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Chitosan nanoparticles (Ch NPs) with individual particles 10-30 nm in size and average aggregate sizes of 240 nm were prepared via ionic gelation. Ordered mesoporous Mobil Composition of Matter No. 41 (MCM-41) with a surface area of 1590m2/g was prepared via a sol-gel method. The nanocomposites were prepared via the in situ dispersion of MCM-41 in chitosan followed by ionic gelation with a multivalent anion to produce MCM-41-impregnated Ch NPs or via the mixture of dispersed MCM-41 with preprepared Ch NPs to produce Ch NPs supported on MCM-41. The beryllium-uptake efficiency was studied with different pH values, contact times, and initial Be(II) concentrations. The maximum achieved uptake efficiencies of the nanocomposites (95% and 96%) were superior to that of MCM-41 (38%) and higher than that of Ch NPs (90%). The nanocomposite formulas facilitated post-treatment separation while maintaining a high beryllium-uptake efficiency. The Be(II)-uptake process for all of the materials followed the pseudo-second-order kinetic model and both the Langmuir and Freundlich isotherms. [ABSTRACT FROM AUTHOR]

ABSTRACT Tissue engineering holds an exciting promise in providing a long-term cure to bone-related defects and diseases. However, one of the most important prerequisites for bone tissue engineering is an ideal platform that can aid tissue genesis by having biomimetic, mechanostable, and cytocompatible characteristics. Chitosan (CS) was chosen as the base polymer to incorporate filler, namely beta-tri calcium phosphate (β-TCP). This research deals with a comparative study on the properties of CS scaffolds prepared using micro- and nano-sized β-TCP as filler by freeze gelation method. The scaffolds were characterized for their morphology, porosity, swelling, structural, chemical, biodegradation, and bioresorption properties. Rheological behavior of polymer and polymer-ceramic composite suspensions were analyzed and all the suspensions with varying ratios of β-TCP showed non-Newtonian behavior with shear thinning property. Pore size, porosity of micro- and nano-sized composite scaffolds are measured as 48-158 μm and 77% and 43-155 μm and 81%, respectively. The scaffolds containing nano β-TCP possess higher compressive strength (∼2.67 MPa) and slower degradation rate as compared to composites prepared with micro-sized β-TCP (∼1.52 MPa). Bioresorbability , in vitro cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, proliferation by Alamar blue assay, cell interaction by scanning electron microscope, and florescence microscopy further validates the potentiality of freeze-gelled CS/β-TCP composite scaffolds for bone tissue engineering applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41025. [ABSTRACT FROM AUTHOR]

Composite chitosan/active carbon (AC) hydrogels were elaborated by a novel route, consisting in exposing the chitosan solution to ammonia vapors. This vapor-induced gelation method was compared with the conventional elaboration process, a direct immersion of the chitosan solution in liquid ammonia. The hydrogels were characterized to evaluate their potential application as wound-dressings, mostly regarding their morphology, mechanical properties, swelling behavior, and sorption capacities for malodorous compounds emitted from wounds as diethylamine (DEA). The influence of elaboration route, chitosan concentration, and AC incorporation was studied. The results show that freeze-dried hydrogels have a porous asymmetric structure dependent on the chitosan concentration and which promotes exudates drainage. The nanostructure of the parent hydrogel is semi-crystalline and slightly dependent on the gelation conditions. It confers on hydrogel an acceptable mechanical behavior (compressive modulus up to 1.08·105 Pa). Hydrogels including AC display enhanced sorption kinetics for DEA, with sorption capacities up to 49 mg g−1. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

This study shows the potential of chitosan (CH) nanoparticles as both an oral and IV drug delivery system using the anticancer drug cladribine as a model drug. Smooth, spherical nanoparticles were prepared by the ionotropic gelation of CH with sodium tripolyphosphate. Nanoparticle size depended on degree of hydration, drug loading, and crosslinking conditions, with the smallest nanoparticles in the size range of 212 ± 51 nm. Cladribine was entrapped in the CH matrix with an entrapment efficiency of up to 62%, depending on the initial loading. The release of cladribine followed a near-Fickian diffusion rate over the first several hours and then reached a plateau. A second release phase began after 30-40 h of incubation in the release medium, and proceeded until ∼100 h. Loaded CH nanoparticles that were crosslinked with genipin showed a delayed release profile, with only 40% of loaded drug being released after 100 h. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

In this study, the influences of different solvents on highly porous chitosan (CS)-based hydrogel have been investigated by monitoring the characterizations of the hydrogel. The results determined from rheological analysis and scanning electron microscope showed that all the CS dissolved in different solvents used in this study, when neutralized by α,β-glycerophosphate solution, could transform into a highly porous three-dimensional hydrogel at a certain temperature, and the aperture size and shape of the pores were related to solvent variety and solvent strength. The cytocompatibility and in vivo injection experiments demonstrated that the hydrogel prepared with acetic acid, hydrochloric acid, or lactic acid as the solution of CS had low toxicity and high histocompatibility. This study suggested that the gelation temperatures, pH values, turbidity, complex viscosities, and porous structures of the hydrogels for certain experimental applications could be tailored by adjusting the solvent variety and solvent strength of the CS solution. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

