Jorge Ripoll

Bio: Jorge Ripoll is an academic researcher from Charles III University of Madrid. The author has contributed to research in topics: Optical tomography & Diffuse optical imaging. The author has an hindex of 39, co-authored 182 publications receiving 7496 citations. Previous affiliations of Jorge Ripoll include Harvard University & Carlos III Health Institute.

Looking and listening to light: the evolution of whole-body photonic imaging.

Abstract: Optical imaging of live animals has grown into an important tool in biomedical research as advances in photonic technology and reporter strategies have led to widespread exploration of biological processes in vivo. Although much attention has been paid to microscopy, macroscopic imaging has allowed small-animal imaging with larger fields of view (from several millimeters to several centimeters depending on implementation). Photographic methods have been the mainstay for fluorescence and bioluminescence macroscopy in whole animals, but emphasis is shifting to photonic methods that use tomographic principles to noninvasively image optical contrast at depths of several millimeters to centimeters with high sensitivity and sub-millimeter to millimeter resolution. Recent theoretical and instrumentation advances allow the use of large data sets and multiple projections and offer practical systems for quantitative, three-dimensional whole-body images. For photonic imaging to fully realize its potential, however, further progress will be needed in refining optical inversion methods and data acquisition techniques.

A submillimeter resolution fluorescence molecular imaging system for small animal imaging.

Abstract: Most current imagingsystems developed for tomographic investigations of intact tissues using diffuse photons suffer from a limited number of sources and detectors. In this paper we describe the construction and evaluation of a large dataset, low noise tomographic system for fluorescenceimaging in small animals. The system consists of a parallel plate-imaging chamber and a lens coupled CCD camera, which enables conventional planar imaging as well as fluorescencetomography. The planar imaging data are used to guide the acquisition of a Fluorescence Molecular Tomography (FMT) dataset containing more than 10 6 measurements, and to superimpose anatomical features with tomographic results for improved visual representation. Experimental measurements exhibited good agreement with the diffusion theory models used to predict light propagation within the chamber. Tests of the instrument’s capacity to quantitatively reconstruct fluorochrome distributions in three dimensions showed less than 5% errors between actual fluorochrome concentrations and FMT findings, and suggested a detection threshold of approximately 100 femptomoles for small localized objects. Experiments to assess the instrument’s spatial resolution demonstrated the ability of the system to resolve objects placed at clear distances of less than 1 mm. This is a significant resolution increase over previously developed systems for animal imaging, and is primarily due to the large dataset employed and the use of inversion methods. Finally, the in vivoimaging capacity is showcased. It is expected that the large dataset collected can enable superior imaging of molecular probes in vivo and improve quantification of fluorescence signatures.

Visualization of antitumor treatment by means of fluorescence molecular tomography with an annexin V–Cy5.5 conjugate

Abstract: In vivo imaging of treatment responses at the molecular level could have a significant impact on the speed of drug discovery and ultimately lead to personalized medicine. Strong interest has been shown in developing quantitative fluorescence-based technologies with good molecular specificity and sensitivity for noninvasive 3D imaging through tissues and whole animals. We show herein that tumor response to chemotherapy can be accurately resolved by fluorescence molecular tomography (FMT) with a phosphatidylserine-sensing fluorescent probe based on modified annexins. We observed at least a 10-fold increase of fluorochrome concentration in cyclophosphamide-sensitive tumors and a 7-fold increase of resistant tumors compared with control studies. FMT is an optical imaging technique developed to overcome limitations of commonly used planar illumination methods and demonstrates higher quantification accuracy validated by histology. It is further shown that a 3-fold variation in background absorption heterogeneity may yield 100% errors in planar imaging but only 20% error in FMT, thus confirming tomographic imaging as a preferred tool for quantitative investigations of fluorescent probes in tissues. Tomographic approaches are found essential for small-animal optical imaging and are potentially well suited for clinical drug development and monitoring.

In vivo continuous-wave optical breast imaging enhanced with Indocyanine Green

Abstract: We investigate the uptake of a nontargeted contrast agent by breast tumors using a continuous wave diffuse optical tomography apparatus. The instrument operates in the near-infrared spectral window and employs 16 sources and 16 detectors to collect light in parallel on the surface of the tumor-bearing breast (coronal geometry). In our protocol an extrinsic contrast agent, Indocyanine Green (ICG), was injected by bolus. Three clinical scenarios with three different pathologies were investigated. A two-compartment model was used to analyze the pharmacokinetics of ICG and preprocess the data, and diffuse optical tomography was used for imaging. Localization and delineation of the tumor was achieved in good agreement with a priori information. Moreover, different dynamical features were observed for differing pathologies. The malignant cases exhibited slower rate constants (uptake and outflow) compared to healthy tissue. These results provide further evidence that in vivo pharmacokinetics of ICG in breast tumors may be a useful diagnostic tool for differentiation of benign and malignant pathologies.

Optimisation of bioluminescent reporters for use with mycobacteria.

