A multiswitchable poly(terthiophene) bearing a spiropyran functionality: understanding photo and electrochemical control

An electroactive nitrospiropyran-substituted polyterthiophene, 2-(3,3′′-dimethylindoline-6′-nitrobenzospiropyranyl)ethyl 4,4′′-didecyloxy-2,2′:5′,2′′-terthiophene-3′-acetate, has been synthesized for the first time. The spiropyran, incorporated into the polymer backbone by covalent attachment to the alkoxyterthiophene monomer units, leads to multiple coloured states as a result of both electrochemical isomerization of the spiropyran moiety to merocyanine forms as well as electrochemical oxidation of the polyterthiophene backbone and the merocyanine substituents. While electrochemical polymerization of the terthiophene monomer could occurs without the apparent oxidation of the spiropyran, the subsequent electrochemistry is complex and clearly involves this substituent. In order to understand this complex behaviour, the first detailed electrochemical study of the oxidation of the precursor spiropyran, 1-(2-hydroxyethyl)-3,3-dimethylindoline-6’-nitrobenzospiropyran, was undertaken, showing that, in solution, an irreversible electrochemical oxidation of the spiropyran occurs leading to reversible redox behaviour of at least two merocyanine isomers. With these insights, an extensive electrochemical and spectroelectrochemical study of the nitrospiropyran-substituted polyterthiophene films reveals an initial irreversible electrochemical oxidative ring opening of the spiropyran to oxidized merocyanine. Subsequent reduction and cyclic voltammetry of the resulting nitromerocyanine-substituted polyterthiophene film gives rise to the formation of both merocyanine π-dimers or oligomers and π-radical cation dimers, between polymer chains. Although merocyanine formation is not electrochemically reversible, the spiropyran can be photochemically regenerated, at least in part, through irradiation with visible light. SEM and AFM images support the conclusion that the bulky spiropyran substituent is electrochemically isomerizes to the planar merocyanine moiety affording a smoother polymer film. The conductivity of the freestanding polymer film was found to be 0.4 S cm-1

In vitro growth and differentiation of primary myoblasts on thiophene based conducting polymers

Polythiophenes are attractive candidate polymers for use in synthetic cell scaffolds as they are amenable to modification of functional groups as a means by which to increase biocompatibility. In the current study we analysed the physical properties and response of primary myoblasts to three thiophene polymers synthesized from either a basic bithiophene monomer or from one of two different thiophene monomers with alkoxy functional groups. In addition, the effect of the dopants pTS- and ClO4 - was investigated. In general, it was found that pTS- doped polymers were significantly smoother and tended to be more hydrophilic than their ClO 4 - doped counterparts, demonstrating that the choice of dopant significantly affects the polythiophene physical properties. These properties had a significant effect on the response of primary myoblasts to the polymer surfaces; LDH activity measured from cells harvested at 24 and 48 h post-seeding revealed significant differences between numbers of cells attaching to the different thiophene polymers, whilst all of the polymers equally supported cell doubling over the 48 h period. Differences in morphology were also observed, with reduced cell spreading observed on polymers with alkoxy groups. In addition, significant differences were seen in the polymers\u27 ability to support myoblast fusion. In general pTS- doped polymers were better able to support fusion than their ClO4 - doped counterparts. These studies demonstrate that modification of thiophene polymers can be used to promote specific cellular response (e.g. proliferation over differentiation) without the use of biological agents. 2013 The Royal Society of Chemistry

