Piero A. Salvadori

Boron analysis and boron imaging in biological materials for Boron Neutron Capture Therapy (BNCT)

Boron Neutron Capture Therapy (BNCT) is based on the ability of the stable isotope 10B to capture neutrons, which leads to a nuclear reaction producing an alpha- and a 7Li-particle, both having a high biological effectiveness and a very short range in tissue, being limited to approximately one cell diameter. This opens the possibility for a highly selective cancer therapy. BNCT strongly depends on the selective uptake of 10B in tumor cells and on its distribution inside the cells. The chemical properties of boron and the need to discriminate different isotopes make the investigation of the concentration and distribution of 10B a challenging task. The most advanced techniques to measure and image boron are described, both invasive and non-invasive. The most promising approach for further investigation will be the complementary use of the different techniques to obtain the information that is mandatory for the future of this innovative treatment modality.

Fatty Acid Metabolism in the Liver, Measured by Positron Emission Tomography, Is Increased in Obese Individuals

BACKGROUND & AIMS Hepatic lipotoxicity results from and contributes to obesity-related disorders. It is a challenge to study human metabolism of fatty acids (FAs) in the liver. We combined (11)C-palmitate imaging by positron emission tomography (PET) with compartmental modeling to determine rates of hepatic FA uptake, oxidation, and storage, as well as triglyceride release in pigs and human beings. METHODS Anesthetized pigs underwent (11)C-palmitate PET imaging during fasting (n = 3) or euglycemic hyperinsulinemia (n = 3). Metabolic products of FAs were measured in arterial, portal, and hepatic venous blood. The imaging methodology then was tested in 15 human subjects (8 obese subjects); plasma (11)C-palmitate kinetic analyses were used to quantify systemic and visceral lipolysis. RESULTS In pigs, PET-derived and corresponding measured FA fluxes (FA uptake, esterification, and triglyceride FA release) did not differ and were correlated with each other. In human beings, obese subjects had increased hepatic FA oxidation compared with controls (mean +/- standard error of the mean, 0.16 +/- 0.01 vs 0.08 +/- 0.01 micromol/min/mL; P = .0007); FA uptake and esterification rates did not differ between obese subjects and controls. Liver FA oxidation correlated with plasma insulin levels (r = 0.61, P = .016), adipose tissue (r = 0.58, P = .024), and systemic insulin resistance (r = 0.62, P = .015). Hepatic FA esterification correlated with the systemic release of FA into plasma (r = 0.71, P = .003). CONCLUSIONS PET imaging can be used to measure FA metabolism in the liver. By using this technology, we found that obese individuals have increased hepatic oxidation of FA, in the context of adipose tissue insulin resistance, and increased FA flux from visceral fat. FA flux from visceral fat is proportional with the mass of the corresponding depot.

The makers of the Protoaurignacian and implications for Neandertal extinction

Cultural prehistory in southern Europe The Protoaurignacian culture appeared in the southern European archeological record around 42,000 years ago and was characterized by artefacts including personal ornaments and bladelets. Archaeologists have debated whether it was ancestral Homo sapiens or Neandertals who made these tools and ornaments. Benazzi et al. analyzed dental remains from two Protoaurignacian sites in Italy and confirm that they were H. sapiens. The arrival of this culture may have led to the demise of Neandertals in these areas (see the Perspective by Conard et al.). Science, this issue p. 793; see also p. 754 The Protoaurignacian culture in southern Europe involved anatomically modern humans and overlapped in time with the last Neandertals. [Also see Perspective by Conard] The Protoaurignacian culture is pivotal to the debate about the timing of the arrival of modern humans in western Europe and the demise of Neandertals. However, which group is responsible for this culture remains uncertain. We investigated dental remains associated with the Protoaurignacian. The lower deciduous incisor from Riparo Bombrini is modern human, based on its morphology. The upper deciduous incisor from Grotta di Fumane contains ancient mitochondrial DNA of a modern human type. These teeth are the oldest human remains in an Aurignacian-related archaeological context, confirming that by 41,000 calendar years before the present, modern humans bearing Protoaurignacian culture spread into southern Europe. Because the last Neandertals date to 41,030 to 39,260 calendar years before the present, we suggest that the Protoaurignacian triggered the demise of Neandertals in this area.

