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Photoacoustic imaging (PA imaging or PAI) has been focused on as a new technique to provide images of high spatial resolution, at depths of up to 5 cm, and the development of novel PAI probes for tumor imaging is of marked interest. Although nanomaterials such as gold nanorods have been reported as PAI probes, dyes are required to aid their ease of preparation, cost-effectiveness, and safety. However, because PAI has relatively low intrinsic sensitivity compared to optical imaging, and requires high-energy laser pulse exposure, an appropriate probe design, high tumor accumulation, and photostability are required for PAI probes. We developed some dyes and evaluated their usefulness as PAI probes. We first developed a high tumor-accumulation dye probe, IC7-1-Bu, which utilizes serum albumin as a tumor-targeting carrier to deliver an adequate PA signal at the tumor. Although IC7-1-Bu showed strong tumor targeting ability and a sufficient PA signal at the tumor in in vivo studies, IC7-1-Bu lacks photostability against multiple laser irradiations of PAI. In order to improve dye photostablity, we focused on the effect of singlet oxygen ((1)O2) generated by excited PAI probes on probe degeneration, and developed a triplet-state quencher conjugated dye probe, IC-5-T. IC-5-T reduced (1)O2 generation and improved photostability against multiple irradiations compared to IC7-1-Bu. IC-5-T also showed a sufficient PA signal at the tumor, and 1.5-fold higher photostabillity compared to IC7-1-Bu in sequential in vivo PAI studies. These results suggest that IC-5-T is a potential PAI probe for tumor imaging.

Nanoparticles have recently emerged as an important group of materials used in numerous disciplines within the life sciences, ranging from basic biophysical research to clinical therapeutics. Luminescent nanoparticles make excellent optical bioprobes significantly extending the capabilities of alternative fluorophores such as organic dyes and genetically engineered fluorescent proteins. Their advantages include excellent photostability, tunable and narrow spectra, controllable size, resilience to environmental conditions such as pH and temperature, combined with a large surface for anchoring targeting biomolecules. Some types of nanoparticles provide enhanced detection contrast due to their long emission lifetime and/or luminescence wavelength blue-shift (anti-Stokes) due to energy upconversion. This topical review focuses on four key types of luminescent nanoparticles whose emission is governed by different photophysics. We discuss the origin and characteristics of optical absorption and emission in these nanoparticles and give a brief account of synthesis and surface modification procedures. We also introduce some of their applications with opportunities for further development, which could be appreciated by the physics-trained readership.

A molecular beacon (MB) is a hairpin-structured oligonucleotide probe containing a photoluminescent species (PLS) and a quencher at different ends of the strand. In a recognition and detection process, the hybridization of MBs with target DNA sequences restores the strong photoluminescence, which is quenched before hybridization. Making better MBs involves reducing the background photoluminescence and increasing the brightness of the PLS, which therefore involves the development of new PLS and quenchers, as well as innovative PLS-quencher systems. Heavy-metal complexes, nanocrystals, pyrene compounds, and other materials with excellent photophysical properties have been applied as PLS of MBs. Nanoparticles, nanowires, graphene, metal films, and many other media have also been introduced to quench photoluminescence. On the basis of their high specificity, selectivity, and sensitivity, MBs are developed as a general platform for sensing, producing, and carrying molecules other than oligonucleotides.

The development of surface-attached sensors for cationic and anionic guests is of intense current research interest. In addition to the environmental flexibility, robustness and reusability of such devices, surface-confined sensors typically exhibit an amplified response to target analytes owing to preorganization of the receptor. Whereas redox-active cations may be sensed by studying the cyclic voltammetry of host-guest systems containing ion-selective receptors attached to an appropriate electrode, redox-inactive ionic species require the use of electrochemical impedance spectroscopy, with appropriately functionalized electrodes and redox probes. Alternatively, receptors may be constructed that incorporate an electrochemical or optical reporter group within their structure to provide a macroscopic response to the presence of an ionic guest. This critical review seeks to present an up-to-date, although necessarily selective, account of the progress in the field, and provides insights into possible future developments, including the utilization of receptor-nanoparticle conjugates and mechanically interlocked receptors.

