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PEG
Kinds of PEG Terms modified by PEG Selected AbstractsProtein-Release Behavior of Self-Assembled PEG,, -Cyclodextrin/PEG,Cholesterol HydrogelsADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Frank van de Manakker Abstract This paper reports on the degradation and protein release behavior of a self-assembled hydrogel system composed of , -cyclodextrin- (,CD) and cholesterol-derivatized 8-arm star-shaped poly(ethylene glycol) (PEG8). By mixing ,CD- and cholesterol-derivatized PEG8 (molecular weights 10, 20 and 40 kDa) in aqueous solution, hydrogels with different rheological properties are formed. It is shown that hydrogel degradation is mainly the result of surface erosion, which depends on the network swelling stresses and initial crosslink density of the gels. This degradation mechanism, which is hardly observed for other water-absorbing polymer networks, leads to a quantitative and nearly zero-order release of entrapped proteins. This system therefore offers great potential for protein delivery. [source] The properties of reactive hot melt polyurethane adhesives modified with novel thermoplastic polyurethanesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009Tae K. Kim Abstract A reactive hot melt adhesive (RHMA) consisting of thermoplastic polyurethane (TPU) was modified with sodium montmorillonite (Na-MMT) intercalated with poly(ethylene glycol) (PEG), and their effects on the adhesion, rheological, and mechanical properties of the RHMA were examined. The Na-MMT intercalated with PEG (Na-MMT/PEG) effectively enhanced the initial bond strength development of the RHMA, although the amounts of Na-MMT/PEG in the RHMA were less than 0.2%. The increase of the complex viscosity and pseudo-solid like behavior observed at low shear rate indicates that there are intimate interactions between the RHMA molecules and Na-MMT/PEG. The improved modulus and tensile strength of the cured RHMA film in the presence of Na-MMT/PEG demonstrates that Na-MMT/PEG effectively reinforced the RHMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Allergic contact dermatitis to copolymers in cosmetics , case report and review of the literatureCONTACT DERMATITIS, Issue 5 2006Sarah Quartier Copolymers or heteropolymers are large molecules with high molecular weights (>1000 D). They have been underestimated for a long time as to their sensitizing capacities. Allergic contact dermatitis to 6 copolymers in cosmetics and 1 in a medical dressing has been described; however, the nature of the hapten is still unknown. We report a case of allergic contact dermatitis to polyvinylpyrrolidone (PVP)/hexadecene copolymer in a purple-colored lipstick and review the literature on allergic contact dermatitis to 7 copolymers: PVP/hexadecene, PVP/eicosene, PVP/1-triacontene, methoxy polyethyleneglycol (PEG)-22/dodecyl glycols, methoxy PEG-17/dodecyl glycols, phthalic anhydride/trimellitic anhydride/glycols, and polyvinyl methyl/maleic acid anhydride. [source] Raman and Rayleigh scattering study of crystalline polyoxyethyleneglycolsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005M. Kozielski Abstract Results of the study of Raman and Rayleigh scattering in crystalline polyoxyethyleneglycols (PEG) and PEG 1500 aqueous solution are reported. The conformational changes of the polymer chain have been studied as a function of PEG water solution concentration and molecular weight. Intensity ratios of the gauche and trans conformation around C,C and C,O bonds have been estimated from the Raman spectra. Moreover, from the Raman band parameters the values of the order parameters versus aqueous solution concentration have been determined. The influence of an external electric field on these parameters has been analysed. Mutual orientation of polyoxyethyleneglycol chains in the crystalline and liquid state has been studied on the basis of the angular correlation parameters obtained from the Rayleigh band intensity as a function of aqueous solution concentration and molecular weight. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Flow cytometry antibody screening using pooled red cells,CYTOMETRY, Issue 2 2010Dong Il Won Abstract Background: For red cell alloantibody screening, the column agglutination technique (CAT) is used extensively, and flow cytometry (FC) screening has recently been demonstrated to be accurate, rapid, and cost effective. We attempted to determine whether the high sensitivity of FC allows pooling of screening red cells, which is generally not an acceptable technique in CAT. Methods: For FC screening, a commercial two-cell screening panel was utilized for the preparation of individual cells (CSi), as well as pooled cells diluted 1 in 2 (CSp), and 1 in 3 (CS1/3). Another panel was pooled from 120 randomly selected group O donors (RSp). Results: Comparing the endpoint titrations of serial dilutions, CS1/3 was found to be one dilution, on the average, less sensitive than CSi. In 33 CAT-positive patient