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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↗
PubMed1985

Surface modification of proteins. Activation of monomethoxy-polyethylene glycols by phenylchloroformates and modification of ribonuclease and superoxide dismutase.

A single-step method of activation of monomethoxypolyethylene glycols suitable for its binding to polypeptides and proteins is proposed. Based on the reaction with 2,4,5-trichlorophenylchloroformate or p-nitrophenylchloroformate, it gives reactive PEG-phenylcarbonate derivatives. The PEG intermediate is stable on storage, the activating group is easily quantified,and the reaction with amino acid and proteins proceeds rapidly at pH near neutrality. The PEG derivatization of enzymes with this procedure is less inactivating than those previously reported. Ribonuclease and superoxide dismutase were modified and the effect of (a) bound polymer on clearance time in rats, (b) antibody recognition, and (c) on the enzymatic activity toward low and high molecular weight substrates were studied.

Amino Acids↗
PubMedDate not supplied

Gelatin nanoparticles by two step desolvation--a new preparation method, surface modifications and cell uptake.

A new two-step desolvation method for manufacturing gelatin nanoparticles was developed. After the first desolvation step, the low molecular gelatin fractions present in the supernatant were removed by decanting. The high molecular fractions present in the sediment were redesolved and then desolvated again at pH 2.5 in the second step. The resulting particles can then be easily purified by centrifugation and redispersion. The different fractions obtained during the process were analysed by gel permeation chromatography (GPC). Based on these results, it can be concluded that the molecular weight of gelatin has a decisive influence on the stability of the manufactured gelatin nanoparticles. In addition, two fluorescent dyes (Texasred and fluoresceinamine) were coupled to the nanoparticles for cell uptake studies. The fluorescent nanoparticles showed a high uptake into monocytes/macrophages.

Cells, Cultured↗
PubMed1975

Surface modifications evoked by estradiol and diethylstilbestrol in isolated endometrial cells: evidence from lectin probes and extracellular release of lysosomal protease.

Endometrial cells were isolated from the uteri of ovariectomized rats. The inhibitory effect of alpha-methyl-D-mannoside on fluorescein-labeled concanavalin A (Con A) binding to these cells indicates that they possess specific binding sites for Con A. The lectin also mediates adsorption of homologous erythrocytes to these cells. Both Con A binding and Con A-mediated hemadsorption to endometrial cells are depressed at 4 C compared with these functions in cells maintained at 22 C. Gross elevations in lectin-mediated hemadsorption to endometrial cells are evident following prior exposure to 1 X 10(-9)M concentrations of diethylstilbestrol (DES) or estradiol-17beta, but not to the physiologically inactive 17 alpha-epimer, at 22 C. The enhancement of hemagglutinability cannot be attributed to a corresponding increase in lectin binding at 22 C. Although estrogen treatment elicited significant increments in Con A binding as early as 5 min after addition of estrogen to cell suspensions, the increment in agglutination attributable to hormone treatment consistently ranged from 1.5-3 times greater than the increase in lectin binding. These estrogenic effects were reduced by incubation of the endometrial cells at 4 C or when cortisol, 3 X 10(-6)M, was present with estradiol-17beta. In parallel experiments, treatment with DES and estradiol-17beta, but not estradiol-17 alpha, also enhanced the release of cathepsin B 1 and acid phosphatase from uterine segments into the particle-free extracellular media in which the tissues had been incubated for 30-60 min. The marked increment in the extracellular activity of the lysosomal hydrolases induced by estrogen treatment was suppressed in cells incubated at 4 C or when cortisol was present concomitantly. These and related data suggest the hypothesis that acute increments in lysosomal hydrolase activity may contribute to cell surface alterations which have been described in both normal and aberrant processes of cell growth.

Acid Phosphatase↗
PubMed1997

Lymphatic uptake and biodistribution of liposomes after subcutaneous injection: III. Influence of surface modification with poly(ethyleneglycol).

