Ioan Cianga

Review paper: Progress in the Field of Conducting Polymers for Tissue Engineering Applications

This review focuses on one of the most exciting applications area of conjugated conducting polymers, which is tissue engineering. Strategies used for the biocompatibility improvement of this class of polymers (including biomolecules’ entrapment or covalent grafting) and also the integrated novel technologies for smart scaffolds generation such as micropatterning, electrospinning, self-assembling are emphasized. These processing alternatives afford the electroconducting polymers nanostructures, the most appropriate forms of the materials that closely mimic the critical features of the natural extracellular matrix. Due to their capability to electronically control a range of physical and chemical properties, conducting polymers such as polyaniline, polypyrrole, and polythiophene and/or their derivatives and composites provide compatible substrates which promote cell growth, adhesion, and proliferation at the polymer—tissue interface through electrical stimulation. The activities of different types of cells on these materials are also presented in detail. Specific cell responses depend on polymers surface characteristics like roughness, surface free energy, topography, chemistry, charge, and other properties as electrical conductivity or mechanical actuation, which depend on the employed synthesis conditions. The biological functions of cells can be dramatically enhanced by biomaterials with controlled organizations at the nanometer scale and in the case of conducting polymers, by the electrical stimulation. The advantages of using biocompatible nanostructures of conducting polymers (nanofibers, nanotubes, nanoparticles, and nanofilaments) in tissue engineering are also highlighted.

Immobilization of invertase and glucose oxidase in poly 2-methylbutyl-2-(3-thienyl) acetate/polypyrrole matrices

Abstract Immobilization of invertase and glucose oxidase in conducting polypyrrole and copolymers of poly 2-methylbutyl-2-(3-thienyl) acetate with pyrrole were achieved via electrochemical method. Sodium dodecyl sulphate was found to be the most suitable supporting electrolyte. Maximum reaction rate, Michaelis–Menten constant and optimum temperatures were determined for native and immobilized enzymes. Storage and operational stabilities of enzyme electrodes were also investigated.

Poly(p-phenylene) graft copolymers with polytetrahydrofuran/polystyrene side chains

Abstract 1,4-Dibromo-2,5-bis(bromomethyl)benzene was used as a bifunctional initiator in cationic ring opening polymerization (CROP) of tetrahydrofuran. The resulting macromonomer, with a central 2,5-dibromobenzene ring, was reacted in combination with 2,5-dihexylbenzene-1,4-diboronic acid by a Suzuki coupling, in the presence of Pd(PPh3)4 as catalyst, leading to a poly(p-phenylene) (PPP) with alternating polytetrahydrofuran (PTHF) and hexyl side chains. A polystyrene (PSt) based macromonomer with a central benzene ring bearing cyclic boronic acid propanediol diester groups, synthesized by atom transfer radical polymerization (ATRP), was also used as partner for PTHF in the cross-coupling reaction. A PPP with alternating PSt and PTHF side chains was obtained. PTHF macromonomer was also homopolymerized by a Yamamoto reaction. The resulting PPPs have high solubility in common organic solvents at room temperature. The new polymers were characterized by GPC, 1H NMR, 13C NMR, IR and UV analysis. Thermal behavior of the precursor PTHF macromonomer and the final polyphenylenes were investigated by TGA and DSC analyses and compared.

Synthesis of well-defined polystyrene macrophotoinitiators by atom-transfer radical polymerization†

New mono- and bifunctional atom-transfer radical polymerization (ATRP) initiators were synthesized by the condensation of 2-bromopropanoyl bromide with 2-hydroxy-2-methyl-1-phenyl propan-1-one (HMPP) and 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl propan-1-one (HE-HMPP), respectively and characterized. The ATRP of styrene (St) in bulk at 110 °C by means of these initiators in conjunction with a cuprous complex Cu(I)Br/bipyridine yields polystyrenes with photoactive alkoxy phenylketone groups. Gel permeation chromatography, spectroscopic and photodegradation studies revealed that the initiation efficiency was quantitative and low- polydispersity polystyrenes with photoinitiator functionality in the end or middle of the chain were obtained.

Synthesis and characterization of comb-like polyphenylenes via Suzuki coupling of polystyrene macromonomers prepared by atom transfer radical polymerization

Abstract 1,4-Dibromo-2,5-bis(bromomethyl)benzene was used as initiator in atom transfer radical polymerization of styrene in conjunction with CuBr/2,2′-bipyridine as catalyst. The resulting macromonomer, with a central 2,5 dibromobenzene ring and the degree of polymerization of 16 at each side, was used in combination with 2,5-dihexylbenzene-1,4-diboronic acid, for a Suzuki coupling in the presence of Pd(PPh3)4 as catalyst. The obtained polyphenylene, with alternating polystyrene and hexyl side chains, has high solubility in common organic solvents at room temperature. The new polymer was characterized by GPC, 1 H-NMR, 13 C-NMR, IR and UV analysis. Thermal behavior of the precursor polystyrene macromonomer and the final polyphenylene was investigated by thermogravimetric analysis and differential scanning calorimeter/calorimetry analyses and compared.

