Functional surfaces and interfaces

Resume : Modifying metal or oxide surfaces either to selectively enhance protein or cell adhesion, or, on the contrary to prevent it, has become a challenging issue to face whenmore efficient bisoensorsand/or sophisticated biocompatible materials are needed. Amongst multiple ways of attaching probes on surfaces, like using polymers, thiols, silanes as possible linkers, depending on the substrate nature, we will focus our presentation on two examples: i) the immobilization of a peptides on gold, via various thiol layers, and the subsequent recognition of a protein; by changing the terminal group of the thiol adsorbed on gold, one could covalently attach a peptide, and tune its orientation/conformation on the surface .Going to a more realistic case, anti-GdH antibodies were then either adsorbed or covalently grafted on bare gold, or on SAMs, terminated by various functions, on gold surfaces. Time-of-flightsecondaryion mass spectrometry (ToF-SIMS) and principal component analysis (PCA), in combination withcomplementarytechniques (PM-IRRAS, QCM-D and XPS), were used to characterize, at the molecular scale, the antibody orientation on the surface; anti-GdH-GdH recognition was then evaluated by quartz crystal microbalance (QCM) . This ensemble of results suggests a strong influence of the underlayer, on the grafting mode, on protein orientation and, more important, on the bioactivity of immobilised proteins. ii) the immobilization of an antimicrobial peptide (AMP) on a so strategic materiaReferences V. LEBEC, J. LANDOULSI, S. BOUJDAY, C. POLEUNIS, C.M. PRADIER AND A. DELCORTE Probing the Orientation of b-Lactoglobulin on Gold Surfaces Modified by Alkyl-Thiol Self-Assembled Monolayers, J. Phys. Chem. C, 2013, 117, 11569-11577 -LEBEC, VICTOR; BOUJDAY, SOUHIR; POLEUNIS, CLAUDE; PRADIER, CLAIRE-MARIE; DELCORTE, ARNAUD, ToF-SIMS Investigation of the Orientation of Adsorbed Antibodies on SAMs Correlated to Biorecognition Tests J. Phys. Chem. C., 2014, 118(4), 2085-2092 J. PEYRE, V. HUMBLOT, C. METHIVIER, J.-M. BERJEAUD, C.-M. PRADIER Co-Grafting of Amino-Poly-Ethylene-Glycol and Magainin I on a TiO2 Surface; Tests of Antifouling and Antibacterial Activities J. Phys.Chem. B 2012, 116, 13839-13847

Resume : Nanostructured surfaces have demonstrated extraordinary capacity to influence and strongly modulate the biointerfacial interactions, including protein adsorption and subsequent cellular responses, although the mechanisms are still not clear. The adsorption, desorption, and conformational changes of proteins interacting with surfaces are important processes for understanding the influence on the adsorbed layers. When materials have structures on the nanometer scale, the protein function can be altered. A range of nanoscale material properties influence these interactions. The ability to manipulate both material nanochemistry and nanotopography remains challenging in its own right. A versatile and simple approach to build-up tunable hybrid nanowell arrays on surfaces is presented here. The preparation method implies spin coating of polycrystalline gold surfaces by means of monodisperse silica nanoparticles, providing a monolayer of ordered colloidal crystals. A thin polymer layer is then deposited on samples to embed the silica nanoparticle array. The selective removal of the nanospheres, afterwords, leads to the formation of nanowell arrays, having internal bottom area of gold surrounded by polymeric matrix, spanning over a micron-sized area. Nanowells of about 0.3 attolitre each, with a density of 109 wells/cm2 can be easily produced and, due to their hybrid chemical structure (polymer walls and metallic bottom), are shown to behave indeed as selective nanocontainers for simple biomolecules. As proof of concept, simple model proteins, e.g., Human Lysozyme and Human Serum Albumin and their own antibodies have been chosen for this study. The driving chemical factors of adsorption selectivity are discussed in terms of surface free energy gradients and chemical termination of the pore bottom and walls, respectively.

Resume : The functionalization of the surface of nanosized transition metal sulphides represents one of the most exciting challenges in the field of the synthesis of inorganic nanostructures. Whereas transition metal oxides are easily derivatized by using, inter alia, carboxylic, phosphates and hydroxylic moieties (e.g. cathecols), the stable anchoring of ligands on the homologues metal sulphides is conversely very demanding. Furthermore, most of the retrieved studies report the occurrence of a functionalization without unravel which kind of interactions rules the anchoring of the ligand on the surface. In fact, both the surface chemistry of metal sulphides as well as the nature and stability of the interaction between the metal sulphide surface and ligand moieties are far from being understood. In this framework, we undertook a comprehensive study based on a tight synergy between spectroscopic investigations and theoretical modelling to study the surface of zinc sulphide nanostructures as model system. The ZnS nanoparticles were produced by a simple, reproducible low temperature hydrothermal route starting from an aqueous suspension of zinc salt and Na2S. Pure sphalerite ZnS nanocrystals were obtained at 135°C. The surface composition was investigated by XPS, FT-ATR and Raman spectroscopies, whereas chemisorption studies with small molecules (CO, pyridine, H2O) was carried out by FT-IR. The experimental investigations were complemented by Density Functional Theory (DFT) studies.

