Showing papers in "Macromolecular Bioscience in 2003"

Chitosan: An Attractive Biocompatible Polymer for Microencapsulation

Abstract: Chitosan is a weak cationic polysaccharide composed essentially of β(1 → 4) linked glucosamine units together with some N-acetylglucosamine units. It is obtained by extensive deacetylation of chitin, a polysaccharide common in nature. Chitosan is a biocompatible, biodegradable, and nontoxic natural polymer that exhibits excellent film-forming ability. As a result of its cationic character, chitosan is able to react with polyanions giving rise to polyelectrolyte complexes. Therefore, because of these interesting properties, it has become the subject of numerous scientific reports and patents on the preparation of microspheres and microcapsules. The techniques employed to microencapsulate with chitosan include, among others, ionotropic gelation, spray drying, emulsion phase separation, simple and complex coacervation, and polymerization of a vinyl monomer in the presence of chitosan. The aim of this work is to review some of the more common techniques used and to put forward the results obtained by our research group in preparing chitosan-based microcapsules: for taste masking and improving the stability of a nutritional oil, the sustained release of drugs, as well as the preparation of chitosan superparamagnetic microcapsules for the immobilization of enzymes. Scanning electron micrograph of some superparamagnetic chitosan particles and magnetic hysteresis loop of the microparticles.

Present and Future Role of Chitin and Chitosan in Food

Abstract: The conversion of processed discarded material into valuable by-products and alternative specialty materials has been identified as a timely challenge for food research and development associated with numerous applications of chitinous products. Chitin, chitosan, calcareous chitin, and chitosan, N-acetylated chitosan, N-methylene phosphonic chitosan (NMPC), and N-lauryl-N-methylene phosphonic chitosan (LMPC) are being studied as a result of their broad range of food applications. These biopolymers offer a wide range of unique applications including formation of biodegradable films, immobilization of enzymes, preservation of foods from microbial deterioration, as additives (clarification and deacidification of fruits and beverages, emulsifier agents, thickening and stabilizing agents, color stabilization), and dietary supplements. This review summarizes some of the most important developments in this field.

Effect of Chitosan and Temperature on Spore Germination of Aspergillus niger

Abstract: Inhibition of radial growth and spore germination of Aspergillus niger in media with added chitosan were detected. The highest radial growth inhibition (73%) was determined at 24 h with 3 g . L -1 of chitosan, and the percent inhibition of spore germination was 40% after 13 h of inoculation. Further, the CC 50 , that is, the concentration at which spore germination is inhibited by 50%, was estimated by probit analysis (3.5 g.L -1 ). The activation energies, E A were estimated by an Arrhenius model in control and amended chitosan media, obtaining 35.6 and 36.6 kcal.mol -1 , respectively. These values were in the same order of magnitude because chitosan as inhibitor was more effective at low temperature (≤ 18 °C). Hence synergism of temperature and chitosan were only observed at 12 and 18°C. Therefore, the maximal percentage of germinated spores, S max was also affected by low temperatures in chitosan-amended media with estimated values lower than 70% at temperatures < 37 °C whereas in control media S max reached values close to 100%. Scanning electron micrographs showed that chitosan produced spore aggregation and morphological anomalies affecting swelling, germ tube emergence, and polarization.

Chemical Modification of Chitosan, 17

Abstract: The Michael reaction of chitosan with acrylic acid was carried out successfully even in water alone as the reaction medium. As a consequence of its good solubility in water, the reaction product, N-carboxyethylchitosan showed excellent biodegradable properties with standard activated sludge.

Laccase-catalyzed Synthesis and Antioxidant Property of Poly(catechin)

Abstract: Catechin was oxidatively polymerized by laccase in a mixture of a polar organic solvent and buffer to give a new class of flavonoid polymers. Myceliophthora laccase showed high catalytic activity for the polymerization. Using a mixed solvent of acetone and pH 5 acetate buffer efficiently produced the polymer. Under the selected conditions, DMF-soluble polymers were obtained in good yields. Effects of reaction parameters on the yield, solubility, and molecular weight of the polymer have been systematically investigated. A radical species was detected in the polymer by ESR spectroscopy. The polymers showed greatly amplified superoxide scavenging activity and xanthine oxidase inhibitory activity compared with monomeric catechin. Superoxide scavenging activity of poly(catechin)s, n = 3. ○: catechin, □: poly(catechin).

