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At least 1,369 records · Page 76Linked to original sources
PubMed2003

Evaluation of pH-dependent membrane-disruptive properties of poly(acrylic acid) derived polymers.

Anionic pH-sensitive membrane-disruptive polymers have evolved as a new class of bioactive excipients for the cytosolic delivery of therapeutic macromolecules. A large variety of anionic copolymers and analogues of poly(acrylic acid) (PA) was investigated and compared to a cationic PA copolymer. The pH-responsive membrane-disruptive properties were characterized by employing three in vitro models, such as pH dependent shift of pyrene fluorescence, liposome leakage and lysis of red blood cells. The pH-dependent increase of polarity and membrane disruption in the different model systems was in good agreement for all tested PA polymers. The efficacy of polymer-induced membrane disruption was concentration-dependent and significantly affected by the composition of the membrane. The sensitivity of relatively complex membranes of mammalian cells can be ranked between plain diphosphatidylcholine (DPPC) liposomal membranes and the more rigid cholesterol-containing DPPC membranes. Among the various studied PA polymers, medium and low molecular poly(ethacrylic acid) (PEA) and poly(propacrylic acid) (PPA) were identified as displaying significant pH-dependent disruptive activity. Relative to the disruptive cationic PA polymer (PDMAEM) the ranking is PEA < PPA < PDMAEM. The fine tuning of the pH-responsive hydrophilic-hydrophobic balance is likely to be responsible for the superior effect of PEA and PPA compared to other anionic PA polymers. This thorough investigation of a large variety of different anionic PA polymers and the comparison with an efficient, although rather toxic cationic PA polymer provides a good assessment for further therapeutic applications.

Acrylic Resins↗
PubMed2004

Development of acrylic-based copolymers for oral insulin delivery.

We developed nanospheres of crosslinked networks of methacrylic acid grafted with poly(ethylene glycol), and acrylic acid grafted with poly(ethylene glycol) nanospheres for use as oral insulin delivery devices. The copolymer nanospheres were synthesized via free-radical precipitation/dispersion. The average particle diameter of the copolymer gel nanospheres at various physiologically relevant pH values was characterized using photon correlation spectroscopy. Their size increased dramatically as the surrounding pH rose above the pK(a) of the network. The nanospheres ranged in diameters from 200 nm at pH of 2.0 to 2 microm at pH around 6.0. Insulin was loaded into the copolymers at levels of 9.33 and 9.54 mg per 140 mg solid sample, by partitioning from concentrated insulin solutions. In vitro studies were performed to study the passage of the insulin-loaded copolymer samples in the gastrointestinal tract. Insulin was entrapped at low pH (pH=3.0) but released at more neutral pH (pH=7.0). Animal studies were performed to investigate the abilities of insulin-loaded copolymer samples to influence the serum glucose levels of rats. In studies with diabetic rats, the serum glucose level was lower than control values for the animals that received the insulin-loaded copolymers and lasted for at least 6 h. The insulin loaded copolymer nanospheres caused a significant reduction of serum glucose with respect to that of a control animal.

Acrylates↗
PubMed2004

Polycomplexes of poly(acrylic acid) with streptomycin sulfate and their antibacterial activity.

Complex formation between streptomycin sulfate and poly(acrylic acid) has been studied in aqueous solutions by turbidimetric, potentiometric and viscometric methods as well as by FTIR spectroscopy. It was shown that these polycomplexes are stabilized by electrostatic interactions. The solubility of polycomplexes was examined as a function of pH and it was found that at pH values below 3.1 the polycomplexes undergo complete dissociation or dissolution. The antimicrobial activity of the drug and its polycomplex was evaluated using Sarcina sp. as a model organism. It was demonstrated that the polycomplexes have an antimicrobial activity on the same level as the free drug.

Acrylic Resins↗
PubMed1998

Drug diffusion and binding in ionizable interpenetrating networks from poly(vinyl alcohol) and poly(acrylic acid).

