Three-dimensional Macromolecules Research Articles

Two-Photon Absorbing Dendrimers and Their Properties-An Overview.

This review describes the two-photon absorption properties of dendrimers, which are arborescent three-dimensional macromolecules differing from polymers by their perfectly defined structure. The two-photon absorption process is a third order non-linear optical property that is attractive because it can be used in a wide range of applications. In this review, dendrimers that were studied for their two-photon absorption properties are first described. Then, the use of dendritic TPA chromophores for light harvesting, photopolymerization, optical power limitation, cell imaging, singlet oxygen generation, and photodynamic therapy is described. This review thus proposes an overview of the properties and possible applications of two-photon absorbing dendrimers.

Research progress on synthesis and applications of hyperbranched polymers

Hyperbranched polymers (HBPs) are a kind of highly branched three-dimensional macromolecule. Over the past decade, they have received much attention from interdisciplinary research. They have many branched points and their molecular chain is not easy to tangle. Additionally, as the molecular weight of the substance increases, its viscosity does not vary. Rich end functional groups are simple to alter and conducive to the synthesis of a variety of functional materials. Their simple synthesis and special properties have attracted a lot of attention from researchers in polymer science. Therefore, this review intends to introduce some methods to synthesize HBPs, including living polymerization, polycondensation, ring-opening polymerization and some other methods. Then, the properties of from the aspects of thermal, mechanical, rheological and solution properties are introduced. At last, the applications in materials and medicine of HBPs are reviewed in this paper followed by a discussion of the development prospects and potential challenges. HBPs have drawn great attention from researchers due to their special properties and unique application prospects. As the research on 3-dimensional HBPs is becoming more and more mature, 2-dimensional HBPs which are less focused on may be one of the focuses of future research.

Synthesis of AB2 type hyperbranched polymer by CuAAC based 1,3-dipolar cycloaddition and its application in delivering curcumin to cancer cell cultures in-vitro

Hyperbranched polymers are three-dimensional macromolecules with unique physical and chemical properties, such as high solubility, low viscosity, and many functional groups at the terminals, as well as possible applications in several fields. Herein, we report the synthesis of a trifunctional AB2 monomer in a three-step process followed by "Click" polymerization via copper-catalyzed azide-alkyne cycloaddition to prepare a polytriazole-based hyperbranched polymer. Synthesized monomer and polymer were subsequently characterized by 1H and 13C NMR spectroscopy, and size-exclusion chromatography. The AB2 type hyperbranched polymer was self-assembled into lipid-polymer hybrid nanoparticles (HBP-NPs) through a nanoprecipitation approach, and curcumin (CUR) was incorporated into the HBP-NPs. The CUR-loaded HBP-NPs were characterized by particle size analysis, zeta potential, polydispersity index, morphology, drug entrapment efficiency, in vitro drug release, cellular uptake, and anticancer potential against HepG2 and NCI-H460 cell lines. The results indicated the CUR-loaded HBP-NPs demonstrated enhanced cell inhibition due to the improved delivery of CUR upon incorporation into HBP-NPs.

Synthesis and Applications of Dendrimer-Modified Mesoporous Nanoparticles

Because of their excellent physical properties, mesoporous nanoparticles have been widely studied, especially in the aspect of surface functionalization, which has had a profound impact in many fields of scientific research. Dendrimers, as a kind of three-dimensional macromolecules, also have been widely concerned and studied on account of their unique structural properties. Combining dendrimers with mesoporous nanoparticles can fabricate novel hybrid nanomaterials that possess the advantages of both dendrimers and mesoporous nanoparticles, which may meet the need of the increasing application demands in many fields. This review mainly introduces some of the extensive applications of dendrimers and mesoporous nanoparticles combined in recent years, and briefly summarizes their synthesis methods.

Dendrimer applications: a brief review

: Dendrimers are highly branched three-dimensional macromolecules with a highly controlled structure, a single molecular weight, numerous controllable dendritic branches and peripheral functionalities, as well as the tendency to adopt an ellipsoid or spheroid shape once a certain size is reached. These features have made them attractive for application in pharmaceutical and medicinal chemistry in gene transfection, as medical imaging agents, and as drug carriers in potential drug delivery agents. The incorporation of metallic species into dendritic molecules has also been reported; the focus has been on organometallic dendrimers with metallic species only at specific positions of the molecules, such as the core, dendritic branches and the periphery, studied for their magnetic, electronic, and photo-optical or catalytic properties. Dendrimers have been investigated for optoelectronic applications (adsorption, emission, laser emission, nonlinear optics) through the encapsulation of active units by dendritic branches, core and peripheral. This review briefly discusses their use in nanomedicine, cancer treatment, treatment of other diseases, tissue repair, catalysis and applications in OLEDs and solar cells.