PURPOSE: The aim of the present paper was to assess the effect of inclusion of distearoylphosphatidylethanolamine-poly(ethyleneglycol) (DSPE-PEG) into liposomal bilayers on the lymphatic uptake and lymph node localization of liposomes after subcutaneous administration. METHODS: [3H]-Cholesteryloleylether labeled liposomes of various composition and sizes were injected s.c. into the dorsal side of the foot of rats. At several time-points after injection, blood levels of liposomes were determined. Lymphatic uptake from the s.c. site of injection and lymph node localization in regional lymph nodes were determined at the end of the 52 h observation period. RESULTS: The results demonstrate that inclusion of DSPE-PEG into several types of liposomes has only a modest effect on lymphatic uptake. Also lymph node localization is only slightly affected by PEG-mediated steric stabilization. CONCLUSIONS: Factors other than the presence of a steric barrier are more important in determining lymphatic uptake from the s.c. injection site. The observation that lymph node localization was only slightly affected by PEG-coating strongly suggests that macrophage uptake is not the only important mechanism of lymph node localization of s.c. administered liposomes.

Animals↗
PubMed2003

Irradiation effects in MALDI, ablation, ion production, and surface modifications. Part II. 2,5-dihydroxybenzoic acid monocrystals.

Irradiation effects at low and high laser fluence on 2,5-dihydroxybenzoic acid large crystals were investigated. Contrary to what was observed for matrices as cinnamic acid derivatives, no chemical degradation of matrix is evidenced and continuous ablation as well as ion production resulted of extended irradiation in all the fluence range corresponding to classical matrix-assisted laser desorption /ionization. Ripples are formed on the base of the crater for a limited number of laser shots under moderate fluence. For extended irradiation, conical shape craters are formed with the axis of the crater oriented along the incident direction of the laser beam. A study of the craters showed that ablation through the ablated volume slowly varied with the laser fluence when a strong increase of ion production (matrix and analyte) was recorded. Ablation volume was found to vary non-linearly with the number of laser shots. On a same spot, the ablated volume and the ion production were measured as a function of the laser energy. With an increasing laser energy (or fluence), the ablated volume slowly increases when the ion production strongly increases. This gives evidence of a decoupling between ablation and ionization. Interaction of the plume with the incoming beam is thus probable.

Crystallization↗
PubMed2002

Surface modification of extrasynovial tendon by chemically modified hyaluronic acid coating.

We investigated a method for chemically binding hyaluronic acid (HA) to extrasynovial tendon and the effect of chemically modified HA on the gliding resistance of tendon. Canine peroneus longus (PL) tendons were immersed into one of three different solutions (saline, 1% HA, or 1% chemically modified HA) for 2 h. The gliding resistance of treated PL tendons was measured at 1, 5, 10, 20, 50, and 100 cycles in a saline bath. After treatment with unmodified HA and chemically modified HA, the gliding resistance of the PL tendons decreased significantly compared with the saline-treated tendons (p < 0.05), and this effect of the two HA treatments persisted through 10 cycles. For cycles 20-100, the gliding resistance of PL tendons treated with chemically modified HA remained significantly lower than that of tendons treated either with saline or unmodified HA (p < 0.01). The effect of paratenon removal on gliding resistance was neither statistically significant for repetitions beyond 10 cycles, nor was it an independent predictor of gliding resistance, as the effect (higher resistance after paratenon removal) was mainly seen in the saline-treated tendons. Chemically modified HA-treated extrasynovial tendons may improve gliding of tendon graft and reduce adhesion postoperatively, compared with traditional grafts.

Animals↗
PubMed1995

A new porous surface modification technology for peritoneal dialysis catheters as an exit-site cuff to reduce exit-site infections.

