Initial attachment of osteoblastic cells onto sol-gel derived fluoridated hydroxyapatite coatings

Initial cell attachment and spreading of anchorage-dependent cells onto the material surface are crucial concerns for the development of more effective implants. In this study, MG63 cells were employed to investigate the initial cell response to sol-gel derived fluoridated hydroxyapatite (FHA) coatings. Along with that, surface roughness, wettability, and protein adsorption were also characterized for those FHA coatings, respectively. It was observed that both the surface roughness and contact angle have a slight increase in response to the incorporation of more fluorine ions. All FHA coatings showed similar amount of adsorbed proteins (approximately 1.6 microg/cm(2)) upon testing in culture medium. Cell counting showed that no significant difference was observed for the amount of initially attached cells between HA and fluoridated HA coatings during the first 4 h culture. On the other hand, the well-spread cell on all prepared coating surface indicates that the incorporated fluorine ions have no adverse effect on cell spreading process. Therefore, it was suggested from this study that the prepared fluoridated hydroxyapatite coatings have comparable bioactivity to that of pure hydroxyapatite coating, and these results are meaningful for further investigation for application of FHA coatings.     

Grafting of dermatan sulfate on polyethylene terephtalate to enhance biointegration

The aim of the present study was to achieve the immobilization of dermatan sulfate (DS) on polyethylene terephthalate (PET) surfaces and to evaluate its biocompatibility. DS obtained from the skin of Scyliorhinus canicula shark was immobilized via carbodiimide on knitted PET fabrics, modified with carboxyl groups. PET-DS characterization was performed by SEM, ATR-FTIR and contact angle measurements. Biocompatibility was evaluated by investigating plasma protein adsorption and endothelial cell proliferation, as well as by subcutaneous implantations in rats. The results indicated that DS immobilization on PET was achieved at ~8 μg/cm2. ATR-FTIR evidenced the presence of sulfate groups on the PET surface. In turn, contact angle measurements indicated an increase in the surface wettability. DS immobilization increased albumin adsorption on the PET surface, whereas it decreased that of fibrinogen. In vitro cell culture revealed that endothelial cell proliferation was also enhanced on PET-DS. Histological results after 15 days of subcutaneous implantation showed a better integration of PET-DS samples in comparison to those of nonmodified PET. In summary, DS was successfully grafted onto the surface of PET, providing it new physicochemical characteristics and biological properties for PET, thus enhancing its biointegration.     

Adhesion and proliferation of rat vascular smooth muscle cells (VSMC) on polyethylene implanted with O+ and C+ ions

Polyethylene was implanted with 30-keV oxygen (PE/O+) or 23-keV carbon ions (PE/C+) at 10(13) to 5 x 10(15) ions cm(-2) doses in order to improve the adhesion of vascular smooth muscle cell (VSMC) to the polymer surface in vitro because of its oxidation and carbon-enrichment. The concentration of -CO- groups in the PE/O+ and PE/C+ samples increased only up to doses of 3 x 10(14) and 10(15) ions cm(-2), respectively, and then declined. At the same time, the concentration of these groups, measured at a dose of 3 x 10(14) ions cm(-2), was higher in PE/O+ than in PE/C+ samples. Similarly, the number of initially-adhering rat VSMC (24 h after seeding) increased only up to a dose of 3 x 10(13) and 10(15) ions cm(-2) on PE/O+ and PE/C+ samples, respectively. In addition, between doses of 10(13) and 10(14) ions cm(-2), this number was about two to three times higher on PE/O+ samples. On the other hand, the surface wettability increased proportionally to the implanted ion dose, especially above a dose of 10(14) ions cm(-2). Thus, the number of initially-adhered cells appeared to be positively correlated with the amount of the oxygen group present at the polymer surface rather than with the surface wettability. The higher cell adhesion was accompanied by adsorption of fluorescent dye-conjugated collagen IV in larger amounts. The highest numbers of initially-adhered cells were usually associated with the lowest rates of subsequent proliferation (measured by the doubling time, BrdU labelling and M     

