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At least 1,621 records · Page 90Linked to original sources

PubMed2000

Effect of heparin-surface-modified intraocular lenses on postoperative inflammation after phacoemulsification: a randomized trial in a United States patient population. Heparin-Surface-Modified Lens Study Group.

OBJECTIVE: To compare postoperative inflammation occurring with heparin-surface-modified (HSM) versus non-HSM polymethyl methacrylate intraocular lenses (IOLs) after phacoemulsification. DESIGN: Randomized, double-masked, multicenter, parallel trial. PARTICIPANTS: A total of 367 patients, consisting of routine (n = 220), glaucoma (n = 58), and diabetes (n = 89) patients, from eight US medical centers. METHODS: Patients were observed for 1 year after phacoemulsification and lens implantation (week 1, months 1, 3, 6, 12). MAIN OUTCOME MEASURES: Primary measures of postoperative inflammation defined as the presence of giant cells on the lens surface via specular micrography and cellular deposits via slit-lamp examination. RESULTS: The cross-sectional analyses showed that consistently fewer routine patients with HSM lens implants had giant cells on the IOL than those with non-HSM lens implants across all follow-up visits. The statistical significance (P < 0.05) was observed at all visits except month 12 for routine patients. The diabetes patients also demonstrated the same giant cell difference, and the statistical significance was observed at all visits including month 12. A similar trend was also observed in the glaucoma patients, with statistical significance only at the 3-month visit. For cell deposits, significant differences in favor of the HSM lens (P < 0.05) were observed at 3 months among routine and diabetes patients, and at 3 and 6 months among glaucoma patients. A longitudinal data analysis using the generalized estimating equation approach indicated statistically significant treatment effect of HSM lenses in reducing inflammation in all patients except for cellular deposits in diabetes patients. In all patient groups, sight-threatening complications were not reported either more frequently or with more severity than normally expected for patients who have undergone cataract extraction and IOL implantation. CONCLUSIONS: The present study, the only one to have used phacoemulsification in virtually all patients (211/220 [96%] routine, 57/58 [98%] glaucoma, and 84/89 [94%] diabetes) is the largest to evaluate and compare concurrently routine, glaucoma, and diabetes patients. It is also the first US patient population study to document that heparin surface modification reduces postoperative inflammatory responses, as measured by specular micrography and slit-lamp examination, especially in the early postoperative period.

Aged↗

PubMed2003

Feasibility of protein A for the oriented immobilization of immunoglobulin on silicon surface for a biosensor with imaging ellipsometry.

The feasibility of using protein A to immobilize antibody on silicon surface for a biosensor with imaging ellipsometry was presented in this study. The amount of human IgG bound with anti-IgG immobilized by the protein A on silicon surface was much more than that bound with anti-IgG immobilized by physical adsorption. The result indicated that the protein A could be used to immobilize antibody molecules in a highly oriented manner and maintain antibody molecular functional configuration on the silicon surface. High reproducibility of the amount of antibody immobilization and homogenous antibody adsorption layer on surfaces could be obtained by this immobilization method. Imaging ellipsometry has been proven to be a fast and reliable detection method and sensitive enough to detect small changes in a molecular monolayer level. The combination of imaging ellipsometry and surface modification with protein A has the potential to be further developed into an efficient immunoassay protein chip.

Animals↗

PubMed2000

Characteristics and biodistribution of cationic liposomes and their DNA complexes.

We have developed some novel liposome formulations for gene transfection. The formulations consisting of O,O'-ditetradecanoyl-N-(alpha-trimethyl ammonio acetyl) diethanolamine chloride (DC-6-14) as a cationic lipid, phospholipid and cholesterol showed effective gene transfection activity in cultured cells with serum and in vivo, i.e., intraperitoneal injection in mice. In this report, the physicochemical characteristics and biodistribution of the liposomes containing DC-6-14 (DC-6-14 liposomes) as a drug (gene) carrier for gene therapy were investigated in vitro and in vivo. DC-6-14 liposome-DNA complexes were usually thought to have positive surface charge. However, depending on the ratio of DNA to liposomes, zeta-potential of the complexes became negative. The diameter of the complexes also depended on the DNA-liposome ratio, and showed a maximum when their surface potential was neutral. When biodistribution of the complexes was determined after intravenous injection, positively charged complexes showed an immediate lung accumulation. On the other hand, negatively charged complexes did not show lung accumulation. These results have suggested that biodistribution of the DNA-liposome complexes, prepared with DC-6-14 liposomes, depends on their surface charge. Therefore, some surface modification of DC-6-14 liposomes may improve the biodistribution and hence the targetability of their DNA complexes.

