limit their biological applications. Herein, we synthesize bright (∼100%) and stable InP-based core/shell QDs by using cost-effective and low-toxic phosphorus source, and then aqueous InP QDs are prepared with quantum yield over 80% by shell engineering. The immunoassay of alpha-fetoprotein can be detected in the widest analytical range of 1-1000 ng ml-1 and the limit of detection of 0.58ngml-1 by using those InP QDs-based fluorescent probes, making it the best-performing heavy metal-free detection reported so far, comparable to state-of-the-art Cd-QDs-based probes. Furthermore, the high-quality aqueous InP QDs exhibit excellent performance in specific labeling of liver cancer cells and in vivo tumor-targeted imaging of live mice. Overall, the present work demonstrates the great potential of novel high-quality Cd-free InP QDs in cancer diagnosis and image-guided surgery.

Significant Reduction of Total-Body Irradiation-Induced Death in Mice Treated with PrC-210 24 Hours Postirradiation.

The search for radiation countermeasures that can serve as: i. a pre-exposure agent to protect against subsequent irradiation, and/or ii. a post-exposure agent to mitigate the development of Acute Radiation Syndrome after radiation exposure, remains a prominent goal of the U.S. Government. This study was undertaken to determine whether PrC-210, when administered once, 24 h postirradiation, would provide a survival benefit and would mitigate Acute Radiation Syndrome in mice that had received an otherwise 95-100% lethal radiation dose. Our results show that a single intraperitoneal dose of PrC-210 (0.3-0.4 MTD, 151-201 ug/gm body weight) administered 24 h postirradiation, conferred: i. a 45% survival advantage (P = 0.002) in outbred ICR mice and a 25% survival advantage (P = 0.037) in inbred C57Bl/6 mice, ii. a significant increase in body weight in surviving mice (P = 0.012), iii. a discernible protection of intestinal structure by MRI imaging of live mice, iv. visibly denser jejunal villi and surface epithelium and v. visible bone marrow population in PrC-210-treated mice versus saline controls. The ability of PrC-210 to suppress 100% of radiation-induced death when administered minutes before irradiation, or roughly half of this effect (45%) when administered 24 h postirradiation is noteworthy. Determining the multiple paths by which PrC-210 protection is conferred is a process; the results in this report showing protection of two of the major systems central to Acute Radiation Syndrome damage, is a good first step. This was the first study of PrC-210 administered postirradiation; it conferred substantial survival benefit and suppression of Acute Radiation Syndrome. This outcome supports the continued development of PrC-210 to protect humans exposed to ionizing radiation.

Chemiluminescent 1,2-Dioxetane Iridium Complexes for Near-Infrared Oxygen Sensing.

Chemiluminescent iridium-based sensors which demonstrate oxygen dependent responses have been developed. The molecular probes, named IrCL-1, IrCL-2 and IrCL-3 consist of oxygen-sensitive iridium complexes attached to a spiroadamantane 1,2 dioxetane and operate via energy transfer from the chemiexcited benzoate to the corresponding iridium(III) complex. Complexing the iridium(III) center with π-extended ligands results in emission in the biologically relevant, near-infrared (NIR) region. All probes demonstrate varying oxygen tolerance, with IrCL-1 being the most oxygen sensitive. These probes have been further utilized for in vitro ratiometric imaging of oxygen, as well as for intraperitoneal, intramuscular and intratumoral imaging in live mice. To our knowledge, these are the first iridium-based chemiluminescent probes that have been employed for in vitro ratiometric oxygen sensing, and for in vivo tumor imaging.

Chemiluminescent 1,2‐Dioxetane Iridium Complexes for Near‐Infrared Oxygen Sensing

AbstractChemiluminescent iridium‐based sensors which demonstrate oxygen dependent responses have been developed. The molecular probes, named IrCL‐1, IrCL‐2 and IrCL‐3 consist of oxygen‐sensitive iridium complexes attached to a spiroadamantane 1,2 dioxetane and operate via energy transfer from the chemiexcited benzoate to the corresponding iridium(III) complex. Complexing the iridium(III) center with π‐extended ligands results in emission in the biologically relevant, near‐infrared (NIR) region. All probes demonstrate varying oxygen tolerance, with IrCL‐1 being the most oxygen sensitive. These probes have been further utilized for in vitro ratiometric imaging of oxygen, as well as for intraperitoneal, intramuscular and intratumoral imaging in live mice. To our knowledge, these are the first iridium‐based chemiluminescent probes that have been employed for in vitro ratiometric oxygen sensing, and for in vivo tumor imaging.

