结核分枝杆菌重组Ag85A、Ag85B蛋白免疫原性的研究

目的研究结核分枝杆菌重组Ag85A（rAg85A）和/或Ag85B（rAg85B）蛋白与母牛分枝杆菌菌苗（Mycobacteri-um vaccae,MV）联合免疫的免疫原性。方法 60只雌性BALB/c小鼠随机分为下列6组：（1）阴性对照组：磷酸盐缓冲液（PBS）组,（2）阳性对照组：卡介苗（BCG）组,（3）阳性对照组：MV组,（4）实验组：rAg85A-MV组,（5）实验组：rAg85B-MV组及（6）实验组：rAg85A-rAg85B-MV组。每2周免疫1次,共免疫3次。末次免疫结束后第14天杀鼠,用ELISA法检测血清中IgGI、gG1和IgG2a水平;ELISPOT检测脾脏分泌γ干扰素（IFN-γ）的T淋巴细胞斑点数;流式细胞术检测全血单个核细胞内Th1和Th2百分比。结果三个实验组小鼠血清抗体水平均明显高于三个对照组（P〈0.001）;三个实验组和两个阳性对照组小鼠的T淋巴细胞斑点数均明显高于阴性对照组（P〈0.05）;rAg85A-rAg85B-MV组小鼠Th1百分比明显高于其余五组（P〈0.001）,三个实验组Th1/Th2比值均明显高于三个对照组（P〈0.05）。结论结核分枝杆菌rAg85A和rAg85B蛋白均具有很强的免疫原性,与MV联合免疫可增强其Th1型细胞免疫应答。     

The SARS-CoV-2 B.1.618 variant slightly alters the spike RBD–ACE2 binding affinity and is an antibody escaping variant: a computational structural perspective

Continuing reports of new SARS-CoV-2 variants have caused worldwide concern and created a challenging situation for clinicians. The recently reported variant B.1.618, which possesses the E484K mutation specific to the receptor-binding domain (RBD), as well as two deletions of Tyr145 and His146 at the N-terminal binding domain (NTD) of the spike protein, must be studied in depth to devise new therapeutic options. Structural variants reported in the RBD and NTD may play essential roles in the increased pathogenicity of this SARS-CoV-2 new variant. We explored the binding differences and structural-dynamic features of the B.1.618 variant using structural and biomolecular simulation approaches. Our results revealed that the E484K mutation in the RBD slightly altered the binding affinity through affecting the hydrogen bonding network. We also observed that the flexibility of three important loops in the RBD required for binding was increased, which may improve the conformational optimization and consequently binding of the new variant. Furthermore, we found that deletions of Tyr145 and His146 at the NTD reduced the binding affinity of the monoclonal antibody (mAb) 4A8, and that the hydrogen bonding network was significantly affected consequently. This data show that the new B.1.618 variant is an antibody-escaping variant with slightly altered ACE2–RBD affinity. Moreover, we provide insights into the binding and structural-dynamics changes resulting from novel mutations in the RBD and NTD. Our results suggest the need for further in vitro and in vivo studies that will facilitate the development of possible therapies for new variants such as B.1.618.

This study explored the binding patterns of the wild type and B.1.618 variant using which revealed that the B.1.618 variant possess a stronger binding affinity for the host ACE2 and escape the neutralizing antibodies.     

Ag–K/MnO2 nanorods as highly efficient catalysts for formaldehyde oxidation at low temperature

A series of Ag–K/MnO₂ nanorods with various molar ratios of K/Ag were synthesized by a conventional wetness incipient impregnation method. The as-prepared catalysts were used for the catalytic oxidation of HCHO. The Ag–K/MnO₂ nanorods with an optimal K/Ag molar ratio of 0.9 demonstrated excellent HCHO conversion efficiency of 100% at a low temperature of 60 °C. The structures of the samples were investigated by BET, TEM, SEM, XRD, H₂-TPR, O₂-TPD and XPS. The results showed that Ag–0.9K/MnO₂-r exhibited more facile reducibility and greatly abundant surface active oxygen species, endowing it with the best catalytic activity of the studied catalysts. This work provides new insights into the development of low-cost and highly efficient catalysts for the removal of HCHO.