samples, the sensitivities of CSi and CSp did not differ significantly without polyethylene glycol (PEG) (30/33, 26/33, respectively, P = 0.125), although they did differ significantly with PEG (32/33, 25/33, respectively, P = 0.016). The percentages of reactive cells among the total cells from RSp were roughly proportional to the relevant antigen frequencies of the local donors. Conclusions: A trend toward reduced sensitivity was observed using pooled red cells, even via FC. Pooled cells from randomly selected group O donors may be employed as another method by which the characteristics of known antibodies might be assessed. © 2009 Clinical Cytometry Society [source] CLINICAL INVESTIGATION OF UPPER GASTROINTESTINAL HEMORRHAGE AFTER PERCUTANEOUS ENDOSCOPIC GASTROSTOMYDIGESTIVE ENDOSCOPY, Issue 3 2010Shinji Nishiwaki Background:, Upper gastrointestinal (GI) hemorrhage after percutaneous endoscopic gastrostomy (PEG) is sometimes reported as one of the serious complications. Our purpose was to clarify the cause of upper GI hemorrhage after PEG. Patients and Methods:, We retrospectively investigated the causes of upper GI hemorrhage among a total of 416 patients out of 426 consecutive patients who underwent PEG in our institution, excluding 10 patients who showed upper GI tumors on PEG placement. Results:, Among 17 patients who developed upper GI hemorrhage after PEG, three and four patients showed PEG tube placement and replacement-related hemorrhage, respectively; these lesions were vascular or mucosal tears around the gastrostomy site. Ten patients experienced 12 episodes of upper GI hemorrhage during PEG tube feeding. The lesions showing bleeding were caused by reflux esophagitis (five patients), gastric ulcer (two patients), gastric erosion due to mucosal inclusion in the side hole of the internal bolster (two patients), and duodenal diverticular hemorrhage (one patient). Anticoagulants were administered in six patients, including four patients with replacement-related hemorrhage and one patient each with reflux esophagitis and gastric ulcer. Conclusions:, Reflux esophagitis was the most frequent reason for upper GI hemorrhage after PEG. The interruption of anticoagulants should be considered for the prevention of hemorrhage on the placement as well as replacement of a gastrostomy tube. [source] REDUCING THE RISK OF PERISTOMAL INFECTION AFTER PEG PLACEMENTDIGESTIVE ENDOSCOPY, Issue 4 2005Iruru Maetani Percutaneous endoscopic gastrostomy (PEG) was first described in 1980 as an effective means of enteral nutrition where oral intake is not possible. PEG placement is safe and has now replaced the nasogastric tube in patients who need long-term feeding. Although it is relatively safe with a very low associated mortality, minor complications, especially local and systemic infection, remain a problem. Of these, peristomal wound infections are the most common complication of PEG. In patients indicated for this procedure who are aged and/or frail, this complication may pose a critical problem. In the commonly used pull or push methods for PEG placement, the PEG tube is readily colonized by oropharyngeal bacteria. Infection of the PEG site is considered to be associated with contamination of the PEG catheter. There are important measures that should be taken to prevent peristomal infection. A number of rigorous studies have shown that prophylactic antibiotics are effective in reducing the risk of peristomal infection. As methicillin-resistant Staphylococcus aureus (MRSA) or other resistant organisms are emerging as a major pathogen in peristomal infection, however, currently recommended antibiotic prophylaxis regimens might be inappropriate. Alternative regimens and other approaches to prevent contamination of the PEG tube during the procedure are required. [source] Solubility studies on valdecoxib in the presence of carriers, cosolvents, and surfactantsDRUG DEVELOPMENT RESEARCH, Issue 1 2004Kashappa Goud H. Desai Abstract Enhancement of the solubility of valdecoxib was examined using a series of hydrophilic carriers (mannitol, polyethylene glycol (PEG) 4000, PEG 6000, PEG 8000, and urea), surfactants (Tween-20, Tween-80, and sodium lauryl sulfate [SLS]) and cosolvents (ethanol, methanol, and glycerol) at 37°C. The solubility of valdecoxib could be enhanced significantly using PEG 4000 as a carrier, ethanol as cosolvent, and SLS as a surfactant. Because the solubility of valdecoxib increased dramatically in the presence of polyethylene glycols, these are suitable dispersing agents for preparing solid dispersions containing valdecoxib. Gibbs free energy (,G) values were all negative for all hydrophilic carriers tested, indicating the spontaneous nature of valdecoxib solubilisation. Among the cosolvents, ethanol exhibited higher solubilization potential than methanol and glycerol. As the dielectric constant of the cosolvent,water mixtures decreased, the solubility of valdecoxib increased. Finally, SLS exerted maximum solubilization of valdecoxib when