In recent years fluorescence correlation spectroscopy (FCS) has become a routine method for determining diffusion coefficients, chemical rate constants, molecular concentrations, fluorescence brightness, triplet state lifetimes, and other molecular parameters. FCS measures the spatial and temporal correlation of individual molecules with themselves and so provides a bridge between classical ensemble and contemporary single-molecule measurements. It also provides information on concentration and molecular number fluctuations for nonlinear reaction systems that complement single-molecule measurements. Typically implemented on a fluorescence microscope, FCS samples femtoliter volumes and so is especially useful for characterizing small dynamic systems such as biological cells. In addition to its practical utility, however, FCS provides a window on mesoscopic systems in which fluctuations from steady states not only provide the basis for the measurement but also can have important consequences for the behavior and evolution of the system. For example, a new and potentially interesting field for FCS studies could be the study of nonequilibrium steady states, especially in living cells., (Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

Objective: Conventional anatomic imaging biomarkers, including World Health Organization (WHO) criteria and Response Evaluation Criteria in Solid Tumors (RECIST), although effective, have limitations. This article will discuss the conventional and newer morphologic imaging biomarkers for the assessment of tumor response to therapy., Conclusion: Applying established methods of assessing tumor response to therapy allows consistency in image interpretation and facilitates communication with oncologists. Because of the new methods of treatment, assessment of necrosis and volumetric information will need to be incorporated into size-based criteria.

Molecular and cell biology have not only greatly advanced our understanding of the pathogenesis of numerous human diseases but at the same time contributed to their diagnosis, therapy and prevention. Based on modern genetic as well as epigenetic and biochemical analyses it is possible to identify on the one hand point mutations and single nucleotide polymporphisms (SNPs) as well as epigenetic modifications. On the other hand, using high throughput array technologies, it is possible to analyze thousands of genes simultaneously, resulting in an individual gene or gene expression profile (signature). These data increasingly allow to define the individual risk for a given disease and to predict the individual prognosis of a disease as well as the efficacy of therapeutic strategies (personalized medicine)., (© Georg Thieme Verlag KG Stuttgart · New York.)

The in situ ligation (ISL) methodology detects apoptotic cells by the presence of characteristic DNA double-strand breaks. A labeled double-stranded probe is ligated to the double-strand breaks in situ on tissue sections. Like the popular TUNEL assay, ISL detects cells in apoptosis based on the ongoing destruction of DNA by apoptotic nucleases. In comparison to TUNEL, it is more specific for apoptosis versus other causes of DNA damage, both repairable damage and necrosis. In the decade and a half since its introduction, ISL has been used in several hundred publications. Here we review the development of the method, its current status, and its uses and limitations.

Many clinical decisions in the management of bladder cancer would benefit from better and reliable knowledge of individual prognosis. Marker for urothelial cancer can principally be measured in blood, urine and transurethrally resected tissue. In recent years new markers have been identified by new technologies and this opens exiting avenues. Since no single marker gives a clear Yes-or-no prognostic answer but always only a measure of probability, the use of marker systems has so far not gained widespread clinical applications. This will likely change in future.

Ultrasonography (US) is one of the most commonly used diagnostic modalities in clinical medicine. Gas-filled microbubbles can be used to enhance the contrast of tumors by indicating increased vascularity. Because microbubbles can be detected with high sensitivity and specificity, they fulfill an important precondition for use as a molecular imaging probe. Over the past several years, there have been an increasing number of published studies that showed that markers of angiogenesis and inflammation can be assessed reliably when microbubbles are coupled to antibodies and peptides. Recently, target-specific microbubbles have been developed that are suited for use in humans. Now the identification of the optimal clinical indications for molecular US imaging in clinics is required. In this context, advantages and limitations of US with targeted microbubbles, when compared with other imaging modalities, must be carefully considered. Because US is a transportable, cheap, real-time imaging modality, molecular US imaging may have advantages for initial tumor screening and US-guided interventions; furthermore, it may support therapy monitoring in intervals between whole-body images obtained with positron emission tomography (PET), computed tomography (CT), and magnetic resonance (MR) imaging.

Early diagnosis by molecular tests has increasingly catched attention after deciphering the complete human genome sequence in 2001. Meanwhile, complete genome sequencing will soon become available for each individual. Molecular testing is standard of care in certain infectious or malignant diseases. Novel biomarkers are emerging as a result of modern comprehensive procedures (transcriptomics, proteomics, metabolomics etc). However, hype and hope are particularly close in this field and responsible conduct by clinicians will ensure beneficial use of new tests.

