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Results for “surface modification”

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PubMed2006

Mineralization of hydroxyapatite in electrospun nanofibrous poly(L-lactic acid) scaffolds.

A highly porous electrospun poly(L-lactic acid) (PLLA) nanofibrous scaffold was used as a matrix for mineralization of hydroxyapatite. The mineralization process could be initiated by immersing the electrospun scaffold in the simulated body fluids (SBF) at 37 degrees C for varying periods of time. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), wide-angle X-ray diffraction (WAXD), Fourier transform infrared (FTIR), and Raman spectroscopy were used to characterize the composition and the structure of the deposited mineral on the nanofiber surface. Results indicated that the mineral phase was a carbonated apatite with thin flake-like nanostructures. The effects of functional groups on the scaffold surface and anionic additives in the incubation fluids on the nucleation and growth of the mineral were investigated. It was found that a minuscule amount of anionic additives (e.g., citric acid and poly-L-aspartic acid) in the SBF could effectively inhibit the mineral growth. Surface modification of the scaffold was carried out by hydrolysis of PLLA scaffold in NaOH aqueous solution, where carboxylic acid groups were produced without compromising the scaffold integrity. The mineralization process from modified PLLA electrospun scaffolds was significantly enhanced because the calcium ions can bind to the carboxylate groups on the fiber surface.

Anions↗

PubMed1982

Cell-surface remodelling during mammalian erythropoiesis.

Current evidence suggests that the major cell-surface modification occurring during mammalian erythropoiesis could be generated by two separate mechanisms: either selective loss of membrane proteins during enucleation or endocytosis at the subsequent reticulocyte and erythrocyte stages. The former idea was tested by collecting developing rabbit erythroid cells before and after the enucleation step and comparing their cell-surface protein composition via radiolabelling and electrophoresis. Few changes were observed. Our data thus lend support to the endocytosis mechanism.

Animals↗

PubMed1985

Surface changes in chimpanzee sperm during epididymal transit.

Intact chimpanzee caput and cauda epididymal sperm, sperm cell lysates, and caput and cauda epididymal fluid were radiolabeled by enzymatic iodination with lactoperoxidase and Na125 I and were compared by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Caput epididymal sperm showed nine labeled macromolecular components of 90, 64, 56, 48, 38, 31, 20, 18 and 16 Kd and cauda epididymal sperm showed eleven macromolecular components of 90, 64, 55, 47, 42, 33, 27, 18, 17, 15 and 11 Kd. Six of the components labeled on caput sperm (90, 64, 56, 48, 18 and 16 Kd) were detected in equal amounts of cauda sperm and two (38 and 20 Kd) were detected at greatly reduced labeling intensities. In the cauda epididymidis, four new components (33, 27, 17 and 11 Kd) became prominent features of the sperm surface. Analysis of labeled caput and cauda sperm cell lysates resolved components distinct from those detected on sperm surfaces. Electrophoresis of caput epididymal fluid showed five labeled components of 66, 56, 47, 41 and 37 Kd, while electrophoresis of cauda epididymal fluid showed eight labeled components of 92, 66, 56, 48, 31, 27, 24 and 11 Kd. Three components (66, 56 and 47 Kd) were present in both caput and cauda fluid, two (41 and 37 Kd) in caput fluid only, and five (92, 31, 27, 24 and 11 Kd) in cauda fluid only. Components of 37 Kd were labeled in caput fluid and on caput sperm but not on cauda sperm, whereas components of 27 Kd and 11 Kd were labeled in cauda fluid and on cauda sperm but not on caput sperm. These data show that chimpanzee sperm undergo extensive surface modifications during epididymal maturation and that some of these modifications may be related to exogenous proteins/glycoproteins in epididymal fluids.

Animals↗

PubMedDate not supplied

Evaluation of a new heparin bonding process in prolonged extracorporeal membrane oxygenation.

