Scalable and controllable synthesis of atomic metal electrocatalysts assisted by an egg-box in alginate

Herein, a general strategy is developed to synthesize atomic metal catalysts using sustainable and earth-abundant sodium alginate (Na-Alg), a common seaweed extract, as a precursor. The “egg-box” structure in Na-Alg after ion-exchange with metal cations (Zn2+, Co2+, Ni2+, Cu2+, etc.) is the key to achieve a scalable and controllable synthesis of highly dispersed atomic metals. For instance, atomic Co, Ni and Cu have been successfully synthesized using this method. As a representative, the as-synthesized atomically dispersed Co on reduced graphene oxide (A-Co/r-GO) can reach a maximum metal loading of 3.6 wt%, showing outstanding catalytic activity and stability for the oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.842 V vs. RHE that is more positive than that of 20 wt% Pt/C (0.827 V vs. RHE) in alkaline solutions. The A-Co/r-GO catalyzed zinc-air batteries (ZABs) outperform Pt/C-based ZABs in the aspects of discharge voltage and specific zinc capacity, and can work robustly for more than 250 h with negligible voltage loss with refueling the Zn anode and KOH electrolyte periodically. This work opens up a new strategy for a general, practical and scalable synthesis of atomic metal catalysts at very low cost.No Full Tex

Subinhibitory Concentrations of Thymol Reduce Enterotoxins A and B and α-Hemolysin Production in Staphylococcus aureus Isolates

BACKGROUND: Targeting bacterial virulence factors is now gaining interest as an alternative strategy to develop new types of anti-infective agents. It has been shown that thymol, when used at low concentrations, can inhibit the TSST-1 secretion in Staphylococcus aureus. However, there are no data on the effect of thymol on the production of other exotoxins (e.g., alpha-hemolysin and enterotoxins) by S. aureus. METHODOLOGY/PRINCIPAL FINDINGS: Secretion of alpha-hemolysin, SEA and SEB in both methicillin-sensitive and methicillin-resistant S. aureus isolates cultured with graded subinhibitory concentrations of thymol was detected by immunoblot analysis. Hemolysin and tumor necrosis factor (TNF) release assays were performed to elucidate the biological relevance of changes in alpha-hemolysin, SEA and SEB secretion induced by thymol. In addition, the influence of thymol on the transcription of hla, sea, and seb (the genes encoding alpha-hemolysin, SEA and SEB, respectively) was analyzed by quantitative RT-PCR. Thymol inhibited transcription of hla, sea and seb in S. aureus, resulting in a reduction of alpha-hemolysin, SEA and SEB secretion and, thus, a reduction in hemolytic and TNF-inducing activities. CONCLUSIONS/SIGNIFICANCE: Subinhibitory concentrations of thymol decreased the production of alpha-hemolysin, SEA and SEB in both MSSA and MRSA in a dose-dependent manner. These data suggest that thymol may be useful for the treatment of S. aureus infections when used in combination with beta-lactams and glycopeptide antibiotics, which induce expression of alpha-hemolysin and enterotoxins at subinhibitory concentrations. Furthermore, the structure of thymol may potentially be used as a basic structure for development of drugs aimed against these bacterial virulence factors

Self-assembling and pH-responsive protein nanoparticle as potential platform for targeted tumor therapy

Frequent injections at high concentrations are often required for many therapeutic proteins due to their short in vivo half-life, which usually leads to unsatisfactory therapeutic outcomes, adverse side effects, high cost, and poor patient compliance. Herein we report a supramolecular strategy, self-assembling and pH regulated fusion protein to extend the in vivo half-life and tumor targeting ability of a therapeutically important protein trichosanthin (TCS). TCS was genetically fused to the N-terminus of a self-assembling protein, Sup35p prion domain (Sup35), to form a fusion protein of TCS-Sup35 that self-assembled into uniform spherical TCS-Sup35 nanoparticles (TCS-Sup35 NP) rather than classic nanofibrils. Importantly, due to the pH response ability, TCS-Sup35 NP well retained the bioactivity of TCS and possessed a 21.5-fold longer in vivo half-life than native TCS in a mouse model. As a result, in a tumor-bearing mouse model, TCS-Sup35 NP exhibited significantly improved tumor accumulation and antitumor activity without detectable systemic toxicity as compared with native TCS. These findings suggest that self-assembling and pH responding protein fusion may provide a new, simple, general, and effective solution to remarkably improve the pharmacological performance of therapeutic proteins with short circulation half-lives