Ag–K/MnO₂ nanorods with appropriate K/Ag ratio demonstrated excellent catalytic activity for complete oxidation of formaldehyde.     

Green syntheses of silver nanoparticle decorated reduced graphene oxide using l-methionine as a reducing and stabilizing agent for enhanced catalytic hydrogenation of 4-nitrophenol and antibacterial activity

Herein, we have reported a facile and green synthesis approach of Ag NP decorated reduced graphene oxide (RGO) through an in situ self-assembly method in the presence of l-methionine (l-Met) as reducing and stabilizing agent. The electronic properties, crystal structure, and morphology of the as-synthesized RGO–Ag nanocomposite were investigated by UV-Visible (UV-Vis) spectroscopy, Fourier transform-infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. UV-Vis and FTIR show the effective reduction of GO and the formation of Ag NPs using l-Met. FESEM, TEM, and XRD analysis show the successful impregnation of Ag NPs into RGO with a 23 nm average crystallite size. The RGO–Ag nanocomposite with NaBH₄ shows a fast-catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AMP). The enhanced catalytic activity of RGO–Ag nanocomposites can be attributed to the synergistic effect of improved adsorption capacity and the absence of agglomeration of Ag nanoparticles. Moreover, RGO–Ag showed strong antibacterial activity against B. subtilis and E. coli.

Herein, we have reported a facile and green synthesis approach of Ag NP decorated reduced graphene oxide (RGO) through an in situ self-assembly method in the presence of l-methionine (l-Met) as reducing and stabilizing agent.     

结核分枝杆菌Ag85A/MPT-64融合基因DNA疫苗的构建及免疫研究中ELISPOT技术的应用

目的构建结核分枝杆菌蛋白Ag85A/MPT-64融合基因为基础的DNA疫苗,并利用ELISPOT技术检测其免疫原性。方法利用PCR和基因克隆技术从结核分枝杆菌H37Rv基因组中扩增出Ag85A/MPT-64编码基因,构建真核表达载体,用酶切和双向DNA测序进行鉴定。鉴定正确的阳性克隆重组质粒,肌注免疫小鼠,3周后用ELISPOT法检测抗体滴度。结果 构建到真核载体中的结核分枝杆菌H37Rv株Ag85A/MPT-64融合基因经序列测定证实无突变。ELISPOT法检测几何平均滴度为1∶1 000。结论以Ag85A/MPT-64融合基因为基础的DNA疫苗的成功构建和表达以及ELISPOT技术的应用,为进一步研究其在结核病与肿瘤防治方面的作用奠定了基础。     

Coating metal–organic frameworks on plasmonic Ag/AgCl nanowire for boosting visible light photodegradation of organic pollutants

Photoactive metal–organic frameworks, MIL-100(Fe), with controllable thickness are coated on plasmonic Ag/AgCl nanowire, for boosting visible light photodegradation of rhodamine B and tetracycline hydrochloride. The morphology and composition of the obtained nano-heterostructure were investigated in detail by SEM imaging, TEM imaging, XRD patterns, FT-IR spectra, N₂ adsorption–desorption curves and TGA patterns. Photoelectric performance test suggested that a Z-scheme photocatalysis system for efficient transfer of photogenerated charge carriers was established between MIL-100(Fe) and plasmonic Ag/AgCl nanowire.

A photoactive metal–organic framework, MIL-100(Fe), with controllable thickness was coated on plasmonic Ag/AgCl nanowire for boosting the visible light photodegradation of rhodamine B and tetracycline hydrochloride.     

Photocatalytic activity and antibacterial properties of linen fabric using reduced graphene oxide/silver nanocomposite

