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PubMed2006

Use of PLL-g-PEG in micro-fluidic devices for localizing selective and specific protein binding.

By utilizing flow-controlled PLL-g-PEG and PLL-g-PEGbiotin modification of predefined regions of a poly(dimethylsiloxane) (PDMS) micro-fluidic device, with an intentionally chosen large (approximately 1 cm2) internal surface area, we report rapid (10 min), highly localized (6 x 10(-6) cm2), and specific surface-based protein capture from a sample volume (100 microL) containing a low amount of protein (160 attomol in pure buffer and 400 attomol in serum). The design criteria for this surface modification were achieved using QCM-D (quartz crystal microbalance with energy dissipation monitoring) of serum protein adsorption onto PLL-g-PEG-modified oxidized PDMS. Equally good, or almost as good, results were obtained for oxidized SU-8, Topas, and poly(methyl metacrylate) (PMMA), demonstrating the generic potential of PLL-g-PEG for surface modification in various micro-fluidic applications.

Adsorption↗

PubMed2005

Encapsulation of drug nanoparticles in self-assembled macromolecular nanoshells.

Layer-by-Layer (LbL) stepwise self-assembly of the polyelectrolytes poly(allylamine hydrochloride) and poly(styrenesulfonate) was used to create a macromolecular nanoshell around drug nanoparticles (approximately 150 nm in diameter). Dexamethasone, a steroid often used in conjugation with chemotherapy, was chosen as a model drug and was formulated into nanoparticles using a modified solvent-evaporation emulsification method. Measurement of the zeta potential (zeta-potential) after each polyelectrolyte layer was electrostatically added confirmed the successful addition of each layer. Additionally, data acquired from X-ray photon spectroscopy (XPS) indicated the presence of peaks representative of each physisorbed polyelectrolyte layer. Surface modification of the nanoshell was performed by covalently attaching poly(ethylene glycol) (PEG) with a molecular weight of 2000 to the outer surface of the nanoshell. Zeta potential measurements and XPS indicated the presence of PEG chains at the surface of the nanoshell. The polymeric nanoshell on the surface of the drug nanoparticle provides a template upon which surface modifications can be made to create a stealth or targeted drug delivery system.

Dexamethasone↗

PubMed2005

[On the active mechanism of hydroxyapatite modified by cold plasma].

The surface modification using cold plasma technique was introduced to hydroxyapatite(HA). The methods adopted in the study included the formation of bone-like apatite in simulated body fluid and the use of SEM, XPS and XRD. The results showed that the formation of bone-like apatite on HA modified by cold plasma was easier than that without modification. The active mechanism involves the impact of the particles with high energy and high activity against HA, which roughens and etches the surface of HA, heads to the distortion of HA crystal, and thus increases the dissolvability of HA and the local concentration of the Ca and P ions. This approach is helpful to the formation of bone-like appetite. The data demonstrate that the surface modification using cold plasma technique can increase the activity of HA.

Apatites↗

PubMed2001

Surface transformation of bioactive glass in bioreactors simulating microgravity conditions. Part II: numerical simulations.

The effects of simulated microgravity on the surface modification of bioactive glass (BG) in solution were studied using a numerical method. Models were developed for estimating the mass transfers of different chemical species from the surface of bioactive glass particles (microcarriers) suspended in the rotating liquid medium of a NASA-designed high aspect ratio vessel (HARV) bioreactor and on the bottom surface of a static vial. The concentration profiles resulting from chemical reactions and ionic transports were ascertained. Numerical results for the transport under simulated microgravity in the HARV and at normal gravity in the static vial were compared. These results were also compared with those of experiments to verify the enhancement of the reaction kinetics under simulated microgravity conditions. The experimental and numerical studies confirm that simulated microgravity conditions lead to the quick achievement of bioactive glass surface modification.

Bioreactors↗

PubMed2002

Determination of standard electrode potential E(o) for chronic platinum and gold electrodes in rat muscle: implications for biosensors and the "anode" of bipolar pacing.