Animals↗

PubMed2002

Design of segmented poly(ether ester) materials and structures for the tissue engineering of bone.

In this study, PEOT/PBT segmented copolymers of different compositions have been evaluated as possible scaffold materials for the tissue engineering of bone. By changing the composition of PEOT/PBT copolymers, very different mechanical and swelling behaviors are observed. Tensile strengths vary from 8 to 23 MPa and elongations at break from 500 to 1300%. Water-uptake ranges from 4 up to as high as 210%. The in vitro degradation of PEOT/PBT copolymers occurs both by hydrolysis and oxidation. In both cases degradation is more rapid for copolymers with high PEO content. PEOT/PBT scaffolds with varying porosities and pore sizes have been prepared by molding and freeze-drying techniques in combination with particulate-leaching. The most hydrophilic PEOT/PBT copolymers did not sustain goat bone marrow cell adhesion and growth. However, surface modification by gas plasma treatment showed a very much improved polymer-cell interaction for all PEOT/PBT copolymer compositions. Their mechanical properties, degradability and ability to sustain bone marrow cell growth make PEOT/PBT copolymers excellent materials for bone tissue engineering.

Animals↗

PubMed2001

Mucoadhesive nanoparticulate systems for peptide drug delivery.

This chapter describes the preparation of and methods for evaluating mucoadhesive nanoparticulate systems, including liposomes and polymeric nanoparticles. Mucoadhesive ability is conferred on the particulate systems by coating their surface with mucoadhesive polymers such as chitosan and Carbopol. The feasibility of this surface modification was confirmed by measuring the zeta potential. Several methods of evaluating the mucoadhesive properties of particulate systems have been reported in the literature. We have also developed some novel evaluation procedures including a particle counting method using a Coulter counter for polymer-coated liposomes. The mucoadhesive properties of the polymer-coated liposomes and polymeric nanoparticles were confirmed by means of these mucoadhesion tests. In applying these mucoadhesive nanoparticles to the oral and pulmonary administration of peptide drugs, more effective and prolonged action was observed in comparison with non-coated systems, thereby confirming the usefulness of mucoadhesive nanoparticulate systems for the delivery of peptide drugs.

Animals↗

PubMed2001

Biodegradable block copolymers.

Recently, block copolymers have got tremendous impetus on the ongoing research in the area of drug delivery technology, due to their capability to provide a biomaterial having a broad range of amphiphilic characteristics, as well as targeting the drugs to specific site. This article is an attempt to review applications of block copolymers in surface modification, drug targeting, nano and microparticles, hydrogels, micelles etc. The physicochemical properties of block copolymers and various synthetic routes for block copolymers are also discussed.

Animals↗

PubMed1998

Theoretical considerations of RES-avoiding liposomes: Molecular mechanics and chemistry of liposome interactions.

The development of long-circulating, RES-avoiding liposomes has become a remarkable milestone in the progress of contemporary pharmacology. Drugs incorporated in such liposomes are protected from fast metabolization and clearance, and can be further targeted to a desired tissue site. Ideally, future developments should result in drug carriers which can identify and act upon their targets with even higher efficiency and selectivity, preferably close to or exceeding that of the natural immune cells.Further increasing carrier 'inertness' with regard to the normal biological milieu is the major requirement for future success. The ability of natural blood components to circulate with blood for several days and weeks presents both the motivation and the challenge for further research. Today, even the best available preparations are inferior to natural proteins and cells with regard to their ability to remain in circulation by approximately two orders of magnitude.In view of the above, it seems vitally important to determine the mechanisms responsible for glycolipid- or polymer-modified liposome protection against RES, and whether any potentially useful mechanisms have been underutilized. Furthermore, identification of quantitative dependencies between liposome structure and pharmacokinetics (and mechanisms underlying such dependencies) would benefit future research and reduce the cost of development.This paper discusses the relationships between liposome structure and circulation with respect to the theoretical mechanistic models of mass transfer, liposome interactions with cells and blood proteins, and boundary effects resulting from surface modification. Special attention is paid to the practical application and limitations of the models.