compared to Tween-20 or Tween-80. The crystallinity of valdecoxib was explored by X-ray diffraction study and showed numerous crystalline peaks. Examination of surface morphology by scanning electron microscopy depicted a near spherical shape of valdecoxib with irregular surface characteristics. Drug Dev. Res. 62:41,48, 2004. © 2004 Wiley-Liss, Inc. [source] Determination of Ytterbium Traces by Cathodic Stripping VoltammetryELECTROANALYSIS, Issue 1 2003Marina Mlakar Abstract The method of ytterbium(III) trace concentration in the presence of 2-thenoyltrifluoroacetone (TTA) and polyethyleneglycol (PEG) in ammonium chloride is described. The adsorption was performed at the HMDE at ,1.0,V using linear scan voltammetry and square-wave voltammetry. The relationship between properties of the SW response of the mixed ligand complex and parameters of a charge transfer were analyzed using theoretical data of SW redox processes. [source] Testing of the influenza virus purification by CIEFELECTROPHORESIS, Issue 2 2010Marie Horká Abstract In virological practice, the pre-concentration, purification and subsequent determination of the purity and concentration of the viruses from the cultural medium and/or from the real sample are required. The conventional techniques used today are equipment demanding, time-consuming and laborious. In this study, the CIEF of influenza viruses with UV detection has been developed and subsequently used to test the purification of the virus from the biological samples. The equine and swine influenza viruses present in infected allantoic fluid of specific pathogen free embryonated chicken eggs were precipitated by using PEG 6000 and sodium chloride. The precipitated viruses were centrifuged at 14,000×g, and the impurities of different densities were removed by using the sucrose gradients. The efficiency of the virus purification technique was examined by the CIEF and compared to the results of real-time PCR. The pIs of both influenza viruses were determined. Simultaneously, the CIEF was found to be a suitable method for the rapid testing of the efficiency of the virus purification. [source] CE-based noncompetitive immunoassay for immunoglobulin G in bovine colostrum productsELECTROPHORESIS, Issue 21 2007Jin Zhao Abstract A CE-based noncompetitive immunoassay for IgG in bovine colostrum products was established. FITC-labeled protein G (FITC-PrG) was tagged through noncovalent bindings to the Fc region of the mouse monoclonal antibovine IgG (Ab). The FITC-PrG, Ab, and IgG formed a sandwiched immunocomplex FITC-PrG-Ab-IgG under optimal incubation conditions. The immunocomplex was separated and analyzed by CZE with LIF detection in less than 2,min in an uncoated fused-silica capillary. Addition of PEG 20,000 (PEG 20M) in the running buffer significantly suppressed analyte adsorption and thus improved the reproducibility and the resolution. The precision of the method was 5.1% (n,=,7). A linear relationship was established for the IgG concentration in the range of 1,5,mg/L with a linear correlation coefficient (r,=,0.9917). The LOD was 0.1,mg/L (S/N,=,3). The method was successfully applied for the determination of IgG in bovine colostrum products and satisfactory results were achieved. [source] Intracellular FITC-derivatization with PEGELECTROPHORESIS, Issue 21 2005Fanguo Chen Abstract In order to investigate the amino acids (AAs) in plant cells, we explore an avenue for intracellular derivatization with FITC. In this method, FITC was used to mark AAs in living protoplasts derived from embryogenic calli of common wheat (Triticum aestivum L.,c.v. Jinan,177) mediated by PEG. After FITC-derivatization, the AAs in the lysate were determined by CE. The result reveals that this PEG method can be used to transfer FITC into plant cells efficiently, which provides a good method for AA,analysis in plant cells. [source] Sodium dodecyl sulfate-capillary gel electrophoresis of polyethylene glycolylated interferon alphaELECTROPHORESIS, Issue 3 2004Dong H. Na Abstract Sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) using a hydrophilic replaceable polymer network matrix was applied to characterize the polyethylene glycol(PEG)ylated interferon alpha (PEG-IFN). The SDS-CGE method resulted in a clearer resolution in both the PEG-IFN species and the native IFN species. The distribution profile of PEGylation determined by SDS-CGE was consistent with that obtained by SDS-polyacrylamide gel electrophoresis (PAGE) with Coomassie blue or barium iodide staining. The result was also compared using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry. SDS-CGE was also useful for monitoring the PEGylation reaction to optimize the reaction conditions, such as reaction molar ratio. This study shows the potential of SDS-CGE as a new method for characterizing the PEGylated proteins with advantages of speed, minimal sample consumption and high resolution. [source] Tumour cell,dendritic cell fusion for cancer immunotherapy: comparison of therapeutic