Electrostatic assembly of calf thymus DNA on multi-walled carbon nanotube modified gold electrode and its interaction with chlorpromazine hydrochloride

The electrostatic assembly of calf thymus DNA on multi-walled carbon nanotubes (MWNTs)-modified gold electrode via poly(diallyldimethylammonium chloride) (PDDA), a cationic polyelectrolyte, has been studied. Piezoelectric quartz crystal impedance (PQCI) technique was employed to monitor the assembly of DNA in real time. Electrochemical impedance spectroscopy was also used to characterize the modification process. It has been found that modification of the electrode with MWNTs has significantly enhanced the effective electrode surface area in addition to providing negatively charged groups for the electrostatic assembly of cationic polyelectrolyte. PDDA plays a key role in the attachment of DNA to MWNTs and acts as a bridge to connect DNA with MWNTs, though the direct adsorption of DNA on MWNTs has been observed. Moreover, the interaction between DNA and chlorpromazine hydrochloride was observed with PQCI technique. This shows that DNA assembled on MWNTs still has the ability to interact with drug molecules, which has great importance in the construction of new types of miniature DNA biosensors.     

DNA-protein noncovalent cross-linking: ruthenium dipyridophenazine biotin complex for the assembly of proteins and gold nanoparticles on DNA templates

We report the first example of a small molecule that can noncovalently cross-link DNA with streptavidin and streptavidin-labeled materials. Molecule 1 possesses a ruthenium dipyridophenazine DNA-intercalating moiety and a biotin unit; these two units are adequately separated to ensure efficient cross-linking of DNA with protein. Complex 1 is essentially nonemissive in aqueous solution and when bound to streptavidin, however, its luminescence is turned "on" when it binds to DNA. We have used these properties to establish that this complex can simultaneously bind to DNA and streptavidin, and can thus bring these two biomolecules together. We also synthesized a related molecule, 3, in which the biotin and DNA-intercalating moieties are covalently bound. While complex 3 can intercalate into DNA through a threading mechanism, luminescence experiments show that it cannot simultaneously bind DNA and streptavidin, most likely due to the proximity of its two molecular-recognition units. The cross-linking ability of molecule 1 was used to template the assembly of streptavidin molecules on circular plasmid DNA, as visualized by atomic force microscopy. In addition, using 1, we show the organization of discrete groups of gold nanoparticles labeled with streptavidin on a linear DNA template of finite size, with transmission electron microscopy. In these experiments the DNA template acted as a "molecular ruler" that dictated the number of particles in the assembly.     

Synthesis and comparison of crosslinked peptide nanoparticles based on diphenylalanine derivatives

Self‐assembly is a mechanism that creates novel nanomaterials with amplified properties but with stability challenges. In this report, highly stable and biocompatible anionic zwitterionic diphenylalanine nanoparticles (ZFFNPs), which are novel for the literature, are demonstrated. ZFF was crosslinked with glutaraldehyde (GA) and self‐assembled into nanoparticles in a self‐assembly mechanism like that for diphenylalaninamide nanoparticles (FFANPs). Also, ZFFNPs were compared with FFANPs in aspects of morphology, surface charge, stability, and cytotoxicity. ZFFNPs demonstrate a spherical morphology and homogenicity like FFANPs, but while ZFFNPs have negative surface groups (carboxyl), FFANPs contain polar surface groups (amide). While ZFFNPs exhibit a high stability in extremely acidic environments (pH 3–5), AFFNPs show stability in a wide pH range (pH 4–10). Both NPs are nontoxic and biocompatible. These novel anionic ZFFNPs have great promise for potential utilization in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45930.     

Investigation of F?rster Resonance Energy Transfer (FRET) and Competition of Fluorescent Dyes on DNA Microparticles

Fluorescent labeling is widely used to investigate the structural stability and changes to DNA nano- and microstructures. Despite this, the conventional method for observing DNA structures has several limitations in terms of cost-efficiency. This paper introduces a DNA spherical particle stained with DNA intercalating dyes (SYBR Green and SYTOX Orange) as tracers and reports the interaction between multiple dyes. The interference between the dyes was analyzed in terms of Förster resonance energy transfer (FRET) and competition. The changes in the fluorescence intensity by FRET were uniform, regardless of the sequence. The competition effect could occur when several dyes were added simultaneously. These properties are expected to help in the design of multicolor tracers in bioimaging and environmental applications.     