This review focuses on the use of Förster Resonance Energy Transfer (FRET) to monitor intra- and intermolecular reactions occurring in microfluidic reactors. Microfluidic devices have recently been used for performing highly efficient and miniaturised biological assays for the analysis of biological entities such as cells, proteins and nucleic acids. Microfluidic assays are characterised by nanolitre to femtolitre reaction volumes, which necessitates the adoption of a sensitive optical detection scheme. FRET serves as a strong 'spectroscopic ruler' for elucidating the tertiary structure of biomolecules, as the efficiency of the non-radiative energy transfer is extremely sensitive to nanoscale changes in the separation between donor and acceptor markers attached to the biomolecule of interest. In this review, we will review the implementation of various microfluidic assays which employ FRET for diverse applications in the biomedical field, along with the advantages and disadvantages of the various approaches. The future prospects for development of microfluidic devices incorporating FRET detection will be discussed.

Noninvasive molecular imaging approaches include nuclear, optical, magnetic resonance imaging, computed tomography, ultrasound, and photoacoustic imaging, which require accumulation of a signal delivered by a probe at the target site. Monoclonal antibodies are high affinity molecules that can be used for specific, high signal delivery to cell surface molecules. However, their long circulation time in blood makes them unsuitable as imaging probes. Efforts to improve antibodies pharmacokinetics without compromising affinity and specificity have been made through protein engineering. Antibody variants that differ in antigen binding sites and size have been generated and evaluated as imaging probes to target tissues of interest. Fast clearing fragments, such as single-chain variable fragment (scFv; 25 kDa), with 1 antigen-binding site (monovalent) demonstrated low accumulation in tumors because of the low exposure time to the target. Using scFv as building block to produce larger, bivalent fragments, such as scFv dimers (diabodies, 50 kDa) and scFv-fusion proteins (80 kDa minibodies and 105 kDa scFv-Fc), resulted in higher tumor accumulation because of their longer residence time in blood. Imaging studies with these fragments after radiolabeling have demonstrated excellent, high-contrast images in gamma cameras and positron emission tomography scanners. Several studies have also investigated antibody fragments conjugated to fluorescence (near infrared dyes), bioluminescence (luciferases), and quantum dots for optical imaging and iron oxides nanoparticles for magnetic resonance imaging. However, these studies indicate that there are several factors that influence successful targeting and imaging. These include stability of the antibody fragment, the labeling chemistry (direct or indirect), whether critical residues are modified, the number of antigen expressed on the cell, and whether the target has a rapid recycling rate or internalizes upon binding. The preclinical data presented are compelling, and it is evident that antibody-based molecular imaging tracers will play an important future role in the diagnosis and management of cancer and other diseases., (Copyright 2010 Elsevier Inc. All rights reserved.)

Positron emission tomography (PET) is playing an increasingly important role in the diagnosis, staging, and monitoring response to treatment in a variety of cancers. Recent efforts have focused on immuno-PET, which uses antibody-based radiotracers, to image tumors based on expression of tumor-associated antigens. It is postulated that the specificity afforded by antibody targeting should both improve tumor detection and provide phenotypic information related to primary and metastatic lesions that will guide therapy decisions. Advances in antibody-engineering are providing the tools to develop antibody-based molecules with pharmacokinetic properties optimized for use as immuno-PET radiotracers. Coupled with technical advances in the design of PET scanners, immuno-PET holds promise to improve diagnostic imaging and to guide the use of targeted therapies. An overview of the preclinical immuno-PET studies in cancer models is reviewed here., (Copyright 2010 Elsevier Inc. All rights reserved.)

Atherosclerotic plaque disruption accounts for the major part of cardiovascular mortality and the risk of disruption appears to depend on plaque composition. Carotid plaques in patients, scheduled for endarterectomy, have been successfully characterised with MRI. MRI has the advantage of combining information about morphology and function. Unfortunately, the tortuosity and size of the coronary arteries, and the respiratory and cardiac motion hinder the in vivo characterisation of human coronary plaque. In addition to plaque composition several molecular markers of the different processes involved in atherosclerosis, such as integrins, matrix metalloproteinases and fibrin seem to correlate with risk of plaque rupture and clinical outcome. These molecular markers can be targeted with antibodies coupled to carriers, which are loaded with gadolinium for detection (molecular MRI). Several cellular/molecular MRI studies in animal models and some in human patients have been conducted with varying levels of success. The advent of clinical high field magnets, the development of contrast agent carriers with high relaxivity and the development of relatively new MR contrast techniques are promising in the field of plaque imaging. Future MRI studies will have to focus on the molecular target of the atherosclerotic process, which has the highest prognostic value with regard to acute coronary syndromes and on the most suitable contrast agent to visualize that target.