Pacemaker electrode surface modification by organosilane and organic self-assembled monolayer strategies creates a possible new variable in pacemaker electrode behavior. Because all of these chemical surface coatings are unstable at extremes of potential, the potential to which the electrode relaxes (between pacing pulses) becomes extremely important. The authors measured this potential for platinum (Pt) and gold (Au) relevant for their use as anode (or cathode) in a bipolar pacing system and from this potential the standard electrode potential, E(o) was determined. Thirty-Four determinations were made by a null current three-electrode potentiostatic technique of 2.45 mm2 platinum or gold electrodes implanted chronically in blood perfused muscle in a spontaneously breathing rat. Linear voltage sweeps were performed while monitoring current with voltage at null current determined repeatedly at varying scan rates and limits. Electrode potential varied between -388 +/- 19 mV (vs Ag/Ag+) for platinum and -388 +/- 55 mV for gold electrodes. Hysteresis was observed in all sweeps (P < 0.008, Fisher's exact) and measured 61 +/- 17 mV (anodic) and 25 +/- 3 mV (cathodic) with steep dependence on polarity (P < 0.001, t-test). The findings were independent of the materials' electronic work function. E(o) versus normal hydrogen electrode (NHE) were thus -166 mV (platinum) and -166 mV (gold). Because the most common bipolar system, uses platinum as anode, these results are directly applicable to current pacing technology. Provided low thresholds are achievable with novel surface modified electrodes, the small range of variation of E(o), and the particular mean value observed, are both compatible with function, provided care is used during electrode testing to avoid surface disruption. These results are significant also for biosensors that use similar surface modification methodologies.

Animals↗

PubMed2005

Modification of MSW fly ash by anionic chelating surfactant.

This paper elucidates a study on the re-utilization and stabilization of municipal solid waste (MSW) fly ash in producing a high value-added product by the surface modification of anionic chelating surfactant on the particles. After modification, MSW fly ash can be expected using as a filler of ultra-high molecular weight polymers. The effects of anionic chelating surfactants (ACS) on surface modification of MSW fly ash and fixing capacity for heavy metals were explored. Meanwhile, the interaction mechanism between surfactants and MSW fly ash was suggested. The results showed that anionic chelating surfactants can be used to effectively modify MSW fly ash particles and achieve a high active ratio. At the same time, they also exhibited a strong fixing capacity for heavy metals. Of the two modified MSW fly ash, ED3A-modified MSW fly ash has a much higher active ratio than MAP-modified MSW fly ash at over 95%, although its fixing capacity for heavy metals was a shade lower than MAP-modified MSW fly ash.

Anions↗

PubMed1993

Synthesis and application of new microcarriers for animal cell culture. Part II: Application of polystyrene microcarriers.

In this work (Part II) the application of new polystyrene based microcarriers in cell culture technology is demonstrated. Carriers with a variety of surface modifications were tested as a growth support for cell line BHK 21. The growth behavior of the cells and cell to surface attachment were compared to Cytodex 3 (Pharmacia), which was used as a reference carrier. To select carriers with growth supporting surfaces, broad screening in petri dish experiments was carried out. Candidates with the highest growth rates were investigated in spinner flash experiments in further detail. Polystyrene carrier with a surface modification like triethylamine, maltamine or N-methylglucosamine were able to support growth as good or better as the reference carrier Cytodex 3. Economies of ingredients and ease in laboratory handling could make amine-modified polystyrenes a competitive alternative to currently commercially available microcarrier types.

Animals↗

PubMed2004

Covalent attachment of a nickel nitrilotriacetic acid group to a germanium attenuated total reflectance element.

