Plasma Polymerized Allylamine Research Articles

Plasma polymerized bio-interface directs fibronectin adsorption and functionalization to enhance “epithelial barrier structure” formation via FN-ITG β1-FAK-mTOR signaling cascade

BackgroundTransepithelial medical devices are increasing utilized in clinical practices. However, the damage of continuous natural epithelial barrier has become a major risk factor for the failure of epithelium-penetrating implants. How to increase the “epithelial barrier structures” (focal adhesions, hemidesmosomes, etc.) becomes one key research aim in overcoming this difficulty. Directly targeting the in situ “epithelial barrier structures” related proteins (such as fibronectin) absorption and functionalization can be a promising way to enhance interface-epithelial integration.MethodsHerein, we fabricated three plasma polymerized bio-interfaces possessing controllable surface chemistry. Their capacity to adsorb and functionalize fibronectin (FN) from serum protein was compared by Liquid Chromatography-Tandem Mass Spectrometry. The underlying mechanisms were revealed by molecular dynamics simulation. The response of gingival epithelial cells regarding the formation of epithelial barrier structures was tested.ResultsPlasma polymerized surfaces successfully directed distinguished protein adsorption profiles from serum protein pool, in which plasma polymerized allylamine (ppAA) surface favored adsorbing adhesion related proteins and could promote FN absorption and functionalization via electrostatic interactions and hydrogen bonds, thus subsequently activating the ITG β1-FAK-mTOR signaling and promoting gingival epithelial cells adhesion.ConclusionThis study offers an effective perspective to overcome the current dilemma of the inferior interface-epithelial integration by in situ protein absorption and functionalization, which may advance the development of functional transepithelial biointerfaces.Graphical Tuning the surface chemistry by plasma polymerization can control the adsorption of fibronectin and functionalize it by exposing functional protein domains. The functionalized fibronectin can bind to human gingival epithelial cell membrane integrins to activate epithelial barrier structure related signaling pathway, which eventually enhances the formation of epithelial barrier structure.

Chemical characterization of plasma polymerized allylamine coatings with addition of ammonia and oxygen by XPS

Article Chemical characterization of plasma polymerized allylamine coatings with addition of ammonia and oxygen by XPS was published on August 1, 2022 in the journal Current Directions in Biomedical Engineering (volume 8, issue 2).

Amine Plasma-Polymerization of 3D Polycaprolactone/β-Tricalcium Phosphate Scaffold to Improving Osteogenic Differentiation In Vitro.

This study aims to investigate the surface characterization and pre-osteoblast biological behaviors on the three-dimensional (3D) poly(ε-caprolactone)/β-tricalcium phosphate (β-TCP) scaffold modified by amine plasma-polymerization. The 3D PCL scaffolds were fabricated using fused deposition modeling (FDM) 3D printing. To improve the pre-osteoblast bioactivity, the 3D PCL scaffold was modified by adding β-TCP nanoparticles, and then scaffold surfaces were modified by amine plasma-polymerization using monomer allylamine (AA) and 1,2-diaminocyclohexane (DACH). After the plasma-polymerization of PCL/β-TCP, surface characterizations such as contact angle, AFM, XRD, and FTIR were evaluated. In addition, mechanical strength was measured by UTM. The pre-osteoblast bioactivities were evaluated by focal adhesion and cell proliferation. Osteogenic differentiation was investigated by ALP activity, Alizarin red staining, and Western blot. Plasma-polymerization induced the increase in hydrophilicity of the surface of the 3D PCL/β-TCP scaffold due to the deposition of amine polymeric thin film on the scaffold surface. Focal adhesion and proliferation of pre-osteoblast improved, and osteogenic differentiation was increased. These results indicated that 3D PCL/β-TCP scaffolds treated with DACH plasma-polymerization showed the highest bioactivity compared to the other samples. We suggest that 3D PCL/β-TCP scaffolds treated with DACH and AA plasma-polymerization can be used as a promising candidate for osteoblast differentiation of pre-osteoblast.

