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PubMed1978

Short-time hemodiafiltration using polymethylmethacrylate hemodiafilter.

Three times 3 hr/wk hemodiafiltration (simultaneous hemofiltration and dialysis: HDF) using Toray HDF system has been carried out on 4 patients. Filters used were Toray Filtryzers (membrane: polymethylmethacrylate, surface area 1.15 M2) with a dialysate flow of 500 ml/min. Nine to 10 L of body fluid was removed and 7-8 L of substitution fluid was reinfused distal to the filter (postdilution). Short-time HDF was favorable accepted by the patients. Blood pressure was stable, and disequilibrium syndrome negligible. Clinical courses as well as laboratory findings of the patients were satisfactory. The reduction rate of middle to larger molecules was 20 to 100% higher compared to conventional HD as measured by chromatogram. Loss of amino acids was about 3 gm/treatment. Reduction of hormones was negligible and no depletion syndrome was observed throughout the observation period up to 10 mos. Acidosis was corrected within 3-4 hrs. Elevated blood concentration of lactate and acetate gradually decreased to a pretreatment level within 2-3 hrs after termination of the procedure. Removal of middle molecules by HDF, in addition to removal of small molecules by conventional hemodialysis, is considered to be the treatment of choice for uremic patients.

Acrylic Resins↗
PubMed1989

Trace-level determination of 3'-azido-3'-deoxythymidine in human plasma by preconcentration on a silver (I)-thiol stationary phase with on-line reversed-phase high-performance liquid chromatography.

A method was developed for the determination of 3'-azido-3'-deoxythymidine (AZT) in plasma. The method is based on the trace enrichment of AZT on a pre-column packed with a silver-loaded thiol stationary phase at pH 11.6. On-line desorption to the reversed-phase liquid chromatographic system is performed by injecting a plug of 50 microliters of 1 M perchloric acid on the silver (I)-thiol pre-column. Two different sample pretreatment methods - protein precipitation with perchloric acid and on-line clean-up via a polymeric PRP-1 pre-column - were applied for the determination of AZT in human plasma. The latter method allows the direct injection of plasma samples into the analytical system and can therefore easily be automated. With both methods detection limits in the order of 10(-8) M AZT were obtained after preconcentration of 1.0 ml of plasma, using UV detection at 267 nm.

Autoanalysis↗
PubMed2006

Effect of molecular weight and ionic strength on the formation of polyelectrolyte complexes based on poly(methacrylic acid) and chitosan.

Chitosan/poly(methacrylic acid) complexes, CS/PMAA, were prepared via dropwise addition of a solution of PMAA to a solution of chitosan in acetic acid 2 wt %. The increase in molecular weight of PMAA inhibited the formation of insoluble complexes, while the increase in ionic strength first favored the formation of the complex followed by inhibiting it at higher concentrations. These observations were related to a description of polyelectrolyte complexation that was strongly dependent on macromolecular dimensions, both in terms of molecular weight and of coil expansion/contraction driven by polyelectrolyte effect.

Chitosan↗
PubMed1999

Swelling and ketoprofen release characteristics of thermo- and pH-responsive copolymer gels.

Swelling-controlled drug delivery copolymer gels were newly synthesized by introducing thermo- and pH-responsive methacryloyl-glycine (MA-Gly) or pH-responsive methacrylic acid (MA-Ac) for comparison with thermoresponsive acryloyl-L-proline ethyl ester (A-ProOEt). A homopolymer gel of A-ProOEt was kept at degrees of swelling that were less than 0.5 at a pH from 2.5 to 7.5 at 37 degrees C. The thresholds of swelling for copolymer gels consisting of A-ProOEt/MA-Gly and A-ProOEt/MA-Ac with a composition of 40/60 mol% were found to be pH 3.0 and pH 5.5, respectively, in buffer solutions at 37 degrees C. The diffusion characteristics of 2-(3-benzoylphenyl)propionic acid (ketoprofen) from such copolymer gels was evaluated in buffer solutions at pH's more than 5.5, and it was found that A-ProOEt/MA-Gly gel possesses a case II transport mechanism that is completely linear time dependent in both the amount diffused and the penetrating swelling front position. On the other hand, A-ProOEt/MA-Ac gel exhibited a non-Fickian (or anomalous) diffusion behavior under the same conditions.

Diffusion↗
PubMed1990

[A novel reactive polymer bonding composite resin to ground tooth substrates].