Synthesis and Characterization of β-Cyclodextrin Based Functional Monomers and its Copolymers with N-isopropylacrylamide

Abstract: Two novel monovinyl β-cyclodextrin (β-CD) monomers are synthesized Their chemical compositions are characterized by means of element analysis, NMR and FT-IR spectroscopy The results show that the synthesis techniques used are convenient and efficient Using N-isopropylacrylamide as a comonomer, two novel linear copolymers can also be synthesized

Biologically Active Polymers, 6

Abstract: Various copolymers were prepared by the copolymerization of 2-chloroethyl vinyl ether (CEVE) with methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA) and vinylbenzyl chloride (VBC). The copolymers were further modified by quaternization with triethylamine, triphenylphosphine, and tributylphosphine. The antimicrobial activities of the prepared, quaternized copolymers were evaluated against Candida albicans, Fusaruimoxysporium, Aspergillus flavus, Bacillussubtilis, Escherichiacoli,and Staphylococcus aureus. The antimicrobial activity was explored by the cut plug method, viable cell counting (surviving ratio), transmission electron microscopy, and potassium leakage tests. The results indicated that the prepared polymers had a high antimicrobial activity, control experiments on the main polymer withoutammonium, phenyl, or butyl and/or phosphonium groups were carried out. The phosphonium containing polycationicbiocidesare more effective than the quaternary ammonium salt polymers. Examining the C. albicans and S. aureus polymer-treated cells by electron microscopy indicated disruption for the cytoplasmic membrane and release of potassium ion as shown by the assay of potassium leakage.

Antigen Responsive Hydrogels Based on Polymerizable Antibody Fab′ Fragment

Abstract: Novel antigen responsive hydrogels were prepared by using polymerizable antibody Fab′ fragment from monoclonal anti-fluorescein BDC1 antibody (IgG2a). To form Fab′ containing hydrogels, the polymerizable Fab′ fragment was copolymerized with N-isopropylacrylamide (NIPAAm) and N,N′-methylenebis(acrylamide) (MBAAm; crosslinker) using redox initiators. The thermosensitivity of the hydrogels decreased with increasing Fab′ fragment content. The antigen responsiveness of the hydrogels depended on the Fab′ content, pH, and temperature. When the hydrogels were alternately exposed to antigens fluorescein (FL) and polyamidoamine dendrimer (PAMAM)-fluorescein (FD), significant reversible volume changes were observed for the hydrogel containing 50% (w/w) Fab′ fragment at 33.7 and 36.8 °C in acetate buffer (10 mM, pH 5.0), respectively, but not at 27.7 °C or in PBS buffer (10 mM, pH 7.4). No noticeable reversible volume changes were observed with pure PNIPAAm hydrogel and the gel containing 10% (w/w) Fab′ fragment. Structure of Fab′ containing hydrogels.

Laccase‐Catalyzed Oxidative Polymerization of Phenols

Abstract: Laccase-catalyzed oxidative polymerization of phenol and its derivatives has been performed in aqueous organic solvents at room temperature in air. Laccase derived from Pyconoporus coccineus efficiently induced the polymerization to produce polyphenols consisting of a mixture of phenylene and oxyphenylene units. The unit ratio of the polymer could be precisely controlled by selection of the solvent and the monomer substituent.