The surface of a germanium internal reflectance element (IRE) was modified to bind 6X-histidine (his)-tagged biomolecules. The step-by-step surface modification was monitored via single-pass attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FT-IR). Initially an adlayer of 7-octenyltrimethoxysilane (7-OTMS) was formed on the Ge crystal through the surface hydroxyl groups, which were produced via ozonolysis of the Ge surface. The vinyl moiety of 7-OTMS was oxidized to a carboxylic acid, which was activated by 1,1'-carbonydiimidazole (CDI) to produce a labile imidazole. The labile imidazole that resulted from the CDI coupling was then displaced by the primary amine of nitrilotriacetic acid (NTA). Nickel sulfate was added to the system, and it coordinated with the three carbonyl groups and the nitrogen on NTA, thus leaving the ability of Ni to coordinate with two adjacent histidine residues. Binding of his-tagged biotin to nickel nitrilotriacetic acid (Ni-NTA) was observed by ATR-FT-IR spectroscopy. The surface modification method presented in this paper had minimal nonspecific binding, the Ni-NTA surface was reusable if stored properly, and complete removal of the organic surface was achievable.

Journal Article↗

PubMed2002

Visible-light-induced surface graft polymerization via camphorquinone impregnation technique.

A surface modification method that is particularly applicable to complexly shaped fabricated devices has long been awaited. In this article, we describe the visible-light-induced surface photograft polymerization technique by which an inner surface of the device is modified by visible-light irradiation through the external surface. Comphorquione, as a photoradical initiator, was impregnated on a segmented polyurethane surface by solvent soaking, followed by visible-light irradiation in the presence of monomers such as acrylamide and poly(ethylene glycol) methacrylate. The resultant surfaces were highly wettable with water, and surface chemical compositional analysis by X-ray photoelectron spectroscopy revealed that the surface was graft-polymerized with these monomers. The simple and widespread applicability of this surface modification technique to biomedical devices is discussed.

Biocompatible Materials↗

PubMed1985

In vitro biologic toxicity of native and surface-modified silica and kaolin.

An in vitro study of the biologic responses of surface-modified and native silica and kaolin was made to provide comparative information on the suppression of cytotoxicity by pulmonary surfactant. The release of alveolar macrophage cytoplasmic enzyme, lactate dehydrogenase (LDH), and lysosomal enzymes beta-N-acetylglucosaminidase (beta-NAG) and beta-glucuronidase (beta-GLUC) and sheep blood-cell hemolysis were monitored as indicators of cell membrane damage and cytotoxicity. Surface modification of silica and kaolin with dipalmitoyl lecithin (DPL) resulted in complete abrogation of cytotoxicity of both minerals. These findings indicate that surface modification of minerals with different adsorption properties by pulmonary surfactant generally lessens their prompt adverse effects.

Acetylglucosaminidase↗

PubMed2002

Comparison of surface properties of random, block, and graft copolymers having perfluoroalkyl and silicone-containing side chains.

Fluorosilicone copolymers of random, block, and graft with both perfluoroalkyl and silicone-containing side chains were synthesized, and their surface properties and surface modification effects on PVC film were compared. It can be confirmed that the fluorosilicone copolymers of random, block, and graft exhibit very low surface free energies of 9-13 dyn/cm, depending on the perfluoroalkyl group content and their molecular structure. The inherent surface free energies of the fluorosilicone copolymers are significantly influenced by their molecular structure and perfluoroalkyl group content. It can also be found that the fluorosilicone copolymers are very effective for lowering surface free energy. The surface free energy of a copolymer/PVC blend strongly varies with perfluoroalkyl group content as well as molecular structure. The molecular structure of a fluorosilicone copolymer is as important as the perfluoroalkyl group content for their inherent surface free energies and surface modification of other polymers.

Journal Article↗

PubMedDate not supplied

Capillary zone electrophoresis of biological substances with fused silica capillaries having zero or constant electroosmotic flow.