Catheter exit-site infection continues to be a more common morbid event in patients undergoing peritoneal dialysis. Previous attempts to place a biointegration material at the next site have failed to reduce infection rates. This study reports the use of an innovative microporous silicone material placed as a cuff around the catheter at the exit site. The porous material has a pore-sized distribution that stimulates and facilitates capillary ingrowth into the pores. This capillary ingrowth prevents scar tissue formation, increases blood supply, and theoretically improves the immunological competence of the tissue at the vulnerable exit site. Twenty-five test catheters (12 using standard exit-site creation and 13 using the Moncrief-Popovich implantation technique) were implanted in a canine model. The exit-site infection rate in a canine model without the microporous material was 100% at 2 months. The corresponding results with the microporous material was 40% at 2 months. The majority of the test catheters showed progressive drying and healing at the exit site. Sixty percent of the catheters healed quickly and remained infection-free. Biointegration of the microporous material at the exit-site was demonstrated. Several exit site infections with the test catheters treated only with local therapy (without systemic or topical antibiotics) demonstrated progressive healing and secondary adequate biointegration. Because of these encouraging results, human studies were initiated, with the first human implant occurring in August, 1994. A 10-patient project is planned for the next year.

Animals↗
PubMed2001

Amphiphilic poly-N-vinylpyrrolidones: synthesis, properties and liposome surface modification.

Certain amphiphilic water-soluble polymers including amphiphilic derivatives of polyvinyl pyrrolidone (PVP) were found to be efficient steric protectors for liposomes in vivo. In this study, we have tried to develop synthetic pathways for preparing amphiphilic PVP and to investigate the influence of the hydrophilic/hydrophobic blocks on some properties of resulting polymers and polymer-coated liposomes. To prepare amphiphilic PVP with the end stearyl (S) or palmityl (P) residues, amino- and carboxy-terminated PVP derivatives were first synthesized by the free-radical polymerization of vinyl pyrrolidone in the presence of amino- or carboxy-mercaptans as chain transfer agents, and then modified by interaction of amino-PVP with stearoyl chloride or palmitoyl chloride, or by dicyclohexyl carbodiimide coupling of stearylamine with carboxy-PVP. ESR-spectra of the hydrophobic spin-probe, nitroxyl radical N-oxyl-2-hexyl-2-(10-methoxycarbonyl)decyl-4,4'-dimethyl oxazoline, in the presence of amphiphilic PVP demonstrated good accessibility of terminal P- and S-groups for the interaction with other hydrophobic ligands. Spontaneous micellization and low CMC values (in a low micromolar range) were found for amphiphilic PVP derivatives using the pyrene method. In general, S-PVP forms more stable micelles than P-PVP (at similar MW, CMC values for S-PVP are lower than for P-PVP). It was found that amphiphilic PVP incorporated into negatively charged liposomes effectively prevents polycation(poly-ethylpyridinium-4-vinylchloride)-induced liposome aggregation, completely abolishing it at ca. 10 mol% polymer content in liposomes. Additionally, the liposome-incorporated PVP prevents the fluorescence quenching of the membrane-incorporated hydrophobic fluorescent label [N-(4-fluoresceinthiocarbamoyl)dipalmitoyl-PE] by the free polycation. PVP-modified liposomes were loaded with a self-quenching concentration of carboxyfluorescein, and their destabilization in the presence of mouse serum was investigated following the release of free dye. Amphiphilic PVP with MW between 1,500 and 8,000 provides good steric protection for liposomes. The degree of this protection depends on both polymer concentration and molecular size of the PVP block.

Animals↗
PubMed1996

Polymeric surface modifications of tantalum stents.