A novel heparin bonding method has been developed for in situ surface modification using ozone oxidation, and evaluated in vitro and in vivo during prolonged extracorporeal membrane oxygenation (ECMO) experiments. The ECMO system consisted of a Capiox hollow fiber membrane oxygenator (MO; Terumo Corp., Tokyo, Japan) with an integral heat exchanger, a Capiox centrifugal pump (CP), and an extracorporeal circuit. The blood contacting surfaces of the system were completely modified using the heparin bonding process, and evaluated in a chronic sheep model for extended period of time, ranging from 96 to 168 hr, under minimal systemic heparinization. The heparin bonded surface was able to maintain high levels of heparin bioactivity, and showed improved blood compatibility in in vitro epifluorescent video microscopy experiments by suppressing platelet adhesion/activation and complement activation. For the ECMO experiments, extracorporeal blood flow was maintained at 3 L/min and the activated clotting time was maintained at 150 sec. There was no significant change in the gas transfer capability or mean pressure drop across the MO over experimental times of up to 168 hr. Platelet count and other coagulation parameters remained stable within the physiologic range throughout the experiment. There were no detectable thrombi in the CP, tubing, or connectors in the test circuit. Local thrombus formation was noted in a stagnant area of the MO, although this did not interfere with its function or lead to any significant embolization. Based on these results, the heparin bonded ECMO system appears to be a safe and effective device for prolonged extracorporeal circulation under minimal systemic heparinization.

Animals↗

PubMed2003

Selective detection of copper ions in aqueous solution based on an evanescent wave infrared absorption spectroscopic method.

A new infrared sensing scheme based on an evanescent wave was proposed in this work for selective detection of copper ion in aqueous solutions. This sensing scheme is based on the band-shifting technique to overcome the limitation that metal ions do not absorb IR radiation. To demonstrate that the proposed mechanism is feasible, both theoretical considerations and practical examination of copper ions in aqueous solutions were investigated. The IR sensor was constructed by surface modification with L-(-)proline to selectively interact with copper ions by formation of stable square-planar complexes. After complexation, the absorption bands of the immobilized L-(-)proline exhibits a band shift and could be used to monitor the quantity of metal ions in aqueous solutions. To immobilize L-(-)proline on the surface of a sensing element and increase the stability of the modified phase in aqueous solutions, poly(vinylbenzyl chloride) was coated onto the sensing element for further immobilization of L-(-)proline. A sensitive and a water-stable L-(-)proline phase was obtained. This sensing phase is selective and sensitive to copper ions due to the large formation constant between the copper ions and L-(-)proline. Factors, such as the copper ion concentration, response time, solution pH, long-term stability, regeneration efficiency, and the matrix effect, were investigated. Results indicated that the pH effect was significant but could be controlled by buffering the sample solutions. Using the optimal conditions found in this work, the detection limit could be lower than 0.7 microM and the linear regression coefficients in standard curves could be higher than 0.99 for a concentration range from 5 to 200 microM.

Copper↗

PubMed2005

Effect of supporting surface layers on catalytic activities of gold nanoparticles in CO oxidation.

The surfaces of fumed silica materials were modified with a surface sol-gel process for catalysis applications. This surface-modification approach allows not only a monolayer growth of TiO(2) or Al(2)O(3) but also a stepwise double-layer growth of TiO(2)/TiO(2), Al(2)O(3)/Al(2)O(3), TiO(2)/Al(2)O(3), or Al(2)O(3)/TiO(2) on the surfaces of the silica materials with a monolayer precision. XRD analyses revealed that the coated monolayers and double layers of TiO(2) and Al(2)O(3) were amorphous. Gold nanoparticles were successfully deposited on the above six surface-modified silica materials via a deposition-precipitation method. The catalytic activities of these six gold catalysts for CO oxidation are highly dependent on the structures of their surface monolayers or double layers. The gold catalyst supported on the silica material functionalized with a TiO(2) monolayer (Au/TiO(2)) is the most active in both as-synthesized and oxidized forms, while the gold catalyst supported on the silica material functionalized with an Al(2)O(3)/TiO(2) double layer (Au/Al(2)O(3)/TiO(2)/SiO(2)) is the most active in the reduced form among the six catalysts. Surprisingly, the gold catalyst supported on the silica material functionalized with a TiO(2)/Al(2)O(3) double layer (Au/TiO(2)/Al(2)O(3)/SiO(2)) has much less activity than Au/Al(2)O(3)/TiO(2)/SiO(2) under all various treatments, underscoring the sensitivity of the catalytic activity to the structure of the supporting surfaces.