Methyl methacrylate (MMA)-p-styrene sulfonic acid copolymer (MS) was prepared and its adhesion to ground tooth substrates was evaluated. MS is crosslinked with Ca2+ supplied by hydroxyapatite in the smeared layer on the ground enamel and dentin, and sticks to their surface. The adhesion mechanism of MS is quite different from that of interpenetration and polymerization of monomers. The bonding strength of MMA-TBB resin to the tooth treated with an aqueous solution of MS was 11-12 MPa but that of MMA-BPO.DMPT resin was only 2.5 M Pa. Free sulfonic acids remaining in the immobilized MS disturbed the initiation of polymerization in MMA-BPO.DMPT resin. A photocurable liner, triethylene glycol dimethacrylate (TEGDMA) activated by d,l-comphorquinone (CQ), N-phenylglycine (NPG), which was polymerized in an acidic condition by irradiation, was chosen to obtain a high bond strength to the cross-linked MS on the tooth. The bond strength of TEGDMA-CQ.NPG on the tooth treated with an aqueous mixture of 10 wt% MS 7 (MMA: 70 mol%, p-styrene sulfonic acid: 30 mol%) and FeCl3 ([Fe3+]/[SO3-] = 0.28) was 10-11 MPa. The observation of the fractured surface after the tensile test and interface between precipitated MS and tooth indicated that the liner did not interpenetrate into the dentin through the immobilized MS on the tooth. These results indicated that the polymer reaction of MS with Ca2+ was important in the adhesion. In conclusion, MS is a reactive polyelectrolyte which adheres well to tooth substrates and prevents pulp irritation by hindering the penetration of the monomer.

Adhesiveness↗
PubMed2006

Influence of stereoregularity of the polymer chain on interactions with surfactants: binding of cetylpyridinium chloride by isotactic and atactic poly(methacrylic acid).

Association of a cationic surfactant cetylpyridinium chloride, CPC, with isotactic and atactic poly(methacrylic acid), i-PMA and a-PMA, respectively, in aqueous 0.01 M NaCl solutions was studied by pH and fluorescence measurements in conjunction with potentiometric studies using a surfactant-sensitive membrane electrode. pH measurements have demonstrated that the presence of an oppositely charged surfactant increases ionization of carboxyl groups on PMA at low degrees of neutralization. The increase is more pronounced in the case of i-PMA. The isotactic form of PMA is not soluble in water at zero degrees of neutralization but can be rendered soluble by the addition of CPC at the surfactant to a polyion molar ratio of around 0.4. In the solubilized complex, the positive charge of the CPC molecule is facing the polar solvent, whereas surfactant tails are oriented toward the i-PMA compact coil. Binding isotherms and cooperativity parameters show that chain tacticity has an important influence on the interaction of cetylpyridinium cation with polymethacrylate anion. At the onset of cooperative binding, the association is stronger with i-PMA than with the atactic form, as demonstrated by lower CAC values and higher values of the cooperativity parameters. In contrast, more surfactant is bound by a-PMA in the region where polyion becomes saturated with surfactant ions. Results are interpreted by taking into account local chain conformations as obtained from quantum mechanical semiempirical molecular orbital calculations. Greater hydrophobicity and possibly higher charge density of i-PMA on one hand and more flexibility of the a-PMA chain on the other are held responsible for these observations.

Cations↗
PubMed1998

Copolymers of N-isopropylacrylamide can trigger pH sensitivity to stable liposomes.

Stable liposomes were rendered pH-sensitive by complexation to a polymer that undergoes marked temperature- and pH-dependent water solubility changes. The N-isopropylacrylamide-methacrylic acid copolymer was prepared with or without octadecyl acrylate. At pH below the phase transition of the polymer, egg phosphatidylcholine liposomes quickly released a part of their contents only when associated with the octadecyl aliphatic chain grafted polymer at 37 degrees C. Similarly, sterically stabilized liposomes also quickly released a significant part of the entrapped fluorescent markers at pH 5.5-4.9, values corresponding to those of endosomes/lysosomes. This new pH-sensitive liposome-polymer system may further improve the efficiency of liposomal drug delivery.

Acrylamides↗
PubMed1987

Incorporation into human enamel of fluoride slowly released from a sealant in vivo.

Fluoride incorporation into human enamel from an experimental sealant resin in vivo was investigated. The sealant consisted of a newly synthesized methacryloyl fluoride-methyl methacrylate (MF-MMA) copolymer resin, which contains acidic fluoride covalently bonded to carbonyl groups and releases fluoride ions slowly by hydrolysis in an aqueous environment. This experimental sealant was applied to the enamel of permanent pre-molars and the control sealant without MF-MMA copolymer to that of the contralateral teeth. Fluoride concentration was determined by an enamel biopsy procedure with acid-etching four weeks after the sealant application. As much as 3500 ppm fluoride was found to be deposited at 10 microns depth in the enamel under the MF-MMA copolymer sealant. The increase in fluoride concentration was significant even at 60 microns. Of the fluoride incorporated into the enamel, from 70 to 80% was present as a tightly bound form. This resin sealant is expected to protect the enamel from caries attack even after detachment of the sealant.