Journal Article↗

PubMed2000

Adsorption of phenol by bentonite.

The potential of bentonite for phenol adsorption from aqueous solutions was studied. Batch kinetics and isotherm studies were carried out to evaluate the effect of contact time, initial concentration, pH, presence of solvent, and the desorption characteristics of bentonite. The adsorption of phenol increases with increasing initial phenol concentration and decreases with increasing the solution pH value. The adsorption process was significantly influenced by the solvent type in which phenol was dissolved. The affinity of phenol to bentonite in the presence of cyclohexane was greater than that in water and was lowest in the presence of methanol. Methanol was used to extract phenol from bentonite. The degree of extraction was dependent on the amount of phenol adsorbed by bentonite. X-ray diffraction analysis showed that the crystalline structure of bentonite was destroyed when cyclohexane was used. The ability of bentonite to adsorb phenol from cyclohexane decreased as the water to cyclohexane ratio was increased. Furthermore, hysteresis was observed in phenol desorption from bentonite in aqueous solutions. The equilibrium data in aqueous solutions was well represented by the Langmuir and Freundlich isotherm models. The removal of phenol from aqueous solutions was observed without surface modification.

Journal Article↗

PubMed2000

Prospective crossover trial of the influence of vitamin E-coated dialyzer membranes on T-cell activation and cytokine induction.

Cytokine induction by dialyzer membranes has been related to several acute and chronic side effects of hemodialysis treatment, among them being immune dysfunction and progressive atherosclerosis. Surface modification of cuprophane dialyzers with the antioxidant vitamin E is a new approach to enhance biocompatibility and improve cytokine levels, as well as immune function. Twenty-one patients undergoing treatment with hemophane (HE) dialyzers were enrolled onto a crossover study with a vitamin E-coated (VE) dialyzer or a synthetic polyamide (PA) dialyzer. In vitro assays of lymphocyte activation and measurements of cytokine induction were performed to evaluate biocompatibility. Four weeks of treatment with either VE or PA dialyzers enhanced in vitro proliferation of peripheral blood leukocytes in comparison to treatment with HE membranes used before study entry. Enhancement of lymphocyte function was independent of dialysis efficiency, which was kept constant during the study. In the interdialytic interval, preactivation of monocytes for the production of interleukin-6 (IL-6) did not differ between VE or PA dialysis. In contrast, the VE membrane reduced acute production of IL-6 during a dialysis treatment, whereas the PA membrane did not. Unlike IL-6, the regulatory cytokine IL-10 is not inhibited by either membrane. This is important because IL-10 is believed to have a beneficial effect on immune function in dialysis patients. The VE membrane, despite being based on a cuprophane backbone, is similar to the highly biocompatible PA dialyzer in terms of its effect on lymphocyte function, whereas it exerts an additional suppressive effect on the overproduction of proinflammatory cytokines.

Aged↗

PubMed2002

Versatile tool for the manipulation of electrophoresis chips.

This communication describes a versatile tool allowing standard operations (i.e. washing, pre-conditioning, separation, inner surface modification of the chip channel) with capillary electrophoresis chips. Through currently designed for a chip of maximal dimensions 30 x 60 mm, other formats of the chip require only a minimum adjustment of the equipment, namely setting of the chip sliding rails and adequate arrangement of the exchangeable heads. The application of the tool is demonstrated by the separation of the standard set of inorganic cations.

Electrophoresis, Capillary↗

PubMed2002

Liposomes as carriers of amphiphilic gadolinium chelates: the effect of membrane composition on incorporation efficacy and in vitro relaxivity.

