Carboxylic Acid Groups Of Poly Research Articles

Enhancing Membrane-Disruptive Activity via Hydrophobic Phenylalanine and Lysine Tethered to Poly(aspartic acid).

Amphiphilic polymers with pH-responsive abilities have been widely used as carriers for intracellular delivery of bioactive substances, while their membrane-disruptive activity exerted on cells is a critical characteristic that determines delivery efficiency. Herein, we present a novel method to prepare amphiphilic and pH-responsive polymers by chemically tethering l-phenylalanine methyl ester and followed by Nε-carbobenzyloxy-l-lysine benzyl ester to the side carboxylic acid groups of poly(aspartic acid). The obtained phenylalanine- and lysine-grafted polymer (PAsp- g-Phe)- g-Lys demonstrated enhanced membrane-disruptive activity at pH 7.4 in comparison with that of PAsp- g-Phe. Moreover, the pH-responsive behavior of the grafted polymers caused by the significantly intensified hydrophobicity could be modulated by the tethered amount of hydrophobic amino acids with phenyl groups. The prepared amphiphilic (PAsp- g-Phe)- g-Lys could facilitate entry of calcein into NIH/3T3 and HeLa cells at physiological pH values, possibly due to local chemical destabilization of cell membranes by the interaction between the polymer and membrane bilayers. Therefore, we have provided a feasible approach to prepare pH-responsive polymers with enhanced membrane-disruptive activity, and the phenylalanine- and lysine-grafted polymers could be a potential candidate for intracellular delivery of bioactive molecules in biomedical applications.

RAFT‐mediated synthesis of poly[(oligoethylene glycol) methyl ether acrylate] brushes for biological functions

AbstractThe synthesis of poly[(oligoethylene glycol) methyl ether acrylate] [poly(OEGA)] brushes was achieved via reversible addition‐fragmentation chain transfer (RAFT) polymerization and used to selectively immobilize streptavidin proteins. Initially, gold surfaces were modified with a trithiocarbonate‐based RAFT chain transfer agent (CTA) by using an ester reaction involving a gold substrate modified with 11‐mercapto‐1‐undecanol and bis(2‐butyric acid)trithiocarbonate. poly(OEGA) brushes were then prepared via RAFT‐mediated polymerization from the surface‐immobilized CTA. The immobilization of CTA on the gold surface and the subsequent polymer formation were followed by ellipsometry, X‐ray photoelectron spectroscopy, grazing angle‐Fourier transform infrared spectroscopy, atomic force microscopy, and water contact‐angle measurements. RAFT‐mediated polymerization method gave CTA groups to grafted poly(OEGA) termini, which can be converted to various biofunctional groups. The terminal carboxylic acid groups of poly(OEGA) chains were functionalized with amine‐functionalized biotin units to provide selective attachment points for streptavidin proteins. Fluorescence microscopy measurements confirmed the successful immobilization of streptavidin molecules on the polymer brushes. It is demonstrated that this fabrication method may be successfully applied for specific protein recognition and immobilization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The compatible and mechanical properties of biodegradable poly(Lactic Acid)/ethylene glycidyl methacrylate copolymer blends

The Fourier transform infrared results suggest that the carboxylic acid groups of poly(lactic acid) (PLA) molecules react with the epoxy groups of molecules of Ethylene Glycidyl Methacrylate Copolymer (EGMC) during the reactive extrusion processes of PLAxEGMCy specimens. The tensile and tear strength values of PLAxEGMCy blown-film specimens in machine and transverse directions improve significantly, and reach their maximal values as their EGMC contents approach an optimum value of 6 wt.%. The melt shear viscosity values of PLAxEGMCy resins, measured at varying shear rates, are significantly higher than those of the PLA resin, and increase consistently with their EGMC contents. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) of PLA and PLAxEGMCy specimens reveal that the percentage crystallinity, peak melting temperature, and onset re-crystallization temperature values of PLAxEGMCy specimens reduce gradually as their EGMC contents increase. In contrast, the glass transition temperatures of PLAxEGMCy specimens increase gradually in conjunction with their EGMC contents. Demarcated porous morphology with several connected fungi-decomposed cavities was found on the surfaces of the PLAxEGMCy specimens after being buried for specific amounts of time, in which the sizes of the fungi-decomposed cavities found on the surfaces of buried PLAxEGMCy specimens reduce significantly as their EGMC contents increase. Further DMA and morphological analysis of PLAxEGMCy specimens reveal that the EGMC molecules are compatible with PLA molecules at EGMC contents equal to or less than 2 wt.% because no phase-separated EGMC droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLAxEGMCy specimens, respectively. The possible reasons for these remarkable properties of the PLA/EGMC specimens are proposed in this study.