Journal Article↗

PubMed2005

Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications.

Superparamagnetic iron oxide nanoparticles (SPION) with appropriate surface chemistry have been widely used experimentally for numerous in vivo applications such as magnetic resonance imaging contrast enhancement, tissue repair, immunoassay, detoxification of biological fluids, hyperthermia, drug delivery and in cell separation, etc. All these biomedical and bioengineering applications require that these nanoparticles have high magnetization values and size smaller than 100 nm with overall narrow particle size distribution, so that the particles have uniform physical and chemical properties. In addition, these applications need special surface coating of the magnetic particles, which has to be not only non-toxic and biocompatible but also allow a targetable delivery with particle localization in a specific area. To this end, most work in this field has been done in improving the biocompatibility of the materials, but only a few scientific investigations and developments have been carried out in improving the quality of magnetic particles, their size distribution, their shape and surface in addition to characterizing them to get a protocol for the quality control of these particles. Nature of surface coatings and their subsequent geometric arrangement on the nanoparticles determine not only the overall size of the colloid but also play a significant role in biokinetics and biodistribution of nanoparticles in the body. The types of specific coating, or derivatization, for these nanoparticles depend on the end application and should be chosen by keeping a particular application in mind, whether it be aimed at inflammation response or anti-cancer agents. Magnetic nanoparticles can bind to drugs, proteins, enzymes, antibodies, or nucleotides and can be directed to an organ, tissue, or tumour using an external magnetic field or can be heated in alternating magnetic fields for use in hyperthermia. This review discusses the synthetic chemistry, fluid stabilization and surface modification of superparamagnetic iron oxide nanoparticles, as well as their use for above biomedical applications.

Animals↗

PubMed2005

Immune complement activation on polystyrene and silicon dioxide surfaces. Impact of reversible IgG adsorption.

We have studied aspects of the molecular background to immune complement activation on solid surfaces. Quartz crystal microbalance with dissipation monitoring (QCM-D) sensor surfaces were modified by means of spin coating with polystyrene (PS) or sputtering of silicon dioxide (SiO2). The IC activation on modified QCM-D surfaces was investigated by incubation in serum, followed by determinations of the amounts of bound C3 fragments (C3c) at the surface. Determinations of soluble C3a and soluble C5b-9 complex (sC5b-9) were made with enzyme immunoassay (EIA) method. We found that IC activation was high on PS surfaces, independent of the method used for measurements. On the SiO2 surfaces, IC activation was generally lower, but still detectable with anti-C3c as well as sC5b-9 and C3a determinations. Pre-coating the surfaces with a layer of IgG resulted in that IC activation became very high on PS surface, while the IC response remained low on SiO2 surfaces. The lower level of IC activation on the SiO2 surfaces was explained by a low surface concentration of IgG as measured with QCM-D. This was a result of the high reversibility of the IgG protein adsorption as well as absence of sufficient conformational changes of adsorbed IgG molecules. The QCM-D method was as sensitive as the C3a and sC5b-9 determinations to reveal surface associated IC-activation on these model surfaces. Additional advantages of the QCM-D method are the broad dynamic measurement window, i.e. the high precision and the ability to perform time resolved measurements and the ease of making different surface modifications.

Adsorption↗

PubMed1999

Biofilm formation in vivo on perfluoro-alkylsiloxane-modified voice prostheses.

