Synthesis of biocompatible surfaces by nanotechnology methods

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SYNTHESIS OF BIOCOMPATIBLE SURFACES BY NANOTECHNOLOGY METHODS 699(a)40(a)55nm4003002001000 100 200 300(b)400 nm4003002001000 100 200 300(c)400 nm4000nm400nm40nmnm0.80.60.40.20 0.2 0.4 0.6(b)0.80.80.60.40.20 0.2 0.4 0.6(c)0.80.8nm045nm0453002001000 100 200 300 400nm0nmFig. 3. 2D images obtained by SPM examination of LDPEsurface modified by N = 30–50 pulses of carbon plasma ata repetition frequency of f = (a) 0.1, (b) 0.3, and (c) 1.0 Hz.nm0.60.40.2nm00 0.2 0.4 0.6 0.8nmFig. 4. 2D images obtained by a SPM examination of thePU surface modified by N = 30–50 pulses of carbonplasma at a repetition frequency of f = (a) 0.1, (b) 0.3, and(c) 1.0 Hz.of the degree of activation of the complement systembased on the general hemolytic activity of the complementin human blood serum. The results showed (seetable) that the proposed modification of the polymersurface by carbon leads to a decrease in the thrombocyte(platelet) adhesion and a drop in the rate constantK ind of induced activation of the complementsystem. These characteristic were calculated using thetimes of the half-lysis of sensitized goat erythrocytesby human blood serum before and after incubationwith a sample. The surface is classified as hemocompatible,provided that its K ind does not exceed 1.5. Itshould be noted that the initial polymer surfaces hadK ind = 5.1 and 5.5 for LDPE and PU, respectively. Ananalysis of data in the table shows that the proposedmodification significantly improves the hemocompatibilityof the polymer surface at an affective carbonfilm thickness of 5–12 nm and cluster dimensionswithin 50–120 nm.NANOTECHNOLOGIES IN RUSSIA Vol. 5 Nos. 9–10 2010
700ALEKHIN et al.Intensite, rel. units30201008001000 1200 1400 1600 1800Wavenumber, cm −1Fig. 5. Analysis of the Raman spectrum of a carbon coatingshowing general line envelope and its components correspondingto sp 2 hybridization, sp 3 hybridization, and misorientedstates, respectively.NANOSTRUCTURAL MODIFICATIONOF POLY(METHYL METHACRYLATE)SURFACE BY A COMBINATIONOF PLASMACHEMICAL TREATMENTAND VACUUM ULTRAVIOLET IRRADIATIONPoly(methyl methacrylate) (PMMA) is now widelyused in practical transplantology as a base material forvarious implants [11].Plasmachemical Processing of PMMA SurfacePreviously, Vasilets et al. [12, 13] showed that plasmachemicalprocessing and vacuum ultraviolet (VUV)irradiation modify the properties of near-surface layersof medical polymers. The destruction of polymers andthe formation of active chemical radicals and speciesunder these conditions make it possible to control thebiocompatibility of the polymers. In particular, themodification of the near-surface layers of a polymerleads to a change in its nanoroughness. In this context,we have studied the effect of plasmachemical treatmentin an oxygen-containing medium at a small partialpressure (~2 Pa) followed by VUV irradiation onthe PMMA surface roughness in a nanometer range.The initial PMMA film with a molecular mass of8 × 10 4 and a thickness of about 0.8 μm was depositedby centrifuging onto a polished Si(100) single crystalsurface (Fig. 6a) and then nanostructured by beingtreated for 20 s in an RF (13.56 MHz) plasma. Theparameters of the surface roughness and geometry ofthe surface features (nanohills and nanograins) onPMMA films were studied by SPM in the atomic forcemicroscopy (AFM) mode on a sample surface area of1.4 × 1.4 μm 2 . The dimensions of the features weredetermined by the computer-aided recognition of thesurface relief, which was performed using the methodof feature-oriented scanning in the virtual regime[14].It was established that the plasmachemical treatmentof a PMMA film led to the formation of flat nanograins(Fig. 6b) with average lateral dimensions ofabout 66 nm, an average height of about 1.8 nm, andan average distance of about 104 nm between adjacentgrains. The number of nanograins per unit surface areawas about 122 μm –2 . The proposed nanostructuretechnology ensures that these results can be easilyreproduced.The formation of surface nanograins can beexplained by local changes in the PMMA film density.These local changes are related to the presence ofinhomogeneities in most polymers, primarily globules/grainsand lamellae, as well as coils, nodes, twists,entanglements, etc. of molecular chains, which agreeswith the results of other investigations [15, 16]. In thecourse ofPMMA treatment in oxygen-containing plasma,the polymer is subject to significant chemical modification,including the formation of polar functionalgroups [17, 128], carbonate (O 2 C=O), and carbonyl(C=O) groups. In addition, there are significantchanges in the binding energies of carbon atoms invarious molecular groups. The content of oxygen inthe near-surface layer exhibits a significant increaseduring the first seconds of treatment; then the growthslows down and eventually oxygen rather slowly penetratesin depth of the material [17].Treatment of PMMA Film Surfaceby VUV RadiationPlasma-treated PMMA samples were exposed tothe radiation of krypton lamps with a characteristicwavelength of λ = 123.6 nm in vacuum at a residualThe dependence that the cluster size, the rate constant (K ads ) of blood plasma protein adsorption, and the rate constant K indof induced activation of the complement system has on the effective thickness of the carbon-containing layer on LDPE surfaceCarbon filmthickness, nmClustersize, nmK ads , ml/(mg s)K indLDPE Vitur LDPE Vitur12 Surface coverage >80% 0.25 0.1 4.3 ± 0.5 3.5 ± 0.4NANOTECHNOLOGIES IN RUSSIA Vol. 5 Nos. 9–10 2010
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