Hydrogels of poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), and their interpenetrating networks (IPNs) were prepared using glutaraldehyde and ethylene glycol dimethacrylate as crosslinking agents. The hydrogels were characterized by measuring their equilibrium polymer volume fraction, equilibrium swelling ratio, and mesh size. Drug and protein diffusion through these hydrogels were studied. Solutes studied included theophylline, vitamin B12 and myoglobin. The ratio of PVA and PAA in the IPNs was varied to study the effect of ionic polymer content on the polymer/drug interactions and on the drug diffusion rate. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to analyze the polymer/drug binding interactions. It was concluded that drug diffusion may be impeded by associated drug binding, especially in IPN hydrogels containing high amounts of PAA.

Acrylic Resins↗
PubMed1998

Covalent coupling of immunoglobulin G to a poly(vinyl)alcohol-poly(acrylic acid) graft polymer as a method for fabricating the interfacial-recognition layer of a surface plasmon resonance immunosensor.

The synthesis of a terminally thiolated poly(vinyl)alcohol (PVA) grafted with Poly (acrylic acid) (PAA) side chains is described. The PVA-PAA graft polymer (PVAg) was end-tethered to silver surfaces via the terminal thiol functionality and the resultant mobile, hydrophilic polymer matrix exploited for the covalent immobilization of large quantities of polyclonal goat (anti-hIgG) antibody (IgG) with low levels of non-specific adsorption. An SPR immunosensor, fabricated with an IgG-PVA-silver interfacial layer proved capable of performing a sensitive label-free assay of human IgG antigen (hIgG) with minimal non-specific binding interference. A detection limit (DL) for hIgG from serum of 0.8 microgram/ml (5 nM) and an assay sensitivity of 0.66 ng hIgG/mm2/nM are reported.

Acrylic Resins↗
PubMed2003

Structure-activity relationships of novel anti-malarial agents: part 5. N-(4-acylamino-3-benzoylphenyl)-[5-(4-nitrophenyl)-2-furyl]acrylic acid amides.

We have developed the [5-(4-nitrophenyl)-2-furyl]acrylic acid substituted benzophenone 4g as a novel lead for anti-malarial agents. Here, we demonstrated that the acyl residue at the 2-amino group of the benzophenone core structure has to be a phenylacetic acid substructure substituted in its para-position with methyl or other substituents of similar size. The trifluoromethyl substituted derivative displayed an IC(50) of 47 nM against the multi-drug resistant Plasmodium falciparum strain Dd2.

Acrylates↗
PubMedDate not supplied

Characteristic dye absorption peaks found in the FTIR spectra of coloured acrylic fibres.

The improved quality of spectra recorded using FTIR-microspectroscopy has meant that a lot more information is now obtainable from the spectra of dyed acrylic fibres. In addition to the main absorptions produced by the polymer material, additional absorptions resulting from the fibre dye are often present. An attempt has been made to explain some of the strongest and most frequently seen dye bands with the aid of spectra obtained from fibres treated with known dyes. Provided the dye concentration in the fibre is sufficient, it is possible to make some general observations on the type of dyes which have been used. Further investigation in conjunction with HPLC or FTIR-Raman spectroscopy would be useful.

Acrylates↗
PubMed2000

Molecularly imprinted fluorescent-shift receptors prepared with 2-(trifluoromethyl)acrylic acid.

Methacrylic acid (MAA) and 2-(trifluoromethyl)acrylic acid (TFMAA) were used to prepare molecularly imprinted polymers exhibiting diastereoselectivity for cinchona alkaloids. Fluorescent spectra of the cinchona alkaloid exhibit a characteristic shift through binding to these polymer particles, originating most likely from the highly acidic residues in the imprinted polymers acting as a proton donator. Our results show that TFMAA based imprinted polymers can be used as polymer reagents for quantitating the cinchona alkaloid bound to the polymers without bound/free separation.

Acrylates↗
PubMed2006

Grafting of poly(ethylene glycol) onto poly(acrylic acid)-coated glass for a protein-resistant surface.