Boranes↗
PubMed2001

Oriented antibody immobilization to polystyrene macrocarriers for immunoassay modified with hydrazide derivatives of poly(meth)acrylic acid.

BACKGROUND: Hydrophobic polystyrene is the most common material for solid phase immunoassay. Proteins are immobilized on polystyrene by passive adsorption, which often causes considerable denaturation. Biological macromolecules were found to better retain their functional activity when immobilized on hydrophilic materials. Polyacrylamide is a common material for solid-phase carriers of biological macromolecules, including immunoreagents used in affinity chromatography. New macroformats for immunoassay modified with activated polyacrylamide derivatives seem to be promising. RESULTS: New polymeric matrices for immunoassay in the form of 0.63-cm balls which contain hydrazide functional groups on hydrophilic polymer spacer arms at their surface shell are synthesized by modification of aldehyde-containing polystyrene balls with hydrazide derivatives of poly(meth)acrylic acid. The beads contain up to 0.31 micromol/cm2 active hydrazide groups accessible for covalent reaction with periodate-oxidized antibodies. The matrices obtained allow carrying out the oriented antibody immobilization, which increases the functional activity of immunosorbents. CONCLUSIONS: An efficient site-directed antibody immobilization on a macrosupport is realized. The polymer hydrophilic spacer arms are the most convenient and effective tools for oriented antibody coupling with molded materials. The suggested scheme can be used for the modification of any other solid supports containing electrophilic groups reacting with hydrazides.

Antibodies↗
PubMed2004

The influence of the copolymer composition on the diltiazem hydrochloride release from a series of pH-sensitive poly[(N-isopropylacrylamide)-co-(methacrylic acid)] hydrogels.

A series of poly[(N-isopropylacrylamide)-co-(methacrylic acid)] (P[(N-iPAAm)-co-(MAA)]) hydrogels was investigated to determine the composition that exhibits a better pH-modulated release of diltiazem hydrochloride (DIL.HCl). For this purpose hydrogel slabs were loaded with DIL.HCl by the immersion method, and its release under acidic medium (0.1N HCl, pH 1.2) and in phosphate buffer pH 7.2, using United States Pharmacopeia (USP) 24 Apparatus 1, was investigated. According to the results from the slabs, copolymers with 85% mol N-iPAAm content were selected to prepare tablets with different particle size. The effect of pH and particle size changes on DIL.HCl release from these last hydrogel tablets was investigated by a stepwise pH variation of the dissolution medium. The amount of DIL.HCl released from high N-iPAAm content copolymer slabs under acidic pH medium was not only very low but it was also released at a slow rate. In the 85% N-iPAAm tablets, significant differences between and within release profiles were found as a function of particle size and pH, respectively. A relationship between particle size and release rate has been found. The lower DIL.HCl release at acidic pH from enriched N-iPAAm copolymers is interpreted by a cooperative thermal- and pH-collapse. Although for the whole range of copolymer composition a dependence of the equilibrium of swelling on the pH was found, DIL.HCl release experiments indicated that hydrogels with 85% mol N-iPAAm are the more adequate to be used for modulated drug delivery systems. Additionally, the particle size of the tablet can be used to tailor the release rate.

Acrylamides↗
PubMed2003

Characterization of the membrane-destabilizing properties of different pH-sensitive methacrylic acid copolymers.

The intracellular delivery of active biomacromolecules from endosomes into the cytoplasm generally requires a membrane-disrupting agent. Since endosomes have a slightly acidic pH, anionic carboxylated polymers could be potentially useful for this purpose since they can destabilize membrane bilayers by pH-triggered conformational change. In this study, five different pH-sensitive methacrylic acid (MAA) copolymers were characterized with respect to their physicochemical and membrane lytic properties as a function of pH. pH-dependent conformational changes were studied in aqueous solution by turbidimetry and spectrofluorimetry. The hydrophobic domains that formed upon a decrease in pH were found to be dependent on copolymer's composition. Hemolysis and cytotoxicity assays demonstrated that the presence of the hydrophobic ethyl acrylate monomer and/or sufficient protonation of the carboxylic acid groups were important parameters for efficient membrane destabilization. Excessive copolymer hydrophobicity was not associated with membrane destabilization, but resulted in high macrophage cytotoxicity. Overall, this study gave more insights into the structure-activity relationship of MAA copolymers with membrane bilayers. Gaining knowledge of modulation of the physicochemical properties of copolymers and the optimization of copolymer-lipid interactions may lead to the elaboration of much more efficient drug delivery systems.

