Modular Ligation of Thioamide Functional Peptides onto Solid Cellulose Substrates

Hetero Diels‐Alder (HDA) cycloaddition – as an effective modular conjugation approach – is employed to graft thioamide endfunctional oligopeptides onto solid cyclopentadienyl (Cp) functional cellulose substrates generating cellulose‐peptide hybrid materials. The highly reactive Cp moieties serve as diene functionality in the consecutive HDA reaction on the biosubstrate surface. Oligopeptides (i.e., the model peptide Gly‐Gly‐Arg‐Phe‐Pro‐Trp‐Trp‐Gly and the antimicrobial peptide tritrpticin) are functionalized at their N‐termini employing strongly electron deficient thiocarbonyl thio compounds resulting in biomacromolecules bearing a thioamide endgroup. The dienophile‐ functional peptides readily undergo HDA reactions at ambient temperature and under mild conditions in solution with synthetic polymers as well as on solid (bio)substrates. An in‐depth investigation is provided of the influence of the temperature, the Lewis acid catalysis and the side group exchange of thioamide functional oligopeptides reacting with Cp terminated poly(methyl methacrylate) (M_n = 2100 g·mol^?1, PDI = 1.1) in homogenous solution as well as Cp functionalized cellulose in a heterogeneous system. To assess the success of the grafting reaction, the soluble samples were subjected to characterization methods such as size exclusion chromatography (SEC) and SEC‐electrospray ionization mass spectrometry (SEC‐ESI‐MS). The heterogeneous “grafting‐to” reactions were monitored using high resolution attenuated total reflection (ATR) Fourier transform infrared microscopy (HR‐FTIRM) imaging, X‐ray photoelectron spectroscopy (XPS) and elemental analysis. Evaluation via elemental analysis leads to quantitative peptide cellulose surface loading capacities.     

端羟基聚环氧氯丙烷醚的合成及表征

采用乳液双金属氰化物络合物代替Lewis酸类作为催化剂,使环氧氯丙烷(ECH)开环聚合,制得相对分子质量较高及分子质量分布较窄的聚环氧氯丙烷(PECH),这种PECH可用于高质量的含能叠氮粘合剂中。研究了影响ECH聚合的一些关键因素,包括引发剂的类型及用量,单体的加料方式及催化剂用量等。实验结果表明,PECH的官能度随引发剂的种类而变。而增加催化剂用量及提高反应温度,则可增大PECH的相对分子质量。另外,连续地逐滴加入单体比一次性加入单体较优。当以双酚A为引发剂,催化剂用量为生成PECH量的0.05%,反应温度为128℃时,PECH的收率可大于95%,所得PECH的官能度为2～3,PECH的结构由IR、1HNMR及GPC确认。     

电子浆料用超微细玻璃粉的等离子体改性

以六甲基二硅氧烷为单体,利用高频等离子体在超微细低熔磷酸盐玻璃粉体表面聚合硅氧聚合物包覆薄膜。用水和粉体压片之间的接触角变化表征了等离子体工艺参数对粉体表面能的影响。结果表明改性后粉体配制电子浆料的细度、黏度、流变特性提高显著。改性后可以改变或控制超微细粉体的表面能大小,从而可调节电子浆料的流变性和印刷适性。     

A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands

Controlled Suzuki–Miyaura coupling polymerization of 7′‐bromo‐9′,9′‐dioctyl‐fluoren‐2′‐yl‐4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolane initiated by bromo(4‐tert‐butoxycarbonylamino‐phenyl)(tri‐tert‐butylphosphine)palladium ( 1 ) or bromo(4‐diethoxyphosphoryl‐phenyl)(tri‐tert‐butylphosphine)palladium ( 2 ) yields functionalized polyfluorenes (M_n = 4 × 10³ g mol^?1, M_w/M_n < 1.2) with a single amine or phosphonic acid, respectively, end‐group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution σ < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino‐functionalized polyfluorene ligands. Single particle micro‐photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot.     