Synthesis of a novel polymer cholesterol‐poly(ethylene glycol) 2000‐glycyrrhetinic acid (chol‐PEG‐GA) and its application in brucine liposome

In this research, a novel polymer cholesterol‐poly(ethylene glycol) 2000‐glycyrrhetinic acid (Chol‐PEG‐GA) was synthesized with four steps of chemical modification and elucidated by FTIR and ¹H‐NMR spectra. To demonstrate the application of this Chol‐PEG‐GA in preparation of liposomes (CPGL), conventional liposome (CL) composed of PC and Chol was prepared and the effects of the quantity of Chol‐PEG‐GA on the physicochemical properties (entrapment efficiency, particle size, stability of storage, and so on) of CPGL were also evaluated. The ability of the sustained release and the liver targeting ability of CPGL were further studied in vivo in rats and mice. The results show that, the AUC and MRT of CPGL were increased 2.31 and 2.11 times when compared with CL, respectively. The CPGL delivered about seven times higher drug into liver as compared with CL. From the targeting parameters of CPGL and CL, we can also conclude that the CPGL is able to improve the liver targeting of brucine. All these results suggested that, the Chol‐PEG‐GA modified liposomes were potential as the sustained and liver targeting drug delivery. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on self‐assembly interactions of proteins and octenyl succinic anhydrate (OSA)‐modified depolymerized waxy rice starch using rheological principles

Dynamic tests (23 °C, pH ～ 7.0) yielding relaxation times, λ, as a function of frequency and polymer concentration were performed to assess self‐assembly characteristics of biopolymers in aqueous solution. Reduction of λ‐values (slope) up to a critical frequency value (CFV) helps characterize structure formation. Proteins and octenyl succinic anhydrate (OSA)‐modified depolymerized waxy rice starch (DWxRc) show a well‐defined λ‐slope at all concentrations. Except for whey protein isolate (WPI, 0.184 g/L) and 7% OSA‐modified DWxRc (1.84 g/L), the λ‐values of the solutions are comparable (P > 0.05), indicating similar structures. Self‐assembly interaction of α‐lactalbumin (3.68 g/L) with OSA‐modified polysaccharides is observed with 18.4 g/L of 7% OSA‐modified DWxRc (CFV of 0.08 Hz), while WPI (3.68 g/L) exhibits self‐assembly with all polysaccharides and concentrations. Transmission electron microscopy (TEM) of electrostatically precipitated proteins alone or in combination with OSA‐modified polysaccharides confirms that λ?slope and CFV values relate to shape, size, and shear stability of the assembled structures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43603.     

Comparison of double-walled with single-walled carbon nanotube electrodes by electrochemistry

Double-walled carbon nanotubes (DWCNTs) were selectively functionalised by treatment with concentrated nitric and sulphuric acid, resulting in carboxylated outer and pristine inner tube constituents. The functionalised DWCNTs were then incorporated into two types of pre-existing carbon nanotube (CNT) electrode platforms, and the performance of each was compared to single-walled carbon nanotubes (SWCNTs). To make the CNT electrode platforms DWCNTs were covalently bound to fluorinated tin oxide glass (FTO) or electrografted aminophenyl tether layers on silicon. The performance of single- compared to double-walled CNTs on FTO or silicon supported electrodes was then determined through electrochemical methods, using the redox probes, ferrocene and ruthenium hexaamine, respectively. The DWCNTs showed an improved heterogeneous rate constant. This improvement was attributed to the protection of the electronic properties of the inner wall of the DWCNT during the chemical modification and suggests that DWCNTs may offer a useful alternative to SWCNTs in future electronic devices.     

A PNA-DNA2 Triple-Helix Molecular Switch-Based Colorimetric Sensor for Sensitive and Specific Detection of microRNAs from Cancer Cells

Peptide nucleic acids (PNAs), the synthetic DNA mimics that can bind to oligonucleotides to form duplexes, triplexes, and quadruplexes, could be advantageous as probes for nucleic acid sequences owing to their unique physicochemical and biochemical properties. We have found that a homopurine PNA strand could bind to two homopyrimidine DNA strands to form a PNA-DNA₂ triplex. Moreover, the cyanine dye DiSC₂(5) could bind with high affinity to this triplex and cause a noticeable color change. On the basis of this phenomenon, we have designed a label-free colorimetric sensing platform for miRNAs from cancer cells by using a PNA-DNA₂ triple-helix molecular switch (THMS) and DiSC₂(5). This sensing platform can detect miRNA-21 specifically with a detection limit of 0.18 nM, which is comparable to that of the THMS-mediated fluorescence sensing platform. Moreover, this colorimetric platform does not involve any chemical modification or enzymatic signal amplification, which boosts its applicability and availability at the point of care in resource-limited settings. The universality of this approach can be simply achieved by altering the sequences of the probe DNA for specific targets.     