Preparation of Crosslinked Chitosan/Silk Fibroin Blend Films for Drug Delivery System

Abstract: Crosslinked chitosan/silk fibrosin blend films were prepared by a solution casting technique using glutaraldehyde as crosslinking agent. Drug release characteristics of the blend films with various blend compositions were investigated. Theophylline, diclofenac sodium, amoxicillin trihydrate, and salicylic acid were used as model drugs. The release studies were performed at 37 °C in buffer solutions at pH 2.0, 5.5, and 7.2. It was found that the blend films with 80% chitosan content showed the maximum amount of model drug release at pH 2.0 for all the drugs studied here. This result corresponded to the swelling ability of the blend films. From a swelling study, the maximum degrees of swelling of the drug-loaded blend films were obtained at this pH and blend composition. The amount of drugs released from the films with 80% chitosan content, from the highest to the lowest values, occurred in the following sequence: salicylic acid > theophylline > diclofenac sodium > amoxicillin.

Methylation of chitosan with iodomethane: Effect of reaction conditions on chemoselectivity and degree of substitution

Abstract: N,N,N-trimethylchitosan (TMC) was prepared by reacting purified chitosan with iodomethane, in the presence of sodium hydroxide, water and sodium iodide, at room temperature. The reaction medium was N-methyl-2-pyrrolidone. Different samples of TMC were obtained by adding to the reaction medium a fixed volume (5.5 mL) of aqueous NaOH solutions at different concentrations (15, 20, 30 and 40 wt.-%) and carrying out the reactions for 9 or 24 h. The features observed in the 1 H and 13 C NMR spectra of these chitosan derivatives, in respect of the chemical shift, number and relative intensity of the signals, depended strongly on the excess of NaOH and H 3 CI added to the reaction medium, but when the lowest excess was employed, the characteristics of the derivative were not affected by the reaction time to the same extent. The average degree of quaternization of these N-methylated derivatives of chitosan ranged from 10.5% to 44.8%, according to the reaction conditions. Increasing the excess of NaOH, in reactions carried out for 9 h, resulted in TMC samples with progressively higher content of trimethylated sites however, the reaction yields were correspondingly lower and O-alkylation was favored in these cases.

Recovery of Metal Ions by Chitosan: Sorption Mechanisms and Influence of Metal Speciation

Abstract: Chitosan is characterized by a high affinity for metal ions due to its high content of amine groups. The sorption mechanism depends on both the protonation of these amine groups and the speciation of metal ions. Metal cations may be adsorbed at pH close to neutrality by chelation mechanism while metal anions can be adsorbed in acidic solutions through ionic interactions with protonated amine groups. Several examples are considered. The first example focuses on Cd sorption, which proceeds by a chelation mechanism on free non-protonated amine groups in neutral media. In acidic solutions the protonation of amine groups limits the ability of amine groups to complex Cd. The crosslinking of chitosan with glutaraldehyde also results in a dramatic decrease of sorption properties due to the decrease in the density of complexation sites available for sorption. The sorption of vanadium(V) and molybdenum(VI) illustrates the high capacity of chitosan for the sorption of oxo-anions. They are very efficiently sorbed in acidic solutions by ionic interactions. The correlation of sorption capacities with the distribution of metal species shows that the sorbent has a greater affinity for highly charged anionic species. The sorption of complex anionic species such as chloro-complexes of Pd and Pt; and that of copper complexed with organic ligands have also been studied. The optimum conditions for sorption are obtained when anionic complexes predominate in the solution. The chemical modification of chitosan, obtained by grafting of sulfur compounds, allows modifying the sorption mechanism: the ion-exchange polymer is transformed to a dual ion-exchange and chelating polymer.

