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PubMedDate not supplied

Surface modification of enzymes for therapeutic use: monomethoxypoly (ethylene glycol) derivatization of ribonuclease.

Bovine pancreatic ribonuclease A (RNase) was modified at various extent at the lysine residues by monomethoxypoly(ethylene glycol) (MPEG) activated as active ester. For pharmacokinetic experiments a radioactive adduct was also prepared with tritiated amino acid as spacer between polymer and protein. The modification reduced only slightly the RNase catalytic activity and Km towards the substrate cytidine-2',3'-cyclic monophosphate. On the other hand extensively modified MPEG-RNase samples, showed significant decrease in activity towards ribonucleic acid. The polymer modification did not change the pH activity profile, increased the stability to proteolytic digestion, while the behaviour towards denaturants and heat was not modified. The native and MPEG-RNase administered IV, IM and SC to rats, showed impressive differences in pharmacokinetics: the half-life of the modified enzyme, evaluated in blood by radioactivity, was increased of 40-50 folds with respect to the native form.

Animals↗
PubMedDate not supplied

Increased target specificity of anti-HER2 genospheres by modification of surface charge and degree of PEGylation.

Genospheres are cationic lipid-nucleic acid nanoparticles prepared by the assembly of the lipids and nucleic acids from an aqueous/organic liquid monophase that independently dissolves the components, where the resultant particles are homogeneously sized (70-110 nm), with efficiently incorporated and protected DNA. In the present study, we demonstrate pH-dependent modulation of the Genosphere surface charge using pH-titratable lipids. By incorporation of the lipids with titratable anionic or imidazole headgroups, Genospheres with neutral or anionic surface charge at neutral pH were produced and compared for cellular uptake and transfection of a reporter gene (luciferase) in culture of breast cancer cells. The extent of particle-cell association was also studied by fluorescent microscopy and quantified by cytofluorometery. The effects of Genosphere surface modification with poly(ethylene glycol) (molecular weight 2000) at low (0.5 mol %) and high (5 mol %) grafting densities, as well as the effects of HER2-receptor-directed targeting by an internalizable anti-HER2 scFv F5, linked via PEG spacer, were also studied. Inclusion in the Genosphere formulation of pH-titratable lipids CHEMS (cholesteryl hemisuccinate), CHIM (1-(3-(cholesteryloxycarbonylamino)propyl)imidazole), or DSGG (1,2-distearoyl-sn-glycero-3-hemiglutarate) rendered the particles surface-charge neutral or slightly anionic at neutral pH, and cationic at mildly acidic pH, as shown by zeta-potential measurements. In HER2-targeted systems, transfection activity and target specificity with HER2-overexpressing SKBR-3 breast cancer cells were dependent on Genosphere surface charge and PEGylation. The highest target specificity correlated with low cationic charge at neutral pH, while incorporation of 5 mol % PEG-lipid had only minor effects on Genosphere-cell association, internalization, and transfection activity. The implications of this work for potential in vivo applications are discussed.

Antibodies↗
PubMed2005

Modification of micronozzle surfaces using fluorinated polymeric nanofilms for enhanced dispensing of polar and nonpolar fluids.

In this work, we report on the surface modification of a micronozzle surface to enhance fluid dispensing in the nanoliter range. Unmodified dispensing chips usually suffer from lateral wetting of the nozzle surfaces by low surface tension liquids resulting in poor control of the volume of the dispensed fluid. Covalent attachment of a fluorinated acrylate polymer to the outer surface of the micronozzle using a novel UV irradiation process helps to overcome capillary and adhesive forces and results in an enhancement of the control on fluid dispensing in the nanoliter range. The modified nozzles have been tested with a variety of fluids having a wide range of surface tensions. The surface modification allows precise control of the dispensing of nanoliter droplets with a high degree of reproducibility.

Fluorine Compounds↗
PubMed1975

Species variability in the modification of erythrocyte surface proteins by enzymatic probes.

Bovine and equine erythrocytes have been studied by three different surface modification techniques to investigate the accessibility of the surface components to the external medium. Lactoperoxidase labeling of equine erythrocytes results in a significant labeling of only one membrane component, a 100 000-mol.wt polypeptide corresponding to the membrane-spanning Component III of human erythrocytes. The major sialoglycoprotein of the equine erythrocyte is not labeled. This is in contradistinction to the situation for human and bovine cells, where both components are labeled. The equine membrane sialoglycoprotein is also not markedly affected by pronase, chymotrypsin or trypsin treatment of whole cells under the treatment conditions used, although it can be cleaved by pronase in isolated membranes. Experiments with the isolated glycoprotein show that its cleavage by trypsin is quite selective, whereas cleavage by pronase and chymotrypsin is much more extensive. Labelling of bovine red cells by galactose oxidase treatment followed by reduction with 3H-labeled borohydride yields radioactivity in only one major peak, that corresponding increase in labeling. Equine erythrocytes don not show significant labeling by this technique unless a neuraminidase pretreatment has been performed. Then only the major glycoprotein is labeled. Thus the equine glycoprotein is apparently inaccessible to the cell surface by standard surface modification methods, although it is clearly a surface component. These experiments point out some of the limitations of surface labeling and proteolysis methods in probing the accessibility of membrane components. The results suggest that apparent inaccessibility of the equine glycoprotein is due partially to its structure and partially to its localization in the membrane.

Alcohol Oxidoreductases↗
PubMed2006

Biochemical modification of titanium surfaces: peptides and ECM proteins.