Microfluidic approach for fast labeling optimization and dose-on-demand implementation

INTRODUCTION The diffusion of PET as a pivotal molecular imaging modality has emphasized the need for new positron-emitting radiotracers to be used in diagnostic applications and research. Microfluidic represents an innovative approach, owing to its potential to increase radiochemical productivity in terms of yields, time reduction, precursor consumption and flexible experimental planning. METHODS We focused on fluorine-18 labeling and used a microfluidic platform to perform sequential reactions, by using the same batch of (18)F-labeling solution on one or more substrates, during the same experimental session. A solid-phase extraction (SPE) workup procedure was also implemented in the system to provide a repeatable purification step. RESULTS We were able to quickly optimize the conditions for labeling of ethyl and propyl ditosylate and of a new cannabinoid type 2 (CB2) receptor agonist, CB41. In all substrates, we obtained good incorporation yields (60% to 85%) in short (<90 s) reaction times. Single dosages of the CB2 ligand were sequentially prepared, upon request, in satisfactory quantities and purity for small animal PET scanning. CONCLUSION This work demonstrates the usefulness of a microfluidic-based system for a rapid optimization of temperature, flow rate of reactants and their relative ratio in the labeling of different precursors by using the same (18)F-fluoride batch. This approach was used to obtain in sequence several injectable doses of a novel CB2 ligand, thus providing the proof of principle that microfluidic systems permit a dose-on-demand production of new radiotracers.

Microfluidics in radiopharmaceutical chemistry

The increased demand for molecular imaging tracers useful in assessing and monitoring diseases has stimulated research towards more efficient and flexible radiosynthetic routes, including newer technologies. The traditional vessel-based approach suffers from limitations concerning flexibility, reagent mass needed, hardware requirements, large number of connections and valves, repetitive cleaning procedures and overall big footprint to be shielded from radiation. For these reasons, several research groups have started to investigate the application of the fast growing field of microfluidic chemistry to radiosynthetic procedures. After the first report in 2004, many scientific papers have been published and demonstrated the potential for increased process yields, reduced reagent use, improved flexibility and general ease of setup. This review will address definitions occurring in microfluidics as well as analyze the different approaches under two macro-categories: microvessel and microchannel. In this perspective, several works will be collected, involving the use of positron emitting species ((11)C, (18)F, (64)Cu) and the fewer examples of gamma emitting radionuclides ((99m)Tc, (125/131)I). New directions in microfluidic research applied to PET radiochemistry, future developments and challenges are also discussed.

Dose-on-demand of diverse 18F-fluorocholine derivatives through a two-step microfluidic approach

INTRODUCTION The validation and confirmation of clinical usefulness of new and known positron emission tomography (PET) tracers require stable production routes and simple and robust radiochemical procedures. Microfluidic technologies are regarded as an approach that could allow an unprecedented flexibility and productivity in PET radiopharmaceutical research. In this work, we will show how a commercially available microfluidic system can be used for a sequential and repeatable radiosynthesis of three different fluorocholine analogues currently under investigation as tumor tracers. METHODS Advion microfluidic system was used for performing the synthesis and purification of [(18)F]fluoromethyl, [(18)F]fluoroethyl or [(18)F]fluoropropyl choline employing a two-step approach, starting from the corresponding alkyl-ditosylate and reacting the [(18)F]fluorotosylate obtained in the first step with neat dimethylethanolamine. The purification was obtained using a recyclable SPE cartridge set. RESULTS The three products, fluoromethylcholine, fluoroethylcholine and fluoropropylcholine, were obtained in good to optimum yields (22%-54% decay corrected) with a 15-min procedure. The production could be restarted several times for producing each one of the tracers without decrease in yields and purities, in accordance with a dose-on-demand (DOD) approach. The final products were formulated in isotonic saline solution. CONCLUSION The described approach gives a proof of principle of the enhanced productivity obtainable using a microfluidic approach; in particular, the possibility to produce the reported tracers in a DOD fashion following a homogeneous synthetic and purification approach will foster further studies on the clinical evaluation of the best fluorocholine analogue for prostate cancer imaging without biasing for differences in radiochemical approach.

