Oxide-Free Gadolinium Nanoparticles as MRI Contrast Agents

The Gd element and other rare-earth metals are notoriously difficult to use in chemical synthesis due to their high reduction potentials and aggressive reactivities with ambient oxygen, which almost always leads to the formation of oxides. The challenge in chemical synthesis limits the range of applications for rare-earth metals. The most important use of Gd at the moment is nanocrystals for technological applications. Herein, we report for the first time the successful production of size-controllable, solid core-shell oxide-free Gd metal nanocrystals. We have solved the long-standing problem of oxidation through a reduction process and appropriate capping. The manuscript describes the procedure and detailed characterizations of the process to ensure the highest quality of the produced particles. In particular, the nanocrystals displayed the largest saturation magnetization observed to date for nanocrystalline Gd metal. This value (206 emu/g at 2K) currently stands as the world record.Another important application of Gd is contrast agent development for MRI. To this end, we have performed NMR relaxivity measurements to evaluate the performance of the nanoparticles as potential MRI contrast agents. Typically, Gd based nanoconstructs such as FDA approved Gd-DTPA chelates are T1 MRI contrast agents; however, we demonstrate, for the first time, that pure Gd nanoparticles can also be used as state-of-the art T2 contrast agents. World record high values for transverse proton relaxitivity (r2 of 232 mM-1s-1 per Gd atom and per-particle relaxivity (2.9 x 10^8 mM-1s-1 have been obtained, exceeding the current highest per-particle r2 values. These results make our Gd nanocrystals the most promising MRI contrast agents for use in biomedical applications. For the first time, this puts MRI on par with positron emission tomography in terms of sensitivity to detection of a contrast agent.We further developed the nanoparticles and we demonstrate record high saturation magnetizations for Gd nanoparticles, namely, 226 emu/g at 5 T. This magnetization is substantially higher than anything achieved to date. We have achieved such high magnetizations in a reliable and reproducible manner by controlling the crystallinity of the grown Gd nanofilm. The crystallinity of Gd is found to play an important role in the observed magnetization values. The higher magnetization is observed for nanoparticles that have a lower content of paramagnetic face-centered cubic (fcc) phase and greater content of ferromagnetic hexagonal close-packed (hcp) phase. Control over fcc and hcp content in the lattice was achieved by adjusting the deposition rate of Gd metal during the nanofabrication process. Our results indicate the remarkable influence of nanocrystallinity on the magnetism of Gd and the ability to control it.Our novel fabrication technique, which overcomes the problems of current synthetic approaches to rare-earth nanoparticle synthesis through the careful optimization of capping and hydrogen reduction techniques, can also be applied to other rare-earth metals and alloys. This opens the door to fundamental studies on these materials at the nanoscale. It will also enable the realization of the full potential of rare-earth metals in industry

Controlled nanocrystallinity in Gd nanobowls leads to magnetization of 226 emu/g

Gadolinium (Gd) metal is of great interest in applications such as contrast-enhanced MRI and magnetic cooling. However, it is generally difficult to produce oxide-free and highly magnetic Gd nanoparticles due to the aggressively reactive nature of Gd with oxygen. Herein, we utilized a nanofabrication route and optimization of experimental conditions to produce highly magnetic airstable oxide-free Gd nanoparticles. The nanobowls displayed the highest saturation magnetization to date for Gd, reaching 226.4 emu/g at 2K. The crystalline composition of Gd is found to affect the observed magnetization values: the higher magnetization is observed for nanoparticles that have a lower content of the paramagnetic face-centered cubic (fcc) phase and a greater content of the ferromagnetic hexagonal close-packed (hcp) phase. The relative fcc content was found to depend on the deposition rate of the Gd metal during the nanofabrication process, thereby correlating with altered magnetization. Published by AIP Publishing

Advanced Computational Methodologies Used in the Discovery of New Natural Anticancer Compounds

