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PubMed1998

Surface modifications for the development of piezoimmunosensors.

Four different techniques for the immobilisation of proteins onto the gold electrode of a piezoelectric quartz crystal were investigated. The examined techniques were adsorption, avidin-biotin binding and two different types of covalent binding on self-assembled monolayers (SAM), dithiobis(succinimidylpropionate) (DSP) and a dextran modified thiol monolayer. The reaction of the immobilised proteins (bovine serum albumin (BSA) and anti-human IgG) with their specific antibodies, anti-BSA and hIgG (50 and 200 micrograms/ml) were studied using a quartz crystal microbalance and then compared. Many cycles of measurements were performed on the same crystal regenerating the gold surface with a solution of glycine.HCl, 100 mM, pH 2.1. The interactions of the immobilised reagents with non-specific antibodies were also studied. The adsorption protocol was the quickest, but did not allow regeneration with glycine.HCl. Thiol-dextran coated surfaces did not show any detectable response to non-specific reagents, but needed a very long and complicated protocol. DSP and avidin-biotin coating procedures were easy and not too long. They seemed to have the best characteristics of reproducibility among different crystals and possibility of regeneration of the coated surface, but the percentage of non-specific binding was high.

Adsorption↗
PubMed2006

Surface modification of indium tin oxide via electrochemical reduction of aryldiazonium cations.

The facile deposition of para-substituted aryl films onto indium-tin oxide (ITO) electrodes by the electrochemical reduction of aryl diazonium salts in acetonitrile is reported. For the deposition conditions used in this report, the aryl film thicknesses are on the order of 1-6 nm, suggesting a multilayer structure. Regardless of the functional group on the aryl diazonium cation, (NO(2), CO(2)H, or fluorene) the electrodeposition behavior onto ITO electrodes is similar to that seen on other electrode materials. XPS and UV-vis data support the introduction of organic functional surface groups to ITO. The blocking behavior of the aryl films on ITO toward the Ru(NH(3))(6)(3+/2+) redox couple is in agreement with electron transfer through conjugated organic layers. The facile preparation of patterned aryl films with regular-spaced 700 nm voids on ITO is also described. Atomic force microscopy and scanning surface potential microscopy on patterned NO(2) aryl films are used to assess the molecular structure and orientation. A 100 mV decrease in the contact potential over NO(2) aryl films relative to bare ITO suggests that the aryl films are loosely structured as deposited with the NO(2) groups oriented at a small angle away from the ITO surface.

Diazonium Compounds↗
PubMed2004

Formation of Langmuir layers and surface modification using new upper-rim fully tethered bipyridinyl or bithiazolyl cyclodextrins and their fluorescent metal complexes.

Seven new amphiphilic cyclodextrins bearing bipyridyl or bithiazolyl moieties at the narrow rim and free hydroxyl or methoxyl groups at the wide rim of the cyclooctaamylose crown were synthesized using a one step "phosphine imide" approach. These ligands form metal complexes that have fluorescence properties with potentials for optical applications. Here, the cyclodextrin derivatives were used as probes for evaluating the role of different moieties in the self-assembly process, providing crucial information in creating functional devices. The behavior of these molecules and of complexes with EuIII in some cases was studied in Langmuir films using surface pressure (pi) and surface potential (deltaV) measurements performed as a function of film compression (compression isotherms). For chosen cyclodextrins, Brewster angle microscopy (BAM) in monolayers was performed. Films formed with derivatives 1, 3, 7, and 2compl were transferred on mica using the Langmuir-Blodgett technique. The properties of the films deposited on mica were analyzed with fluorimetry and, in the case of derivative 7, using fringe of equal chromatic order technique (FECO). The monolayer structure and the fluorescence properties of the Langmuir-Blodgett films indicate that the derivatives studied can be used for preparing cyclodextrin-based optical devices.

Cyclodextrins↗
PubMedDate not supplied

Improving the expansion and neuronal differentiation of mesenchymal stem cells through culture surface modification.

