Theoretical study on the reaction of NbS^+(~3∑^-,~1Γ) with CO

Two possible reactions of NbS＋ （3∑^-, 1Г） with CO in the gas phase have been studied by using B3LYP and CCSD（T） methods： the O/S exchange reaction （NbS^＋ ＋ CO → NbO^＋ ＋ CS） and the S-transfer reaction （NbS＋ ＋ CO → Nb^＋ ＋ COS）. The two reactions have a one-step mechanism. The barriers of the O/S exchange reaction on the triplet and singlet surfaces are 51.2 and 52.4 kcal/mol, respectively, and the barriers of the S-transfer reaction are 58.3 and 78.0 kcal/mol, respectively. The results indicate that the Stransfer and the O/S exchange reaction of the 3∑^- ground state of NbS＋ are competing, but, for the S-transfer reaction, the 1F exited state is more reactive. The differences between the reactions of NbS＋ （3∑^_, 1Г） and VS＋ （3∑^_, 1Г） are discussed.

Oxygen microcapsules improve immune checkpoint blockade by ameliorating hypoxia condition in pancreatic ductal adenocarcinoma

Rationale:Hypoxia in tumor microenvironment(TME)represents an obstacle to the efficacy of immunotherapy for pancreatic ductal adenocarcinoma(PDAC)through several aspects such as increasing the expression of immune checkpoints or promoting fibrosis.Reversing hypoxic TME is a potential strategy to improve the validity of immune checkpoint blockade(ICB).Methods:Here,we synthesized polydopamine-nanoparticle-stabilized oxygen microcapsules with excellent stabilization,bioavailability,and biocompatibility for direct oxygen delivery into tumor sites by interfacial polymerization.Results:We observed oxygen microcapsules enhanced the oxygen concentration in the hypoxia environment and maintained the oxygen concentration for a long period both in vitro and in vivo.We found that oxygen microcapsules could significantly improve the efficiency of ICB against PDAC in vivo.Mechanismly,combined treatments using oxygen microcapsules and ICB could reduce the infiltration of tumor-associated macrophages(TAMs)and polarized pro-tumor M2 macrophages into anti-tumor M1 macrophages.In addition,combined treatments could elevate the proportion of T helper subtype 1 cells(Th1 cells)and cytotoxic T lymphocytes cells(CTLs)to mediate anti-tumor immune response in TME.Conclusion:In summary,this pre-clinical study indicated that reversing hypoxia in TME by using oxygen microcapsules was an effective strategy to improve the performances of ICB on PDAC,which holds great potential for treating PDAC in the future.

Synergetic treatment of oxygen microcapsules and lenvatinib for enhanced therapy of HCC by alleviating hypoxia condition and activating anti-tumor immunity

Hypoxia is a typical characteristic of hepatocellular carcinoma(HCC), which causes tremendous obstacles to tumor treatments. Current first-line treatment may further deteriorate tumor hypoxia. For example,Lenvatinib, a receptor tyrosine kinase inhibitor(RTKI), suppresses tumor growth via blocking vascular endothelial growth factor(VEGF) signaling, and can also inhibit angiogenesis, thus limiting oxygen supply to tumor sites. Therefore, alleviating tumor microenvironment(TME) hypoxia holds great potential for enhancing the therapeutic effect of RTKI. Here, nanoparticle-stabilized oxygen microcapsules, a stable and biocompatible oxygen-loaded delivery system, are successfully prepared through interfacial polymerization of polydopamine nanoparticles. The microcapsules with a large loading capacity of oxygen in the core show excellent bioavailability and dispersity, which could effectively improve the hypoxic TME when they serve as oxygen delivery vehicles. Synergetic treatments of Lenvatinib and oxygen microcapsules could induce the transition of “cold tumor” in an immune-suppressed state to “hot tumor” in an immune-activated state by improving tumor hypoxic TME and reducing angiogenesis in HCC. It is revealed that combined treatments of oxygen microcapsules and Lenvatinib could polarize tumor-associated macrophages(TAMs) to anti-tumor M1 cells and activate T cell-mediated anti-tumor immune responses.The results suggest that synergetic therapy using oxygen microcapsules and Lenvatinib could alleviate the hypoxic TME and enhance the therapeutic performance of RTKI, demonstrating a promising anti-tumor strategy for enhanced therapy of HCC.

Competitive polycondensation of model compound melamine-urea-formaldehyed(MUF)resin system by^(13)C NMR

Melamine-urea-formaldehyde(MUF)resin is an excellent adhesive in the field of wood adhe-sives,however the competition mechanism is questionable which affects the structure control and performance optimization of the resin.In this study,the competitive resin synthesis poly-condensation reaction of MUF system under alkaline condition was studied based on the model compound 1,3-dihydroxymethyl urea(UF_(2))and melamine(M)system,and the competitive reac-tion mechanism in the system was deduced by^(13)C NMR quantitative analysis.The results show that the energy barrier of hydroxymethylation of melamine is lower than that of urea,and the priority of hydroxymethylation is lower;the addition of melamine results in a large amount of hy-drolysis of UF_(2),and the formed free formaldehyde,resulting in hydroxymethylation of melamine;there is obvious polycondensation reaction in UF_(2)+M system,mainly from the relationship be-tween hydroxymethylurea and melamine or hydroxymethylmelamine.The type I bridge bond structure of polycondensation mainly comes from the reaction of UF_(2) and M,which is difficult to form the type II bridge bond.At low molar ratio,the formation of bridge bond is superior to that of ether bond.With the increase of molar ratio,the formation of ether bond shows advantages,but there is obvious competition between them.There may be competitive presence of the UF self-condensation products,melamine-formaldehyde(MF)self-condensation products and MUF co-condensed products after the polycondensation reaction.