Influence of Complexing Polyanions on the Thermostability of Basic Proteins

Abstract: Lysozyme (Lyz), chymotrypsinogen (Cht), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were used as model proteins capable of forming water-soluble polyelectrolyte complexes with linear synthetic polyanions. The complex formation with sodium poly(methacrylate) (PMA), sodium poly(acrylate) (PAA), sodium poly(anetholsulfonate) (PAS), and potassium poly(vinylsulfate) (PVS) markedly reduced the temperature of protein denaturation, Tmax, as determined by differential scanning calorimetry (DSC). The effect of sodium poly(styrenesulfonate) (PSS) on Lyz was so drastic that the protein melting peak was not observed at all during DSC measurements. The temperature shift, most pronounced for Lyz, increased upon substitution of the polyanions according to the following series: PMA < PVS < PAA < PAS < PSS. Decomposition of the complexes by addition of either sodium chloride or poly(N-ethyl-4-vinylpyridinium) cation completely restored the initial Tmax of the protein (except for PSS and PAS). The complex formation slightly affected the enzyme activity up to temperatures close to Tmax of the polyanion-protein complex. On further heating, the activity of the complex decreased steeply, whereas the free enzyme maintained a high activity. The data obtained strongly suggest that the protein-polyelectrolyte interactions in solution, while leaving the thermostability and activity of the proteins practically unaffected over a rather wide temperature range, result in the effective denaturation of proteins once a certain critical temperature is achieved. This finding appears to be crucial for further development of immobilized enzymes in biotechnology and essential for understanding mechanisms and principles of the functioning of proteins immobilized on charged matrices in vivo. (Less)

Reaction Mechanism of Enzymatic Degradation of Poly(butylene succinate‐co‐terephthalate) (PBST) with a Lipase Originated from Pseudomonas cepacia

Abstract: An aliphatic/aromatic copolyester, poly(butylene succinate-co-terephthalate) (PBST), was prepared to investigate the effect of the aromatic units on the enzymatic degradation of the poly(butylene succinate) (PBS) derivatives in the presence of a lipase originated from Pseudomonas cepacia (Lipase PS®). The degradability of PBST was found to increase with increasing BS content. The degradation products were analyzed in detail by liquid chromatograph mass spectrometry (LC-MS). A hexamer containing one terephthalate unit was the largest fragment among the diverse fragments detected, while a pentamer was the largest one consisting only of succinate units. The oligomeric fragments cut out from the polymer chain were involved in the secondary hydrolysis into 4-hydroxybutyl succinate (BSH) and terephthalate (BTH). The trimeric fragments tetramethyl disuccinate (SBSH) and succinate terephthalate (SBTH), having both carboxyl end groups, were slowly hydrolyzed by a nonspecific mechanism. Based on these data, the overall mechanism of the enzymatic hydrolysis of this aliphatic/aromatic copolyester is proposed, in which PBST undergoes endo hydrolysis. A plausible mechanism of enzymatic hydrolysis of PBST with Lipase PS®.

A Novel Gelatin–Carbon Nanotubes Hybrid Hydrogel

Abstract: This letter focuses on the first result of the preparation and the swelling behavior of a novel hybrid gelatin hydrogel with carbon nanotubes. A novel hybrid gelatin hydrogel with carbon nanotubes was synthesized by a physical mixing method. The structure of the novel hydrogel obtained was characterized by SEM. Besides, the swelling behavior of the synthesized hydrogel was measured at two different temperatures. The results indicate that carbon nanotubes added could maintain the stability of the hybrid hydrogel without cross-linking at 37 °C. This suggests that the hybrid gelatin hydrogel with carbon nanotubes could be used in biomedical field. Besides, its application in protein separation is discussed.

Bioresorbable Hydrogels Prepared Through Stereocomplexation between Poly(L‐lactide) and Poly(D‐lactide) Blocks Attached to Poly(ethylene glycol)

Abstract: Block copolymers were synthesized by ring-opening polymerization of L-lactide or D-lactide in the presence of mono- or dihydroxyl poly(ethylene glycol), using zinc metal as catalyst. The resulting copolymers were characterized by various techniques, namely 1 H NMR spectroscopy, differential scanning calorimetry (DSC), X-ray diffractometry, and Raman spectrometry. The composition of the copolymers was designed such that they were water soluble. Bioresorbable hydrogels were prepared from aqueous solutions containing both poly(L-lactide)/poly(ethylene glycol) and poly(D-lactide)/poly(ethylene glycol) block copolymers. Rheological studies confirmed the formation of hydrogels resulting from stereocomplexation between poly(L-lactide) and poly(D-lactide) blocks.