OBJECTIVE: To study the influence of perfluoroalkylsiloxane (PA) surface modification of silicone rubber voice prostheses on biofouling. DESIGN: Placebo-controlled clinical trial. SETTING: Tertiary referral center, with specialization in head and neck cancer treatment. PATIENTS: Eighteen consecutive patients with laryngectomies and experienced in the use of a voice prosthesis who visited the outpatient clinic for prosthesis replacement. MATERIAL: Eighteen partially surface-modified voice prostheses (3 with short-chain PAs [1 fluorocarbon unit] and 15 with long-chain PAs [8 fluorocarbon units]) were inserted via the patients' tracheoesophageal shunts and remained in place for 2 to 8 weeks. INTERVENTION: Replacement of the prostheses. MAIN OUTCOME MEASURES: Evaluation of biofilm formation on short- and long-chain PA-modified and original silicone rubber surfaces on the esophageal side of the voice prosthesis. RESULTS: The planimetrical biofilm scores of the surfaces of all 3 short-chain PA-treated voice prostheses indicated more biofouling on the treated surfaces than on the untreated surfaces of the same prostheses. For the long-chain PA-treated prostheses, the planimetrical biofilm scores, as well as the numbers of colony-forming units per cm(-2) for bacteria and yeasts, indicated less biofouling on the treated side than on the control side for 9 of the 13 prostheses that could be analyzed (2 were lost to analysis). Identical fungal strains, mainly Candida sp, were isolated from biofilms on each side of the esophageal flange. CONCLUSIONS: Chemisorption of long-chain PAs by the silicone rubber used for voice prostheses reduces biofilm formation in vivo and therefore can be expected to prolong the life of these prostheses. Chemisorption of short-chain PAs by silicone rubber seems to have an adverse effect.

Biofilms↗

PubMed1989

Mineral phases of calcium phosphate.

Many studies of calcium phosphate precipitation have been made using relaxation techniques in which the concentrations of the lattice ions are allowed to decrease as equilibrium is approached. Since the nature of the phases that form depend markedly on the solution composition, this decrease can lead to concomitant phase transformations during the crystallization experiments. The results of the present constant composition (CC) studies show that defect apatites may be formed under conditions of sustained supersaturation with a non-stoichiometric coefficient dependent on the pH of the growth medium. An important factor in analyzing these experiments is the initial surface modification and ion-exchange processes involving H+ and Ca2+ ions after inoculation of the supersaturated solutions. Thereafter, active growth sites may be eliminated as the crystals undergo lattice perfection. Transformation of dicalcium phosphate dihydrate to octacalcium phosphate, involving dissolution and subsequent nucleation and growth of the new phase, is also influenced by surface roughening of the initial phase. Typical inhibitors that reduce the rate of growth of seed crystals in supersaturated solutions may actually induce the nucleation of calcium phosphate phases when immobilized on inert surfaces. This may be a factor in the modulation of crystal growth in many biological systems.

Calcium Phosphates↗

PubMed2003

Porous PEOT/PBT scaffolds for bone tissue engineering: preparation, characterization, and in vitro bone marrow cell culturing.

The preparation, characterization, and in vitro bone marrow cell culturing on porous PEOT/PBT copolymer scaffolds are described. These scaffolds are meant for use in bone tissue engineering. Previous research has shown that PEOT/PBT copolymers showed in vivo degradation, calcification, and bone bonding. Despite this, several of these copolymers do not support bone marrow cell growth in vitro. Surface modification, such as gas-plasma treatment, is needed to improve the in vitro cell attachment. Porous structures were prepared using a freeze-drying and a salt-leaching technique, the latter one resulting in highly porous interconnected structures of large pore size. Gas-plasma treatment with CO(2) generated a surface throughout the entire structure that enabled bone marrow cells to attach. The amount of DNA was determined as a measure for the amount of cells present on the scaffolds. No significant effect of pore size on the amount of DNA present was seen for scaffolds with pore sizes between 250-1000 microm. Light microscopy data showed cells in the center of the scaffolds, more cells were observed in the scaffolds of 425-500 microm and 500-710 microm pore size compared to the ones with 250-425 microm and 710-1000 microm pores.

Alkaline Phosphatase↗

PubMed2001

Immobilization of bisphosphonates on surface modified titanium.

The efficiency of surface modifications on the immobilization of bisphosphonates on titanium was investigated with Ca-ion implantation and thin hydroxyapatite coatings. The ALP activity of osteoblastic cells and the inhibitory effects on the initial adherence of P. gingivalis were also evaluated using bisphosphonate-immobilized titanium. X-ray photoelectron spectroscopy analysis suggested that titanium surfaces modified with Ca-ion implantation and thin hydroxyapatite coatings caused the immobilization of bisphosphonate on titanium plates. The ALP activity of osteoblastic cells cultured on plates immobilized with bisphosphonate was almost the same as that of cells cultured on titanium plates, indicating that the bisphosphonate-immobilization showed no toxic effect on osteoblastic cells, and that it provides a favorable micro-environment with osteogenetic ability. Data of the adherence of oral bacteria showed that a bisphosphonate-immobilized titanium surface inhibited the initial adherence of P. gingivalis. These results indicate that the immobilization of bisphosphonates on titanium modified with Ca-ion implantation and thin hydroxyapatite coatings are useful for dental implants.