Automatic Actin Filament Quantification and Cell Shape Modeling of Osteoblasts on Charged Ti Surfaces

Surface charges at the cell–biomaterial interface are known to determine cellular functions. Previous findings on cell signaling indicate that osteoblastic cells favor certain moderately positive surface charges, whereas highly positive charges are not tolerated. In this study, we aimed to gain deeper insights into the influence exerted by surface charges on the actin cytoskeleton and the cell shape. We analyzed surfaces with a negative, moderately positive, and highly positive zeta (ζ) potential: titanium (Ti), Ti with plasma polymerized allylamine (PPAAm), and Ti with a polydiallyldimethylammonium chloride (PDADMA) multilayer, respectively. We used the software FilaQuant for automatic actin filament quantification of osteoblastic MG-63s, analyzed the cell edge height with scanning ion conductance microscopy (SICM), and described the cellular shape via a mathematical vertex model. A significant enhancement of actin filament formation was achieved on moderately positive (+7 mV) compared with negative ζ-potentials (−87 mV). A hampered cell spreading was reflected in a diminished actin filament number and length on highly positively charged surfaces (+50 mV). Mathematical simulations suggested that in these cells, cortical tension forces dominate the cell–substrate adhesion forces. Our findings present new insights into the impact of surface charges on the overall cell shape and even intracellular structures.

A surface dielectric barrier discharge for deposition of allylamine polymer costings

In this article, an atmospheric pressure surface dielectric barrier discharge (SDBD) generated in helium has been studied for its discharge characteristics and its ability to generate amine functionalised polymer coatings for application in cell therapy. The electrical and optical properties of the surface plasma generated SDBD consisting of a mesh electrode are presented. Current-voltage measurements and intensified charge coupled device (ICCD) camera images showed that the plasma device is able to generate glow like discharge structures that are stable over the area of the electrodes at applied voltages ranging from 3.5 kV to 5 kVpk-pk. Most importantly, the plasma images show evidence of high electric fields around the hexagonal grid of the mesh electrode. Through the helium line ratio method, the density and temperature of electrons in the discharge was estimated between 1011–1012 cm3 and 0.3–0.8 eV respectively as a function of gas flow.Surface characterisation of the allylamine plasma polymer coating (ppAAm) with X‐ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that the coating is rich in amine functionality. However, atomic force microscopy (AFM) analysis show that the thickness of the coating is spatially nonuniform. From the results, it is predicted that the high amine functionality of the coating could be applied in cell adhesion and growth.

Phenolic-amine chemistry mediated synergistic modification with polyphenols and thrombin inhibitor for combating the thrombosis and inflammation of cardiovascular stents

Antithrombogenicity, anti-inflammation, and rapid re-endothelialization are central requirements for the long-term success of cardiovascular stents. In this work, a plant-inspired phenolic-amine chemistry strategy was developed to combine the biological functions of a plant polyphenol, tannic acid (TA), and the thrombin inhibitor bivalirudin (BVLD) for tailoring the desired multiple surface functionalities of cardiovascular stents. To realize the synergistic modification of TA and BVLD on a stent surface, an amine-bearing coating of plasma polymerized allylamine was firstly prepared on the stent surface, followed by the sequential conjugation of TA and BVLD in alkaline solution based on phenolic-amine chemistry (i.e., Michael addition reaction). TA and BVLD were successfully immobilized onto the stent surface with considerable amounts of 330 ± 12 and 930 ± 80 ng/cm2, respectively. The abundant phenolic hydroxyl groups of TA imparted the stent with ability to suppress inflammation. Meanwhile, BVLD provided an antithrombogenic and endothelial-friendly microenvironment. As a result, the combined functions of the TA and BVLD facilitate the rapid stent re-endothelialization for reduced intimal hyperplasia in vivo, and may be a promising strategy to address the clinical complications associated with restenosis and late stent thrombosis.

Efficacy of Plasma-Polymerized Allylamine Coating of Zirconia after Five Years.

