Macromolecular Nanostructures Research Articles

Bottom-Up Synthesized Glucan Materials: Opportunities from Applied Biocatalysis.

Linear d-glucans are natural polysaccharides of simple chemical structure. They are comprised of d-glucosyl units linked by a single type of glycosidic bond. Noncovalent interactions within, and between, the d-glucan chains give rise to a broad variety of macromolecular nanostructures that can assemble into crystalline-organized materials of tunable morphology. Structure design and functionalization of d-glucans for diverse material applications largely relies on top-down processing and chemical derivatization of naturally derived starting materials. The top-down approach encounters critical limitations in efficiency, selectivity, and flexibility. Bottom-up approaches of d-glucan synthesis offer different, and often more precise, ways of polymer structure control and provide means of functional diversification widely inaccessible to top-down routes of polysaccharide material processing. Here the natural and engineered enzymes (glycosyltransferases, glycoside hydrolases and phosphorylases, glycosynthases) for d-glucan polymerization are described and the use of applied biocatalysis for the bottom-up assembly of specific d-glucan structures is shown. Advanced material applications of the resulting polymeric products are further shown and their important role in the development of sustainable macromolecular materials in a bio-based circular economy is discussed.

Ultra-High-Molecular-Weight Macrocyclic Bottlebrushes via Post-Polymerization Modification of a Cyclic Polymer

Polymer bottlebrushes are complex macromolecular nanostructures with polymeric side chains densely grafted to a polymer backbone. In this work, a synthetic strategy for the synthesis of cyclic bott...

Generation of spatially ordered metal–polymer nanostructures in the irradiated dispersions of poly(acrylic acid)–poly(vinylimidazole)–Cu2+ complexes

The generation of metal nanostructures by radiation-induced reduction of copper ions in aqueous dispersions of macromolecular complexes of poly(acrylic acid) and polyvinylimidazolе has been studied in the pH range of 2.3–4.3. It was shown that an effective coordination number of Cu2+ in the complex with polymer units decreased at lower pH, which resulted in dramatic increase of the nanoparticle formation rate. As demonstrated by transmission electron microscopy, using the poly(acrylic acid)–polyvinylimidazolе–Cu2+ complexes as precursors allows one to control the nanoparticle size and promotes assembling of spatially ordered supramolecular structures. As revealed by dynamic light scattering, decreasing the medium pH leads to ripening of the poly(acrylic acid)–polyvinylimidazolе–Cu2+ particles. The obtained results provide an evidence for strong effect of the pH value on the spatial organization of nanoparticles in irradiated suspensions. In the case of less acidic medium (at pH 3), assembling of nanoparticles occurs in flabby interpolymer particles, whereas at lower pH the metal nanoparticles are produced in the templates of the perfect macromolecular nanostructures.

Multivalency in a Dendritic Host–Guest System

Multivalency is an important instrument in the supramolecular chemistry toolkit for the creation of strong specific interactions. In this paper we investigate the multivalency effect in a dendritic host–guest system using molecular dynamics simulations. Specifically, we consider urea–adamantyl decorated poly(propyleneimine) dendrimers that together with compatible mono-, bi-, and tetravalent ureidoacetic acid guests can form dynamic patchy nanoparticles. First, we simulate the self-assembly of these particles into macromolecular nanostructures, showing guest-controlled reduction of dendrimer aggregation. Subsequently, we systematically study guest concentration dependent multivalent binding. At low guest concentrations multivalency of the guests clearly increases relative binding as tethered headgroups bind more often than free guests’ headgroups. We find that despite an abundance of binding sites, most of the tethered headgroups bind in close proximity, irrespective of the spacer length; nevertheless, longer spacers do increase binding. At high guest concentrations the dendrimer becomes saturated with bound headgroups, independent of guest valency. However, in direct competition the tetravalent guests prevail over the monovalent ones. This demonstrates the benefit of multivalency at high as well as low concentrations.