Compatible and tearing properties of poly(lactic acid)/poly(ethylene glutaric‐co‐terephthalate) copolyester blends

AbstractFourier transform infrared and nuclear magnetic resonance results suggest that the carboxylic acid groups of poly(lactic acid) (PLA) molecules react with the hydroxyl groups of FePol (FP) molecules during the melt‐blending of PLAxFPy specimens. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) experiments of PLA and PLA/FP specimens suggest that only small amounts of poor PLA and/or FP crystals are present in their corresponding melt crystallized specimens. In fact, the percentage crystallinity, peak melting temperature, and onset re‐crystallization temperature values of PLA/FP specimens reduce gradually as their FP contents increase. However, the glass transition temperatures of PLA molecules found by DSC and DMA reduce to a minimum value as the FP contents of PLAxFPy specimens reach 6 wt %. Further DMA and morphological analysis of PLA/FP specimens reveal that FP molecules are compatible with PLA molecules at FP contents equal to or less than 6 wt %, as no distinguished phase‐separated FP droplets and tan δ transitions were found on fracture surfaces and tan δ curves of PLA/FP specimens, respectively. In contrast to PLA, the FP specimen exhibits highly deformable and tearing properties. After blending proper amounts of FP in PLA, the inherent brittle deformation and poor tearing behavior of PLA were successfully improved. Possible reasons accounting for these interesting crystallization, compatible and tearing properties of PLA/FP specimens are proposed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 913–920, 2010

Preparation of hollow composite spheres with raspberry‐like structure based on hydrogen‐bonding interaction

AbstractThe hollow composite spheres with a raspberry‐like structure were prepared by a self‐assemble heterocoagulation based on the inter‐particle hydrogen‐bonding interaction between the amide groups of hollow poly (N,N′‐methylenebisacrylamide‐co‐N‐isopropyl acrylamide) (P(MBA‐co‐NIPAAm)) microspheres and the carboxylic acid groups of poly(ethyleneglycol dimethacrylate‐co‐methacrylic acid) (P(EGDMA‐co‐MAA)) nanoparticles, in which P(EGDMA‐co‐MAA) nanoparticle acted as the corona and the hollow P(MBA‐co‐NIPAAm) microsphere behaved as the core. The control coverage of the corona particles on the surface of hollow core microspheres of P(MBA‐co‐NIPAAm)/P(EGDMA‐co‐MAA) hollow composite sphere was studied in detail through adjustment of the mass ratio between the core and corona particles. The effect of the pH on the stability of the raspberry‐like hollow spheres was investigated. The polymer particles and the resultant heterocoagulated raspberry‐like hollow spheres were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis and Magnetic Properties of Surface Coated Magnetite Superparamagentic Nanoparticles

The magnetite superparamagnetic nanoparticles were synthesized by using a co-precipitation method. The surfaces of magnetite nanoparticles were modified by carboxylic acid group of poly (3-thiophenacetic acid). The crystalline structure and the composition of core magnetite nanoparticles were not changed after surface coating with a very thin outer shell of carboxylic-acid group. The magnetite and the surface-coated magnetite particles were well monodispersed. The diameters of the nanoparticles were about 10.4 nm and 12 nm, respectively, determined by using transmission electron microscopy and dynamic light scattering method. The superparamagnetic behaviors were examined by measuring magnetization hysteresis loops and zero-field cooling and field cooling magnetizations as a function of temperature from 5 K to 300 K. The blocking temperatures of the magnetite and the surface coated magnetite were around 245 K and 220 K, respectively. The superparamagnetic behaviors of the magnetite and the surface coated magnetite nanoparticles were discussed in the context of the change of magnetizations with temperature.

생체분자 분리를 위한 Fe3O4나노입자의 표면수식과 분산 안정성 향상

The surface of magnetite (<TEX>$Fe_{3}O_{4}$</TEX>) nanoparticles prepared by coprecipitation method was modified by carboxylic acid group of poly(3-thiophenacetic acid (3TA)) and meso-2,3-dimercaptosuccinic acid (DMSA). Then the lysozyme protein was immobilized on the carboxylic acid group of the modification of the magnetite nanoparticles. The magnetite nanoparticles are spherical and the particle size is approximately 10 nm. We measured quantitative dispersion state by dispersion stability analyzer for each <TEX>$Fe_{3}O_{4}$</TEX> nanoparticles with and without surface modification. The concentration of lysozyme on the modified magnetite nanoparticles was also investigated by a UV-Vis spectrometer and compared to that of magnetite nanoparticles without surface modification. The functionalized magnetite particles had higher enzymatic capacity and dispersion stability than non-functionalized magnetite nanoparticles.