The synthesis and targeting of PPP-type copolymers to breast cancer cells: Multifunctional platforms for imaging and diagnosis

Herein, we demonstrate the synthesis and application of water-soluble, biomolecule conjugated PPP copolymers bearing poly(ethylene glycol) (PEG) side chains as fluorescent probes for the in vitro imaging of cancer cells. The targeting of fluorescent polymers to breast cancer cells allows effective visualization and discrimination of MCF7 cells from human mammary epithelial cells. Furthermore, these materials are also suitable for efficient radiolabeling via125I which enables dual-modality holding the possibility of both radioactive and fluorescence imaging in cancer diagnosis applications.

Synthesis of new conjugated polymers with schiff base structure containing pyrrolyl and naphthalene moieties and hmo study of the monomers reactivity

Abstract This paper reports a novel method for the synthesis of wholly aromatic polyazomethines by oxidative polymerization of monomers having a preformed azomethine linkage. Two monomers having a Schiff base type structure: N -pyrrolylmethylen-1-aminonaphthalene ( I ) and N -pyrrolylmethylen-2-aminonaphthalene ( II ) were synthesized by coupling of pyrrole 2-carboxaldehyde with 1- and 2-aminonaphthalene, respectively. Their cation-radical polymerization was performed by chemical oxidation with ammonium persulfate and iron trichloride. Aromatic polyazomethines were obtained with good thermal properties. The structures of the polymers were studied by IR spectroscopy and were correlated with Huckel molecular orbital calculations for evaluating the monomers reactivity and the most probable linkage sites of the monomer units in the polymer chain.

Synthesis of block copolymers by combination of photoinduced and atom transfer radical polymerization routes

Abstract Block copolymers of methyl methacrylate (MMA) and styrene (St) were obtained by the combination of two different free radical polymerization processes, namely photoinduced and atom transfer radical polymerization (ATRP) methods. In the first step, hydroxy terminated polymers were prepared by photoinitiated polymerization of MMA in the presence of N,N′-dimethylethanolamine and benzophenone as the initiating system and subsequently converted to bromine ended poly(methyl methacrylate) by the esterification of the resulting polymer with 2-bromo-propionylbromide. The functionalized polymers thus prepared were used as initiators in ATRP of St, in bulk, in conjunction with CuBr/2,2′-bipyridine as catalyst. The GPC and 1 H -NMR analysis, and the kinetic studies indicate a fully controlled/“living” radical polymerization which results in the formation of block copolymers with narrow polydispersities.

Hybrid materials consisting of an all-conjugated polythiophene backbone and grafted hydrophilic poly(ethylene glycol) chains

Organic hybrid materials consisting of an all-conjugated polythiophene backbone and well-defined poly(ethylene glycol) (PEG) grafted chains have been prepared by anodic polymerization of chemically synthesized macromonomers. The latter consist of a pentathiophene sequence in which the central ring bears a PEG chain with Mw = 1000 or 2000 at the 3-position. The influence of the polymerization potential, the length of the PEG branches and the dopant agent on the structure and properties of the graft copolymers has been examined. The chemical structure of the grafted materials has been corroborated by FTIR and X-ray photoelectron spectroscopies. Scanning electron microscopy and atomic force microscopy studies reveal that the morphology and topography of these materials are influenced by the above mentioned factors, even though homogeneous films showing a compact distribution of nanoaggregates, very flat surfaces (i.e. roughness < 15 A) and nanometric thickness (i.e. 100–500 nm) were obtained in all cases. Cyclic voltammetry assays have been used to determine the presence of charged species, the electroactivity, the electrostability and the formation of cross-links. The electrochemical stability of the copolymer with grafted PEG chains of Mw = 1000 has been found to increase with the number of consecutive oxidation–reduction cycles (self-electrostabilizing behavior). Finally, a preliminary investigation into the applicability of these hybrid materials as active surfaces for the selective adsorption of proteins is presented.

Chemical synthesis of some Schiff base-type polymers containing pyrrole units

SummaryThe synthesis of three Schiff-base type monomers containing pyrrole units was performed. Their polymerization was carried out by chemical oxidation with (NH4)2S2O8. Some preliminary thermal and electrical properties were determined.