Protein adsorption resistance and oxygen permeability of chemically crosslinked phospholipid polymer hydrogel for ophthalmologic biomaterials

The biomimetic structure of a polymer hydrogel bearing phosphorylcholine groups was obtained from 2-methacryloyloxyethylphosphorylcholline (MPC) and a novel crosslinker, 2-(methacryloyloxy)ethyl-N-(2-methacryloyloxy)ethyl]phosphorylcholine (MMPC), to prepare biocompatible ocular materials. MMPC is a dimethacrylate with phosphorylcholine-analogous linkage. Previous reports clarified that the affinity of MMPC to MPC enables the water contents and mechanical properties of the poly(MPC) hydrogels to be varied without disturbing the bulk phases. In this study, we examined the protein adsorption resistance, water wettability, oxygen permeability, and electrolyte permeability of the mechanically enhanced poly(MPC) hydrogel crosslinked with MMPC. The amount of protein adsorbed on this hydrogel was 0.9 microg/cm(2), which accounted for 30% of Omafilcon A and 3% of Etafilcon A. Water contact angle experiments revealed the high wettability of the poly(MPC) hydrogels. The oxygen permeability and NaCl diffusion constant of the poly(MPC) hydrogels were 64 barrer and 48 x 10(-6) cm(2)/s, respectively. This high permeability resulted from the high water content, similar to the case of the human cornea. These results suggested that poly(MPC) hydrogels have good potential for use in ophthalmologic biomaterials.     

Morphologies of fibroblast cells cultured on surfaces of PHB films implanted by hydroxyl ions

Polyhydroxybutyrate (PHB) films were implanted with 40 keV hydroxyl ions with fluences ranging from 1 x 10(12) to 1 x 10(15) ions/cm2, respectively. The as-implanted PHB films were characterized by scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA) and water contact angle measurements. The surface structures and properties of the as-implanted PHB films were closely related with hydroxyl ion fluence. They were further investigated by inoculating 3T6 fibroblasts cells on their surfaces. Morphologies of the 3T6 fibroblast cells cultured on surfaces of the as-implanted PHB films were observed by SEM. Characterization of the cultural 3T6 cells was analyzed qualitatively. The preliminary experimental results reveal that the bioactivity of the PHB films modified by hydroxyl ion implantation was improved at different levels, and the fluence of 1 x 10(13) ions/cm2 is optimal for PHB film.     

Non-biofouling materials prepared by atom transfer radical polymerization grafting of 2-methacryloloxyethyl phosphorylcholine: separate effects of graft density and chain length on protein repulsion

Biomimetic poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) brushes with graft density 0.06-0.39 chains/nm2 and chain length 5-200 monomer units were prepared from silicon wafer surfaces by combining self-assembly of initiator and surface-initiated atom transfer radical polymerization (ATRP). Water contact angle, X-ray photoelectron spectroscopy, and atomic force microscopy were used to characterize the modified surfaces. These surfaces with well-controlled poly(MPC) brushes were tested for protein repelling performance. Fibrinogen adsorption from tris-buffered saline at pH 7.4 decreased significantly with increasing graft density and/or chain length of poly(MPC) and reached a level of < 10 ng/cm2 at graft density > or = 0.29 chains/nm2 and chain length > or = 100 units, compared to ca. 570 ng/cm2 for the unmodified samples. While the fibrinogen adsorption was determined by both graft density and chain length, it showed a stronger dependence on graft density than on chain length.     