Macromolecules Structural Classification With a 3D Dilated Dense Network in Cryo-Electron Tomography.

Cryo-electron tomography, combined with subtomogram averaging (STA), can reveal three-dimensional (3D) macromolecule structures in the near-native state from cells and other biological samples. In STA, to get a high-resolution 3D view of macromolecule structures, diverse macromolecules captured by the cellular tomograms need to be accurately classified. However, due to the poor signal-to-noise-ratio (SNR) and severe ray artifacts in the tomogram, it remains a major challenge to classify macromolecules with high accuracy. In this paper, we propose a new convolutional neural network, named 3D-Dilated-DenseNet, to improve the performance of macromolecule classification. In 3D-Dilated-DenseNet, there are two key strategies to guarantee macromolecule classification accuracy: 1) Using dense connections to enhance feature map utilization (corresponding to the baseline 3D-C-DenseNet); 2) Adopting dilated convolution to enrich multi-level information in feature maps. We tested 3D-Dilated-DenseNet and 3D-C-DenseNet both on synthetic data and experimental data. The results show that, on synthetic data, compared with the state-of-the-art method in the SHREC contest (SHREC-CNN), both 3D-C-DenseNet and 3D-Dilated-DenseNet outperform SHREC-CNN. In particular, 3D-Dilated-DenseNet improves 0.393 of F1 metric on tiny-size macromolecules and 0.213 on small-size macromolecules. On experimental data, compared with 3D-C-DenseNet, 3D-Dilated-DenseNet can increase classification performance by 2.1 percent.

Advances in dendrimer-mediated targeted drug delivery to the brain

Treating diseases of the central nervous system (CNS) still remains a problem for the researchers. Existence of specific anatomical barriers, especially the blood brain barrier (BBB), restricts the brain mobility and hinders the effectiveness of different drug therapies. Rapid nanotechnological developments have given promising solutions to this challenge. Therefore, during the last few decades, a variety of nanocarriers have been designed to deliver drugs to the brain. Dendrimers are highly branched, three-dimensional macromolecules with tailor-made surface functionality and internal cavities that make them interesting carrier to deliver the drug to the brain. Significant advances have been made in dendrimer-mediated targeted delivery to the brain in last two decades. This review article deals majorly with recent advances in dendrimer-mediated delivery to the brain with discussions on the mechanisms of biodistribution and toxicity of dendrimer crossing the BBB. This will assist researchers in designing the new strategies to deal with major challenges related to the targeted delivery of CNS therapeutic agents to the brain.

A beginner’s guide to neutron macromolecular crystallography

Hydrogen atoms drive biological structure and function, but the lightest element is often unseen in three-dimensional macromolecule structures, hampering our understanding of biochemical processes. This guide will i) present how neutron crystallography uniquely reveals the experimental positions of hydrogen atoms and resolves mechanical controversies, ii) briefly introduce beamlines at neutron facilities, iii) discuss sample requirements and preparation and iv) familiarize the reader with neutron data and refinement statistics.

The Effectiveness of Using Three-Dimensional Visualization Tools to Improve Students’ Understanding of Medicinal Chemistry and Advanced Drug Design Concepts

Computer technology is an integral part of modern research. Most undergraduate pharmacy students are not aware of the use of these techniques in the drug design process. Understanding drug-target interactions plays a vital role in the drug design process, however, teaching the molecular basis of drug action is one of the major challenges we face in medicinal chemistry courses. The increase in the availability of three-dimensional macromolecule crystal structures and computer visualization software have provided better tools to study the drugs effect at the molecular level. This study evaluates the effectiveness of using three-dimensional macromolecule visualization tools in medicinal chemistry lectures on the students understanding of the molecular basis of drug action and drug design concepts. The different examples presented in this work are part of the teaching material that were developed to suite the learning objectives of the course. In addition, the “macromolecular drug targets assignment” was introduced to the course in order to allow the students to have practical experience using the new in silico techniques. Two hundred seventy students were surveyed over the past five years, the result showed that the new teaching tools have increased students’ interest in medicinal chemistry and allowed them to develop better understanding of the effect of structural modification on compounds’ activity and structure activity relationship. In addition, it gave them an insight into the advanced methods used in drug design. https://doi.org/10.26803/ijlter.19.4.11

Facile Fabrication of Environmentally-Friendly Hydroxyl-Functionalized Multiwalled Carbon Nanotubes/Soy Oil-Based Polyurethane Nanocomposite Bioplastics with Enhanced Mechanical, Thermal, and Electrical Conductivity Properties.