Plasma-polymerized allylamine (PPAAm) coatings of titanium enhance the cell behavior of osteoblasts. The purpose of the present study was to evaluate a PPAAm nanolayer on zirconia after a storage period of 5 years. Zirconia specimens were directly coated with PPAAm (ZA0) or stored in aseptic packages at room temperature for 5 years (ZA5). Uncoated zirconia specimens (Zmt) and the micro-structured endosseous surface of a zirconia implant (Z14) served as controls. The elemental compositions of the PPAAm coatings were characterized and the viability, spreading and gene expression of human osteoblastic cells (MG-63) were assessed. The presence of amino groups in the PPAAm layer was significantly decreased after 5 years due to oxidation processes. Cell viability after 24 h was significantly higher on uncoated specimens (Zmt) than on all other surfaces. Cell spreading after 20 min was significantly higher for Zmt = ZA0 > ZA5 > Z14, while, after 24 h, spreading also varied significantly between Zmt > ZA0 > ZA5 > Z14. The expression of the mRNA differentiation markers collagen I and osteocalcin was upregulated on untreated surfaces Z14 and Zmt when compared to the PPAAm specimens. Due to the high biocompatibility of zirconia itself, a PPAAm coating may not additionally improve cell behavior.

Comparative study of different nitrogen-containing plasma modifications applied on 3D porous PCL scaffolds and 2D PCL films

Additive manufacturing of 3D-scaffolds and surface modification of 2D-substrates using nitrogen-containing plasmas have separately advanced the tissue engineering field for their cyto-responsive topographical and chemical features. However, their synergistic implementation remains largely unsuccessful because of the non-homogeneous surface treatment throughout porous structures. Therefore, this study focuses on the 3D-printing of polycaprolactone (PCL) scaffolds and the optimization of their surface chemistry via 3 plasma modifications: N2 activation, NH3:He (1:9) activation and allylamine polymerization. For an adequate optimization, a precise surface chemical analysis is performed throughout scaffold cross-sections by local measurements using an X-ray photoelectron spectroscopy (XPS) machine connected to a secondary electron image camera. Overall higher nitrogen incorporation and amino-selectivity are detected after NH3 (5.0%) compared to N2 plasma activation (2.8%). A remarkably high average nitrogen content (12.4%) primarily incorporated as C-N bonds is perceived on plasma polymerized allylamine coatings that exhibit an excellent uniformity throughout the scaffolds. In fact, high energy densities lead to a deposition of coatings with a symmetrical shallow nitrogen gradient towards the scaffold inner struts that still present a much higher nitrogen content (7%) when comparing with the state-of-the-art. Overall, this study constitutes a perfect-picture reference for plasma treatment of porous scaffolds.

From surface to bulk modification: Plasma polymerization of amine-bearing coating by synergic strategy of biomolecule grafting and nitric oxide loading

Integration of two or more biomolecules with synergetic and complementary effects on a material surface can help to obtain multi-functions for various biomedical applications. However, the amounts of biomolecules integrated and their physiological functions are compromised due to the limited surface anchoring sites. Herein, we propose a novel concept of film engineering strategy “from surface to bulk synergetic modification”. This new concept is realized by employing the surface amine groups of plasma polymerized allylamine (PPAm) film for grafting a molecule e.g., thrombin inhibitor, bivalirudin (BVLD), meanwhile its bulk amine groups is used as a universal depot for storing and releasing therapeutic nitric oxide (NO) gas as supplement to the functions of BVLD. It is demonstrated that such a “from surface to bulk synergetic modification” film engineering can impart the modified-substrates with anti-platelet and anti-coagulant dual functions, giving rise to a highly endothelium-mimetic thromboresistant property. We believe that our research provides a very promising strategy to deliver multifunctional surface versatilely that require NO release in combination with other properties, which will find broad biomedical applications in blood-contacting devices, and et al. Moreover, it also provides a brand-new film engineering strategy for tailoring surface multi-functionalities of a wide range of materials.

Plasma Polymerized Allylamine-The Unique Cell-Attractive Nanolayer for Dental Implant Materials.