A novel, physically stabilized hydrogel system composed of chitosan (Chi) or its derivatives [e.g., carboxymethyl chitosan (CMC), sodium carboxymethyl chitosan, or trimethyl carboxymethyl chitosan (TMCMC)] with poly(vinyl pyrrolidone) (PVP) or opened-ring poly(vinyl pyrrolidone) (OR-PVP) were prepared and characterized. TMCMC was synthesized by a novel method with dimethylsulfate as the methylation agent. The synthesized materials were characterized by Fourier transform infrared spectroscopy, H-NMR, C-NMR, and size exclusion chromatography. The mechanical properties, gel fraction, swelling behavior, and water state of the prepared hydrogels were investigated. Gelation occurred when the OR-PVP and Chi solutions were blended within a few seconds. However, the gelation of the OR-PVP and CMC solutions needed pH adjustment. No gelation occurred when the solutions of TMCMC and PVP or OR-PVP were blended. The quaternization or protonization of NH groups may have prevented the gelation of the solutions. The amino groups of Chi derivatives should have been free to take part in hydrophilic bonds between the two polymers. The physical entanglement of polymeric chains and strong hydrogen bonds between the polymers were considered as mechanisms for the formation of the physical hydrogels. The physical hydrogels showed ionic and pH-sensitive swelling properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Chitosan has been extensively exploited in biomaterials research because of easy tailorable properties. Chitosan fibers are produced through either wetspinning or electrospinning. However, it is difficult to produce few microns fibers using either of these techniques. Present study focuses on production of ultrafine chitosan fibers through modified wetspinning technique by injecting homogenous chitosan solution through a very fine hole of silicone tube into either sodium tripolyphosphate (STPP) or sodium hydroxide (NaOH) bath by applying positive pressure. The gelation behavior of the chitosan was evaluated with STPP and NaOH solution through rheological study for comparative spinnability of chitosan in STPP and NaOH bath. Although gel strength of chitosan-NaOH system (240 Pa) was four times higher than that of chitosan-STPP system, gel breakdown rate was higher in previous case. From Fourier infrared spectroscopy (FTIR) analysis, ionic cross-linking between TPP and chitosan molecules in chitosan-TPP fibers was confirmed. Scanning electron micrographs showed fine chitosan fibers with average diameter of ∼ 10 μm. These nonwoven fibers/scaffolds with interconnected porosity may find potential biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

The article discusses the covalent immobilization of &#x03B2-galactosidase from Aspergillus oryzae on novel biopolymers of carrageenan coated with chitosan. The chitosan-carrageenan polyelectrolyte complex have shown to increase the thermal stability of the carrageenan gel from 35 degrees Centrigrade to 95 degrees Centigrade. Also, the covalent immobilization and stabilization of the &#x03B2-galactosidase occur at the same time, providing a simple and quick method for preparation.

The article presents a study that investigated an injectable in situ gel-ling thermosensitive hydrogel system based on chitosan and gelatin blends. The study used gelatin to achieve correct buffering and other physicochemical conditions including control of hydrophobic interactions and hydrogen bonding. It relied on FTIR, swelling, and rheological analysis to assess the chitosan/gelatin hydrogels. It revealed the endothermic gelation of chitosan/gelatin solutions using rheological analysis.

The article discusses a study which focused on the preparation of chitosan (CS) nanoparticles with different mean sizes ranging from 100 to 195 nanometer (nm) through ionic gelation of CS and poly(acrylic acid) (PAA). The study examined the variations in thermal solution pH value and CS: PAA volume ratio for their effects on nanoparticle size, intensity of surface charge, and tendency toward particle aggregation. The particle size and structure of the CS-PAA nanoparticles are described.

The article presents a study on the antioxidant activity and physicochemical characterization of quercetin-loaded chitosan nanoparticles. The researchers prepared chitosan nanoparticles based on the ionic gelation of chitosan with TPP anions, after which they dissolved chitosan in acetic aqueous solution. They also used a scanning probe Microscope SPM-9500 J3 instrument. They found that the quercetin in an amorphous state was encapsulated by chitosan nanoparticles.

The rheological behavior of chitosan/alginate solutions was investigated in relation to gelation and polyelectrolyte complex (PEC) formation. Before mixing, the chitosan and the alginate solutions were both homogeneous fluids. However, heterogeneity developed after mixing, accompanied by a serious increase of viscosity. To determine the sol–gel state of the solutions, the viscoelastic variables, such as the dynamic storage modulus (G′) and loss modulus (G″), the loss tangent, and the viscoelastic exponents for G′ and G″, were obtained. Depending on the concentration, the chitosan/alginate solutions revealed unexpected rheological behavior. At a polymer concentration of 1.0 wt %, the chitosan/alginate solution was in a viscoelastic gel state, whereas, at higher concentrations, viscoelastic sol properties were dominant. A viscoelastic gel state for the chitosan/alginate solution was induced based on the weak formation of fiber‐shaped precipitates of a PEC at a low polymer concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1408–1414, 2007 [ABSTRACT FROM AUTHOR]

Chitosan gel was prepared by crosslinking method. To make use of chitosan gel, the optimization of elution conditions and the adsorbent characteristics of chitosan gel were discussed in this article. The optimum elution conditions were c (NaCl) = 0.05 mol/L in Tris‐HCl (pH, 9.05) at the flow rate of 2.0–3.0 mL/min with chitosan gel (particle sizes, 120–140 μm). The effects of contact time, pH, initial BSA concentration, and temperature on adsorption were studied. The equilibrium data could be described well by Langmuir, Freundlich, and Redlich–Peterson models. Adsorption dynamics had been successfully studied by Langergren, intraparticle diffusion model and Avrami model. The thermodynamics parameters ΔG°, ΔH°, and ΔS° were calculated. The spectra studies indicated that the interaction between gel and protein was chiefly through electrostatic attraction in the shape of hydrogen bond. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1495–1506, 2007 [ABSTRACT FROM AUTHOR]