Correlation of proliferation, morphology and biological responses of fibroblasts on LDPE with different surface wettability

In order to find a correlation between cell adhesion, growth and biological response with different wettability, NIH/3T3 fibroblast cells were cultured on plasma-treated low-density polyethylene (LDPE) film generated with radio frequency. Different surface wettabilities (water contact angle 90-40 degrees ) were created by varying the duration of plasma treatment between 0 and 15 s, respectively. Growth and proliferation rate of cells on LDPE surfaces was evaluated by MTT assay, and cell morphology, by means of spreading and adhesion, was characterized by scanning electron microscopy (SEM). The expression of particular genes in cells contacted on films with different wettability was analyzed by RT-PCR. Using the MTT assay, we confirmed that the amount of cell adhesion was higher on surface of film with a water contact angle of 60 degrees than with other water contact angle. Also, the proliferation rate of cells was highest with a water contact angle of 60 degrees . It was confirmed by SEM that the morphology of cells adhered with a water contact angle of 50-60 degrees was more flattened and activated than on other surfaces. Furthermore, c-fos mRNA in cells showed maximum expression on the film with contact angle range of 50-60 degrees and c-myc mRNA expressed highly on the film with a contact angle of 50 degrees . Finally, p53 gene expression increased as wettability increase. These results indicate that a water contact angle of the polymer surfaces of 50-60 degrees was suitable for cell adhesion and growth, as well as biological responses, and the surface properties play an important role for the morphology of adhesion, growth and differentiation of cells.     

Selective adsorption of metal ions on poly(4-vinylpyridine) resins in which the ligand chain is immobilized by crosslinking

Chelate forming resins ( 3 ) were prepared by crosslinking poly(4-vinylpyridine) ( 1 ) with 1,4-dibromobutane ( 2 ) and their complexation with metal ions was studied. Stability constants (K) were found to be much higher for the Cu- 3 system than for the Cu- 1 system, which indicates that 3 uptakes Cu ions with high efficiency. K and the adsorption capacity of Cu decrease largely with increasing degree of crosslinking. Visible and ESR spectra of Cu- 3 show that the structure of the Cu complex within 3 is the same as that of the monomeric Cu-pyridine complex. However, the ligand-chain is immobilized in the highly crosslinked 3c and 3d , so that the square planar structure of a stable Cu complex is distorted. The amount of adsorption of Cu, Fe, Cr, Ni, and Zn ions on 3 decreases with the crosslinking, but the adsorption of Hg ions is independent; i.e. 3d selectively adsorbs Hg ions. Metal complexed 1 was crosslinked according to Scheme 1 and the metal ion which was used as template is well adsorbed by the obtained 3 . It is considered, therefore, that the ligand chain is maintained at the best conformation for the template ion.     

Corrosion and wear-corrosion behavior of NiTi modified by plasma source ion implantation

The understanding of corrosion behavior in NiTi is critical for the devices using this shape-memory alloy. In order to improve the surface properties of NiTi such as corrosion resistance, plasma source ion implantation (PSII) technique was employed with oxygen as incident ions at three levels of implantation dose (5x10(16), 1x10(17) and 3x10(17) ions/cm(-2)). Pitting corrosion and wear-corrosion behavior of control and PSII-modified Ti-50.7at% Ni alloy were evaluated by cyclic potentiodynamic polarization and wear-corrosion measurements. Surface characterization was used to interpret the different corrosion behavior observed between control and oxygen-implanted samples. Results showed that corrosion behavior was influenced by both heat treatment and surface modification. The best pitting corrosion resistance was observed for samples with Af=21 degrees C modified by oxygen implantation at a dose of 1x10(17) ions/cm(-2). Better wear-corrosion resistance was observed for oxygen-implanted samples.     