Biomaterials should be bioactive in stimulating the surrounding tissue to accelerate the ingrowth of permanent implants. Chemical and topographical features of the biomaterial surface affect cell physiology at the interface. A frequently asked question is whether the chemistry or the topography dominates the cell-material interaction. Recently, we demonstrated that a plasma-chemical modification using allylamine as a precursor was able to boost not only cell attachment and cell migration, but also intracellular signaling in vital cells. This microwave plasma process generated a homogenous nanolayer with randomly distributed, positively charged amino groups. In contrast, the surface of the human osteoblast is negatively charged at −15 mV due to its hyaluronan coat. As a consequence, we assumed that positive charges at the material surface—provoking electrostatic interaction forces—are attractive for the first cell encounter. This plasma-chemical nanocoating can be used for several biomaterials in orthopedic and dental implantology like titanium, titanium alloys, calcium phosphate scaffolds, and polylactide fiber meshes produced by electrospinning. In this regard, we wanted to ascertain whether plasma polymerized allylamine (PPAAm) is also suitable for increasing the attractiveness of a ceramic surface for dental implants using Yttria-stabilized tetragonal zirconia.

Tuning of the electrochemical properties of transparent fluorine-doped tin oxide electrodes by microwave pulsed-plasma polymerized allylamine

We report here the dry, one-step, and low-temperature modification of FTO surfaces using pulsed plasma polymerization of allylamine (PPAAm). PPAAm/FTO surfaces were characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and contact angles to understand the morphological, structural, and optical properties. FTO were coated with a very thin layer of adherent cross-linked, pinhole-, and additive-free allylamine plasma polymer resistant to hydrolysis and delamination, and characterized by a high density of positively charged amino groups. Electrochemical studies revealed that PPAAm/FTO electrodes show wide range pH stability and reaction rates tuned by the duration of plasma treatment. We show how the modification of plasma treatment duration between 72 s and 288 s affects the chemical structure and thickness of the obtained modification, having a strong influence on the charge transfer kinetics. In particular, XPS revealed the occurrence of the reduction processes under long-term plasma exposure proving the need for monitoring of this key factor. This covalent immobilization of amine compounds on FTO surface using rapid process in microwave pulsed-plasma makes it a promising electrode for future applications in electrochemical biosensors and optoelectronic devices.

Biomimetic engineering endothelium-like coating on cardiovascular stent through heparin and nitric oxide-generating compound synergistic modification strategy

Co-immobilization of two or more molecules with different and complementary functions to prevent thrombosis, suppress smooth muscle cell (SMC) proliferation, and support endothelial cell (EC) growth is generally considered to be promising for the re-endothelialization on cardiovascular stents. However, integration of molecules with distinct therapeutic effects does not necessarily result in synergistic physiological functions due to the lack of interactions among them, limiting their practical efficacy. Herein, we apply heparin and nitric oxide (NO), two key molecules of the physiological functions of endothelium, to develop an endothelium-mimetic coating. Such coating is achieved by sequential conjugation of heparin and the NO-generating compound selenocystamine (SeCA) on an amine-bearing film of plasma polymerized allylamine. The resulting surface combines the anti-coagulant (anti-FXa) function provided by the heparin and the anti-platelet activity of the catalytically produced NO. It also endows the stents with the ability to simultaneously up-regulate α-smooth muscle actin (α-SMA) expression and to increase cyclic guanylate monophosphate (cGMP) synthesis of SMC, thereby significantly promoting their contractile phenotype and suppressing their proliferation. Importantly, this endothelium-biomimetic coating creates a favorable microenvironment for EC over SMC. These features impressively improve the antithrombogenicity, re-endothelialization and anti-restenosis of vascular stents in vivo.

