Archive for the ‘Paper of the Week’ Category

Paper of the week: White light emission of multi-chromophore photoluminescent nanoparticles

‘Fluorescence is a powerful tool in a variety of applications, ranging from optical to analytical materials (detection of small molecules and protein studies) because of its exquisite sensitivity, cost-effectiveness, facile operation, and superb spatial and temporal resolutions. Fluorescent organic nanoparticles derived from conjugated polymers have attracted significant interest due to their variable optical, electronic, and other properties such as facile preparation and functionalization. Among conjugated polymers used in organic nanoparticles, polyfluorene (PF) and its derivatives are considered to be of special interest because of their thermal/chemical stability, high fluorescence quantum yield and significant charge carrier mobility.’

Graphical abstract: White light emission of multi-chromophore photoluminescent nanoparticles using polyacrylate scaffold copolymers with pendent polyfluorene groups

In this work, Ling, Hogen-Esch and co-workers reported a styrene-type macromonomer containing polyfluorene pendent group (PFS), which allowed the convenient synthesis of well-defined copolymers of PFS with t-butyl acrylate by both RAFT and ATRP polymerization methods. After hydrolysis, the amphiphilic copolymers self-assembled into photoluminescent nanoparticles in aqueous solution. When doped with selected dyes, the nanoparticles emitted light with tunable colors as well as white via Förster energy transfer from the excited pendent polyfluorene groups.

White light emission of multi-chromophore photoluminescent nanoparticles using polyacrylate scaffold copolymers with pendent polyfluorene groups by Chao Deng, Peng Jiang, Xiaobin Shen, Jun Ling and Thieo E. Hogen-Esch, Polym. Chem. 2014, 5, 5109-5115.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine used as a transdermal penetration enhancer

‘The stratum corneum (SC) of skin is the main barrier against transdermal drug penetration, and poor permeability in the SC limits the usefulness of the transdermal drug administration route. Generally, drug permeation through the SC could be increased with skin permeation enhancers. Currently, enhancers most frequently used in transdermal drug delivery systems are neatly divided into three categories. One is organic solvents such as ethanol, propylene glycol and dimethyl sulfoxide. The second is surfactants such as cationic, anionic and nonionic surfactants. The last category is laurocapram and its derivative series. Nevertheless, their potential shortcomings have gradually been recognized, for their great irritation to skin or causing harm to organs. The practical use of enhancers requires the careful balancing of skin toxicity and permeation enhancement benefits’

Graphical abstract: In vitro and in vivo application of hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine used as a transdermal penetration enhancer

In this work, Xing and co-workers developed a new penetration enhancer based on hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine (HP-β-CD–PEI). Its penetration mechanism relied on a change of the secondary structure of keratin in the stratum corneum to enhance the transcutaneous permeation of drugs. By using a series of in vitro and in vivo methods, this cationic polymer demonstrated great biocompatibility and could be valuable for topical delivery as a penetration enhancer to improve the penetration of hydrophilic drugs.

In vitro and in vivo application of hydroxypropyl-β-cyclodextrin-grafted polyethyleneimine used as a transdermal penetration enhancer by Ke Wang, Yan Yan, Guilan Zhao, Wei Xu, Kai Dong, Cuiyu You, Lu Zhang and Jianfeng Xing, Polym. Chem. 2014, 5, 4658-4669.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Hybrid organic–inorganic copolymers with self-healing properties

‘Over the last decade, a broad range of self-healing materials has emerged. Such systems, when they have been damaged, heal themselves either spontaneously or with the aid of a stimulus. Several of these materials draw their inspiration from the design of biological materials. On the other hand, hybrid materials or nanocomposites, defined as composites constituted of two components, one inorganic and the other one organic in nature mixed at the nanometer level, have attracted strong interest both in academia and industry. The combination at the nanoscale of organic and inorganic components leads to highly homogeneous materials, which develop extended organic–inorganic interfaces with tuneable chemical organic–inorganic bonds from weak to strong interactions.’

Graphical abstract: Nano-building block based-hybrid organic–inorganic copolymers with self-healing properties

In this work, Rozes and co-workers prepared new dynamic materials, that can repair themselves after strong damage, by hybridization of polymers with structurally well-defined nanobuilding units. The controlled design of cross-linked poly(n-butyl acrylate) (PnBA) has been performed by introducing a very low amount of a specific tin oxo-cluster. Sacrificial domains with non-covalent interactions (i.e. ionic bonds) developed at the hybrid interface play a double role. Such interactions are strong enough to cross-link the polymer, which consequently exhibits rubber-like elasticity behavior, and labile enough to enable, after severe mechanical damage, dynamic bond recombination leading to an efficient healing process at room temperature. In agreement with the nature of the reversible links at the hybrid interface, the healing process can speed up considerably with temperature .

