A technique to quantify very low activities in regions of interest with a collimatorless detector

We present a new method to measure sub-microcurie activities of photon-emitting radionuclides in organs and lesions of small animals in vivo. Our technique, named the collimator-less likelihood fit, combines a very high sensitivity collimatorless detector with a Monte Carlo-based likelihood fit in order to estimate the activities in previously segmented regions of interest along with their uncertainties. This is done directly from the photon projections in our collimatorless detector and from the region of interest segmentation provided by an x-ray computed tomography scan. We have extensively validated our approach with 225Ac experimentally in spherical phantoms and mouse phantoms, and also numerically with simulations of a realistic mouse anatomy. Our method yields statistically unbiased results with uncertainties smaller than 20% for activities as low as ~111 Bq (3 nCi) and for exposures under 30 minutes. We demonstrate that our method yields more robust recovery coefficients when compared to SPECT imaging with a commercial pre-clinical scanner, specially at very low activities. Thus, our technique is complementary to traditional SPECT/CT imaging since it provides a more accurate and precise organ and tumor dosimetry, with a more limited spatial information. Finally, our technique is specially significant in extremely low-activity scenarios when SPECT/CT imaging is simply not viable.

Highly efficient color-tunable organic co-crystals unveiling polymorphism, isomerism, delayed fluorescence for optical waveguides and cell-imaging

Photofunctional co-crystal engineering strategies based on donor-acceptor π-conjugated system facilitates expedient molecular packing, consistent morphology, and switchable optical properties, conferring synergic 'structure-property relationship' for optoelectronic and biological functions. In this work, a series of organic co-crystals were formulated using a twisted aromatic hydrocarbon (TAH) donor and three diverse planar acceptors, resulting in color-tunable solid and aggregated state emission via variable packing and through-space charge-transfer interactions. While, adjusting the strength of acceptors, a structural transformation into hybrid stacking modes ultimately results in color-specific polymorphs, a configurational cis-isomer with very high photoluminescence quantum yield. The cis-isomeric co-crystal exhibits triplet-harvesting thermally activated delayed fluorescence (TADF) characteristics, presenting a key discovery in hydrocarbon-based multicomponent systems. Further, 1D-microrod-shaped co-crystal acts as an efficient photon-transducing optical waveguides, and their excellent dispersibility in water endows efficient cellular internalization with bright cell imaging performances. These salient approaches may open more avenues for the design and applications of TAH based co-crystals.

A conformational tweak for enhanced cellular internalization, photobleaching resistance and prolonged imaging efficacy

A strategy of conformational tweaking regulates the condensed state behavior of naphthalimide skeletal isomers (NSIs) and enhances their photophysical properties, cellular uptake and prolonged imaging capability. This salient approach results in a large Stokes shift (>120 nm), rapid cellular internalization, photobleaching resistance, and efficient bioimaging of the ribbon-like nano-assembly superior to that of its electronically similar micro-flower isomer.

Efficient induction of apoptosis in cancer cells by paclitaxel-loaded selenium nanoparticles

Aim: To develop selenium nanoparticles (SeNPs)-based delivery systems for paclitaxel (PTX) and assess their antiproliferative efficacy against cancer cells in vitro with potential mechanistic insight. Methods: Pluronic F-127 stabilized SeNPs were prepared and characterized. Effects of PTX-loaded SeNPs on lung (A549), breast (MCF7), cervical (HeLa) and colon (HT29) cancer cells were studied by viability assay complemented with flow-cytometric analyses of cell cycle, apoptosis, mitochondrial membrane potential, intracellular reactive oxygen species and caspase activity. Results: PTX-loaded SeNPs demonstrated significant antiproliferative activity against cancer cells. Cell cycle analyses of PTX-SeNPs treated cells established G2/M phase arrest in a dose-dependent manner leading to apoptosis. Further investigation revealed disruption of mitochondrial membrane potential orchestrated with induction of reactive oxygen species leading to the activation of caspases, key players of apoptotic cell death. Conclusion: Efficient induction of apoptosis in various cancer cells by PTX-loaded SeNPs, with appropriate future studies, might lead to potential anticancer strategies.