An electrochemical quartz crystal impedance system
(EQCIS) was used to investigate depletion layer effects
on equivalent circuit parameters of piezoelectric quartz
crystal resonance in electrochemical processes of CoSO4
aqueous solutions containing 0.4 mol/L ethylenediamine
+ 0.5 mol/L Na2SO4, 0.2 mol/L 1,10-phenanthroline +
0.5 mol/L Na2SO4 and K3Fe(CN)6, or K4Fe(CN)6 aqueous
solutions containing 1.0 mol/L KCl in potential cycling
experiments, respectively. The impedance data were
analyzed according to Martin's model. For the former two
systems, motional resistance R
1, series resonant frequency f
s, and motional inductance L
1 changed reversibly
with potential, and the observed values of ΔR
1, ΔL
1, and
Δf
s roughly satisfied equations reflecting liquid loading
effects, suggesting that changes in these parameters might
be mainly governed by local variations in solution density
and viscosity near the electrode surface. For the latter two
systems, reversible changes in R
1 with potential coincided
well with the simulated results from variations in solution
density and viscosity near the electrode surface; however,
besides reversible changes of ΔL
1 and Δf
s with potential,
rising drifts of f
s and decreasing drifts of L
1 were found
at oxidation potentials. The drifts of f
s and L
1 observed
are believed to result from mass changes of the gold
electrode, and cyanide and chloride corrosion of the gold
electrode at oxidation potentials may play an important
role for the drifting phenomena. It is concluded that
quantitative analyses of ΔR
1, ΔL
1, and Δf
s obtained from
the EQCIS provide the possibility for differentiating the
net depletion layer effect with the change in electrode
mass, and the ΔR
1 response may be well used for
evaluating local changes in liquid loading inside the
depletion layer compared with responses of Δf
s and ΔL
1.
Several in vitro and in vivo experiments have shown that nanostructured materials, which mimic the nanometer topography of the native tissues, improve biocompatible responses, and result in better tissue integration in medical implants. Understanding various aspects of nanotopography is extremely important for better designs of these devices. In this review paper, recent progress in the fabrication, characterization, biological responses, and application of nanostructured materials are discussed. Specifically, materials such as ceramics and polymers used to manufacture nanostructured surfaces are briefly introduced. Techniques for fabrication and characterization of nanostructured materials are also explored. Cellular responses such as morphology, alignment, adhesion, proliferation, and profiles of gene expression of various cell types after their exposure to nanofeatured materials are particularly reviewed. Finally, the paper briefly discusses some application of nanostructured materials including those in biosensor and tissue engineering fields.
The molecular composition of mycobacteria and Gram-negative bacteria cell walls is structurally different. In this work, Raman microspectroscopy was applied to discriminate mycobacteria and Gram-negative bacteria by assessing specific characteristic spectral features. Analysis of Raman spectra indicated that mycobacteria and Gram-negative bacteria exhibit different spectral patterns under our experimental conditions due to their different biochemical components. Fourier transform infrared (FTIR) spectroscopy, as a supplementary vibrational spectroscopy, was also applied to analyze the biochemical composition of the representative bacterial strains. As for co-cultured bacterial mixtures, the distribution of individual cell types was obtained by quantitative analysis of Raman and FTIR spectral images and the spectral contribution from each cell type was distinguished by direct classical least squares analysis. Coupled atomic force microscopy (AFM) and Raman microspectroscopy realized simultaneous measurements of topography and spectral images for the same sampled surface. This work demonstrated the feasibility of utilizing a combined Raman microspectroscopy, FTIR, and AFM techniques to effectively characterize spectroscopic fingerprints from bacterial Gram types and mixtures.
The corrosion behavior and cell adhesion property of nanostructured TiO2 films deposited electrolytically on Ti6Al4V were examined in the present in vitro study. The nanostructured TiO2 film deposition on Ti6Al4V was achieved via peroxoprecursors. SEM micrographs exhibit the formation of amorphous and crystallite TiO2 nanoparticles on Ti6Al4V before and after being annealed at 500 degrees C. Corrosion behavior of TiO2-deposited and uncoated Ti6Al4V was evaluated in freely aerated Hank's solution at 37 degrees C by the measurement and analysis of open-circuit potential variation with time, Tafel plots, and electrochemical impedance spectroscopy. The electrochemical results indicated that nano-TiO2 coated Ti6Al4V showed a better corrosion resistance in simulated biofluid than uncoated Ti6Al4V. Rat bone cells and human aortic smooth muscle cells were grown on these substrates to study the cellular responses in vitro. The SEM images revealed enhanced cell adhesion, cell spreading, and proliferation on nano-TiO2 coated Ti6Al4V compared to those grown on uncoated substrates for both cell lines. These results suggested that nanotopography produced by deposition of nanostructured TiO2 onto Ti alloy surfaces might enhance corrosion resistance, biocompatibility, and cell integration for implants made of Ti alloys.
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