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Current Medicinal Chemistry 2011With many desirable properties such as ease of synthesis, small size, lack of immunogenicity, and versatile chemistry, aptamers represent a class of targeting ligands... (Review)
Review
With many desirable properties such as ease of synthesis, small size, lack of immunogenicity, and versatile chemistry, aptamers represent a class of targeting ligands that possess tremendous potential in molecular imaging applications. Non-invasive imaging of various disease markers with aptamer-based probes has many potential clinical applications such as lesion detection, patient stratification, treatment monitoring, etc. In this review, we will summarize the current status of molecular imaging with aptamer-based probes. First, fluorescence imaging will be described which include both direct targeting and activatable probes. Next, we discuss molecular magnetic resonance imaging and targeted ultrasound investigations using aptamer-based agents. Radionuclide-based imaging techniques (single-photon emission computed tomography and positron emission tomography) will be summarized as well. In addition, aptamers have also been labeled with various tags for computed tomography, surface plasmon resonance, dark-field light scattering microscopy, transmission electron microscopy, and surface-enhanced Raman spectroscopy imaging. Among all molecular imaging modalities, no single modality is perfect and sufficient to obtain all the necessary information for a particular question. Thus, a multimodality probe has also been constructed for concurrent fluorescence, gamma camera, and magnetic resonance imaging in vivo. Although the future of aptamer-based molecular imaging is becoming increasingly bright and many proof-of-principle studies have already been reported, much future effort needs to be directed towards the development of clinically translatable aptamer-based imaging agents which will eventually benefit patients.
Topics: Animals; Aptamers, Nucleotide; HeLa Cells; Humans; Molecular Imaging
PubMed: 21838686
DOI: 10.2174/092986711797189691 -
Philosophical Transactions of the Royal... Feb 2013Two optical configurations are commonly used in single-molecule fluorescence microscopy: point-like excitation and detection to study freely diffusing molecules, and... (Review)
Review
Two optical configurations are commonly used in single-molecule fluorescence microscopy: point-like excitation and detection to study freely diffusing molecules, and wide field illumination and detection to study surface immobilized or slowly diffusing molecules. Both approaches have common features, but also differ in significant aspects. In particular, they use different detectors, which share some requirements but also have major technical differences. Currently, two types of detectors best fulfil the needs of each approach: single-photon-counting avalanche diodes (SPADs) for point-like detection, and electron-multiplying charge-coupled devices (EMCCDs) for wide field detection. However, there is room for improvements in both cases. The first configuration suffers from low throughput owing to the analysis of data from a single location. The second, on the other hand, is limited to relatively low frame rates and loses the benefit of single-photon-counting approaches. During the past few years, new developments in point-like and wide field detectors have started addressing some of these issues. Here, we describe our recent progresses towards increasing the throughput of single-molecule fluorescence spectroscopy in solution using parallel arrays of SPADs. We also discuss our development of large area photon-counting cameras achieving subnanosecond resolution for fluorescence lifetime imaging applications at the single-molecule level.
Topics: Computational Biology; Diffusion; Electrons; Equipment Design; Fluorescence; Microscopy, Fluorescence; Molecular Conformation; Molecular Imaging; Photons; Sensitivity and Specificity; Time Factors
PubMed: 23267185
DOI: 10.1098/rstb.2012.0035 -
American Journal of Nuclear Medicine... 2018Somatostatin receptors (SSTRs) are variably expressed by a variety of malignancies. Using radiolabeled somatostatin analogs (SSAs), the presence of SSTRs on tumor cells... (Review)
Review
Somatostatin receptors (SSTRs) are variably expressed by a variety of malignancies. Using radiolabeled somatostatin analogs (SSAs), the presence of SSTRs on tumor cells may be exploited for molecular imaging and for peptide receptor radionuclide therapy. In-DTPA-octreotide has long been the standard in SSTR scintigraphy. A major leap forward was the introduction of gallium-68 labeled SSAs for positron emission tomography (PET) offering improved sensitivity. Tracers currently in clinical use are Ga-DOTA-Tyr-octreotide (Ga-DOTATOC), Ga-DOTA-Tyr-octreotate (Ga-DOTATATE) and Ga-DOTA-1-NaI-octreotide (Ga-DOTANOC), collectively referred to as Ga-DOTA-peptides. Ga-DOTA-peptide PET has superseded In-DTPA-octreotide scintigraphy as the modality of choice for SSTR imaging. However, implementation of Ga-DOTA-peptides in routine clinical practice is often limited by practical, economical and regulatory factors related to the use of the current generation of Ge/Ga generators. Centralized production and distribution is challenging due to the low production yield and relatively short half-life of gallium-68. Furthermore, gallium-68 has a relatively long positron range, compromising spatial resolution on modern PET cameras. Therefore, possibilities of using other PET radionuclides are being explored. On the other hand, new developments in SSTR PET ligands are strongly driven by the need for improved lesion targeting, especially for tumors with low SSTR expression. This may be achieved by using peptide vectors having a higher affinity for the SSTR or a broader affinity profile for the different receptor subtypes or by using compounds recognizing more binding sites, such as SSTR antagonists. This review gives an overview of recent developments leading to the next generation of clinical PET tracers for SSTR imaging.
