Hot Topics in Molecular Imaging: imaging of nano-objects
4-8 February
Les Houches , France

Organisers:

Bertrand Tavitian: CEA, France
Frédéric Ducongé: CEA, France
Andreas Jacobs: Cologne, Germany
Patrick Cumi: Evry, France
Eva Pebay-Peroula: Grenoble, France
Silvio Aime: Turin, Italy

Draft Report

Summary

Molecular imaging is a new science with already a strong influence on medicine and biology, leading the way in exploiting molecular, biological and genetic information to develop precise, precocious and predictive diagnostic methods. These methods are increasingly precious for the follow-up and the evaluation of new treatments of many pathological states.

Molecular imaging is therefore asserting itself as an original means of discovery, and opens new avenues to address unexplored questions. This is what TOPIM, Hot Topics in Molecular Imaging, is all about: capture these assertions by providing an instant picture of the field, and foster new ones through the discussions between participants.

Naturally, it would be an incommensurable task to cover all aspects of the burgeoning
molecular imaging field in just a few days, and there are already annual meetings which aim at doing that. As a consequence, rather than proposing a catalogue of recent releases in molecular imaging, the ESMI (European Society for Molecular Imaging) council decided to concentrate on one aspect at the forefront of the discipline, a hot topic. TOPIM is an annual rendezvous concentrating on one domain of application or technique of molecular imaging, chosen according to its pertinence and timeliness.

Medical imaging has advanced from a marginal role in healthcare to become an essential tool of diagnostics over the last 25 years. Originally, imaging techniques could only detect changes in the appearance of tissues when the symptoms were relatively advanced. Later, contrast agents were introduced to more easily identify and map the locus of disease. Today, through the application of nanotechnology, both imaging tools and marker/contrast agents are being dramatically refined towards the end goals of detecting disease as early as possible, eventually at the level of a single cell, and monitoring the effectiveness of therapy. The convergence of nanotechnology and medical imaging opens the doors to a revolution in molecular imaging (also called nano-imaging) in the foreseeable future, leading to the detection of a single molecule or a single cell in a complex biological environment.

Continued research into nano-sciences combined with imaging techniques offers the
overview of essential developments in Nanomedicine, and involves teams of scientists from across ‘conventional’ disciplines, such as physics, chemistry, surgery and mathematics, as well as those from the ‘new’ fields of genomics, proteomics, metabolomics, pharmacokinetic modeling and microscope design. It seamed therefore valuable that TOPIM’08 adopt a multidisciplinary approach by bringing together experts from different disciplines in order to promote essential exchanges between these fields. The organizers (Bertrand Tavitian, Andreas Jacobs, Patrick Curmi, Eva Pebay-Peyroula, Silvio Aime and Frédéric Ducongé) have been most fortunate to attract a panel of prestigious speakers, all at the fore point of research in their discipline.

Scientific Content
Throughout the workshop, the main concerns regarding the use of nanoparticles during drug targeting, delivery and release rose from issues related to improvement of their stability in the biological environment, to mediation of the bio-distribution of active compounds, to improvement of drug loading, targeting, transport, release and interaction with biological barriers. The cytotoxicity of nanoparticles or their degradation products remains a major problem and improvements in biocompatibility obviously are a main concern of future research. Various alternatives to bypass these problems were discussed.

Radiochemistry: The use of fluorine-18 labeling for PET imaging of macromolecule
and nanoobject was presented. (Dolle).

Drug delivery: Toward the “magic bullet” using liposome (lipidic nanoparticle) which
can offer the possibility to visualized the drug targeting and drug releasing phases, and
also provides information on the microenvironnement of the diseased region (Aime).
Dendrimer nanoplatform can be used as a multimodal carrier as it is easily soluble, tunable in size and as it can be functionalized at the same time with fluorescent dyes,
anti-cancer drugs, radioisotopes… (Jones).

