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PubMed1990

Spectroscopic characterization of polyethyleneglycol modified superoxide dismutase: 1H NMR studies on its Cu2Co2 derivative.

Spectroscopic methods have been employed in order to understand the molecular basis of the decrease in enzymatic activity of the antiinflammatory enzyme copper-zinc superoxide dismutase (SOD) following the covalent binding of polyethyleneglycol (PEG) chains to the protein amino-groups. The PEG modification is a general method recently proposed to improve the therapeutic index of enzymes. 1H NMR spectra on the cobalt substituted PEG-modified SOD, Cu2Co2-PEG-SOD, have been recorded. The signals are quite broad with respect to the unmodified enzyme. This has been interpreted on the basis of the effect of molecular weight on the linewidth. The analysis has shown that the histidine hydrogens involved in metal binding at the enzyme active site are the same in both native and PEG-modified SOD. Similarly, circular dichroism and absorption spectra indicate that the overall conformation of the metal clusters is not perturbed upon modification. On the other hand, azide titration shows that the affinity constant of N-3 for SOD is largely reduced upon PEG modification (K = 154 M-1 and 75 M-1 for the native and modified SOD, respectively). These results indicate that the decrease in enzymatic activity upon surface modification with PEG is not caused by a perturbation of the active site geometry, but to a decrease in the channeling of the O2- ion towards the enzyme active site.

Circular Dichroism↗

PubMed1992

ESCA study on dental alloy surfaces modified by Ga-Sn alloy.

A new, simple surface modification method for adherend metals has been developed. It gives high bond strength and superior water durability to dental precious-metal alloys bonded with 4-META/MMA-TBB resin. However, there was no effect on the bonding of Ag-In-Zn alloy and base-metal alloys. In the present study, the alloy surfaces modified by the new method were analyzed by ESCA and SEM for determination of details of the modification effect. A new alloying layer containing Ga and Sn was formed on the precious-metal alloys. The main factor for excellent adhesion to be achieved was the formation of a very thin layer of Ga2O3 and SnO2, less than 1-2nm thick, on the alloy surface. A thicker modified layer, as formed on the Ag-In-Zn and Ni-Cr alloys, led to low bonding ability.

Acrylic Resins↗

PubMed1987

Post-testicular change in the reptile sperm surface with particular reference to the snake, Natrix fasciata.

Sperm surface changes occurring in the reptile Wolffian duct have been explored with particular references to the snake, Natrix fasciata. In the snake Wolffian duct there are several proteins not present in serum, the pattern of which changes in concert with the seasonal testicular cycle. Whereas testicular spermatozoa did not bind antibody to duct secretions, all Wolffian duct spermatozoa did so over both head and tail, according to immunofluorescence patterns. Thus, on entering the Wolffian duct, the entire surface of N. fasciata spermatozoa acquires one of more of the duct's secretory components. As indicated by immunofluorescence, immunoelectrophoresis, and immunodiffusion, epitopes on at least some molecules that bind to spermatozoa or that remain free in the duct fluid are shared with those in other Natrix species, but not in more distant reptiles (turtle, anole lizard), nor chicken, rat, or rabbit. In regard to glycoproteins, one prominent con A-reactive band was present in polyacrylamide gel electrophoresis (PAGE) of snake fluid and more were evident in fluid collected from the turtle duct. However, such lectin-reactive elements did not bind to spermatozoa as judged by an absence of any change in snake, turtle and lizard sperm lectin-binding patterns in passing from the testis into and through the Wolffian duct. In all, evidence from these and other species studied begins to suggest that the nature of the post-testicular sperm surface modification displayed in most vertebrates that fertilize internally may differ in sub-therian and therian groups, respectively. There appears to be a relative emphasis on glycosyl-rich surface elements in the latter. The possible significance of these changes for sperm function in the different groups is discussed briefly in terms of sperm survival/storage, as well as capacitation and sperm binding to the zona.