Protein activity is essential functional information, yet difficult to predict from transcript or protein data. Activity-based protein profiling (ABPP) displays active proteins in proteomes using small molecule probes that irreversibly label proteins in their active state. Here, we review proof-of-concept ABPP studies in plant science. These studies displayed activities of dozens of plant cysteine proteases, lipases, methylesterases and the proteasome. ABPP in plants revealed differential protein activities in development and immunity and uncovered striking selectivity of pathogen-derived inhibitors and unexpected targets of commercial inhibitors. The unique, high-content information of ABPP and the robustness and simplicity of the assays will make ABPP a powerful tool in future plant science and biotechnology., (Copyright 2010 Elsevier Ltd. All rights reserved.)

The organisers of this conference have kindly provided me with the forum to look forward and examine the future of medical imaging. My view of the future is informed by my own research directions; thus, I illustrate my vision of the future with results from my own research, and from the research that has motivated me over the last few years. As such, the results presented are specific to the field of breast imaging; however, I believe that the trends presented have general applicability, and hope that this discourse will motivate new research. My vision of the future can be summarised in accordance with three broad trends: (1) increased prevalence of low-dose tomographic X-ray imaging; (2) continuing advances in functional and molecular X-ray imaging; and (3) novel image-based biomarker discovery.

Atherosclerotic plaque disruption accounts for the major part of cardiovascular mortality and the risk of disruption appears to depend on plaque composition. Carotid plaques in patients, scheduled for endarterectomy, have been successfully characterised with MRI. MRI has the advantage of combining information about morphology and function. Unfortunately, the tortuosity and size of the coronary arteries, and the respiratory and cardiac motion hinder the in vivo characterisation of human coronary plaque. In addition to plaque composition several molecular markers of the different processes involved in atherosclerosis, such as integrins, matrix metalloproteinases and fibrin seem to correlate with risk of plaque rupture and clinical outcome. These molecular markers can be targeted with antibodies coupled to carriers, which are loaded with gadolinium for detection (molecular MRI). Several cellular/molecular MRI studies in animal models and some in human patients have been conducted with varying levels of success. The advent of clinical high field magnets, the development of contrast agent carriers with high relaxivity and the development of relatively new MR contrast techniques appear to be promising in the field of plaque imaging. Future MRI studies will have to focus on the molecular target of the atherosclerotic process, which has the highest prognostic value with regard to acute coronary syndromes and on the most suitable contrast agent to visualize that target.

The spatiotemporal patterns of ion and metabolite levels in living cells are important in understanding signal transduction and metabolite flux. Imaging approaches using genetically encoded sensors are ideal for detecting such molecule dynamics, which are hard to capture otherwise. Recent years have seen iterative improvements and evaluations of sensors, which in turn are starting to make applications in more challenging experimental settings possible. In this review, we will introduce recent progress made in the variety and properties of biosensors, and how biosensors are used for the measurement of metabolite and ion in live cells. The emerging field of applications, such as parallel imaging of two separate molecules, high-resolution transport studies and high-throughput screening using biosensors, will be discussed.

The closing of the last century opened a wide variety of approaches for inflammation imaging and treatment of patients with rheumatoid arthritis (RA). The introduction of biological therapies for the management of RA started a revolution in the therapeutic armamentarium with the development of several novel monoclonal antibodies (mAbs), which can be murine, chimeric, humanised and fully human antibodies. Monoclonal antibodies specifically bind to their target, which could be adhesion molecules, activation markers, antigens or receptors, to interfere with specific inflammation pathways at the molecular level, leading to immune-modulation of the underlying pathogenic process. These new generation of mAbs can also be radiolabelled by using direct or indirect method, with a variety of nuclides, depending upon the specific diagnostic application. For studying rheumatoid arthritis patients, several monoclonal antibodies and their fragments, including anti-TNF-alpha, anti-CD20, anti-CD3, anti-CD4 and anti-E-selectin antibody, have been radiolabelled mainly with (99m)Tc or (111)In. Scintigraphy with these radiolabelled antibodies may offer an exciting possibility for the study of RA patients and holds two types of information: (1) it allows better staging of the disease and diagnosis of the state of activity by early detection of inflamed joints that might be difficult to assess; (2) it might provide a possibility to perform 'evidence-based biological therapy' of arthritis with a view to assessing whether an antibody will localise in an inflamed joint before using the same unlabelled antibody therapeutically. This might prove particularly important for the selection of patients to be treated since biological therapies can be associated with severe side-effects and are considerably expensive. This article reviews the use of radiolabelled mAbs in the study of RA with particular emphasis on the use of different radiolabelled monoclonal antibodies for therapy decision-making and follow-up.