Natural chemical compounds have been widely investigated for their programmed necrosis causing characteristics. One of the conventional methods for screening such compounds is the use of concentrated plant extracts without isolation of active moieties for understanding pharmacological activity. For the last two decades, modern medicine has relied mainly on the isolation and purification of one or two complicated active and isomeric compounds. The idea of multi-target drugs has advanced rapidly and impressively from an innovative model when first proposed in the early 2000s to one of the popular trends for drug development in 2021. Alternatively, fragment-based drug discovery is also explored in identifying target-based drug discovery for potent natural anticancer agents which is based on well-defined fragments opposite to use of naturally occurring mixtures. This review summarizes the current key advancements in natural anticancer compounds; computer-assisted/fragment-based structural elucidation and a multi-target approach for the exploration of natural compounds

Thermal behavior of the molten pool, microstructural evolution, and tribological performance during selective laser melting of TiC/316L stainless steel nanocomposites: Experimental and simulation methods

Bulk-form nanocomposites of TiC-reinforced 316L stainless steel matrix were fabricated by selective laser melting (SLM), an emerging powder-bed additive manufacturing technique which allows the direct fabrication of usable end-products, using various volumetric laser energy densities (a). The microstructural features of the distribution and sizes of TiC nanoparticles, as well as the grain sizes and tribological performances of the SLMprocessed nanocomposite parts, were sensitive to the applied eta. Increasing eta enhanced the dispersion state of nanoscale TiC owing to intensified Marangoni flow and the corresponding capillary force, which prevented TiC aggregation and promoted a uniform dispersion of reinforcements in the solidified matrix. However, with increasing eta, the TiC particle size also increased, and some nanoparticles lost their initial nanostructure because of significant thermal accumulation within the molten pool. Increasing eta also caused increases in the grain sizes of the fabricated nanocomposite because of the decreasing cooling rate. A simulation model was developed to enhance understanding of the manufacturability of these new materials, as well as to predict the temperature evolution and thermal behaviors of the molten pool under various eta. The simulation modeled the effects of various eta values on the temperature distribution evolutions and the corresponding effects of Marangoni convection during the SLM process. The temperature distribution was significantly influenced by the applied a; the maximum temperature gradient within the molten pool was increased significantly with increased a. The simulation results validated the experimental results and the underlying physical mechanism of the molten pool. The microhardness of the SLM nanocomposite decreased sharply with increased grain size due to the lower cooling rate, but increased with further increases in eta because of the enhanced densification degree. Nanocomposites processed under the optimum condition of eta = 200 J/mm(3) showed the lowest wear rates accompanied by the formation of adherent and strain-hardened tribolayers on the worn surfaces of the nano composites, suggesting improved tribological performance

Oxide-Free Gadolinium Nanocrystals with Large Magnetic Moments

Among the elements in the periodic table, gadolinium (Gd) has the highest number of unpaired electrons. However, the potential of this rare-earth metal has not yet been fully realized due to challenges in its chemical synthesis, namely, its high reduction potential, leading to the formation of oxides with suboptimal properties. This problem is also prevalent with other lanthanides, severely limiting their uses in industry. Herein, a fabrication approach along with a reduction process and appropriate capping have been developed to produce oxide-free, stable gadolinium nanoparticles. We demonstrate broad tunability of the particle size while maintaining remarkably narrow size distributions (<5%). The nanoconstructs displayed the highest magnetization measured to date for Gd, 206 emu/g Gd at 2 K along with a record high per particle nuclear magnetic resonance (NMR) transverse relaxivity (r(2)) of 2.7 x 10(8) mM(-1) s(-1), which corresponds to the highest per-particle r2 relaxivity reported for any T-2 contrast agents to date. Unlike traditional approaches, this process can be extended to produce oxide-free nanoconstructs of other lanthanides, making them accessible for technological or biomedical applications

Supercapacitor behaviors of polyaniline/CuO, polypyrrole/CuO and PEDOT/CuO nanocomposites