The effects of membrane composition (phospholipid type and amount of cholesterol), liposome size, drug/lipid ratio (loading) and nature of the amphiphilic gadolinium (Gd) chelate on the incorporation efficacy and magnetic resonance (MR) contrast efficacy (longitudinal (T1) relaxivity) were investigated using a fractional factorial design. A highly lipophilic Gd-chelate was required to ensure complete liposome incorporation. High T1-relaxivity was obtained by using liposomes composed of cholesterol and phospholipids with short acyl chain lengths (dimyristoyl phosphatidyl choline (DMPC) and dimyristoyl phosphatidyl glycerol (DMPG). Two key factors, the loading of Gd-chelate and the amount of cholesterol in small-sized DMPC/DMPG liposomes, were studied further in a central composite optimising design. A robust high relaxivity region was identified, comprising high loading of cholesterol and Gd-chelate. However, the highest T1-relaxivity (52 mM(-1) s(-1)) was found in an area containing no cholesterol and low content of Gd-chelate. Nuclear magnetic resonance dispersion (NMRD) profiles were obtained for five of the liposome compositions from the optimising design, and high relaxivity peaks in the 20 MHz region confirmed the presence of Gd-chelates with a long tau(R). A liposome formulation was selected for surface modification with polyethylene glycol (PEG), without having any effect on the T1-relaxivity.

Chelating Agents↗

PubMed2002

Ibuprofen crystals with optimized properties.

The common analgesic drug ibuprofen shows bad dissolution and tableting behavior due to its hydrophobic structure. Additionally its high cohaesivity results in low flowability. Because of the bad compaction behavior ibuprofen has to be granulated usually before tableting. Another problem in manufacturing is the high tendency for sticking to the punches. A crystal form with optimized properties of ibuprofen was prepared and characterized in this study. Crystallization was carried out using the solvent change technique in the presence of different water-soluble additives. These additives were only present during the crystallization process and removed after precipitation by a washing process. A nearly pure ibuprofen powder was received, as GC-analysis showed. Plate-shaped crystals with increased powder dissolution, increased flowability and good tableting behavior were obtained. All crystals were determined as isomorphic by DSC and X-ray analysis. Thus the improvement of the substance characteristics of ibuprofen is reached by changes in the outer appearance of the crystals and in surface modifications. Due to the fact that ibuprofen molecules can form hydrogen bonds, additives that can interact with these hydrogen bonds during the crystallization process can modify the properties of the resulting crystals.

Analgesics, Non-Narcotic↗

PubMed1993

Heparin-modified lenses for eyes at risk for breakdown of the blood-aqueous barrier during cataract surgery.

To determine the appropriateness of heparin-surface-modified (HSM) lenses in eyes at risk for breakdown of the blood-aqueous barrier, 36 consecutive patients with cataracts associated with chronic recurrent or past uveitis had extracapsular cataract extraction and insertion of an HSM posterior chamber one-piece intraocular lens (IOL). Examinations for implant precipitates (IPs), fibrin membranes, IOL synechias, and visual outcome were done postoperatively. Results show that despite a recurrence of overt uveitis with keratic precipitates in 13 eyes (36.1%), IPs were seen in only six eyes (16.6%) and were generally small and few in number. An acute postoperative fibrin reaction, which is related to blood-aqueous barrier breakdown, occurred in nine eyes. Implant synechias were found in three eyes. We found that HSM provided a cell-free IOL surface in the majority of eyes at high risk for blood-aqueous barrier breakdown and uveitis. Heparin surface modification does not prevent complications but tends to protect the IOL from inflammation changes that might otherwise occur.

Adult↗

PubMed1998

Biocompatibility and blood-aqueous barrier impairment in at-risk eyes with heparin-surface-modified or unmodified lenses.

PURPOSE: To evaluated the influence of heparin-surface-modified (HSM) versus unmodified poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) on the blood-aqueous barrier (BAB) in at-risk eyes. SETTING: Department of Ophthalmology, Bundesknappschaft's Hospital, Sulzbach Germany. METHODS: This study comprised 100 patients with predisposing risk factors for BAB destabilization (e.g., diabetes mellitus with or without retinopathy, glaucoma, pseudoexfoliation, uveitis). One eye in each patient received an HSM IOL and the fellow eye, a conventional unmodified PMMA IOL after phacoemulsification by the same surgeon. Anterior chamber flare was measured with the Kowa 500 laser flare meter 1 day before and 1 day, 1 and 6 weeks, and 3 months after surgery. RESULTS: For most risk factors, mean flare was lower in the HSM group than in the PMMA group at most follow-ups. Significantly lower flare values (difference between postoperative and preoperative mean values) were seen in eyes with the HSM IOL at 6 weeks (P < .004) and 3 months (P < .003; Student's t-test). In the group with preoperative elevated flare values, the eyes with the HSM IOL had significantly better results 6 weeks (P < .0006) and 3 months (P < .01) postoperatively. The values in the HSM IOL eyes were also significantly higher in the diabetic with retinopathy group at 3 months (P < .003). CONCLUSION: The results confirm the efficacy of IOL surface modification in reducing postoperative intraocular reaction in at-risk eyes.

