Formation of calcium carbonate films on chitosan substrates in the presence of polyacrylic acid

In this investigation, chitosan membranes with different surface average degrees of deacetylation (DA) are prepared and then are employed as the support matrix to culture calcium carbonate (CaCO₃). In the presence of high concentration of polyacrylic acid (PAA), the CaCO₃ films obtained on the surface of all chitosan films mainly consisted of vaterite, which suggests the presence of bulk PAA plays an overwhelming part in stabilizing the vaterite. As a comparison, the influences of active groups indicate that only in case of low concentration PAA the thin CaCO₃ films grown on chitosan with 8% DA mainly consisted of vaterite owing to the strong nucleation ability of -NH₂ group, whereas, for those grown on chitosan with 80% DA the CaCO₃ films mainly consisted of aragonite. A more complex scenario revealed that in the case of intermediate concentration of PAA the formed polymorphs behave as mixtures of vaterite and aragonite.     

Designing cancer nanodrugs that are highly loaded,pH-responsive,photothermal, and possess a favored morphology: A hierarchical assembly of DOX and layer-by-layer modified rGO

A facile strategy to construct the multifunctional rGO-DOX nanodrugs by hydrogen bonding was reported. The nanodrugs were highly loaded, pH-responsive, photothermal, and possess a favored morphology.     

Methyl methacrylate-co-itaconic acid (MMA-co-IA) hydrogels for controlled drug delivery

In the present work methyl methacrylate-co-itaconic acid (MMA-co-IA) hydrogels were synthesized by free radical copolymerization of methyl methacrylate (MMA) and itaconic acid (IA) using ethylene glycol dimethacrylate (EGDMA) and methylene bisacrylamide (MBAAm) as crosslinkers and benzoyl peroxide as initiator. Selected samples were loaded with model drug lactulose. For the lactulose release, the effect of pH, monomeric compositions, degree of crosslinking were investigated. The release of lactulose was studied for 8 h period in USP phosphate buffer solutions of varying pH 1.2, 5.5, 6.5 and 7.0. The drug release data were fitted into various kinetics models like the zero order, first order, Higuchi and Peppas. The release kinetics of lactulose from MMA/IA hydrogels was found to be best described by the Peppas model. Results showed that drug release increased by increasing IA content in the hydrogels but the effect of changing of crosslinking ratio on drug release was not significant. The surface morphology of MMA/IA drug loaded hydrogel was studied by SEM which revealed uniform distribution of the drug in the hydrogels. In conclusion, it can be said that lactulose can be successfully incorporated into crosslinked MMA/IA hydrogels and its release can be modulated by changing the mole fraction of the acid component in the gels.     

Designing of pH-responsive ketorolac tromethamine loaded hydrogels of alginic acid: Characterization,in-vitro and in-vivo evaluation

pH-responsive hydrogels based on alginic acid grafted with acrylic acid and ethylene glycol dimethylacrylate in the presence of ammonium persulfate were developed for controlled delivery of Ketorolac tromethamine. The alginic acid based hydrogels were prepared by free radical polymerization technique. Increase in gel fraction was observed with the increase in alginic acid, acrylic acid, and ethylene glycol dimethylacrylate content. The dynamic swelling and drug release studies were conducted at two different pH values (pH 1.2 and 7.4). Maximum swelling and drug release were observed at pH 7.4. The characterization of prepared hydrogels was carried out by using Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, powder x-ray diffraction, and scanning electron microscopy. Similarly, in-vivo study was performed on rabbits and greater plasma drug concentration was achieved by fabricated hydrogels as compared to drug solution and commercial product Keten. Conclusively, the fabricated hydrogels can be considered as a potential candidate for controlled delivery of Ketorolac tromethamine.     

Aggregation of laponite in the presence of magnesium ions and polyacrylic acid

The average mass and size characteristics of ageing laponite/MgCl₂ and laponite/MgCl₂/polyacrylic acid were determined in aqueous dispersions at pH 10 using a Coulter counter and laser diffractometry methods. Comparison between mass and size characteristics showed the two systems to temporarily acquire a structure where particles are more densely packed. The relatively higher packing observed for laponite/polymer was attributed to conformational changes of the polymer adsorbed on neighbouring surfaces. Analysis of the reduced mass and size distribution functions confirmed the self-similarity of the distributions. The reduced mass frequency continuously decreased, while the reduced size frequency showed a linear decrease combined with bell-shaped populations. The volume packing observed for the laponite/polymer was attributed to a typical class of aggregates of large size, which was present at the maximal concentration in the bell-shaped distribution. Received: 19 February 2001 Accepted: 6 April 2001     