Nano-building block based-hybrid organic–inorganic copolymers with self-healing properties by F. Potier, A. Guinault, S. Delalande, C. Sanchez, F. Ribot and L. Rozes, Polym. Chem. 2014, 5, 4474-4479.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Cu(0)-mediated polymerization using high-throughput experimentation

‘Over the past decades, several types of controlled radical polymerization methods have been developed. The most popular methods are atom transfer radical polymerization (ATRP), reversible addition–fragmentation chain transfer (RAFT) polymerization and nitroxide mediated polymerization (NMP). One of the more recently developed techniques, which appears to be very promising, is Cu(0)-mediated polymerization, known variously as SET-LRP or SARA-ATRP. Recent publications have shown significant progress in the area of Cu(0)-mediated polymerization. Among the monomers that have been polymerized in a controlled manner via Cu(0)-mediated polymerization are acrylates, methacrylates, vinyl chloride and (meth)acrylamides. However, for each monomer the polymerization conditions should be optimized, which is in general a very time consuming task.’

Graphical abstract: Cu(0)-mediated polymerization of hydrophobic acrylates using high-throughput experimentation

In this work, Hoogenboom and co-workers report the optimization of the Cu(0)-mediated polymerization of n-butyl acrylate (BA) and 2-methoxyethyl acrylate (MEA) via Cu(0)-mediated polymerization using an automated parallel synthesizer.  Using this robot, up to 16 kinetic reactions could be performed in parallel, resulting in a fast screening of different reaction conditions. Several parameters were optimized to determine the optimal reaction conditions with regard to control over the polymerization and reaction rate. These optimal reaction conditions were then used for the one-pot two-step synthesis of diblock copolymers by sequential monomer addition. Altogether, this work shows the power of high-throughput optimization of Cu(0)-mediated polymerization reaction conditions. As such, it may serve to accelerate optimization of Cu(0)-mediated polymerization conditions and aid in gaining fundamental understanding of the effects of various parameters on the Cu(0)-mediated polymerization.

Cu(0)-mediated polymerization of hydrophobic acrylates using high-throughput experimentation by Lenny Voorhaar, Sofie Wallyn, Filip E. Du Prez and Richard Hoogenboom, Polym. Chem. 2014, 5, 4268-4276.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Fully biodegradable antibacterial hydrogels

‘Bacterial infection is a serious problem in many areas, especially those involving the use of biomaterials. According to World Health Organization (WHO) statistics, at any time, over 1.4 million people worldwide suffer from infectious complications acquired in hospital, which have much to do with the use of medical devices. Hydrogels are three-dimensional polymer networks that are able to retain a large fraction of aqueous solvent within their structures. Due to their high water content and soft consistency, which is similar to natural tissue, hydrogels resemble natural living tissue more than any other class of synthetic biomaterial. Therefore, hydrogels have received extraordinary attention as biomaterials for use in biomedical applications, such as tissue engineering, wound dressing materials, immunoisolation16 and drug delivery. Thus, fabricating hydrogels with antibacterial properties is crucial for the biomedical field.’

Graphical abstract: Fully biodegradable antibacterial hydrogels via thiol–ene “click” chemistry

In this work, Zhu and co-workers prepared fully biodegradable antimicrobial hydrogels via a thiol–ene “click” reaction under human physiological conditions using multifunctional poly(ethylene glycol) (PEG) derivatives as precursors. Water soluble and degradable PEG derivatives with multi-enes and multi-thiols, respectively, were synthesized by polycondensation of oligo(ethylene glycol) (OEG) with “clickable” monomers. Ammonium groups with long alkyl chains were incorporated into one of the precursors covalently, using dodecyl bis(2-hydroxyethyl) methylammonium chloride as a comonomer.  These types of cationic PEG-type hydrogels showed strong antibacterial abilities against both Gram- negative and Gram-positive bacteria due to the ammonium moieties. Moreover, the hydrogel with fewer ammonium moieties still possessed significant antibacterial abilities, but low toxicity, and has the potential to be used as a medical material.