Poly-D-lysine, poly-L-lysine, collagen, laminin, fibronectin, and Matrigel were compared with standard tissue grade polystyrene for their impact on the expansion and neuronal differentiation of mesenchymal stem cells (MSCs). Among these substrates, adsorption of Matrigel at 5 microg/cm2 did not enhance cell proliferation but gave rise to the highest percentage of MSC-derived neuron-like cells with the best morphological differentiation. Matrigel at a higher coating density of 50 microg/cm2 not only further enhanced the differentiation but also significantly improved cell expansion. In contrast, poly-D-lysine did not effectively support the growth of MSCs. Hence the expansion and neuronal differentiation of MSCs both depend on surface properties of the culture substrate. These results could lead to a culture process with improved yield of MSC-derived neuron-like cells and to novel biomaterials for tissue engineering.

Cell Culture Techniques↗
PubMedDate not supplied

Surface modification of silicone intraocular implants to inhibit cell proliferation.

Photo-cross-linkable polymers bearing cinnamic, sulfonate, and carboxylate groups were synthesized by radical polymerization leading to randomly distributed copolymers. These polymers were used to coat silicone intraocular lenses in order to reduce posterior capsule opacification, also named "secondary cataract". We previously demonstrated that polymers containing both carboxylate and sulfonate groups inhibit cell proliferation, and formulations with the ratio R = COO-/(COO- + SO3-) equal to 0.64 provided the highest inhibitory effect. Ionic polymers with this formulation were synthesized to contain a monomer with pendant siloxane groups in order to get compatibility with the silicone matrix of the intraocular lenses. Anchorage of the ionic polymer at the surface of the silicone implant was achieved by a cycloaddition reaction of the photosensitive groups according to two options. These modified silicone surfaces grafted onto intraocular lenses were shown to inhibit cell proliferation to 60%.

Biocompatible Materials↗
PubMed1988

Surface modifications at the periosseous region of chick osteoclast as revealed by freeze-substitution.

Improved preservation of osteoclast fine structure can be achieved by quick freezing, freeze-substitution, or detergent extraction. With such techniques the ruffled border mainly contains a disorganized, interconnected meshwork of microfilaments (5-7 nm in diameter), whereas in the clear zone a few ordered arrays of intermediate-type filaments (10-12 nm in diameter) are detectable among the network of microfilaments. In well-frozen samples, well-preserved matrix may have occluded the cytoskeleton; detergent extraction permits visualization of the cytoskeletal components. In fresh-frozen cells an extracellular fuzzy coat overlays the ruffled border. At the site of attachment of the clear zone to the bone surface, extracellular cementing material is detected only after quick freezing. The superiority of quick freezing to preserve ultrastructure is shown in various cytoplasmic organelles. Most vesicles and vacuoles found close to the ruffled border seemed not to make contact with the extracellular matrix. Anhydrous procedures using quick freezing and freeze-substitution stabilize bone mineral in some vacuoles and in the channels of the ruffled border.

Animals↗
PubMed2006

Vascular prostheses with controlled release of antibiotics Part 1: Surface modification with cyclodextrins of PET prostheses.

Vascular prostheses were functionalised with the aim to obtain a slow release of antibiotics in order to reduce postoperative infections. The original process that we present in this paper is based on the use of a family of cage molecules named cyclodextrins (CD). These compounds have the ability to form reversible inclusion complexes with drugs such as antibiotics. The aim of this work was to graft CD onto the prosthesis, so that an antibiotic can be bound on it by this inclusion phenomenon, and then be progressively released over a prolonged period by a complex dissociation mechanism. This paper presents the first part of this research program and concerns mainly the study of the functionalization parameters. It presents surface characterization results of the modified prostheses. The PET prostheses were immersed into a solution containing a cross linking agent, cyclodextrins (beta-CD, gamma-CD, HP-beta-CD and HP-gamma-CD) and a catalyst and were padded. Grafting occurred by the mean of a thermofixation step at a temperature comprised between 140 and 180 degrees C. It was observed that the support was permanently modified when the CD polymer that coated the fibres resisted to the final washing process. Grafting rates of 12 wt% in CD polymer could be reached. It was also observed that the fibre coating reaction induced an increase of the permeability of the grafts.

Anti-Bacterial Agents↗
PubMed2004

Surface modification and characterization of chitosan film blended with poly-L-lysine.