Stimulus-Responsive Plasmonic Chiral Signals of Gold Nanorods Organized on DNA Origami.

In response to environmental variations, living cells need to arrange the conformational changes of macromolecules to achieve the specific biofunctions. Inspired by natural molecular machines, artificial macromolecular assemblies with controllable nanostructures and environmentally responsive functions can be designed. By assembling macromolecular nanostructures with noble metal nanoparticles, environmental information could be significantly amplified and modulated. However, manufacturing dynamic plasmonic nanostructures that are efficiently responsive to different stimuli is still a challenging task. Here we demonstrate a stimulus-responsive plasmonic nanosystem based on DNA origami-organized gold nanorods (GNRs). L-shaped GNR dimers were assembled on rhombus-shaped DNA origami templates. The geometry and chiral signals of the GNR nanoarchitectures respond to multiple stimuli, including glutathione reduction, restriction enzyme action, pH change, or photoirradiation. While the glutathione reduction or restriction enzyme caused irreversible changes in the plasmonic circular dichroism (CD) signals, both pH and light irradiation triggered reversible changes in the plasmonic CD. Our system transduces external stimuli into conformational changes and circular dichroism responses in near-infrared (NIR) wavelengths. By this approach, programmable optical reporters for essential biological signals can be fabricated.

Performance dependence of swelling-filling treated Nafion membrane on nano-structure of macromolecular filler

A novel method of Nafion membrane modification by inserting proton conductive macromolecular nanostructures was previously developed. This process was referred as swelling-filling (SF) strategy for enhancing the Nafion membrane performance for direct methanol fuel cell (DMFC) application. However, the SF treated Nafion membrane got an issue of methanol permeation because of micro-pores developed in the modified membrane. In this effort, nano-structure of the SF filler was tuned via molecular structure design to adjust the micro-porous structure of the SF treated Nafion membrane. Methanol-permeation resistivity and proton conductivity of the Nafion membrane were dually boosted by the nano-shuttle SF filler. The nearly doubled selectivity leaded to a remarkable improvement on power output of DMFC and revealed pronounced application potential in DMFC.

General method for the quantification of drug loading and release kinetics of nanocarriers

Macromolecular nanostructures that are used as drug carriers are characterized by their loading and release kinetics. Release studies commonly employ the dialysis method, in which a cellulose membrane separates the solution of released drug from the nanocarrier solution. We demonstrate that it is necessary to take the effect of the dialysis membrane on the release kinetics into account. Using a two-step approach, consisting of a calibration experiment of drug diffusion through the dialysis membrane in the absence of nanocarriers, and an experiment in the presence of nanocarriers, we are able to determine all kinetic rates and in particular to disentangle kinetic dialysis membrane properties from kinetic nanocarrier properties. We apply our general approach to experimental dexamethasone release data from core-multishell nanocarriers and demonstrate that our method yields a consistent description of the nanocarrier release kinetics.

The features of the formation of the hybrid nanostructures of C60 fullerene and amphiphilic copolymer of N-vinylpyrrolidone with (di)methacrylates in isopropyl alcohol and its mixtures with water

The aggregation of the amphiphilic copolymer N-vinylpyrrolidone with lauryl methacrylate and triethylene glycol dimethacrylate in isopropyl alcohol and its mixtures with water was studied by the dynamic light scattering and transmission electron microscopy. It was shown that the aggregation of amphiphilic macromolecules was enhanced at increase of the media polarity. The TEM images of the terpolymer aggregates demonstrated the presence of spherical shape particles with diameter ca. 50 and 300–500 nm after evaporation of isopropyl alcohol and isopropyl alcohol-water mixture of 60:40 vol% composition, respectively. The fullerene hybrid macromolecular structures were produced owing to spontaneous aggregation of the fullerene C60 and the terpolymer colloids. According to dynamic light scattering (DLS), in isopropyl alcohol, the monodisperse C60-copolymer structure was formed in which the fullerene was held by the copolymer particles due to hydrophobic interactions. According to the electronic absorption spectroscopy, the encapsulated fullerene kept its electronic structure in isopropyl alcohol in contrast to the isopropyl alcohol-water mixtures. The fullerene absorption band at λ 330 nm shifted to the red region due to donor-acceptor interaction between the terpolymer and C60, and the absorption band appears in the 400–500-nm region as a result of the fullerene cluster formation in the isopropyl alcohol-water mixtures. Stable macromolecular hybrid nanostructures of the amorphous fullerene produced in isopropyl alcohol were spherical particles and uneven surface. In 60:40 vol% isopropyl alcohol-water mixture, the fullerene as clusters of crystalline nature with a size of ~50 nm was found.