Polyaniline (PANI)/copper oxide (CuO), poly(3,4-ethylenedioxythiophene) (PEDOT)/CuO and polypyrrole (PPy)/CuO have been synthesized electrochemically on glassy carbon electrode in sodium dodecyl sulfate in sulfuric acid solution as an electroactive material. To our best knowledge, the first report on comparison of supercapacitor behaviors of PANI/CuO, PEDOT/CuO and PPy/CuO nanocomposite films was studied by electrochemical impedance spectroscopy, related to the plots of Nyquist, Bode magnitude and Bode phase. The highest specific capacitance (C (sp)) was obtained as C (sp) = 286.35 F x g(-1) at the scan rate of 20 mV x s(-1) for PANI/CuO amongst the PEDOT/CuO (C (sp) = 198.89 F x g(-1) at 5 mV x s(-1)) and PPy/CuO (C (sp) = 20.78 F x g(-1) at 5 mV x s(-1)) by CV method. Long-term stability of the capacitor has also been tested by CV method, and the results indicated that, after 500 cycles, the specific capacitance of PANI/CuO nanocomposite film is 81.82 % of the initial capacitance. An equivalent circuit model of R (s)(C (dl)(R (1)(Q(R (2) W)))) has been used to fit the experimental and theoretical data

Red is no Warmer than Blue: A Challenge to the Semantic Coding Hypothesis

Participants were simultaneously presented with a colour square on a monitor (red, black or blue) and a temperature at their fingertip using a peltier tile (warm, room temperature or cool). Each stimulus pair was presented in congruent (red-warm and blue-cool) and incongruent (red-cool and blue-warm) combinations. Latencies were recorded for each participant's verbal response when naming the colour and the temperature. The semantic coding hypothesis proposes that although input patterns and types are different for different sense organs, interactions can occur after these inputs have been recoded at post-perceptual levels. For example, reaction times to a simultaneously presented high-pitched tone and light source above head height might be shorter than those to a low-pitched tone and light source above head height because the recoded inputs of the former share the post-perceptual format “high”, whereas the later do not (ie, the later are incongruent). In our experiment, response times were similar regardless of whether the stimulus pair was “congruent” or “incongruent”, suggesting that while it is commonly believed that red is a warm colour and blue is cold, this kind of correspondence did not facilitate shorter latencies as it should according to the semantic coding hypothesis

Surface ligand-directed pair-wise hydrogenation for heterogeneous phase hyperpolarization

para-Hydrogen induced polarization is a technique of magnetic resonance hyperpolarization utilizing hydrogen's para-spin state for generating signal intensities at magnitudes far greater than state-of-the-art magnets. Platinum nanoparticle-catalysts with cysteine-capping are presented. The measured polarization is the highest reported to date in water, paving pathways for generating medical imaging contrast agents

Preparation and evaluation of bismuth sulfide and magnetite-based theranostic nanohybrid as drug carrier and dual MRI/CT contrast agent

Due to the increased incidence and population growth that has been leading to growing number of cases worldwide, early diagnosis and treatment of cancer is crucial. Low density cancer tissue cannot be diagnosed before progressing toward a metastatic stage. Thus, theranostic systems play a significant role in assisting timely diagnosis and treatment. The combination of magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents in a single probe is of high importance and necessity, where individual strengths of each approach can be merged while shortcomings of each modality could be compensated. With this motivation, we have developed and synthesized Bi2S3@BSA-Fe3O4 nanoparticles as a dual MRI/CT contrast agent and carrier of curcumin (CUR) as natural anticancer drug. The nanoparticles shortened both the longitudinal (T-1) and transverse (T-2), MRI relaxation times, with a more distinct effect on producing negative contrast (T-2) images with a relaxivity (r(2)) of 54.73 mM(-1) s(-1). The magnetite/bismuth hybrid nanoparticle also was capable of increasing CT image contrast. Further, in vitro cytotoxicity assay showed high biocompatibility of the synthesized nanoparticles. Furthermore, in vitro cytotoxicity assay on cancer cells showed high anticancer activity of the synthesized nanoparticles

Biomimetic cell membrane‐coated poly(lactic‐co‐glycolic acid) nanoparticles for biomedical applications

Abstract Poly(lactic‐co‐glycolic acid) (PLGA) nanoparticles (NPs) are commonly used for drug delivery because of their favored biocompatibility and suitability for sustained and controlled drug release. To prolong NP circulation time, enable target‐specific drug delivery and overcome physiological barriers, NPs camouflaged in cell membranes have been developed and evaluated to improve drug delivery. Here, we discuss recent advances in cell membrane‐coated PLGA NPs, their preparation methods, and their application to cancer therapy, management of inflammation, treatment of cardiovascular disease and control of infection. We address the current challenges and highlight future research directions needed for effective use of cell membrane‐camouflaged NPs