Animals↗
PubMed2006

Ultra-fast mass fingerprinting by high-affinity capture of peptides and proteins on derivatized poly(glycidyl methacrylate/divinylbenzene) for the analysis of serum and cell lysates.

The development of support materials in mass fingerprinting is an important task required for diagnostic markers in conjunction with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The material-based approach, which we introduced as material-enhanced laser desorption/ionization (MELDI), focuses not only on different functionalities, but also emphasizes the morphology, i.e. porosity or particle size of the carrier material. As a result, it provides a quick and sensitive platform for effective binding of peptides and proteins out of different biofluids, e.g. serum, spinal fluid, urine or cell lysates, and to subsequently analyze them with MALDI-TOF MS. This approach includes a built-in desalting step for serum protein profiling and is sensitive enough to detect proteins and peptides down to 100 fmol/microL. Here we co-polymerized glycidyl methacrylate (GMA) with divinylbenzene (DVB) using thermal polymerization to yield a GMA/DVB polymer for further modifications. Different affinities have been created, such as immobilized metal ion affinity (IDA-Cu2+), reversed-phase (RP) and anion-exchanger (AX) chromatography. The diverse derivatizations and the dispersity of the particles created by different chemical synthetic approaches were confirmed by characteristic infrared (IR) peaks. The polymerization carried out by non-stirring yielded an average pore radius of 6.1 microm (macro-pores) that enhanced the binding capacity enormously by offering enlarged surface areas. Moreover, atomic absorption spectrometry (AAS) provided the metal content loaded on iminodiacetic acid (IDA) in the case of poly(GMA/DVB)-IDA-Cu2+. To summarize, the optimized MELDI approach is sensitive in its performance, extremely fast and can be adapted to robotic systems for routine analysis, allowing sample preparation in less than 5 min in contrast to the conventional surface-enhanced laser desorption/ionization (SELDI) methods.

Blood Proteins↗
PubMed2006

Organic-inorganic hybrid-nanocarrier of siRNA constructing through the self-assembly of calcium phosphate and PEG-based block aniomer.

The development of siRNA delivery systems is a major key for practical RNA therapy that holds promise for the treatment of life-threatening human diseases, yet there still exists significant difficulties in their construction because of the various requirements including high transfection efficacy, tolerability in the biological medium, and low toxicity. Here we report the novel preparation route of organic-inorganic hybrid-nanocarriers entrapping siRNA based on the self-assembly of the block aniomer, poly(ethylene glycol)-block-poly(methacrylic acid), with calcium phosphate crystals. The nanocarriers have diameters in the range of several hundreds of nanometers and revealed excellent colloidal stability due to the steric stabilization effect of the PEG palisade. The biological activity of siRNA loaded in nanocarriers was assessed using 293 cells stably expressing luciferase gene, showing the remarkably high gene silencing-efficacy without the use of any adjuvant molecules such as chroloquin. Further advantage of the system is the serum tolerability, which is of a critical issue in in vivo application.

Calcium Phosphates↗
PubMed2000

Interaction of antibodies and antigens conjugated with synthetic polyanions: on the way of creating an artificial chaperone.

Recently we have initiated the use of synthetic polyelectrolytes to mimic the action of chaperones in living cells [Dainiak et al., Biochim. Biophys. Acta 1381 (1998) 279-285]. The next step in this direction is done by the synthesis of conjugates of poly(methacrylic acid) (PMAA) with antigen, denatured glyceraldehyde-3-phosphate dehydrogenase (dGAPDH), and with monoclonal antibodies specific for dGAPDH (but not for the native protein). The pH-dependent properties of the conjugates have been studied using turbidimetry and light scattering. The antibody-PMAA and dGAPDH-PMAA conjugates were shown to interact with free dGAPDH and antibodies respectively as well as with each other. Insoluble aggregates of dGAPDH with antibody-PMAA and of antibodies with dGAPDH-PMAA are formed in acidic media. The same situation occurs in the mixture of antibody-PMAA and dGAPDH-PMAA: precipitation takes place in acidic media, whereas soluble associates are formed in neutral solutions. The size of the soluble associates and the number of conjugates in the associate could be regulated by pH. The competition of free dGAPDH and dGAPDH-PMAA for binding with antibody-PMAA and the dynamic release of refolded GAPDH, with no affinity to antibody-PMAA, into solution could be used for simulating chaperone action.