A series of capillary surface modifications entailing multilayered coatings were introduced and evaluated in capillary zone electrophoresis of biological substances, e.g., proteins, peptides, oligosaccharides and nucleotides. In one set of surface modifications, large molecular weight hydroxypropyl cellulose afforded "zero" flow capillaries, which were used as precursors for developing anodal flow capillaries. When "zero" flow capillaries were further functionalized with a charge polyethyleneimine layer to which a top polyether layer was covalently attached, the resulting anodal electroosmotic flow was relatively weak due to the high viscosity of the coated wall imparted by the hydroxypropyl cellulose layer. Capillaries with relatively strong and constant anodal electroosmotic flow were best achieved when the inner capillary surface was first chemically derivatized with methylated (i.e., quaternarized) polyethyleneimine hydroxyethylated. This hydroxylated and permanently charged polymeric coating yielded constant anodal flow regardless of electrolyte pH. The hydroxyl groups of the charged polymeric coating permitted the covalent attachment of polyether chains, which minimized electrostatic interaction between the positive charges of the polymeric layer and oppositely charged biopolymers. Under these conditions, rapid transport of acidic biopolymers past the detection point in the separation capillary could be achieved, and relatively high plate counts were obtained.

Amino Acid Sequence↗

PubMed1991

Photochemical coatings for the prevention of bacterial colonization.

Biomaterials are being used with increasing frequency for tissue substitution. Implantable, prosthetic devices are instrumental in the saving of patients' lives and enhancing the quality of life for many others. However, the greatest barrier to expanding the use of biomedical devices is the high probability of bacterial adherence and proliferation, causing very difficult and often untreatable medical-device centered infections. The difficulty in treating such infections results in great danger to the patient, and usually retrieval of the device with considerable pain and suffering. Clearly, development of processes that make biomedical devices resistant to bacterial adherence and colonization would have widespread application in the field of biomedical technology. A photochemical surface modification process is being investigated as a generic means of applying antimicrobial coatings to biomedical devices. The photochemical process results in covalent immobilization of coatings to all classes of medical device polymers. A discussion of the photochemical surface modification process and preliminary results demonstrating the success of photochemical coatings in formulating microbial-resistant surfaces are presented in this paper.

Anti-Bacterial Agents↗

PubMed1997

Organic surface chemistry on titanium surfaces via thin film deposition.

In order to develop a synthetic strategy for the fine tuning of the interfacial properties of titanium-based implants and implant parts, a thin polymeric film was deposited from ethylene plasma on the surfaces of Ti foils. The intended aim was to further modify the adherent, delamination-resistant organic coating using the techniques of surface modification of polymers to direct interfacial interactions at the metal foil-biological phase interface. In particular, air-plasma treatment and Ce(IV)-induced hydroxyethylmethacrylate grafting, two typical reactions of biomedical polymers surface chemistry, were used to improve cell adhesion or to impart cell resistance to the plasma-coated Ti. Results indicate that a plasma-deposited thin polymeric film effectively can act as a viable substrate for further surface chemical modifications and allow the application of a huge background of surface-modification polymers to metallic devices.

Animals↗

PubMed2005

[Comparison of modification of surface xenoantigens on bovine and porcine erythrocytes].

This study was aimed to explore impact of removal of cell membrane G alalpha1-3Gal beta1-4Glc NAc epitopes (called alpha-Gal) and chemical modification of other xenoantigen on bovine red blood cell (bRBC) and porcine red blood cell (pRBC) antigenicity and to compare their modified erythrocytes, in order to provide basis for development of human blood substitute with rich source, high safety and efficacy. bRBC and pRBC were subjected to both enzymatic removal of membrane alpha-Gal with recombinant coffee bean alpha-galactosidase (rC alpha-GalE) and covalent attachment of benzotriazole carbonate-linked methoxypolyethylene glycol (mPEG-BTC, MW = 20 kD). The effects of treatment were measured by hemagglutination, flow cytometric assay of IgG binding and clinical cross-match testing to human sera. The results showed that although alpha-galactosidase treatment reduced hemagglutination titers to levels similar to negative control, the combination of the treatments was most effective. Clinically used cross-match tests between bRBC, pRBC and human sera demonstrated increased compatibility. Bovine RBC were more robust than pRBC, and had less xenoantigens, and had longer half life than pRBC in vivo. These characteristics suggested that bRBCs were more suitable to investigation as an alternatives to hRBC in clinical transfusion than pRBC. These data suggested that strategies to remove or mask xenoantigens on bRBC reduce antigenicity sufficiently to allow in vitro cross-match compatibility to human sera, and therefore bRBC following modification may be considered as human blood substitute.