Abstract: BACKGROUND: Mycobacterium tuberculosis, the causative agent of tuberculosis, still represents a major public health threat in many countries. Bioluminescence, the production of light by luciferase-catalyzed reactions, is a versatile reporter technology with multiple applications both in vitro and in vivo. In vivo bioluminescence imaging (BLI) represents one of its most outstanding uses by allowing the non-invasive localization of luciferase-expressing cells within a live animal. Despite the extensive use of luminescent reporters in mycobacteria, the resultant luminescent strains have not been fully applied to BLI. METHODOLOGY/PRINCIPAL FINDINGS: One of the main obstacles to the use of bioluminescence for in vivo imaging is the achievement of reporter protein expression levels high enough to obtain a signal that can be detected externally. Therefore, as a first step in the application of this technology to the study of mycobacterial infection in vivo, we have optimised the use of firefly, Gaussia and bacterial luciferases in mycobacteria using a combination of vectors, promoters, and codon-optimised genes. We report for the first time the functional expression of the whole bacterial lux operon in Mycobacterium tuberculosis and M. smegmatis thus allowing the development of auto-luminescent mycobacteria. We demonstrate that the Gaussia luciferase is secreted from bacterial cells and that this secretion does not require a signal sequence. Finally we prove that the signal produced by recombinant mycobacteria expressing either the firefly or bacterial luciferases can be non-invasively detected in the lungs of infected mice by bioluminescence imaging. CONCLUSIONS/SIGNIFICANCE: While much work remains to be done, the finding that both firefly and bacterial luciferases can be detected non-invasively in live mice is an important first step to using these reporters to study the pathogenesis of M. tuberculosis and other mycobacterial species in vivo. Furthermore, the development of auto-luminescent mycobacteria has enormous ramifications for high throughput mycobacterial drug screening assays which are currently carried out either in a destructive manner using LuxAB or the firefly luciferase.

The fluorescent toolbox for assessing protein location and function

Abstract: Advances in molecular biology, organic chemistry, and materials science have recently created several new classes of fluorescent probes for imaging in cell biology. Here we review the characteristic benefits and limitations of fluorescent probes to study proteins. The focus is on protein detection in live versus fixed cells: determination of protein expression, localization, activity state, and the possibility for combination of fluorescent light microscopy with electron microscopy. Small organic fluorescent dyes, nanocrystals ("quantum dots"), autofluorescent proteins, small genetic encoded tags that can be complexed with fluorochromes, and combinations of these probes are highlighted.

Imaging in the era of molecular oncology

Abstract: New technologies for imaging molecules, particularly optical technologies, are increasingly being used to understand the complexity, diversity and in vivo behaviour of cancers. 'Omic' approaches are providing comprehensive 'snapshots' of biological indicators, or biomarkers, of cancer, but imaging can take this information a step further, showing the activity of these markers in vivo and how their location changes over time. Advances in experimental and clinical imaging are likely to improve how cancer is understood at a systems level and, ultimately, should enable doctors not only to locate tumours but also to assess the activity of the biological processes within these tumours and to provide 'on the spot' treatment.

In vivo tumor targeting and spectroscopic detection with surface-enhanced Raman nanoparticle tags

Abstract: Nanostructures, methods of preparing nanostructures, methods of detecting targets in subjects, and methods of treating diseases in subjects, are disclosed An embodiment, among others, of the nanostructure includes a metallic gold surface- enhanced Raman scattering nanoparticle, a Raman reporter and a protection structure The protection structure may include a thiol-polyethylene glycol to which may be attached a target-specific probe

New Strategies for Fluorescent Probe Design in Medical Diagnostic Imaging

Abstract: In vivo medical imaging has made great progress due to advances in the engineering of imaging devices and developments in the chemistry of imaging probes Several modalities have been utilized for medical imaging, including X-ray radiography and computed tomography (x-ray CT), radionuclide imaging using single photons and positrons, magnetic resonance imaging (MRI), ultrasonography (US), and optical imaging In order to extract more information from imaging, “contrast agents” have been employed For example, organic iodine compounds have been used in X-ray radiography and computed tomography, superparamagnetic or paramagnetic metals have been used in MRI, and microbubbles have been used in ultrasonography Most of these, however, are non-targeted reagents Molecular imaging is widely considered the future for medical imaging Molecular imaging has been defined as the in vivo characterization and measurement of biologic process at the cellular and molecular level1, or more broadly as a technique to directly or indirectly monitor and record the spatio-temporal distribution of molecular or cellular processes for biochemical, biologic, diagnostic, or therapeutic application2 Molecular imaging is the logical next step in the evolution of medical imaging after anatomic imaging (eg x-rays) and functional imaging (eg MRI) In order to attain truly targeted imaging of specific molecules which exist in relatively low concentrations in living tissues, the imaging techniques must be highly sensitive Although MRI, US, and x-ray CT are often listed as molecular imaging modalities, in truth, radionuclide and optical imaging are the most practical modalities, for molecular imaging, because of their sensitivity and the specificity for target detection Radionuclide imaging, including gamma scintigraphy and positron emission tomography (PET), are highly sensitive, quantitative, and offer the potential for whole body scanning However, radionuclide imaging methods have the disadvantages of poor spatial and temporal resolution3 Additionally, they require radioactive compounds which have an intrinsically limited half life, and which expose the patient and practitioner to ionizing radiation and are therefore subject to a variety of stringent safety regulations which limit their repeated use4 Optical imaging, on the other hand, has comparable sensitivity to radionuclide imaging, and can be “targeted” if the emitting fluorophore is conjugated to a targeting ligand3 Optical imaging, by virtue of being “switchable”, can result in very high target to background ratios “Switchable” or activatable optical probes are unique in the field of molecular imaging since these agents can be turned on in specific environments but otherwise remain undetectable This improves the achievable target to background ratios, enabling the detection of small tumors against a dark background5,6 This advantage must be balanced against the lack of quantitation with optical imaging due to unpredictable light scattering and absorption, especially when the object of interest is deep within the tissue Visualization through the skin is limited to superficial tissues such as the breast7-9 or lymph nodes10,11 The fluorescence signal from the bright GFP-expressing tumors can be seen in the deep organ only in the nude mice 12,13 However, optical molecular imaging can also be employed during endoscopy14 or surgery 15,16