Cleaning of albumin-contaminated Ti and Cr surfaces: an XPS and QCM study

EPS for bacterial anti-adhesive properties investigated on a model metal surface

Understanding Extracellular Polymeric Substances (EPS) interaction on a well-defined chromium surface is of importance especially for biocorrosion processes. Adsorption of EPS extracted from Pseudoalteromonas NCIMB 2021 on Cr surfaces was investigated using in situ quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS). We show that EPS adsorption is an irreversible process. The amount of adsorbed EPS increases with increasing EPS concentration in solution. For low EPS concentration, the surface is only partially covered by EPS, whereas a continuous organic film of around 15 nm is formed at the surface for high EPS concentrations. An in-depth structuration of this organic layer is evidenced with a strong enrichment of proteins in the inner part and of polysaccharides in the outer part. Adhesion of Pseudoalteromonas NCIMB 2021 has been tested on Cr surfaces covered or not by EPS extracted from Pseudoalteromonas NCIMB 2021. EPS conditioning with a 15 nm film inhibits bacterial adhesion on Cr, showing that this organic film has efficient anti-adhesive properties.

Inhibition of chemical interaction of molybdenum and silicon in a Mo/Si multilayer structure by the formation of intermediate compounds

In the present study, the formation of intermediate compounds in the Mo/Si multilayer was realized by the introduction of barrier layers at the interfaces. Their impact on the interdiffusion of Mo and Si was analyzed via X-ray photoelectron spectroscopy. It was established that the insertion of a thin Be barrier layer led to the formation of beryllide MoBe12 at the interface Si-on-Mo, which prevented the formation of molybdenum disilicide and improved the interface. The insertion of the B4C barrier layer led to its complete decomposition with the formation of borides and carbides of molybdenum and silicon (MoBx, SiBx, MoxC and SiCx) at the Si-on-Mo interface. The formation of only MoBx and SiCx was detected at the Mo-on-Si interface. It was important that the insertion of a thin B4C barrier layer did not fully prevent the formation of MoSi2 at both (Si-on-Mo and Mo-on-Si) the interfaces. These facts allowed us to assume that the diffusion barrier function of the B4C interlayer could be caused by the stability of the formed compounds, rather than the stability of the B4C layer itself.

Pyrolysis of a self-supported dodecyl sulfate anion-intercalated Co(OH)2 nanosheet with enlarged amorphous phase content towards enhanced activity for alkaline water oxidation

Highly active electrocatalysts made of earth-abundant elements are vital for efficient and cost-effective energy storage and conversion systems. In this communication, we report the further amorphization of a solvothermally synthesized dodecyl sulfate anion-intercalated cobalt hydroxide nanosheet array on nickel foam (DS-Co(OH)2/NF) via pyrolysis. Owing to the greatly enlarged interlayer distance of the DS-Co(OH)2/NF precursor (2.4 nm), and the more exposed active sites due to the enlarged amorphous phase content, the resulting P-DS-Co(OH)2/NF exhibits boosted activity as a 3D catalyst electrode for alkaline water oxidation. In 1.0 M KOH, an overpotential of only 266 mV is needed to drive a geometrical catalytic current density of 70 mA cm-2, which is 74 and 121 mV lower than the overpotentials for the DS-Co(OH)2/NF precursor and for Co(OH)2 without DS anion intercalation (Co(OH)2/NF), respectively. Impressively, this catalyst also displays superior long-term stability with a high turnover frequency value of 0.055 O2 s-1 at an overpotential of 340 mV.