Animals↗

PubMed1971

Studies on gonococcus infection. I. Pili and zones of adhesion: their relation to gonococcal growth patterns.

The four colony types of several different strains of gonococci were isolated by selective transfers on agar. These colony variants differed in the degree of autoagglutination which occurred when they were grown in fluid medium. It was found that this clumping behavior was related to the colonial type, with type 2 isolates exhibiting the greatest autoagglutination followed by types 3, 1, and 4. Electron microscopic examination of thin sections indicated that the clumping in fluid medium was mediated by peculiar zones of adherence of the outer membranes of gonococci. These resembled the gap junctions seen in animal cell systems but differed in that the gonococcal membranes involved in the zone of adherence did not bear typical surface modifications. Electron microscopic study of negatively stained specimens of gonococci revealed that pili with a diameter of approximately 85 A and a length up to 4 micro were present on the surfaces of all type 1 and type 2 gonococci examined, and were not seen on any type 3 or 4 gonococci. The consistent presence of pili on type 1 and type 2 gonococci which are virulent colony forms and the lack of pili on avirulent colony types 3 and 4 suggests a relationship between the gonococcal pili and pathogenetic potential of the organisms.

Agar↗

PubMed2026

Single antiplatelet therapy and tirofiban bridged with surface modified flow diverters for ruptured blood blister-like aneurysms: single center experience and systematic review.

BACKGROUND: Blood blister-like aneurysms (BBAs) of the internal carotid artery are rare but high risk lesions that frequently re-rupture due to their fragile structure and dissecting pathology. Treatment is particularly challenging in ruptured cases, given the risks associated with dual antiplatelet therapy. Recent advancements in flow diverter stents (FDSs) with surface modifications, and the use of single antiplatelet therapy (SAPT), offer a potential alternative strategy. METHODS: We conducted a retrospective review of 17 patients with ruptured internal carotid artery BBAs treated with surface modified FDS under SAPT (ticagrelor or prasugrel) bridged periprocedurally with intravenous tirofiban. All procedures were performed within the acute phase of subarachnoid hemorrhage. Clinical, radiographic outcomes, and procedure related complications were evaluated. RESULTS: Among 17 patients, 94.1% achieved complete angiographic occlusion, and 76.5% attained favorable clinical outcomes (modified Rankin Scale score ≤2). No aneurysm rebleeding or device related ischemic events occurred. A total of 11 patients underwent external ventricular drainage or ventriculoperitoneal shunting without discontinuing SAPT, and no hemorrhagic complications were observed. A literature review incorporating seven additional series identified a total of 42 FDS plus SAPT treated BBA cases, with similar safety and efficacy profiles. CONCLUSIONS: Surface modified FDS with SAPT and tirofiban bridging appears to be a promising treatment option for ruptured BBAs, offering high occlusion rates with minimal thromboembolic and hemorrhagic complications. Larger prospective studies are needed to validate these findings.

Humans↗

PubMed1979

Surface morphology of macrophages in the regressing corpus luteum, as revealed by scanning electron microscopy.

Activated macrophages phagocytize moribund luteal cells and thus play a central role in the postpartum regression of corpora lutea in guinea pigs (Paavola, '79). When viewed by transmission electron microscopy (TEM), these luteal macrophages exhibit many surface protrusions. To characterize more fully the nature and extent of these evaginations, as well as to gain further understanding of phagocytes in their natural surroundings, luteal macrophages were studied in situ by scanning electron microscopy of regressing corpora lutea. Correlated TEM was carried out to confirm the identity of the various cell types. Even in low power scanning electron micrographs, macrophages are consipicuous, and can be readily distinguished from luteal cells by their surface topography. Luteal cell surfaces bear low ridge-like folds and sparse microvilli. In contrast, macrophages characteristically exhibit highly developed surface projections, the most common of which are knob-like or clubbed processes of varying size and shape. Other distinctive surface modifications displayed by luteal macrophages include long, slender filopodia, and well developed pseudopodia. These processes generally have an uneven distribution over the cell; thus, luteal macrophages may appear polarized with regard to surface activity. Both filopodia and pseudopodia occur in close contact with luteal cell surfaces. In addition, occasional luteal macrophages have surfaces that are covered with large, crater-like depressions. The phagocytosis of cells and cellular debris by macrophages was also observed. In summary, the highly pleomorphic surface activity of luteal macrophages appears to be correlated with their role in the removal of senescent luteal cells.

