Ultrathin films of poly[N-(2-cyanoethyl)pyrrole] and poly(N-methylpyrrole) and their composites with Au nanoparticles were used for the electrochemical detection of small concentrations (10 mM-100 μM) of dopamine, a neurotransmitter related with neurological disorders. Results indicated that Au nanoparticles improve the sensing abilities of the two polymers, even though they are not essential to obtain effective and fast responses toward the presence of dopamine. Furthermore, although both polymers have been found to be highly sensitive to low concentrations of dopamine, the response of poly[N-(2-cyanoethyl)pyrrole] is better and more effective than the response of poly(N-methylpyrrole). Experimental results were corroborated with quantum mechanical calculations on model systems, which also indicated that the interaction of oxidized dopamine with poly[N-(2-cyanoethyl)pyrrole] is stronger than that with poly(N-methylpyrrole). This behavior has been attributed to two different factors: (i) the flexibility of the cyanoethyl groups, which allows maximize the number of attractive van der Waals interactions, and (ii) the dipole of the cyano group, which interacts favorably with the dipole of the CO bonds of oxidized dopamine. Finally, theoretical results were used to propose an atomistic model that explains the interaction behavior between the oxidized dopamine and the conducting polymers.

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Biocomposites formed by a pentapeptide (CREKA), which recognizes clotted plasma proteins, entrapped into the poly(3,4-ethylenedioxythiophene) (PEDOT) matrix have been prepared using three very different procedures. X-ray photoelectron spectroscopy analyses indicate that PEDOT-CREKA films, prepared by chronoamperometry in basic aqueous solution (pH = 10.3) and deposited onto a PEDOT internal layer, present the higher concentration of peptide: one CREKA molecule per six polymer repeat units. The surface of this bilayered system shows numerous folds homogeneously distributed, which have been exhaustively characterized by scanning electron microscopy and atomic force microscopy. Indeed, the morphology and topography of such bilayered films is completely different from those of biocomposite-prepared acid aqueous and organic solutions as polymerization media. The impact of the entrapped peptide molecules in the electrochemical properties of the conducting polymer has been found to be practically negligible. In contrast, biocompatibility assays with two different cellular lines indicate that PEDOT-CREKA favors cellular proliferation, which has been attributed to the binding of the peptide to the fibrin molecules from the serum used as a supplement in the culture medium. The latter assumption has been corroborated examining the ability of PEDOT-CREKA to bind fibrin. The latter ability has been also used to explore an alternative strategy based on the treatment of PEDOT-CREKA with fibrin to promote cell attachment and growth. Overall, the results suggest that PEDOT-CREKA is appropriated for multiple biomedical applications combining the electrochemical properties of conducting polymer and the ability of the peptide to recognize and bind proteins.

Flexible and lightweight electrodes are prepared using a two-step process. First, poly(3,4ethylenedioxythiophene) (PEDOT) microparticles are loaded into poly-γ-glutamic acid (γ-PGA) hydrogel matrix, during the reaction of the biopolymer chains with the cross-linker, cystamine. After this, PEDOT particles dispersed inside the hydrogel are used as polymerization nuclei for the chronoamperometric synthesis of poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PHMeDOT) in aqueous solution. After characterization of the resulting electrode composites, electrochemical studies revealed that the capacitive properties drastically depend on the polymerization time used to produce PHMeDOT inside the loaded hydrogel matrix. Specifically, flexible electrodes obtained using a polymerization time of 7 hours exhibit an specific capacitance of 45.40.7 mF/cm 2 from cyclic voltammetry and charge-discharge long-term stability. The applicability of these electrodes in lightweight and flexible energy-harvesting systems useful for energy-autonomous, low-power, disposable electronic devices, has been proved powering a LED bulb.

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