Composition and Stability of Plasma Polymer Films Exhibiting Vertical Chemical Gradients

Controlling the balance between stability and functional group density in grown plasma polymer films is the key to diverse applications such as drug release, tissue-engineered implants, filtration, contact lenses, microfluidics, electrodes, sensors, etc. Highly functional plasma polymer films typically show a limited stability in air or aqueous environments due to mechanisms like molecular reorganization, oxidation, and hydrolysis. Stabilization is achieved by enhancing cross-linking at the cost of the terminal functional groups such as −OH and −COOH, but also −NH₂, etc. To overcome such limitations, a structural and chemical gradient was introduced perpendicular to the surface plane; this vertical gradient structure is composed of a highly cross-linked base layer, gradually changing into a more functional nanoscaled surface termination layer. This was achieved using CO₂/C₂H₄ discharges with decreasing power input and increasing gas ratio during plasma polymer deposition. The aging behavior and stability of such oxygen-functional vertical gradient nanostructures were studied in air and in different aqueous environments (acidic pH 4, neutral pH ≈ 6.2, and basic pH 10). Complementary characterization methods were used, including angle-resolved X-ray photoelectron spectroscopy (ARXPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) as well as water contact angle (WCA) measurements. It was found that in air, the vertical gradient films are stabilized over a period of months. The same gradients also appear to be stable in neutral water over a period of at least 1 week. Changes in the oxygen depth profiles have been observed at pH 4 and pH 10 showing structural and chemical aging effects on different time scales. The use of vertical gradient plasma polymer nanofilms thus represents a novel approach providing enhanced stability, thus opening the possibility for new applications

Ultrathin, Flexible, and Transparent Polymer Multilayer Composites for the Protection of Silver Surfaces

Silver coatings at the nanoscale became of high interest for the integration of electronic functionalities on all kinds of objects for daily use. In these thin coatings, corrosion is a big problem as it destroys these thin layers and leads to a loss of conductivity due to missing bulk material. For protection of thin silver coatings against H₂S induced corrosion, we developed nanocoatings based on the covalent layer-by-layer technique. We prepared composites by subsequent deposition of polyamines like polyethylenimine (PEI) or polyallylamine (PAAm) and polyanhydrides like poly­(maleic anhydride-<i>alt-</i>methyl vinyl ether) (Gantrez) or poly­(styrene-<i>co</i>-maleic anhydride) (PSMA). For the tuning of the hydrophobicity, the layers were terminated by reaction with palmitoylic acid derivatives. Reflectivity measurements, contact angle measurements, and AFM measurements were made to investigate how the coatings affect the surface properties. All coatings show a lower reflectivity below 450 nm compared to pure silver, depending on the number of layers deposited. The addition of a palmitoylic derivative to the surface increases the hydrophobicity, but only in case of the Gantrez-PVAm-composite, this approach leads to real hydrophobicity, reaching contact angles above 90°. AFM measurements show a decrease of the roughness of the polymer coated surfaces compared to the pure metal surfaces. Corrosion tests in a H₂S atmosphere show a good protective effect of the palmitoyl-terminated composites. Martindale abrasion tests on coated textiles reveal a good stability of the prepared polymer composites

Data_Sheet_1_Extraction of Biofilms From Ureteral Stents for Quantification and Cultivation-Dependent and -Independent Analyses.pdf

<p>Ureteral stenting is a common surgical procedure, which is associated with a high morbidity and economic burden, but the knowledge on the link between biofilms on these stents, morbidity, and the impact of the involved microbiota is still limited. This is partially due to a lack of methods that allow for a controlled extraction of the biofilms from stents. Development of an appropriate in vitro model to assess prevention of biofilm formation by antimicrobial coatings and biomaterials requires a profound understanding of the biofilm composition, including the involved microbiota. This work describes an analytical pipeline for the extraction of native biofilms from ureteral stents for both cultivation-dependent and -independent analysis, involving a novel mechanical abrasion method of passing stent samples through a tapered pinhole. The efficiency of this novel method was evaluated by quantifying the removed biofilm mass, numbers of cultivable bacteria, calcium content, and microscopic stent analysis after biofilm removal using 30 clinical stent samples. Furthermore, the extraction of in vitro formed Escherichia coli biofilms was evaluated by universal 16S quantitative PCR, a cultivation-independent method to demonstrate efficient biofilm removal by the new approach. The novel method enables effective contamination-free extraction of the biofilms formed on ureteral stents and their subsequent quantification, and it represents a useful tool for comprehensive examinations of biofilms on ureteral stents.</p

Affinity-Driven Immobilization of Proteins to Hematite Nanoparticles

Functional nanoparticles are valuable materials for energy production, bioelectronics, and diagnostic devices. The combination of biomolecules with nanosized material produces a new hybrid material with properties that can exceed the ones of the single components. Hematite is a widely available material that has found application in various sectors such as in sensing and solar energy production. We report a single-step immobilization process based on affinity and achieved by genetically engineering the protein of interest to carry a hematite-binding peptide. Fabricated hematite nanoparticles were then investigated for the immobilization of the two biomolecules C-phycocyanin (CPC) and laccase from <i>Bacillus pumilus</i> (LACC) under mild conditions. Genetic engineering of biomolecules with a hematite-affinity peptide led to a higher extent of protein immobilization and enhanced the catalytic activity of the enzyme

Decaborane Thiols as Building Blocks for Self-Assembled Monolayers on Metal Surfaces

Three <i>nido</i>-decaborane thiol cluster compounds, [1-(HS)-<i>nido</i>-B₁₀H₁₃] <b>1</b>, [2-(HS)-<i>nido</i>-B₁₀H₁₃] <b>2</b>, and [1,2-(HS)₂<i>-nido</i>-B₁₀H₁₂] <b>3</b> have been characterized using NMR spectroscopy, single-crystal X-ray diffraction analysis, and quantum-chemical calculations. In the solid state, <b>1</b>, <b>2</b>, and <b>3</b> feature weak intermolecular hydrogen bonding between the sulfur atom and the relatively positive bridging hydrogen atoms on the open face of an adjacent cluster. Density functional theory (DFT) calculations show that the value of the interaction energy is approximately proportional to the number of hydrogen atoms involved in the interaction and that these values are consistent with a related bridging-hydrogen atom interaction calculated for a B₁₈H₂₂·C₆H₆ solvate. Self-assembled monolayers (SAMs) of <b>1</b>, <b>2</b>, and <b>3</b> on gold and silver surfaces have been prepared and characterized using X-ray photoelectron spectroscopy. The variations in the measured sulfur binding energies, as thiolates on the surface, correlate with the (CC2) calculated atomic charge for the relevant boron vertices and for the associated sulfur substituents for the parent B₁₀H₁₃(SH) compounds. The calculated charges also correlate with the measured and DFT-calculated thiol ¹H chemical shifts. Wetting-angle measurements indicate that the hydrophilic open face of the cluster is directed upward from the substrate surface, allowing the bridging hydrogen atoms to exhibit a similar reactivity to that of the bulk compound. Thus, [PtMe₂(PMe₂Ph)₂] reacts with the exposed and acidic B–H–B bridging hydrogen atoms of a SAM of <b>1</b> on a gold substrate, affording the addition of the metal moiety to the cluster. The XPS-derived stoichiometry is very similar to that for a SAM produced directly from the adsorption of [1-(HS)-7,7-(PMe₂Ph)₂-<i>nido</i>-7-PtB₁₀H₁₁] <b>4</b>. The use of reactive boron hydride SAMs as templates on which further chemistry may be carried out is unprecedented, and the principle may be extended to other binary boron hydride clusters