PubMed: 30510849
DOI: No ID Found -
Proceedings of the National Academy of... Jul 2019Plasmons, the collective oscillations of mobile electrons in metallic nanostructures, interact strongly with light and produce vivid colors, thus offering a new route to...
Plasmons, the collective oscillations of mobile electrons in metallic nanostructures, interact strongly with light and produce vivid colors, thus offering a new route to develop color printing technologies with improved durability and material simplicity compared with conventional pigments. Over the last decades, researchers in plasmonics have been devoted to manipulating the characteristics of metallic nanostructures to achieve unique and controlled optical effects. However, before plasmonic nanostructures became a science, they were an art. The invention of the daguerreotype was publicly announced in 1839 and is recognized as the earliest photographic technology that successfully captured an image from a camera, with resolution and clarity that remain impressive even by today's standards. Here, using a unique combination of daguerreotype artistry and expertise, experimental nanoscale surface analysis, and electromagnetic simulations, we perform a comprehensive analysis of the plasmonic properties of these early photographs, which can be recognized as an example of plasmonic color printing. Despite the large variability in size, morphology, and material composition of the nanostructures on the surface of a daguerreotype, we are able to identify and characterize the general mechanisms that give rise to the optical response of daguerreotypes. Therefore, our results provide valuable knowledge to develop preservation protocols and color printing technologies inspired by past ones.
PubMed: 31182585
DOI: 10.1073/pnas.1904331116 -
Archives of Cardiovascular Diseases Dec 2021Myocardial flow reserve represents the ratio of myocardial blood flow between stress and rest, giving functional information about both macrocirculation and... (Review)
Review
Myocardial flow reserve represents the ratio of myocardial blood flow between stress and rest, giving functional information about both macrocirculation and microcirculation; it has been reported extensively in positron emission tomography, with an increase in diagnostic performance, providing important prognostic information and being a powerful tool to guide therapy. Advances in single photon emission computed tomography, with the widespread availability of "cadmium zinc telluride" single photon emission computed tomography cameras, raise the question of myocardial flow reserve use in daily clinical practice. In this article, we review the pathophysiology of myocardial blood flow and myocardial flow reserve, and the initial data available from single photon emission computed tomography myocardial blood flow and myocardial flow reserve evaluation; we also discuss potential limitations to the wider implementation of flow evaluation in single photon emission computed tomography.
Topics: Coronary Angiography; Coronary Artery Disease; Humans; Myocardial Perfusion Imaging; Perfusion; Tomography, Emission-Computed, Single-Photon
PubMed: 34801410
DOI: 10.1016/j.acvd.2021.10.006 -
Philosophical Transactions of the Royal... Jun 1997Light can be used to probe the function and structure of human tissues. We have been exploring two distinct methods: (i) externally emitting light into tissue and... (Review)
Review
Light can be used to probe the function and structure of human tissues. We have been exploring two distinct methods: (i) externally emitting light into tissue and measuring the transmitted light to characterize a region through which the light has passed, and (ii) internally generating light within tissue and using the radiated light as a quantitative homing beacon. The emitted-light approach falls within the domain of spectroscopy, and has allowed for imaging of intracranial haemorrhage in newborns and of brain functions in adults. The generated-light approach is conceptually parallel to positron emission tomography (PET) or nuclear medicine scanning, and has allowed for real-time, non-invasive monitoring and imaging of infection and gene expression in vivo using low-light cameras and ordinary lenses. In this paper, we discuss recent results and speculate on the applications of such techniques.
Topics: Adult; Animals; Brain; Cerebral Hemorrhage; Communicable Diseases; Gene Expression; HIV; Humans; Infant, Newborn; Jurkat Cells; Light; Mice; Mice, Transgenic; Salmonella Infections, Animal; Spectrophotometry, Infrared; Tomography, Emission-Computed; Virus Replication
PubMed: 9232865
DOI: 10.1098/rstb.1997.0059 -
World Journal of Radiology Jul 2015Colorectal cancer is one of the few malignant tumors in which synchronous or metachronous liver metastases [colorectal liver metastases (CRLMs)] may be treated with... (Review)
Review
Colorectal cancer is one of the few malignant tumors in which synchronous or metachronous liver metastases [colorectal liver metastases (CRLMs)] may be treated with surgery. It has been demonstrated that resection of CRLMs improves the long-term prognosis. On the other hand, patients with un-resectable CRLMs may benefit from chemotherapy alone or in addition to liver-directed therapies. The choice of the most appropriate therapeutic management of CRLMs depends mostly on the diagnostic imaging. Nowadays, multiple non-invasive imaging modalities are available and those have a pivotal role in the workup of patients with CRLMs. Although extensive research has been performed with regards to the diagnostic performance of ultrasonography, computed tomography, positron emission tomography and magnetic resonance for the detection of CRLMs, the optimal imaging strategies for staging and follow up are still to be established. This largely due to the progressive technological and pharmacological advances which are constantly improving the accuracy of each imaging modality. This review describes the non-invasive imaging approaches of CRLMs reporting the technical features, the clinical indications, the advantages and the potential limitations of each modality, as well as including some information on the development of new imaging modalities, the role of new contrast media and the feasibility of using parametric image analysis as diagnostic marker of presence of CRLMs.