Functionalization of Magnetite Nanoparticles for Protein Immobilization

The surface of magnetite nanoparticles which have been prepared by coprecipitation method was modified by carboxylic acid group of poly(3-thiophenacetic acid (3TA)). Then the egg white lysozyme was immobilized on the carboxylic acid group of the modification of the magnetite nanoparticles. Lysozyme immobilizing efficiency increased with increasing concentration of 3TA. And the functionalized magnetite particles had higher enzymatic capacity than non-functionalized magnetite nanoparticles.

Infrared Monitoring of the Modification of Styrene Acrylonitrile Copolymers with Oxazoline and Its Interfacial Reaction with Acid‐Containing Polymers

AbstractThe kinetics of the modification of styrene acrylonitrile (SAN) with aminoethanol to oxazoline‐containing copolymers has been monitored with FTIR spectroscopy. Further, the interfacial reaction in bilayer samples of the oxazoline groups of these copolymers and the carboxylic acid groups of poly(ethylene‐co‐methacrylic acid) (PE‐co‐MA) copolymers has been studied by FTIR at different temperatures. The interfacial formation of ester‐amides has been measured quantitatively by FTIR difference spectroscopy.

Blends of Poly(mono n-alkyl itaconates) with Tertiary Polyamides: Specific Interactions and Thermal Degradation

The specific interactions in blends of poly(mono-n-alkyl itaconate)s with two tertiary polyamides, the poly(N,N-dimethylacrylamide) (PDMA) and the poly(ethyloxazoline) (PEOX), were studied. Hydrogen bonding between carboxylic acid groups of poly(mono-n-alkyl itaconate)s and carbonyl groups of PDMA and PEOX was found. The interassociation extent was measured by spectral fitting of the Amide I band and reveals a loss of interassociating ability in blends with PDMA as the length of the size group of the poly(mono-n-alkyl itaconate) increases, while in blends with PEOX the interassociation degree remains constant for a given composition. This different behavior is attributed to the larger interspacing between vicinal carbonyl groups in PEOX. Spectral changes upon heating showed an increase of thermal stability of the polyacid in the blends, larger in blends with PDMA than PEOX. These changes are explained in terms of the hydrogen bonding and the rigidity of the system. Finally, the ratio of absortion coefficients for the Amide I band was obtained.

Evidence from infrared ellipsometry for covalent bonding at a polymer/polymer interface with relevance to "lock-up" in pressure-sensitive adhesive laminates

In a novel application, infrared spectroscopic ellipsometry is used to provide clear evidence for the formation of a covalent bond at a polymer/polymer interface. Specifically, there is evidence for the formation of a Si-O-C bond resulting from a reaction between the silyl (SiH) group of a poly(hydrogen methyl siloxane) crosslinker used in poly(dimethyl siloxane) and the carboxylic acid group of poly(acrylic acid). This covalent bond formation could explain the source of the "lock-up" that is sometimes found between acrylic pressure-sensitive adhesives and a silicone-coated release liner.

Miscibility of nylon 6 with poly(maleic anhydride-co-vinyl acetate) and hydroxylated poly(maleic anhydride-co-vinyl acetate) blends

Abstract The miscibility of blends of nylon 6 with poly(maleic anhydride- co -vinyl acetate) (poly(MAH- co -VAc)), or hydroxylated poly(maleic anhydride- co -vinyl acetate) (poly(MAH- co -VAc)H) was investigated by means of Fourier transform infra-red ( FT i.r.) spectroscopy, differential scanning calorimetry (d.s.c.), and X-ray diffraction. Poly(MAH- co -VAc) was prepared by radical copolymerization and the copolymers were hydrolysed to form poly(MAH- co -VAc)H at reflux temperature in H 2 O. Poly(MAH- co -VAc) and poly(MAH- co -VAc)H were characterized by FT i.r. and 1 H-n.m.r. spectroscopy. On the basis of optical clarity, glass transition temperature ( T g ), FT i.r. spectra, and X-ray diffraction, it was found that the nylon 6/poly(MAH- co -VAc) blends showed immiscible behaviour over the entire blend concentration but the poly(MAH- co -VAc)H showed miscibility with nylon 6 over blend concentrations above 75 wt% of poly(MAH- co -VAc)H. The FT i.r. results showed that strong specific interactions between the carboxylic acid group of poly(MAH- co -VAc)H and the amide group of nylon 6 are responsible for the miscibility.

