Modified carrageenan. 5. Preparation,swelling behavior,salt‐ and pH‐sensitivity of partially hydrolyzed crosslinked carrageenan‐graft‐polymethacrylamide superabsorbent hydrogel

The polysaccharide, kappa‐carrageenan (κC) was chemically modified to achieve a novel superabsorbent hydrogel via graft copolymerization of methacrylamide (MAM) onto the substrate followed by alkaline hydrolysis. Ammonium persulfate (APS) and N,N′‐methylene bisacrylamide (MBA) were used as a free‐radical initiator and a crosslinker, respectively. The saponification reaction was carried out using sodium hydroxide aqueous solution. Either κC‐g‐PMAM or hydrolyzed κC‐g‐PMAM (PMAM: polymethacrylamide) was characterized by FT‐IR spectroscopy. The effect of grafting variables (i.e. concentration of MBA, MAM, and APS) and alkaline hydrolysis conditions (i.e. NaOH concentration, hydrolysis time and temperature) were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The swelling capacity of these hydrogels was also measured in various salt solutions. Results indicated that the swelling ratios decreased with an increase in the ionic strength of the salt solutions. This behavior can be attributed to charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. Absorbency of superabsorbing hydrogels was examined in buffer solutions with pH range 1–13. Also, the pH reversibility and on–off switching behavior, at pH values 3.0 and 8.0, makes the synthesized hydrogels good candidates for controlled delivery of bioactive agents. Finally, swelling kinetics in distilled water and various salt solutions was preliminary investigated. Results showed that the swelling in water was faster than in saline solutions. Copyright © 2004 John Wiley & Sons, Ltd.     

A green approach to prepare Ag NPs loaded IC/PVA polymeric film for antimicrobial applications

In this study, glyoxal-cross-linked Iota carrageenan (IC) /poly(vinyl alcohol) PVA films were prepared and loaded with silver nanoparticles via a green approach, consisting of sweet lime juice induced in-situ reduction of Ag(I) ions to nano silver within the film matrix. The formation of silver nanoparticles was confirmed using UV–visible spectrophotometry. The Ag NPs-loaded films were also characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). The dynamic water uptake data were interpreted by the ‘Power functional model’. The films showed fair antimicrobial action against bacteria E. Coli.     

Synthesis and characterization of κ‐carrageenan/poly(N,N‐diethylacrylamide) semi‐interpenetrating polymer network hydrogels with rapid response to temperature

In this study, a novel classical thermo‐ and salt‐sensitive semi‐interpenetrating polymer network (semi‐IPN) hydrogel composed of poly(N,N‐diethylacrylamide) (PDEAm) and κ‐carrageenan (KC) was synthesized by free radical polymerization. The structure of the hydrogels was studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). FTIR and SEM revealed that the semi‐IPN hydrogels possessed the structure of H‐bonds and larger number of pores in the network. Compared to the PDEAm hydrogel, the prepared semi‐IPN hydrogels exhibited a much faster response rate to temperature changes and had larger equilibrium swelling ratios at temperatures below the lower critical solution temperature (LCST). The salt‐sensitive behavior of the semi‐IPN hydrogels was dependent on the content of KC. In addition, during the reswelling process, semi‐IPN hydrogels showed a non‐sigmoidal swelling pattern. Copyright © 2008 John Wiley & Sons, Ltd.     

Temperature Effect on Drying and Swelling of Kappa Carrageenan Gels: A Steady State Fluorescence Study

Summary: A novel technique based on in situ steady state fluorescence (SSF) measurements is introduced for studying drying and swelling of κ- carrageenan (kappa carrageenan) gels at various temperatures. κ- carrageenan gels were completely dried and then swelled in water vapor. Pyranine was embedded in κ- carrageenan and used as a fluorescence probe. Scattered light intensities, I_sc and fluorescence intensities, I were monitored during the drying and swelling of κ- carrageenan gels. It was observed that the fluorescence intensity decreased linearly as drying time was increased. A simple model consisting of Case II diffusion was used to quantify the drying processes of the κ- carrageenan gels. This moving boundary model provided packing constant, k₀. During swelling, fluorescence intensity increased exponentially as time is increased. The increase in I, was modeled using Li-Tanaka equation from which swelling time constants, τ_c and cooperative diffusion coefficients, D_c were determined. It was observed that swelling time constants, τ_c decreased and diffusion coefficients, D_c increased as the swelling temperature was increased. Activation energies for drying and swelling were also obtained and found to be 53.9 and 47.2 kJ mol⁻¹, respectively.     