Radiochemistry on chip

We have developed an integrated microfluidic platform for producing 2-[(18)F]-fluoro-2-deoxy-D-glucose ((18)F-FDG) in continuous flow from a single bolus of radioactive isotope solution, with constant product yields achieved throughout the operation that were comparable to those reported for commercially available vessel-based synthesisers (40-80%). The system would allow researchers to obtain radiopharmaceuticals in a dose-on-demand setting within a few minutes. The flexible architecture of the platform, based on a modular design, can potentially be applied to the synthesis of other radiotracers that require a two-step synthetic approach, and may be adaptable to more complex synthetic routes by implementing additional modules. It can therefore be employed for standard synthesis protocols as well as for research and development of new radiopharmaceuticals.

Piscivory in a Miocene Cetotheriidae of Peru: first record of fossilized stomach content for an extinct baleen-bearing whale

Instead of teeth, modern mysticetes bear hair-fringed keratinous baleen plates that permit various bulk-filtering predation techniques (from subsurface skimming to lateral benthic suction and engulfment) devoted to various target prey (from small invertebrates to schooling fish). Current knowledge about the feeding ecology of extant cetaceans is revealed by stomach content analyses and observations of behavior. Unfortunately, no fossil stomach contents of ancient mysticetes have been described so far; the investigation of the diet of fossil baleen whales, including the Neogene family Cetotheriidae, remains thus largely speculative. We report on an aggregate of fossil fish remains found within a mysticete skeleton belonging to an undescribed late Miocene (Tortonian) cetotheriid from the Pisco Formation (Peru). Micro-computed tomography allowed us to interpret it as the fossilized content of the forestomach of the host whale and to identify the prey as belonging to the extant clupeiform genus Sardinops. Our discovery represents the first direct evidence of piscivory in an ancient edentulous mysticete. Since among modern mysticetes only Balaenopteridae are known to ordinarily consume fish, this fossil record may indicate that part of the cetotheriids experimented some degree of balaenopterid-like engulfment feeding. Moreover, this report corresponds to one of the geologically oldest records of Sardinops worldwide, occurring near the Tortonian peak of oceanic primary productivity and cooling phase. Therefore, our discovery evokes a link between the rise of Cetotheriidae; the setup of modern coastal upwelling systems; and the radiation of epipelagic, small-sized, schooling clupeiform fish in such highly productive environments.

Radiopharmaceuticals, Drug Development and Pharmaceutical Regulations in Europe

Radiopharmaceuticals have a long tradition of clinical and research applications. Current legislation of developed Countries includes these compounds in the regulatory environment of medicinal products. Products used under a marketing authorisation license and investigational radiopharmaceuticals are then part of the clinical practice and scientific programs. Positron Emission Tomography has induced a strong increase in the number of potentially available radiopharmaceuticals and, beside being a breakthrough in diagnostic nuclear medicine, has demostrated its value as research tool. Drug Development Research is searching new tools for reducing attrition and increasing efficiency in the identification and development of new medicines. Molecular Imaging, PET in particular seems to have important answers to this demand. The regulatory environment in Europe is hence revised in the perspective of utilisation of nuclear molecular imaging as a supporting tool for DDR. Relevant documents from European regulatory Agency (EMEA) as well as their essential impact on radiopharmaceuticals have been summarised and discussed.

Effects of long time exposure to simulated micro- and hypergravity on skeletal architecture

This manuscript reports the structural alterations occurring in mice skeleton as a consequence of the longest-term exposition (90 days) to simulated microgravity (hindlimb unloading) and hypergravity (2g) ever tested. Bone microstructural features were investigated by means of standard Cone Beam X-ray micro-CT, Synchrotron Radiation micro-CT and histology. Morphometric analysis confirmed deleterious bone architectural changes in lack of mechanical loading with a decrease of bone volume and density, while bone structure alterations caused by hypergravity were less evident. In the femurs from hypergravity-exposed mice, the head/neck cortical thickness increment was the main finding. In addition, in these mice the rate of larger trabeculae (60-75 μm) was significantly increased. Interestingly, the metaphyseal plate presented a significant adaptation to gravity changes. Mineralization of cartilage and bone deposition was increased in the 2g mice, whereas an enlargement of the growth plate cartilage was observed in the hindlimb unloaded group. Indeed, the presented data confirm and reinforce the detrimental effects on bone observed in real space microgravity and reveal region-specific effects on long bones. Finally these data could represent the starting point for further long-term experimentations that can deeply investigate the bone adaptation mechanisms to different mechanical force environments.