Effect of the electrochemical characteristics of titanium on the adsorption kinetics of albumin

An electrochemical quartz crystal microbalance (EQCM) was used to examine the electrochemical behaviour of pure titanium in phosphate buffered saline (PBS) and PBS-containing bovine serum albumin (BSA) solutions, and the associated adsorption characteristics of BSA under cathodic and anodic applied potentials. It was found that the electrochemical behaviours of bulk titanium substrate and titanium-coated QCM sensors are slightly different in PBS buffer solution, which is attributed to the difference in their surface roughness. The oxide film formed on the surface of the QCM sensor during potentiostatic tests was found to affect its electrochemical behaviour, while cathodic cleaning is not sufficient to have it removed. Lastly, the excessive amount of electrons on the titanium surface upon application of a cathodic potential could result in the desorption of BSA due to electrostatic repulsion and protein dehydration. In contrast, application of anodic potential charges the titanium surface positively and can facilitate protein adsorption when the surface is not saturated with protein.

An EQCM was used to examine the electrochemical behaviour of pure titanium in PBS and PBS-containing BSA solutions, and the associated adsorption characteristics of BSA under cathodic and anodic applied potentials.

Grafting of architecture controlled poly(styrene sodium sulfonate) onto titanium surfaces using bio-adhesive molecules: Surface characterization and biological properties

This contribution reports on grafting of bioactive polymers such as poly(sodium styrene sulfonate) (polyNaSS) onto titanium (Ti) surfaces. This grafting process uses a modified dopamine as an anchor molecule to link polyNaSS to the Ti surface. The grafting process combines reversible addition-fragmentation chain transfer polymerization, postpolymerization modification, and thiol-ene chemistry. The first step in the process is to synthetize architecture controlled polyNaSS with a thiol end group. The second step is the adhesion of the dopamine acrylamide (DA) anchor onto the Ti surfaces. The last step is grafting polyNaSS to the DA-modified Ti surfaces. The modified dopamine anchor group with its bioadhesive properties is essential to link bioactive polymers to the Ti surface. The polymers are characterized by conventional methods (nuclear magnetic resonance, size exclusion chromatography, and attenuated total reflection-Fourier-transformed infrared), and the grafting is characterized by x-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and quartz crystal microbalance with dissipation monitoring. To illustrate the biocompatibility of the grafted Ti-DA-polyNaSS surfaces, their interactions with proteins (albumin and fibronectin) and cells are investigated. Both albumin and fibronectin are readily adsorbed onto Ti-DA-polyNaSS surfaces. The biocompatibility of modified Ti-DA-polyNaSS and control ungrafted Ti surfaces is tested using human bone cells (Saos-2) in cell culture for cell adhesion, proliferation, differentiation, and mineralization. This study presents a new, simple way to graft bioactive polymers onto Ti surfaces using a catechol intermediary with the aim of demonstrating the biocompatibility of these size controlled polyNaSS grafted surfaces.

Reusable hydroxyapatite nanocrystal sensors for protein adsorption

The repeatability of the adsorption and removal of fibrinogen and fetal bovine serum on hydroxyapatite (HAp) nanocrystal sensors was investigated by Fourier transform infrared (FTIR) spectroscopy and quartz crystal microbalance with dissipation (QCM-D) monitoring technique. The HAp nanocrystals were coated on a gold-coated quartz sensor by electrophoretic deposition. Proteins adsorbed on the HAp sensors were removed by (i) ammonia/hydrogen peroxide mixture (APM), (ii) ultraviolet light (UV), (iii) UV/APM, (iv) APM/UV and (v) sodium dodecyl sulfate (SDS) treatments. FTIR spectra of the reused surfaces revealed that the APM and SDS treatments left peptide fragments or the proteins adsorbed on the surfaces, whereas the other methods successfully removed the proteins. The QCM-D measurements indicated that in the removal treatments, fibrinogen was slowly adsorbed in the first cycle because of the change in surface wettability revealed by contact angle measurements. The SDS treatment was not effective in removing proteins. The APM or UV treatment decreased the frequency shifts for the reused HAp sensors. The UV/APM treatment did not induce the frequency shifts but decreased the dissipation shifts. Therefore, we conclude that the APM/UV treatment is the most useful method for reproducing protein adsorption behavior on HAp sensors.