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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polyurethane membrane filters and filters coated with poly(ethyleneimine) were used to investigate the influence of leukocyte adhesion during filtration. Treatment of the filters with an aqueous solution of 1% (w/v) poly(ethyleneimine) (PEI) led to the introduction of amine groups at the filter surfaces, as was confirmed by X-ray photoelectron spectroscopy. The modification procedure did not significantly change the porous structure in the filters, as was demonstrated by SEM and porometry. Using 14C-labeled poly(ethyleneimine) it was shown that nearly a complete coverage (approximately 0.1 mg/m2) was achieved that did not desorb from the filter surface during contact with blood plasma. When the filtration was carried out with purified leukocytes in the absence of red cells, platelets, and blood plasma, the number of cells removed by modified filters (> 95%) was significantly higher as compared to the removal with unmodified filters (approximately 80%). However, no significant differences between the filters were found when the filtration was performed with whole blood. This finding was unexpected, because it was shown before that immobilization of poly(ethyleneimine) on solid polyurethane film, surfaces promoted the adhesion of leukocytes from whole blood. Apparently, the adhesive properties of the PEI diminish during filtration. Filter coating of commercial leukocyte filters composed of polyester fibers also had no effect on the removal of leukocytes from whole blood. It was postulated that morphological factors, such as filter shape, roughness, tortuosity, and porosity rather than the physicochemical properties of the filter surface influence cell adhesion to the filter surface, and through that the filtration process.
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PMID:Poly(ethyleneimine) modified filters for the removal of leukocytes from blood. 824 40

Biosynthetic bone grafts are considered to contain one or more of three critical components: osteoprogenitor cells, an osteoconductive matrix, and osteoinductive growth factors. The basic requirements of the scaffold material are biocompatibility, mechanical integrity, and osteoconductivity. A major design problem is satisfying these requirements with a single composite. In this study, we hypothesize that one composite that combines bone marrow-derived osteoblasts and a novel mechanical reinforced porous hydroxyapatite with good biocompatibility and osteoconductivity (HA/BMO) can reach these requirements. A novel sintered porous hydroxyapatite (HA) was prepared by the following procedures. The HA slurry was foamed by adding polyoxyethylenelaurylether (PEI) and mixing. The pores were fixed by crosslinking PEI with diepoxy compounds and the HA porous body was sintered at 1200 degrees C for 3 h. The HA sintered porous body had a high porosity (77%), and was completely interconnected. Average pore diameter was 500 microm and the interconnecting path 200 microm in diameter. The compressive (17 MPa) and three-point bending (7 MPa) strengths were high. For in vivo testing, the 2-week subcultured HA/BMO (+) composites were implanted into subcutaneous sites of syngeneic rats until 8 weeks after implantation. These implants were harvested at different time points and prepared for the biochemical analysis of alkaline phosphatase activity (ALP) and bone osteocalcin content (OCN), and histological analysis. ALP and OCN in the HA/BMO group were much higher than those in the HA without BMOs control group 1 week after implantation (p < 0.001). Light microscopy revealed mature bone formation in the HA/BMO composite 4 weeks after implantation. In the SEM study, mineralized collagenous extracellular matrix was noted in HA/BMO composite 2 weeks after implantation with numbers of active osteoblasts. We conclude that the composite of the novel HA and cultured BMOs has osteogenic ability in vivo. These results provide a basis for further studies on the use of this composite as an implant in orthopaedic surgery.
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PMID:In vivo evaluation of a novel porous hydroxyapatite to sustain osteogenesis of transplanted bone marrow-derived osteoblastic cells. 1148 83