Intravital Imaging of the Murine Subventricular Zone with Three Photon Microscopy.

The mouse subventricular zone (SVZ) produces neurons throughout life. It is useful for mechanism discovery and is relevant for regeneration. However, the SVZ is deep, significantly restricting live imaging since current methods do not extend beyond a few hundred microns. We developed and adapted three-photon microscopy (3PM) for non-invasive deep brain imaging in live mice, but its utility in imaging the SVZ niche was unknown. Here, with fluorescent dyes and genetic labeling, we show successful 3PM imaging in the whole SVZ, extending to a maximum depth of 1.5 mm ventral to the dura mater. 3PM imaging distinguished multiple SVZ cell types in postnatal and juvenile mice. We also detected fine processes on neural stem cells interacting with the vasculature. Previous live imaging removed overlying cortical tissue or lowered lenses into the brain, which could cause inflammation and alter neurogenesis. We found that neither astrocytes nor microglia become activated in the SVZ, suggesting 3PM does not induce major damage in the niche. Thus, we show for the first time 3PM imaging of the SVZ in live mice. This strategy could be useful for intravital visualization of cell dynamics, molecular, and pathological perturbation and regenerative events.

Bacteria-Based Live Vehicle for In Vivo Bioluminescence Imaging.

The anticancer therapy strategy mediated by tumor-targeting bacteria needs better visualization tools for imaging and monitoring bacteria in vivo. The probiotic strain Escherichia coli Nissle 1917 (EcN), one of the tumor-targeting bacteria, leads to the potential application for cancer therapy. Here, we report the development and application of a live, EcN-based imageable vehicle for noninvasive in vivo bioluminescence imaging in live mice. Firefly luciferase (Fluc) and luciferin-regenerating enzyme (LRE), an enzyme that contributes to stable bioluminescence, were functionally coexpressed in EcN. The recombinant EcN strain expressing the genomically integrated Fluc-LRE cassette was demonstrated to be a valuable tool for generating robust, continuous, and red-shifted bioluminescence for bacterial tracking in vitro and in vivo, thus providing an optical tumor-targeting system for the in vivo study of bacteria-assisted cancer therapy. Additionally, in vivo imaging of the recombinant EcN strain in the mouse intestinal tract indicated the potential of this strain to be used as a tool in the study of gut.

Experimental Data and PBPK Modeling Quantify Antibody Interference in PEGylated Drug Carrier Delivery.

Physiologically-based pharmacokinetic (PBPK) modeling is a popular drug development tool that integrates physiology, drug physicochemical properties, preclinical data, and clinical information to predict drug systemic disposition. Since PBPK models seek to capture complex physiology, parameter uncertainty and variability is a prevailing challenge: there are often more compartments (e.g., organs, each with drug flux and retention mechanisms, and associated model parameters) than can be simultaneously measured. To improve the fidelity of PBPK modeling, one approach is to search and optimize within the high-dimensional model parameter space, based on experimental time-series measurements of drug distributions. Here, we employ Latin Hypercube Sampling (LHS) on a PBPK model of PEG-liposomes (PL) that tracks biodistribution in an 8-compartment mouse circulatory system, in the presence (APA+) or absence (naïve) of anti-PEG antibodies (APA). Near-continuous experimental measurements of PL concentration during the first hour post-injection from the liver, spleen, kidney, muscle, lung, and blood plasma, based on PET/CT imaging in live mice, are used as truth sets with LHS to infer optimal parameter ranges for the full PBPK model. The data and model quantify that PL retention in the liver is the primary differentiator of biodistribution patterns in naïve versus APA+ mice, and spleen the secondary differentiator. Retention of PEGylated nanomedicines is substantially amplified in APA+ mice, likely due to PL-bound APA engaging specific receptors in the liver and spleen that bind antibody Fc domains. Our work illustrates how applying LHS to PBPK models can further mechanistic understanding of the biodistribution and antibody-mediated clearance of specific drugs.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11538-021-00950-z.