Effect of thermal annealing on a bilayer polyvinyl alcohol/polyacrylic acid electrospun hydrogel nanofibres loaded with doxorubicin and clarithromycin for a synergism effect against osteosarcoma cells

Polyvinyl alcohol/polyacrylic acid (PVA/PAA) bilayer hydrogel nanofibres were successfully fabricated by electrospinning and physically crosslinked via heat treatment. The effects of the thermal annealing process on the structure, morphology, swelling, thermal properties and hydrophilicity of electrospun nanofibres were investigated. In addition, these membranes were also used to incorporate doxorubicin and clarithromycin for osteosarcoma treatment, one in each layer. These drugs were used because it is hypothesized in this work that a synergism occurs between both drugs. So, these membranes were analyzed towards their dual-drug release and potential cytotoxicity towards the U2OS human osteosarcoma cell line. Moreover, the water contact angle, disintegration, swelling and weight loss studies confirmed the rapid swelling and improved water stability of the annealed PVA/PAA bilayer nanofibres. The annealed bilayer nanofibres exhibited an increase in the average diameter and degree of crystallinity. In addition, the results revealed that a variation occurred in the degree of hydrophilicity of annealed PVA/PAA bilayer nanofibres. The PAA nanofibres surface exhibited higher hydrophilicity than the PVA nanofibres surface. Drug delivery presented to be as fast rate release for clarithromycin and slow-rate release for doxorubicin, which may be advantageous because both drugs exhibited to be synergetic for certain dosages presenting the combination of the drugs higher than 50% of cell inhibition, while these membranes had higher inhibition values (up to 90%), which was attributed to the PAA but also the drugs. These unique properties are of potential interest in drug delivery applications for dual drug delivery where the tunability of surfaces is desirable.     

Radiation synthesis of superabsorbent poly(acrylic acid)–carrageenan hydrogels

A series of superabsorbent hydrogels were prepared from carrageenan and partially neutralized acrylic acid by gamma irradiation at room temperature. The gel fraction, swelling kinetics and the equilibrium degree of swelling (EDS) of the hydrogels were studied. It was found that the incorporation of even 1% carrageenan (sodium salt) increases the EDS of the hydrogels from 320 to 800 g/g. Thermal analysis were carried out to determine the amount of free water and bound water in the hydrogels. Under optimum conditions, poly(acrylic acid)–carrageenan hydrogels with high gel fraction (80%) and very high EDS (800 g/g) were prepared gamma radiolytically from aqueous solution containing 15% partially neutralized acrylic acid and 1–5% carrageenan. The hydrogels were also found to be sensitive to the pH and the ionic strength of the medium.     

Poly(acrylic acid) with disulfide bond for the elaboration of pH-responsive brush surfaces

We report on a new route for the facile preparation of pH-responsive tethered brushes on metallic surfaces, starting from poly(acrylic acid) (PAA) containing a disulfide (S-S) bond (PAA-S-S-PAA). First, atom transfer radical polymerization (ATRP) of 1-ethoxyethyl acrylate (EEA) with a disulfide-containing initiator was performed to obtain the poly(EEA) precursor polymer (PEEA-S-S-PEEA). Deprotection of PEEA by a heating step resulted in the desired PAA chains without any further purification. The brushes, obtained by the ‘grafting to’ of PAA-S-S-PAA onto gold, were then characterized by atomic force microscopy in water at various pH values. The results evidence a large collapsing/swelling capacity.     

High-performance liquid chromatographic determination of monomeric sodium acrylate and acrylic acid in polyacrylic gelling agents

Summary High-performance liquid chromatographic methods (reversed-phase and ion exclusion) for the determination of monomeric acrylic acid in polyacrylic gelling agents are described. Acrylic acid is extracted by two different methods.The methods were applied to samples containing acrylic acid from 1–1000 mg/kg.     

Polyacrylamide hydrogels with phenylboronic acid moieties for the imprinting of proteins

<正>In this letter,N-acryloyl-3-aminophenylboronic acid(AAPBA) was synthesized and then examined as a new functional monomer for protein imprinting.It was allowed to be copolymerized with acrylamide to produce hemoglobin- or lysozyme-imprinted hydrogels.In template rebinding tests,the imprinted gels showed significant increase in the specific binding with the increase of the AAPBA amounts in the prepolymerization recipes.These results indicate that AAPBA may be a useful functional monomer for its moderate interactions with protein molecules.     