Animals↗

PubMed2003

Bone formation after 4 weeks around blood-plasma-modified titanium implants with varying surface topographies: an in vivo study.

The aim of the present study was to investigate and compare the stability and bone ingrowth capacity to screw-shaped titanium implants with five different surface treatments. The implants were: (1) standard turned with a thin blood plasma coat (TP), (2) NaOH-etched dito with pore size 0.2-0.3 microm (E), (3) NaOH-etched with pore size 0.2-0.3 microm and a thin blood plasma coat (EP), (4) electrochemically oxidised with pore size 1-2 microm (O), (5) electrochemically oxidised with pore size 1-2 microm and a thin blood plasma coat (OP). A total of 66 implants were divided into the above-described five groups and inserted for 4 weeks into tibia and femur of 11 rabbits. The implants were evaluated by resonance frequency (RF) measurements at the time of insertion and removal, and analysed histomorphometrically at removal. The RF measurements showed that the implant stability was lower in soft bone compared to dense and increased with time. No significant differences were observed between the different surface modifications. The histomorphometric analysis revealed no statistically significant differences between the implants regarding bone-to-metal contact (BMC) and bone area inside the threads (BA). The above results indicate that thin blood plasma-coated and non-coated screw-shaped titanium implants with turned, NaOH-etched and electrochemically etched surface profiles integrate similarly to bone at 1 month of implantation.

Bone Development↗

PubMed2003

Acid pretreatment of titanium implants.

The purpose of this study was to evaluate the effectiveness of several methods of cleaning titanium surfaces as pretreatment for surface modifications by analyzing the chemical interaction of three acids, such as Na(2)S(2)O(8),H(2)SO(4) and HCl, followed by rinsing with acetone or ultrapure water. Chemical evaluation, using X-ray photoelectron spectroscopy (XPS), and mechanical evaluation, using nanoindentation, were employed. XPS revealed that an untreated Ti surface consisted of carbon- and nitrogen-containing contaminant and titanium oxide layer on metallic titanium substrate. The method involving the combination of 10 N HCl and acetone was the most effective of all the methods investigated. Such a combination most effectively reduced values of contamination parameters C/Ti and N/Ti, as well as the intensity of the titanium oxide component in Ti 2p spectra. Chlorine was barely detected from the surface treated with HCl in any concentration. Sulfur from the residual S(2)O(8)(2-) or SO(4)(2-), however, was detected from the samples treated with either Na(2)S(2)O(8) or H(2)SO(4). The S/Ti values depended on concentration of the acidic solution. In addition, nanoindentation measurements revealed that Young's modulus of the surface treated with 0.1-10 N HCl was not significantly different from that of an untreated surface (p > 0.05). Consequently, the HCl/acetone treatment is proposed as an excellent decontamination method for the surface preparation process of Ti.

Acids↗

PubMed2005

Influence of antibody immobilization strategy on molecular recognition force microscopy measurements.

A systematic evaluation of the effects of antibody immobilization strategy on the binding efficiency and selectivity (e.g., ability to distinguish between specific and nonspecific interactions) of immunosurfaces prepared with F(ab') antibody fragments of rabbit Immunoglobulin G (IgG) is described. F(ab') was attached to gold surfaces either (1) directly via the formation of a gold-thiolate bond or (2) indirectly through a series of a bifunctional linkers containing an alkane chain or ethylene glycol spacer. Immobilization of F(ab') via the sulfhydryl reactive group located opposite the antigen binding site ensured optimum orientation of the antigen binding site. X-ray photoelectron spectroscopy (XPS) and surface plasmon resonance (SPR) were used to confirm surface modification with the bifunctional linkers and antibody immobilization, respectively. Binding efficiency assays performed with SPR indicated that increasing the length of the linker increased the antigen binding efficiency. Atomic force microscopy (AFM) adhesion force measurements indicated that AFM probes functionalized with directly immobilized F(ab') more effectively discriminated between specific and nonspecific surface-bound proteins than probes modified indirectly via linker-immobilized F(ab'). In addition, a greater number of antibody-antigen binding events were observed with directly immobilized F(ab')-functionalized probes.