Design of Over-1000 nm Near-Infrared Fluorescent Polymeric Micellar Nanoparticles by Matching the Solubility Parameter of the Core Polymer and Dye.

Polymeric micellar nanoparticles (PNPs) encapsulating over-thousand-nanometer (OTN) near-infrared (NIR) fluorescent dye molecules in block polymers having hydrophobic and hydrophilic chains are promising agents for the dynamic imaging of deep tissue. To achieve OTN-NIR fluorescent PNPs (OTN-PNPs) having high brightness, it is crucial to increase the affinity between the core polymer and dye molecules by matching their polarities; thus, criteria and methods to evaluate the affinity are required. In this study, we used the Hansen solubility parameter (HSP), including the polarity term, to evaluate the affinity between the two substances. HSP values of the OTN-NIR fluorescent dye IR-1061 and four core polymers, poly(lactic-co-glycolic acid) (PLGA), poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL), and polystyrene (PSt), were calculated using the Hansen solubility sphere method and molecular group contribution method, respectively. The relative energy density between IR-1061 and each core polymer calculated using their HSP values revealed that the affinities of PLGA and PLA for IR-1061 are higher than those of PCL and PSt. Therefore, OTN-PNPs composed of PLGA, PLA, and PCL core polymers were prepared and compared. The OTN-PNPs having PLGA and PLA cores could be loaded with larger amounts of IR-1061, had higher photoluminescence intensities, and showed higher stability in phosphate buffered saline than those having PCL cores. Moreover, the OTN-PNPs having PLGA or PLA cores were used for the dynamic imaging of live mice. Thus, matching the solubility parameters of the core polymer and dye molecule is a useful approach for designing high-performance OTN-NIR fluorescent probes.

1237-P: Generation of Targeted Nanoparticles for ß-Cell-Selective Delivery of Antioxidant Drugs

β-cells are highly metabolic and vulnerable to a variety of exogenous stressors, many of which elicit the generation of reactive oxygen species (ROS). Endogenous adaptive responses can restore homeostasis after excessive ROS elevation. If the endogenous adaptive response fails, ROS accumulation can cause damage to DNA, proteins, and organelles, ultimately leading to apoptosis. A wealth of evidence supports that ROS accumulation contributes to β-cell dysfunction and destruction during diabetes development. These findings suggest that stimulating the antioxidant response could prevent or treat diabetes. However, limitations exist in that persistent systemic activation of the antioxidant response can perturb the normal second messenger function of ROS, and that exogenous antioxidants have poor bioavailability and lack specificity. To overcome these obstacles, we developed β-cell targeted nanoparticles to selectively deliver antioxidants to β-cells. We conjugated modified Exendin-4 (Ex4) to an amphiphilic polymer, allowing us to generate lipid nanoparticles to deliver small hydrophobic compounds to GLP-1R expressing cells. We assessed β-cell targeting of our nanoparticles using isolated islets from mice expressing tdTomato selectively in the β-cell. Isolated islets were treated with nanoparticles containing a lipid intercalating dye, DiO, and we observed selective DiO accumulation in tdTomato positive cells. We also performed in vivo imaging of live mice injected with targeted or non-targeted nanoparticles containing a near-IR lipid intercalating dye. These experiments demonstrated selective retention of targeted nanoparticles both systemically and in the pancreata of animals 1 hour after tail vein injection. Collectively, we provide evidence that Ex4 coated micelles are selective to β-cells. Future experiments will explore this targeted approach to deliver drugs to stimulate the antioxidant response and reduce β-cell apoptosis under diabetogenic conditions. Disclosure A. Novak: None. T. Nallan chakravarthula: None. J. Crowder: None. N. J. Alves: None. J. Broichhagen: None. D. Hodson: None. A. Bedwell: None. A. K. Linnemann: None.

Intravital Imaging of Neocortical Heterotopia Reveals Aberrant Axonal Pathfinding and Myelination around Ectopic Neurons.

