Facile synthesis of C-doped hollow spherical g-C3N4 from supramolecular self-assembly for enhanced photoredox water splitting

A facial, template-free and green strategy was developed to prepare C-doped hollow spherical g-C₃N₄ derived from supramolecular self-assembly of melamine, glucose and cyanuric acid. Especially, the precursors were tightly connected by hydrogen bonds, wherein glucose was served as a source of doped carbon. Spectroscopic and electrochemical analysis confirmed that the endmost nitrogen was replaced by the doped carbon to combine two melon parts, leading to the possible existence of the delocalized big π bonds in the system. Moreover, the GCN-x not only maintained the excellent properties of the hollow sphere, such as high surface area, moderate porosity and short charges diffusion distance, but also overcame the drawbacks of low visible light response and high electron-holes recombination rate from bulk g-C₃N₄. Thereby, the visible light utilization rate and the photogenerated electron-holes separation efficiency of the catalyst were improved. The highest hydrogen yield of 305  μmol h⁻¹ from GCN-0.2 was 28.5 times that of bulk g-C₃N₄. Finally, a possible mechanism underlying the photocatalytic performance of C-doped g-C₃N₄ hollow spheres was proposed tentatively.     

Fluorescence Correlation Spectroscopy Analysis of Effect of Molecular Crowding on Self-Assembly of β-Annulus Peptide into Artificial Viral Capsid

Recent progress in the de novo design of self-assembling peptides has enabled the construction of peptide-based viral capsids. Previously, we demonstrated that 24-mer β-annulus peptides from tomato bushy stunt virus spontaneously self-assemble into an artificial viral capsid. Here we propose to use the artificial viral capsid through the self-assembly of β-annulus peptide as a simple model to analyze the effect of molecular crowding environment on the formation process of viral capsid. Artificial viral capsids formed by co-assembly of fluorescent-labelled and unmodified β-annulus peptides in dilute aqueous solutions and under molecular crowding conditions were analyzed using fluorescence correlation spectroscopy (FCS). The apparent particle size and the dissociation constant (K_d) of the assemblies decreased with increasing concentration of the molecular crowding agent, i.e., polyethylene glycol (PEG). This is the first successful in situ analysis of self-assembling process of artificial viral capsid under molecular crowding conditions.     

Thermo- and pH-Responsive Polymersomes of Poly(α,β-N-substituted-DL-aspartamide)s

Materials that can respond to multiple stimuli, such as temperature and pH changes, are of considerable interest for applications in drug delivery systems. Notably, α,β-[poly(2-hydroxyethyl)-DL -aspartamide] is a potentially useful material for such applications. This study investigated the temperature and pH responsiveness of polymers structurally similar to α,β-[poly(2-hydroxyethyl)-DL -aspartamide], namely, poly(α,β-N-substituted-DL -aspartamide)s, in aqueous media. These polymers were derived from polysuccinimide (PSI), which was first synthesized via acid-catalyzed bulk polycondensation of L -aspartic acid (L-ASP) in the presence of 85% o-phosphoric acid under N2. Two primary amino alcohols, 4-aminobutanol (4AB) and 6-aminohexanol (6AH), were then respectively utilized to modify PSI to form poly (α,β-N-substituted-DL -aspartamide)s via aminolysis. Different ratios of these two amino alcohols were used to modify the polymer to produce a series of copolymers with lower critical solution temperatures ranging from 53–28°C when dispersed in aqueous media. Moreover, the properties of the poly(α,β-N- substituted-DL -aspartamide)s in aqueous solution were affected by pH changes. The morphology of the particles formed by these amphiphilic polymers was observed using scanning electronic microscopy and transmission electronic microscopy, and the particles were found to be polymersomes with shell and hollow core structures and diameters of 0.5–1 μm. Other properties of this series of self-assembly copolymers were also characterized. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhancing the Nucleolytic Resistance and Bioactivity of Functional Nucleic Acids by Diverse Nanostructures through in Situ Polymerization-Induced Self-assembly

Functional nucleic acids (FNAs) are garnering tremendous interest owing to their high modularity and unique bioactivity. Three-dimensional FNAs have been developed to overcome the issues of nuclease degradation and limited cell uptake. We have developed a new facile approach to the synthesis of multiple three-dimensional FNA nanostructures by harnessing photo-polymerization-induced self-assembly. Sgc8 aptamer and CpG oligonucleotide were modified as macro chain-transfer reagents to mediate in situ polymerization and self-assembly. Diverse structures, including micelles, rods, and short worms, afford these two FNAs afford these two FNAs with higher nuclease resistance in serum serum, greater cellular uptake efficiency, and increased bioactivity.     