Recognition of the DNA Minor Groove by Thiazotropsin Analogues

Solution‐phase self‐association characteristics and DNA molecular‐recognition properties are reported for three close analogues of minor‐groove‐binding ligands from the thiazotropsin class of lexitropsin molecules; they incorporate isopropyl thiazole as a lipophilic building block. Thiazotropsin B (AcImPy^iPrThDp) shows similar self‐assembly characteristics to thiazotropsin A (FoPyPy^iPrThDp), although it is engineered, by incorporation of imidazole in place of N‐methyl pyrrole, to swap its DNA recognition target from 5′‐ACTA GT‐3′ to 5′‐ACGC GT‐3′. Replacement of the formamide head group in thiazotropsin A by nicotinamide in AIK‐18/51 results in a measureable difference in solution‐phase self‐assembly character and substantially enhanced DNA association characteristics. The structures and associated thermodynamic parameters of self‐assembled ligand aggregates and their complexes with their respective DNA targets are considered in the context of cluster targeting of DNA by minor‐groove complexes.     

Spatially-interactive biomolecular networks organized by nucleic Acid nanostructures

Living systems have evolved a variety of nanostructures to control the molecular interactions that mediate many functions including the recognition of targets by receptors, the binding of enzymes to substrates, and the regulation of enzymatic activity. Mimicking these structures outside of the cell requires methods that offer nanoscale control over the organization of individual network components. Advances in DNA nanotechnology have enabled the design and fabrication of sophisticated one-, two- and three-dimensional (1D, 2D, and 3D) nanostructures that utilize spontaneous and sequence-specific DNA hybridization. Compared with other self-assembling biopolymers, DNA nanostructures offer predictable and programmable interactions and surface features to which other nanoparticles and biomolecules can be precisely positioned. The ability to control the spatial arrangement of the components while constructing highly organized networks will lead to various applications of these systems. For example, DNA nanoarrays with surface displays of molecular probes can sense noncovalent hybridization interactions with DNA, RNA, and proteins and covalent chemical reactions. DNA nanostructures can also align external molecules into well-defined arrays, which may improve the resolution of many structural determination methods, such as X-ray diffraction, cryo-EM, NMR, and super-resolution fluorescence. Moreover, by constraint of target entities to specific conformations, self-assembled DNA nanostructures can serve as molecular rulers to evaluate conformation-dependent activities. This Account describes the most recent advances in the DNA nanostructure directed assembly of biomolecular networks and explores the possibility of applying this technology to other fields of study. Recently, several reports have demonstrated the DNA nanostructure directed assembly of spatially interactive biomolecular networks. For example, researchers have constructed synthetic multienzyme cascades by organizing the position of the components using DNA nanoscaffolds in vitro or by utilizing RNA matrices in vivo. These structures display enhanced efficiency compared with the corresponding unstructured enzyme mixtures. Such systems are designed to mimic cellular function, where substrate diffusion between enzymes is facilitated and reactions are catalyzed with high efficiency and specificity. In addition, researchers have assembled multiple choromophores into arrays using a DNA nanoscaffold that optimizes the relative distance between the dyes and their spatial organization. The resulting artificial light-harvesting system exhibits efficient cascading energy transfers. Finally, DNA nanostructures have been used as assembly templates to construct nanodevices that execute rationally designed behaviors, including cargo loading, transportation, and route control.     

Dynamic pressure‐driven covalent assembly of inner skin hollow fiber multilayer membrane

A covalent assembly was accomplished onto hollow fibers via a dynamic pressure‐driven layer‐by‐layer (LbL) technique. The covalent crosslinking multilayers were successfully formed onto the inner surfaces of hollow fiber porous substrates during the alternatively filtration of polyethyleneimine (PEI) and glutaraldehyde (GA) solutions. The formation of covalent bond between PEI and GA was confirmed using fourier transform infrared (FTIR) spectra. The thickness increment on a quartz slide clearly suggested the stepwise growth of multilayer at nanometer scale. The regular alternation of zeta potentials demonstrated that the successful formation of GA‐crosslinked PEI multilayers on the hollow fibers. The multilayer membranes showed excellent pervaporation performances for the dehydration of different solvent–water mixtures. The selectivity and permeability can be controlled by varying the PEI layer number. More importantly, the covalent assembled multilayer membrane rendered much higher stabilities compared with those from electrostatically LbL assembly, which offers much opportunity for practical applications. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Comparative Study of Interfacial and Biological Properties in <Emphasis Type="SmallCaps">d</Emphasis>-Glycerate-Derived Surfactants