Superparamagnetic Twist‐Type Actuators with Shape‐Independent Magnetic Properties and Surface Functionalization for Advanced Biomedical Applications

Directed nanoparticle self‐organization and two‐photon polymerization are combined to enable three‐dimensional soft‐magnetic microactuators with complex shapes and shape‐independent magnetic properties. Based on the proposed approach, single and double twist‐type swimming microrobots with programmed magnetic anisotropy are demonstrated, and their swimming properties in DI‐water are characterized. The fabricated devices are actuated using weak rotating magnetic fields and are capable of performing wobble‐free corkscrew propulsion. Single twist‐type actuators possess an increase in surface area in excess of 150% over helical actuators with similar feature size without compromising the forward velocity of over one body length per second. A generic and facile combination of glycine grafting and subsequent protein immobilization exploits the actuator's increased surface area, providing for a swimming microrobotic platform with enhanced load capacity desirable for future biomedical applications. Successful surface modification is confirmed by FITC fluorescence.     

A Biodegradable Antigen Nanocapsule Promotes Anti-Tumor Immunity via the cGAS-STING Pathway

Materials-based antigen delivery systems can augment the immune response by improving antigen uptake in antigen-presenting cells, targeting lymph nodes, prolonging antigen exposure, enhancing cross-presentation, etc. Recent research revealed that some antigen carriers activate the innate immune pathways without additional adjuvant. Here, a vaccine delivery platform (antigen nanocapsules) constructed by a one-step in situ polymerization is reported, weaving a biodegradable polymer network around the antigen surface. This simple technology allowed us to study the immunomodulatory effect of various antigen carriers. An antigen nanocapsule (NC7) capable of inducing dendritic cell activation and cross-presentation is identified. Further mechanistic studies revealed that NC7 activated the cGAS-STING pathway in a cGAS-dependent manner. Moreover, the subcutaneously injected NC7 accumulated in the lymph nodes and elicited strong cytotoxic T cell immunity and T cell memory against established cancer. Collectively, the often-neglected immunomodulatory effect of various cationic antigen carriers, enabling potential application in cancer vaccines, is uncovered.     

A Facile Strategy for Preparing Self‐Healing Polymer Composites by Incorporation of Cationic Catalyst‐Loaded Vegetable Fibers

A two‐component healing agent, consisting of epoxy‐loaded microcapsules and an extremely active catalyst (boron trifluoride diethyl etherate, (C₂H₅)₂O · BF₃)), is incorporated into epoxy composites to provide the latter with rapid self‐healing capability. To avoid deactivation of the catalyst during composite manufacturing, (C₂H₅)₂O · BF₃ is firstly absorbed by fibrous carriers (i.e., short sisal fibers), and then the fibers are coated with polystyrene and embedded in the epoxy matrix together with the encapsulated epoxy monomer. Because of gradual diffusion of the absorbed (C₂H₅)₂O · BF₃ from the sisal into the surrounding matrix, the catalyst is eventually distributed throughout the composites and acts as a latent hardener. Upon cracking of the composites, the epoxy monomer is released from the broken capsules, spreading over the cracked planes. As a result, polymerization, triggered by the dispersed (C₂H₅)₂O · BF₃, takes place and the damaged sites are rebonded. Since the epoxy–BF₃ cure belongs to a cationic chain polymerization, the exact stoichiometric ratio of the reaction components required by other healing chemistries is no longer necessary. Only a small amount of (C₂H₅)₂O · BF₃ is sufficient to initiate very fast healing (e.g., a 76% recovery of impact strength is observed within 30 min at 20 °C).     

Photothermally Sensitive Poly(N‐isopropylacrylamide)/Graphene Oxide Nanocomposite Hydrogels as Remote Light‐Controlled Liquid Microvalves

A photothermally sensitive poly(N‐isopropylacrylamide)/graphene oxide (PNIPAM/GO) nanocomposite hydrogel can be synthesized by in situ γ‐irradiation‐assisted polymerization of an aqueous solution of N‐isopropylacrylamide monomer in the presence of graphene oxide (GO). The colors and phase‐transition temperatures of the PNIPAM/GO hydrogels change with different GO doping levels. Due to the high optical absorbance of the GO, the nanocomposite hydrogel shows excellent photothermal properties, where its phase transitions can be controlled remotely by near‐infrared (NIR) laser irradiation, and it is completely reversible via laser exposure or non‐exposure. With a higher GO loading, the NIR‐induced temperature of the nanocomposite hydrogel increases more quickly than with a lower doping level and the temperature can be tuned effectively by the irradiation time. The nanocomposite hydrogel with its excellent photothermal properties will have great applications in the biomedical field, especially as microfluidic devices; this has been demonstrated in our experiments by way of remote microvalves to control fluidic flow. Such an “easy” and “clean” synthetic procedure initiated by γ‐irradiation can be extended for the efficient synthesis of other nanocomposite materials.