Anions↗
PubMedDate not supplied

Development and characterization of transdermal drug delivery systems for diltiazem hydrochloride.

Transdermal drug delivery system of diltiazem hydrochloride was developed to obtain a prolonged controlled drug delivery. Both the matrix diffusion controlled (MDC) and membrane permeation controlled (MPC) systems were developed. The matrix diffusion controlled systems used various combinations of hydrophilic and lipophillic polymers, whereas membrane permeation controlled systems were developed using the natural polymer chitosan. The MDC systems were prepared using the cast film method and the MPC systems by an adhesive sealing technique. Both the systems were characterized for in vitro and in vivo performance. The MDC systems were characterized for physicochemical properties such as tensile strength, moisture content, and water vapor transmission. The in vitro release studies showed that the release from the matrix diffusion controlled transdermal drug delivery systems follows a nonfickian pattern and that from the membrane permeation controlled transdermal drug delivery systems follow zero-order kinetics. The release from the matrix systems increased on increasing the hydrophilic polymer concentration, but the release from the membrane systems decrease on cross-linking of the rate controlling membrane and also on addition of citric acid to the chitosan drug reservoir gel. The in vivo studies of the selected systems showed that both systems are capable of achieving the effective plasma concentration for a prolonged period of time. The MPC system achieved effective plasma concentration a little more slowly than the MDC system, but it exhibited a more steady state plasma level for 24 hr.

Acrylates↗
PubMed1988

pH-dependent swelling and solute diffusion characteristics of poly(hydroxyethyl methacrylate-co-methacrylic acid) hydrogels.

Poly(hydroxyethyl methacrylate-co-methacrylic acid) hydrogels can swell extensively in a high-pH medium where the carboxyl groups are ionized. The swelling equilibrium is a strong function of the methacrylic acid composition of the polymer and pH of the medium. The nonionized gel structure was found to be rather insensitive to the amount of cross-linker, tetraethylene glycol dimethacrylate (TEGDMA), incorporated, within the range of 0.5 to 3%. This result is supportive of the existence of secondary interactions that shield the effect of covalent cross-links. Phenylpropanolamine (PPA) was used as a probe solute to study the diffusion characteristics of the poly(HEMA-co-MA) gels. Its diffusion coefficient in the swollen matrices of different methacrylic acid compositions at various pH's was measured via a desorption method. It is evident that these diffusion coefficients follow Yasuda's free volume theory, which expresses an exponential relationship between the solute diffusivity in a swollen polymer membrane and the reciprocal of the membrane hydration. Although interactions exist between PPA and the hydrogel matrix, these interactions are not significant enough to perturb the free volume relationship established. This observation can be explained by the high ionic strength of the system.

Acrylates↗
PubMed2001

Preliminary assessment of selected methacrylic acid--acrylic acid copolymers as factors buffering triethanolamine interacting with artificial skin sebum.

To allow cleaning of sebum ducts for acne prophylaxis the authors suggest use of triethanolamine buffered with anionic polymers of acrylic and methacrylic acid. In these preliminary researches addition of Eudragit L-100, Eudragit L-100-55 or Eudragit S-100 implicates decrease of pH of 1.49% triethahnolamine solution from 10.06 even to 7.20. Triethanolamine penetrates into the artificial skin sebum, gains hydrophylic properties, and reacted sebum increase in volume allowing mechanical remove of lipid bed. The highest triethanolamine penetration and the highest volume increase were observed after application of Eudragit S-100 complexes. Eudragit L-100 and L-100-55 proved milder action. These complexes may be applied for further examinations on acne prevention.

Acrylic Resins↗
PubMed2003

Controlled release of epidermal growth factor (EGF) from EGF-loaded polymeric nanoparticles composed of polystyrene as core and poly(methacrylic acid) as corona in vitro.

Polymeric nanoparticles composed of polystyrene (PS) as core and poly(methacrylic acid) (PMA) as corona were prepared by the dispersion copolymerization. The potential of the nanoparticles as carriers for recombinant human epidermal growth factor (EGF) was investigated. The nanoparticles showed monodispersity and good water-dispersibility. The loading content of EGF to the nanoparticles was very high due to electrostatic interaction between EGF and nanoparticles. EGF was released as a pseudo-zero order pattern after initial burst effect. The nanoparticles were sufficient for A431 cells proliferation.

DNA↗