Understanding the impact of poly(allylamine) plasma grafting on the filtration performances of a commercial polymeric membrane

Commercial membranes often exhibit difficulties in rejecting specific ionic species, and especially multivalent cations, due to their usual negative charge. To face this drawback, it is proposed here to functionalize the membrane surface by allylamine plasma polymerization. The impact of this modification on both permeation flux and ion rejection is investigated for single salt solutions and ion mixtures. It is shown that the membrane behaves like a positive membrane from the point of view of cation rejection but the negative charge (and the corresponding electrical field) inside pores leads to high rejection of divalent anions like a negative membrane. This allows a high selectivity between divalent and monovalent ions irrespective of their sign. However, in the cases of ionic mixtures, the selectivity between cations and anions is reduced as the grafting duration increases. This outstanding impact on performances was obtained although the membrane surface is perhaps partially covered by plasma poly(allylamine). Indeed, the overall apparent zeta-potential was found to be still slightly negative or slightly positive for 5 and 10 min of polymerization, respectively. Consequently, a definitive conclusion about the mechanisms governing the impact of grafting on rejection cannot still be drawn and it requires an in-depth characterization of the membrane before and after modification so as to consider the changes in physicochemical properties induced by poly(allylamine) grafting.

Minimal attachment of Pseudomonas aeruginosa to DNA modified surfaces.

Extracellular deoxyribonucleic acid (eDNA) exists in biological environments such as those around medical implants since prokaryotic or eukaryotic cells can undergo processes such as autolysis, necrosis, and apoptosis. For bacteria, eDNA has been shown to be involved in biofilm formation and gene transfer and acts as a nutrient source. In terms of biofilm formation, eDNA in solution has been shown to be very important in increasing attachment; however, very little is known about the role played by surface immobilized eDNA in initiating bacterial attachment and whether the nature of a DNA layer (physically adsorbed or covalently attached, and molecular weight) influences biofilm formation. In this study, the authors shed light on the role that surface attached DNA plays in the early biofilm formation by using Si wafers (Si) and allylamine plasma polymer (AAMpp) coated Si wafers to adsorb and covalently immobilize salmon sperm DNA of three different molecular weights. Pseudomonas aeruginosa was chosen to study the bacterial interactions with these DNA functionalized surfaces. Characterization of surface chemistry and imaging of attached bacteria were performed via x-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and epi-fluorescence microscopy. XPS results confirmed the successful grafting of DNA on the AAMpp and Si surfaces, and surprisingly the results showed that the surface attached DNA actually reduced initial bacterial attachment, which was contrary to the initial hypothesis. This adds speculation about the specific role played by DNA in the dynamics of how it influences biofilm formation, with the possibility that it could actually be used to make bacterial resistant surfaces.

