Electrochemical hydrazine oxidation and proton reduction occur at a significantly higher rate at Pt than at Au or C electrodes. Thus, the collision and adhesion of a Pt particle on a less active Au or C electrode leads to a large current amplification by electrocatalysis at single nanoparticles (NPs). At low particle concentrations, the collision of Pt NPs was characterized by current transients composed of individual current profiles that rapidly attained a steady state, signaling single NP collisions. The characteristic steady-state current was used to estimate the particle size. The fluctuation in collision frequency with time indicates that the collision of NPs at the detector electrodes occurs in a statistically random manner, with the average frequency a function of particle concentration and diffusion coefficient. A longer term current decay in single current transients, as opposed to the expected steady-state behavior, was more pronounced for proton reduction than for hydrazine oxidation, revealing microscopic details of the nature of the particle interaction with the detector electrode and the kinetics of electrocatalysis at single NPs. The study of single NP collisions allows one to screen particle size distributions and estimate NP concentrations and diffusion coefficients.

An extensive comparative study of the effects of microwave versus conventional heating on the nucleation and growth of near-monodisperse Rh, Pd, and Pt nanoparticles has revealed distinct and preferential effects of the microwave heating method. A one-pot synthetic method has been investigated, which combines nucleation and growth in a single reaction via precise control over the precursor addition rate. Using this method, microwave-assisted heating enables the convenient preparation of polymer-capped nanoparticles with improved monodispersity, morphological control, and higher crystallinity, compared with samples heated conventionally under otherwise identical conditions. Extensive studies of Rh nanoparticle formation reveal fundamental differences during the nucleation phase that is directly dependent on the heating method; microwave irradiation was found to provide more uniform seeds for the subsequent growth of larger nanostructures of desired size and surface structure. Nanoparticle growth kinetics are also markedly different under microwave heating. While conventional heating generally yields particles with mixed morphologies, microwave synthesis consistently provides a majority of tetrahedral particles at intermediate sizes (5-7 nm) or larger cubes (8+ nm) upon further growth. High-resolution transmission electron microscopy indicates that Rh seeds and larger nanoparticles obtained from microwave-assisted synthesis are more highly crystalline and faceted versus their conventionally prepared counterparts. Microwave-prepared Rh nanoparticles also show approximately twice the catalytic activity of similar-sized conventionally prepared particles, as demonstrated in the vapor-phase hydrogenation of cyclohexene. Ligand exchange reactions to replace polymer capping agents with molecular stabilizing agents are also easily facilitated under microwave heating, due to the excitation of polar organic moieties; the ligand exchange proceeds with excellent retention of nanoparticle size and structure.

An environmentally friendly reversed-phase HPLC method for simultaneous determination of creatinine and uric acid in human urine samples has been developed. Human urine samples were pretreated by dilution, protein precipitation, centrifugation and filtration, followed by HPLC separations using a reversed-phase C18 column with an aqueous mobile phase of phosphate buffer. The retention loss of a C18 column when using the highly aqueous mobile phases was avoided by employing a gradient elution using a small volume (<0.23 mL) of acetonitrile and phosphate buffer at pH 4.75. This developed method provides a simple, rapid separation and sensitive detection for the species of interest in 10 min with UV detection at 205 nm. Quantitation was carried out by relating the peak areas of the identified compounds to that of hypoxanthine as an internal standard. The detection limits for creatinine and uric acid were 0.045 and 0.062 mg mL -1 , respectively. The recoveries of the standards added to urine samples were 87.3 -102.2% for creatinine and 97.3 -108.6% for uric acid, and the relative standard deviation for both analytes was less than 1.0%. This method has been successfully applied to estimating of creatinine and uric acid in human urine.

