Barrier films to control loss of 9,10-anthraquinone-2-sulphonate dopant from PEDOT films during electrochemical transitions

Nanoparticle Doped PEDOT for Enhanced Electrode Coatings and Drug Delivery

In order to address material limitations of biologically interfacing electrodes, modified silica nanoparticles are utilized as dopants for conducting polymers. Silica precursors are selected to form a thiol modified particle (TNP), following which the particles are oxidized to sulfonate modified nanoparticles (SNPs). The selective inclusion of hexadecyl trimethylammonium bromide allows for synthesis of both porous and nonporous SNPs. Nonporous nanoparticle doped polyethylenedioxythiophene (PEDOT) films possess low interfacial impedance, high charge injection (4.8 mC cm-2 ), and improved stability under stimulation compared to PEDOT/poly(styrenesulfonate). Porous SNP dopants can serve as drug reservoirs and greatly enhance the capability of conducting polymer-based, electrically controlled drug release technology. Using the SNP dopants, drug loading and release is increased up to 16.8 times, in addition to greatly expanding the range of drug candidates to include both cationic and electroactive compounds, all while maintaining their bioactivity. Finally, the PEDOT/SNP composite is capable of precisely modulating neural activity in vivo by timed release of a glutamate receptor antagonist from coated microelectrode sites. Together, this work demonstrates the feasibility and potential of doping conducting polymers with engineered nanoparticles, creating countless options to produce composite materials for enhanced electrical stimulation, neural recording, chemical sensing, and on demand drug delivery.

1-(Prop-2-en-1-yl)-3-{[3-(pyridin-4-yl)-4,5-dihydroisoxazol-5-yl]methyl}-1H-anthra[1,2-d]imidazole-2,6,11(3H)-trione

The fused five- and three six-membered rings of the anthra[1,2-d]imidazole­trione part of the title compound, C₂₇H₂₀N₄O₄, show two different substituents at the imidazole N atoms, viz. an allyl group and a [3-(pyridin-4-yl)-4,5-di­hydro­isoxazol-5-yl]methyl group. The fused-ring system is approximately planar [r.m.s. deviation = 0.232 (2) Å], but is slightly buckled along the common edge of the two pairs of adjacent rings, with a dihedral angle between them of 11.17 (6)°. The isoxazole ring makes dihedral angles of 27.2 (2) and 12.7 (2)° with the imidazole and pyridine rings, respectively. Weak C—H⋯O and C—H⋯N hydrogen bonds ensure the cohesion of the crystal structure, forming a three-dimensional network.

N-Cadherin- and L1-functionalised conducting polymers for synergistic stimulation and guidance of neural cell growth

Conducting polymers are promising materials for advanced neuroprostheses and neural repair devices. However, these challenging technologies demand stable presentation of multiple biomolecules on the polymer surface and fabrication of scaffolds suitable for implantation. We electrosynthesised poly(3,4-ethylenedioxythiophene) doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)] (PEDOT:PSS-co-MA) on gold-coated surfaces or carbon microfibres, functionalised the polymer by covalent immobilisation of anti-IgG antibodies and subsequent binding of N-Cadherin and L1 recombinant proteins, and used these materials as substrates for culturing cerebral cortex neurons. N-Cadherin and L1 were much more effective than polylysine in promoting axonal elongation and collateralisation on the polymer. However, N-Cadherin also induced cell migration and dendritic extension and branching, whereas L1 inhibited dendrites. Dual functionalisation with N-Cadherin and L1 produced synergistic effects on neuronal growth that could not be achieved with either of the proteins when used alone. PEDOT:PSS-co-MA electrosynthesised on carbon microfibres showed good electrochemical properties and, when biofunctionalised with N-Cadherin or L1, stimulated very long and guided axonal elongation. Finally, electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry showed that the good electrical properties of PEDOT:PSS-co-MA were not degraded by covalent peptide attachment, indicating that this polymer is suitable for multiple biofunctionalisation of electroactive surfaces in neuroprosthetic and lesion-bridging applications.