Quantum Dots (QDs): Chemical modification of the QD coating to improve their
aqueous solubility and their in vivo biodistribution (Dubertret and Daou). QD used as
nanotools to study cellular mechanism not only at cellular but also at molecular level
which could be helpful in medical application to improve drug delivery system (Dahan).
Continuous real time tracking of QDs functionalized with antibodies, with a high resolution in vivo 3D microscopic system. It was shown to be efficient for the study of
delivery processes in blood and cells and future drug delivery (Ohuchi and Kawai)

Fluorescent proteins: Improved sensitivity and specificity for super-resolution imaging
using photoswitchable proteins (Bock); Use of green fluorescent proteins (GFP) that
can be tuned to change their color for applications in embryogenesis and cell-division
(Roecker); Control of fluorescence under pressure of protein surface interaction
(Fuchs)

Contrast agent: Lipid based emulsion for encapsulation of iodine allowing a long
circulating blood time. Use for spectral CT and SPECT (de Vries). Use of iron oxide
nanoparticle (10 nm) coated with PEG or Gadolinium assemblies for MRI contrast
agents (Bégin-Colin and Hengerer). Some of them are already in clinical development.
Gadolinium contrast agent functionalized with a collagen adhesion protein: use for
tissue maturation monitoring and remodeling (Sanders). Gold nanorods coupled with
an antibody were used as contrast agent for opto-acoustic detection of cancer cells and showed enhanced sensitivity (Greish)

Oxide Nanoparticles (NPs): Iron oxide NPs can be used as contrast agent for MRI
(Bégin-Colin) and find applications for the macrophage and blood pool imaging.
Actually the efficiency, the biodistribution, the stability, the metabolism of these
superparamagnetic NPs is being studied (Port) as it could be used for molecular
imaging and cell labeling. It would therefore allow, for example, magnetic manipulation
of cells (Gazeau). Another use of these NPs would be as colloidal heating mediators
for cancer therapy as they can generate heat when subjected to a high frequency
magnetic field (Lévy). Finally, these NPs can be functionalized with different molecules
for in vivo imaging (Cy5.5) and targeting (siRNA, gfp/agfp, therapeutic gene,…) at the
same time.

Luminescent NPs: These rare-earth oxide nanoparticles can be excited before
injection, and their in vivo distribution can be followed in real-time for more than 1 h
without the need for any external illumination source. Chemical modification of the
nanoparticles surface led to lung or liver targeting or to long-lasting blood circulation (le Masne de Chermont). They could also be used for local detection of H2O2 or for
dynamics studies of toxins coupled to these NPs (Gacoin).

Silica NPs: Dye-doped NPs are composed of a silver core covered with a passive shell
and a silica one doped with fluorophores. Therefore, as the metal is going to enhance
the fluorescence of the dye, these systems could be used as chemosensors in the way
that it is possible to control photoinduced energy transfer (Prodi). By labeling silica NPs
it is then possible to use them for life sciences applications and nanomedecine. For
example, by grafting a pH sensitive dye on these NPs it allows to study the pH variation
inside cells (Wiesner).

Zeolite: These silica-based nanocontainers are made of hundreds of parallel aligned channel and can be used to encapsulate fluorophores or radioactive element. Hence,
they can be used as multifunctional systems for in vitro MRI imaging (de Cola). By
incorporating rare-earth complex they can be used as MRI contrast agents too
(Tsotsalas).

Carbon NPs: Different kinds of carbon NPs have been presented like carbon dots (Sun), carbon nanotubes (Doris and Helm), fullerenes (Helm) and diamond nanocrystals (Jelezko). The goal each time is to functionalize them for in vivo applications with either PEG, streptavidin or other biomolecules or MRI contrast agent like gadolinium in order to obtain biocompatible and non-toxic nano-carriers.

Advanced functionalization of NPs for the delivery of therapeutic peptide/proteins: NPs
combined with cyanine dye, RAFT with a multivalent presentation of RGD and PEG (Dufort).

Use of fluorescent and radioactive organometallic complex probes bearing a pendant
arm for further coupling to bioactive vectors: in vitro and in vivo imaging applications
(Paulo).

Use of a polymer that can polymerize and mimic a membrane. The color change of the
polymer under irradiation give indications on the membrane processes in living cells
(Jelinek).

Use of lipidic NPs labeled with Gd3+ for MRI detection. These lipidic NPs can also be
made to contain QDs, RGD or ligands to couple different kind of detection and imaging
(Nicolay).

Sensitive methods for detection and assessment of optical properties of nano-particles:
use of an interferometric microscopy method for detection of nonfluorescent
nanoparticles at the single emitter level (Kukura); STED microscopy ensures that the
measured signal stems from a region of the sample that is much smaller than the limit
imposed by the diffraction of light (Eggeling).