Natural Bioactive Material: A Preparation of Soluble Eggshell Membrane Protein

Abstract: The proteins of eggshell membranes, an industrial waste product, are dissolved by reductive cleavage with aqueous 3-mercaptopropionic acid and acetic acid. The soluble protein preparation is cast into a thin film, and its bioactivity is investigated by cell culture. Photomicrograph of NIH3T3 fibroblasts cultured on SEP film for 3 days.

Synthesis and characterization of amphiphilic biodegradable copolymer, poly(aspartic acid-co-lactic acid)

Abstract: An amphiphilic biodegradable polymer, poly-(aspartic acid-co-lactic acid) (PAL), was synthesized by simply heating a mixture of aspartic acid (Asp) and L-lactide without additional catalysts or solvents. The unique branched architecture comprising succinimide units and lactic acid units was confirmed by IR and NMR spectroscopy. A copolymer of sodium aspartate and lactic acid (PALNa) was prepared by reacting PAL with an aqueous sodium hydroxide solution. The PAL was soluble in many organic solvents, while the PALNa was soluble in methanol and water. The hydrolytic degradation behavior of PAL varied with the copolymer composition. A higher Asp content resulted in a faster molecular weight decrease, and introducing glycolic acid units accelerated the degradation rate.

Effect of Chemical Crosslinking on the Swelling and Shrinking Properties of Thermal and pH‐Responsive Chitosan Hydrogels

Abstract: The ability to form a gel through the physical or chemical crosslinking of chitosan has been well documented. In an attempt to mimic biological systems, thermal and pH-sensitive chitosan cylindrical hydrogels were produced by a combination of physical and chemical crosslinking processes. To this end, chitosan hydrogels prepared from alkali chitin were molded in cylinders and, once washed, were further crosslinked with glutaraldehyde at stoichiometric ratios, R (=[-CH=O]/[-NH 2 ]), of 1.61 and 3.22 × 10 -2 . Variation in swelling as a result of stepwise changes in temperature between 40 and 2 °C at pH values of 7.0, 7.6, and 8.0 revealed that the system responds in markedly different manners dependent upon the pH. At pH 7.0, cooling from 40 to 2 °C results in contraction of the gel network structure. While raising the temperature from 2 to 40 °C leads to a rapid swelling response (i.e., ca. a twofold increase in the amount of solvent uptake). Subsequent cooling to 2 °C is accompanied by a new contraction cycle. At pH ≥7.6 the temperature dependence of the swelling-contraction behavior is exactly the opposite of that observed at pH 7.0. Very similar trends were observed for the gels at both degrees of crosslinking. The swelling-shrinking behavior observed in gels of pH≥7.6, is similar in kind to that of uncrosslinked gels and is interpreted in terms of a lower critical solution temperature (LCST) volume phase transition, driven by hydrophobic association, presumably involving residual acetyl groups in the chitin. The results at pH 7.0 suggest that the slight ionization of the -NH + 3 groups leads to destruction of the hydrophobic hydratin thus effectively reversing the negative thermal shrinking.

Effects of chitin/chitosan and their oligomers/monomers on migrations of macrophages

Abstract: The effects of chitin/chitosan and their oligomers/monomers on the migrations of mouse peritoneal macrophage (PEM) and the rat macrophage cell line (rMp) were evaluated in vitro. In direct migratory assay using the blind well chamber method, the migratory activity of PEM was enhanced significantly by chitin and chitosan oligomers (NACOS and COS, respectively), but reduced by chitin, chitosan, and the chitosan monomer (GlcN). The migratory activity of rMp was increased significantly by chitin, chitosan, and the polymers, NACOS and GlcN.