Resume : Polyelectrolyte multilayers (PEMs) exhibit exceptional properties such as their easy fabrication, the ability to control the thickness in the nm range and the possibility to embed various functionalities. Particularly, the use of polyelectrolytes bearing ion-selective groups enable the preparation of ion-selective PEMs. In this work we have chemically functionalized a polycation with a guanidinium (Gu) moiety, which is known to bind oxyanions. This new derivative was used to prepare PEMs. The formation of these PEMs and their non-functionalized equivalents was monitored real-time with optical reflectometry and a quartz crystal microbalance equipped with dissipation monitoring (QCM-D). Differences in the adsorbed amount, wet layer thickness, layer rigidity and pH stability are rationalized by the additional Gu-polyanion interactions, also affecting the conformation of the polyelectrolyte chains in the PEM. Furthermore, QCM-D analysis of the layer properties upon the exposure to aqueous solutions of different sodium salts suggest a high binding affinity and selectivity for H2PO4- over other anions. This can be explained by the differences in the hydration properties and the valency of the anions as well as by the strong interactions between Gu and H2PO4-. It is anticipated that compounds like the presented Gu-functionalized polyelectrolyte will facilitate the further development of ion separation/recovery systems and H2PO4- sensors.

Resume : Core/shell colloids are intensively investigated for broadband light trapping and management, because they can play as optical cavities and directly take advantage of morphology dependent resonances. The same properties can be exploited in imaging and vibrational spectroscopy (Raman, IR), in order to enhance their analytical sensitivity. [1-3] Moreover, the synergistic combination of plasmonic nanoantennas with dielectric core/shell colloids allowed for fabricating near-field optical light concentrators, which are very efficient in stimulating photon-driven processes at metal-semiconductor interfaces and show an impressive decrease in degradation time (minutes instead of hours) of organic pollutants. [4] This presentation will review some applications of core/shell light nanoconcentrators as non-plasmonic Raman enhancers, which have been used to investigate biochemical reactions in aqueous environment, and their coupling to plasmonic nanoantennas for promoting and in-situ monitoring light-assisted chemical reactions.[1-6] References 1) I. Alessandri, J. Am. Chem. Soc. (2013) 135(15), 5541-5544. 2) I. Alessandri et al., RSC Adv. (2014) 4, 38152-38158 3) I. Alessandri et. al., Small (2014) 10, 1294-1298. 5) M. Salmistraro et al., Small (2013) 9, 3301-3307 6) G. Sinha et al. ACS-Appl. Mater. Interf. (2011) 3, 2557-2563.

Resume : In the current research field of energetic materials, effective destructibility as well as high safety has been the most important performance for munitions used in modern weapons. Therefore, considerable efforts have been devoted to exploring the desensitization strategies of nitramine explosives (RDX, HMX and CL-20) with high energy. In this paper, melamine-formaldehyde resins were selected for the fabrication of three typical nitramine explosives based microcapsules, the polymer coating shell could be prepared via a facile in situ polymerization of melamine and formaldehyde on the surface of explosive crystals. Structural characterizations and thermal properties of the core-shell composites were systematically studied by SEM, XPS, XRD, FT-IR and DSC. The SEM and XPS results indicated that a compact coating with high shell coverage close to 100% was obtained for these three energetic cores. XRD and FTIR analyses showed the combined characteristics of explosives and MF resins, and revealing that the polymorph of CL-20 maintained the optimal ε form during the whole preparing process. After coating, the endothermic polymorphic phase transition as well as the exothermic thermal decomposition temperature of the explosives was visibly increased, attributing to the outstanding heat resistance of MF resin shell. The impact sensitivity tests showed that the sensitivity of the resultant microcapsules could be reduced markedly after coating by 3 wt% MF resins.

