Polymer Chemistry Blog

In this article, Vicent, Salmaso, Alexander and co-workers prepared a modular and effective controlled release system, based on polymers designed to respond to the pH-changes that occur in tissues affected by peculiar disease. The individual blocks were composed of (a) permanently hydrophilic chains with neutral functionality and (b) acrylate polymers with weakly basic side-chains. Variation in co-monomer content, molar mass and block ratios/compositions led to a range of pH-responses, manifested through reversible self-assembly into micelles and/or polymersomes. These transitions were tuned to achieve environmental responses in a pH range from 5–7. The ability of the systems assembled with these polymers to act as pH-responsive containers was shown by DNA encapsulation and release studies, and their potential for application as vehicle for drug delivery was proved by cell metabolic activity and cell uptake measurements.

Synthesis and characterization of variable conformation pH responsive block co-polymers for nucleic acid delivery and targeted cell entry by Teresa Matini, Nora Francini, Anna Battocchio, Sebastian G. Spain, Giuseppe Mantovani, Maria J. Vicent, Joaquin Sanchis, Elena Gallon, Francesca Mastrotto, Stefano Salmaso, Paolo Caliceti and Cameron Alexander Polym. Chem. 2014, 5, 1626-1636.

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.

In this publication, Themistou, Battaglia and Armes reported on the one-pot metal-free ring-opening polymerization (ROP)–reversible addition–fragmentation chain transfer (RAFT) synthesis of biocompatible linear and branched amphiphilic diblock copolymers based on a biodegradable aliphatic polyester (PLA) and methacrylic monomers (such as 2-(dimethylamino)ethyl methacrylate (DMA) or oligo(ethylene glycol) methacrylate (OEGMA)), using a novel hydroxyl-functionalized trithiocarbonate-based chain transfer agent. These amphiphilic diblock copolymers self-assembled in dilute aqueous solution, leading to various copolymer morphologies depending on the block compositions. Two novel disulfide-functionalized PLA-branched block copolymers were also synthesized using simultaneous ROP of LA and RAFT copolymerization of OEGMA or DMA with a disulfide-based dimethacrylate. The disulfide bonds were reductively cleaved using tributyl phosphine to generate reactive thiol groups. Thiol–ene chemistry was utilized for further derivatization with thiol-based biologically important molecules and heavy metals for tissue engineering or bioimaging applications, respectively.

Facile synthesis of thiol-functionalized amphiphilic polylactide–methacrylic diblock copolymers by Efrosyni Themistou, Giuseppe Battaglia and Steven P. Armes Polym. Chem. 2014, 5, 1405-1417.

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.

In this study, Voit, Appelhans and co-workers demonstrated the successful fabrication of biohybrid structures tailored by non-covalent interactions for potential biochemical applications. Using avidin-biotin conjugation as the deciding non-covalent interaction step, different nanometer-sized biohybrid structures can be established by using different molar interaction ratios between mono-, bi- and tetravalent biotinylated glycodendrimers and avidin.  The biotin ligand’s spacer length, its chemical structure and the degree of biotin functionalization were shown to be essential parameters in the formation of nanostructures with avidin having a controlled composition and size dimension up to 100 nm. Biohybrid structures with avidin as a central unit required monovalent glycodendrimers with PEG-linked biotin, while bi- and tetravalent glycodendrimers with short alkyl-linked biotin ligands were more efficient than their counterparts with longer PEG–biotin ligands in the fabrication of defined biohybrid structures (diameters up to 100 nm) with avidin as a bridging unit.  Not only does this study elucidate the formation of biohybrid structures between avidin and biotinylated glycodendrimers in the conjugation solution, but it also provides deeper insight into these supramolecular (bio)polymeric structures from a general point of view.

Biohybrid structures consisting of biotinylated glycodendrimers and proteins: influence of the biotin ligand’s number and chemical nature on the biotin–avidin conjugation by Franka Ennen, Susanne Boye, Albena Lederer, Mihaela Cernescu, Hartmut Komber, Bernhard Brutschy, Brigitte Voit and Dietmar Appelhans Polym. Chem. 2014, 5, 1323-1339.

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.

In this study, Poly, Lalevée, Matyjaszewski and co-workers reported on a new approach for the synthesis of dynamic covalent networks exhibiting self-healing properties under UV irradiation. The procedure combined ATRP and click chemistry as two versatile synthetic tools for the design of well-defined peripherally functionalized star-like oligomers followed by their covalent bonding with responsive alkoxyamine crosslinking agents. The incorporation of alkoxyamine linkages into the junctions between the stars enabled their subsequent cleavage under irradiation. Beyond self-healing materials, the concept developed in the present study might be of interest regarding aging issues of polymeric materials due to UV radiation.

Introduction of self-healing properties into covalent polymer networks via the photodissociation of alkoxyamine junctions by Siham Telitel, Yoshifumi Amamoto, Julien Poly, Fabrice Morlet-Savary, Olivier Soppera, Jacques Lalevée and Krzysztof Matyjaszewski Polym. Chem. 2014, 5, 921-930.

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.