A combination of frequency photoacoustic and photoacoustic spectroscopy techniques for measurement of optical and thermal properties of macromolecular nanostructures

Macromolecular nanostructures represent a class of materials of considerable interest for application in nanooptics and nanoelectronics. The potential applications require understanding of the transport mechanisms in macromolecular nanostructures, and the recent theoretical studies indicated that the transport mechanisms of heat generated by absorption of IR and visible light are different. In this paper is proposed a combination of experimental techniques that would enable simultaneous measurement of optical and thermal properties of macromolecular structures excited by wide spectrum of light. The results of the experiments would enable credible testing of validity of the predictions of the theoretical studies, and further insight of the transport processes in macromolecular nanostructures.

Confined Synthesis of Organometallic Chains and Macrocycles by Cu-O Surface Templating.

The bottom-up construction of low-dimensional macromolecular nanostructures directly on a surface is a promising approach for future application in molecular electronics and integrated circuit production. However, challenges still remain in controlling the formation of these nanostructures with predetermined patterns (such as linear or cyclic) or dimensions (such as the length of one-dimensional (1D) chains). Here, we demonstrate that a high degree of structural control can be achieved by employing a Cu(110)-(2×1)O nanotemplate for the confined synthesis of organometallic chains and macrocycles. This template contains ordered arrays of alternating stripes of Cu-O chains and bare Cu, the widths of which are controllable. Using scanning tunneling microscopy and low-energy electron diffraction, we show that well-defined, ordered 1D zigzag organometallic oligomeric chains with uniform lengths can be fabricated on the Cu stripes (width >5.6 nm) of the Cu(110)-(2×1)O surface. In addition, the lengths of the meta-terphenyl (MTP)-based chains can be adjusted by controlling the widths of the Cu stripes within a certain range. When reducing the widths of Cu stripes to a range of 2.6 to 5.6 nm, organometallic macrocycles including tetramer (MTP-Cu)4, hexamer (MTP-Cu)6, and octamer (MTP-Cu)8 species are formed due to the spatial confinement effect and attraction to the Cu-O chains. An overview of all formed organometallic macrocycles on the Cu stripes with different widths reveals that the origin of the formation of these macrocycles is the cis-configured organometallic dimer (MTP)2Cu3, which was observed on the extremely narrow Cu stripe with a width of 1.5 nm.

New hybrid nanostructures of C60 fullerene based on an amphiphilic copolymer of N-vinylpyrrolidone and (di)methacrylates

New hybrid macromolecular nanostructures of C60 fullerene based on an amphiphilic copolymer of N-vinylpyrrolidone with lauryl methacrylate and triethylene glycol dimethacrylate were prepared in isopropyl alcohol.