efficiency of polyethylen-glycol versus electro-fusion protocolsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 3 2002M. Lindner Abstract Background ,Fusion of tumour cells with dendritic cells (DC) is a powerful new technology to increase tumour vaccine immunogenicity. The aim of this study was to compare fusion protocols with syngenic DCs with respect to the efficiency of polyethylen-glycol-(PEG) and electric pulse-mediated fusions for induction of protective anti-tumour immune responses. As a model we chose a low immunogenic and metastatic murine mammary carcinoma cell line, which mimics clinically relevant tumour features. Methods FACS-staining, chromium release assay, therapeutic immunization, adoptive transfer. Results ,We show that the parental line with low cell surface expression of MHC molecules as well as a lacZ transfectant becomes highly immunogenic upon fusion with DCs. This was true for PEG- as well as for electro-fused cells. Immunization with products of DCs and tumour cells cocultivated for 16 h without the fusing agent PEG also caused induction of profound anti-tumour immunity, while this was not the case when using parental tumour cells or their lacZ transfectants as vaccines. Immune protection against the parental tumour cells after vaccination with fused cells was long-lasting and could be transferred via immune spleen cells into immuno-incompetent nude (nu/nu) mice. Conclusion ,Fusion products of DA3hi mammary carcinoma cells and DCs produced by an electric pulse were similar to those produced by PEG fusion with regard to vaccine potency in prophylactic antitumour immunization assays in vivo. Therefore, both techniques seem to be promising for clinical application. [source] Intraocular injection of tamoxifen-loaded nanoparticles: a new treatment of experimental autoimmune uveoretinitisEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2004Yvonne de Kozak Abstract In this study, we tested the efficiency of an intravitreal injection of tamoxifen, a non-steroidal estrogen receptor modulator, in retinal soluble antigen (S-Ag)-induced experimental autoimmune uveoretinitis (EAU). To increase the bioavailability of tamoxifen, we incorporated tamoxifen into polyethylene glycol (PEG)-coated nanoparticles (NP-PEG-TAM). The localization of the nanoparticles within the eye was investigated using fluorescent-labeled PEG-coated nanoparticles after injection into the vitreous cavity of rats with EAU. Some nanoparticles were distributed extracellularly throughout the ocular tissues, others were concentrated in resident ocular cells and in infiltrating macrophages. Whereas the injection of free tamoxifen did not alter the course of EAU, injection of NP-PEG-TAM performed 1,2,days before the expected onset of the disease in controls resulted in significant inhibition of EAU. NP-PEG-TAM injection significantly reduced EAU compared to injection of NP-PEG-TAM with 17,-estradiol (E2), suggesting that tamoxifen is acting as a partial antagonist to E2. Diminished infiltration by MHC class,II+ inflammatory cells and low expression of TNF-,, IL-1,, and RANTES mRNA were noted in eyes of NP-PEG-TAM-treated rats. Intravitreal injection of NP-PEG-TAM decreased S-Ag lymphocyte proliferation, IFN-, production by inguinal lymph node cells, and specific delayed-type hypersensitivity indicative of a reduced Th1-type response. It increased the anti-S-Ag IgG1 isotype indicating an antibody class switch to Th2 response. These data suggest that NP-PEG-TAM inhibition of EAU could result from a form of immune deviation. Tamoxifen-loaded nanoparticles may represent a new option for the treatment of experimental uveitis. [source] Retention behavior of trans isomers of eicosapentaenoic and docosahexaenoic acid methyl esters on a polyethylene glycol stationary phaseEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 6 2008Svein A. Mjřs Abstract A polyethylene glycol (PEG) stationary phase was evaluated for the separation of mono- trans isomers of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) methyl esters. The resolution patterns were compared to patterns achieved with previously applied conditions on a cyanopropyl phase. There were no overlaps between all- cis EPA/DHA and their mono- trans isomers on the PEG phase. Because of overlap between 22:0 and 22:1 isomers, the PEG column is not a good choice for analyses of EPA trans isomers in crude fish oils. However, if the saturated and monounsaturated fatty acids are not present in significant amounts, PEG can be a better choice than cyanopropyl columns. [source] EFNS task force on management of amyotrophic lateral sclerosis: guidelines for diagnosing and clinical care of patients and relativesEUROPEAN JOURNAL OF NEUROLOGY, Issue 12 2005An evidence-based review with good practice points Despite being one of the most devastating diseases known, there is little evidence for diagnosing and managing patients with amyotrophic lateral sclerosis (ALS). Although specific therapy is lacking, correct early