The surface of solid glass supports for samples in optical microscopy and for biosensors needs to be protein-resistant. A coating of a poly(ethylene glycol) monomethyl ether (mPEG) on the surface of the glass is one promising method for preventing the nonspecific adsorption of proteins. In this study, we have developed a novel technique for achieving an optimal coverage of a glass surface with mPEG to prevent protein adhesion. A clean glass substrate previously treated with (3-aminopropyl)dimethylethoxysilane (APDMES) was treated sequentially with poly(acrylic acid) and subsequently a primary amine derivative of mPEG in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The resultant glass surface was demonstrated to be highly protein-resistant, and the adsorption of bovine serum albumin decreased to only a few percentage points of that on a glass surface treated with APDMES alone. Furthermore, to extend the present method, we also prepared a glass substrate on which biotinylated poly(ethylene glycol) was cografted with mPEG, and biotinylated myosin subfragment-1 (biotin-S1) was subsequently immobilized on this substrate by biotin/avidin chemistry. Actin filaments were observed to glide on the biotin-S1-coated glass surface in the presence of ATP, and thus, the method is capable of immobilizing the protein specifically without any loss in its biological function.

Acrylic Resins↗
PubMed1979

Phenylalanine ammonia-lyase: enzymic conversion of 3-(1,4-cyclohexadienyl)-L-alanine to trans-3-(1,4-cyclohexadienyl)acrylic acid.

The phenylalanine analogue 3-(1,4-cyclohexadienyl)-L-alanine is converted to the hitherto unknown cinnamate analogue trans-3-(1,4-cyclohexadienyl)acrylic acid by L-phenylalanine ammonia-lyase (EC 4.3.1.5) from maize, potato, or Rhodotorula glutinis. The structure assigned to the product is confirmed by its 1H nuclear magnetic resonance spectrum and by the chemical synthesis to be described in a subsequent paper. On comparing the above substrate analogue with L-phenylalanine, the Km was lowered only slightly but kcat was reduced 14--40-fold depending on the source of the enzyme. Because the compounds closely resemble each other in size and hydrophobic properties, this lowering of kcat may be attributed to the electronic effect of replacing the pi electrons of the aromatic system by those of a double bond. Correct alignment at the active site appears to depend upon the space-filling properties of the ring system; open chain analogues that retain the gamma, beta double bond were found to be inhibitors, not substrates.

Acrylates↗
PubMedDate not supplied

Poly(N-isopropylacrylamide)-based semi-interpenetrating polymer networks for tissue engineering applications. 1. Effects of linear poly(acrylic acid) chains on phase behavior.

Poly(N-isopropylacrylamide)-based [P(NIPAAm)-based] semi-interpenetrating polymer networks (semi-IPNs), consisting of P(NIPAAm)-based hydrogels and linear poly(acrylic acid) [P(AAc)] chains, were synthesized, and the effects of the P(AAc) chains on semi-IPN injectability and phase behavior were analyzed. In P(NIPAAm)- and P(NIPAAm-co-AAc)-based semi-IPN studies, numerous reaction conditions were varied, and the effects of these factors on semi-IPN injectability, transparency, phase transition, lower critical solution temperature (LCST), and volume change were examined. The P(AAc) chains did not significantly affect the LCST or volume change of the semi-IPNs, compared to control hydrogels. However, the P(AAc) chains affected the injectability, transparency, and phase transition of the matrices, and these effects were dependent on chain amount and molecular weight (MW) and on interactions between the P(AAc) chains and the solvent and/or copolymer chains in P(NIPAAm-co-AAc) hydrogels. These results can be used to design "tailored" P(NIPAAm)-based semi-IPNs that have the potential to serve as functional scaffolds in tissue engineering applications.

Acrylic Resins↗
PubMedDate not supplied

Immobilization of galactose ligands on acrylic acid graft-copolymerized poly(ethylene terephthalate) film and its application to hepatocyte culture.