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BackgroundTo examine the prevalence of diabetes and prediabetes in Songming county, Yunnan province, South-west China and examine influences of anthropometric indicators on diabetic risk.MethodsThis study was a population based cross-sectional study of 1031 subjects in Songming County aged 30 years and older. Age-standardization was performed by using the 2010 Songming population as the standard population. After an overnight fasting, participants underwent an oral glucose tolerance test (OGTT), and venous blood glucose levels were measured to identify diabetes and prediabetes. Physicians completed questionnaires and blood pressure measurements; trained nurses measured anthropometric variables. Age-adjusted logistic regression models were used to assess the association between anthropometric variables and diabetes.ResultsTotal prevalences of diabetes and prediabetes were 10.0% and 11.6%, respectively. In women, prevalence of diabetes and prediabetes significantly increased with body mass index (BMI),waist hip ratio (WHR), and waist-to-height ratio (WHtR). But in men, prevalence of diabetes and prediabetes only significantly increased with WHR and WHtR. Compared to 1st WHR tertile in women, there was a nearly tenfold increase in the risk of diabetes with 3rd WHR tertile (OR 10.50, 95% CI 3.95-27.86). Men with 3rd BMI tertile had 4.8-fold risk of getting diabetes compared to men with 1st WHtR tertile (OR 4.79, 95% CI 1.88-12.26). Only WHtR had significantly higher receiver operating characteristic (ROC) area than BMI in total men (0.668 vs. 0.561, p < 0.05). And in total women, only WHR had significantly higher ROC area than BMI (0.723 vs. 0.628, p < 0.05). In the partial correlation analysis controlling for waist circumference, only WHR had significant correlation with fasting plasma glucose (r = 0.132, p = 0.002) and 2-h plasma glucose (r = 0.162, p = 0.000) in women, and WHtR had a much stronger association with both fasting plasma glucose (r = 0.305, P = 0.000) and 2 h plasma glucose (r = 0.303, P = 0.000) than WHR in men.ConclusionHigh prevalence of diabetes and prediabetes were found in this underdeveloped region. About half of total subjects with diabetes were undiagnosed. The association of obesity indices and diabetic risk factors varied with gender. The strongest predictors of diabetes were WHR for the female subgroup and WHtR for the male subgroup.

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Mesenchymal stem cells (MSCs) have been optimal targets in the development of cell based therapies, but their limited availability and high death rate after transplantation remains a concern in clinical applications. This study describes novel effects of platelet rich clot releasate (PRCR) on rat bone marrow-derived MSCs (BM-MSCs), with the former driving a gene program, which can reduce apoptosis and promote the regenerative function of the latter in hostile microenvironments through enhancement of paracrine/autocrine factors. By using reverse transcriptionpolymerase chain reaction, immunofluorescence and western blot analyses, we showed that PRCR preconditioning could alleviate the apoptosis of BM-MSCs under stress conditions induced by hydrogen peroxide (H 2 O 2 ) and serum deprivation by enhancing expression of vascular endothelial growth factor and platelet-derived growth factor (PDGF) via stimulation of the platelet-derived growth factor receptor (PDGFR)/PI3K/AKT/NF-jB signaling pathways. Furthermore, the effects of PRCR preconditioned GFP-BM-MSCs subcutaneously transplanted into rats 6 h after wound surgery were examined by histological and other tests from days 0-22 after transplantation. Engraftment of the PRCR preconditioned BM-MSCs not only significantly attenuated apoptosis and wound size but also improved epithelization and blood vessel regeneration of skin via regulation of the wound microenvironment. Thus, preconditioning with PRCR, which reprograms BM-MSCs to tolerate hostile microenvironments and enhance regenerative function by increasing levels of paracrine factors through PDGFR-a/PI3K/AKT/NF-jB signaling pathways would be a safe method for boosting the effectiveness of transplantation therapy in the clinic.

Demands for development of biological therapies is rapidly increasing, as is the drive to reduce time to patient. In order to speed up development, the disposable Automated Microscale Bioreactor (Ambr 250) system is increasingly gaining interest due to its advantages, including highly automated control, high throughput capacity, and short turnaround time. Traditional early stage upstream process development conducted in 2 - 5 L bench-top bioreactors requires high foot-print, and running cost. The establishment of the Ambr 250 as a scale-down model leads to many benefits in process development. In this study, a comprehensive characterization of mass transfer coefficient (k a) in the Ambr 250 was conducted to define optimal operational conditions. Scale-down approaches, including dimensionless volumetric flow rate (vvm), power per unit volume (P/V) and k a have been evaluated using different cell lines. This study demonstrates that the Ambr 250 generated comparable profiles of cell growth and protein production, as seen at 5-L and 1000-L bioreactor scales, when using k a as a scale-down parameter. In addition to mimicking processes at large scales, the suitability of the Ambr 250 as a tool for clone selection, which is traditionally conducted in bench-top bioreactors, was investigated. Data show that cell growth, productivity, metabolite profiles, and product qualities of material generated using the Ambr 250 were comparable to those from 5-L bioreactors. Therefore, Ambr 250 can be used for clone selection and process development as a replacement for traditional bench-top bioreactors minimizing resource utilization during the early stages of development in the biopharmaceutical industry. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:478-489, 2017.