Animals↗

PubMed1999

Uniform-sized molecularly imprinted polymer for (S)-naproxen selectively modified with hydrophilic external layer.

A uniform-sized molecularly imprinted polymer (MIP) for (S)-naproxen selectively modified with hydrophilic external layer has been prepared. First, the molecularly imprinted polymer for (S)-naproxen was prepared using 4-vinylpyridine and ethylene glycol dimethacrylate (EDMA) as a functional monomer and cross-linker, respectively, by a multi-step swelling and thermal polymerization method. Next, a 1:1 mixture of glycerol monomethacrylate (GMMA) and glycerol dimethacrylate (GDMA) was used for hydrophilic surface modification, and it was added directly to the molecularly imprinted polymer for (S)-naproxen 4 h after the start of molecular imprinting. The retention factors of all solutes tested were decreased with the surface modified molecularly imprinted polymer, compared with the unmodified molecularly imprinted polymer. However, chiral recognition of racemic naproxen was attained with the surface modified molecularly imprinted polymer as well as the unmodified molecularly imprinted polymer. Further, bovine serum albumin was completely recovered from the surface modified molecularly imprinted polymer. These results revealed that the chiral recognition sites of (S)-naproxen remained unchanged with hydrophilic surface modification, and that the molecularly imprinted polymer for (S)-naproxen was selectively modified with hydrophilic external layer. Preliminary results reveal that the surface modified molecularly imprinted polymer could be applicable to direct serum injection assays of (S)-naproxen.

Chromatography, High Pressure Liquid↗

PubMed2006

Galactose derivative immobilized glow discharge processed polyethersulfone membranes maintain the liver cell metabolic activity.

New strategies aimed to surface modification of polymeric membranes are crucial to optimise cell-biomaterial interactions in vivo and in vitro biohybrid systems. In this paper, we investigated the surface modification of Polyethersulfone (PES) membranes by plasma polymerisation of acrylic acid monomers (PES-pdAA) and by immobilization of galactonic acid through a hydrophilic "spacer arm" molecule (PES-pdAA-SA-GAL). The modification steps were characterised by high resolution X-ray photoelectron spectroscopy. The performance of modified and unmodified membranes was evaluated by assessing the expression of liver specific biotransformation functions of pig and human hepatocytes. Human liver cells cultured on PES-pdAA-SA-GAL membranes displayed an enhanced albumin production, urea synthesis and protein secretion for 24 days of culture. The immobilisation of galactose derivative units on the membrane allowed specific interactions with hepatocytes biomimicking the cellular microenvironment and produced an improvement of the long-term maintenance and differentiation of human hepatocytes.

Acrylates↗

PubMed2001

Hepatocyte [3H]-palmitate uptake: effect of albumin surface charge modification.

The role of plasma proteins on the cellular uptake of lipophilic substrates has perplexed investigators for many years. We tested the hypothesis that an ionic interaction between the protein-ligand complex and hepatocyte surface may be responsible for supplying more ligand to the cell for uptake. The surface-charged groups on albumin were modified to yield proteins having a range of isoelectric points (ALB, ALBs, ALBm, ALBe had values of 4.8-5.0, 4.5-4.7, 3.0-3.5, 8.4-8.6, respectively). [3H]-Palmitate uptake studies were performed with adult rat hepatocyte suspensions using similar unbound ligand fractions in the presence of the different binding proteins. Mass spectrometry, isoelectric focusing (pI), and heptane:water partitioning were used to determine protein molecular weight, pI, and protein-palmitate equilibrium binding constant, respectively. Hepatocyte [3H]-palmitate clearance in the presence of ALBs and ALBm were significantly lower (p < 0.05) than ALB, whereas [3H]-palmitate clearance in the presence of ALBe was significantly higher (p < 0.05) than ALB. The data were consistent with the notion that ionic interactions between extracellular protein-ligand complexes and the hepatocyte surface facilitate the uptake of long-chain fatty acids.

Albumins↗