Vascular Cell Co-Culture on Silk Fibroin Matrix.

Silk fibroin (SF), a natural polymer material possessing excellent biocompatibility and biodegradability, and has been widely used in biomedical applications. In order to explore the behavior of vascular cells by co-culturing on regenerated SF matrix for use as artificial blood vessels, human aorta vascular smooth muscle cells (HAVSMCs) were co-cultured with human arterial fibroblasts (HAFs) or human umbilical vein endothelial cells (HUVECs) on SF films and SF tubular scaffolds (SFTSs). Analysis of cell morphology and deoxyribonucleic acid (DNA) content showed that HUVECs, HAVSMCs and HAFs adhered and spread well, and exhibited high proliferative activity whether cultured alone or in co-culture. Immunofluorescence and scanning electron microscopy (SEM) analysis showed that HUVECs and HAFs co-existed well with HAVSMCs on SF films or SFTSs. Cytokine expression determined by reverse transcription-polymerase chain reaction (RT-PCR) indicated that the expression levels of α-smooth muscle actin (α-SMA) and smooth muscle myosin heavy chain (SM-MHC) in HAVSMCs were inhibited on SF films or SFTSs, but expression could be obviously promoted by co-culture with HUVECs or HAFs, especially that of SM-MHC. On SF films, the expression of vascular endothelial growth factor (VEGF) and platelet endothelial cell adhesion molecule-1 (CD31) in HUVECs was promoted, and the expression levels of both increased obviously when co-cultured with HAVSMCs, with the expression levels of VEGF increasing with increasing incubation time. The expression levels of VEGF and CD31 in cells co-cultured on SFTSs improved significantly from day 3 compared with the mono-culture group. These results were beneficial to the mechanism analysis on vascular cell colonization and vascular tissue repair after in vivo transplantation of SFTSs.

The effect of hirudin modification of silk fibroin on cell growth and antithrombogenicity.

Thrombus formation remains a particular challenge for small-diameter vascular grafts. In this study, the direct thrombin inhibitor hirudin (Hir) was used to modify silk fibroin films in an attempt to enhance its antithrombogenic properties. Hir was successfully attached to silk fibroin and uniformly distributed in the regenerative material. Hir-modified films showed good cytocompatibility, and supported adhesion and proliferation of fibroblasts (L929), human umbilical vascular endothelial cells (HUVECs) and human aortic smooth muscle cells (HASMCs). Proliferation of HAVSMCs was inhibited by increasing Hir concentration. Activated partial thrombin time (APTT), prothrombin time (PT) and thrombin time (TT) of Hir-modified silk fibroin tubular scaffolds (SFTSs) were all increased markedly compared with fresh rabbit blood, ethanol-treated SFTS and unmodified SFTS, demonstrating the improved antithrombogenicity of SFTSs following modification with Hir.

High-Performance Li-O2 Batteries with Controlled Li2O2 Growth in Graphene/Au-Nanoparticles/Au-Nanosheets Sandwich.

The working of nonaqueous Li-O2 batteries relies on the reversible formation/decomposition of Li2O2 which is electrically insulating and reactive with carbon and electrolyte. Realizing controlled growth of Li2O2 is a prerequisite for high performance of Li-O2 batteries. In this work, a sandwich-structured catalytic cathode is designed: graphene/Au-nanoparticles/Au-nanosheets (G/Au-NP/Au-NS) that enables controlled growth of Li2O2 spatially and structurally. It is found that thin-layer Li2O2 (below 10 nm) can grow conformally on the surface of Au NPs confined in between graphene and Au NSs. This unique crystalline behavior of Li2O2 effectively relieves or defers the electrode deactivation with Li2O2 accumulation and largely reduces the contact of Li2O2 with graphene and electrolyte. As a result, Li-O2 batteries with the G/Au-NP/Au-NS cathode exhibit superior electrochemical performance. A stable cycling of battery can last 300 times at 400 mA g-1 when the capacity is limited at 500 mAh g-1. This work provides a practical design of catalytic cathodes capable of controlling Li2O2 growth.

Au-nanocrystals-decorated δ-MnO2 as an efficient catalytic cathode for high-performance Li-O2 batteries.

A Li-O2 battery works based on the reversible formation and decomposition of Li2O2, which is insulating and highly reactive. Designing a catalytic cathode capable of controlling Li2O2 growth recently became a challenge to overcome this barrier. In this work, we present a new design of catalytic cathode by growing porous Au/δ-MnO2 electrocatalyst directly on a conductive substrate. We found that Au/δ-MnO2 can catalyze the directed growth of Li2O2 into a thin/small form, only inside porous δ-MnO2, and along the surface of δ-MnO2 sheets. We proposed the catalytic mechanism of Au/δ-MnO2, where Au plays a critical role in catalyzing the nucleation, crystallization and conformal growth of Li2O2 on δ-MnO2 sheets. Li-O2 batteries with an Au/δ-MnO2 catalytic cathode showed excellent electrochemical performance due to this favorable Li2O2 growth habit. The battery yielded a high capacity of 10,600 mA h g(-1) with a low polarization of 0.91 V at 100 mA g(-1). Superior cycling stability could be achieved in both capacity-limited (500 mA h g(-1), 165 times at 400 mA g(-1)) and unlimited (ca. 3000 mA h g(-1), 50 cycles at 800 mA g(-1)) modes.

Correlation between composition and hydrogen storage behaviors of the Li2NH-MgNH combination system.

Hydrogen storage performances of a Li(2)NH-xMgNH combination system (x = 0, 0.5, 1 and 2) are investigated for the first time. It is found that the hydrogenated samples with MgNH exhibit a significant reduction in the dehydrogenation temperatures. Mechanistic investigations reveal that there is a strong dependence of the hydrogen storage reaction process on the molar ratio between MgNH and Li(2)NH. As a consequence, tuning of thermodynamics is achieved for hydrogen storage in the Li(2)NH-xMgNH system by changing the reaction routes, which is ascertained to be the primary reason for the reduction in the operating temperature for hydrogen desorption. Specifically, it is found that under 105 atm hydrogen (140-280 °C) 5.6 wt% hydrogen is reversibly stored in the Li(2)NH-0.5MgNH combination system, which is greater than in the well-investigated Mg(NH(2))(2)-2LiH system.