Animals↗

PubMed1989

Evaluation of blood compatibility of PEO grafted and heparin immobilized polyurethanes.

To develop better blood compatible polymer for long-term biomedical applications, poly(ethylene oxide) (PEO) grafted and/or heparin immobilized polyurethanes (PUs) were made by novel surface modification. Their blood compatibilities were investigated using in vitro platelet adhesion test, APTT, PT, immobilized heparin bioactivity measurement, and ex vivo rabbit A-A shunt test. In platelet adhesion tests, PEO grafted PU surfaces, compared to PU control, displayed very little platelet adhesion and activation, and this effect was more significant as the molecular weight of PEO increased from 200 to 2000. Also, the degree of platelet adhesion was lower in the heparinized PU surfaces than that of PU control. The immobilized heparin showed a greater effect on intrinsic blood coagulation factors than on extrinsic ones, whereas the PU-PEO surface was independent of blood coagulation factors. Lowering both in vitro platelet adhesion and activation led to a prolongation in the ex vivo occlusion time. In particular, the heparinized PU-PEO surfaces displayed enhanced blood compatibility due to the synergistic effects of PEO and heparin.

Animals↗

PubMed1989

Non-enzymic post-translational modification of proteins in aging. A review.

Various non-enzymic post-translational changes to proteins occur in vivo and some of these progress with aging. These changes are reviewed and linked to a number of age-related diseases, and to alterations in the charge distribution on protein surfaces. Modification by cyanate and by glucose 6-phosphate causes a partial unfolding of proteins, with loss of tertiary structure but retention of secondary structure. These products are reminiscent of the intermediate state observed during folding and unfolding of some proteins.

Aged↗

PubMed1976

Surface hydroxylation of styrene-butadiene-styrene block copolymers for biomaterials.

This work pertains to the development of high strength elastomers potentially useful as nonthrombogenic cardiovascular prostheses. Triblock copolymers of the styrene-butadiene-styrene type have been subjected to surface hydroxylation which provide reactive sites at the surface for the subsequent coupling of heparin while retaining the unique mechanical properties of the SBS copolymers. Curves of hydroxyl content versus the copolymer film thickness demonstrate the effect of swelling in the surface region on the product distribution and on the time dependence of the hydroxylation process. In addition, the effect of time, temperature, and the composition of the reaction bath on the diffusion/reaction process is shown. Finally, the general applicability of this surface modification scheme to the development of biomaterials is discussed.

Adsorption↗

PubMed1992

Low fluorescence background electroblotting membrane for DNA sequencing.

A low fluorescence background polypropylene (PP) membrane has been developed for ultimate use as an electroblotting membrane in DNA sequencing based on fluorescence detection. The DNA binding capacity of this membrane is improved by a surface modification using radio frequency plasma discharge (RFPD) in ammonia gas. The RFPD operational parameters are evaluated both in terms of membrane nitrogen content and in terms of the product's capacity for binding radioisotope-labeled DNA fragments. The surface morphologies of the derivatized membranes are examined by scanning electron microscopy; their mechanical and electrical properties, which are important for the subsequent sequencing procedures, are likewise established. Due to the goal of developing a membrane suitable for multiplex processing, in which the electroblotted DNA must withstand dozens of hybridization/stripping cycles, special attention is given the covalent attachment of DNA to the membrane. The modified PP membrane is evaluated in a multiplex sequencing application using radioisotope-labeled DNA probes, and found to yield somewhat better binding of a given amount of electroblotted DNA than the commonly used GeneScreen membrane. A tenfold repetition of the probing indicates little loss of signal; the membrane-bound DNA is stable upon storage and shows no detectable loss in probing efficiency after one month.

