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A convergent total synthesis of the siderophore coelichelin is described. The synthetic route also provided access to acetyl coelichelin and other congeners of the parent siderophore. The synthetic products were evaluated for their ability to bind ferric iron and promote growth of a siderophore-deficient strain of the Gram-negative bacterium Pseudomonas aeruginosa under iron restriction conditions. The results of these studies indicate coelichelin and several derivatives serve as ferric iron delivery vehicles for P. aeruginosa.
Mouse laser-induced choroidal neovascularization (mouse LCNV) recapitulates the "wet" form of human age-related macular degeneration (AMD). Vascular cell adhesion molecule-1 (VCAM-1) is a known inflammatory biomarker, and it increases in the choroidal neovascular tissues characteristic of this experimental model. We have designed and constructed gold nanoparticles (AuNPs) functionalized with hairpin-DNA that incorporates an antisense sequence complementary to VCAM-1 mRNA (AS-VCAM-1 hAuNPs) and tested them as optical imaging probes. The 3' end of the hairpin is coupled to a near-infrared fluorophore that is quenched by the AuNP surface via Förster resonance energy transfer (FRET). Hybridization of the antisense sequence to VCAM-1 mRNA displaces the fluorophore away from the AuNP surface, inducing fluorescent activity. In vitro testing showed that hAuNPs hybridize to an exogenous complementary oligonucleotide within a pH range of 4.5-7.4, and that they are stable at reduced pH. LCNV mice received tail-vein injections of AS-VCAM-1 hAuNPs. Hyperspectral imaging revealed the delivery of AS-VCAM-1 hAuNPs to excised choroidal tissues. Fluorescent images of CNV lesions were obtained, presumably in response to the hybridization of AS-hAuNPs to LCNV-induced VCAM-1 mRNA. This is the first demonstration of systemic delivery of hAuNPs to ocular tissues to facilitate mRNA imaging of any target.
Translocator Protein (18 kDa, TSPO) is regarded as a useful biomarker for neuroinflammation imaging. TSPO PET imaging could be used to understand the role of neuroinflammation in brain diseases and as a tool for evaluating novel therapeutic effects. As a promising TSPO probe, [F]DPA-714 is highly specific and offers reliable quantification of TSPO in vivo. In this study, we further radiosynthesized and evaluated another novel TSPO probe, 2-(7-butyl-2-(4-(2-[F]fluoroethoxy)phenyl)-5-methylpyrazolo[1,5-a]pyrimidin-3-yl)-N,N-diethylacetamide ([F]VUIIS1018A), which features a 700-fold higher binding affinity for TSPO than that of [F]DPA-714. We evaluated the performance of [F]VUIIS1018A using dynamic in vivo PET imaging, radiometabolite analysis, in vitro autoradiography assays, biodistribution analysis, and blocking assays. In vivo study using this probe demonstrated high signal-to-noise ratio, binding potential (BP), and binding specificity in preclinical neuroinflammation studies. Taken together, these findings indicate that [F]VUIIS1018A may serve as a novel TSPO PET probe for neuroinflammation imaging.
Copyright © 2018. Published by Elsevier Masson SAS.
Increasing evidence supports the hypothesis that soluble misfolded protein assemblies contribute to the degeneration of postmitotic tissue in amyloid diseases. However, there is a dearth of reliable nonantibody-based probes for selectively detecting oligomeric aggregate structures circulating in plasma or deposited in tissues, making it difficult to scrutinize this hypothesis in patients. Hence, understanding the structure-proteotoxicity relationships driving amyloid diseases remains challenging, hampering the development of early diagnostic and novel treatment strategies. We report peptide-based probes that selectively label misfolded transthyretin (TTR) oligomers circulating in the plasma of TTR hereditary amyloidosis patients exhibiting a predominant neuropathic phenotype. These probes revealed that there are much fewer misfolded TTR oligomers in healthy controls, in asymptomatic carriers of mutations linked to amyloid polyneuropathy, and in patients with TTR-associated cardiomyopathies. The absence of misfolded TTR oligomers in the plasma of cardiomyopathy patients suggests that the tissue tropism observed in the TTR amyloidoses is structure-based. Misfolded oligomers decrease in TTR amyloid polyneuropathy patients treated with disease-modifying therapies (tafamidis or liver transplant-mediated gene therapy). In a subset of TTR amyloid polyneuropathy patients, the probes also detected a circulating TTR fragment that disappeared after tafamidis treatment. Proteomic analysis of the isolated TTR oligomers revealed a specific patient-associated signature composed of proteins that likely associate with the circulating TTR oligomers. Quantification of plasma oligomer concentrations using peptide probes could become an early diagnostic strategy, a response-to-therapy biomarker, and a useful tool for understanding structure-proteotoxicity relationships in the TTR amyloidoses.
Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
The Thomsen-Friedenreich (TF) antigen represents a prognostic biomarker of colorectal carcinoma. Here, using a nanobeacon, the surface of which was fabricated with peanut agglutinin as TF-binding molecules, we demonstrate that the nanobeacon is able to detect TF antigen in frozen and freshly biopsied polyps using fluorescence microscopy. Our results provide important clues about how to detect aberrant colonic tissues in the most timely fashion. Given the versatile application method for this topical nanobeacon, the protocol used in this work is amenable to clinical colonoscopy. Moreover, the prospects of clinical translation of this technology are evident.
The effective identification, selection, and implementation of small molecules for the interrogation of biological systems require an intricate understanding of the chemical principles underlying their cellular activities. While much has been published regarding the use of screening techniques in forward chemical genetics platforms and on small-molecule target identification, less emphasis has been placed on detailed strategies for evaluating, selecting, and optimizing screening hits. This chapter provides practical tools for identifying and developing promising screening hit compounds into effective tools for biological discovery.
Academic radiology is poised to play an important role in the development and implementation of quantitative imaging (QI) tools. This article, drafted by the Association of University Radiologists Radiology Research Alliance Quantitative Imaging Task Force, reviews current issues in QI biomarker research. We discuss motivations for advancing QI, define key terms, present a framework for QI biomarker research, and outline challenges in QI biomarker development. We conclude by describing where QI research and development is currently taking place and discussing the paramount role of academic radiology in this rapidly evolving field.
Copyright © 2015 AUR. Published by Elsevier Inc. All rights reserved.
Quantitative imaging (QI) is increasingly applied in modern radiology practice, assisting in the clinical assessment of many patients and providing a source of biomarkers for a spectrum of diseases. QI is commonly used to inform patient diagnosis or prognosis, determine the choice of therapy, or monitor therapy response. Because most radiologists will likely implement some QI tools to meet the patient care needs of their referring clinicians, it is important for all radiologists to become familiar with the strengths and limitations of QI. The Association of University Radiologists Radiology Research Alliance Quantitative Imaging Task Force has explored the clinical application of QI and summarizes its work in this review. We provide an overview of the clinical use of QI by discussing QI tools that are currently used in clinical practice, clinical applications of these tools, approaches to reporting of QI, and challenges to implementing QI. It is hoped that these insights will help radiologists recognize the tangible benefits of QI to their patients, their referring clinicians, and their own radiology practice.
Copyright © 2015 AUR. Published by Elsevier Inc. All rights reserved.
Hypoxia has been associated with retinal diseases which lead the causes of irreversible vision loss, including diabetic retinopathy, retinopathy of prematurity, and age-related macular degeneration. Therefore, technologies for imaging hypoxia in the retina are needed for early disease detection, monitoring of disease progression, and assessment of therapeutic responses in the patient. Toward this goal, we developed two hypoxia-sensitive imaging agents based on nitroimidazoles which are capable of accumulating in hypoxic cells in vivo. 2-nitroimidazole or Pimonidazole was conjugated to fluorescent dyes to yield the imaging agents HYPOX-1 and HYPOX-2. Imaging agents were characterized in cell culture and animal models of retinal vascular diseases which exhibit hypoxia. Both HYPOX-1 and -2 were capable of detecting hypoxia in cell culture models with >10:1 signal-to-noise ratios without acute toxicity. Furthermore, intraocular administration of contrast agents in mouse models of retinal hypoxia enabled ex vivo detection of hypoxic tissue. These imaging agents are a promising step toward translation of hypoxia-sensitive molecular imaging agents in preclinical animal models and patients.
Cannabinoid CB2 receptors (CB2R) hold promise as therapeutic targets for treating diverse diseases, such as cancers, neurodegenerative diseases, pain, inflammation, osteoporosis, psychiatric disorders, addiction, and immune disorders. However, the fundamental role of CB2R in the regulation of diseases remains unclear, largely due to a lack of reliable imaging tools for the receptors. The goal of this study was to develop a CB2R-targeted molecular imaging probe and evaluate the specificity of the probe using human tumor cells that naturally overexpress CB2R. To synthesize the CB2R-targeted probe (NIR760-Q), a conjugable CB2R ligand based on the quinolone structure was first prepared, followed by bioconjugation with a near-infrared (NIR) fluorescent dye, NIR760. In vitro fluorescence imaging and competitive binding studies showed higher uptake of NIR760-Q than free NIR760 dye in Jurkat human acute T-lymphoblastic leukemia cells. In addition, the high uptake of NIR760-Q was significantly inhibited by the blocking agent, 4-quinolone-3-carboxamide, indicating specific binding of NIR760-Q to the target receptors. These results indicate that the NIR760-Q has potential in diagnostic imaging of CB2R positive cancers and elucidating the role of CB2R in the regulation of disease progression.