Surface modification of plastic, glass and titanium by photoimmobilization of polyethylene glycol for antibiofouling

Photoreactive poly(ethylene glycol) (PEG) was prepared and the polymer was photoimmobilized on organic, inorganic and metal surfaces to reduce their interaction with proteins and cells. The photoreactive PEG was synthesized by co-polymerization of methacrylate-PEG and acryloyl 4-azidobenzene. Surface modification was carried in the presence and the absence of a micropatterned photomask. It was then straightforward to confirm the immobilization using the micropatterning. Using the micropatterning method, immobilization of the photoreactive PEG on plastic (Thermanox™), glass and titanium was confirmed by time-of-flight secondary ion mass spectroscopy and atomic force microscopy observations. The contact angle on an unpatterned surface was measured. Although the original surfaces have different contact angles, the contact angle on PEG-immobilized surfaces was the same on all surfaces. This result demonstrated that the surface was completely covered with PEG by the photoimmobilization. To assess non-specific protein adsorption on the micropatterned surface, horseradish peroxidase (HRP)-conjugated proteins were adsorbed. Reduced protein adsorption was confirmed by vanishingly small staining of HRP substrates on the immobilized regions. COS-7 cells were cultured on the micropatterned surface. The cells did not adhere to the PEG-coated regions. In conclusion, photoreactive PEG was immobilized on various surfaces and tended to reduce interactions with proteins and cells.     

Recognition of lysozyme using surface imprinted bacterial cellulose nanofibers

Here, we developed the lysozyme imprinted bacterial cellulose (Lyz-MIP/BC) nanofibers via the surface imprinting strategy that was designed to recognize lysozyme. This study includes the molecular imprinting method onto the surface of bacterial cellulose nanofibers in the presence of lysozyme by metal ion coordination, as well as further characterizations methods FTIR, SEM and contact angle measurements. The maximum lysozyme adsorption capacity of Lyz-MIP/BC nanofibers was found to be 71 mg/g. The Lyz-MIP/BC nanofibers showed high selectivity for lysozyme towards bovine serum albumin and cytochrome c. Overall, the Lyz-MIP/BC nanofibers hold great potential for lysozyme recognition due to the high binding capacity, significant selectivity and excellent reusability.     

Roughness induced dynamic changes of wettability of acid etched titanium implant modifications

Dynamic contact angle analysis (DCA) was used to investigate time-dependent wettability changes of sandblasted and acid-etched commercially pure (cp) titanium (Ti) implant modifications during their initial contact with aqueous systems compared to a macrostructured reference surface. Surface topography was analyzed by scanning electron microscopy and by contact stylus profilometry. The microstructured Ti surfaces were found to be initially extremely hydrophobic. This hydrophobic configuration can shift to a completely wettable surface behavior with water contact angles of 0 degrees after the first emersion loop during DCA experiments. It is suggested that a hierarchically structured surface topography could be responsible for this unexpected wetting phenomenon. Roughness spatial and hybrid parameters could describe topographical features interfering with dynamic wettability significantly better than roughness height parameters. The Ti modifications which shift very sudden from a hydrophobic to a hydrophilic state adsorbed the highest amount of immunologically assayed fibronectin. The results suggest that microstructuring greatly influences both the dynamic wettability of Ti implant surfaces during the initial host contact and the initial biological response of plasma protein adsorption. The microstructured surfaces, once in the totally wettable configuration, may improve the initial contact with host tissue after implantation, due to the drastically increased hydrophilicity.     

Immobilization of a nonsteroidal antiinflammatory drug onto commercial segmented polyurethane surface to improve haemocompatibility properties