It is challenging to prepare polyurethane bioplastics from renewable resources in a sustainable world. In this work, polyurethane nanocomposite bioplastics are fabricated by blending up to 80 wt % of soy-based polyol and petrochemical polyol with hydroxyl-functionalized multiwalled carbon nanotubes (MWCNTs-OH). The scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FTIR) analyses reveal homogeneous dispersion of the MWCNTs-OH in the matrix, as well as interaction or reaction of MWCNTs-OH with the matrix or polymeric methylene diphenyl diisocyanate (pMDI) in forming the organic–inorganic hybrid bioplastic with a three-dimensional (3D) macromolecule network structure. Mechanical properties and electrical conductivity are remarkably enhanced with the increase of the multiwalled carbon nanotube (MWCNTs) loading. Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) results show that the bioplastics with MWCNTs-OH have a better thermal stability compared with the bioplastics without MWCNTs-OH. The composition of the nanocomposites, which defines the characteristics of the material and its thermal and electrical conductivity properties, can be precisely controlled by simply varying the concentration of MWCNTs-OH in the polyol mixture solution.

Elegant pH-Responsive Nanovehicle for Drug Delivery Based on Triazine Dendrimer Modified Magnetic Nanoparticles.

Owing to properties of magnetic nanoparticles and elegant three-dimensional macromolecule architectural features, dendrimeric structures have been investigated as nanoscale drug delivery systems. In this work, a novel magnetic nanocarrier, generation two (G2) triazine dendrimer modified Fe3O4@SiO2 magnetic nanoparticles (MNP-G2), was designed, fabricated, and characterized by Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA), vibrating sample magnetometer (VSM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The prepared MNP-G2 nanosystem offers a new formulation that combines the unique properties of MNPs and triazine dendrimer as a biocompatible material for biomedical applications. To demonstrate the potential of MNP-G2, the nanoparticles were loaded with methotrexate (MTX), a proven chemotherapy drug. The MTX-loaded MNP-G2 (MNP-G2/MTX) exhibited a high drug-loading capacity of MTX and the excellent ability for controlled drug release. The cytotoxicity of MNP-G2/MTX using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide based assay and MCF-7, HeLa, and Caov-4 cell lines revealed that MNP-G2/MTX was more active against the tumor cells than the free drug in a mildly acidic environment. The results of hemolysis, hemagglutination, and coagulation assays confirmed the good blood safety of MNP-G2/MTX. Moreover, the cell uptake and intracellular distribution of MNP-G2/MTX were studied by flow cytometry analysis and confocal laser scanning microscopy (CLSM). This research suggests that MNP-G2/MTX with good biocompatibility and degradability can be selected as an ideal and effective drug carrier in targeted biomedicine studies especially anticancer applications.

Dendrimer‐based nanocarriers: a versatile platform for drug delivery

Advances in nanotechnology have had profound impacts on therapeutic delivery, leading to the development of nanomaterials engineered with large carrying capabilities and targeting functionalities. Among the nanomaterials, dendrimers have garnered particular attention from researchers owing to their well-defined structure, near-monodispersity, and ease of multifunctionalization. As hyperbranched, three-dimensional macromolecules, dendrimers can be engineered to target and deliver a wide range of therapeutic agents, including small molecules, peptides, and genes, reducing their systemic toxicities and enhancing efficacies. In this review, we provide a comprehensive overview of the commonly employed dendrimer-based nanocarrier designs, including dendrimer conjugates, Janus dendrimers, and linear-dendritic block copolymers. The discussion will progress through the basic synthetic strategies of dendrimer-based nanocarriers, followed by the potential clinical applications related to their unique structural properties. Finally, the major challenges that these nanocarriers are currently facing in their clinical translation and possible solutions to address these issues will be discussed, with the aim to provide researchers in the drug delivery field a good understanding of the potential utilities of dendrimer-based nanocarriers. WIREs Nanomed Nanobiotechnol 2017, 9:e1409. doi: 10.1002/wnan.1409 For further resources related to this article, please visit the WIREs website.