Effect of hybrid nanoparticles on glass transition temperature of polymer nanocomposites

Changes in the glass transition temperatures of composites based on polystyrene and nanosized macromolecular nanostructures (molecular silicasols, dendrimers) are reported. Silicasols are nanosized particles consisting of a silica core and an ethyl phenyl shell; dendrimers are formed using a carbosilane core with ethyl phenyl end groups. It has been observed that the glass transition temperatures of the composites (Tgc) may be either above or below the glass transition temperature of polystyrene, depending on the size of the filler particles. A theoretical model based on the relation between the glass transition temperature and the configurational entropy of the composite, which satisfactorily describes the experimental dependence, was developed. It is found that the effect of the size of the hybrid nanoparticles on Tgc was determined using two factors. First, the presence of an organic layer on the surface of nanoparticles increases the number of degrees of freedom and the entropy of the system, thereby reducing Tgc. Second, the particles present in the polymer reduce the number of configuration states of macromolecules, which reduces the disorientation entropy. This effect leads to an increase Tgc. The competition between these two main factors determines the sign of the glass transition temperature deviation. The size of the particles and their organic surface layer play the key roles in the thermodynamic properties of the composites. POLYM. COMPOS., 37:1978–1990, 2016. © 2015 Society of Plastics Engineers

The Development of Gold Nanoparticles as an Ideal Non-Viral Nanoscale Delivery System for Islet Transplantation.

Islet transplantation is a promising therapy for T1DM, but shows variable success. A long-standing goal is to develop an efficient system for the delivery of molecular cargos to islets in order to improve islet transplant outcomes. Common viral and non-viral systems can only deliver molecular cargos to the periphery cells of an islet. Most of these systems alternate islet function, pose potential oncogenic risks, and increase immunogenicity. Gold nanoparticles are macromolecular nanostructures with high biocompatibility containing void spaces in their interior regions and modifiable surface groups that allow conjugation of therapeutic drugs and proteins. Gold nanoparticles of 12 nm in size have demonstrated a high efficacy to enter cells without auxiliary agents and minimal cytotoxicity. We hypothesize that gold nanoparticles could be used as a unique vehicle to deliver functional molecular cargos for islets. Previous studies performed in the lab indicated the ability to use Cy5 labeled gold nanoparticles conjugated with a specific oligonucleotide sequence. A new spherical nanoparticle tagged with Cy5 was tested for penetration efficacy. Gold nanoparticles were conjugated with mRNA and tagged with green fluorescent protein (GFP) in order to further determine the stability and time required for the mRNA to be delivered and expressed. Gold nanoparticle transfection efficacy was tested in human islets using confocal microscopy and optimal concentration was determined. Islet function was evaluated by measuring the calcium influx and insulin secretion in response to glucose. (i) Confocal images showed high uptake of gold nanoparticles including islet cores. (ii) 12 nM of gold nanoparticles conjugated with Cy5, Cy5/Oligonucleotide and GFP/mRNA were tested for 24 hours, 48 hours and 72 hours of incubation in order to determine the optimal condition. (iii) The functionality of gold nanoparticle-treated islets was well preserved after 72 hours. There was no significant difference in the intracellular calcium concentration of the control group versus the islets treated with gold nanoparticles (p>0.05). Mitochondrial potential indices demonstrated similarity between the control group and islets treated with gold nanoparticles (p>0.05). With the ability to use gold nanoparticles as a delivery system to islets with high transfection efficacy will allow the possibility to conjugate a specific protein or siRNA.

Cross-Linked Poly(Vinyl Pyrrolidone) Hard-Template and Polymerization Method in Controlling Nanostructures and Properties of Polyaniline Composites

The present work investigates the use of hard template cross-linked poly(vinyl pyrrolidone) (CPVP) in polyaniline (PANI) material design. In chemical polymerization with slight modification in synthesis conditions, CPVP regulates the formation of three PANI composites PANI-CPVP 1 (nanorods) PANI-CPVP 2 (nano-rice-like structures) and PANI-CPVP 3 (crystalline grains). FTIR, XRD and SEM techniques explain the different chemical and structural modifications in the composites compared to PANI. In thermogravimetry, PANI has three-step weight-loss while PANI-CPVP composites exhibit 4/5 step weight-loss. All the composites exhibit characteristic differences in conductivity and hardness properties. An interrelationship thus exists between macromolecular nanostructures and properties.