A method has been developed in which a layer of p-aminosalicylic acid (4-amino-2-hydroxybenzoic acid) (PAS), a water soluble pharmaceutical compound of the nonsteroidal anti-inflammatory drug (NSAID) class with antiaggregant platelet activity, is covalently immobilized onto a segmented polyurethane, Biospan (SPU) surface. Thus, SPU surfaces were modified by grafting of hexamethylenediisocyanate. and the free isocyanate remaining on the SPU surface were then coupled through a condensation reaction to amine groups of p-aminosalicylic acid. The bonding of PAS from aqueous solution onto SPU surface was studied by ATR-FTIR. UV and fluorescence spectroscopy. Plateau levels of coupled PAS were reached within 1.2 microg/cm2 using PAS solution concentrations of 1mg/ ml. The surface wettability of the polymeric films measured by contact angle indicate that the introduction of the PAS turns the surface more hydrophilic (theta(water) = 43.1 +/- 2.1) relatively to the original SPU films (theta(water) = 70.3 +/- 1.9). The in vitro albumin (BSA) adsorption shows that the PAS-SPU films adsorb more BSA (250/microgmm2) than the original SPU (112 microg mm2). Thrombogenicity was assessed by measuring the thrombus formation and platelet adhesion of the SPU containing PAS relatively to nonmodified SPU surfaces. The polymeric surfaces with immobilized PAS had better nonthrombogenic characteristics as indicated by the low platelet adhesion, high adsorption of albumin relatively to fibrinogen and low thrombus formation, making them potentially good candidates for biomedical applications.     

Improved wettability of an experimental silicone rubber denture soft lining material

The purpose of this study was to improve the wettability of an experimental silicone rubber soft lining material (Sildent) to increase patient comfort. Sildent was modified by the addition of polyalkylene oxide poly(dimethylsiloxane) surfactants. The various surfactants were added directly to the polymeric matrix in the quantities 5, 10, 20% w/w. The surfactants were also added to a one part silicone sealant, which was then painted onto the surface of already cured Sildent. Contact angle measurements were made on samples using a dynamic contact angle analyzer. Results showed that incorporation of surfactants A (Silwet L7600) and B (Silwet L7607) effectively improved the wettability of Sildent. This improvement was still evident after 6 months storage in distilled water at 37 degrees C suggesting retention of the surfactants matrix via physio-chemical bonding. Formulations with surfactants added directly to the matrix showed unacceptable water absorption after 2 months in distilled water. Samples with surfactant charged sealant painted on the surface showed a lower water absorption. In conclusion, Sildent formulations modified with polyalkylene silicone surfactants showed improved wettability compared to unmodified Sildent. Further work is needed to reduce water uptake and determine the effect on key mechanical properties.     

Silica coatings formed on noble dental casting alloy by the sol-gel dipping process.

The sol-gel dipping process, in which liquid silicon alkoxide is transformed into the solid silicon-oxygen network, can produce a thin film coating of silica (SiO2). The features of this method are high homogeneity and purity of the thin SiO2 film and a low sinter temperature, which are important in preparation of coating films that can protect from metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface characteristics of the dental casting silver-palladium-copper-gold (Ag-Pd-Cu-Au) alloy coated with a thin SiO2 film by the sol-gel dipping process. The SiO2 film bonded strongly (over 40 MPa) to Ti-implanted Ag-Pd-Cu-Au alloy substrate as demonstrated by a pull test. Hydrophobilization of Ti-implanted/SiO2-coated surfaces resulted in a significant increase of the contact angle of water (80.5 degrees) compared with that of the noncoated alloy specimens (59.3 degrees). Ti-implanted/SiO2-coated specimens showed the release of many fewer metallic ions (192 ppb/cm2) from the substrate than did noncoated specimens (2,089 ppb/cm2). The formation of a thin SiO2 film by the sol-gel dipping process on the surface of Ti-implanted Ag-Pd-Cu-Au alloy after casting clinically may be useful for minimizing the possibilities of the accumulation of dental plaque and metal allergies caused by intraoral metal restorations.     