Base Sequence↗

PubMed1986

The cell surface of Mycobacterium avium-intracellulare and M. scrofulaceum: effect of specific chemical modifications on cell surface charge.

Cells of representative strains of the Mycobacterium avium-intracellulare and Mycobacterium scrofulaceum (MAIS) group had mixed cationic/anionic surfaces, unlike the surfaces of other mycobacteria. The pH electrophoretic mobility curves demonstrated that all MAIS strains examined had a net negative mobility above pH 3.5-4.5 and a positive mobility below that pH range. Based upon the pH electrophoretic mobility of cells following chemical or enzymatic treatment, it appears that the surface molecules contributing to charge are amino groups (primarily contributed by proteins), carboxyl and phosphate (and phosphodiester-linked) groups.

Cell Membrane↗

PubMed1976

Surface labelling of senescent chick fibroblasts by lactoperoxidase-catalysed iodination.

Cell surface of chick fibroblasts were labelled by a short treatment with 125I in presence of lactoperoxidase. A glycoprotein (220,000 molec. wt) was iodinated and was present in a more exposed position or in greater amounts at the surface of old phase III cells compared to young phase II cells. The findings extend our previous observations on cell surface modifications in in vitro senescing fibroblasts.

Aging↗

PubMed1978

Effects of albumin on the phagocytosis of polystyrene spherules by rabbit polymorphonuclear leucocytes.

Polystyrene latex spherules are rapidly phagocytized by polymorphonuclear leucocytes. Surface modifications of the latex spherules can lead to an inhibition of phagocytosis, and the purpose of this study was to analyse in particular inhibition by bovine and human serum albumin. It can be shown that albumin is bound much more strongly by the PSL particle surface than by the cell surface. Furthermore, a correlation was established between the extent to which the particle surface is covered and the extent of phagocytosis inhibition. In the binding of albumin to the particle surface ionic as well as hydrophobic interactions play a role. As a result, the particle acquires a negatively charged hydrophilic coating which effectively diminishes the number of effective cell-particle collisions leading to engulfment.

Animals↗

PubMed1989

Calcium phosphate mineralization.

Although it is often assumed that the thermodynamically most stable hydroxyapatite is a suitable prototype for biological minerals, it is now generally accepted that other phases such as dicalcium phosphate dihydrate and octacalcium phosphate as well as defect apatites and carbonated apatites may participate. The Constant Composition kinetics method, has been used to show that defect apatites may be formed with non-stoichiometric coefficients that depend upon the pH of the growth medium. Important factors in analyzing these experiments are the initial surface modification and ion exchange processes involving hydrogen and calcium ions following inoculation of the supersaturated solutions. Proteins and other macromolecules which may inhibit the rate of growth of calcium phosphates in supersaturated solutions are able to enhance the nucleation of these phases when immobilized on inert surfaces.

Apatites↗

PubMed1992

Fibrinous reaction on implanted intraocular lenses. A comparison of conventional PMMA and heparin surface modified lenses.

We studied the fibrinous reaction after intraocular lens (IOL) implantation in the posterior chamber of cynomolgus monkeys. In 50% of the eyes, we implanted an IOL made of conventional poly-(methyl methacrylate) (PMMA); in the remaining eyes we implanted a PMMA IOL with a heparin modified surface. Two, 4, 8, and 18 weeks after surgery the eyes were examined by slitlamp for fibrinous reactions on and around the IOL surface. At weeks 4, 8, and 18 there was a marked decrease in fibrinous reaction in the eyes with a heparin surface modified IOL. The results of this study accord with earlier findings that heparin surface modification improves the biocompatibility of the IOL.

