Ingestible sensors are potentially a powerful tool for monitoring human health. Sensors have been developed that can, for example, provide pH and pressure readings or monitor medication, but capsules that can provide key information about the chemical composition of the gut are still not available. Here we report a human pilot trial of an ingestible electronic capsule that can sense oxygen, hydrogen, and carbon dioxide. The capsule uses a combination of thermal conductivity and semiconducting sensors, and their selectivity and sensitivity to different gases is controlled by adjusting the heating elements of the sensors. Gas profiles of the subjects were obtained while modulating gut microbial fermentative activities by altering their intake of dietary fibre. Ultrasound imaging confirmed that the oxygen-equivalent concentration profile could be used as an accurate marker for the location of the capsule. In a crossover study, variations of fibre intake were found to be associated with differing small intestinal and colonic transit times, and gut fermentation. Regional fermentation patterns could be defined via hydrogen gas profiles. Our gas capsule offers an accurate and safe tool for monitoring the effects of diet of individuals, and has the potential to be used as a diagnostic tool for the gut. NATuRE ELECTRONiCS

It is known that the unique layered structure of orthorhombic MoO3 (α-MoO3) facilitates the interaction with H2 gas molecules and that the surface-to-volume ratios of the crystallites play an important role in the process. MoO3 was deposited on a wide variety of transparent substrates using thermal evaporation in order to alter the surface-to-volume ratios of the crystallites. In situ Raman spectroscopy was employed to investigate the interaction between MoO3 and 1% H2 in both N2 and synthetic air environments, while incorporating Pd as a catalyst at room temperature. This study confirmed that the layered MoO3 with a high surface-to-volume ratio facilitated the H2 gas interaction. The Raman spectroscopy studies revealed that the H+ ions mainly interacted with the doubly coordinated oxygen atoms and caused the crystal transformation from the original α-MoO3 into the mixed structure of hydrogen molybdenum bronze and substoichiometric MoO3, eventually forming oxygen vacancies and water. It was also found that the presence of O2 during the H2 gas exposure caused the recombination of a number of oxygen vacancies and reduced the available surface catalytic sites for H2.

Increasing cell survival in stem cell therapy is an important challenge for the field of regenerative medicine. Here, we report theranostic mesoporous silica nanoparticles that can increase cell survival through both diagnostic and therapeutic approaches. First, the nanoparticle offers ultrasound and MRI signal to guide implantation into the peri-infarct zone and away from the most necrotic tissue. Second, the nanoparticle serves as a slow release reservoir of insulin-like growth factor (IGF)—a protein shown to increase cell survival. Mesenchymal stem cells labeled with these nanoparticles had detection limits near 9000 cells with no cytotoxicity at the 250 µg/mL concentration required for labeling. We also studied the degradation of the nanoparticles and showed that they clear from cells in approximately 3 weeks. The presence of IGF increased cell survival up to 40% (p<0.05) versus unlabeled cells under in vitro serum-free culture conditions.

Nanoparticles are a new class of imaging agent used for both anatomic and molecular imaging. Nanoparticle-based imaging exploits the signal intensity, stability, and biodistribution behavior of submicron-diameter molecular imaging agents. This review focuses on nanoparticles used in human medical imaging, with an emphasis on radionuclide imaging and MRI. Newer nanoparticle platforms are also discussed in relation to theranostic and multimodal uses.Key Words: nanoparticles; medical imaging; molecular imaging; nanoparticle; imaging and diagnostics Nucl Med 2016; 57:1833 57: -1837 57: DOI: 10.2967 Medical imaging offers rapid, longitudinal, and noninvasive visualization of the interior of living subjects. There are two main approaches to medical imaging, the first being anatomic imaging, which provides information on gross structure, and the second being molecular or functional imaging, which provides information on physiology and cellular processes such as metabolism, protein expression, and DNA synthesis (1). Although exogenous imaging agents are optional for anatomic imaging (e.g., MRI or CT contrast medium agents, which help improve tissue contrast), they are virtually a requirement for molecular imaging, especially within the realm of nuclear medicine, for which radioisotopes are required for single-photon emission CT (SPECT) or PET. JThe 3 main classes of imaging agents include small molecules, proteins, and nanoparticles. Most scans use small molecules, which are agents below 2,000 kDa and measure approximately 1 nm (e.g., 18 F-FDG for PET, iodinated small molecules for CT, and chelated gadolinium for MRI). Protein imaging agents, such as radiolabeled monoclonal antibodies, are less common but offer precise molecular information and are a growing area of research. Nanoparticles are a new and exciting class of imaging agent that can be used for both anatomic and molecular imaging.Their small size and unique properties (high ratio of surface area to volume) offer, first, intense and longitudinally stable imaging signals (quantum and C dots); second, different targeting strategies (passive targeting via the mononuclear phagocyte system or active targeting to specific molecular targets as a result of functionalization with ligands); third, high avidity (a large association constant brought about by the presence of multiple ligands per particle); fourth, theranostic capabilities (use for both diagnostic purposes, by generating an imaging signal, and therapeutic purposes, by delivering a drug payload); fifth, multimodal signal capabilities (detection of one nanoparticle by more than one imaging modality, making it suitable for deep tissue imaging, screening with MRI, and intraoperative guidance using superficial imaging with optical imaging); and sixth, multiplexing (detection of multiple different molecular targets simultaneously).Although many of these features have been demonstrated only in animal models, there are several nanoparticle formulations that have been transitioned into clinical practice. This revi...