In-depth, non-invasive techniques to investigate biological systems: micro-axial
tomography combined to a new algorithm to increase optical resolution (Birk); Depth
resolution limit of fluorescence diffuse optical tomography (Boffety).

Explanation and discussion upon molecule (fluorophores, QD) fluorescence life time
fluctuations in disordered and structured environments (Carminati) trough plasmonic
slabs (Vandenbem).


Assessment of the results & contribution to the future direction of the field
In past decades, great progress has been made by physicists and chemists in order to
create a panel of new nano-objects with original physico-chemical properties (quantum dots, carbon nanotubes, polymeric nano-sized lipidic rings, gold and diamond nanoparticles…). Formal definitions of nanotechnological devices typically feature the requirements that the device itself is man-made and within the 1-100 nm range. Such nanodevices bring new
important possibilities both for high contrast agents or therapeutic payloads. Nano-objects are already extensively exploited in vitro to achieve fundamental understanding of biological processes or disease diagnostic. Given the importance that nano-objects are likely to take in molecular medicine, it appears timely to combine the expertise in the analysis of distribution of large objects in vivo with the expertise in the fabrication and functionalization of these objects. Since the 1990s, progress made by physicists and chemists has provided a wealth of nanoscaled tools predicted to have a large impact on life sciences and particularly on cancer treatment.

In medicine, nanodevices offer important new possibilities, both for high contrast agents and therapeutic payloads. In vivo clinical applications of nano-objects are just beginning but their potential seems to be high and many efforts are provided to build and functionalized these nano-objects in order to achieve long circulation time, good
biocompatibility and low immunogenicity, efficient penetration of physiological barriers,
selective targeting, external activation or self regulating drug release... However, despite the appealing applications of nanotechnologies their use in vivo raises the question of the precise distribution and elimination pathways, as well as the toxicity associated with nano-scaled objects. Among all the interesting discussions engaged during the different lectures of this workshop, the metabolism of these promising nano-objects appeared to be one of the most important point of this new research area that remain to be elucidated.

To address limitations of in vitro assays, in vivo imaging of vertebrates has emerged as
a powerful tool used in virtually all forms of modern biomedical research and drug discovery. Particularly, the evolution or development of new methods, primarily based on photonic technologies, which are well suited for small animal research, significantly accelerate biomedical discovery. Theses imaging techniques are particularly efficient to assess noninvasively the pharmacokinetics of drug candidates and are increasingly applied to explore in living animals the distribution of nanomolecules and nanovectors.

Programme

Monday, 4th February

09:00 -09:45 INTRODUCTION : Bertrand TAVITIAN, President ESMI & Patrick BRESSLER, Representative ESF

Fluorine-18 Chemistry: from FDG to the Labelling of Macromolecules and Nanoobjects
Frederic DOLLE , Orsay

09:45 -10:30 Imaging-guided Drug Delivery
Silvio AIME, Torino

10:50 -11:35 Quantum Dots for in vivo imaging
Benoît DUBERTRET, Paris

11:35 -11:50 Presentation submitted abstract: Photoswitchable fluorescent Proteins Tools for Far-Field Microscopy at the Nanoscale
Hannes BOCK, Göttingen

11:50 -12:05 Presentation submitted abstract: Iodinated Emulsion for multimodality Imaging using spectral CT and SPECT
Anke DE VRIES, Eindhoven

12:05-12:20 Presentation submitted abstract: Use of Optical Imaging for Detection, medical Imaging and Treatment of Cancer
Sandrine DUFORT, Grenoble

17:00-17:45 Clinical Application of Iron Oxide Nanoparticles in MRI Imaging and Research Perspectives
Marc PORT, Roissy

17:45-18:30 Investigating cellular Processes at the single Molecule Level using Semiconductor Nanoscrystals
Maxime DAHAN, Paris

18:45-19:30 Luminescent Silica Nanoparticles: Organization and Versatility towards
Brightness
Luca PRODI, Bologna

Tuesday, 5th February

09:00-09:45 Photoluminescent Carbon Dots and Bioimaging Applications
Ya-Ping SUN, South Carolina

09:45 -10:30 Core-Shell Silica Nanoparticles as Fluorescent Labels for Nanobiotechnology and Nanomedicine: C Dots
Ulrich WIESNER, New York