Clean Coupling of Unfunctionalized Porphyrins at Surfaces To Give Highly Oriented Organometallic Oligomers

The direct coupling of complex, functional organic molecules at a surface is one of the outstanding challenges in the road map to future molecular devices. Equally demanding is to meet this challenge without recourse to additional functionalization of the molecular building blocks and via clean surface reactions that leave no surface contamination. Here, we demonstrate the directional coupling of unfunctionalized porphyrin molecules--large aromatic multifunctional building blocks--on a single crystal copper surface, which generates highly oriented one-dimensional organometallic macromolecular nanostructures (wires) in a reaction which generates gaseous hydrogen as the only byproduct. In situ scanning tunneling microscopy and temperature programmed desorption, supported by theoretical modeling, reveal that the process is driven by C-H bond scission and the incorporation of copper atoms in between the organic components to form a very stable organocopper oligomer comprising organometallic edge-to-edge porphyrin-Cu-porphyrin connections on the surface that are unprecedented in solution chemistry. The hydrogen generated during the reaction leaves the surface and, therefore, produces no surface contamination. A remarkable feature of the wires is their stability at high temperatures (up to 670 K) and their preference for 1D growth along a prescribed crystallographic direction of the surface. The on-surface formation of directional organometallic wires that link highly functional porphyrin cores via direct C-Cu-C bonds in a single-step synthesis is a new development in surface-based molecular systems and provides a versatile approach to create functional organic nanostructures at surfaces.

An in vitro release study of indomethacin from nanoparticles based on methyl methacrylate/glycidyl methacrylate copolymers

Indomethacin was coupled onto some macromolecular nanostructures based on methyl methacrylate copolymers with glycidyl methacrylate and tested as a model drug. The polymeric matrices were synthesized by radical emulsion copolymerization with and without the presence of a continuous external magnetic field of 1500Gs intensity. Mathematical analysis of the release data was performed using Higuchi, Peppas-Korsmeyer equations. NIR chemical imaging (NIR-CI) was used to provide information about the spatial distribution of the components in the studied nanostructures. This opportunity was used to visualize the spatial distribution of bioactive substances (indomethacin) into the polymeric matrix, as well as to evaluate the degree of chemical and/or physical heterogeneity of the bioactive samples. The release rate dependence on the synthesis conditions as well as on the chemical compositions of the tested polymeric systems, it was also evidenced.

Nanodroplets of polyisoprene fluid contained within poly(acrylic acid‐co‐acrylamide) shells

AbstractThe preparation and characterization of macromolecular nanostructures possessing an amphiphilic core–shell morphology with a hydrophobic, fluidlike core domain with a low glass‐transition temperature are described. The nanostructures were prepared by the self‐assembly of polyisoprene‐b‐poly(acrylic acid) diblock copolymers into polymer micelles, followed by crosslinking of the hydrophilic shell layer via condensation between the acrylic acid functionalities and 2,2′‐(ethylenedioxy)bis(ethylamine), in the presence of 1‐(3′‐dimethylaminopropyl)‐3‐ethylcarbodiimide methiodide. The properties of the resulting shell‐crosslinked knedel‐like (SCK) nanoparticles were dependent on the microstructure and properties of the polyisoprene core domain. SCKs containing polyisoprene with a mixture of 3,4‐ and 1,2‐microstructures underwent little shape distortion upon adsorption from aqueous solutions onto mica or graphite. In contrast, when SCKs were composed of polyisoprene of predominantly cis‐1,4‐repeat units, the glass‐transition temperature was −65 °C, and the nanospheres deformed to a large extent upon adsorption onto a hydrophilic substrate (mica). Adsorption onto graphite gave a less pronounced deformation, as determined by a combination of transmission electron microscopy and atomic force microscopy. Subsequent crosslinking of the core domain (in addition to the initial shell crosslinking) dramatically reduced the fluid nature and, therefore, reduced the SCK shape change. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1659–1668, 2003