Chiral Recognition Sites Converted from Tetrapeptide Derivatives Adopting Racemates as Print Molecules

Abstract: Molecularly imprinted polymeric membranes were prepared from polystyrene resin bearing tetrapeptide derivatives H-Asp(OcHex)-Leu-Asp(OcHex)-Glu(OBzl)-OCH 2 - (DLDE) consisting of D-amino acid residues or L-amino acid residues. The tetrapeptide derivatives were converted into chiral recognition sites by using not only an optically pure Boc-Trp but also racemic Boc-Trps as a print molecule. The chiral recognition ability depends on the combination of the absolute configuration of the print molecule and that of constituting amino acid residues. The membrane prepared from a DLDE derivative consisting of D-amino acid residues and imprinted by Boc-D-Trp recognized the D-isomer in preference to the corresponding L-isomer and vice versa. In the present study, it was also made clear that racemic print molecules were effective in generating chiral recognition sites. The affinity constant of the generated chiral recognition site was determined to be 9.6 × 10 3 mol -1 . dm 3 , which was independent of the molecular imprinting conditions. Enantioselective permeation was attained by applying electrodialysis. An optimum perm-selectivity of 5.9, which corresponds to the adsorption selectivity, was attained.

A Layer-by-Layer Film of Chitosan in a Taste Sensor Application

Abstract: Chitosan is alternated with sulfonated polystyrene (PSS) to build layer-by-layer (LBL) films that are used as sensing units in an electronic tongue. Using impedance spectroscopy as the principle method of detection, an array using chitosan/PSS LBL film and a bare gold electrode as the sensing units was capable of distinguishing the basic tastes - salty, sweet, bitter, and sour - to a concentration below the human threshold. The suitability of chitosan as a sensing material was confirmed by using this sensor to distinguish red wines according to their vintage, vineyard, and brands.

Synthesis and Characterization of Photocrosslinkable Biodegradable Polymers Derived from 4-Hydroxycinnamic Acid

Abstract: A novel series of photocrosslinkable biodegradable polymers was prepared by a high-temperature solution polycondensation from a dichloride of 4,4'-(adipoyldioxy)dicinnamic acid (CAC) and alkane diols of various methylene lengths (HO(CH 2 ) n OH; n = 6-10) or poly(ethylene glycol)s (PEG) of various molecular weights (M = 200-8 300). The CAC was synthesized by the condensation of adipoyl chloride and 4-hydroxycinnamic acid. The chemical structures and properties of these polymers were characterized by elemental analysis, ultraviolet-visible spectroscopy (UV-VIS), Fourier transform infrared spectroscopy (FT-IR), 1 H NMR spectroscopy, differential scanning calorimertry (DSC), and thermogravimetry (TG). All polymers had a high molecular weight and good solubility in organic solvents. DSC showed that T m values of CACn (134-180°C) were much higher than those of CACEm (25-56°C). The CACE200 degraded very rapidly in the buffer solutions (pH 7.2) of Ps. Cepacia or Rh. delemar lipase at 37°C, while CACn resisted the hydrolysis by these lipases during the test period. The ultraviolet light irradiation (%≥ 280 nm) caused the photocrosslinking reaction by an intermolecular dimerization at ambient temperature without a photosensitizer, as examined by UV-VIS, FT-IR spectroscopy, and gel formation. The gets pregared from CACEm (m 1000) were swollen in water and showed characteristic properties of a hydrogel. The irradiation time and the molecular weight of PEGs controlled the degree of swelling of these hydrogels. The CACE8 300 gel irradiated for 20 min showed the largest degree of swelling of 10.5.

Drug Delivery Systems Based on Porous Chitosan/Polyacrylic acid Microspheres

Abstract: Porous microspheres have been prepared by suspension free radical polymerization of acrylic acid (AA) in the presence of chitosan (CHI). The microspheres were characterized by FTIR and environmental SEM. The PAA content of the microspheres was estimated to be in the range 45-50 wt.-%. The swelling degree of these particles is almost constant in the range 2 < pH < 5, but it increases considerably as the pH is raised from 5 to 10. The release profiles of microspheres loaded with meclofenamic acid (MF) were determined at pH 2, 7.4, and 10. The in vitro release of MF at different pHs was modulated by the solubility of the drug. These microcapsules are biodegradable and presented good biocompatibility and biodegradability during in vivo experiments.

