PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “surface modification”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed1996

Blood-pool imaging using technetium-99m-labeled liposomes.

UNLABELLED: This study evaluated two 99mTc-liposome formulations as potential blood-pool agents in comparison with standard 99mTc-red cells and 99mTc-human serum albumin (HSA). METHODS: Liposomes with no surface modification or coated with polyethylene glycol (PEG) were labeled with 99mTc using the lipophilic chelator, HMPAO. Autologous red cells were labeled with 99mTc using in vitro or in vivo techniques. Technetium-99m-HSA was supplied commercially. Rabbits were injected intravenously with 99mTc-liposomes, 99mTc-red cells or 99mTc-HSA. Static images were acquired and blood samples collected. RESULTS: Technetium-99m-liposome images showed prominent blood-pool activity compared to lung and liver activities, which were similar to those acquired for 99mTc-red cells, but better than 99mTc-HSA. Heart-to-lung ratios were not significantly different between 99mTc-liposome formulations or for either formulation compared to 99mTc-red cells. The ratios were higher, however, than for 99mTc-HSA. Heart-to-liver ratios were higher for PEG 99mTc-liposomes than they were for neutral 99mTc-liposomes and 99mTc-HSA, but were not significantly different than 99mTc-red cells. Bladder activities for both 99mTc-liposome formulations were 3-6 times lower than for the other agents. PEG 99mTc-liposomes remained in circulation 1.6 times longer than any of the other agents. CONCLUSIONS: Technetium-99m-liposomes, independent of surface modification, had excellent circulation persistence and in vivo stability when compared to 99mTc-red cells and 99mTc-HSA. PEG 99mTc-liposomes performed better than neutral 99mTc-liposomes due to lower liver background activity. Advantages of PEG 99mTc-liposomes compared to 99mTc-red cells include: (a) only one venipuncture, (b) little exposure to patient's blood, (c) excellent in vitro and in vivo stability and (d) lack of drug interference.

Animals↗
PubMedDate not supplied

The efficacy of silver-ion implanted catheters in reducing peritoneal dialysis-related infections.

BACKGROUND: Dialysis-related infections are the commonest cause of catheter loss and transfer to hemodialysis. Surface modifications of the catheter that reduce infections are of major importance. OBJECTIVE: The efficacy of silver-ion treated catheters in reducing dialysis-related infections was tested. METHODS: The study design was a prospective, randomized controlled trial. Patients were implanted with either a silver-treated study catheter or a control catheter. Prospective collection of data included infectious complications and catheter survival. RESULTS: The subject groups were comprised of 67 silver-treated catheters and 72 control catheters. Demographic characteristics of the study and control groups were equal. Exit-site infection rates for the study group and control group (0.52 and 0.45 episodes/patient-year of dialysis respectively) were not different by Poisson regression analysis (p > 0.4). Peritonitis rates were identical for the two groups (0.37 episodes/patient-year) and were not different by Poisson analysis (p > 0.9). Antibiotic-free intervals between infections for the study and control groups were not significantly different for exit-site infections (p = 0.58), peritonitis (p = 0.44), or both infections combined (p = 0.47). Actuarial analyses showed no differences between the groups in the probability of remaining free of exit-site infection (p > 0.2) or peritonitis (p > 0.7). Similarly, catheter survival was not significantly different between the groups (p > 0.6). CONCLUSION: Surface modification of catheters with ion beam implantation of silver produced no clinical effect with respect to reducing dialysis-related infections.

Adult↗
PubMed2006

Soft tissue around three different implant types after 1.5 years of functional loading without oral hygiene: a preliminary study in baboons.