diagnosis and introduction of symptomatic and specific therapy can have a profound influence on the care and quality of life of the patient and may increase survival time. This document addresses the optimal clinical approach to ALS. The final literature search was performed in the spring of 2005. Consensus recommendations are given graded according to the EFNS guidance regulations. Where there was lack of evidence but consensus was clear we have stated our opinion as good practice points. People affected with possible ALS should be examined as soon as possible by an experienced neurologist. Early diagnosis should be pursued and a number of investigations should be performed with high priority. The patient should be informed of the diagnosis by a consultant with a good knowledge of the patient and the disease. Following diagnosis, the patient and relatives should receive regular support from a multidisciplinary care team. Medication with riluzole should be initiated as early as possible. PEG is associated with improved nutrition and should be inserted early. The operation is hazardous in patients with vital capacity <50%. Non-invasive positive pressure ventilation improves survival and quality of life but is underused. Maintaining the patients ability to communicate is essential. During the entire course of the disease, every effort should be made to maintain patient autonomy. Advance directives for palliative end of life care are important and should be fully discussed early with the patient and relatives respecting the patients social and cultural background. [source] Proteolytically Degradable Photo-Polymerized Hydrogels Made From PEG,Fibrinogen Adducts,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Daniel Dikovsky Abstract We develop a biomaterial based on protein,polymer conjugates where poly(ethylene glycol) (PEG) polymer chains are covalently linked to multiple thiols on denatured fibrinogen. We hypothesize that conjugation of large diacrylate-functionalized linear PEG chains to fibrinogen could govern the molecular architecture of the polymer network via a unique protein,polymer interaction. The hypothesis is explored using carefully designed shear rheometry and swelling experiments of the hydrogels and their precursor PEG/fibrinogen conjugate solutions. The physical properties of non-cross-linked and UV cross-linked PEGylated fibrinogen having PEG molecular weights ranging from 10 to 20,kDa are specifically investigated. Attaching multiple hydrophilic, functionalized PEG chains to the denatured fibrinogen solubilizes the denatured protein and enables a rapid free-radical polymerization cross-linking reaction in the hydrogel precursor solution. As expected, the conjugated protein-polymer macromolecular complexes act to mediate the interactions between radicals and unsaturated bonds during the free-radical polymerization reaction, when compared to control PEG hydrogels. Accordingly, the cross-linking kinetics and stiffness of the cross-linked hydrogel are highly influenced by the protein,polymer conjugate architecture and molecular entanglements arising from hydrophobic/hydrophilic interactions and steric hindrances. The proteolytic degradation products of the protein,polymer conjugates proves to be were different from those of the non-conjugated denatured protein degradation products, indicating that steric hindrances may alter the proteolytic susceptibility of the PEG,protein adduct. A more complete understanding of the molecular complexities associated with this type of protein-polymer conjugation can help to identify the full potential of a biomaterial that combines the advantages of synthetic polymers and bioactive proteins. [source] Photopolymerizable Hydrogels Made from Polymer-Conjugated Albumin for Affinity-Based Drug Delivery,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2010Liat Oss-Ronen As a drug delivery vehicle, biodegradable albumin hydrogels can combine the high binding capacity of albumin with the structural stability of a polymeric hydrogel network to enable controlled release of small molecules based on both binding affinity and physical interactions. In the present study, we report on the development of a hybrid hydrogel composed of albumin conjugated to poly(ethylene glycol) (PEG) for drug delivery applications where controlled release is accomplished using the natural affinity of the drugs to the serum albumin. Bovine serum albumin was conjugated to PEG-diacrylate having a molecular weight of 1.5, 4, or 10,kDa to form a PEGylated albumin macromolecule (mono-PEGylated or multi-PEGylated). Biodegradable hydrogels were formed from the PEGylated albumin using photopolymerization. Two model drugs, Warfarin and Naproxen, were used for equilibrium dialysis and release experiments from the hydrogels, both having relatively low molecular weights and a known high affinity for albumin. Equilibrium dialysis experiments showed that multi-PEGylation of albumin significantly decreased the drug affinity to the protein