Resume : The need of recognizing antigens present on cells or in biological liquids, for liquid biopsy, is at present a challenge which is faced by many laboratories for reaching lower detection limits. Nanoparticles functionalized with antibodies are new materials which are emerging as platforms for imaging, analytical aims or also for drugs delivery. We will show our results starting from the synthesis of nanoparticles with plasmonic, superparamagnetic and superparamagnetic/plasmonic properties that we obtain by laser ablation synthesis in solvents (LASiS) and that offers nanoparticles with naked surfaces in pure solvents. We functionalize the naked nanoparticles with antibodies at different concentrations and look at their activity against selected antigens. Concentration dependent activity shows that an organization of the antibodies is operating on the surface of the nanostructures. We will show how antibodies for two membrane prostatic cancer antigens (PSMA and PSCA) are active in a multiplexed approach using the plasmonic related SERS effect. 1 M. Meneghetti, et al. Small,(2012) 8, 3733 2 F. Bertorelle, et al. J. Phys. Chem. C (2014) 118, 14534 3 V. Amendola, et al. Small (2014) 10, 2476

Resume : Carbon nanotubes have been proposed for several biomedical applications: They can cargo drugs to be released in a precise location in a cell or in the body, they can be functionalized with antibodies to be used as sensors, and they can be employed for biological imaging due to their emission in the second optical window of biological tissues. Their only drawback is their low emission yield, which is typically below 1%. To overcome this limit, we have recently implemented a hybrid nanoplasmonic colloidal system by dispersing single-walled carbon nanotubes in gold nanorods suspensions [1]. The hybrid structures exhibit enhanced luminescence, overcoming the low-emission yield of carbon nanotubes. This simple, robust and flexible technique enhances even the luminescence of tubes with chiralities whose enhancement was never reported before. The metal enhanced luminescence can be realized either by coupling of the plasmon resonance with the excitation of the CNT, ascribed as proximity mechanisms, or by coupling between the surface plasmon resonance with the emission of the CNTs, the radiating plasmon model. Here we will present our results on time resolved measurements in order to clarify the coupling mechanism between the CNTs and the plasmonic nanoparticles, as well as photoluminescence and Raman characterization of the nanohybrids. References [1] M. Glaeske and A. Setaro, Nano Research 6, 593, 2013.

Resume : Synthesis of aqueous nanogel particles can be performed in controlled way to tune particle size and size distribution, chemical functionality, surface charge, swelling degree, colloidal stability and stimuli-sensitivity. The post-modification reactions provide a tool-box for incorporation of small organic molecules, synthetic polymers, biopolymers or inorganic nanoparticles into colloidal nanogel network thus leading to the formation of multifunctional colloids. Such colloids may exhibit electrical conductivity, magnetic response, optical and catalytic activity and can be used as building blocks for the preparation of well-ordered nanostructured materials of different dimensions and complexity. By controlled self-assembly of nanogels in solution, on interfaces or surfaces defined architectures like colloidosomes, fibers, networks, arrays or films can be obtained. In present paper we will present some examples for the use of nanogels as functional stimuli-responsive building blocks for decoration of surfaces. We have developed a simple route for the preparation of the novel multi-sensitive nanogel-based capsules.1,2 The variation of the microgel and polymer properties as well as their concentration provides a control over important capsule wall parameters such as size, morphology, wall thickness, degradability etc. Nanogel- and nanogel/polymer-based composite microfibers can be prepared by electrospinning process.3 Obtained microfibers with tuneable dimensions, swelling behaviour and mechanical properties have been obtained by varying the nanogel properties (size and chemical structure), nanogel/polymer ratio and viscosity of spinning solution. The printing of nanogel arrays on solid substrates using nanostructured substrates as stamps was developed. The size, crosslink density and surface chemistry are important parameters that control the morphology and mechanical properties of printed structures.4 Obtained nanogel-based arrays and films are used for cell guidance, tissue regeneration, antibacterial and antifouling coatings. [1] S. Berger, H. Zhang, A. Pich, Adv. Funct. Mater. 2009, 19, 554-559. [2] G. Agrawal, X. Zhu, M. M?ller, A. Pich, , Chem Mater, 2014, 26, 5882?5891. [3] D. Kehren, A. Pich, Macromol. Mater. Eng. 2013, 12, 1283-1293 [4] S. Hiltl, M. Sch?rings, A. Balaceanu, V. Mayorga, C. Liedel, A. Pich, A. B?ker, Soft Matter 2011, 7, 8231-8238.