PURPOSE: To compare two kinds of polymer-coated tantalum stents with bare tantalum stents (control) to determine if the coatings can improve thromboresistance. METHODS: Twenty-seven Fontaine-Dake stents were balloon expanded in three 8-mm x 80-cm polytetrafluoroethylene (PTFE) grafts; 9 stents were bare tantalum (T); 9 were coated with polyetherurethane (PL); and 9 were coated with parylene (PA). There were 9 stents placed in each graft as follows: 3 tantalum, 3 polyetherurethane, and 3 parylene. In swine whose platelets had been radiolabeled with indium 111, the ends of each stented graft were connected to 14F femoral and venous sheaths to create an ex vivo fistula. Each graft was exposed to blood for 30, 60, and 120 minutes. At the end of each test period, the stented grafts were disconnected from the sheaths, flushed with saline until clear, and then flushed with formalin. The stents were removed from the grafts, and a radionuclide well counter recorded radionuclide counts from each stent type at each period of blood contact. These values were converted to platelet density per 1000 microns 2. Stents were then photographed and scanned with electron microscopy (EM) for qualitative analysis. Possible significant differences in platelet adhesion with the three types of stents (both between stent groups and within stent groups) were examined using a two-tailed Student's t-test. RESULTS: There were significantly fewer platelets adsorbed on PA versus T at all time periods (p < 0.005); on PL versus T at 60 and 120 minutes (p < 0.005); and on PA versus PL at 30 and 120 minutes (p < 0.0005). There was no significant difference in platelet density within each stent group (p = 0.1). Mean platelet density (number of platelets per 1000 microns 2 +/- SD) was as follows: at 30 minutes: T = 1891 +/- 965; PL = 373 +/- 193; and PA = 27 +/- 3; at 60 minutes: T = 6226 +/- 1621; PL = 1573 +/- 793; and PA = 1185 +/- 710; at 120 minutes: T = 5307 +/- 591; PL = 3164 +/- 318; and PA = 180 +/- 100. Gross inspection of the 120-minute groups demonstrated focal areas of thrombus on T, less on PL, and none on PA. Scanning EM demonstrated extensive platelet accumulation covering T at all time periods, less on PL, and even less on PA.

Animals↗
PubMed1975

Surface modifications evoked by antidiuretic hormone in isolated epithelial cells: evidence from lectin probes.

Epithelial cells (80-90% "granular" type) were isolated from urinary bladders of Bufo marinus and Rana catesbiana. The inhibitory effect of alpha-methyl-D-mannoside on fluorescein-labeled concanavalin A (Con A) binding to these cells indicates that they possess specific binding sites for Con A. The lectin also mediates adsorption of erythrocytes to these cells. Both Con A binding and Con A-mediated hemadsorption to epithelial cells are depressed at 4 degrees C, as compared with cells maintained at 22 degrees C. Elevation of temperature to 37 degrees C, however, enhances hemadsorption independently of alterations in lectin binding. Treatment of cells with antidiuretic hormone (ADH) at 22 degrees C followed by 15 min of incubation at 22 degrees or 37 degrees C before exposure of cells to Con A promotes increments in Con A-mediated hemadsorption, but not in lectin binding, at 22 degrees or 37 degrees C. These hormonal effects are not significant when hemadsorption is assayed at 4 degrees C. Treatment of cells with another octapeptide, angiotensin, elicits a small, but significant, increment in hemadsorption to epithelial cells which is likewise uninfluenced by quantitative changes in lectin binding. Collectively, these data and other independent observations suggest that treatment with octapeptide hormones acts to enhance the redistribution and aggregation of lectin-binding proteins in the membranes of granular epithelial cells from amphibian urinary bladder. Such changes, in turn, may contribute to the alterations in membrane transport properties which characterize the hormonal response.

Angiotensin II↗
PubMed1997

Nylon-Based Affinity Membranes: Impacts of Surface Modification on Protein Adsorption.