Biocompatible Crosslinked Nanofibers of Poly(Vinyl Alcohol)/Carboxymethyl‐Kappa‐Carrageenan Produced by a Green Process

This study presents a new type of biocompatible nanofiber based on poly(vinyl alcohol) (PVA) and carboxymethyl‐kappa‐carrageenan (CMKC) blends, produced with no generation of hazardous waste. The nanofibers are produced by electrospinning using PVA:CMKC blends with ratios of 1:0, 1:0.25, 1:0.4, 1:0.5, and 1:0.75 (w/w PVA:CMKC) in aqueous solution, followed by thermal crosslinking. The diameter of the fibers is in the nanometer scale and below 300 nm. Fourier transform infrared spectroscopy shows the presence of the carboxyl and sulfate groups in all the fibers with CMKC. The nanofibers from water‐soluble polymers are stabilized by thermal crosslinking. The incorporation of CMKC improves cytocompatibility, biodegradability, cell growth, and cell adhesion, compared to PVA nanofibers. Furthermore, the incorporation of CMKC modulates phenotype of human adipose‐derived stem cells (ADSCs). PVA/CMKC nanofibers enhance ADSC response to osteogenic differentiation signals and are therefore good candidates for application in tissue engineering to support stem cells.     

Kappa-Carrageenan/PVA Filmswith Antibacterial Properties: Part 1. Optimization of Preparation Conditions and Preliminary Drug Release Studies

In this work, kappa carrageenan (KC) and poly(vinyl alcohol) are crosslinked with glutaraldehyde (GTA) to produce films without using catalyst HCL. The optimum conditions for the formation of film have been established based on their water absorption property. The crosslinking reaction was confirmed by FTIR analysis.The films were also characterized by scanning electron microscopy(SEM) and X-ray diffraction (XRD) analysis.The equilibrium swelling of films showed fair dependency on the presence of salt in the swelling medium.However, pH dependent swelling behavior was not prominent. Finally, a representative film sample was loaded with antibacterial drug Gentamicin sulphate and release was monitored kinetically in the physiological fluid (PF) at 37°C. The film showed fair antibacterial action against model bacteria E.Coli.     

氯化钠相转变 K-型卡拉胶/聚 N-异丙基丙烯酰胺共混凝胶的辐射合成及性质研究

用γ辐射技术合成了K 型卡拉胶 (KC)与聚N 异丙基丙烯酰胺共混凝胶 (Blendgels) .合成产物透明 ,有弹性和较好的力学强度 .对不同条件下共混凝胶性能的测定结果表明 ,所形成的共混凝胶有明显的氯化钠相转变性质 ,也保持了聚N 异丙基丙烯酰胺 (PNIPAM)特有的温度敏感性 (LCST为 34℃ )     

Investigation of Moisture Sorption,Permeability, Cytotoxicity and Drug Release Behavior of Carrageenan/Poly Vinyl Alcohol Films

This work describes moisture sorption behavior and water vapor permeability of glutaraldehyde-crosslinked carrageenan/polyvinyl alcohol (Carr/PVA) films. The moisture uptake has been studied under various relative humidity (RH) and the data obtained has been interpreted in the terms of various isotherm models such as GAB, Oswin and Halsey models. The moisture permeability through the films has been characterized in the terms of various parameters like water vapor transmission rate (WVTR), permeance (P) and water vapor permeability (WVP). It was found that these parameters are greatly affected by the degree of crosslinking of the films. Finally, the model drug Gentamycin Sulphate was loaded in to the films and its release was monitored kinetically in the physiological buffer (PF) at 37°C. The films exhibited diffusion controlled release mechanism. The films are non-cytotoxic.     

Double‐Helix Structure in Carrageenan–Metal Hydrogels: A General Approach to Porous Metal Sulfides/Carbon Aerogels with Excellent Sodium‐Ion Storage

The metal sulfide‐carbon nanocomposite is a new class of anode material for sodium ion batteries, but its development is restricted by its relative poor rate ability and cyclic stability. Herein, we report the use of double‐helix structure of carrageenan–metal hydrogels for the synthesis of 3D metal sulfide (M_xS_y) nanostructure/carbon aerogels (CAs) for high‐performance sodium‐ion storage. The method is unique, and can be used to make multiple M_xS_y/CAs (such as FeS/CA, Co₉S₈/CA, Ni₃S₄/CA, CuS/CA, ZnS/CA, and CdS/CA) with ultra‐small nanoparticles and hierarchical porous structure by pyrolyzing the carrageenan–metal hydrogels. The as‐prepared FeS/CA exhibits a high reversible capacity and excellent cycling stability (280 mA h^?1 at 0.5 A g^?1 over 200 cycles) and rate performance (222 mA h^?1 at 5 A g^?1) when used as the anode material for sodium‐ion batteries. The work shows the value of biomass‐derived metal sulfide–carbon heterostuctures in sodium‐ion storage.