Resume : The phase behavior of an amphiphilic block copolymer based on a poly(aspartic acid) hydrophilic block and a poly(n-butyl acrylate) hydrophobic block was investigated at the air-water and air-buffer interface. The polymer forms stable monomolecular films on both subphases. At low pH, the isotherms exhibit a plateau. Compression-expansion experiments and infrared reflection absorption spectroscopy suggest that the plateau is likely due to the formation of polymer bi- or multilayers. At high pH the films remain intact upon compression and no multilayer formation is observed. Furthermore, the mineralization of calcium phosphate beneath the monolayer was studied at different pH. The pH of the subphase and thus the polymer charge strongly affects the phase behavior of the film and the mineral formation. After 4 h of mineralization at low pH, atomic force microscopy shows smooth mineral films with a low roughness. With increasing pH the mineral films become inhomogeneous and the roughness increases. Transmission electron microscopy confirms this: at low pH a few small but uniform particles form whereas particles grown at higher pH are larger and highly agglomerated. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirm the formation of calcium phosphate. The levels of mineralization are higher in samples grown at high pH.

Resume : Hyaluronic acid (HA) is a major intracellular component of connective tissues. However, it does not support cell attachment and spreading and needs chemical modification to support cellular adhesion. In the present study, polyelectrolyte multilayer films of HA-Aldehyde derivative and Poly-L-lysine (PLL) were built up by layer-by-layer method. HA-aldehyde is crosslinked by hydrolytically labile imine bond between amino groups of one polymer and aldehydic derivative of HA. The main objective was to optimize the polyelectrolyte multilayer film growth and control cytokine release. The aim is to decrease the implant and medical device failure due to adverse immune reactions by developing an innovative immunomodulatory system. The results confirmed the hypothesis that this polyelectrolyte multilayer can be successfully deposited onto the biomaterials surface. Biofunctionalization of these films can be envisioned by introducing bioactive molecules, which was done by incorporation of Interleukin-4 (IL-4). Moreover, drug release behavior could be modulated as afunction function of the physical property of the films. Our current focus is to use the controlled release capacities for the delivery of immunomodulatory cytokines such as IL-4 and quantification of its effect on primary macrophages. Our results showed that the cytokine release profile of primary macrophages can be significantly affected by the controlled delivery of an anti-inflammatory cytokine.

Resume : The goal of tissue engineering is to assemble functional constructs that restore, maintain, or recover damaged tissues or whole organs; in this field of research, self-assembling peptides (SAPs) are an appealing class of materials due to their skill to organize in nanostructured hydrogels that can be successfully anchored to appropriate substrates [1] or directly injected into a lesion. SAPs scaffolds are able to mimic the structure of the extra-cellular matrix (ECM), offering tridimensional support for cell growth and/or becoming vehicles for the delivery of stem cells or drugs [2]. Indeed these nanomaterials, possibly combined with growth factors, may constitute a biomimetic matrix with the capability of surrounding cells and promoting specific interactions with these, allowing to control and to modulate their behavior by mimicking their native environment. The achievement of SAPs should include a first step of chemical and structural characterization, to check the stability and protection of the molecular structure during scaffold’s development. In this work, we present an accurate spectroscopic investigation of different classes of SAPs using X-ray photoelectron spectroscopy (XPS) and Fourier-Transform Infrared spectroscopy (FT-IR) techniques. XPS and FT-IR are successfully used to probe the chemical composition, molecular structure and conformation of the proposed materials. [1] M. Dettin et al., J. Pept. Sci. 2014, 20, 585 [2] R. Flamia et al., Biomacromol. 2007,8,128

Resume : Non covalent surface functionalization approaches based on spontaneous adsorption and arrangement of molecules from a solution onto a solid surface is a common phenomenon, but its rationalization and control is extremely complex since it is driven by different weak interactions, including van der Waals, hydrophobic, and electrostatic forces. This aspect is particularly critical in water, where dispersive interactions are dominant. The comprehension of the interactions involved in the mechanism of spontaneous adsorption of functional molecules from aqueous solution to nanostructured inorganic surfaces paves the way for a straightforward and environmentally friendly development of functional materials, biomaterials, and sensing devices. Polylysine (PL), is a water soluble biomolecule that can assume three canonical conformations (alpha-helix, random coil and beta-sheet) depending on pH and temperature of solution. PL spontaneous deposition on surface is widely employed to promote cell adhesion or deposition of ionic biopolymers and biomolecules. Herein, we provide experimental evidences to demonstrate that PL secondary structure profoundly influences the outcome of its spontaneous deposition on quartz surfaces. Accordingly, PL deposition on quartz (and other inorganic surfaces) is optimised working in an unexpected pH condition. The interaction of PL treated substrates with porphyrins and calixarenes shed light on the possibility to build up on surface supramolecular architectures using full non-covalent approaches. The proposed methodology is proven robust and repeatable and compatible for combination with a wide selection of inorganic nanomaterials.