Nylon microfiltration membranes were activated with bisoxirane and formaldehyde at terminal amino groups and amide groups of the nylon polymer, respectively. Dextrans were covalently immobilized on these activated membranes to yield dextran-coated membrane matrices. Both procedures led to a significant reduction of hemoglobin adsorption; however, bisoxirane activation required additional cross-linking of dextran and a second dextran layer to yield comparable quality of dextran-coated membranes than formaldehyde activation. Formaldehyde activation was easiest and cheapest and resulted in membranes with highest dextran density and relatively lowest nonspecific hemoglobin adsorption. Dextrans of &Mmacr;w >/= 40,000 were required for bisoxirane-activated membranes, whereas dextrans of &Mmacr;w = 6000 were sufficient for formaldehyde-activated membranes. Both activation methods resulted in stable coatings at low and high pH; however, formaldehyde-activated membranes were unstable under strongly acidic conditions at pH < 3. Dextran coils were found responsible for the reduction of the hydraulic permeability but also for the high ligand densities obtained after immobilization of Cibacron Blue F3G-A (360 nmol/cm2) and iminodiacetic acid (400 nmol/cm2). The thermodynamics of protein adsorption on dye ligand affinity (DLA) membranes corresponded with chromatographic sorbents and dye ligand conjugates, with the dextran coating demonstrating similar structure than dextrans in solution. Protein adsorption took place in the extended coil structure of dextrans with binding capacities up to 730 µg/cm2 lysozyme on DLA membranes and 470 µg/cm2 concanavalin A on metal chelate affinity membranes. Copyright 1997 Academic Press.

Journal Article↗
PubMed1984

Cell surface modifications in the epithelium of rat ventral prostate during adaptation to in vitro conditions: an ultrastructural study.

Sequential changes in epithelial cells of collagenase-dissociated rat ventral prostate were studied by thin-section and freeze-fracture electron microscopy. Epithelial cells did not attach to the substrate for 48 h. Pelleted cells obtained 1, 24, and 48 h after dissociation were assigned to three categories depending on morphology and cellular associations. (a) Solitary epithelial cells degenerated as determined by extensive vacuolization in the cytoplasm and aggregation of intramembranous particles (IMP). (b) Epithelial clusters consisted of a homogeneous population of well-maintained, closely packed cells. Aggregation of IMP was minimal. Tight junctions that formed between cells at the periphery of the clusters appeared normal and provided an effective permeability barrier demonstrated by the exclusion of ruthenium red tracer. (c) Tissue fragments were comprised of varying combinations of epithelial, endothelial, and smooth muscle cells as well as fibroblasts and erythrocytes. Maintenance of tissue fragments was variable. Plasma membranes often displayed aggregated IMP and proliferated tight junctional strands. An effective permeability barrier was absent. After the 48 h "latent period," epithelial cells in the clusters lost interdependence, disassociated from one another, and attached to the substrate. These isolated cells, which did not display aggregated IMP, retained the ability to form an effective permeability barrier upon reaching confluency. During the first 48 h, epithelial cells did not tolerate solitary existence, yet as participants in clusters they were well maintained. After this interval, they no longer required interactions with neighbors in order to survive. These results indicate that under our experimental conditions, an adaptation period is required by prostatic epithelial cells. The enhanced quality of maintenance associated with epithelial clusters suggests that control over the internal microenvironment, provided by a tight junctional barrier, may be important during the initial period of adaptation in vitro.

Adaptation, Physiological↗
PubMed1995

Stabilization and surface modification of monoclonal antibodies by 'bi-layer encagement'.

A two step simple procedure for antibody stabilization in soluble form was developed. The antibody is first treated with low molecular weight polyaldehyde (polyglutaraldehyde). Following removal of non-bound polyaldehyde the antibody-polyaldehyde conjugate is crosslinked by polyamine (alkyl amine derivative of polyglutaraldehyde). Feasibility studies were successfully conducted employing monoclonal antibody raised against horseradish peroxidase as model system. The stabilized antibody preparation exhibited improved thermal stability, enhanced resistance to proteolytic digestion and higher 'specific binding activity' in ELISA test, without losing its capability to bind large antigen (enzyme) or being recognized by another antibody (goat anti-mouse IgG).

Antibodies, Monoclonal↗