Facile preparation of pH-responsive PEGylated prodrugs for activated intracellular drug delivery

The acid-cleavable amphiphilic prodrug DOX-PEG-DOX self-assemble to form nanoparticles and enter the cell by endocytosis for the pH-triggered intracellular delivery of DOX.     

Facile preparation of pH-responsive PEGylated prodrugs for activated intracellular drug delivery

PEGylated prodrug, covalent attaching polyethylene glycol (PEG) polymer chains to therapeutic drugs, is one of the most promising techniques to improve the water-solubility, stability, and therapeutic effect of drugs. In this study, three PEGylated acid-sensitive prodrugs DOX-PEG-DOX with different molecular weights, were prepared via Schiff-base reaction between aldehyde-modified PEG and the amino groups of doxorubicin (DOX). This kind of amphiphilic polymeric prodrug could be self-assemble into nanoparticles in aqueous solution. The average particle size and morphologies of the prodrug nanoparticles under different pH conditions were observed by dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. It turned out that the nanoparticles could be kept stable in the physiological environment, but degraded in acidic medium. Subsequently, we also investigated in vitro drug release behavior and found that the prodrug had acid-sensitive property. The cytotoxicity and intracellular uptake assays revealed that the prodrugs could rapidly internalized by HeLa or HepG2 cells to release DOX and effectively inhibited the proliferation of the tumor cells, which have the potential for use in cancer therapy.     

白花丹酸的简易合成法

设计了以邻苯二酚为起始原料的新合成路线, 在不同保护基的条件下用二条合成路线合成了白花丹酸, 方法的特点是以杂原子诱导的芳基锂化反应实现了区域专一性芳酰化; 用KH为碱顺利实现了羰基α位的羧甲基化; 采用环己酮保护酚羟基后, 后处理方便, 收率提高。     

Radiation synthesis of polyaspartamide functionalised hydrogels for sustained release of fragrances

The aim of the present investigation is to assess the possibility of obtaining a biocompatible material device which is able to deliver oil-soluble fragrances in air over a length of time. Aqueous solutions of polyaspartamide functionalised with glycidyl methacrylate have been crosslinked through gamma irradiation in the presence of a lipophilic model fragrance, emulsified prior to irradiation. Two emulsification conditions have been considered at two different concentrations of both fragrance and surfactant in water. Chemical hydrogels have been obtained in correspondence to two irradiation absorbed doses and have been characterised for their solubility properties and swelling ability in water. Both static and dynamic release experiments of the fragrance in air have been performed and the release behaviour related to the hydrogel network structure and its water retention properties.     

Determination of trace amounts of cadmium and copper by atomic absorption spectrometry after simultaneous extraction and preconcentration using a new water-soluble polyacrylic acid/alumina sorbent

An analytical method using alumina modified with water-soluble polyacrylic acid polymer for the simultaneous separation and preconcentration of trace Cu and Cd in a column system, and their determination by flame atomic absorption spectrometry was developed. The conditions for coating Al₂O₃ with polyacrylic acid were optimized, then the column was packed with 50 mg of this sorbent. Cd and Cu solution was passed through a glass column at pH 4.5, and elution was carried out with 5 mL of 0.05 M HCl at a flow rate of 1 mL min⁻¹. A sorption capacity of 10 mg Cu and 12 mg Cd was obtained for 1 g sorbent. The detection limit was calculated as 4.5 μg L⁻¹ for Cu and 1.54 μg L⁻¹ for Cd in the final solution. Enrichment factors of 300 for Cd and 400 for Cu were obtained.     