ChemInform Abstract: Hyperbranched Polymers: Advances from Synthesis to Applications

AbstractReview: 347 refs.

Synthesis of β-cyclodextrin-Based Star Block Copolymers with Thermo-Responsive Behavior

Star polymers are one example of three-dimensional macromolecules containing several arms with similar molecular weight connected to a central core. Due to their compact structure and their enhanced segment density in comparison to linear polymers of the same molecular weight, they have attracted significant attention during recent years. The preparation of block-arm star copolymers with a permanently hydrophilic block and an “environmentally” sensitive block, which can change its nature from hydrophilic to hydrophobic, leads to nanometer-sized responsive materials with unique properties. These polymers are able to undergo a conformational change or phase transition as a reply to an external stimulus resulting in the formation of core–shell nanoparticles, which further tend to aggregate. Star-shaped copolymers with different cores were synthesized via atom transfer radical polymerization (ATRP). The core-first method chosen as synthetic strategy allows good control over the polymer architecture. First of all the multifunctional initiators were prepared by esterification reaction of the hydroxyl groups with 2-chloropropionyl chloride. Using β-cyclodextrin as core molecules, which possess a well-defined number of functional groups up to 21, allows defining the number of arms per star polymer. In order to prepare stimuli-responsive multi-arm copolymers, containing a stimuli-responsive (poly(N-isopropylacrylamide) (PNIPAAm)) and a non-responsive block (poly(N,N-dimethylacrylamide) (PDMAAm)), consecutive ATRP was carried out. The polymers were characterized intensively using NMR spectroscopy and size exclusion chromatography (SEC), whereas the temperature-depending aggregation behavior in aqueous solution was determined via turbidimetry and differential scanning calorimetry (DSC).

A modular approach toward functionalized three-dimensional macromolecules: from synthetic concepts to practical applications.

A new strategy for the preparation of functional, multiarm star polymers via nitroxide-mediated "living" radical polymerization has been explored. The generality of this approach to the synthesis of three-dimensional macromolecular architectures allows for the construction of nanoscopically defined materials from a wide range of different homo, block, and random copolymers combining both apolar and polar vinylic repeat units. Functional groups can also be included along the backbone or as peripheral/chain end groups, thereby modulating the reactivity and polarity of defined portions of the stars. This modular approach to the synthesis of three-dimensional macromolecules permits the application of these tailored materials as multifunctional hosts for hydrogen bonding, nanoparticle formation, and as scaffolds for catalytic groups. Examples of applications of the functional stars in catalysis include their use in a Heck-type coupling as well as an enantioselective addition reaction.

Application of complex macromolecular architectures for advanced microelectronic materials.

The distinctive features of well-defined, three-dimensional macromolecules with topologies designed to enhance solubility and amplify end-group functionality facilitated nanophase morphologies in mixtures with organosilicates and ultimately nanoporous organosilicate networks. Novel macromolecular architectures including dendritic and star-shaped polymers and organic nanoparticles were prepared by a modular approach from several libraries of building blocks including various generations of dendritic initiators and dendrons, selectively placed to amplify functionality and/or arm number, coupled with living polymerization techniques. Mixtures of an organosilicate and the macromolecular template were deposited, cured, and the phase separation of the organic component, organized the vitrifying organosilicate into nanostructures. Removal of the sacrificial macromolecular template, also denoted as porogen, by thermolysis, yielded the desired nanoporous organosilicate, and the size scale of phase separation was strongly dependent on the chain topology. These materials were designed for use as interlayer, ultra-low dielectric insulators for on-chip applications with dielectric constant values as low as 1.5. The porogen design, chemistry and role of polymer architecture on hybrid and pore morphology will be emphasized.

