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The miscibility, bioactivity, and antibacterial properties of chitosan/collagen specimens were systematically studied. The specimens were prepared by blending collagen and chitosan with varying deacetylation degrees in solutions; the collagen molecules had been extracted from pigskins using the acid swelling-pepsin digestion method. To understand the miscibility properties of collagen and chitosan molecules, the intrinsic viscosity and differential scanning calorimetry analysis of collagen, chitosan, and collagen/chitosan specimens were performed. The instrinsic viscosity measurements suggested that chitosan and collagen molecules with varying deacetylation degrees were miscible at molecular level for all compositions and degrees of deacetylation of chitosan/collagen mixture solutions prepared in this study. Fourier transform infrared analyses suggested that the percentage of preserved triple helix structures present in collagen molecules in collagen/chitosan specimens decreased with increasing chitosan contents, since the ratios of peak absorbance at 1239 cm−1of amide III and 1455 cm−1of C‒H bending of collagen/chitosan specimens decreased significantly with increase in their chitosan contents. Abnormally high denaturation temperatures (Td) were observed as the chitosan contents of collagen/chitosan specimens reached 40 wt%, at which Tdof collagen molecules was even higher than that of the corresponding pure chitosan molecules with varying deacetylation degrees. The antibacterial activity of collagen/chitosan blends increased consistently with increasing deacetylation degrees and concentrations of chitosan molecules in collagen/chitosan solutions. Possible explanations for these interesting thermal denaturation, antibacterial, and miscibility properties of chitosan/collagen specimens are reported. [ABSTRACT FROM PUBLISHER]

Current attempts for synthesizing chitosan-modified magnetite nanoparticles (CS-MNPs) as drug carrier involve use of surfactants, which brings potential cytotoxicity and decrease of saturated magnetization (Ms). To address this, we developed a facile single-step method for synthesizing CS-MNPs. The developed method offers several advantages. No surfactant was involved and the magnetite nanoparticles were in-situ-coated with a chitosan (CS) layer, which endows the CS-MNPs with enhanced physical and chemical properties. The Ms of magnetite was significantly increased (55.5 emu/g) as compared to magnetite nanoparticles modified by surfactants with oxygen ligands, indicating their potential applications as drug-delivery systems (DDSs) where high saturated magnetization (Ms) is preferred. Besides, the amount of CS layer of CS-MNPs was approx. 24 wt%, which makes the synthesized CS-MNPs highly biocompatible as no acute adverse effect of the viability on MG-63 cells was observed at doses up to 0.2 mg/ml. Macropinocytosis is the main endocytic mechanism of MG-63 cells internalize CS-MNPs, which might avoid lysosomal degradation of the CS-MNPs. The synthesized CS-MNPs have potential applications in the fields of targeted drug delivery, separation for purification and immunoassay and magnetic resonance imaging. [ABSTRACT FROM AUTHOR]

Liesegang rings, periodical bands or ring patterns formed by inorganic precipitation in polymer gel medium, have attracted lots of interest of researchers aiming to construct ordered structures. Inspired by the Liesegang ring phenomena, chitosan, instead of inorganic species, was used as building block to construct a chitosan hydrogel with concentric multilayers in a protonated chitosan/NaOH reaction system by alternate soaking in NaOH solution and water. The morphology of concentric multilayers structure was characterized by environmental scanning electron microscopy. The upload and release behavior of isoniazid was also investigated. The quantitive rules of the concentric layer position/the square root of reaction time and the position of the consecutive concentric layer coincide with the time law and space law of the classical Liesegang ring phenomena, respectively. The chitosan solution converts into a hydrogel accompanied by remarkable volume shrinkage due to hydrogen bonds reconstruction and electrostatic repulsion disappearance. The separated concentric multilayers can be formed due to the fluctuation of hydroxide ions concentration when the neutralization is interrupted by alternate soaking in NaOH solution and water. The major difference of the concentric multilayers in chitosan hydrogel from the classical Liesegang ring phenomena occurring in inorganic precipitation systems is that chitosan not only plays the role of reactant in chitosan hydrogel formation, but also acts as supporting reaction medium to control the diffusion behavior of hydroxide ions. The porosity and equilibrium swelling ratio of the chitosan xerogel are 63% and 1100%, respectively, which is feasible for drug uploading through diffusion or absorption. The isoniazid release kinetics are dominated by the diffusion-erosion model. The chitosan hydrogel with concentric multilayers structure loaded with isoniazid will have wide applications in treatment of bone tuberculosis. [ABSTRACT FROM AUTHOR]

A magnetic dye affinity adsorbent was prepared by coating the magnetic nanoparticles (MNPs) with chitosan (CS), which significantly decreased the non-specifically adsorbing protein. Following this, Reactive Red 120 (Red 120), chosen as a dye affinity ligand, was immobilized onto the chitosan-coated magnetic nanoparticles (CS-MNPs) to obtain the specific protein adsorption. The prepared functionalized adsorbents were characterized by SEM, FTIR, XRD, VSM, and elementary analysis. Factors influencing the adsorption of bromelain, e.g., initial protein concentration, medium pH, and ionic strength were investigated. The adsorption isotherm fitted the Freundlich model well. The regeneration experiment showed that the affinity superparamagnetic particles were suitable for bromelain adsorption. [ABSTRACT FROM AUTHOR]

Polymers with negatively charged groups (-COOH, -OH or -PO4H2) were frequently adopted to induce or promote apatite deposition through electrostatic interaction. However, chitosan with positively charged groups (-NH2) was ignored, although it could bind most of metal ions through chelation. Based on the chelation properties of the amino group, a chitosan hydrogel obtained via physical cross-linking was used as template for ion assembly. Gradient structural bone-like apatite induced by chitosan hydrogel was achieved via ion assembly within a few hours under ambient conditions, in which amino groups of chitosan acted as anchors between chitosan and apatite nucleation. The phase and component of bone-like apatite were similar to apatite in rabbit ribs according to XRD patterns and FT-IR spectra. XRD results revealed that bone-like apatite was carbonated apatite and preferred growth orientation in the direction of c-axis. The profile of elements distribution in chitosan suggested that the content of calcium and phosphorous elements decreased with the increase of depth along the radius direction, which was accompanied by the formation of apatite-rich regions near the outer layer. When chitosan was dipped in calcium ions solution, Ca2+ ions bound amino groups of chitosan and formed chitosan/calcium ions complexes (CS-NH2...Ca2+). CS-NH2...Ca2+ subsequently attracted negatively-charged phosphate ions through electrostatic interaction. When ion assembly finished, Ca and P ions in the chitosan hydrogel converted into ACP with Ca/P ratio of 1.19. ACP converted into bone-like apatite with Ca/P ratio of 2.01 after alkali treatment. [ABSTRACT FROM AUTHOR]