Surface studies on copolymers having pendant monosaccharides

Copolymers having pendant monosaccharide groups were synthesized by copolymerizing 2-(glucosyloxy)ethyl methacrylate (GEMA, 1 ), with methyl methacrylate (MMA) or styrene (St). The surface characteristics of the copolymer films were investigated by means of contact angle measurements, X-ray photoelectron spectroscopy (XPS), and protein adsorption. The surface free energy of the GEMA/St copolymer films was constant in the range of a GEMA content from 10 mol-% to 60 mol-%. Insertion of GEMA of over 60 mol-%, however, caused an increase of the surface free energy of the copolymer films. The surface composition determined by means of XPS supported the result from surface free energy measurements. There was a significant difference between the GEMA/St and GEMA/MMA copolymer films in the effect of the GEMA content on the surface characteristics of the films. The differences could be explained on the basis of the sequence of monomeric units in each copolymer. Immersing the copolymer films in hot water made the copolymer surface more hydrophilic. This is because each component migrates to the surface or the bulk in order to minimize the surface free energy of the copolymer films. The introduction of GEMA to the copolymer suppressed fibrinogen adsorption onto the copolymer films.     

Boundary lubrication and maxillofacial prosthetic polydimethylsiloxanes

Polydimethylsiloxanes exhibit hydrophobic behaviour and poor wettability. These features impose some problems with the clinical performance of the material when used for the construction of intraoral and extraoral facial prostheses. Surface active agents were added to modify the surface energy of the polydimethylsiloxane and contact angle measurements were carried out to observe wetting characteristics. Five siloxane-alkene oxide block copolymers, one organosilicon quaternary ammonium chloride and an epoxyalkyl silane ester were used as surfactants. The best surfactant in terms of permanency and contact angle lowering achieved a value of 24 degrees when added at 10% level compared with 57 degrees for the unmodified silicone. The fairly high viscosity, combined with a comb-like structure, together with the high hydroxyl number of 75 provided the correct balance of permanence and wetting characteristics.     

Amphiphilic Block Copolymers with Pendent Sugar as Hydrophilic Segments and Their Surface Properties

The block copolymers of styrene ( St ) and 2,3;4,5‐diisopropylidene‐1‐(4‐vinylphenyl)‐D ‐gluco(D ‐manno)pentitol ( 1 ) were prepared by TEMPO‐mediated free‐radical polymerization. The polystyrene‐bearing TEMPO fragment at the chain end was used as the macromolecular initiator for 1 , and the poly1 ‐bearing TEMPO fragment at the chain end was used as the initiator for St . Corresponding amphiphilic block copolymers were produced after removing isopropylidene by treating the samples with trifluoroacetic acid and water (9/1, v/v). The surface properties of the cast films on silanized glass substrates from N,N‐dimethylformamide solutions were characterized by contact‐angle analysis. The results show that the surface properties of the as‐cast films are hydrophobic and became hydrophilic when the films were treated with hot water. This suggests that the structures of the outermost surface could be reorganized according the treating conditions. The relatively longer polystyrene segments in the copolymers seem to increase the ability of the domain to reconstruct. The adsorption of the novel amphiphilic block copolymers on a polystyrene plate was also studied by the contact‐angle method. It was found that the surface quickly became hydrophilic simply by spreading a low concentration of an aqueous solution of the copolymer on the substrate.     

Surface glycosylation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) membrane for selective adsorption of low-density lipoprotein

A novel method of constructing a glycosylated surface on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] membrane surface for the selective adsorption of low-density lipoprotein (LDL) was developed, which involved the photoinduced graft polymerization of acrylic acid followed by the chemical binding of carboxyl groups with glucosamine in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride and N-hydroxy-succinimide. The chemical structures of the fabricated membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Zeta potential and water contact angle measurements were performed to investigate the surface charge and wettability of the membranes, respectively. An enzyme linked immunosorbent assay was used to measure the LDL adsorption on the plain and modified membrane surfaces. It was found that the surface glycosylation of P(3HB-co-4HB) membrane greatly enhanced the affinity interactions with LDL and the absorbed LDL could be easily desorbed with eluents, indicating a specific and reversible binding of LDL to the surface. Furthermore, the hemocompatibility of glycosylated membrane was improved as examined by platelet adhesion. The results suggest that the glycosylated P(3HB-co-4HB) membrane is promising for application in LDL apheresis therapy.