Studies on the Synthesis and Properties of Temperature Responsive and Biodegradable Hydrogels

Abstract: Novel linear poly(NIPA-co-CL) copolymers have been synthesized by radical copolymerization of N-isopropylacrylamide (NIPA) and 2-methylene-1,3-dioxepane (MDO), The structure of copolymers was confirmed by 1 H NMR and IR spectroscopy. Cross-linked poly(NIPA-co-CL) hydrogels have also been prepared in toluene using N,N'-methylenebisacrylamide as cross-linking agent. The hydrogels thus obtained exhibit good temperature response and are biodegradable in the presence of proteinase K.

Hydrogen-Bonding Interaction and Crystalline Morphology in the Binary Blends of Poly(ε-caprolactone) and Polyphenol Catechin

Abstract: The specific intermolecular hydrogen-bonding interaction between the ester carbonyl groups of poly(e-caprolactone) (PCL) and the phenolic hydroxyl groups of catechin has been studied by Fourier-trasform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). According to quantitative curve-fitting analysis of the FT-IR spectra of PCL/catechin blends, it was found that the fraction of hydrogen-bonded carbonyl goups of PCL increased with catechin content, while that of hydrogen-bonded hydroxyl groups of catechin decreased. The calculated crystallinity of PCL in the binary blends, based on the curve-fitting results, suggested that the crystallization of PCL was restrained in the blends with catechin. Only single glass transition temperature, T g , was observed over the whole range of blend compositions, which was between those of the pure components. The melting point, T m , depressed and T g increased, indicating also the existence of strong intermolecular association. The blend composition dependence of T g could be predicted very well by the Kwei equation with a positive 'q' value of 124. With the aid of small angle X-ray scattering measurement, the segregation of catechin was investigated. It was found that the extent of extra-lamellar segregation increased with catechin content. It was suggested that the crystal growth rate played the dominant role in the formation of morphology. With decreasing crystal growth rate of PCL component in the blends, enough time has been given to catechin molecules to diffuse into extra-lamellar region.

Novel biodegradable and thermosensitive Dex-AI/PNIPAAm hydrogel

Abstract: The dextran-allyl isocyanate/poly(N-iso-propylacrylamide) (Dex-AI/PNIPAAm) hydrogel was designed and prepared by copolymerization of the modified dextran with N-isopropylacrylamide(NIPAAm). Thisnovel Dex-AI/PNIPAAm hydrogel is biodegradable and intelligent due to its biodegradable dextran linkage and thermosensitive PNIPAAm moiety. With an increase in dextran content, it exhibits the increased lower critical solution temperature (LCST) and decreased porous microstructure. Also, the thermosensitivity of this hydrogel is also controllable and adjustable depending on the different compositions.

Bilirubin Removal from Human Plasma with Albumin Immobilised Magnetic Poly(2‐hydroxyethyl methacrylate) Beads

Abstract: Bioaffinity separation has a unique and powerful role as a support tool in the removal of toxic substances from human plasma Magnetic beads have advantages as supports in comparison to conventional nonmagnetic beads because of low pressure drop, high mass transfer rates, and good Fluid-solid contact In addition, they eliminate internal diffusion limitations Human serum albumin (HSA) immobilised onto magnetic poly(2-hydroxyethyl methacrylate) (mPHEMA) beads were investigated as an adsorbent for the selective bilirubin removal from human plasma The mPHEMA beads were prepared by a modified suspension polymerisation HSA was covalently coupled to the mPHEMA beads Bilirubin adsorption was investigated from hyperbilirubinemic human plasma on the mPHEMA beads containing different amounts of immobilised HSA, (between 11-100 mg/g) The nonspecific bilirubin adsorption on the unmodified mPHEMA beads was 047 mg/g Higher bilirubin adsorption capacities, up to 647 mg/g, were obtained with the HSA-inonoobilised magnetic beads Bilirubin adsorption increased with increasing temperature