Fully biodegradable antibacterial hydrogels via thiol–ene “click” chemistry by Hong Du, Guangyu Zha, Lilong Gao, Huan Wang, Xiaodong Li, Zhiquan Shena and Weipu Zhu, Polym. Chem. 2014, 5, 4002-4008.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Macroporous antibacterial hydrogels with tunable pore structures

‘Porous hydrogels with well-defined pore structure have attracted considerable attention due to their multifarious applications such as scaffolds for tissue engineering, vehicles for drug delivery and self-healing materials. CO2-in-water (C/W) high internal phase emulsions (HIPEs) and oil-in-water (O/W) HIPEs are considered as very effective templates to produce such kinds of high porosity hydrogels… In most cases, the O/W HIPEs are stabilized by large amounts of surfactants at high concentrations of 5–50 vol%, where the enormous quantity of surfactants presents economic and potential environmental problems. Therefore, much attention has been focused on the Pickering-HIPEs, which are stabilized by colloidal particles instead of traditional surfactants.’

Graphical abstract: Macroporous antibacterial hydrogels with tunable pore structures fabricated by using Pickering high internal phase emulsions as templates

In this work, Deng, Wang and co-workers prepared Artemisia argyi oil (AAO)-loaded macroporous antibacterial hydrogels by polymerization of oil-in-water Pickering HIPEs. The HIPEs were stabilized by the synergy of hydrophilic silica nanoparticles (N20) and surfactant Tween 80. The void interconnectivity and pore size of the hydrogels can be readily tailored by varying the concentrations of N20 nanoparticles and Tween 80. The in vitro release of the AAO-loaded hydrogels with different inner morphologies was evaluated and showed controlled release activity. The antibacterial activity of the AAO-loaded hydrogel was evaluated against Staphylococcus aureus and Escherichia coli. This kind of hydrogel exhibited excellent and long-term antibacterial activity indicating its potential use in biomedical and infection prevention applications.

Macroporous antibacterial hydrogels with tunable pore structures fabricated by using Pickering high internal phase emulsions as templates by Shengwen Zou, Zengjiang Wei, Yang Hu, Yonghong Deng, Zhen Tonga and Chaoyang Wang, Polym. Chem. 2014, 5, 4227-4234.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Bio-based covering materials for surface design

‘Innovative approaches for the syntheses of polymeric structures bearing polypeptides have received enormous interest in the fields of biomedicine, drug delivery, biomineralization, nanoscale self-assembly, and tissue engineering. The conjugation of synthetic polymers with polypeptides can result in novel biomaterials that possess the following characteristics: biorecognition-like properties similar to antibody/antigen interactions, biodegradability properties, biocatalyst activity, and compatibility with blood and/or tissue.’

Graphical abstract: Electrochemical deposition of polypeptides: bio-based covering materials for surface design

In this article, Endo, Timur, Yagci and co-workers reported on a simple and efficient approach for the electrochemical deposition of polypeptides as bio-based covering materials for surface design. The method involves N-carboxyanhydride (NCA) ring-opening polymerization from its precursor to form a thiophene-functionalized polypeptide macromonomer (T-Pala), followed by electropolymerization. The obtained conducting polymer, namely polythiophene-g-polyalanine (PT-Pala), was characterized and utilized as a matrix for biomolecule attachment. The biosensing applicability of PT-Pala was also investigated by using glucose oxidase (GOx) as a model enzyme to detect glucose. Finally, the antimicrobial activities of newly synthesized T-Pala and PT-Pala were also evaluated. Interestingly, this technique is experimentally facile and can be applied to various types of polypeptides.

Electrochemical deposition of polypeptides: bio-based covering materials for surface design by Huseyin Akbulut, Murat Yavuz, Emine Guler, Dilek Odaci Demirkol, Takeshi Endo, Shuhei Yamada, Suna Timur and Yusuf Yagci, Polym. Chem. 2014, 5, 3929-3936.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: A new platform for synthesis of functional aliphatic polyesters

‘Functional polymers open up applications with endless possibilities, where properties can be tailored, altered, and/or maintained over the complete lifetime of the material. In light of this, the focus today is on conferring function to the main chain of the polymer. One class of polymers that is inherently of great value for many applications is aliphatic polyesters; because of their ester functionality, they most often degrade within a reasonable time frame. Unfortunately, many of these monomers lack sites that allow alterations and modifications of the polymer backbone. Therefore, a major scientific focus has been on imparting different functionalities to aliphatic polyesters.’