Novel polythiophene materials for bionic applications

Bionics is the revolutionary area of medical research concerned with the interface between biology and electronics. For the next generation of bionic devices, new electromaterials need to be developed. Conducting polymers are excellent candidate electromaterials for these bionic devices. Due to their ease of synthesis and functionalisation, polythiophenes are one of the best candidate conducting polymers. Here the synthesis and optimisation of novel polythiophene materials for bionic applications was investigated. The research focused on four key properties that are desirable for bionic materials; functionality, biodegradability, processability and biocompatibility. The introduction of functionality into polythiophene materials was demonstrated through the synthesis of several terthiophene building blocks. Functionalisation of these terthiophene building blocks was demonstrated by the attachment of amino acid, barbituric acid and spiropyran functionalities. The functionalised terthiophenes could be polymerised to yield functional polymers. Spiropyran functionalised polymers were of particular interest as conformational changes in these materials could be electrically induced. The development of biodegradable conducting polymers was initially investigated with the development of conducting azomethine linked thiophene oligomers. The stability of azomethine materials was investigated and they were found to be susceptible to acid hydrolysis. Then the synthesis of several novel terthiophene and sexithiophene oligomers via Stille coupling as precursors to biodegradable conducting polymers was explored. Films and aligned electrospun fibres of ester functionalised poly(octanoic acid 2- thiophen-3-yl ethyl ester) were fabricated. Further functionalisation of these structures was demonstrated through hydrolysis of the ester and functionalisation of the films and fibres with ferrocene acid chloride. The electrochemistry and surface properties of these structures was compared with the hydrolysed structures being more hydrophilic and showing a much greater electrochemical response in aqueous electrolyte. The biocompatibility of several polythiophene materials was tested with C2C12 muscle cells, which were shown to be compatible with these materials. Smoother spin coated films were seen to be better scaffolds than rough electropolymerised films, for supporting cell differentiation of sensitive ROSA primary muscle cells. Aligned polythiophene fibre structures on gold Mylar were investigated for controlling the direction of ROSA cell differentiation. Fibres spaced between 15-100 μm apart gave the best directional cues to the cells and most efficiently promote alignment of myotubes. The insights and knowledge gained during this study will help in the development and application of conducting polymer materials for bionic applications

Reaction injection molding of hydrophilic-in-hydrophobic femtolitre-well arrays

Patterning of micro- and nanoscale topologies and surface properties of polymer devices is of particular importance for a broad range of life science applications, including cell-adhesion assays and highly sensitive bioassays. The manufacturing of such devices necessitates cumbersome multiple-step fabrication procedures and results in surface properties which degrade over time. This critically hinders their wide-spread dissemination. Here, we simultaneously mold and surface energy pattern microstructures in off-stoichiometric thiol-ene by area-selective monomer self-assembly in a rapid micro-reaction injection molding cycle. We replicated arrays of 1,843,650 hydrophilic-in-hydrophobic femtolitre-wells with long-term stable surface properties and magnetically trapped beads with 75% and 87.2% efficiency in single- and multiple-seeding events, respectively. These results form the basis for ultrasensitive digital biosensors, specifically, and for the fabrication of medical devices and life science research tools, generally.status: publishe

In vitro growth and differentiation of primary myoblasts on thiophene based conducting polymers

Polythiophenes are attractive candidate polymers for use in synthetic cell scaffolds as they are amenable to modification of functional groups as a means by which to increase biocompatibility. In the current study we analysed the physical properties and response of primary myoblasts to three thiophene polymers synthesized from either a basic bithiophene monomer or from one of two different thiophene monomers with alkoxy functional groups. In addition, the effect of the dopants pTS− and ClO4− was investigated. In general, it was found that pTS− doped polymers were significantly smoother and tended to be more hydrophilic than their ClO4− doped counterparts, demonstrating that the choice of dopant significantly affects the polythiophene physical properties. These properties had a significant effect on the response of primary myoblasts to the polymer surfaces; LDH activity measured from cells harvested at 24 and 48 h post-seeding revealed significant differences between numbers of cells attaching to the different thiophene polymers, whilst all of the polymers equally supported cell doubling over the 48 h period. Differences in morphology were also observed, with reduced cell spreading observed on polymers with alkoxy groups. In addition, significant differences were seen in the polymers’ ability to support myoblast fusion. In general pTS− doped polymers were better able to support fusion than their ClO4− doped counterparts. These studies demonstrate that modification of thiophene polymers can be used to promote specific cellular response (e.g. proliferation over differentiation) without the use of biological agents