The effects of hydrophobic chain length on the interfacial and biological properties of diacyl d ‐glyceric acid (d ‐GA) sodium salts were evaluated based on interfacial tension analyses, dynamic light scattering (DLS), and antitrypsin activity. Of the four synthesized d ‐GA‐derived surfactants [dihexanoyl d ‐GA sodium salt (diC6GA‐Na), dioctanoyl d ‐GA sodium salt (diC8GA‐Na), didecanoyl d ‐GA sodium salt (diC10GA‐Na), and dilauroyl d ‐GA sodium salt (diC12GA‐Na)], only those with C6, C8, and C10 acyl chains were investigated because diC12GA‐Na were insoluble at room temperature. Together with our previous results, surface tensions at the critical micelle concentration (CMC) were 33.9 mN/m for diC6GA‐Na, 25.5 mN/m for diC8GA‐Na, and 27.9 mN/m for diC10GA‐Na. Evaluation of assembly size via DLS and optical microscopy revealed that diC8GA‐Na and diC10GA‐Na formed large associates with average sizes ranging from 50 to 200 μm at concentrations 4–5 times greater than their CMC, whereas diC6GA‐Na did not form such associates. In tryptic hydrolysis studies using N^α‐benzoyl‐dl ‐arginine‐4‐nitroanilide as a substrate, diC8GA‐Na exhibited an inhibitory effect on trypsin (trypsin specific activity: 0.26 ± 0.045 U/mg‐protein) greater than that of diC10GA‐Na (0.39 ± 0.10 U/mg‐protein), whereas diC6GA‐Na did not show antitrypsin activity. These results show that diC8GA‐Na was the most bioactive of the evaluated diacyl d ‐glycerate surfactants.     

Trifunctional Saxitoxin Conjugates for Covalent Labeling of Voltage-Gated Sodium Channels**

Voltage-gated sodium ion channels (Na_Vs) are integral membrane protein complexes responsible for electrical signal conduction in excitable cells. Methods that enable selective labeling of Na_Vs hold potential value for understanding how channel regulation and post-translational modification are influenced during development and in response to diseases and disorders of the nervous system. We have developed chemical reagents patterned after (+)-saxitoxin (STX) – a potent and reversible inhibitor of multiple Na_V isoforms – and affixed with a reactive electrophile and either a biotin cofactor, fluorophore, or ‘click’ functional group for labeling wild-type channels. Our studies reveal enigmatic structural effects of the probes on the potency and efficiency of covalent protein modification. Among the compounds analyzed, a STX-maleimide-coumarin derivative is most effective at irreversibly blocking Na⁺ conductance when applied to recombinant Na_Vs and endogenous channels expressed in hippocampal neurons. Mechanistic analysis supports the conclusion that high-affinity toxin binding is a prerequisite for covalent protein modification. Results from these studies are guiding the development of next-generation tool compounds for selective modification of Na_Vs expressed in the plasma membranes of cells.     

Metal‐organic gels of simple chemicals and their high efficacy in removing arsenic(V) in water

Metal‐organic gels (MOGs) have emerged as a class of functional materials that show great potential applications in the field of catalysis, energy storage, template synthesis, and environmental technology. The construction of functional MOGs and the control of functionality are still challenging due to complicated chemicals or routes involved in previous works. Here we report a series of tunable multifunctional MOGs by directly gelating between Fe³⁺ and simple chemicals, propanedioic acid (H₂PA), succinic acid (H₂SA), glutaric acid (H₂GA), and fumaric acid (H₂FA) in ethanol. The obtained MOGs exhibit self‐healing property and good conductivity, and were used for high efficacy removal of arsenic (As) in water. The ease, low cost, and scalability of the assembly process combined with multifunctionality make these MOGs be potentially applied in the fields of energy storage and sewage disposal. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3719–3727, 2018     

Glutaraldehyde‐crosslinking for improved copper absorption selectivity and chemical stability of polyethyleneimine coatings

Nano‐thin coatings of glutaraldehyde (GA)‐crosslinked polyethyleneimine (PEI) are extremely selective and effective in binding copper from seawater. Here it was demonstrated that GA‐PEI performs significantly different from PEI. The copper‐selectivity of self‐assembled PEI coatings on silicon substrates was greatly improved by GA‐crosslinking. After submersion in artificial seawater containing 200 ppb copper and equimolar amounts of 11 competing ions only copper and trace amounts of Zn were detected in the GA‐crosslinked coatings, while for non‐crosslinked PEI there was about 30% Zn present relative to copper. The coatings were demonstrated to be highly stable under acidic conditions and retained their copper‐binding selectivity after repeated cycles of binding and acid‐mediated elution. After self‐assembly of the GA‐crosslinked coating on mesoporous diatomaceous earth particles, significant amounts of copper could be extracted from 200 ppb in artificial seawater and eluted under acidic pH. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43954.     