Interaction between Monomeric Units of Donor−Acceptor-Functionalized Azobenzene Dendrimers: Effects on Macroscopic Configuration and First Hyperpolarizability

To find out why azobenzene dendrimers, which are branched three-dimensional macromolecules with a branch point at each of the donor−acceptor-functionalized azobenzene monomeric units, have large first hyperpolarizabilities, we used theoretical calculations for three types of dimers: (1) two azobenzenes linked covalently head-to-tail; (2) linear dimers where the two azobenzenes are nearly superimposable on the covalently bonded dimers but are not covalently linked; (3) parallel dimers where the two azobenzenes are roughly side by side. We found from ab initio calculations that the optimized geometry is roughly linear for the first type and is nearly parallel and slightly staggered for the third type. We also found that the first hyperpolarizabilities for the linear dimers are larger than those obtained from the sum of the hyperpolarizability tensors for the individual monomers and that those for the parallel dimers are smaller. These findings led us to conclude that the noncentrosymmetric arrangement of t...

Dendrimers and Hyperbranched Polymers: Two Families of Three-Dimensional Macromolecules with Similar but Clearly Distinct Properties

Abstract Dendrimers and hyperbranched polymers are globular macromolecules that are characterized both by a highly branched structure, in which all bonds converge to a focal point or core, and a multiplicity of reactive chain-ends. Because of the obvious similarity of their building blocks, many assume that the properties of these two families of dendritic macromolecules are almost identical and that the terms “dendrimer” and “hyperbranched polymer” can be used interchangeably. This assumption is incorrect because only regular dendrimers have a precise end-group multiplicity and functionality and exhibit properties that are totally unlike those of all other families of macromolecules. For example, regular dendrimers display a maximum in the relationship between their intrinsic the applications that are contemplated for the dendritic polymers. Using living systems as a model, one must anticipate that the regular placement of reactive groups at a precise location, as opposed to throughout a structure, has great importance in terms of ultimate performance when surface and interfacial properties are involved. Therefore, just like Langmuir-Blodgett films, dendrimers belong to a special class of well-defined molecular architectures where exact structure and ultimate performance are intimately related. It is likely that regular dendrimers will continue to draw much attention in specialized applications that take advantage of their precise architecture: drug delivery, catalysis, nanoreactors, molecular devices, etc. In contrast, hyperbranched polymers will join other interesting functional polymers in applications that involve commodity materials: from coatings and adhesives to lubricants, compatibilizers, and carriers. Today, the frontiers in the chemistry of dendritic polymer are in the search for rapid methods of synthesis involving, for example, vinyl polymerizations [46, 50], the preparation of “engineered” dendritic structures, and the discovery of new properties and applications [1, 47].

Unsymmetrical three-dimensional macromolecules: preparation and characterization of strongly dipolar dendritic macromolecules

The preparation and characterization of a series of strongly dipolar monodisperse dendritic molecules ranging in molecular weight from 604 to 10 530 are described. The molecules are designed to achieve high dipole moments through the placement of electron-withdrawing cyano groups and electron-donating benzyloxy groups at segmentally opposed regions of the chain ends of the dendrimers. This is accomplished through application of the convergent growth approach in the preparation of dendritic benzyl ether fragments bearing the appropriate chain ends, followed by stepwise attachment to a linear difunctional core molecule, 4,4'-dihydroxybiphenyl. For comparison purposes, a series of symmetrical unfunctionalized dendritic benzyl ethers with molecular weights from 791 to 13 526 were also prepared

The formation and structure of polymers of the insoluble cross-linked type

Staudinger, in a series of papers (1934,1935,1936) describes the formation of an insoluble polymer of styrene by the addition to the styrene, before polymerization, of small quantities of p -divinyl-benzene. This insolubility he explains by suggesting the formation of cross-linkages of divinyl-benzene between the long thread-like molecules of polystyrene to give three-dimensional macromolecules of exceedingly high molecular weight. By using increasing proportions of divinyl-benzene Staudinger obtained a series of polymers which varied from polystyrenes soluble in benzene through polymers of high swelling capacity to completely insoluble pro­ducts. He considers that the cross-linkages of divinyl-benzene prevent the dispersion of the substance throughout the solvent, while it does not prevent the solvation of the long polystyrene chains. Thus, when few such cross-linkages are present, i. e. when the concentration of divinyl-benzene is low, the polymer will have a great tendency to go into solution through the solvation of the polystyrene chains, but will be prevented from becoming completely dispersed by the presence of the cross-linkages. The product will therefore have a high swelling capacity in those solvents in which the straight chain polystyrenes are soluble. This swelling capacity will decrease as the concentration of divinyl-benzene increases until com­pletely insoluble polymers are obtained.