Electrochemical behaviour of human serum albumin–TiO2 nanocrystalline electrodes studied as a function of pH

Scanning with Laser Beam over the TiO2 Nanotubes Covered with Thin Chromium Layers towards the Activation of the Material under the Visible Light

This work presents pulsed UV laser treatment (355 nm, 2 Hz) of TiO₂ nanotubes decorated with chromium oxides. The modification was performed in a system equipped with a beam homogenizer, and during the irradiation, the samples were mounted onto the moving motorized table. In such a system, both precisely selected areas and any large area of the sample can be modified. Photoelectrochemical tests revealed photoresponse of laser-treated samples up to 1.37- and 18-fold under the illumination with ultraviolet-visible and visible light, respectively, in comparison to bare titania. Optimal beam energy fluence regarding sample photoresponse has been established. Scanning electron microscopy images, X-ray diffraction patterns, along with Raman and X-ray photoelectron spectra, suggest that the enhanced photoresponse results from changes solely induced in the layer of chromium oxides. It is believed that the results of the present work will contribute to a wider interest in laser modification of semiconductors exhibiting improved photoelectrochemical activity.

Widening of the electroactivity potential range by composite formation - capacitive properties of TiO2/BiVO4/PEDOT:PSS electrodes in contact with an aqueous electrolyte

Composites based on the titania nanotubes were tested in aqueous electrolyte as a potential electrode material for energy storage devices. The nanotubular morphology of TiO2 was obtained by Ti anodization. TiO2 nanotubes were covered by a thin layer of bismuth vanadate using pulsed laser deposition. The formation of the TiO2/BiVO4 junction leads to enhancement of pseudocapacitance in the cathodic potential range. The third component, the conjugated polymer PEDOT:PSS, was electrodeposited from an electrolyte containing the monomer EDOT and NaPSS as a source of counter ions. Each stage of modification and deposition affected the overall capacitance and allowed for an expansion of the potential range of electroactivity. Multiple charge/discharge cycles were performed to characterize the electrochemical stability of the inorganic-organic hybrid electrode. Capacitance values higher than 10 mF·cm-2 were maintained even after 10000 galvanostatic cycles (i c = i a = 0.5 mA·cm-2).

Electrochemical Characterization of Protein Adsorption onto YNGRT-Au and VLGXE-Au Surfaces

The adsorption of the proteins CD13, mucin and bovine serum albumin on VLGXE-Au and YNGRT-Au interfaces was monitored by electrochemical impedance spectroscopy in the presence of [Fe(CN)₆]^3−/4−. The hydrophobicity of the Au surface was tailored using specific peptides, blocking agents and diluents. The combination of blocking agents (ethanolamine or n-butylamine) and diluents (hexanethiol or 2-mercaptoethanol) was used to prepare various peptide-modified Au surfaces. Protein adsorption onto the peptide-Au surfaces modified with the combination of n-butylamine and hexanethiol produced a dramatic decrease in the charge transfer resistance, R_ct, for all three proteins. In contrast, polar peptide-surfaces induced a minimal change in R_ct for all three proteins. Furthermore, an increase in R_ct was observed with CD13 (an aminopeptidase overexpressed in certain cancers) in comparison to the other proteins when the VLGXE-Au surface was modified with n-butylamine as a blocking agent. The electrochemical data indicated that protein adsorption may be modulated by tailoring the peptide sequence on Au surfaces and that blocking agents and diluents play a key role in promoting or preventing protein adsorption. The peptide-Au platform may also be used for targeting cancer biomarkers with designer peptides.

Thermal aggregation of bovine serum albumin at different pH: comparison with human serum albumin

We report here a study on thermal aggregation of BSA at two different pH values selected to be close to the isoelectric point (pI) of this protein. Our aim is to better understand the several steps and mechanisms accompanying the aggregation process. For this purpose we have performed kinetics of integrated intensity emission of intrinsic and extrinsic dyes, tryptophans and ANS respectively, kinetics of Rayleigh scattering and of turbidity. The results confirm the important role played by conformational changes in the tertiary structure, especially in the exposure of internal hydrophobic regions that promote intermolecular interactions. We also confirm that the absence of electrostatic repulsion favours the disordered non-specific interactions between molecules and consequently affects the aggregation rate. Finally, the comparison between BSA and another relative protein, HSA, allows us to clarify the role of different domains involved in the aggregation process.