Biodegradable nerve guidance conduits (NGCs) represent a promising alternative to current clinical nerve repair procedures. Chitosan, a natural polysaccharide that has excellent biocompatibility and biodegradability, can be used as a nerve conduit material. The purpose of this work was to study the nerve cell affinity of chitosan modified by blending with different content of poly-L-lysine. PC12 cells culture was used to evaluate the nerve cell affinity of the chitosan-poly-L-lysine composite materials. The results showed that composite materials had significantly improved nerve cell affinity compared to chitosan as indicated by increased attachment, differentiation, and growth of nerve cells. The improved nerve cell affinity might be due to both the increased surface charge and hydrophilicity of composite materials. Composite material with 3 wt% poly-L-lysine content (PL-3) is an even better material in nerve cell affinity than collagen, suggesting that poly-L-lysine-blended chitosan is a promising candidate material for nerve regeneration.

Animals↗
PubMed2004

Increased resistance of DNA lipoplexes to protein binding in vitro by surface-modification with a multivalent hydrophilic polymer.

The potential of cationic liposomes as DNA delivery vehicles for gene therapy is significantly limited by their instability upon systemic administration. Their strong positive charge induces non-specific binding of serum proteins and subsequent clearance from the circulation. This work investigates the ability of the multivalent reactive copolymer of poly[N-(2-hydroxypropopyl) methacrylamide], pHPMA (MA-GG-ONp) to shield lipoplexes from non-specific protein binding. The polymer was found to react with cationic liposome-DNA complexes (lipoplexes) in both an electrostatic and covalent manner to form an external polymer coat. Polymer coating resulted in an increase in lipoplex diameter (by up to 100 nm) that was proportional to the amount of polymer used, with a concomitant reduction in surface charge from strongly positive to neutral (from 30 to 0 mV). Polymer-coated lipoplexes exhibited increased stability to protein binding compared to untreated liposomes and reduced non-specific uptake into cells in vitro.

Cell Line, Tumor↗
PubMed2005

Control of moisture at buried polymer/alumina interfaces through substrate surface modification.

Moisture absorption in poly(4-tert-butoxycarbonyloxystyrene) (PBOCSt) films supported on Al(2)O(3) sputter coated silicon wafers is measured using neutron and X-ray reflectivity. Accumulation of water at the interface during moisture exposure results in an apparent film-thickness-dependent swelling for ultrathin PBOCSt films. The swelling of a film on Al(2)O(3) is less than the swelling of a film of the same thickness on SiO(x) for films thinner than 20 nm. This is due to comparatively less moisture accumulation at the Al(2)O(3)/PBOCSt interface. A simple, zero adjustable parameter model consisting of a fixed water-rich layer at the interface and bulk swelling through the remainder of the film describes the thickness-dependent swelling quantitatively. The influence of four different Al(2)O(3) surface treatments on the moisture distribution within PBOCSt films was examined: bare Al(2)O(3), tert-butylphosphonic acid, phenylphosphonic acid, and n-octyltrichlorosilane. Both the phenyl and the octyl surface treatments reduce the accumulation of water at the polymer/substrate interface. The tert-butyl treatment does not reduce the interfacial water concentration, presumably due to insufficient surface coverage.

Journal Article↗
PubMed2004

Surface modification of oxidic nanoparticles using 3-methacryloxypropyltrimethoxysilane.

Tin oxide, antimony-doped tin oxide (ATO), and silica nanosized particles in aqueous dispersion were reacted with various amounts of 3-methacryloxypropyltrimethoxysilane (MPS). The kinetics were followed by 29Si NMR and the products were analyzed by FTIR and 29Si NMR. The kinetic experiments on ATO and silica revealed that the hydrolysis is the rate-determining step in these reactions. The reaction of MPS with the particles is favored over the homocondensation of MPS. Quantitative analysis using FTIR revealed that the amount of MPS grafted onto the tin oxide and silica particles is limited to the amount needed to fill one monolayer. For ATO the maximum amount of grafted MPS was only 50-70% of the amount that is needed for a closed monolayer. The MPS molecules are for the most part oriented parallel to the oxide surface, and a hydrogen bond between the MPS-carbonyl and the oxide is formed.

Journal Article↗
PubMed2002

Surface modification without desorption: recycling of Cl on Si(100)-(2 x 1).