We report the development of new biomacromolecule coatings on biodegradable biomaterials based on electrostatic assembly of extracellular matrix-like molecules. Poly(ethylene imine) (PEI) was employed to engineer poly(dl-lactide) (PDL-LA) substrate to obtain a stable positively charged surface. An extracellular matrix- (ECM-) like biomacromolecule, gelatin, was selected as the polyelectrolyte to deposit on the activated PDL-LA substrate via the electrostatic assemble technique. The extracellular matrix-like multilayer on the PDL-LA substrate was investigated by attenuated total reflection (ATR-FTIR), X-ray photoelectron spectrscopy (XPS), contact angle, and atomic force microscopy (AFM). The gradual buildup of the protein layer was investigated by UV-vis spectra, and it was further given a quantitative analysis of the protein layer on the PDL-LA substrate via the radioiodination technique. The stability of the protein layer under aqueous condition was also tested by the radiolabeling method. Chondrocyte was selected as the model system for testing the cell behavior and morphology on modified PDL-LA substrates. The chondrocyte test about cell attachment, proliferation, cell activity and cell morphology by SEM, and confocal laser scanning microscopy (CLSM) investigation on extracellular matrix-like multilayer modified PDL-LA substrate was shown to promote chondrocyte attachment and growth. Comparing conventional coating methods, polyelectrolyte multiplayers are easy and stable to prepare. It may be a good choice for the modification of 3-D scaffolds used in tissue engineering. These very flexible systems allow broad medical applications for drug delivery and tissue engineering.
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PMID:Surface engineering of poly(DL-lactide) via electrostatic self-assembly of extracellular matrix-like molecules. 1262 35

Extracellular matrix (ECM)-like coating was developed on biodegradable biomaterials based on the electrostatic self-assembly (ESA) technique to promote osteoblast growth. Poly(ethylenimine) (PEI) was first employed to obtain a stable positively charged surface on poly (DL-lactide) (PDL-LA) substrate. Gelatin was selected as ECM-like biomacromolecule to deposit on the activated PDL-LA substrate using the ESA technique. zeta-Potential results showed alternating charge of polyelectrolytes (PEI/gelatin) layering on PDL-LA microspheres. Quartz crystal microbalance (QCM) measurement further verified the gradual deposition of PEI/gelatin on PDL-LA thin film. Osteoblast cells (MC3T3) were chosen to test the cell behavior on modified PDL-LA substrates. The osteoblast test about cell activity, intracellular total DNA content, total protein content and cell morphology by SEM investigation on ECM-like multilayer-modified PDL-LA substrate showed to promote osteoblast growth. Comparing conventional coating methods, polyelectrolyte multilayers are easy and stable to prepare. It may be a good choice for the surface modification of complex biomedical devices. These very flexible systems allow broad medical applications for drug delivery and tissue engineering.
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PMID:Osteoblast growth promotion by protein electrostatic self-assembly on biodegradable poly(lactide). 1602 95

This study mainly deals with cell transfection and cytotoxicity for PEI(10kD)-PBLG, a novel cationic copolymer, to observe its potential as a gene carrier. Size measurement and SEM were used to show the modality of the PEI-PBLG/pDNA complexes. Cytotoxicity of PEI (10kD)-PBLG was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay and compared with PEI(25kD)-PBLG, PEI(10kD), and PEI(25kD). Furthermore, pEGFP that can express the enhanced green fluorescent protein was chosen as a reporter to observe the transfection efficiency directly. Then, PEI (10kD)-PBLG/pEGFP complexes were transfected into several cell lines, such as Hela, COS-7, Vero-E6, and ECV-304, and effects of the transfection conditions were evaluated. The efficiencies were measured by FACS. Size measurement of complex particles indicated that PEI-PBLG/pDNA tended to form smaller nanoparticles compared with PEI/pDNA. The representative size of the PEI(10kD)-PBLG/pDNA complex was approximately 100 - 200 nm. SEM images showed that the particles were condense and compact. This can be suitable for their entry into cells. Cytotoxicity studies suggested that PEI (10kD)-PBLG had considerably lower toxicity than the other three materials. In the transfection tests, PEI (10kD)-PBLG/pDNA complexes could be transfected into all the cell lines that were tested. These provided the highest level of EGFP expression (45.02%) in Hela cells, which was considerably higher than that of PEI(10kD)/pEGFP (29.16%). Being less affected by the serum during transfection, PEI-PBLG/pDNA complexes offered greater biocompatibility than PEI. PEI-PBLG copolymer reduces the cytotoxicity of PEI, improves the transfection efficiency, and offers greater biocompatibility than PEI. It shows considerable potential as an efficient nonviral carrier for gene delivery.
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PMID:[Transfection with a novel cationic gene carrier: PEI-PBLG]. 1746 Aug 93