The purpose of this study was to determine the peri-implant soft tissue dimension (PSD) and peri-implant bone level (BL) of dental implants with different designs and surface modifications after functional loading without oral hygiene. Three types of dental implants were placed in the posterior jaws of adult baboons, three of the same design per quadrant, and fitted with fixed partial dentures. After 1.5 years of functional loading and plaque accumulation, all implants showed severe peri-implant mucositis and comparatively high BL. A histomorphometric evaluation of the sulcus depth (SD), the dimension of the junctional epithelium (JE) and the connective tissue contact (CTC) resulted in no significant differences between the three implant designs, neither in the maxilla nor in the mandible (P>0.05). The sum of SD, JE and CTC forming the PSD was nearly the same in the maxilla (commercially pure titanium, CpTi: 3.5 mm 2.9/4.1 confidence interval (CI); titanium plasma sprayed (TPS): 3.5 mm 2.9/4.2 CI; sand blasted acid-etched (GBAE): 3.2 mm 2.7/3.9 CI) and in the mandible (CpTi: 3.2 mm 2.6/3.8 CI; TPS: 3.2 mm 2.6/3.8 CI; GBAE: 3.2 mm 2.7/3.9 CI; P>0.05). There was no difference in BL around the three implant designs (maxilla: CpTi: 0.9 mm 0.5/1.6 CI; TPS: 0.9 mm 0.5/1.5CI; GBAE: 0.9 mm 0.5/1.6 CI; mandible: CpTi: 0.8 mm 0.5/1.2 CI; TPS: 0.6 mm 0.4/0.9 CI; GBAE: 0.7 mm 0.5/1.1 CI; P>0.05). Overall, the data presented did not show any significant differences in peri-implant soft tissue conditions in baboons. Moreover, plaque accumulation and propagation of peri-implant mucositis after 1.5 years of functional loading was not influenced by implant design and surface modifications in baboons.

Acid Etching, Dental↗
PubMed1997

Reduced plaque accumulation on hydrocarbon thin film deposited on restorative acrylic polymers.

The deposition of a thin polymeric film from ethylene plasma was used to modify the surface properties of acrylic teeth, commonly used in the dental practice for crown and bridge restorations. The effects of the surface modification process on the surface composition, morphology, and energetics were evaluated by electron spectroscopy for chemical analysis, atomic force microscopy, and contact angle measurement respectively. Plaque accumulation on the plasma-coated and untreated material was evaluated in in vivo experiments, in which the same patient received conventional and plasma-coated restorations. The hydrocarbon-like surface of the plasma-coated restoration remained remarkably free from plaque, even in the absence of brushing. On the other hand, plaque accumulation was observed on the unmodified restoration. Results are discussed according to recent theories on bioadhesive phenomena.

Acrylates↗
PubMed2005

Surface derivatization of poly(p-phenylene terephthalamide) fiber designed for novel separation and extraction media.

The surface derivatization of poly(p-phenylene terephthalamide) fiber was studied. The obtained surface-derivatized filaments were packed into a fused-silica capillary to evaluate its surface characteristics by using GC. As the stationary phase for GC the surface-derivatized fibers showed higher retention for alkanes and alkylbenzenes than that with the untreated Kevlar fiber. The improvements on the retention power and the peak shape were observed on the benzyl-modified fibrous stationary phase. The derivatized fibrous materials were also evaluated as the extraction medium in fiber-in-tube SPE, and the effect of the surface modification on the extraction power was compared to the parent fiber. The results indicated that the modified fiber possessed a higher extraction power than the untreated fiber. Based on the facts, the successful modification of the fiber surface was estimated.

Journal Article↗
PubMed2001

Protein Adsorption onto Zirconia Modified with Terminally Grafted Polyvinylpyrrolidone.

The potential effectiveness of poly(vinyl pyrrolidone) (PVP) as a zirconia surface modifier for protein adsorption reduction was investigated using lysozyme (LYS). The relatively small size of LYS (45 x 30 x 30 Å) allowed for testing the adequacy of the graft polymerization method for producing a dense surface chain coverage to exclude LYS from direct interaction with the zirconia surface. The study demonstrated that a PVP brush layer is capable of reducing lysozyme adsorption. Overall, the maximum adsorption capacity decreased (by up to about 76%) due to surface modification with increasing polymer/silane surface coverage ratio (mol/mol). Adsorption reduction, due to protein exclusion from the surface by the tethered polymer layer, increased significantly when the distance between surface chains was less than the large axis of LYS (i.e., 45 Å). The present results are encouraging and suggest further consideration of polymer-modified ceramic surfaces for reducing fouling of ceramic membranes during protein ultrafiltration and producing ceramic biocompatible surfaces for biomedical applications. Copyright 2001 Academic Press.