Surface modification of argon-plasma-pretreated poly(ethylene terephthalate) (PET) films via UV-induced graft copolymerization with acrylic acid (AAc) was carried out. Galactosylated surfaces were then obtained by coupling a galactose derivative (1-O-(6'-aminohexyl)-D-galactopyranoside) to the AAc graft chains with the aid of a water-soluble carbodiimide (WSC) and N-hydroxysulfosuccinimide (sulfo-NHS). The modified PET films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and water contact-angle measurements. The galactosylated PET films were used as substrates for hepatocyte culture. The effects of surface carboxyl group concentration on the extent of galactose ligand immobilization, the extent of hepatocyte attachment, and the surface morphology were investigated. The amount of the galactose ligands immobilized on the PET surface increased with the AAc polymer graft concentration. AFM images revealed that the surface roughness of the PET film increased after graft copolymerization with AAc, but did not change appreciably with the subsequent immobilization of the galactose ligands. At the surface carboxyl group concentration of about 0.56 micromol/cm(2) or galactose ligand concentration of about 0.51 micromol/cm(2), the hepatocyte culture on the galactosylated surface exhibited the optimum concentration and physiological functions and formed aggregates or spheroids after just 1 day of culture. The albumin and urea synthesis functions of these hepatocytes were comparable to or higher than those of the hepatocytes cultured on the collagen-modified PET substrates.

Acrylates↗
PubMedDate not supplied

Photocurable biodegradable liquid copolymers: synthesis of acrylate-end-capped trimethylene carbonate-based prepolymers, photocuring, and hydrolysis.

Various photocurable liquid biodegradable trimethylene carbonate (TMC)-based (co)oligomers were prepared by ring-opening (co)polymerization of TMC with or without L-lactide (LL) using low molecular weight poly(ethylene glycol) (PEG) (mol wt 200, 600, or 1000) or trimethylolpropane (TMP) as an initiator. Resultant (co)oligomers were pastes, viscous liquids, or liquids at room temperature, depending on the monomer composition and monomer/initiator ratio. Liquid (co)oligomers were subsequently end-capped with acrylate groups. Upon visible-light irradiation in the presence of camphorquinone as a radical generator, rapid liquid-to-solid transformation occurred to produce photocured solid. The photocuring yield increased with photoirradiation time, photointensity, and camphorquinone concentration. The photocured polymers derived from low molecular weight PEG (PEG200) and TMP exhibited much reduced hydrolysis potential compared with PEG1000-derived polymers in terms of weight loss, water uptake, and swelling depth. Force-distance curve measurements by nanoindentation using atomic force microscopy clearly showed that Young's moduli of the photocured polymer films decreased with increasing hydrolysis time. Their potential biomedical applications are discussed.

Acrylates↗
PubMedDate not supplied

Polymeric grafting of acrylic acid onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate): surface functionalization for tissue engineering applications.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt processed disks and solvent cast films were modified by graft co-polymerization with acrylic acid (AAc) in methanol solution at ambient temperature using gamma irradiation (dose rate of 4.5 kGy/h). To assess the presence of carboxylic acid groups on the surface, reaction with pentafluorophenol was performed prior to X-ray photoelectron spectroscopy analysis. The grafting yield for all samples increased with monomer concentration (2-15%), and for the solvent cast films, it also increased with dose (2-9 kGy). However, the grafting yield of the melt processed disks was largely independent of the radiation dose (2-8 kGy). Toluidine blue was used to stain the modified materials facilitating visual information about the extent of carboxylic acid functionalization and depth penetration of the grafted copolymer. Covalent linking of glucosamine to the functionalized surface was achieved using carbodiimide chemistry verifying that the modified substrates are suitable for biomolecule attachment.

Acrylates↗
PubMed2006

pH dependence and protein selectivity of poly(ethyleneimine)/poly(acrylic acid) multilayers studied by in situ ATR-FTIR spectroscopy.