Resume : To the purpose of modeling processes after implantation of bioactive synthesized HAp ceramic and to evaluate bioadhesion to cell culture, biofilm growth and cytotoxicity of domestic biphasic calcium phosphate (BCP) ceramics (Lab.synthesis in Dep. Analytical Chemistry and Functional Ceramics, IPMS NASU , Kyiv) on different stages of their interaction with the environment of tissue in vitro studies have been carried out using cell cultures. The conventional method of culturing cells have been used with HEP- 2 cells in DMEM culture medium (Sigma, USA) and with addition of penicillin, streptomycin and 5% fetal calf serum in 24 well plates in an incubator at 37 ° C in atmosphere with 5% СО2. The replacement of the culture medium performed every second day. Such varieties of the BCP ceramics have been used: powders with hydroxyapatite (HAp)/tricalcium phosphate (TCP) ratio = 80/20; powders with Hap/TCP = 50/50. In two parallel experiments the freshly calcined ceramics or the same ceramics that was modified by overnight exposure in helofuzyn have been used. The cells investigations by the inverted microscopy and fluorescent microscopy methods have been carried out. All experiments showed tight adhesion of cells to ceramic and active multilayered cell growth at the surface area. It was revealed that the freshly calcined ceramics inhibit the cells growth during the first 1.5 - 2 days compared to the ceramics modified by helofuzyn. Fluorescent study also found a higher level of luminescence of nuclei and cytoplasm of cells near and on the modified ceramics at the first few days of cultivation, reflecting the increase in their proliferate activity. These features can be explained by the active adsorption of culture medium components on the surface of freshly calcined ceramics and the excretion of some elements from these surfaces accumulated on them due to segregation processes during calcination. These processes are especially significant during first time after implantation and are accompanying by local changes in pH and ionic composition of the solution, which causes an initial delay in cell growth.

Resume : The interest in obtaining biodegradable nanostructured films produced from natural sources has increased in recent years due to low cost, free toxicity and the possibility to use this products in multiple fields. The basic materials used to produce nanostructured biodegradable films are combinations from various polymers, polysaccharides, proteins, chemically modified pectin and lipids compounds. This study has focused on extending the functional properties of the polysaccharides-chitosan with different natural compounds to yield antioxidant biodegradable and bioactive nanostructured films. The microstructure was investigated by AFM, SEM and high resolution optical microscopy and mechanical and rheological properties with dynamic mechanical analyzer (DMA). In addition the antioxidant characteristics of the biodegradable nanostructured films have been investigated in vitro non cellular by chemiluminescence and DPPH (2,2-diphenyl-1-picrylhydrazyl) methods. Keywords: nanostructured films, antioxidant characteristics, chemiluminescence, rheological properties

Resume : There is a great deal of interest in regenerative medicine due to its capability to generate powerful new treatments for a wide range of diseases and injuries; in this context, self-assembling peptides (SAPs) are an appealing class of materials due to their ability to organize in nanostructured hydrogels that can be directly injected into a lesion. SAPs scaffolds are able to mimic the structure of the extra-cellular matrix (ECM), offering tridimensional support for cell growth. Indeed these nanomaterials may constitute a biomimetic matrix able to surround cells and promote specific interactions, as to control and modify their behavior by mimicking their native environment. The ideal matrix has a 3D geometry similar to the ECM and is able to promote cell adhesion, proliferation, infiltration and differentiation aimed at new tissue formation. In this study, three small elastin-like peptides containing 3-fold repeated motifs (i.e. (VGGLG)3, (LGGLG)3 and (LGGVG)3) were chemically characterized by XPS and FT-IR to probe their chemical composition, molecular structure and conformation. Then, an accurate investigation of the biological properties of the SAPs and their interaction with cells was performed, by culturing cells in the presence of the SAPs as to assess if elastin-like fibrils exert cytotoxic effect and to evaluate biocompatibility, cellular adhesion and proliferation.

Resume : Microbial fuel cell(MFC) systems use electrochemically active biofilm which can exchange electron discharged from internal metabolic pathway into electrically conductive electrode as terminal electron acceptor and/or donor. Conventionally MFC has been applied to produce renewable energy such as electricity and hydrogen from various biodegradable organic materials, and biosensor for organic contaminant monitoring. We investigated the effect of Ti nano-particle on the electron generating efficient of MFC by deposition of nano-particles on the carbon paper electrode. Since the generated voltage and current from MFC are depend on the amount of microbes which are attached on the anode, a surface area and bioaffinity of electrode materials are important factor. By monitoring the voltage of MFC which employing Ti-nano-particle, we evaluated and compared performance enhancement with a case of general carbon paper anode. Also, an influence of nano-particle size and gap of inter-particle variation were investigated. To understand a mechanism of electron transport from alive microbe to conductive electrode, we need to observe an individual electrochemically active bacterium such as Shewanella oneidensis MR-1by using nano-probing technique. The electrical properties such like resistance and dielectric constant of microbes were analyzed by scanning probe microscopy(SPM) with conductive cantilever tip and nanowire of microbe which known as an electrical pathway to transmit an electron to the electrode were characterized with a various mode of SPM. To investigate an interaction between microbe and anode electrode with Ti nano-particle would be a clue for understanding of electron generation and transmission mechanism.