Biocompatible Materials↗

PubMed2000

Methods for reducing biosensor membrane biofouling.

The deleterious effect that biofouling has on sensor stability is a serious impediment to the development of long term implanted biosensors. This paper reviews the surface modification strategies currently employed to minimize membrane biofouling of in vivo sensors. Nine sensor modifications are discussed herein: hydrogels, phospholipid-based biomimicry, flow-based systems, Nafion, surfactants, naturally derived materials, covalent attachments, diamond-like carbons, and topology.

Journal Article↗

PubMed2000

Immobilization of trypsin on porous glycidyl methacrylate beads: effects of polymer hydrophilization.

The immobilization of trypsin at porous glycidyl methacrylate (GMA-GDMA) beads was investigated. In particular, the effects of surface modification of the beads through hydrophilic polymers on the amount protein immobilized and on the extent of retained activity after immobilization were adressed. Furthermore, immobilization at unmodified and hydrophilized beads from aqueous solution was compared to that from a water-in-oil microemulsion. It was found that the amount trypsin immobilized at the unmodified GMA-GDMA beads was significantly higher than that at hydrophilized GMA-GDMA beads. However, also the extent of specific activity loss after immobilization was larger for the unmodified than for the hydrophilized beads. Despite the latter, however, the total activity displayed by the hydrophilized beads was comparable to the unmodified beads at best. On the other hand, by peforming the immobilization from the microemulsion a high immobilization yield can be reached even for the hydrophilized beads, which also results in a higher degree of retained activity in the latter case than obtained for immobilization at the unmodified beads. Using this approach therefore resulted in the highest total activity of the trypsin-activated GMA-GDMA beads.

Journal Article↗

PubMed2003

Improved selectivity of microbial biosensor using membrane coating. Application to the analysis of ethanol during fermentation.

A ferricyanide mediated microbial biosensor for ethanol detection was prepared by surface modification of a glassy carbon electrode. The selectivity of the whole Gluconobacter oxydans cell biosensor for ethanol determination was greatly enhanced by the size exclusion effect of a cellulose acetate (CA) membrane. The use of a CA membrane increased the ethanol to glucose sensitivity ratio by a factor of 58.2 and even the ethanol to glycerol sensitivity ratio by a factor of 7.5 compared with the use of a dialysis membrane. The biosensor provides rapid and sensitive detection of ethanol with a limit of detection of 0.85 microM (S/N=3). The selectivity of the biosensor toward alcohols was better compared to previously published enzyme biosensors based on alcohol oxidase or alcohol dehydrogenases. The biosensor was successfully used in an off-line monitoring of ethanol during batch fermentation by immobilized Saccharomyces cerevisiae cells with an initial glucose concentration of 200 g l(-1).

Biofilms↗

PubMed2003

Cu@Au alloy nanoparticle as oligonucleotides labels for electrochemical stripping detection of DNA hybridization.

Synthesis of the novel Cu@Au alloy nanoparticle and its application in an electrochemical DNA hybridization detection assay is described in this article. We report a low-temperature method for generating core-shell particles consisting of a core of Cu and a thin layer of Au shell that can be readily functionalized with oligonucleotides. Core-shell Cu@Au particles were successfully labeled to a 5'-alkanethiol capped oligonucleotides probe that is related to the colitoxin gene. The DNA genetic sensing assay relies on the electrostatic adsorption of target oligonucleotides onto conducting polypyrrole (PPy) surface at the glassy carbon electrode (GCE), and its hybridization to the alloy particle-oligonucleotides DNA probe. Hybridization events between probe and target were monitored by the release of the copper metal atoms anchored on the hybrids by oxidative metal dissolution and the indirectly determination of the solubilized Cu2+ ions by sensitive anodic stripping voltammetry (ASV). The detection limit is 5.0 pmol l(-1) of target oligonucleotides. The Cu@Au core-shell nanoparticles combining the surface modification properties of Au with the good electrochemical activity of Cu core shows their perspective application in the electrochemical DNA hybridization analysis assay.

Biosensing Techniques↗