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A nanohybrid consisting of poly(3-aminobenzenesulfonic acid-co-aniline) and multiwalled carbon nanotubes [MWCNT-P(ABS-A)]) on a gold electrode was used to immobilize the hexameric tyrosine-coordinated heme protein (HTHP). The enzyme showed direct electron transfer between the heme group of the protein and the nanostructured surface. Desorption of the noncovalently bound heme from the protein could be excluded by control measurements with adsorbed hemin on aminohexanthiol-modified electrodes. The nanostructuring and the optimised charge characteristics resulted in a higher protein coverage as compared with MUA/MU modified electrodes. The adsorbed enzyme shows catalytic activity for the cathodic H2O2 reduction and oxidation of NADH.
Phasins are amphiphilic proteins located at the polymer-cytoplasm interface of bacterial polyhydroxyalkanoates (PHA). The immobilization of phasins on biomaterial surfaces is a promising way to enhance the hydrophilicity and supply cell- directing elements in bioinstructing processes. Optimizing the physical adsorption of phasins requires deep insights into molecular processes during polymer-protein interactions to preserve their structural conformation while optimizing surface coverage. Here, the assembly, organization, and stability of phasin PhaF from Pseudomonas putida at interfaces is disclosed. The Langmuir technique, combined with in situ microscopy and spectroscopic methods, revealed that PhaF forms stable and robust monolayers at different temperatures, with an almost flat orientation of its alpha-helix at the air-water interface. PhaF adsorption onto preformed monolayers of poly[(3-R-hydroxyoctanoate)-co-(3-R-hydroxyhexanoate)] (PHOHHx), yields stable mixed layers below pi = similar to 15.7 mN/m. Further insertion induces a molecular reorganization. PHOHHx with strong surface hydrophobicity is a more adequate substrate for PhaF adsorption than the less hydrophobic poly[(rac-lactide)-co-glycolide] (PLGA). The observed orientation of the main axis of the protein in relation to copolyester interfaces ensures the best exposure of the hydrophobic residues, providing a suitable coating strategy for polymer functionalization.
The electropolymerization of 3,4-(2,2-dibutylpropylenedioxy)thiophene (ProDOT-Bu-2) onto single carbon fiber microelectrode (SCFME) was conducted in acetonitrile (ACN) containing sodium perchlorate (NaClO4) as electrolyte and investigated by cyclic voltammetry (CV). The nanostructured films of poly[3,4-(2,2-dibutyl-propyleneclioxy)thiophene] (PProDOT-Bu-2) which were depositing showed complete reversible redox behavior in monomer-free electrolyte solution.
The capacitive behavior of the films was investigated by electrochemical impedance spectroscopy (EIS) at applied potentials from 0.1 V to 1.3 V. The analysis by equivalent circuit modeling revealed an applied potential around 0.4V to be most suitable for the system PProDOT-Bu-2/SCFME as a double layer supercapacitor component inducing a double layer capacitance C-d, value of 62 mFcm(-2).