Resume : Abstract: Porous silicon powder finds several applications in different areas due to number of properties that make it an attractive material. Within this context, a facile method for the low-cost and large-scale production of Porous silicon (pSi) microparticles, in diverse sizes and shapes, has been used. This method consists of exposing silicon powder to a mixture of HF/HNO3 at specific conditions. Tow samples of the silicon microparticles were analyzed which include the starting metallurgical grade silicon powder and the sample that have been exposed to chemical vapor etching(CVE) . This method lead to the formation of porous silicon nanosponge microparticles. The nanostructured powder has been functionalized with 3-aminopropyl triethoxysilane ( APTES) molecules. These later were intended to work as coupling agent for biosensing applications. Morphologies of pSi microparticles were characterized by scanning electron microscopy (SEM). Fourier transform infra-red (FTIR) and Raman spectroscopic analyses have shown that the APTES molecules are attached to the surface of porous silicon powder.

Resume : In recent years, artificial bio-membrane system (e.g. artificial kidney or artificial aquaporin) has been intensively researched to develop the water molecule transportation system based on artificial nano channel system. Especially, single-file transport of microscopic particles, including atoms, ions, molecules, through nano-fluidic channels is a promising topic for applications of the sensing and manipulation of biomolecules. Unlike micro-sized particles, the selective transportation of ions is difficult in water, because the dissolved ions are very small. However, the control of ions and molecules transportation in water is very significant in order to develop artificial bio-membrane systems. Therefore, we investigated the selective ion transportation in NaCl solution by using electrical bias on the conductive membrane. The surface functionalization by using ALD (Atomic layer deposition) process on membrane was also studied for higher selectivity of ion transportation. The effect of electrical bias and surface functionalization of membrane on the ion selectivity in fluidic system will be presented.

Resume : Carbon materials are widely used for medical applications due to their biocompatibility, hemocompatibility and low toxicity. Many of their biomedical applications rely on the ability to control the carbon/water interfacial properties, particularly, surface charge density. It is known that surface charge density plays a major role in the interaction between carbon surfaces and biomolecules. In this work we present a detailed study of the charge density of amorphous carbon thin film surfaces, as a function of pH and surface chemistry. A surface zeta potential (SZP) cell was used to measure the surface charge density of carbon thin films using the tracer particle method. Surface zeta potential was measured for three types of carbon surfaces: amorphous carbon (a-C), oxidized amorphous carbon (a-C:O) and hydrogen doped amorphous carbon (a-C:H). At neutral pH, a-C and a-C:H show similar surface zeta potential whereas a-C:O displays a lower SZP. For all surfaces, pH measurements reveal a pH-dependent surface zeta potential. Infrared and X-ray photoelectron surface spectroscopies were used in order to relate SZP to carbon surface chemistry. We show that the tracer particle technique is a rapid method for determining SZP values on carbon thin films, with precision < 10%.

Resume : Understanding cellular responses to wide range of configurations of surface topographical features is a major issue in cell-surface interfaces dictating the biological reactions. Within this context, our work presents an in vitro study to identify the influence of substrate features and topography on cell viability, morphology, and spreading. Large area polymeric microstructured surfaces were obtained by replication from matrices of polycarbonate ablated using excimer laser processing technique. Interbedded elongated shape pattern coated with Titanium (10-45 μm width and 20 μm height) with specific designed micro-architecture were used as substrates for the biocompatibility studies in vitro. Cell viability and proliferation were assesed by MTS colorimetric assay. ELISA-type method was used to measure the pro-inflammatory cytokine TNF-α release from THP-1 cells differentiated to macrophages. Macrophages immunolabelled for actin and vinculin-proteins were analyzed. Data obtained from immunofluorescent imaging studies show that macrophages spread and adhere to titanium coated surfaces in closed contact with elongated motif which creates a good pattern for cell attachment. THP-1 cells cultured either on glass coverslip or titanium covered surfaces with or without micropattern do not led to a detectable inflammatory effect. The financial support offered by SCIEX and CNCSIS through PCCA 239/2014 contract is acknowledged