10:50 -11:35 Fluorescent Proteins and fundamental Aspects on Photophysics
Carlheinz ROECKER, Ulm

11:35 -11:50 Presentation submitted abstract: Optical Properties of fluorescent Proteins in controlled Environments
Jochen FUCHS, Ulm

11:50 -12:05 Presentation submitted abstract: Dendronised Magnetite Nanoparticles as
Contrast Agent for MRI
Sylvie BEGIN-COLIN, Strasbourg

12:05-12:20 Presentation submitted abstract: Micro-axial Tomography
Udo BIRK, Heraklion

17:00-17:45 Optical Detection of single nonfluorescent Nanoparticles and Demonstration of a long-distance nanometric Ruler
Philipp KUKURA, Zurich

17:45-18:30 Cell Labelling with magnetic Nanoparticles: Mechanisms, Biocompatibility, MRI Cell Imaging and magnetic Manipulations
Florence GAZEAU, Paris

18:45-19:30 STED Microscopy
Christian EGGELING, Göttingen

Wednesday, 6th February

09:00-09:45 Carbon Nanotubes: Functionalization and selected Examples of Applications
Eric DORIS, Saclay

09:45 -10:30 The influence of the chemical Coating on the Bio-distribution of
Quantum Dots in vivo
Toufic DAOU, Grenoble

10:50 -11:35 Nano-objects, Properties, Assemblies and Applications
Luisa DE COLA, Münster

11:35 -11:50 Presentation submitted abstract: Zeolite L Nanocrystals for Imaging Applications
Manuel TSOTSALAS, Münster

11:50 -12:05 Presentation submitted abstract: Determination of the Depth Resolution Limit of Fluorescence diffuse optical Tomography
Matthieu BOFFETY, Châtenay-Malabry

12:05-12:20 Presentation submitted abstract: Novel Organometallic Complexes for multimodal Imaging
António PAULO, Sacavém

17:00-17:45 Single Molecule Fluorescence in disordered nanoscopic Environments
Rémi CARMINATI, Paris

17:45-18:30 Magnetic Resonance Imaging of single Spins in Diamond Nanocrystals under ambient Conditions
Fedor JELEZKO, Stuttgart

18:45-19:30 Targeted lipid-based Nano-particles for multimodal Biomarker Imaging
Klaas NICOLAY, Eindhoven

Thursday, 7th February

09:00-09:45 Novel Imaging Techniques with functional Nano-objects for Cancer Diagnosis
Noriaki OHUCHI, Sendai

09:45 -10:30 Luminescent Oxide Nanoparticles: Synthesis, Properties and Applications
Thierry GACOIN, Palaiseau

10:50 -11:35 Shape specific Nanoparticles as Contrast Agents for opto-acoustic Detection
Jean-François GREISCH, Liège

11:35 -11:50 Presentation submitted abstract: Controlling single Molecule Fluorescence
through plasmonic Slabs
Cédric VANDENBEM, Paris

11:50 -12:05 Presentation submitted abstract: In vivo Imaging of vascular Permeability using Nano-objects in Mice Tumor
Masaaki KAWAI, Sendai

12:05-12:20 Presentation submitted abstract: The Size of Magnetic Nanoparticle finely tunes their heating Power under a high Frequency alternating Magnetic Field
Michael LEVY, Paris

17:00-17:45 Nanoscale mMRI Contrast Agents
Arne HENGERER, Erlangen

17:45-18:30 Persistent Luminescence Nanoparticles (PLNs): a new imaging tool for biologists?
Quentin LE MASNE DE CHERMONT, Paris

18:45-19:30 Visualizing Dynamics of Cell Signaling
Ralf SCHMAUDER, Lausanne

Friday, 8th February

09:00-09:45 Fullerens and Carbon Nanotubes loaded with Gd high Relaxivity MRI Agents
Lothar HELM, Lausanne

09:45 -10:30 Chromatic Polymer Nano-patches for Imaging Membrane Processes in living Cells
Raz JELINEK, Beer Sheva

10:50 -11:35 Dendrimer Nanoplatforms for effective Tumor Targeting
Ella JONES, San Francisco

11:35 -11:50 Presentation submitted abstract: Paramagnetic Collagen binding Contrast Agents
H.M.H.F. SANDERS, Eindhoven

CONCLUSION : Bertrand TAVITIAN, President ESMI