Journal Article↗
PubMed1995

Modification by surface association of antimicrobial susceptibility of bacterial populations.

In the majority of natural situations in which bacteria are found, they are associated with and attached to surfaces. In the presence of moisture and nutrients, they grow to form extensive bacterial films which are often enveloped within copius exopolymeric matrices. Biofilms are ubiquitous to many different situations in industry, the environment and medicine. Their presence can be either beneficial or more commonly detrimental to such systems. In this respect, biofilm populations possess physiological properties distinct from those of unattached, planktonic bacteria. Moreover, it is generally accepted that bacteria growing within a biofilm are more resistant to antimicrobial agents than their planktonic counterparts. However, although the consequences of attachment to antimicrobial resistance have been known for many years, the mechanistic bases for such effects have still to be fully elucidated. In this article the nature of different resistance mechanisms, including those of the exopolymeric matrix, environmental modulation, attachment-specific physiologies and quorum sensing are reviewed.

Bacteria↗
PubMed1975

Studies on tetrahymena membranes. Modification of surface membrane lipids by replacement of tetrahymanol by exogenous ergosterol in Tetrahymena pyriformis.

Tetrahymena pyriformis WH-14 cells were grown in the medium supplemented with ergosterol (1 mg/100 ml) and the effects of replacement of tetrahymanol by ergosterol upon the lipid composition in the surface membranes (cilia and pellicles) were examined. 1. By scanning and freeze-etch electron microscopy it was suggested that exogenous ergosterol would be inserted into the lipid regions in the surface membranes. Although freeze-etched faces of filipin-treated membranes containing the native tetrahymanol showed a random distribution of 85-a protein particles, the ergosterol-replaced membranes after the same polyene treatment revealed the marked ultrastructural alterations on the fracture faces. 2. The replacement of tetrahymanol in membranes by ergosterol induced a profound alteration in the phospholipid class composition and a marked increase in phosphatidylethanolamine with a compensatory decrease in phosphatidylcholine and 2-aminoethylphosphonolipid. 3. There are significant and quantitative but not qualitative changes in the fatty acid composition of total lipids from the ergosterol-replaced membranes. There are also increases in saturated and decreases in unsaturated fatty acids. Phosphatidylethanolamine acyl chains particularly become more saturated, as compared with two other phospholipids, in ergosterol-replaced pellicles. This increase in saturation is due to an appreciable increase in C14:0, C16:0 and iso-C17:0, and a decrease in C18:1(delta9), C18:2(delta9,12) and C18:3(delta6,9,12). 4. These results suggest that profound alterations in phospholipids as well as in their fatty acyl chains are required to modify the overall membrane lipid composition for the maintenance of proper membrane fluidity. Our data would also support the thesis that polat head groups are involved in the membrane lipid organization and that sterols interact selectively with phospholipid molecules containing the appropriate fatty acyl chain composition in biological membranes.

Acetates↗
PubMed1986

Experimentally induced modifications in surface morphology of Ehrlich ascites tumor cells.

Observations with scanning electron microscopy /SEM/ were carried out on Ehrlich ascites tumor /EAT/ cells incubated 2 to 4 h at 37 degrees C in hyperosmotic media in the presence and in the absence of serum. It was found that the cells even if maintain spherical shape show significant differences in the architecture of their surface. A need for control observations with SEM of cell surface morphology in biochemical and biophysical research concerning plasma membrane functions and properties is pointed out.

Animals↗
PubMed2004

The peculiarities of homogeneous nucleation of reactive Cu0 colloidal particles in the presence of functional oligoperoxides.