Materials for blood-contacting applications have to meet high requirements in terms to prevent thrombotic complications after the medical treatment. Surface induced thrombosis, e.g., after application of cardiovascular devices, is linked clearly to the activation of coagulation system and platelet adhesion and activation. The flat sheet poly(ether imide) membrane (PEI) was modified by binding of iminodiacetic acid (IDA) for different periods of time to obtain surfaces with carboxylic (-COOH) groups, namely PEI-1 (modified for 1 min) and PEI-2 (modified for 30 min). The successful binding of the ligands was monitored by thionin acetate assay. The physico-chemical characteristics of the materials were analyzed by SEM, AFM, water contact angle, and Zeta potential measurements. Hemocompatibility of the polymer materials was studied by analyzing the activation of coagulation system (plasma kallikrein-like activity) and platelet adhesion/activation by using immunofluorescence technique. The blood response to PEI membranes was compared to that of a commercial poly(ethylene terephthalate) (PET) membrane. Our results showed that the increase of the negative charges on the modified PEI membrane surfaces (number of -COOH groups) caused a higher contact activation of the coagulation system and a higher rate of platelet adhesion and activation compared to non-modified PEI. However, overall the hemocompatibility of all PEI membranes was higher than that of PET.
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PMID:Hemocompatibility of poly(ether imide) membranes functionalized with carboxylic groups. 1845 29

Cholesterol-conjugated H(5)R(10) and H(10)R(10) oligopeptides (HR15-Chol and HR20-Chol) were designed and synthesized. These amphiphilic oligopeptides were able to self-assemble into cationic micelles in aqueous solution at low concentrations, and their critical micelle concentrations in sodium acetate buffer (20mM, pH 5.0) were 17.8 and 28.2mg/L respectively. The micelle formation was further evidenced via SEM and dynamic light scattering analyses. The average hydrodynamic size of HR15-Chol and HR20-Chol micelles was about 425 and 435 nM in diameter with zeta potential of 64 and 66 mV respectively. The formation of micelles increased local concentration of cationic charge, leading to higher DNA binding efficiency as compared to the control peptides HR15 and HR20. The minimum size observed for HR15-Chol/DNA and HR20-Chol/DNA complexes was about 175-176 nM, and the maximum zeta potential was around 61-62 mV. In comparison, HR15 and HR20 formed DNA complexes with a similar size but significantly lower zeta potential (i.e. about 31-40 mV). In particular, after being challenged by DMEM medium, the size of peptide/DNA complexes was increased significantly and their surface charge was neutralized. Nevertheless, the size of the micelle/DNA complexes formed from HR15-Chol and HR20-Chol was still about 200 nM with positive charge of around 20 mV at high N/P ratios. The micelles induced much higher overall gene expression (i.e. luciferase expression) levels than the peptides in both HepG2 and HEK293 cell lines. Increasing the histidine residue from 0 to 5 to 10 further increased gene expression efficiency. In particular, HR20-Chol micelles yielded 95% GFP-positive HepG2 cells at N/P 50, much higher than that induced by PEI at its optimal N/P ratio (i.e. 10), which was 6.8%. In 4T1 cells, HR20-Chol induced 2 times higher luciferase expression level than PEI at their optimal N/P ratios. Moreover, HR20-Chol micelle/DNA complexes were less cytotoxic than PEI/DNA complexes. These micelles may be a promising carrier for delivery of therapeutic genes.
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PMID:Cationic micelles self-assembled from cholesterol-conjugated oligopeptides as an efficient gene delivery vector. 1882 2