Neocortical heterotopia consist of ectopic neuronal clusters that are frequently found in individuals with cognitive disability and epilepsy. However, their pathogenesis remains poorly understood due in part to a lack of tractable animal models. We have developed an inducible model of focal cortical heterotopia that enables their precise spatiotemporal control and high-resolution optical imaging in live mice. Here, we report that heterotopia are associated with striking patterns of circumferentially projecting axons and increased myelination around neuronal clusters. Despite their aberrant axonal patterns, in vivo calcium imaging revealed that heterotopic neurons remain functionally connected to other brain regions, highlighting their potential to influence global neural networks. These aberrant patterns only form when heterotopia are induced during a critical embryonic temporal window, but not in early postnatal development. Our model provides a new way to investigate heterotopia formation in vivo and reveals features suggesting the existence of developmentally modulated, neuron-derived axon guidance and myelination factors.

Polymethine‐Based Semiconducting Polymer Dots with Narrow‐Band Emission and Absorption/Emission Maxima at NIR‐II for Bioimaging

AbstractDeep‐penetration fluorescence imaging in the second near‐infrared (NIR‐II) window heralds a new era of clinical surgery, in which high‐resolution vascular/lymphatic anatomy and detailed cancerous tissues can be visualized in real time. Described here is a series of polymethine‐based semiconducting polymers with intrinsic emission maxima in the NIR‐IIa (1300–1400 nm) window and absorption maxima ranging from 1082 to 1290 nm. These polymers were prepared as semiconducting polymer dots (Pdots) in aqueous solutions with fluorescence quantum yields of 0.05–0.18 %, and they demonstrate promising applications in noninvasive through‐skull brain imaging in live mice with remarkable spatial resolution as well as signal‐to‐background contrast. This study offers a platform for future design of NIR‐IIa or even NIR‐IIb emitting Pdots.

Polymethine-Based Semiconducting Polymer Dots with Narrow-Band Emission and Absorption/Emission Maxima at NIR-II for Bioimaging.

Deep-penetration fluorescence imaging in the second near-infrared (NIR-II) window heralds a new era of clinical surgery, in which high-resolution vascular/lymphatic anatomy and detailed cancerous tissues can be visualized in real time. Described here is a series of polymethine-based semiconducting polymers with intrinsic emission maxima in the NIR-IIa (1300-1400 nm) window and absorption maxima ranging from 1082 to 1290 nm. These polymers were prepared as semiconducting polymer dots (Pdots) in aqueous solutions with fluorescence quantum yields of 0.05-0.18 %, and they demonstrate promising applications in noninvasive through-skull brain imaging in live mice with remarkable spatial resolution as well as signal-to-background contrast. This study offers a platform for future design of NIR-IIa or even NIR-IIb emitting Pdots.

Immunotoxin SS1P is rapidly removed by proximal tubule cells of kidney, whose damage contributes to albumin loss in urine

Recombinant immunotoxins (RITs) are chimeric proteins composed of an Fv and a protein toxin being developed for cancer treatment. The Fv brings the toxin to the cancer cell, but most of the RITs do not reach the tumor and are removed by other organs. To identify cells responsible for RIT removal, and the pathway by which RITs reach these cells, we studied SS1P, a 63-kDa RIT that targets mesothelin-expressing tumors and has a short serum half-life. The major organs that remove RIT were identified by live mouse imaging of RIT labeled with FNIR-Z-759. Cells responsible for SS1P removal were identified by immunohistochemistry and intravital two-photon microscopy of kidneys of rats. The primary organ of SS1P removal is kidney followed by liver. In the kidney, SS1P passes through the glomerulus, is taken up by proximal tubular cells, and transferred to lysosomes. In the liver, macrophages are involved in removal. The short half-life of SS1P is due to its very rapid filtration by the kidney followed by degradation in proximal tubular cells of the kidney. In mice treated with SS1P, proximal tubular cells are damaged and albumin in the urine is increased. SS1P uptake by kidney is reduced by coadministration of l-lysine. Our data suggests that l-lysine administration to humans might prevent SS1P-mediated kidney damage, reduce albumin loss in urine, and alleviate capillary leak syndrome.