低分子量聚丙烯酸钠的合成

低分子量聚丙烯酸及其钠盐广泛应用于造纸工业 ,随着高浓度涂布机的引进和铜板纸生产的发展 ,对分散剂的要求越来越大 ,因低分子量聚丙烯酸钠具有提高颜料的细度、分散体系的稳定性 ,提高纸张的柔软性、强度、光泽、白度等优点 ,所以低分子量丙烯酸在造纸工业上越来越受到重视。低分子量聚丙烯酸钠可用不同的方法合成[1,2 ] ,但都是在比较高的温度进行 ,并且要蒸馏回收大量的链转移剂 ,操作费时、耗能。本实验在较低温度下以氧化 还原催化剂直接合成了低分子量聚丙烯酸钠 ,经造纸厂实际应用试验证明 ,该分散剂可单独或与无机磷酸盐分散剂复…     

Comparison of complexed species of Eu in alumina-bound and free polyacrylic acid: a spectroscopic study

The speciation of Eu complexed with polyacrylic acid (PAA) and alumina-bound PAA (PAA(ads)) was studied at pH 5 in 0.1 M NaClO(4). Structural parameters were obtained from (7)F(0) -->(5)D(0) excitation spectra measured by laser-induced fluorescence spectroscopy as well as from Eu L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra. The coordination mode was also investigated by infrared spectroscopy. To elucidate the nature of the complexed species, Eu-acetate complexes were used as references. The spectroscopic techniques show that two carboxylate groups with 2-3 (EuPAA) and 4-5 (EuPAA(ads)) water molecules are coordinated to Eu in the first coordination sphere. For EuPAA(ads), the coordination between carboxylate groups and Eu appears to be bidendate. A similar coordination is probable for EuPAA but the EXAFS data indicate a slightly distorted coordination. The results show that the degree of freedom of carboxylate groups is not the same for free or adsorbed PAA. For PAA, the degree of freedom is constrained by the flexibility of the methylene chain. When PAA is adsorbed on alumina, the polymer chains cannot any more be treated as independent chains. One may rather assume formation of aggregates that form an organic layer at the mineral surface presenting a complex arrangement of carboxylate groups.     

Synthesis of pH‐responsive photocrosslinked hyaluronic acid‐based hydrogels for drug delivery

Photocrosslinked hyaluronic acid/poly(vinyl alcohol)‐styrylpyridinium (HA/PVA‐SbQ) hydrogels were synthesized for controlled antitumor drug delivery. The photocrosslinking reaction was rapid, and the time required for completely converting into the insoluble hydrogels was less than 500 s on exposure to 5 mW/cm² UV light irradiation. The resulting hydrogels exhibited sensitivity to the pH value of the surrounding environment. Scanning electron microscopic analysis revealed that the morphology and the pore size of the hydrogels could be controlled by changing the ratio of HA and PVA‐SbQ in the formulations. Paclitaxel (PTX)‐loaded hydrogel could also be formed rapidly by UV irradiation of a mixed solution of HA/PVA‐SbQ and PTX. Release profiles of PTX from the hydrogels showed pH‐dependent and sustained manner. Moreover, our data revealed that PTX released from the HA hydrogels remained biologically active and had the capability to kill cancer cells. In contrast, control groups of HA hydrogels without PTX did not exhibit any cytotoxicity. This study demonstrates the feasibility of using HA‐based hydrogels as a potential carrier for chemotherapeutic drugs for cancer treatments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

The effect of solvent composition on swelling and shrinking properties of poly(acrylamide-co-itaconic acid) hydrogels

The peculiarities of the equilibrium swelling ratio and swelling-shrinking kinetics of polyelectrolyte copolymeric hydrogels consisting of acrylamide and itaconic acid (AAm/IA) have been studied in water/nonsolvent (acetone, methanol, ethanol and 1-butanol) mixtures as a function of solvent composition and IA content in the hydrogel. The phase transition of these hydrogels was generated by changing the solvent composition by progressive substitution of water by the nonsolvent. For all P(AAm/IA) hydrogels, the form of the shrinking curves was determined to be strongly dependent on the type of the nonsolvent used. The rate of shrinking of these hydrogels increased in the order 1-butanol < ethanol < methanol < acetone.     

Preparation and characterization of new hydrogels based on hyaluronic acid and α,β-polyaspartylhydrazide

Hyaluronic acid (HA) has been crosslinked with α,β-polyaspartylhydrazide (PAHy). The crosslinking reaction has been performed in acidic medium in the presence of various amounts of N-ethyl-N′-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC). All obtained samples have been characterized by FT-IR analysis and swelling measurements in double distilled water that have confirmed the occurrence of a chemical linkage between two polymers and the affinity towards aqueous medium of HA-PAHy networks, respectively.In vitro degradation assays have been performed in simulated physiological conditions as well as in the presence of hyaluronidase. Experimental data evidenced that HA-PAHy samples undergo a poor chemical and a reduced enzymatic degradation unlike native HA.