We have not yet reached a point at which routine sequencing of large numbers of whole eukaryotic genomes is feasible, and so it is often necessary to select genomic regions of interest and to enrich these regions before sequencing. There are several enrichment approaches, each with unique advantages and disadvantages. Here we describe our experiences with the leading target-enrichment technologies, the optimizations that we have performed and typical results that can be obtained using each. We also provide detailed protocols for each technology so that end users can find the best compromise between sensitivity, specificity and uniformity for their particular project.

Through labelling of cells with magnetic contrast agents it is possible to follow the fate of transplanted cells in vivo with magnetic resonance imaging (MRI) as has been demonstrated in animal studies as well as in a clinical setting. A large variety of labelling strategies are available that allow for prolonged and sensitive detection of the labelled cells with MRI. The various protocols each harbour specific advantages and disadvantages. In choosing a particular labelling strategy it is also important to ascertain that the labelling procedure does not negatively influence cell functionality, for which a large variety of assays are available. In order to overcome the challenges still faced in fully exploiting the benefits of in vivo cell tracking by MRI a good understanding and standardisation of the procedures and assays used will be crucial.

Radiation therapy is one of the effective curative treatments for uterine cervical cancer. However poor clinical results for the advanced stages require further improvement of the treatment. Intensive studies on basic and clinical research have been made to improve local control, primarily important for long term survival in radiation therapy. Regarding current advancement in radiation therapy for uterine cervical cancer, the following three major subjects are pointed out; technological development to improve dose distribution by image guided radiation therapy technology, the concomitant anticancer chemotherapy with combination of radiation therapy, and radiation biological assessment of the radiation resistance of tumors. The biological factors overviewed in this article include hypoxia relating factors of HIF-1alpha, SOD, cell cycle parameters of pMI, proliferation factors of Ki67, EGFR, cerbB2, COX-2, cycle regulation proteins p53, p21, apoptosis regulation proteins Bcl2 and Bax and so on. Especially, the variety of these radiation biological factors is important for the selection of an effective treatment method for each patient to maximize the treatment benefit.

Current imaging techniques focus on evaluating the anatomical structure of blood vessel wall and atherosclerotic plaque. These techniques fail to evaluate the biological processes which take place in the vessel wall and inside the plaque. Novel imaging techniques like optical imaging can evaluate the biological and cellular processes inside the plaque and provide information which can be vital for better patient risk stratification. This review highlights the various optical imaging techniques and their application in assessing biological processes in atherosclerosis.

Molecular imaging is a new and evolving field that employs a targeted approach to noninvasively assess biologic processes in vivo. By assessing key elements in specific cellular processes prior to irreversible end-organ damage, molecular tools will allow for earlier detection and intervention, improving management and outcomes associated with cardiovascular diseases. The goal of those working to expand this field is not just to provide diagnostic and prognostic information, but rather to guide an individual's pharmacological, cell-based, or genetic therapeutic regimen. This article will review molecular imaging tools in the context of our current understanding of biological processes of the myocardium, including angiogenesis, ventricular remodeling, inflammation, and apoptosis. The focus will be on radiotracer-based molecular imaging modalities with an emphasis on clinical application. Though this field is still in its infancy and may not be fully ready for widespread use, molecular imaging of myocardial biology has begun to show promise of clinical utility in acute and chronic ischemia, acute myocardial infarction, congestive heart failure, as well as in more global inflammatory and immune-mediated responses in the heart-like myocarditis and allogeneic cardiac transplant rejection. With continued research and development, molecular imaging promises to be an important tool for the optimization of cardiovascular care.