compared to non-PEGylated controls, irrespective of the PEG molecular weight. However, the results from drug release experiments showed that mono-PEGylation of albumin did not change its natural affinity to the drug. Comparing the release profiles with a Fickian diffusion model provided strong evidence that hydrogels containing mono-PEGylated albumin exhibited sub-diffusive drug release properties based on the affinity of the drug to the tethered protein. [source] A Microwave-Assisted Heck Reaction in Poly(ethylene glycol) for the Synthesis of BenzazepinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2007Valérie Declerck Abstract The Heck reaction of alkylated 2-(trimethylsilyl)ethanesulfonyl (SES)-protected ,-amino esters provides benzazepines in good yields. Good selectivity towards cyclisation was obtained when the reaction was performed in PEG 3400 as the solvent under microwave activation. Cleavage of the SES group with HF provides the corresponding free benzazepine. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] A Molecular Brush Approach to Enhance Quantum Yield and Suppress Nonspecific Interactions of Conjugated Polyelectrolyte for Targeted Far-Red/Near-Infrared Fluorescence Cell ImagingADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Kan-Yi Pu Abstract A red-fluorescent conjugated polyelectrolyte (CPE, P2) is grafted with dense poly(ethylene glycol) (PEG) chains via click chemistry and subsequently modified with folic acid to form a molecular brush based cellular probe (P4). P4 self-assembles into a core,shell nanostructure in aqueous medium with an average size of 130 nm measured by laser light scattering. As compared to P2, P4 possesses not only a substantially higher quantum yield (11%), but also reduced nonspecific interactions with biomolecules in aqueous medium due to the shielding effect of PEG. In conjunction with its high photostability and low cytotoxicity, utilization of P4 as a far-red/near-infrared cellular probe allows for effective visualization and discrimination of MCF-7 cancer cells from NIH-3T3 normal cells in a high contrast, selective, and nonviral manner. This study thus demonstrates a flexible molecular brush approach to overcome the intrinsic drawbacks of CPEs for advanced bioimaging applications. [source] A Molecular Brush Approach to Enhance Quantum Yield and Suppress Nonspecific Interactions of Conjugated Polyelectrolyte for Targeted Far-Red/Near-Infrared Fluorescence Cell ImagingADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Kan-Yi Pu Abstract A red-fluorescent conjugated polyelectrolyte (CPE, P2) is grafted with dense poly(ethylene glycol) (PEG) chains via click chemistry and subsequently modified with folic acid to form a molecular brush based cellular probe (P4). P4 self-assembles into a core,shell nanostructure in aqueous medium with an average size of 130 nm measured by laser light scattering. As compared to P2, P4 possesses not only a substantially higher quantum yield (11%), but also reduced nonspecific interactions with biomolecules in aqueous medium due to the shielding effect of PEG. In conjunction with its high photostability and low cytotoxicity, utilization of P4 as a far-red/near-infrared cellular probe allows for effective visualization and discrimination of MCF-7 cancer cells from NIH-3T3 normal cells in a high contrast, selective, and nonviral manner. This study thus demonstrates a flexible molecular brush approach to overcome the intrinsic drawbacks of CPEs for advanced bioimaging applications. [source] Multifunctional Dendrimer-Templated Antibody Presentation on Biosensor Surfaces for Improved Biomarker DetectionADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Hye Jung Han Abstract Dendrimers, with their well-defined globular shape and high density of functional groups, are ideal nanoscale materials for templating sensor surfaces. This work exploits dendrimers as a versatile platform for capturing biomarkers with improved sensitivity and specificity. The synthesis, characterization, fabrication, and functional validation of the dendrimer-based assay platform are described. Bifunctional hydroxyl/thiol-functionalized G4-polyamidoamine (PAMAM) dendrimer is synthesized and immobilized on the polyethylene-glycol (PEG)-functionalized assay plate by coupling PEG-maleimide and dendrimer thiol groups. Simultaneously, part of the dendrimer thiol groups are converted to hydrazide functionalities. The resulting dendrimer-modified surface is coupled to the capture antibody in the Fc region of the oxidized antibody. This preserves the orientation flexibility of the antigen binding region (Fv) of the antibody. To validate the approach, the fabricated plates are further used as a solid phase for developing a sandwich-type enzyme-linked immunosorbent assay (ELISA) to detect IL-6 and IL-1,, important biomarkers for early stages of chorioamnionitis. The dendrimer-modified plate provides assays with significantly enhanced sensitivity, lower nonspecific adsorption, and a