Silver nanoparticles were in situ prepared on the surface of linen fabric coated by graphene oxide (GO). In the meantime, the reduction of silver nitrate on the GO-coated fabric led to the synthesis of reduced graphene oxide on the fabric. Two kinds of substrate (cotton and linen) were used. Both RGO/Ag and Ag/GO nanocomposites were added on cotton and linen fabrics through a conventional “pad–dry–cure” method. The chemistry and morphology of the coated surfaces were extensively characterized using Fourier-transformed infrared spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. Resistivity measurements were used for assessing the conductivity. The UV protection properties and the photocatalytic activity of the coated fabrics against methylene blue dye were also investigated. The antibacterial activity was studied against Gram-positive S. aureus and B. subtilis and Gram-negative bacterial strains E. coli and P. aeruginosa by determining the zone of inhibition using the agar diffusion method. Methicillin-resistant Staphylococcus aureus (MRSA) has been responsible for many serious hospital infections worldwide. The fabrics showed superior antibacterial activity and successfully hindered the growth of pathogenic bacterial strains. This outcome suggested that both the RGO/Ag and Ag/GO nanocomposites-coated fabrics could be potentially applied in biomaterials and biomedical fields.

Silver nanoparticles were in situ prepared on the surface of linen fabric coated by graphene oxide (GO).     

Synthesis of a novel resorcin[4]arene–glucose conjugate and its catalysis of the CuAAC reaction for the synthesis of 1,4-disubstituted 1,2,3-triazoles in water

The Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) in aqueous media using resorcin[4]arene glycoconjugate (RG) is reported. The eight β-d-glucopyranoside moieties constructed on the resorcin[4]arene upper rim provide a pseudo-saccharide cavity that offers a suitable host environment for water-insoluble hydrophobic azido and/or alkyne substrates in water. The utility of RG was established as an efficient inverse phase transfer catalyst for the CuAAC in water as a green approach for the synthesis of 1,4-disubstituted 1,2,3-triazole species. The catalytic utility of RG (1 mol%) was demonstrated in a multicomponent one-pot CuAAC for various azido/alkyne substrates. The RG acts as a molecular host and a micro-reactor resulting in the 1,4-disubstituted 1,2,3-triazoles in excellent yield.

The Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) in aqueous media using resorcin[4]arene glycoconjugate (RG) is reported.     

Green synthesis of bio-molecule encapsulated magnetic silver nanoparticles and their antibacterial activity

Persuaded by the necessity of finding new sources of antibiotics, silver nanoparticles (Ag NPs) were synthesized by adopting a newly developed green synthesis technique and subsequently, their antibacterial activity against different pathogenic bacteria was evaluated. We have successfully synthesized bio-molecule capped ferromagnetic Ag NPs with an average crystallite size of 13 nm using AgNO₃ solution as a precursor and Artocarpus heterophyllus leaf extract as a reducing and capping agent. The characterization of the synthesized Ag NPs was carried out using various techniques such as UV-visible (UV-Vis) spectroscopy, energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetry (TG), and vibrating sample magnetometer (VSM) analyses. After exposing the synthesized Ag NPs to two Gram-positive bacteria – Staphylococcus aureus and Bacillus cereus and two Gram-negative bacteria – Escherichia coli and Salmonella typhimurium, the zones of inhibition were found to be 15, 16, 19, and 18 mm, respectively. These results imply that the Artocarpus heterophyllus leaf extract mediated green synthesized bio-molecules encapsulated Ag NPs can be considered as a potential antibiotic against human pathogens which is very encouraging.

Persuaded by the necessity of finding new sources of antibiotics, Ag NPs were synthesized by adopting a newly developed green synthesis technique and subsequently, their antibacterial activity against different pathogenic bacteria was evaluated.     

Catalytic oxidation of ethyl acetate over LaBO3 (B = Co,Mn, Ni,Fe) perovskites supported silver catalysts

A series of silver catalysts supported on lanthanum based perovskites LaBO₃ (B = Co, Mn, Ni, Fe) were synthesized and evaluated in the catalytic oxidation of ethyl acetate. XRD, BET, TEM/HRTEM, HAADF-STEM, XPS and H₂-TPR were conducted, and the results indicate that redox activity of the catalysts is of great importance to the oxidation reaction. Activity tests demonstrated that Ag/LaCoO₃ was more active than the other samples in ethyl acetate oxidation. Moreover, the CO₂ selectivity, CO_x yields and byproduct distributions for all catalysts were studied, and Ag/LaCoO₃ showed the best catalytic performance. Besides, Ag/LaCoO₃ also showed excellent catalytic activity for other OVOCs.

