Preparation of Cu/Sn-Organic Nano-Composite Catalysts for Potential Use in Hydrogen Evolution Reaction and Electrochemical Characterization.

In this work, the solvothermal solidification method has been used to be prepared as a homogenous CuSn-organic nano-composite (CuSn-OC) to use as a catalyst for alkaline water electrolysis for cost-effective H2 generation. FT-IR, XRD, and SEM techniques were used to characterize the CuSn-OC which confirmed the formation of CuSn-OC with a terephthalic acid linker as well as Cu-OC and Sn-OC. The electrochemical investigation of CuSn-OC onto a glassy carbon electrode (GCE) was evaluated using the cyclic voltammetry (CV) method in 0.1 M KOH at room temperature. The thermal stability was examined using TGA methods, and the Cu-OC recorded a 91.4% weight loss after 800 °C whereas the Sn-OC and CuSn-OC recorded 16.5 and 62.4%, respectively. The results of the electroactive surface area (ECSA) were 0.5, 0.42, and 0.33 m2 g-1 for the CuSn-OC, Cu-OC, and Sn-OC, respectively, and the onset potentials for HER were -420, -900, and -430 mV vs. the RHE for the Cu-OC, Sn-OC, and CuSn-OC, respectively. LSV was used to evaluate the electrode kinetics, and the Tafel slope for the bimetallic catalyst CuSn-OC was 190 mV dec-1, which was less than for both the monometallic catalysts, Cu-OC and Sn-OC, while the overpotential was -0.7 vs. the RHE at a current density of -10 mA cm-2.

A microfluidic strategy to capture antigen-specific high affinity B cells.

Assessing B cell affinity to pathogen-specific antigens prior to or following exposure could facilitate the assessment of immune status. Current standard tools to assess antigen-specific B cell responses focus on equilibrium binding of the secreted antibody in serum. These methods are costly, time-consuming, and assess antibody affinity under zero-force. Recent findings indicate that force may influence BCR-antigen binding interactions and thus immune status. Here, we designed a simple laminar flow microfluidic chamber in which the antigen (hemagglutinin of influenza A) is bound to the chamber surface to assess antigen-specific BCR binding affinity of five hemagglutinin-specific hybridomas under 65- to 650-pN force range. Our results demonstrate that both increasing shear force and bound lifetime can be used to enrich antigen-specific high affinity B cells. The affinity of the membrane-bound BCR in the flow chamber correlates well with the affinity of the matched antibodies measured in solution. These findings demonstrate that a microfluidic strategy can rapidly assess BCR-antigen binding properties and identify antigen-specific high affinity B cells. This strategy has the potential to both assess functional immune status from peripheral B cells and be a cost-effective way of identifying individual B cells as antibody sources for a range of clinical applications.

Mouse ovarian follicle cryopreservation using vitrification or slow programmed cooling: assessment of in vitro development, maturation, ultra-structure and meiotic spindle organization.

AIM: To compare different outcomes of vitrification and slow freezing of isolated pre-antral follicles and to evaluate different cryo-devices for vitrification of isolated follicles. METHODS: Pre-antral follicles were isolated from mouse ovaries and cryopreserved using vitrification and slow freezing. A preliminary experiment was carried out to select the optimal cryo-device for vitrification of isolated follicles. A total of 414 follicles were randomly distributed among four groups: control (CT) fresh (n=100), nylon mesh (n=96), electron microscopy grid (n=102), and micro-capillary tips (n=116). Subsequently, a total of 979 follicles were randomly assigned to three different groups: CT fresh (n=256), vitrification (n=399) and slow freezing (n=324). CT and cryopreserved/thawed follicles were cultured in vitro and examined daily for development. Final maturation was triggered with human chorionic gonadotrophin and rates of oocyte maturation were calculated. The ultra-structure of cryopreserved/thawed follicles was studied using electron microscopy. Meiotic spindle presence and organization in mature oocytes were examined using the Oosight imaging system. RESULTS: Micro-capillary tips resulted in poor immediate post-warming survival but no differences were observed in the subsequent in vitro development characteristics between different cryo-devices. Nylon mesh proved to be the easiest carrier, particularly when large numbers of follicles were to be vitrified. Compared to vitrification, slow freezing resulted in a significantly lower number of intact follicles at the end of the culture period (P<0.0001). However all other outcome measures were comparable between both techniques. CONCLUSIONS: Isolated follicles were more vulnerable to cryodamage after slow freezing as compared to vitrification.