detection limit of 0.13,pg,mL,1 for IL-6 luminol detection and 1.15,pg,mL,1 for IL-1, TMB detection, which are significantly better than those for the traditional ELISA. The assays were validated in human serum samples from a normal (nonpregnant) woman and pregnant women with pyelonephritis. The specificity and the improved sensitivity of the dendrimer-based capture strategy could have significant implications for the detection of a wide range of cytokines and biomarkers since the capture strategy could be applied to multiplex microbead assays, conductometric immunosensors, and field-effect biosensors. [source] Time Controlled Protein Release from Layer-by-Layer Assembled Multilayer Functionalized Agarose HydrogelsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Sumit Mehrotra Abstract Axons of the adult central nervous system exhibit an extremely limited ability to regenerate after spinal cord injury. Experimentally generated patterns of axon growth are typically disorganized and randomly oriented. Support of linear axonal growth into spinal cord lesion sites has been demonstrated using arrays of uniaxial channels, templated with agarose hydrogel, and containing genetically engineered cells that secrete brain-derived neurotrophic factor (BDNF). However, immobilizing neurotrophic factors secreting cells within a scaffold is relatively cumbersome, and alternative strategies are needed to provide sustained release of BDNF from templated agarose scaffolds. Existing methods of loading the drug or protein into hydrogels cannot provide sustained release from templated agarose hydrogels. Alternatively, here it is shown that pH-responsive H-bonded poly(ethylene glycol)(PEG)/poly(acrylic acid)(PAA)/protein hybrid layer-by-layer (LbL) thin films, when prepared over agarose, provided sustained release of protein under physiological conditions for more than four weeks. Lysozyme, a protein similar in size and isoelectric point to BDNF, is released from the multilayers on the agarose and is biologically active during the earlier time points, with decreasing activity at later time points. This is the first demonstration of month-long sustained protein release from an agarose hydrogel, whereby the drug/protein is loaded separately from the agarose hydrogel fabrication process. [source] Delivery of Nucleic Acids through the Controlled Disassembly of Multifunctional NanocomplexesADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Mahmoud Elsabahy Abstract In this study, novel pH-responsive polyion complex micelles (PICMs) were developed for the efficient delivery of nucleic acid drugs, such as antisense oligonucleotide (AON) and short interfering RNA (siRNA). The PICMs consisted of a poly(amidoamine) (PAMAM) dendrimer,nucleic acid core and a detachable poly(ethylene glycol)- block -poly(propyl methacrylate- co -methacrylic acid) (PEG- b -P(PrMA- co -MAA)) shell. The micelles displayed a mean hydrodynamic diameter ranging from 50 to 70,nm, a narrow size distribution, and a nearly neutral surface charge. They could be lyophilized without any additives and stored in dried form. Upon redispersion in water, no change in complexation efficiency or colloidal properties was observed. Entry of the micelles into cancers cells was mediated by a monoclonal antibody fragment positioned at the extremity of the PEG segment via a disulfide linkage. Upon cellular uptake and protonation of the MAA units in the acidic endosomal environment, the micelles lost their corona, thereby exposing their positively charged endosomolytic PAMAM/nucleic acid core. When these pH-responsive targeted PICMs were loaded with AON or siRNAs that targeted the oncoprotein Bcl-2, they exhibited a greater transfection activity than nontargeted PICMs or commercial PAMAM dendrimers. Moreover, their nonspecific cytotoxicity was lower than that of PAMAM. The pH-responsive PICMs reported here appear as promising carriers for the delivery of nucleic acids. [source] Protein Immobilization: Capturing Complex Protein Gradients on Biomimetic Hydrogels for Cell-Based Assays (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Mater. A versatile microfluidic strategy to rapidly and selectively immobilize gradients of virtually any desired protein on soft poly(ethylene glycol) (PEG) hydrogel surfaces is developed by S. Cosson et al. on page 3411. The selectivity and orthogonality of the chosen protein immobilization schemes allows for forming parallel and orthogonal overlapping gradients of multiple proteins. This platform can be exploited to perform a wealth of cell-based assays on biomimetic surfaces. [source] Solid-State NMR Investigations of the Unusual Effects Resulting from the Nanoconfinement of Water within Amphiphilic Crosslinked Polymer NetworksADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Ryutaro Ohashi Abstract Two types of solid-state 19F NMR spectroscopy experiments are used to characterize phase-separated hyperbranched fluoropolymer,poly(ethylene glycol) (HBFP,PEG) crosslinked