Ag/LaBO₃ (B = Co, Mn, Ni, Fe) were investigated for the catalytic oxidation of ethyl acetate, and Ag/LaCoO₃ showed the best catalytic performance.     

Efficient NIR energy conversion of plasmonic silver nanostructures fabricated with the laser-assisted synthetic approach for endodontic applications

Silver nanoparticles were synthesized with the laser-assisted wet chemical approach at room temperature. The effect of light exposure on the silver nanoparticles'' spatial parameters shaping the localized surface plasmon resonance has been evaluated. The optical, structural and morphological characterizations of the Ag nanostructures were conducted with UV-VIS-NIR spectrophotometry, DLS and TEM techniques. The ability of the light-modified Ag nanostructures for energy conversion under the influence of 445 and 880 nm laser radiation is estimated. We have found that the most efficient heat generation can be achieved using triangular Ag nanostructures under the NIR irradiation (880 nm). The temperature effect on the Ag nanostructures'' antibacterial properties has been evaluated against the Staphylococcus aureus population. The prospects of triangular Ag nanostructures'' application on modern endodontics for the rapid nano-laser disinfection of the root canal system of the human tooth have been demonstrated.

Energy conversion by plasmonic silver nanostructures fabricated with the laser assisted synthetic approach at room temperature.     

Facile preparation of a Ag/graphene electrocatalyst with high activity for the oxygen reduction reaction

Small Ag nanoparticles are well dispersed onto graphene sheets via a simple and environmentally friendly route using disposable paper-cups. The obtained Ag/graphene materials exhibit much higher catalytic activity for the oxygen reduction reaction than the conventional Ag/graphene catalyst does in alkaline media.

Ag/graphene composite with small and well-dispersed Ag nanoparticles anchored onto the surface of graphene was prepared via a simple route from a disposal paper-cup, and exhibited superior electrocatalytic property for the oxygen reduction reaction.     

Blocking key mutated hotspot residues in the RBD of the omicron variant (B.1.1.529) with medicinal compounds to disrupt the RBD-hACE2 complex using molecular screening and simulation approaches

A new variant of SARS-CoV-2 known as the omicron variant (B.1.1.529) reported in South Africa with 30 mutations in the whole spike protein, among which 15 mutations are in the receptor-binding domain, is continuously spreading exponentially around the world. The omicron variant is reported to be highly contagious with antibody-escaping activity. The emergence of antibody-escaping variants is alarming, and thus the quick discovery of small molecule inhibitors is needed. Hence, the current study uses computational drug screening and molecular dynamics simulation approaches (replicated) to identify novel drugs that can inhibit the binding of the receptor-binding domain (RBD) with hACE2. Screening of the North African, East African and North-East African medicinal compound databases by employing a multi-step screening approach revealed four compounds, namely (−)-pipoxide (C1), 2-(p-hydroxybenzyl) benzofuran-6-ol (C2), 1-(4-hydroxy-3-methoxyphenyl)-2-{4-[(E)-3-hydroxy-1-propenyl]-2-methoxyphenoxy}-1,3-propanediol (C3), and Rhein (C4), with excellent anti-viral properties against the RBD of the omicron variant. Investigation of the dynamics demonstrates stable behavior, good residue flexibility profiles, and structural compactness. Validation of the top hits using computational bioactivity analysis, binding free energy calculations and dissociation constant (K_D) analysis also indicated the anti-viral properties of these compounds. In conclusion, this study will help in the design and discovery of novel drug therapeutics, which may be used against the emerging omicron variant of SARS-CoV-2.

A new variant of SARS-CoV-2 known as the omicron variant (B.1.1.529) reported in South Africa with 30 mutations in the whole spike protein, among which 15 mutations are in the receptor-binding domain, is continuously spreading exponentially around the world.     