We demonstrate chlorine-induced modification of Si(100)-(2 x 1) under conditions where Cl is recycled rather than desorbed as SiCl2. A dimer with 2 Cl atoms, 2SiCl, converts to SiCl2+Si, allowing the bare Si atom to escape onto the terrace. At temperatures below the desorption threshold, the SiCl2 unit decays through Cl diffusion, allowing the second Si atom to escape. The result is a dimer vacancy, terrace regrowth structures, and Cl that is able to participate in another pitting event. Access to this unexpected roughening pathway is controlled by the Cl concentration and temperature. This previously overlooked process represents an important component of Si(100) surface processing.

Journal Article↗
PubMed2003

Novel core(polyester)-shell(polysaccharide) nanoparticles: protein loading and surface modification with lectins.

This study describes new lectin-decorated or protein-loaded nanoparticles with a hydrophobic poly(epsilon-caprolactone) (PCL) core and a hydrophilic dextran (Dex) corona. In this view, a family of block Dex-PCLn copolymers was first synthesized, consisting of a Dex backbone to which n preformed PCL blocks were grafted. The ability of these new copolymers to form nanoparticles was evaluated in comparison with a series of PCL homopolymers of various molecular weights (2000, 10,000 and 40,000 g/mole). Two different nanoparticle preparation methods have been developed and tested for their efficacy to incorporate proteins. For this, three proteins were used: a model protein, bovine serum albumin (BSA), a lectin from leaves of Bauhinia monandra (BmoLL) and Lens culinaris (LC) lectin. All these proteins were successfully incorporated in nanoparticles with a mean diameter around 200 nm. Lectins could also be adsorbed onto the surface of Dex-PCLn nanoparticles. Surface-bound BmoLL conserved its hemagglutinating activity, suggesting the possible application of this type of surface-modified nanoparticles for targeted oral administration. Caco-2 cellular viability was higher than 70% when put in contact with Dex-PCLn nanoparticles, even at concentrations as high as 660 microg/ml.

Animals↗
PubMed2000

Surface-modification of polystyrene-microtitre plates via grafting of glycidylmethacrylate and coating of poly-glycidylmethacrylate.

Photografting of glycidylmethacrylate (GMA) onto commercially available polystyrene-microtitre plates was carried out in methanol as well as butanol with benzophenone (BP) as photoinitiator. Alternatively, prepolymers of polyglycidylmethacrylate (PGMA) were synthesized in methanol with azo-iso-butyrodinitrile (AIBN) as initiator and dip-coated onto polystyrene-microtitre plates. Both modification methods were tested in order to reach a high binding capacity for proteins. Peroxidase was used as model protein. In addition, the immobilization of myelin basic protein (MBP) to epoxy-modified microtitre plates is shown and a MBP-based ELISA has been developed.

Biocompatible Materials↗
PubMed2001

The inhibitory mechanism of gap junctional intercellular communication induced by polyethylene and the restorative effects by surface modification with various proteins.

Gap junctional intercellular communication (GJIC) is a function that plays an important role in maintaining cell and tissue homeostasis and in regulating cell growth, development, and differentiation. Change in this function of V79 fibroblasts cultured on polyethylene films modified with albumin or collagen was estimated using fluorescence redistribution after photobleaching (FRAP) analysis. The GJIC function of V79 cells on nontreated polyethylene was strongly inhibited in comparison with those on a glass coverslip. When the cells were culture on collagen-immobilized polyethylene film, this function was recovered to about 70% of the cells cultured on the coverslip. However, albumin immobilization did not recover the function as much as collagen immobilization. Western blotting analysis and immunostaining of connexin 43, which is a major protein constituting gap junctional channel of these cells, revealed its abnormal expression and distribution in the cells on nontreated polyethylene, whereas its almost normal distribution was observed in the cells on collagen-immobilized polyethylene. This abnormal expression and distribution of connexin 43 induced by the surface of polyethylene may be ascribed to a strong inhibition of GJIC of V79 fibroblasts.

Albumins↗
PubMed1996

Surface modification of titanium based biomaterials by ion beam.

Ion beam enhanced deposition (IBED) was adopted to synthesize biocompatible titanium oxide film. Structure characteristics of titanium oxide film were investigated by RBS, AES, and XRD. The blood compatibility of the titanium oxide film was studied by measurements of blood clotting time and platelet adhesion. The results show that the anticoagulation property of titanium oxide film is improved significantly. The mechanism of anticoagulation of the titanium oxide film was discussed.

Animals↗