Vacuum-Ultraviolet Photopolymerisation of Amine-Rich Thin Films

VUV Photodeposition of Thiol-Terminated Films: A Wavelength-Dependent Study

Photoinitiated chemical vapor deposition (PICVD) has become attractive for selective and specific surface functionalization, because it relies on a single energy source, the photons, to carry out (photo-) chemistry. In the present wavelength (λ)-dependent study, thiol (SH)-terminated thin film deposits have been prepared from gas mixtures of acetylene (C₂H₂) and hydrogen sulfide (H₂S) via PICVD using four different vacuum-ultraviolet (VUV) sources, namely, KrL (λ_peak = 123.6 nm), XeL (λ_peak = 147.0 nm), XeE (λ_peak = 172.0 nm), and Hg (λ = 184.9 nm) lamps. Different λ influence the deposition kinetics and film composition, reflecting that photolytic reactions are governed by the gases' absorption coefficients, k(λ). Thiol concentrations, [SH], up to ∼7.7%, were obtained with the XeL source, the highest reported in the literature so far. Furthermore, all films showed islandlike surface morphology, regardless of λ.

Kinetics, Chemistry, and Morphology of Syngas Photoinitiated Chemical Vapor Deposition

Syngas is the product of gasification processes and is used for the production of petrochemicals. Little attention has been paid to its use in the production of oligomeric thin films under ambient conditions. Herein, the nature of the photoinitiated chemical vapor deposition of films made from syngas using high-wavelength ultraviolet light is discussed, including an exploration of the oligomeric films' structure, synthesis mechanism, and growth kinetics. Specifically, X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analyses provide insight into the chemical structure, illustrating the effect of photogenerated radicals in the formation of aliphatic, anhydride, and cyclic structures. The films are covalently bonded to the substrate and chemically uniform. Electron and atomic force microscopy identify an islandlike morphology for the deposit. These insights into the mechanism and structure are linked to processing parameters through a study on the effect of residence time and treatment duration on the deposition rate, as determined through profilometry.

Double protein functionalized poly-ε-caprolactone surfaces: in depth ToF-SIMS and XPS characterization

In biomaterial research, great attention has focussed on the immobilization of biomolecules with the aim to increase cell-adhesive properties of materials. Many different strategies can be applied. In previously published work, our group focussed on the treatment of poly-ε-caprolactone (PCL) films by an Ar-plasma, followed by the grafting of 2-aminoethyl methacrylate (AEMA) under UV-irradiation. The functional groups introduced, enabled the subsequent covalent immobilisation of gelatin. The obtained coating was finally applied for the physisorption of fibronectin. The successful PCL surface functionalization was preliminary confirmed using XPS, wettability studies, AFM and SEM. In the present article, we report on an in-depth characterization of the materials developed using ToF-SIMS and XPS analysis. The homogeneous AEMA grafting and the subsequent protein coating steps could be confirmed by both XPS and ToF-SIMS. Using ToF-SIMS, it was possible to demonstrate the presence of polymethacrylates on the surface. From peak deconvoluted XPS results (C- and N-peak), the presence of proteins could be confirmed. Using ToF-SIMS, different positive ions, correlating to specific amino-acids could be identified. Importantly, the gelatin and the fibronectin coatings could be qualitatively distinguished. Interestingly for biomedical applications, ethylene oxide sterilization did not affect the surface chemical composition. This research clearly demonstrates the complementarities of XPS and ToF-SIMS in biomedical surface modification research.

Biofilm formation by the yeast Rhodotorula mucilaginosa: process, repeatability and cell attachment in a continuous biofilm reactor

Yeast biofilms contribute to quality impairment of industrial processes and also play an important role in clinical infections. Little is known about biofilm formation and their treatment. The aim of this study was to establish a multi-layer yeast biofilm model using a modified 3.7 l bench-top bioreactor operated in continuous mode (D = 0.12 h(-1)). The repeatability of biofilm formation was tested by comparing five bioprocesses with Rhodotorula mucilaginosa, a strain isolated from washing machines. The amount of biofilm formed after 6 days post inoculation was 83 μg cm(-2) protein, 197 μg cm(-2) polysaccharide and 6.9 × 10(6) CFU cm(-2) on smooth polypropylene surfaces. Roughening the surface doubled the amount of biofilm but also increased its spatial variability. Plasma modification of polypropylene significantly reduced the hydrophobicity but did not enhance cell attachment. The biofilm formed on polypropylene coupons could be used for sanitation studies.

Effect of nitrogen-rich cell culture surfaces on type X collagen expression by bovine growth plate chondrocytes

BACKGROUND

Recent evidence indicates that osteoarthritis (OA) may be a systemic disease since mesenchymal stem cells (MSCs) from OA patients express type X collagen, a marker of late stage chondrocyte hypertrophy (associated with endochondral ossification). We recently showed that the expression of type X collagen was suppressed when MSCs from OA patients were cultured on nitrogen (N)-rich plasma polymer layers, which we call "PPE:N" (N-doped plasma-polymerized ethylene, containing up to 36 atomic percentage (at.% ) of N.

METHODS

In the present study, we examined the expression of type X collagen in fetal bovine growth plate chondrocytes (containing hypertrophic chondrocytes) cultured on PPE:N. We also studied the effect of PPE:N on the expression of matrix molecules such as type II collagen and aggrecan, as well as on proteases (matrix metalloproteinase-13 (MMP-13) and molecules implicated in cell division (cyclin B2). Two other culture surfaces, "hydrophilic" polystyrene (PS, regular culture dishes) and nitrogen-containing cation polystyrene (Primaria®), were also investigated for comparison.

RESULTS

Results showed that type X collagen mRNA levels were suppressed when cultured for 4 days on PPE:N, suggesting that type X collagen is regulated similarly in hypertrophic chondrocytes and in human MSCs from OA patients. However, the levels of type X collagen mRNA almost returned to control value after 20 days in culture on these surfaces. Culture on the various surfaces had no significant effects on type II collagen, aggrecan, MMP-13, and cyclin B2 mRNA levels.

CONCLUSION

Hypertrophy is diminished by culturing growth plate chondrocytes on nitrogen-rich surfaces, a mechanism that is beneficial for MSC chondrogenesis. Furthermore, one major advantage of such "intelligent surfaces" over recombinant growth factors for tissue engineering and cartilage repair is potentially large cost-saving.