Animals↗

PubMed1988

The use of silicone/polyurethane graft polymers as a means of eliminating surface cracking of polyurethane prostheses.

The long-term biodegradation of various polyurethanes with and without surface modifications was evaluated by implanting small porous filamentous patches of these materials subcutaneously in the backs of dogs for one month. Data were compared to those obtained with spun polyurethane vascular grafts of similar materials implanted in the aorto-iliac position in dogs. The extremely high surface area of approximately 7 m2/cm3 of these porous filamentous patches provided numerous sites for surface cracking and the very fine filaments (10 microns in diameter) provided an easily identifiable structure to study the cracking phenomenon. Results from numerous one month implants clearly demonstrated that the subcutaneous implant model effectively reproduced the biodegradation behavior observed in vascular graft implants. The degradation was most pronounced in the softer Shore 80A polyurethanes and less pronounced in the harder 55D and 75D polyurethanes. The degradation could not simply be stopped by stress annealing the polyurethane and the degradation did not require the presence of metallic ions. Antioxidants, surface adsorbed albumin, poly(2-hydroxyethyl-methacrylate) grafting, silicone copolymerization, tetrafluoroethylene plasma discharge and the addition of urea linkages to the polymer were also shown to be ineffective in stopping the biodegradation process. In contrast, covalent bonding or grafting of silicone polymer to the surface of the urethane successfully inhibited the biodegradation process.

Animals↗

PubMed1991

Covalent immobilization of proteins on to the surface of poly(vinyl alcohol) hydrogel.

Covalent immobilization of cell-adhesive proteins such as collagen and fibronectin on to the surface of poly(vinyl alcohol) hydrogel was investigated by using diisocyanates, polyisocyanates, and cyanogen bromide. It was found that 0.5 and 12 micrograms/cm2 of collagen were immobilized on to the surface by using hexamethylene diisocyanate and cyanogen bromide, respectively. The big difference in the graft amount between the two methods was ascribed to the different reaction media employed for the surface modifications; toluene for the reaction with hexamethylene diisocyanate and water for the reaction with cyanogen bromide.

Collagen↗

PubMed1985

Hydrophilic albumin microspheres.

A method has been developed for preparing unique hydrophilic HSA/MS. Important aspects of this synthesis include addition of the cross-linking agent (glutaraldehyde) in the organic phase and use of concentrated polymer solutions as dispersion media. The polymer solutions afford excellent steric stabilization of aqueous albumin microdispersions for microsphere synthesis. Steric stabilization of dispersions by polymer solutions was shown to be a function of polymer concentration and molecular weight. The HSA/MS prepared by this method are hydrophilic and easily dispersed in a variety of aqueous media without surfactants. Chemical modifications are easily accomplished using available reactive aldehyde groups remaining after cross-linking. Although hydrophilicity of the microspheres is advantageous for many drug delivery applications, in some instances (such as the use of MS in adjuvant immunotherapy or vaccine preparations) some hydrophobicity may be desirable. For this purpose, surface modifications to produce controlled hydrophobicity is easily achieved by covalent coupling with appropriate reagents (e.g., fatty amines). Adriamycin was bound to HSA/MS by both physical association (to 18 wt%) and covalent binding (also to 18 wt%). In vitro release of drug was measured for the MS using a dynamic flow method. Two distinct release mechanisms could be achieved depending on the type of drug bonding used: slow by hydrolytic degradation of covalent bonds and fast by release of physically adsorbed drug. This new and versatile synthesis of hydrophilic HSA/MS opens up many new opportunities for producing chemically modified MS containing high concentrations of therapeutic agents. Use for immunodiagnostic and adjuvant compositions is also suggested.(ABSTRACT TRUNCATED AT 250 WORDS)

Capsules↗