Trifluoroethanol Derivatization of Carboxylic Acidcontaining Polymers for Quantitative XPS Analysis

The carboxylic acid groups of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were derivatized in the solid state using a procedure resulting in esterification by trifluoroethanol vapour. X-ray photoelectron spectroscopy analyses incidate that stoichiometric reaction with PAA was reached after 10 h. However, PMAA did not attain a yield greater than 60%, an effect rationalized in terms of steric hindrance. It is postulated that steric restraints are imppsed by conformational inflexibility related to the pendant methyl group within isotactic portions of the chain.

Trifluoroethanol Derivatization of Carboxylic Acid-containing Polymers for Quantitative XPS Analysis

The carboxylic acid groups of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were derivatized in the solid state using a procedure resulting in esterification by trifluoroethanol vapour. X-ray photoelectron spectroscopy analyses indicate that stoichiometric reaction with PAA was reached after 10 h. However, PMAA did not attain a yield greater than 60%, an effect rationalized in terms of steric hindrance. It is postulated that steric restraints are imposed by conformational inflexibility related to the pendant methyl group within isotactic portions of the chain.

Strategies for Covalent Attachment of Doxorubicin to Poly(PEG-Lys), a New Water-Soluble Poly(ether urethane

Poly(PEG-Lys) is a new, water soluble poly(ether urethane) that has shown promise as an injectable drug carrier. To evaluate the possible use of this drug carrier in chemotherapy, three different approaches for the covalent attachment of doxorubicin to the pendent carboxylic acid groups of poly(PEG- Lys) were developed. In one approach, the pendent carboxylic acid groups of poly(PEG-Lys) were converted to N-hydroxysuccinimide active esters, which spontaneously formed hydrolytically stable amide bonds upon reaction with the amino group located on the daunosamine ring of doxorubicin. The amount of amide-bound doxorubicin was about 7.3 mg/100 mg of conjugate. In a second approach, the degradable hydrazone linkage was formed by reaction of the polymeric hydrazide derivative of poly(PEG-Lys), designated as poly(PEG-Lys hydrazide), with the 13-keto group of doxorubicin. After purification, the amount of carrier-bound doxorubicin was 13.5 mg/100 mg of conjugate. In the third approach, the conjugation of doxorubicin via secondary amine linkages was explored. In this approach, the aldehyde derivative of poly(PEG Lys), desig nated as poly(PEG-Lys-aldehyde), was reacted with doxorubicin, followed by re duction of the intermediate Schiff base with sodium cyanoborohydride. After extensive purification of the carrier, the amount of bound doxorubicin was 10 mg/100 mg of conjugate. All conjugates were characterized by UV/Vis and FTIR spectroscopy and by thin layer chromatography. The conjugates were free of de tectable contamination by unbound drug.

Shifts in the Apparent Ionization Constant of the Carboxylic Acid Groups of Gelatin

Titration data of Type B gelatin were used to investigate shifts of the apparent ionization constant of the carboxylic acid groups caused by changes in the degree of ionization or net molecular charge and in ionic strength. The intrinsic ionization constant was estimated by comparison between titrations in water and in 0.10 molal NaCl. This estimated value of the carboxylic acid groups of gelatin was comparable to those reported for the carboxylic acid groups of poly(acrylic acid) and of a polyampholyte based on methacrylic acid. Neighboring cationic groups of the gelatin molecule assist in the removal of the proton from a carboxylic acid group by electrostatic repulsion while neighboring carboxylate ions hinder the ionization by electrostatic attraction of the proton. These interactions result in a negative or positive electrostatic free energy of ionization, respectively. This excess free energy was calculated by two analogous procedures difference between the apparent and intrinsic ionization constants, and from the slope of a plot of the apparent ionization constant versus net molecular charge. These two methods of calculation gave comparable values for gelatin. Maximum values for the electrostatic free energy of ionization, determined at nearly complete ionization, were of the same order of magnitude for gelatin and for the synthetic polyampholyte. They were an order of magnitude larger for poly(acrylic acid) due to the lack of cationic groups. Addition of 0.10 molal NaCl shifted the apparent ionization constant of the carboxylic acid groups of gelatin toward their intrinsic ionization constant and reduced the absolute value of the electrostatic free energy of ionization compared to its values in water at comparable degrees of ionization.