Olaparib-Based Photoaffinity Probes for PARP-1 Detection in Living Cells

The poly-ADP-ribose polymerase (PARP) is a protein from the family of ADP-ribosyltransferases that catalyzes polyadenosine diphosphate ribose (ADPR) formation in order to attract the DNA repair machinery to sites of DNA damage. The inhibition of PARP activity by olaparib can cause cell death, which is of clinical relevance in some tumor types. This demonstrates that quantification of PARP activity in the context of living cells is of great importance. In this work, we present the design, synthesis and biological evaluation of photo-activatable affinity probes inspired by the olaparib molecule that are equipped with a diazirine for covalent attachment upon activation by UV light and a ligation handle for the addition of a reporter group of choice. SDS-PAGE, western blotting and label-free LC-MS/MS quantification analysis show that the probes target the PARP-1 protein and are selectively outcompeted by olaparib; this suggests that they bind in the same enzymatic pocket. Proteomics data are available via ProteomeXchange with identifier PXD018661.     

Wide Area Reversible Adhesive for In‐Space Assembly

The design of future space structures may anticipate a greater need for in‐space assembly due to larger planned space structures and changes in mission profiles over their operational lifetimes. A rapid and reversible adhesive coating over the structure’s surface would allow additional components to be bonded at any arbitrary time in the future. A scalable wide‐area reversible adhesive utilizing a high glass transition thermoset polymer possessing thermally exchangeable bonds can serve as an enabling technology for in‐space assembly. Coatings of aromatic thermosetting copolyesters can be deposited on aluminum and titanium coupons, which bond when heated to 400 °C with the counterpart surfaces under pressure. Reversibility over multiple cycles is shown within a dynamic mechanical analyzer with the limiting constraint being the necessity of nondelaminatory (cohesive) debonding of the bonded coupons. Bonded coupons can sustain a thermal cycle spanning the representative temperatures in low earth orbit under tension with no failure. A localized rapid heating method amenable for in‐space assembly can be used to bond titanium coupons using induction heating with a bonding time of 40 s.     

Inkjet Printing Based Layer‐by‐Layer Assembly Capable of Composite Patterning of Multilayered Nanofilms

Surface modification involves developing a versatile thin film by combining the physical, chemical, or biological characteristics of the functional materials and can facilitate controlling material for desirable aims. Layer‐by‐layer (LbL) assembly can be used to create materials with controlled thicknesses and morphologies, diverse functionalities, and unique structures on any surface. However, despite the advantages of the LbL fabrication technique, there are limits to its application because it is a time‐consuming process and has difficulty controlling the shape of nanofilms. In addition, controlling the lateral organization is difficult because the preparation methods are based on one‐pot self‐assembly. In this study, a multilayered fabrication system is developed for the high‐throughput LbL assembly of nanofilms through inkjet printing. With various types of materials from synthetic polymer to graphene oxide to natural polymer and protein, the approach can tune the preparation of nanoscale multilayers with desired structures and shapes for specific applications on various substrates, including a silicon wafer, quartz glass, and cellulose‐based paper.     

Improving the mechanical properties of graphene oxide based materials by covalent attachment of polymer chains

We report on the modification of graphene oxide (GO) with poly(vinyl alcohol) (PVA) leading to the mechanical improvement of GO based materials. First, GO was covalently functionalised with PVA by esterification of carboxylic groups on GO with hydroxyl groups of PVA resulting in functionalised f-(PVA)GO. This was carried out for PVA of six different molecular weights. This functionalised graphene oxide could be formed into a paper-like material by vacuum filtration. Papers prepared from f-(PVA)GO showed significant increases in mechanical properties compared to those prepared with GO or with simple mixtures of GO and PVA. The best performance was achieved for PVA functional groups with molecular weights between 50 and 150 kg/mol. Improvements in Young’s moduli of 60% and tensile strength of 400% were observed relative to GO-only paper. The improved mechanical properties are attributed to enhanced inter-flake stress transfer due to the covalently bonded PVA. Second, functionalised f-(PVA)GO was used as filler in PVA-based composites. The application of a pre-selection method allowed the use of only the largest functionalised f-(PVA)GO flakes. This resulted in substantially reinforced PVA–f-(PVA)GO composites. Both modulus and strength increased by 40% relative to the pure polymer for f-(PVA)GO loadings below 0.3 vol.%.