Ab-initio study of electrical and optical properties of allylamine

The Density functional theory is one of most promising methodology in fast and accurate calculations of electrical and optical properties from the atomic basis. In this paper, we calculate electrical and optical properties of allylamine (2-propen 1- amine) in terms of accuracy and speed of calculations obtained by selection of DFT-1/2 method with ultrasoft Vanderbilt pseudopotentials. Comparison of density of states between molecule and bulk configuration shows great agreement between them, therefore we calculated refractive index which showed even better agreement with experimental data. Full Text: PDF ReferencesW. Kohn and L. J. Sham, 'Self-Consistent Equations Including Exchange and Correlation Effects', Phys. Rev., vol. 140, no. 4A, pp. A1133–A1138, Nov. 1965. CrossRef J. P. Perdew, K. Burke, and M. Ernzerhof, 'Generalized Gradient Approximation Made Simple', Phys. Rev. Lett., vol. 77, no. 18, pp. 3865–3868, Oct. 1996. CrossRef L. G. Ferreira, M. Marques, and L. K. Teles, 'Approximation to density functional theory for the calculation of band gaps of semiconductors', Physical Review B, vol. 78, no. 12, Sep. 2008. CrossRef L. G. Ferreira, M. Marques, and L. K. Teles, 'Slater half-occupation technique revisited: the LDA-1/2 and GGA-1/2 approaches for atomic ionization energies and band gaps in semiconductors', AIP Advances, vol. 1, no. 3, p. 032119, Aug. 2011. CrossRef M. Schlipf and F. Gygi, 'Optimization algorithm for the generation of ONCV pseudopotentials', Computer Physics Communications, vol. 196, pp. 36–44, Nov. 2015. CrossRef P. Prayongpan and C. Michael Greenlief, 'Density functional study of ethylamine and allylamine on Si(100)-2×1 and Ge(100)-2×1 surfaces', Surface Science, vol. 603, no. 7, pp. 1055–1069, Apr. 2009. CrossRef M. T. van Os, B. Menges, R. Foerch, G. J. Vancso, and W. Knoll, 'Characterization of Plasma-Polymerized Allylamine Using Waveguide Mode Spectroscopy', Chemistry of Materials, vol. 11, no. 11, pp. 3252–3257, Nov. 1999. CrossRef J. Zeng, R.-Q. Zhang, and H. Treutlein, Quantum Simulations of Materials and Biological Systems. Springer Science & Business Media, 2012. CrossRef I. Del Villar, I. R. Matias, and F. J. Arregui, 'Enhancement of sensitivity in long-period fiber gratings with deposition of low-refractive-index materials', Optics Letters, vol. 30, no. 18, p. 2363, Sep. 2005. CrossRef D. Nidzworski et al., 'A rapid-response ultrasensitive biosensor for influenza virus detection using antibody modified boron-doped diamond', Sci Rep, vol. 7, Nov. 2017. CrossRef Synopsys QuantumWise, Atomistix Toolkit version 2018.06 .D. C. Liu and J. Nocedal, 'On the limited memory BFGS method for large scale optimization', Mathematical Programming, vol. 45, no. 1–3, pp. 503–528, Aug. 1989. CrossRef K. F. Garrity, J. W. Bennett, K. M. Rabe, and D. Vanderbilt, 'Pseudopotentials for high-throughput DFT calculations', Computational Materials Science, vol. 81, pp. 446–452, Jan. 2014. CrossRef Yu Cai, T. Zhang, A. B. Anderson, J. C. Angus, L. N. Kostadinov, and T. V. Albu, 'The origin of shallow n-type conductivity in boron-doped diamond with H or S co-doping: Density functional theory study', Diamond and Related Materials, vol. 15, no. 11, pp. 1868–1877, Nov. 2006. CrossRef

XPS and IR studies of plasma polymers layer deposited from allylamine with addition of ammonia

The plasma polymerization of allylamine was often investigated to modify polymer surfaces with primary amino groups. However, this deposition process is characterized by a significant loss of NH2 groups originally present in allylamine. To compensate this loss of NH2 groups in the deposited plasma polymer layer ammonia was added to the plasma process. Indeed, huge amount of nitrogen could be incorporated into the plasma polymer using addition of ammonia but the yield in primary amino groups was not increased. Extensive side-reactions were observed.Such NH2 group-enriched polymer surfaces are interesting for bio-applications.The influence of NH3 addition to allylamine on the yield of primary amino groups was characterized using FTIR-ATR, X-ray photoelectron spectroscopy and differential scanning calorimetry.

Young's modulus of plasma‐polymerized allylamine films using micromechanical cantilever sensor and laser‐based surface acoustic wave techniques

Mechanical properties of ultra‐thin organic films are fundamentally important in coating applications. Micromechanical cantilever sensor (MCS) and laser‐based surface acoustic wave (LA‐SAW) techniques were both used to measure Young's moduli (E) of plasma polymerized films at different humidities (H). For plasma polymerized allylamine (ppAA) films deposited at 5 W and 90 W, E of 1400 ± 350 MPa and 110 ± 20 MPa at H between 10 and 40%, and 1070 ± 250 MPa and 32 ± 10 MPa at H between 70 and 80% were measured. The LA‐SAW technique revealed E lower than 60% of that measured by MCS. The difference suggested either an enhanced swelling at the air interface or a gradient of cross‐linking density.