Atomic oxygen effects on silvered polyimide films and their surface modification by poly(siloxane amic acid) ammonium salts

The tolerance of silvered polyimide films synthesized by an in situ self-metalization method against atomic oxygen (AO) was evaluated. The results showed that the mass loss of R–Ag/PI was markedly increased as the AO fluence increased; Ag/PI showed an identical trend. SEM data showed that the silver particles on the surfaces of R–Ag/PI and Ag/PI disappeared. The surfaces achieved a “carpet condition” that was more obvious as the AO fluence increased. Poly(siloxane amic acid) ammonium salt was synthesized and made via imidization to produce a flexible organic coating that was characterized by ATR-FTIR, ¹HNMR, TGA, and XPS. This could be used to improve the tolerance of silvered polyimide films against AO. The AO resistance and the impacts on mass loss, surface morphology, and surface compositions were also evaluated after surface modification by poly(siloxane amic acid) ammonium salts. 20 wt% Foc/Ag/PI had a lower mass loss and smoother surface than the others due to the formation of a compact surface-SiO₂-type layer. This flexible organic coating can be produced via an environmentally-friendly method, and it maintains the inherent thermal stability of the polyimide which cannot be achieved by other anti-AO coatings.

Poly(siloxane amic acid) ammonium salt with good AO resistance was synthesized, and used to protect silvered polyimide films from AO erosion.     

ZIF-8 derived Ag-doped ZnO photocatalyst with enhanced photocatalytic activity

Recently, zeolitic imidazolate framework-8 (ZIF-8) has been widely studied and used as a catalyst in various fields, due to its high specific surface area, tunable channels and thermal and chemical stability. In this paper, ZIF-8 was used as a precursor to fabricate a Ag/ZnO photocatalyst, and the influence of Ag on the photocatalytic activity of ZnO has been explored. All samples were characterised using XRD, SEM, TEM, and UV-vis diffuse reflectance spectra. The photocatalytic activity of all samples was evaluated by the degradation of a rhodamine B solution under UV light. The results show that ZIF-8 was completely transformed into ZnO when it was calcined at 550 °C for 6 h, and Ag was well loaded onto ZnO. The photocatalytic efficiency of ZnO is 92.32%. When ZnO was doped with Ag, its photocatalytic efficiency was highly improved (99.64%). Furthermore, Ag/ZnO exhibited high photocatalytic stability. After five repeated cycles, the photocatalytic activity of Ag/ZnO was highly retained at 97.48%.

In this paper, ZIF-8 was used as a precursor to fabricate a Ag/ZnO photocatalyst, and the influence of Ag on the photocatalytic activity of ZnO has also been explored.     

Design of a multi-epitope vaccine against SARS-CoV-2: immunoinformatic and computational methods

A novel infectious agent, SARS-CoV-2, is responsible for causing the severe respiratory disease COVID-19 and death in humans. Spike glycoprotein plays a key role in viral particles entering host cells, mediating receptor recognition and membrane fusion, and are considered useful targets for antiviral vaccine candidates. Therefore, computational techniques can be used to design a safe, antigenic, immunogenic, and stable vaccine against this pathogen. Drawing upon the structure of the S glycoprotein, we are trying to develop a potent multi-epitope subunit vaccine against SARS-CoV-2. The vaccine was designed based on cytotoxic T-lymphocyte and helper T-lymphocyte epitopes with an N-terminal adjuvant via conducting immune filters and an extensive immunoinformatic investigation. The safety and immunogenicity of the designed vaccine were further evaluated via using various physicochemical, allergenic, and antigenic characteristics. Vaccine-target (toll-like receptors: TLR2 and TLR4) interactions, binding affinities, and dynamical stabilities were inspected through molecular docking and molecular dynamic (MD) simulation methods. Moreover, MD simulations for dimeric TLRs/vaccine in the membrane-aqueous environment were performed to understand the differential domain organization of TLRs/vaccine. Further, dynamical behaviors of vaccine/TLR systems were inspected via identifying the key residues (named HUB nodes) that control interaction stability and provide a clear molecular mechanism. The obtained results from molecular docking and MD simulation revealed a strong and stable interaction between vaccine and TLRs. The vaccine''s ability to stimulate the immune response was assessed by using computational immune simulation. This predicted a significant level of cytotoxic T cell and helper T cell activation, as well as IgG, interleukin 2, and interferon-gamma production. This study shows that the designed vaccine is structurally and dynamically stable and can trigger an effective immune response against viral infections.

SARS-CoV-2 infections have spread throughout the world and became a rapidly emerging public health issue. The immunoinformatics approach was applied to design a potent multi-epitope vaccine against this deadly virus.     