Novel multifunctional octadecyl quaternized carboxymethyl chitosans (OQCMCs) with varying degree of quaternary substitution (DS) and molecular mass were prepared and compared with quaternized chitosan. OQCMCs exhibited excellent solubility both in water and organic solvents. Nanoparticles of OQCMCs offered many advantages, such as easier fabrication and modulation of their size and degree of positive charge, and a lower cytotoxic effect compared with PEI (25 kDa). DNA can be successfully adsorbed on its surface. Electrostatic attraction of carboxymethyl and quaternary groups in OQCMCs was utilized as micellar template for the synthesis of cross-linked micelles. Formation and characteristics of OQCMC polymeric micelles were studied by fluorescence spectroscopy, tensiometry, SEM, TEM and particle size analysis. Self-assembled OQCMC micelles were evaluated as carrier of the lipophilic drug, minocycline hydrochloride (MH). MH was incorporated into cross-linked ionic cores of micelles with remarkably high efficiency (22.7%, w/w). MH-loaded OQCMC polymeric micelles exhibited a slow steady release profile over a 1-week period at 37 degrees C. The OQCMC micelles are potentially useful for gene and lipophilic drug delivery applications.
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PMID:Novel quaternized chitosan and polymeric micelles with cross-linked ionic cores for prolonged release of minocycline. 1910 4

The entrapment of enzymes within biomimetic silica nanoparticles offers unique and simple immobilization protocols that merge the stability of proteins confined in solid phases with the high loading and reduced diffusion limitations inherent to nano-sized structures. Herein, we report on the biomimetic silica entrapment of chemically derivatized horseradish peroxidase for amperometric sensing applications. Scanning electron microscopy shows evidence of the formation of enzyme-modified nanospheres using poly(ethylenimine) as a template for silicic acid condensation. When these nanospheres are directly deposited on graphite electrodes, chemically modified anionic peroxidase shows direct electron transfer at 0 mV vs Ag|AgCl. Microgravimetric measurements as well as SEM images demonstrate that negatively charged peroxidase is also entrapped when silica precipitates at gold electrodes are modified with a self-assembled monolayer of poly(ethylenimine). Electrostatic interactions may play a crucial role for efficient enzyme entrapment and silica condensation at the PEI template monolayer. The in-situ biomimetically synthesized peroxidase nanospheres are catalytically active, enabling direct bioelectrocatalysis at 0 mV vs Ag|AgCl with long-term stability.
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PMID:Enzyme-modified nanoparticles using biomimetically synthesized silica. 1954 Jan 73

This paper focuses on the effects of biological and synthetic polymers on the formation of amorphous silica. A concise review of relevant literature related to biosilicification is presented. The importance of synergies between polyelectrolytes on the inhibition of silicic acid condensation is discussed. A specific example of a zwitterionic polymer phosphonomethylated chitosan (PCH) is further analyzed for its inhibitory activity. Specifically, the ability of PCH to retard silicic acid condensation at circumneutral pH in aqueous supersaturated solutions is explored. It was discovered that in short-term studies (0-8 h) the inhibitory activity is PCH dosage-independent, but for longer condensation times (>24 h) there is a clear increase in inhibition upon PCH dosage increase. Soluble silicic acid levels reach 300 ppm after 24 h in the presence of 160 ppm PCH. Furthermore, the effects of either purely cationic (polyethyleneimine, PEI) or purely anionic (carboxymethylinulin, CMI) polyelectrolytes on the inhibitory activity of PCH is systematically studied. It was found that the action of inhibitor blends is not cumulative. PCH/PEI blends stabilize the same level of silicic acid as PCH alone in both short-term (8 h) and long-term (72 h) experiments. PCH/CMI combinations on the other hand can only achieve short-term inhibition of silicic acid polymerization, but fail to extend this over the first 8 h. PCH and its combinations with PEI or CMI affect silica particle morphology, studied by SEM. Spherical particles and their aggregates, irregularly shaped particles and porous structures are obtained depending on additive or additive blend. It was demonstrated by FT-IR that PCH is trapped in the colloidal silica matrix.
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PMID:Bioinspired control of colloidal silica in vitro by dual polymeric assemblies of zwitterionic phosphomethylated chitosan and polycations or polyanions. 1969 46


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