α-氰基二苯乙烯类液晶研究进展

分类综述了α-氰基二苯乙烯类液晶的研究进展,包括氰基二苯乙烯棒状液晶、氰基二苯乙烯弓形液晶及氰基二苯乙烯多链形液晶,盘状液晶等。介绍了他们自组装成的多种液晶相及光电性质,以及对光、电、磁、压力等多种环境因素快速的响应性质。氰基二苯乙烯类液晶作为一种新型的荧光液晶材料,具有压敏效应、聚集发光效应及离子识别效应等,已成为当前人们重点研发的功能材料。     

Reversible Control of Gelatin Hydrogel Stiffness by Using DNA Crosslinkers**

Biomaterials with dynamically tunable properties are critical for a range of applications in regenerative medicine and basic biology. In this work, we show the reversible control of gelatin methacrylate (GelMA) hydrogel stiffness through the use of DNA crosslinkers. We replaced some of the inter-GelMA crosslinks with double-stranded DNA, allowing for their removal through toehold-mediated strand displacement. The crosslinks could be restored by adding fresh dsDNA with complementary handles to those on the hydrogel. The elastic modulus (G’) of the hydrogels could be tuned between 500 and 1000 Pa, reversibly, over two cycles without degradation of performance. By functionalizing the gels with a second DNA strand, it was possible to control the crosslink density and a model ligand in an orthogonal fashion with two different displacement strands. Our results demonstrate the potential for DNA to reversibly control both stiffness and ligand presentation in a protein-based hydrogel, and will be useful for teasing apart the spatiotemporal behavior of encapsulated cells.     

Layer-by-layer self-assembly of multifunctional enzymatic UF membranes

In order to eliminate membrane fouling and to ensure enzymatic hydrolysis of urea, multifunctional biocatalytic membranes were prepared by using urease (URE) and trypsin (TRY) enzymes on the sulfonated polysulfone (SPSf) ultrafiltration membrane via layer-by-layer (LbL) self-assembly method. The membrane architecture consisted of multilayer assembly with TRY and URE enzymes as the outer layer and inner sandwiched layer, respectively. Polyethyleneimine (PEI) and alginate (ALG) were used as cationic and anionic polyelectrolytes. Sulfonation and PEI deposition were successfully accomplished as confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy analysis, contact angle measurements, staining with toluidine blue and Congo red dyes and dead-end filtration experiments. A characteristic value of SPSf membrane with a high water permeability (1000 L/m².h.bar) and 95% bovine serum albumin (BSA) rejection was observed. In static conditions, URE activities of SPSf2-PEI-URE membrane were not affected by BSA fouling, while TRY immobilizations with increased concentrations (SPSf2-PEI-URE-PEI-ALG-TRY) significantly lowered the activity of URE. In dynamic conditions, each deposited layer exhibited individual resistance to flow that can be considered as irreversible fouling and caused 90% of flux decline for the SPSf2-PEI-URE-PEI-ALG-TRY membrane assembly. The recovery of the initial flux for the multilayered membrane at the end of six fouling and washing cycles was observed 85%. Moreover, at the end of 5 cycles, 78% of the URE initial activity of the multilayered membrane was preserved. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48750.     

On control of transport in Brownian ratchet mechanisms

Engineered transport of material at the nano/micro scale is essential for the manufacturing platforms of the future. Unlike conventional transport systems, at the nano/micro scale, transport has to be achieved in the presence of fundamental sources of uncertainty such as thermal noise. Remarkably, it is possible to extract useful work by rectifying noise using an asymmetric potential; a principle used by Brownian ratchets. In this article a systematic methodology for designing open-loop Brownian ratchet mechanisms that optimize velocity and efficiency is developed. In the case where the particle position is available as a measured variable, closed loop methodologies are studied. Here, it is shown that methods that strive to optimize velocity of transport may compromise efficiency. A dynamic programming based approach is presented which yields up to three times improvement in efficiency over optimized open loop designs and 35% better efficiency over reported closed loop strategies that focus on optimizing velocities.     

Emerging Plasmonic Assemblies Triggered by DNA for Biomedical Applications

Plasmonic gold nanocrystal represents plasmonic metal nanomaterials, and has a variety of unique and beneficial properties, such as optical signal enhancement, catalytic activity, and photothermal properties tuned by local temperature, which are useful in physical, chemical, and biological applications. In addition, the inherent properties of predictable programmability, sequence specificity, and structural plasticity provide DNA nanostructures with precise controllability, spatial addressability, and targeting recognition, serving as ideal ligands to link or position building blocks during the self-assembly process. Self-assembly is a common technique for the organization of prefabricated and discrete nanoparticle blocks for the construction of extremely sophisticated nanocomposites. To this end, the integration of DNA nanotechnology with Au nanomaterials, followed by assembly of DNA-functionalized Au nanomaterials can form novel functional Au nanomaterials that are difficult to obtain through conventional methods. Here, recent progress in DNA-assembled Au nanostructures of various shapes is summarized, and their functions are discussed. The fabrication strategies that employ DNA for the self-assembly of Au nanostructures, including dimers, tetramers, satellites, nanochains, and other nanostructures with more complex geometric configurations are first described. Then, the characteristic optical properties and applications of biosensing, bioimaging, drug delivery, and therapy are discussed. Finally, the remaining challenges and prospects are elucidated.     

Porous polyurethane film fabricated via the breath figure approach for sustained drug release

The breath figure (BF) method is an effective process for fabricating porous polymeric films. In this study, we fabricated porous polymer films from thermoplastic polyurethane (PU) through static BF with CHCl₃ as a solvent under 55–80% relative humidity. The porous PU films were prepared within various pore structures and sizes, which were adjustable, depending on the fabrication conditions. The humidity and exposure time were examined as variable parameters affecting the surface morphology, wettability, and cytotoxicity. Atorvastatin calcium, a hyperlipidemic agent, was loaded into the porous films during the casting process, and the drug-loading and drug-releasing behaviors of the porous PU membranes were evaluated. Approximately 60–80% of the drug was released in 14 days. The films exhibited sustained drug-release performances because of the hydrophobicity and nonbiodegradable nature of PU for perivascular drug administration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47658.