Resume : One of the main goals of solar energy conversion technology is to mimic natural photosynthesis. In dye sensitized solar cells, a dye captures the sunlight and produces an electron injection to a metal oxide conduction band. However, in natural photosynthesis, the electron transfer process is mediated by peptide matrices. In this work we have emphasized all the advantages of peptide materials in solar energy conversion technology. We have inserted, between the dye and the surface, an hexapeptide spacer able to attain a helical structure, because exclusively formed by the α-aminoisobutyric acid residue. [1] We demonstrate that the peptide generates a compact and stable monolayer on surface, which inhibits the direct contact of the dye and the electrolyte solution with titania. Furthermore the peptide spacers maintain the dyes quite distant from each other and from the surface, minimizing excited state interactions. The peptide was covalently linked to the surface at the N-terminus, in order to address the electronic flow from the solution to the surface. This design increases the conversion efficiency, with respect to the value obtained when the dye was simply layered on the TiO2 surface, suggesting that helical peptides can be considered very promising materials to be used in DSSC technology. [2] [1] Gatto E. et al. Langmuir 28, 2817−2826 (2012). [2] Gatto E. et al. ChemPhysChem 15, 64-68 (2014).

Resume : ZnO is a piezoelectric, wide-band-gap semiconductor used in sensors, biosensors and various electronic devices. The functionalization of ZnO nanostructures with covalently anchored SAM is a promising approach towards stable and versatile surfaces with controlled properties. In this contribution, nanocolumnar ZnO films were functionalized with two cavitand receptors suited for molecular recognition. Films were grown by Metal Organic Chemical Vapor Deposition and characterized by XRD, SEM and Piezoelectric Force Microscopy to evaluate piezoelectric properties. In order to introduce cavitand receptors on the ZnO surface a multi-step route was adopted. In the first step a bifunctional phosphonic linker, either the 10-undecynylphosphonic acid or the 12-azidodecylphosphonic acid, was anchored on ZnO through the phosphonic group; in the second one a tetraphosphonate cavitand (Tiiii) modified with an azide moiety and a quinoxaline bridged cavitand (QxCav) bearing 4-alkyne moieties were bonded respectively either to the alkyne or azide terminations of the phosphonic monolayer through a azide-alkyne 1,3 dipolar cycloaddition. Each reaction was monitored by using X-ray photoelectron spectroscopy. Tiiii functionalized ZnO surfaces were proved to complex N-methyl ammonium derivatives, such as, sarcosine, a biomarker for prostate cancer, neurotrasmitters and N-methylated antitumoral drugs, whereas QxCav-modified ZnO nanostructures were able to detect aromatic compounds.

Resume : The performance of implant materials depends on their bulk physical properties as well as on their surface properties. Implant surface topography can mediate cell responses at the interface with the surrounding tissue. Laser micro-machining is a surface modification strategy that creates highly controlled textures. Here, two implant biometals, stainless steel 316L and titanium alloy Ti6Al4V were microtextured with different surface patterns and with differing spacing, by means of UV nanosecond Nd:YVO4 laser structuring. Confocal and scanning electron microscopies were used to characterize the topographic modifications. To study the effects of the topographic changes on cell behavior we performed a viability assay with human bone derived cells (HBCs) isolated from trabecular bone by explant culture. Cells were seeded (104/sample) on the metal surfaces and differences in viability were quantified with the AlamarBlue® method. Cells attached and were viable on all the surfaces tested. We found significant differences in cell viability due to the different laser treatments. In particular, cell viability was slightly better in the Ti6Al4V samples than in the 316L samples. Also, the pit morphology was preferred to the grooves and increasing the spacing between features also increased cell viability. These results indicate the potential of UV nanosecond laser treatment as a relevant tool to precisely modify implant surface micro-structuring and influence cell behavior.

Resume : Efficient detection and removal of hexavalent chromium from water is still an urgent task in environmental remediation. Ceramic materials are highly suitable as adsorbents due to their chemical and thermal resistance and superior mechanical strengths. Here we will present the synthesis of micron-sized yttria-stabilized zirconia (YSZ) beads obtained through ionotropic gelation and their structural and functional characterization. The microbeads feature a high specific surface area, open porousity and tailorable pore size distribution. In particular, the efficiency of these beads in adsorption of Cr(VI) from aqueous samples was tested in a series of complementary experiments involving total x-ray fluorescence (T-XRF) and microRaman analysis. These data show that YSZ beads can play as very efficient Raman substrates, allowing for detection of Cr(VI) at very low concentration (ppm). These beads can be further functionalized with specific receptors and combined to nanocatalysts to promote conversion and simultaneous removal of different chromium species.