networks. Mobile (soft) domains are detected in the HBFP phase by a rotor-synchronized Hahn echo under magic-angle spinning conditions, and rigid (hard) domains by a solid echo with no magic-angle spinning. The mobility of chains is detected in the PEG phase by 1H,,,13C cross-polarization transfers with 1H spin-lock filters with and without magic-angle spinning. The interface between HBFP and PEG phases is detected by a third experiment, which utilized a 19F,,,1H,(spin diffusion),1H,,,13C double transfer with 13C solid-echo detection. The results of these experiments show that composition-dependent PEG inclusions in the HBFP glass rigidify on hydration, consistent with an increase in macroscopic tensile strength. [source] Capturing Complex Protein Gradients on Biomimetic Hydrogels for Cell-Based AssaysADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Steffen Cosson Abstract A versatile strategy to rapidly immobilize complex gradients of virtually any desired protein on soft poly(ethylene glycol) (PEG) hydrogel surfaces that are reminiscent of natural extracellular matrices (ECM) is reported. A microfluidic chip is used to generate steady-state gradients of biotinylated or Fc-tagged fusion proteins that are captured and bound to the surface in less than 5,min by NeutrAvidin or ProteinA, displayed on the surface. The selectivity and orthogonality of the binding schemes enables the formation of parallel and orthogonal overlapping gradients of multiple proteins, which is not possible on conventional cell culture substrates. After patterning, the hydrogels are released from the microfluidic chip and used for cell culture. This novel platform is validated by conducting single-cell migration experiments using time-lapse microscopy. The orientation of cell migration, as well as the migration rate of primary human fibroblasts, depends on the concentration of an immobilized fibronectin fragment. This technique can be readily applied to other proteins to address a wealth of biological questions with different cell types. [source] Protein-Release Behavior of Self-Assembled PEG,, -Cyclodextrin/PEG,Cholesterol HydrogelsADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Frank van de Manakker Abstract This paper reports on the degradation and protein release behavior of a self-assembled hydrogel system composed of , -cyclodextrin- (,CD) and cholesterol-derivatized 8-arm star-shaped poly(ethylene glycol) (PEG8). By mixing ,CD- and cholesterol-derivatized PEG8 (molecular weights 10, 20 and 40 kDa) in aqueous solution, hydrogels with different rheological properties are formed. It is shown that hydrogel degradation is mainly the result of surface erosion, which depends on the network swelling stresses and initial crosslink density of the gels. This degradation mechanism, which is hardly observed for other water-absorbing polymer networks, leads to a quantitative and nearly zero-order release of entrapped proteins. This system therefore offers great potential for protein delivery. [source] Capillary Force Lithography: A Versatile Tool for Structured Biomaterials Interface Towards Cell and Tissue Engineering,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Kahp-Yang Suh Abstract This Feature Article aims to provide an in-depth overview of the recently developed molding technologies termed capillary force lithography (CFL) that can be used to control the cellular microenvironment towards cell and tissue engineering. Patterned polymer films provide a fertile ground for controlling various aspects of the cellular microenvironment such as cell,substrate and cell,cell interactions at the micro- and nanoscale. Patterning thin polymer films by molding typically involves several physical forces such as capillary, hydrostatic, and dispersion forces. If these forces are precisely controlled, the polymer films can be molded into the features of a polymeric mold with high pattern fidelity and physical integrity. The patterns can be made either with the substrate surface clearly exposed or unexposed depending on the pattern size and material properties used in the patterning. The former (exposed substrate) can be used to adhere proteins or cells on pre-defined locations of a substrate or within a microfluidic channel using an adhesion-repelling polymer such as poly(ethylene glycol) (PEG)-based polymer and hyaluronic acid (HA). Also, the patterns can be used to co-culture different cells types with molding-assisted layer-by-layer deposition. In comparison, the latter (unexposed substrate) can be used to control the biophysical surrounding of a cell with tailored mechanical properties of the material. The surface micropatterns can be used to engineer cellular and multi-cellular architecture, resulting in changes of the cell shape and the cytoskeletal structures. Also, the nanoscale patterns can be used to affect various aspects of the cellular behavior, such as adhesion, proliferation, migration, and differentiation. [source] | |||||||||||||||||||||||||||||||||||||||||||