This paper reviews current approaches to the enhancement of bone regeneration at the interface with implant devices, by immobilization of biomolecules to titanium surfaces. In particular, techniques based on surface linking of peptides or extracellular matrix (ECM) proteins are reviewed, trying to describe surface modification approaches and to present results of chemico-physical and biological evaluations, both in vitro and in vivo. Based on existing literature, surface modification by peptides or ECM proteins appears as an effective way to stimulate bone regeneration over that provided by titanium, as suggested by basic studies and in vitro results and confirmed by in vivo findings.

Animals↗
PubMed1999

[Interaction of cell adhesion to materials in tissue engineering].

OBJECTIVE: To investigate the adhesive interactions of cells with materials and the effects of material properties on cell adhesion in tissue engineering. METHODS: By looking up the recent literatures dealt with adhesive interactions of cells with materials and reviewing previous work on the adhesion of tissue-derived cells to materials. RESULTS: The adhesion characteristics of cells to materials not only depend on the nature of materials, including bulk and surface properties, surface modification, surface morphology, net charge, porosity and degradation rate, but also on the expression of cell surface molecules and their interaction with the material. CONCLUSION: The quantitative measure and biophysical mechanisms of cell adhesion to materials might be very important in tissue engineering.

Biocompatible Materials↗
PubMed2006

Characterizing the modification of surface proteins with poly(ethylene glycol) to interrupt platelet adhesion.

Surface protein modification with poly(ethylene glycol) (PEG) can inhibit acute thrombosis on damaged vascular and biomaterial surfaces by blocking surface protein-platelet interactions. However, the feasibility of employing protein reactive PEGs to limit intravascular and biomaterial thrombosis in vivo is contingent upon rapid and extensive surface protein modification. To characterize the factors controlling this potential therapeutic approach, the model protein bovine serum albumin was adsorbed onto polyurethane surfaces and modified with PEG-carboxymethyl succinimidyl ester (PEG-NHS), PEG-isocyanate (PEG-ISO), or PEG-diisocyanate (PEG-DISO) in aqueous buffer at varying concentrations and contact times. It was found that up to 5 PEGs could be attached per albumin molecule within one min and that adsorbed albumin PEGylation approached maximal levels by 6min. The lability of reactive PEGs in aqueous buffer reduced total protein modification by 50% when the PEG solution was incubated for 7min prior to application. For fibrinogen PEGylation (performed in the solution phase), PEG-NHS was more reactive than PEG-ISO or PEG-DISO. The gamma peptide of fibrinogen, which contains several key platelet-binding motifs, was highly modified. A marked reduction in platelet adhesion was observed on fibrinogen-adsorbed polyurethane treated with PEG-NHS or PEG-DISO. Relative differences in platelet adhesion on PEG-NHS and PEG-DISO modified surfaces could be attributed to differences in reactivity towards fibrinogen and the size of the polymer backbone. Taken together, these findings provide insight and guidance for applying protein reactive PEGs for the interruption of acute thrombotic deposition.

Animals↗
PubMed2005

Photocatalytic degradation of p-nitrophenol on nanometer size titanium dioxide surface modified with 5-sulfosalicylic acid.

The surface of nanometer size TiO(2) was simply and fast modified by chemical adsorption in saturated solution of 5-sulfosalicylic acid. After surface modification, a stable, yellow surface complex was formed quickly, the wavelength response range of TiO(2) was expanded, it has obvious absorption in the region from 320 to 450 nm; the adsorption efficiency of p-nitrophenol (PNP) by TiO(2) was enhanced from 42% to 84%. The photocatalytic activity was tested on the degradation of PNP. The influences of catalyst and its dosage, pH value, and PNP concentration on the degradation were investigated. On optimal photodegradation conditions, including initial pH 4.0, PNP 5 mg l(-1), catalyst 100 mg, irradiation time 120 min with 160 W high-pressure mercury lamp, the degradation efficiency of PNP was increased from 40% to 88% after surface modification. Surface modification led not only to an increase in the light utilization, but also improved the surface coverage of PNP in comparison with the pure TiO(2). Both of these factors are crucial for the photocatalytic activity of heterogeneous photocatalysis, especially for photodegradation of benzenoid pollutants.

Adsorption↗
PubMed1999

[Modification of the surface of prosthetic valve material by LGDP for protection against microbial adhesion].

This study aimed at the surface modification of prosthetic valve materials by means of cold glow discharge plasma. Orthogonal design was adopted to select the optimal scheme by the experiments of the singular factor, such as output power, gas flow rate, treatment time etc. The PEG-200 was introducted to the surface. Grafting a layer of heparin onto the surface; coating a layer of PEG-like onto the surface first, and then the grafting heparin. Comparing the adhesive amounts of staphylococcus epidermidis (SE), the adhesive curves for Dacron, which was treated by the above methods; the last one is the best.

Bacterial Adhesion↗
PubMed2004

Chemical modification of the surface of a sulfonated membrane by formation of a sulfonamide bond.

This paper describes a novel approach for the surface modification of a cation-exchange membrane, bearing sulfonate groups, by a cationic layer. The modification procedure involved the chlorosulfonation of the sulfonate groups of the base membrane with thionyl chloride, followed by a reaction with a diamine to yield a sulfonamide bond and a terminal amine. The latter could be quaternized by reaction with methyl iodide or protonated by soaking in acidic media. The membranes were characterized in detail by attenuated total reflectance Fourier transform infrared and X-ray photoelectron spectroscopies as well as elemental analysis to confirm that the above reactions occurred. The selectivity of these membranes toward the electrochemically assisted transport of protons versus Zn2+ metallic cations was determined during an electrodialysis in a two-compartment electrochemical cell. The data indicate a significant decrease of the transport of the metallic cations following modification of the membrane with the cationic layer. The later allows for the transport of protons from the catholyte to the anolyte compartment with much improved selectivity since the divalent cations are excluded from the membrane due to the electrostatic barrier of the cationic layer.

Diamines↗