Photocurable acrylate epoxy/ZnO–Ag nanocomposite coating: fabrication,mechanical and antibacterial properties

In this study, a UV-curable acrylate epoxy nanocomposite coating has been prepared by incorporation of ZnO–Ag hybrid nanoparticles. For this purpose, firstly ZnO–Ag hybrid nanoparticles were fabricated by a seed-mediated growth method. Then, these ZnO–Ag hybrid nanoparticles (2 wt%) were added into the UV-curable acrylate resin matrices. The photocuring process of nanocomposite was evaluated by various factors, such as the conversion of acrylate double bonds, pendulum hardness and gel fraction. Under the 4.8 s UV-exposure time for full crosslinking, the obtained data indicated that incorporation of ZnO–Ag nanohybrids into the coating matrix changed the crosslinking process of coating significantly. A mechanical teat indicated that the presence of nanohybrids in photocurable coating matrix enhanced its abrasion resistance from 98.7 to 131.6 L per mil (33.3%). The antibacterial test against E. coli over 7 h indicated that E. coli bacteria were killed totally by nanocomposite coating, whereas it was 2.6 × 10⁴ CFU mL⁻¹ for the neat coating without nanoparticles.

ZnO-Ag hybrid nanoparticles were fabricated by seed-mediated growth method and incorporated into the UV-curable acrylate resin matrice to form a composite. This improved the mechanical property of UV-cured coating and exhibited high antibacterial activity against E. coli.     

Facile synthesis of 1.3 nm monodispersed Ag nanoclusters in an aqueous solution and their antibacterial activities for E. coli

A facile one-pot strategy was developed to prepare ultrastable monodispersed Ag nanoclusters (NCs) in aqueous solution by using ISOBAM-104, as a stabilizing agent. The as-prepared Ag NCs with an average size of 1.3 nm, which can be preserved in water solution for more than one year under ambient conditions without obvious agglomeration, exhibited excellent antibacterial activities for E. coli (DH5α), compared to most of the previously reported results.

Ag NCs of 1.3 nm prepared by a facile one-pot strategy exhibit excellent antibacterial activities for E. coli.     

Electrospun composite nanofibre fabrics containing green reduced Ag nanoparticles as an innovative type of antimicrobial insole

In this study, polyvinyl alcohol (PVA) nanofibrous membranes containing silver nanoparticles (Ag NPs) were successfully fabricated by the combination of electrospinning and a green reduction approach. Through the electrospinning technique, uniform and smooth nanofibres can be obtained, and the Ag NPs with a narrow size distributions are well dispersed in PVA nanofibres. The investigation indicates that the mass ratio of reductant tea polyphenols and AgNO₃ play a crucial role in controlling the size of the Ag NPs. More importantly, multi-layered fabrics with a layer of PVA/Ag NP nanofibrous membrane layered onto cotton substrates were developed and applied to shoe insoles. The fabricated shoe insoles with functionalized PVA nanofibres exhibit remarkable antimicrobial activity against both E. coli and S. aureus (i.e. antibacterial rate > 99%). The creation of such an encouraging fabric could establish a new optimization methodology for producing nanoengineered functional textiles.

This study aims to develop an antimicrobial insole with an electrospun nanofibre mat which contains green reduced Ag NPs by a facile fabrication method.     

In situ fabrication of silver/polyimide composite films with enhanced heat dissipation

In this study, silver/polyimide (Ag/PI) composite films with enhanced heat dissipation properties were prepared. Ag was formed in situ by reducing AgNO₃ at various locations according to the reduction method. Two different types of soluble PIs capable of solution processing were used, namely Matrimid and hydroxy polyimide (HPI). Unlike Matrimid with bulky substituents, HPI with polar hydroxy groups formed ion–dipole interactions with Ag ions to form Ag particles with uniform size distribution. The location and distribution of Ag particles affect the heat emission characteristics of the composite films, resulting in better heat dissipation properties with the thermally and photochemically reduced Ag/HPI films having more Ag particles distributed inside of the films than the chemically reduced films.

The chemical structure and reduction method influence the Ag dispersion in Ag/PI nanocomposite films, resulting in different heat dissipation properties.