Purpose We developed a mouse model that enables non-invasive assessment of changes in β cell mass. Procedures We generated a transgenic mouse expressing luciferase under control of the mouse insulin I promoter [mouse insulin promoter-luciferase-Vanderbilt University (MIP-Luc-VU)] and characterized this model in mice with increased or decreased β cell mass and after islet transplantation. Results Streptozotocin-induced, diabetic MIP-Luc-VU mice had a progressive decline in bioluminescence that correlated with a decrease in β cell mass. MIP-Luc-VU animals fed a high-fat diet displayed a progressive increase in bioluminescence that reflected an increase in β cell mass. MIP-Luc-VU islets transplanted beneath the renal capsule or into the liver emitted bioluminescence proportional to the number of islets transplanted and could be imaged for more than a year. Conclusions Bioluminescence in the MIP-Luc-VU mouse model is proportional to β cell mass in the setting of increased and decreased β cell mass and after transplantation.

Single-layered graphene oxide (GO) has exhibited great promise in the areas of sensing, membrane filtration, supercapacitors, bioimaging, and therapeutic carriers because of its biocompatibility, large surface area, and electrochemical, photoluminescent, and optical properties. To elucidate how the physical dimensions of GO affect its intrinsic properties, we employed sonication to produce more than 130 different sizes of GO in aqueous dispersion and implemented new approaches to characterize various GO properties as a function of the average flake size. New protocols were developed to determine and compare the flake size of GO dispersions sonicated with energies up to 20 MJ/g by using dynamic light scattering and atomic force microscopy (AFM). The relationship between the average flake size and sonication energy per unit mass of GO was observed to follow a power law. AFM height measurements showed that the sonication of GO yielded monolayered flakes. Photoluminescence of GO was characterized as a function of the sonication energy (or the average flake size which is the monotonic function of the sonication energy), excitation wavelength, and pH of the dispersion. The strong dependence of the photoluminescence intensity on pH control and the variation of the photoluminescence intensity with different flake sizes were observed. An intense photoluminescence signal, likely related to the separation of the oxidative debris from the GO framework, was found at the highest sonication energies (E ≳ 15 MJ/g) or under extremely alkaline conditions (pH ≳ 11). The cytotoxicity of GO was studied with various flake sizes. Size- and concentration-dependent cytotoxicity was observed for cell lines NIH 3T3 and A549. The NIH 3T3 cell line also demonstrated time-dependent cytotoxicity.

Surface chemistry is an important factor for quality control during production of nanomaterials and for controlling their behavior in applications and when released into the environment.

Despite significant advances in single-walled carbon nanotube (SWNT) synthesis and purification strategies, the separation of metallic and semiconducting SWNTs on a large scale remains a barrier to the realization of many commercial applications. Selective extraction of specific SWNT types by wrapping and dispersion with conjugated polymers has been found effective for semiconducting SWNTs, but structural parameters that dictate selectivity are poorly understood. Here, we report nanotube dispersions with two structurally similar conjugated copolymers, both being poly-(fluorene-co-phenylene) derivatives, having comparable degrees of polymerization but differing in the extent of electron donation from functional groups on the phenylene comonomers. It is found that copolymers decorated with electron donating methoxy functionalities lead to predominant dispersion of semiconducting SWNTs, while copolymers decorated with electron withdrawing nitro functionalities bias the dispersion toward metallic SWNTs. Differentiation of semiconducting and metallic SWNT populations was carried out by a combination of UV−vis−NIR absorption spectroscopy, Raman spectroscopy using multiple excitation wavelengths, and fluorescence spectroscopy. These results provide new insight into polymer design features that dictate preferential dispersion of specific SWNT types. ■ INTRODUCTIONAmong the known nanoscale materials, single-walled carbon nanotubes (SWNTs) have attracted a tremendous amount of research attention since their discovery. 1−5 Their unique properties, including high tensile strength, 6 high aspect ratio, 7 thermal and electrical conductivity, 8−11 and extraordinary optical characteristics, 12−14 make them potentially valuable components of advanced materials with a wide range of applications. Indeed, SWNTs have been incorporated in fieldeffect transistors (FETs), 7,15 sensors, 16−19 photodetectors, 20 photovoltaics, 21−23 flexible printed circuits, 24 electrode materials for flexible electronics, 25 touch screens, 26 and microelectronic interconnects, 27 among other devices. 28 In these applications, the molecular nature, resilience, and amenity to chemical modification of SWNTs make them decisively advantageous over many other nanoscale materials. However, despite recent progress in nanotube commercialization, 27 applications that require controlled electrical and optical properties have not kept pace with expectations. This lag is a consequence of the inability to industrially prepare SWNTs that are pure in terms of their electrical properties. All known SWNT synthesis methods, such as high-pressure carbon monoxide disproportionation (HiPCO), 29 carbon vapor deposition (CVD), 30 arc discharge, 31 laser ablation, 32 and plasma torch growth, 33 result in the production of mixtures of metallic SWNTs (m-SWNTs) and semiconducting SWNTs (sc-SWNTs). 34 Since components of electronic devices require either m-SWNTs (electrodes, interconnects, etc.) or sc-SWNTs (transistors, sensors, etc.), their separation into pure samples is imperat...

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