PubMed: 26217455
DOI: 10.4329/wjr.v7.i7.157 -
Circulation Journal : Official Journal... 2011Nuclear cardiology has played an important role in both diagnosis and risk assessments of coronary artery disease since early 1970. Among the non-invasive diagnostic... (Review)
Review
Physiological assessment of myocardial perfusion using nuclear cardiology would enhance coronary artery disease patient care: which imaging modality is best for evaluation of myocardial ischemia? (SPECT-side).
Nuclear cardiology has played an important role in both diagnosis and risk assessments of coronary artery disease since early 1970. Among the non-invasive diagnostic tests, the great advantage of nuclear imaging is that this technique can obtain physiological information, such as myocardial perfusion, which is difficult to obtain by other techniques. When patients have inducible myocardial ischemia and sufficient viable myocardium, coronary revascularization treatment should be performed. Both stress myocardial perfusion imaging (MPI) and viability imaging provide important information. Another important aspect of stress perfusion imaging is that normal stress perfusion is associated with low risk for future cardiac events. Therefore, stress MPI plays an important role in the selection of an invasive therapeutic regime and also in avoiding unnecessary invasive procedures. As is the case for other imaging techniques, there have been many technical and instrumental developments in recent years in nuclear cardiology imaging, including new single-photon-emission computed tomography tracers, new pharmacological stress agents, a new generation of γ camera, and positron emission tomography. This review will address the advantages of nuclear cardiology in the clinical setting and recent developments in nuclear cardiology.
Topics: Coronary Artery Disease; Humans; Myocardial Ischemia; Myocardial Perfusion Imaging; Radionuclide Imaging; Risk Factors; Sensitivity and Specificity; Stress, Physiological; Tomography, Emission-Computed, Single-Photon
PubMed: 21301136
DOI: 10.1253/circj.cj-10-1290 -
Cancers Sep 2023Prostate cancer (PCa) is one of the most prevalent cancer diagnoses among men in the United States and in several other developed countries. The prostate specific... (Review)
Review
Prostate cancer (PCa) is one of the most prevalent cancer diagnoses among men in the United States and in several other developed countries. The prostate specific membrane antigen (PSMA) has been recognized as a promising molecular target in PCa, which has led to the development of specific radionuclide-based tracers for imaging and radiopharmaceuticals for PSMA targeted therapy. These compounds range from small molecule ligands to monoclonal antibodies (mAbs). Monoclonal antibodies play a crucial role in targeting cancer cell-specific antigens with a high degree of specificity while minimizing side effects to normal cells. The same mAb can often be labeled in different ways, such as with radionuclides suitable for imaging with Positron Emission Tomography (β+ positrons), Gamma Camera Scintigraphy (γ photons), or radiotherapy (β- electrons, α-emitters, or Auger electrons). Accordingly, the use of radionuclide-based PSMA-targeting compounds in molecular imaging and therapeutic applications has significantly grown in recent years. In this article, we will highlight the latest developments and prospects of radiolabeled mAbs that target PSMA for the detection and treatment of prostate cancer.
PubMed: 37760506
DOI: 10.3390/cancers15184537 -
Medical Physics Jul 2008Targeted radionuclide therapy (TRT) seeks molecular and functional targets within patient tumor sites. A number of agents have been constructed and labeled with beta,...
Targeted radionuclide therapy (TRT) seeks molecular and functional targets within patient tumor sites. A number of agents have been constructed and labeled with beta, alpha, and Auger emitters. Radionuclide carriers spanning a broad range of sizes; e.g., antibodies, liposomes, and constructs such as nanoparticles have been used in these studies. Uptake, in percent-injected dose per gram of malignant tissue, is used to evaluate the specificity of the targeting vehicle. Lymphoma (B-cell) has been the primary clinical application. Extension to solid tumors will require raising the macroscopic absorbed dose by several-fold over values found in present technology. Methods that may effect such changes include multistep targeting, simultaneous chemotherapy, and external sequestration of the agent. Toxicity has primarily involved red marrow so that marrow replacement can also be used to enhance future TRT treatments. Correlation of toxicities and treatment efficiency has been limited by relatively poor absorbed dose estimates partly because of using standard (phantom) organ sizes. These associations will be improved in the future by obtaining patient-specific organ size and activity data with hybrid SPECT/CT and PET/CT scanners.
Topics: Bone Marrow; Gamma Cameras; Humans; Iodine Radioisotopes; Medical Oncology; Neoplasms; Phantoms, Imaging; Positron-Emission Tomography; Radiation Oncology; Radioimmunotherapy; Radioisotopes; Radiotherapy Dosage; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed; Yttrium Radioisotopes
PubMed: 18697529
DOI: 10.1118/1.2938520