Graphical abstract: Establishing α-bromo-γ-butyrolactone as a platform for synthesis of functional aliphatic polyesters – bridging the gap between ROP and SET-LRP

In this article, Albertsson and co-workers felt inspired to use γ-lactones as inexpensive and straightforward monomers that can bestow the desired functionality on commonly used aliphatic polyester. More specifically, they used α-bromo-γ-butyrolactone (αBrγBL) as a comonomer with ε-caprolactone (εCL) or L-lactide (LLA) to produce copolymers with active and available grafting sites, e.g., for SET-LRP, where the choice of the grafting monomers is limited only by one’s imagination. The authors believe that αBrγBL inherently holds all the prerequisites to act as a platform monomer for the synthesis of functional aliphatic polyesters, i.e., it is inexpensive, available, and able to form isolated grafting sites along the polymer chain. The incorporation of isolated αBrγBL is a feature that makes this class of copolymers unique and is considered to provide a route to the “perfect graft copolymer” with a degradable backbone.

Establishing α-bromo-γ-butyrolactone as a platform for synthesis of functional aliphatic polyesters – bridging the gap between ROP and SET-LRP by Peter Olsén, Jenny Undin, Karin Odeliusa and Ann-Christine Albertsson, Polym. Chem. 2014, 5, 3847-3854.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Nanosponges for intravenous and oral drug delivery of anticancer drugs

‘Biodegradable polymeric nanoparticles utilized as delivery agents have been established as an effective strategy for the improvement of numerous therapeutic applications. Nanoparticles are excellent drug delivery vehicles that are investigated mostly due to their ability to optimize the targeting and bioavailability of drugs that are otherwise too toxic and insoluble… Ideally, a single dose of these drugs formulated in a nanoparticle drug delivery system would not only allow for a high dissolution of the drug, but also release an exact amount of drug in a specific amount of time to meet the individual needs of any patient.’

Graphical abstract: An assessment of nanosponges for intravenous and oral drug delivery of BCS class IV drugs: Drug delivery kinetics and solubilization

In this paper, Harth and co-workers reported on the synthesis of biodegradable nanoparticles capable of paclitaxel entrapment and demonstrated the ability to control release of paclitaxel by adjusting the single parameter of the particles’ crosslinking density. Additionally, particles with different densities can be mixed to yield various rates of release that can be fast or slow depending on the specific application. The ability of these particles to withstand simulated gastric fluid allows for the possibility of an oral drug delivery route.

An assessment of nanosponges for intravenous and oral drug delivery of BCS class IV drugs: Drug delivery kinetics and solubilization by David M. Stevens, Kelly A. Gilmore and Eva Harth Polym. Chem. 2014, 5, 3551-3554.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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Paper of the week: Towards polybutadiene brushes featuring pendant polyester side-chains

Ring-opening metathesis polymerization (ROMP) has emerged as a powerful tool to prepare graft copolymers (also denoted as bottlebrush copolymers) using three well-known strategies: grafting-from, grafting-onto, and grafting-through routes. The most often used method, namely the grafting-through (or macromonomer) route, relies on the ROMP of well-defined polymers bearing a “ROMP-able” strained ring such as norbornene or oxanorbornene.

Graphical abstract: Synthesis and polymerization of cyclobutenyl-functionalized polylactide and polycaprolactone: a consecutive ROP/ROMP route towards poly(1,4-butadiene)-g-polyesters

Driven by the interest in developing new efficient methodologies to prepare well-defined grafted poly(1,4-butadiene)s, Fontaine and co-workers used in the present work a consecutive organocatalyzed ring-opening polymerization (ROP)/ROMP route to prepare poly(1,4-butadiene)-g-polyesters from cyclobutenyl macromonomers bearing one or two polyester segment(s) derived from L-lactide (LA) or ε-caprolactone (CL). The products resulting from this strategy represent the first examples of poly(1,4-butadiene)-g-polyesters through the macromonomer route. These results pave the way for more complicated macromolecular architectures, e.g., by modification of the side-chain termini. Moreover, the hydrolytic (bio)degradation potential of the side chains (that can be used as sacrificial domains) of those bottlebrush copolymers makes them attractive candidates to be used for the preparation of complex hollowed nanostructures.

Synthesis and polymerization of cyclobutenyl-functionalized polylactide and polycaprolactone: a consecutive ROP/ROMP route towards poly(1,4-butadiene)-g-polyesters by Flavien Leroux, Véronique Montembault, Sagrario Pascual, William Guerin, Sophie M. Guillaume and Laurent Fontaine Polym. Chem.2014, 5, 3476-3486.

Julien Nicolas is a web-writer and advisory board member for Polymer Chemistry. He currently works at Univ. Paris-Sud (FR) as a CNRS researcher.

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