The selective interaction between polyelectrolyte multilayers (PEM) consecutively adsorbed from poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC) and a binary mixture containing concanavalin A (COA) and lysozyme (LYZ) based on electrostatic interaction is reported. The composition and structure of the PEM and the uptake of proteins were analyzed by in situ attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy, and the morphology and thickness were characterized by atomic force microscopy (AFM) and ellipsometry. The PEM dissociation degree and charge state and the protein adsorption were shown to be highly dependent on the outermost layer type and the pH in solution. High protein uptake was obtained under electrostatically attractive conditions. This was used to bind selectively one protein from a binary mixture of LYZ/COA. In detail it could be demonstrated that six-layered PEM-6 at pH = 7.3 showed a preferential sorption of positively charged LYZ, while at PEM-5 and pH = 7.3 negatively charged COA could be selectively bound. No protein sorption from the binary mixture was observed at pH = 4.0 for both PEM, when COA, LYZ, and the outermost PEI layer of PEM-5 were positively charged or the outermost PAC layer of PEM-6 was neutral. Furthermore, from factor analysis of the spectral data the higher selectivity was found for PEM-5 compared to PEM-6. Increasing the ionic strength revealed a drastic decrease in the selectivity of both PEM. Evidence was found that the proteins were predominantly bound at the surface and to a minor extent in the bulk phase of PEM. These results suggest possible working regimes and application fields of PEI/PAC multilayer assemblies related to the preparative separation of binary and multicomponent protein mixtures (biofluids, food) as well as to the design of selective protein-resistant surfaces.

Acrylic Resins↗
PubMed2006

Controlling network structure in degradable thiol-acrylate biomaterials to tune mass loss behavior.

Degradable thiol-acrylate materials were synthesized from the mixed-mode polymerization of a diacrylate poly(ethylene glycol) (PEG) monomer with thiol monomers of varying functionalities to control the final network structure, ultimately influencing the material's degradation behavior and properties. The influence of the concentration of thiol groups and monomer functionality on the mass loss profiles were examined experimentally and theoretically. Mass loss behavior was also predicted for networks with varying extents of cyclization, PEG molecular weight, and backbone chain length distributions. Experimental results indicate that increasing the thiol concentration from 10 to 50 mol % shifted the reverse gelation time from 35 to 8 days and the extent of mass loss at reverse gelation from 75 to 40%. Similarly, decreasing the thiol functionality from 4 to 1 shifted the reverse gelation time from 18 to 8 days and the mass loss extent at reverse gelation from 70 to 45%.

Acrylates↗
PubMedDate not supplied

Chitosan-poly(acrylic acid): mechanism of complex formation and potential industrial applications.

The food industry is interested in polyelectrolytic coagulants of natural origin for the clarification of food beverages and the recovery of colloidal and dispersed particles from processing waste streams. This paper discusses potential industrial applications of recent findings on polymer complex formation obtained with a chitosan-poly(acrylic acid) model system. Process recommendations could be made on the basis of the ionic strength, pH, and charged group concentration of the fluid to be treated. Ionic strength does not affect the complex formation process. The amount of chitosan in the complex formed is controlled by the solution pH. The mechanism of complex formation indicates that pH measurements could be used to monitor the coagulation process.

Acrylic Resins↗
PubMed2002

Efficient pi-facial control in the ene reaction of nitrosoarene, triazolinedione, and singlet oxygen with tiglic amides of the bornane-derived sultam as chiral auxiliary: an economical synthesis of enantiomerically pure nitrogen- and oxygen-functionalized acrylic acid derivatives.

The ene reaction of 4-nitronitrosobenzene (ArNO), N-phenyl-1,2,4-triazoline-3,5-dione (PTAD), and singlet oxygen (1O2) with the optically active tiglic-acid derivatives of Oppolzer's bornane-derived sultam affords the respective ene products regioselectively in excellent diastereoselectivity (de up to 99%) and in good yield (55-90%). The enophiles ArNO and PTAD give with the methyl-substituted substrate exclusively the like-configured ene adduct, while 1O2 leads to an 83:17 diastereomeric mixture. With the sterically more demanding isopropyl-substituted derivative even the smallest enophile 1O2 forms exclusively the like diastereomer. The high diastereoselectivity is rationalized in terms of the proper conformational alignment of the substrate and a preferred enophilic attack from the C(beta)-re face of the double bond. This concept offers an efficient synthetic route to enantiomerically pure nitrogen- and oxygen-functionalized acrylic acid derivatives.

Acrylates↗