Adhesiveness↗

PubMed1997

Nano-apatite/polymer composites: mechanical and physicochemical characteristics.

Hydrothermally synthesized acicular nano-apatite (Nap) was used as filler to make composites with a polyethylene glycol/poly(butylene terephthalate) (PEG/PBT) block copolymer (Polyactive 70:30). The Nap had a particle diameter of 9-25 nm and a length of 80-200 nm. The mechanical properties and the physiochemical characteristics of the composites, such as Young's modulus, swelling degree in water and the calcification behaviour, have been determined. It was found that Nap had a strong ability to promote the calcification of composites when incorporated into Polyactive 70:30, while poly(acrylic acid) (PAA) coating of Nap had an adverse effect on the calcification of composites, presumably due to the formation of complexes between PAA and PEG segments. Nap had a prominent stiffening effect for Polyactive 70:30 in the dry state, but had a poor stiffening effect for composites in an aqueous environment due to the hygroscopic nature and/or the formation of aggregates. PAA coating on Nap had almost no additional effect on the mechanical properties of composites either in the dry state or in an aqueous environment. To reinforce the polymer by Nap, achieving a more homogeneous dispersion of Nap in the polymer matrix and surface modifications to render the powders less hygroscopic appear to be necessary.

Acrylic Resins↗

PubMed2003

Tailor-made functional surfaces: potential elastomeric biomaterials I.

In the present investigation, different functional monomers, like hydroxyethyl methacrylate, acrylic acid, N-vinyl pyrrolidone and glycidyl methacrylate, have been grafted onto the surface of EPDM film (approx. 200 microm) using simultaneous photo-grafting (lambda > or = 290 nm) and cold plasma-grafting techniques, to alter the surface properties, such as hydrophilicity and, therefore, biocompatibility. Here, we have carried out simultaneous plasma-grafting, unlike the conventional post plasma-grafting. The effect of different surface grafting techniques on the degree of surface modification and resultant biocompatibility has been investigated. The chemical changes on the polymer backbone are followed from the results of attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), which shows the peaks corresponding to the functional groups of the monomers grafted onto the film surface. The morphology of the modified surfaces was investigated using scanning electron microscopy (SEM) technique. The induced hydrophilicity and resultant cell compatibility were followed from the water contact angle measurements and in vitro human carcinoma cell adhesion/proliferation tests, respectively. All the grafted samples exhibited variable cell compatibilities depending upon the type of monomer and their degree of grafting; however, always better than the neat samples. Hydroxyethyl methacrylate and acrylic acid showed exceptionally high cell compatibility in terms of cell adhesion and proliferation.

Biocompatible Materials↗

PubMed2006

Fabrication of conductive membrane in a polymeric electric field gradient focusing microdevice.

A novel approach to integrating a buffer ion-permeable membrane in a poly(glycidyl methacrylate-co-methyl methacrylate) micro electric field gradient focusing (muEFGF) device is described. A weir structure on which the membrane was positioned was fabricated between the separation channel and field gradient-generating channel. Before formation of the membrane, the surface of the polymeric microdevice was treated for covalent bonding of the membrane. Following surface modification, a prepolymer solution containing poly(ethylene glycol) acrylate/methacrylate and Tris-HCl buffer was loaded into the microdevice. Low-pressure nitrogen gas was then purged through the separation and field gradient-generating channels to remove the prepolymer solution from these channels. Residual prepolymer solution was retained on the weir structure due to surface tension. Finally, the premembrane was cured in place on the weir using UV radiation. Using a muEFGF device, green fluorescent protein (GFP) was concentrated 4000-fold. Separation of GFP and R-phycoerythrin, and selective elution of GFP from a protein mixture containing GFP, FITC-labeled casein, and FITC-labeled hemoglobin were also demonstrated. It was found that the membrane conductivity and presence of carboxylic acid impurities in the membrane strongly affected the behavior of the muEFGF device.

Electricity↗