Resume : To the purpose of modeling processes after implantation of bioactive synthesized HAp ceramic and to evaluate bioadhesion to cell culture, biofilm growth and cytotoxicity of domestic biphasic calcium phosphate (BCP) ceramics (Lab.synthesis in Dep. Analytical Chemistry and Functional Ceramics, IPMS NASU , Kyiv) on different stages of their interaction with the environment of tissue in vitro studies have been carried out using cell cultures. The conventional method of culturing cells have been used with HEP- 2 cells in DMEM culture medium (Sigma, USA) and with addition of penicillin, streptomycin and 5% fetal calf serum in 24 well plates in an incubator at 37 ° C in atmosphere with 5% СО2. The replacement of the culture medium performed every second day. Such varieties of the BCP ceramics have been used: powders with hydroxyapatite (HAp)/tricalcium phosphate (TCP) ratio = 80/20; powders with Hap/TCP = 50/50. In two parallel experiments the freshly calcined ceramics or the same ceramics that was modified by overnight exposure in helofuzyn have been used. The cells investigations by the inverted microscopy and fluorescent microscopy methods have been carried out. All experiments showed tight adhesion of cells to ceramic and active multilayered cell growth at the surface area. It was revealed that the freshly calcined ceramics inhibit the cells growth during the first 1.5 - 2 days compared to the ceramics modified by helofuzyn. Fluorescent study also found a higher level of luminescence of nuclei and cytoplasm of cells near and on the modified ceramics at the first few days of cultivation, reflecting the increase in their proliferate activity. These features can be explained by the active adsorption of culture medium components on the surface of freshly calcined ceramics and the excretion of some elements from these surfaces accumulated on them due to segregation processes during calcination. These processes are especially significant during first time after implantation and are accompanying by local changes in pH and ionic composition of the solution, which causes an initial delay in cell growth.

Resume : The development of coatings and surface modification strategies capable of preventing/minimising surface fouling with biomolecules has received much attention. We have recently reported on the use of aryldiazonium salt chemistry as a one-step, solution-based method for the glycosylation of carbon surfaces, leading to the formation of strongly bound carbohydrate adlayers. Herein we report a detailed study of protein adsorption at carbohydrate-modified amorphous carbon surfaces (a-C) using a combination of spectroscopic and nanogravimetric methods. The adsorption of three proteins, bovine serum albumin (BSA), lysozyme (Lyz) and fibrinogen (Fib), from buffer saline solution was investigated using surfaces coated with four different monosaccharides. We show results indicating that the carbohydrate layer significantly reduces surface protein adsorption. Surface energy determinations using the OWRK model suggest that changes in surface energy are partly at the origin of the observed antifouling behaviour. Moreover we show that coatings obtained using more structurally complex carbohydrate aryldiazonium precursors can further reduce protein adsorption by introducing steric repulsion effects. Finally, we report quantitative determinations of surface charge density at coated and uncoated surfaces and discuss the relation between protein adsorption and coating charge and molecular composition.

Resume : Opportunistic infections around implants upon implantation can cause post-surgical complications. To prevent intensive immune response, infections of yeast and fungi and development of bacterial biofilms, we designed a release system which not only releases an antimicrobial peptide, catestatin (CAT), but due to one of its components, polyarginine (PAR), is antimicrobial itself. We hypothesized that polyarginine (PAR), a synthetic cationic polypeptide, can both act on macrophages and also act as an antimicrobial agent; as arginine is an important component of macrophage metabolism and also it is prominently present in antimicrobial peptides. For this purpose we developed polyelectrolyte multilayer (PEM) films based on PAR and Hyaluronic Acid (HA), which is also a known immunomodulator. We showed that PAR/HA and PAR/HA+CAT coatings have a strong inhibitory effect on production of inflammatory cytokines released by human primary macrophages indicating that this coating will inhibit chronic inflammatory reaction to the implant. The cytocompatibility of the films was checked by human umbilical vein endothelial cells (HUVECs). We observed that PAR/HA coating is cytocompatible. Then we demonstrated that, PAR has an antimicrobial activity both in solution and in film format. PAR in solution was effective against S. aureus for one day. In order to achieve long-term antimicrobial activity, we deposited PAR/HA films on a nanoscale layer of silver coated titanium implants. In this construct, release system acts as a “masking” system where the silver coating is preserved for a longer time. Additional silver release resulted in 5 days of active antimicrobial effect under repeated infection. Our self-antimicrobial coating system also was shown to be effective against Candida albicans and Aspergillus fumigatus. This multilayered infection control system shown to be effective as releasing system but also at the surface level. Thus, it can be used for coating of complex implants, especially in nonsterile environments such as tracheal implants.