A method is proposed that combines the stage of formation of colloidal metal and metal-oxide particles with the stage of their surface modification by functional surface-active oligoperoxides (FSAP), which are sorbed irreversibly. Investigation of copper particle homogeneous nucleation kinetics witnesses the significant influence of supermolecular micelle-like structures formed by FSAP in solution on the reduction rate of Cu2+ cations caused by a phenomenon analogous to micellar catalysis. The rate constants of copper reduction in different local zones of the process have been determined. Particle homogeneous nucleation kinetics in the presence of surface-active oligoperoxides has been found to correspond to the main regularities of the Michaelis-Menten equation describing micellar catalysis. The carrying out of copper particle formation in distinct zones correlates well with the particle size distribution. The presence of reactive ditertiary peroxidic fragments on the particle surface as a result of FSAP sorption confers reliable protection from oxidation, hydrophobicity, and ability to form free radicals and participate in elementary stages of radical processes.

Journal Article↗
PubMed2004

Modification of surface crystal formation on mother crystal by additive molecules.

Additive molecules and excess reactant species (NaOH and NH4F) in NaF crystallization were used to control surface crystal formation on a mother crystal. When the surface integration was inhibited or bulk diffusion facilitated, more surface crystals were found on the mother crystal due to an increase in the interfacial supersaturation on the crystal. The inclusion of KCl as an additive and increases in the reactant concentration and agitation speed resulted in a higher population of surface crystals on the mother crystal, because surface integration was inhibited. However, surface crystal formation was suppressed by the polymer gelatin due to retardation of the bulk diffusion by the gelatin layer formed around the crystal. In addition, surface crystal formation significantly changed according to the feeding mode, and the excess species of NaOH originating from the NH4F feeding mode were more effective in facilitating surface crystal formation than the excess species of NH4F coming from the NaOH feeding mode due to the smaller ionic radii of NaOH than of NH4F.

Journal Article↗
PubMed2006

Surface chemical studies on selective separation of pyrite and galena in the presence of bacterial cells and metabolic products of Paenibacillus polymyxa.

Selective separation of pyrite and galena from mixture of the two minerals was achieved through interaction with cells and metabolic products from a culture of Paenibacillus polymyxa. Adsorption of cells and metabolic products onto minerals and electrokinetic studies of minerals after interaction with cells and metabolic products were carried out to examine the resulting surface modification on the mineral surfaces. Flocculation and flotation techniques were successfully applied in the selective separation of minerals after bacterial interaction. The effect of varying conditions for production of extracellular polysaccharides and protein provided an insight into the possible mechanism involved in microbially induced flocculation and flotation of pyrite and galena.

Bacillus↗
PubMed2005

Modification of surface properties of Lentinus sajor-caju mycelia by physical and chemical methods: evaluation of their Cr6+ removal efficiencies from aqueous medium.

The hexavalent chromium biosorption onto untreated and heat-, acid- and alkali-treated Lentinus sajor-caju mycelia were studied from aqueous solutions. The particles sizes of the fungal mycelia ranged from 100 to 200 microm. The effect of pH, temperature, biosorbent dose, initial concentration of chromium ions, contact time parameters were investigated in a batch system. Biosorption equilibrium was established in about 4 h. The surface charge density of the fungal preparations varied with pH, and the maximum absorption of chromium ions on the fungal preparations were obtained at pH 2.0. The biosorption of chromium ions by the tested fungal preparations increased as the initial concentration of chromium ions increased in the medium. The maximum biosorption capacities of the untreated and heat, HCl- and NaOH-treated fungal biomass were 0.363, 0.613, 0.478 and 0.513 mmol Cr6+ per gram of dry biomass, respectively. The correlation regression coefficients and the Langmuir constant values show that the biosorption process can be well defined by Langmuir equation. The chromium adsorption data were analysed using the first- and the second-order kinetic models. The first-order equation is the most appropriate equation to predict the biosorption capacities of all the fungal preparations. In addition, the polarity and surface energy of the untreated and all the modified biomass film preparations were determined by contact angle measurement. All the tested fungal biomass preparations could be regenerated using 0.1 M NaOH solution.

Adsorption↗
PubMed1999

Molecular barriers to biomaterial thrombosis by modification of surface proteins with polyethylene glycol.