Fibroblast Responses Toward Colloidal Assembles and Plasma Polymer Coating

Colloidal assemblies represent a versatile and cost efficient way to generate surface patterns at micron and sub-micron length scales. Chemical modification of the assemblies can be utilized to study the influence of different surface chemistries on cellular responses with high lateral resolution. In this study, single and binary colloidal assemblies were made using different sizes of particles. An allylamine plasma polymer (ALApp) layer was deposited on the top of the assemblies to provide a uniform surface chemistry. Cellular responses toward unmodified and ALApp-coated assemblies was evaluated using L929 fibroblasts. Cells showed smaller spreading area on both single and binary assemblies compared to flat control. Cell size was dependent on the particle size or combination. This effect can be compensated by different degrees after the ALApp coating. These results will find application in the development of new cell culture coatings through the combined use of colloidal assembles and plasma polymer coatings.

Enhanced calcium ion mobilization in osteoblasts on amino group containing plasma polymer nanolayer

BackgroundBiomaterial modifications—chemical and topographical—are of particular importance for the integration of materials in biosystems. Cells are known to sense these biomaterial characteristics, but it has remained unclear which physiological processes bio modifications trigger. Hence, the question arises of whether the dynamic of intracellular calcium ions is important for the characterization of the cell–material interaction. In our prior research we could demonstrate that a defined geometrical surface topography affects the cell physiology; this was finally detectable in a reduced intracellular calcium mobilization after the addition of adenosine triphosphate (ATP).ResultsThis new contribution examines the cell physiology of human osteoblasts concerning the relative cell viability and the calcium ion dynamic on different chemical modifications of silicon–titanium (Ti) substrates. Chemical modifications comprising the coating of Ti surfaces with a plasma polymerized allylamine (PPAAm)-layer or with a thin layer of collagen type-I were compared with a bare Ti substrate as well as tissue culture plastic. For this purpose, the human osteoblasts (MG-63 and primary osteoblasts) were seeded onto the surfaces for 24 h. The relative cell viability was determined by colorimetric measurements of the cell metabolism and relativized to the density of cells quantified using crystal violet staining. The calcium ion dynamic of osteoblasts was evaluated by the calcium imaging analysis of fluo-3 stained vital cells using a confocal laser scanning microscope. The positively charged nano PPAAm-layer resulted in enhanced intracellular calcium ion mobilization after ATP-stimulus and cell viability. This study underlines the importance of the calcium signaling for the manifestation of the cell physiology.ConclusionsOur current work provides new insights into the intracellular calcium dynamic caused by diverse chemical surface compositions. The calcium ion dynamic appears to be a sensitive parameter for the cell physiology and, thus, may represent a useful approach for evaluating a new biomaterial. In this regard, reliable in vitro-tests of cell behavior at the interface to a material are crucial steps in securing the success of a new biomaterial in medicine.

Controlled Attachment of Pseudomonas aeruginosa with Binary Colloidal Crystal-Based Topographies.

Micro- and nanotopographies can interfere with bacteria attachment, however, the interplay existing between surface chemistry and topography remains unclear. Here, self-assembled spherical micrometer- silica and nanometer poly(methyl methacrylate) (PMMA)-sized particles are used to make binary colloidal crystal (BCC) topographical patterns to study bacterial attachment. A uniform surface chemistry of allylamine plasma polymer (AAMpp) is coated on the top of the BCCs to study only the topography effects. The uncoated and coated BCCs are exposed to Pseudomonas aeruginosa, and the surfaces and bacteria are characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and fluorescence microscopy. It is found that bacteria attachment to the uncoated BCCs is delayed and individual cells are attracted to the small particle regions of the patterns. Surprisingly, this phenomenon is also observed for the AAMpp-coated BCCs, with bacteria attaching to the small particle regions of the pattern, in stark contrast to uniform flat films of AAMpp that are highly adhesive toward P. aeruginosa. Also, the overall levels of bacterial attachment are significantly reduced by the BCC patterns compared to controls. Thus, there is a trade-off that exists between chemistry and topography that can be exploited to delay the onset of P. aeruginosa biofilm formation on surfaces.