In this report we summarize the progress made in the past several years on the use of luminescent QDs to probe biological processes at the single molecule level. We start by providing a quick overview of the basic properties of semiconductor nanocrystals, including synthetic routes, surface-functionalization strategies, along with the main attributes of QDs that are of direct relevance to single molecule studies based on fluorescence detection. We then detail some valuable insights into specific biological processes gained using single QDs. These include progress made in probing biomolecular interactions, tracking of protein receptors both in vitro and in live cells, and single particle resonance energy transfer. We will also discuss the advantages offered and limitations encountered by single QD fluorescence as an investigative tool in biology.

A broad array of nanomaterials is available for use as contrast agents for molecular imaging and drug delivery. Due to the lack of endogenous background signal in vivo and the high NMR sensitivity of the (19)F atom, liquid perfluorocarbon nanoemulsions make ideal agents for cellular and magnetic resonance molecular imaging. The perfluorocarbon core material is surrounded by a lipid monolayer which can be functionalized with a variety of agents including targeting ligands, imaging agents and drugs either individually or in combination. Multiple copies of targeting ligands (approximately 20-40 monoclonal antibodies or 200-400 small molecule ligands) serve to enhance avidity through multivalent interactions while the composition of the particle's perfluorocarbon core results in high local concentrations of (19)F. Additionally, lipophilic drugs contained within molecularly targeted nanoemulsions can result in contact facilitated drug delivery to target cells. Ultimately, the dual use of perfluorocarbon nanoparticles for both site targeted drug delivery and molecular imaging may provide both imaging of disease states as well as conclusive evidence that drug delivery is localized to the area of interest. This review will focus on liquid perfluorocarbon nanoparticles as (19)F molecular imaging agents and for targeted drug delivery in cancer and cardiovascular disease.

The successful management of prostate cancer requires early detection, appropriate risk assessment, and optimum treatment. An unmet goal of prostate cancer imaging is to differentiate indolent from aggressive tumors, as treatment may vary for different grades of the disease. Different modalities have been tested to diagnose, stage, and monitor prostate cancer during therapy. This review briefly describes the key clinical issues in prostate cancer imaging and therapy and summarizes the various new imaging modalities and agents in use and on the horizon.

The practice of clinical cardiology employs many imaging techniques for diagnosis, risk stratification and therapeutic monitoring. These imaging modalities largely provide anatomical or structural information, and only indirectly reflect underlying molecular events. Molecular imaging techniques report on entities or processes that can be defined at the molecular, as opposed to the anatomical, level. For example, molecular imaging can reveal the expression or activity of a specific protein, the fate or localization of a biomolecule, or the activity of a biological pathway. This Review highlights key processes and molecular targets that are currently being investigated experimentally by molecular imaging probes in vivo. Collectively, these targets have an important role in the development of atherosclerosis and acute plaque rupture, as well as in myocardial disease. Molecular imaging technology is now progressing towards clinical application in humans and has the potential to guide diagnosis, risk assessment and treatment response. Imaging-based surrogate end points could speed the development of new drugs, particularly those with novel mechanisms of action. More broadly, by noninvasively reporting on molecular processes in vivo, molecular imaging can reveal how specific proteins or pathways function in their native context, thus contributing to a systems-level understanding of cardiovascular disease biology.

The intention of this review is to provide information about the rapidly evolving field of molecular imaging and its potential impact on the clinical practice of nuclear medicine. On completing this article the reader should be able to define molecular imaging, describe the ways in which molecular imaging can be used, identify some of the biologic processes that can be targeted with molecular imaging agents, and list the modalities that can be used for molecular imaging, along with the strengths and weaknesses of each.

A promising role of cellular therapies in cancer treatment is reflected by the constantly growing number of clinical trials with adoptively transferred cells. Direct and indirect cell labeling for the nuclear imaging of transferred cells has been proven reliable for imaging adoptive cellular therapies. Both methods show their advantages and limitations. Direct labeling is a relatively easy, inexpensive, and well-established methodology. Indirect labeling using a reporter gene imaging paradigm allows for reliable, stable, and harmless visualization of cellular trafficking, persistence, proliferation, and function at the target site. It is expected that new human-derived reporter genes will be rapidly translated into clinical applications that require repetitive imaging for the effective monitoring of various genetic and cellular therapies.

Between 2004 and 2008, the US National Institutes of Health Molecular Libraries and Imaging initiative pilot phase funded 10 high-throughput screening centers, resulting in the deposition of 691 assays into PubChem and the nomination of 64 chemical probes. We crowdsourced the Molecular Libraries and Imaging initiative output to 11 experts, who expressed medium or high levels of confidence in 48 of these 64 probes.