For cardiovascular biomaterials, thrombosis, thromboembolism and vascular graft occlusion are believed to be precipitated by the adsorption of proteins containing adhesive ligands for platelets. Polyethylene-glycol-diisocyanate(PEG-diisocyanate, 3400 MW) may potentially react with protein amines to form molecular barriers on adsorbed proteins on biomaterials, thereby masking adhesive ligands and preventing acute surface thrombosis. To test this notion, PE, PTFE, and glass microconduits were pre-adsorbed with fibrinogen and treated with PEG-diisocyanate, non-reactive PEG-dihydroxyl, or remained untreated. Following perfusion of 111In-labeled platelets in whole human blood for 1 min (wall shear rate = 312 s(-1)), PEG-diisocyanate treated surfaces experienced 96%(PE), 97%(PTFE) and 94% (glass) less platelet deposition than untreated surfaces. Similar reductions were seen for PEG-diisocyanate versus PEG-dihydroxyl treatment. Low shear perfusions of plasma for one hour prior to blood contact did not reduce the inhibitory effect of PEG-diisocyanate. Platelet adhesion onto collagen coated glass coverslips and platelet deposition onto preclotted Dacron was also reduced by treatment with PEG-diisocyanate (93 and 91%, respectively). Protein-reactive PEG may thus have utility in forming molecular barriers on surface associated proteins to inhibit acute thrombosis on cardiovascular biomaterials.

Adsorption↗
PubMed1998

Molecular barriers to biomaterial thrombosis by modification of surface proteins with polyethylene glycol.

For cardiovascular biomaterials, thrombosis, thromboembolism and vascular graft occlusion are believed to be precipitated by the adsorption of proteins containing adhesive ligands for platelets. Polyethylene-glycol-diisocyanate (PEG-diisocyanate, 3400 MW) may potentially react with protein amines to form molecular barriers on adsorbed proteins on biomaterials, thereby masking adhesive ligands and preventing acute surface thrombosis. To test this notion, PE, PTFE, and glass microconduits were pre-adsorbed with fibrinogen and treated with PEG-diisocyanate, non-reactive PEG-dihydroxyl, or remained untreated. Following perfusion of 111In-labeled platelets in whole human blood for 1 min (wall shear rate = 312 s(-1)), PEG-diisocyanate treated surfaces experienced 96% (PE), 97% (PTFE) and 94% (glass) less platelet deposition than untreated surfaces. Similar reductions were seen for PEG-diisocyanate versus PEG-dihydroxyl treatment. Low shear perfusions of plasma for 1 h prior to blood contact did not reduce the inhibitory effect of PEG-diisocyanate. Platelet adhesion onto collagen-coated glass coverslips and platelet deposition onto preclotted Dacron were also reduced by treatment with PEG-diisocyanate (93 and 91%, respectively). Protein-reactive PEG may thus have utility in forming molecular barriers on surface-associated proteins to inhibit acute thrombosis on cardiovascular biomaterials.

Adsorption↗
PubMed1999

Modification of surfaces with cell adhesion peptides alters extracellular matrix deposition.

The goal of the current study was to evaluate matrix protein synthesis by cells cultured on materials that had been modified with cell adhesion ligands. We examined the effects of surface peptide density and of peptides with different affinities on the extracellular matrix production of smooth muscle cells, endothelial cells and fibroblasts. While initial adhesion was greatest on the higher density peptide surfaces, all cell types exhibited decreased matrix production on the more highly adhesive surfaces. Similarly, when different peptides were evaluated, matrix production was the lowest on the most adhesive surface and highest on the least adhesive surface. These results suggest that extracellular matrix synthesis may be regulated, to some extent, by signal transduction initiated by adhesion events. This may pose limitations for use of bioactive materials as tissue engineering scaffolds, as matrix production is an important aspect of tissue formation. However, it may be possible to increase matrix production on highly adhesive surfaces using exogenous factors. TGF-beta was shown to increase matrix production by both smooth muscle cells and endothelial cells.

Animals↗