Modifying the Pores of an Inverse Opal Scaffold With Chitosan Microstructures for Truly Three‐Dimensional Cell Culture

Inverse opal scaffolds have recently emerged as a novel class of scaffolds with uniform and controllable pore sizes for tissue engineering to provide better nutrient transport, a uniform cell distribution, and an adjustable microenvironment for cell differentiation. However, when the pore size of the scaffold is much larger than the dimension of a cell, the cell actually encounters a local 2D environment and the void space associated with the pore can not be efficiently utilized. Here, we demonstrate that a truly 3D microenvironment can be created inside a pore by further functionalizing the as‐prepared inverse opal scaffold with a second polymer by freeze‐drying. The resultant inverse opal scaffold with hierarchically structured pores can enhance both cell proliferation and tissue infiltration.     

呋喃甲酰壳聚糖的制备、表征及其抗氧化活性

以壳聚糖与呋喃甲酰氯反应得到呋喃甲酰壳聚糖。通过FT-IR、1 H-NMR、X射线衍射、热重分析、溶解度实验、元素分析、抗氧化活性测试等手段对产物进行了结构和性能表征。结果表明：产物为目标产物且热稳定性好于壳聚糖;在水中的溶解性能良好,溶解度为0.04g/mL;取代度为0.69;当对羟基自由基的清除率达到50%时,呋喃甲酰壳聚糖的质量浓度为1.1mg/mL,其还原能力随质量浓度增加而增强,抗氧化活性优于壳聚糖。     

Antibacterial activity of pH‐sensitive genipin cross‐linked chitosan/poly(ethylene glycol)/silver nanocomposites

Novel nanocomposites consisting of genipin cross‐linked chitosan (GC), poly(ethylene glycol) (PEG), and silver nanoparticles were prepared for such biomedical applications as the wound‐healing materials. Various amounts of silver nanoparticles were dispersed in the GC/PEG hydrogel matrix without severe aggregation. The effects of composition and silver nanoparticles on the physico‐chemical properties of samples were evaluated by infrared analysis, contact angle measurements, and swelling tests. The GC/PEG/Ag nanocomposite showed a pH‐sensitive swelling behavior. The surface hydrophilicity of GC/PEG/Ag nanocomposites was improved with the increase of silver nanoparticle content. L929 cell attachment was improved in the presence of silver nanoparticles. The antimicrobial function was assessed for the GC/PEG/Ag nanocomposites containing the silver content over 100 ppm. The silver nanoparticles had the dual functions of reinforcing structural stability and enhancing antimicrobial activity of GC/PEG/Ag nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.     

Novel 2-Hydroxypropyltrimethyl Ammonium Chitosan Derivatives: Synthesis,Characterization, Moisture Absorption and Retention Properties

Recent years have seen a steady increase in interest and demand for the use of humectants based on biodegradable natural polymers in many fields. The aim of this paper is to investigate the moisture absorption and retention properties of 2-hydroxypropyltrimethyl ammonium chitosan derivatives which were modified by anionic compounds via ion exchange. FTIR, ¹H NMR, and ¹³C NMR spectroscopy were used to demonstrate the specific structures of chitosan derivatives. The degrees of substitution for objective products were calculated by the integral ratio of hydrogen atoms according to ¹H NMR spectroscopy. Meanwhile, moisture absorption of specimens was assayed in a desiccator at different relative humidity (RH: 43% and 81%), and all target products exhibited enhanced moisture absorption. Furthermore, moisture retention measurement at different relative humidity (RH: 43%, 81%, and drier silica gel) was estimated, and all target products possessed obviously improved moisture retention property. Specifically, after 48 h later, the moisture retention property of HACBA at 81% RH was 372.34%, which was much higher than HA (180.04%). The present study provided a novel method to synthesize chitosan derivatives with significantly improved moisture absorption and retention properties that would serve as potential humectants in biomedical, food, medicine, and cosmetics fields.     

The effect of high hydrostatic pressure on the muscle proteins of rainbow trout (Oncorhynchus mykiss Walbaum) fillets wrapped with chitosan-based edible film during cold storage (4±1°C)

This study was to determine the effects of changes that occurred in the muscle proteins of fresh rainbow trout (Oncorhynchus mykiss) fillets during storage at 4±1°C as a result of packaging in vacuum (C), subject to high pressure after packaging in vacuum high hydrostatic pressue (HHP), packaged in vacuum after wrapping with chitosan film (CFW) and subject to high pressure after wrapping with chitosan-based film and packaged in vacuum (HHP+CFW ). Samples were subjected to SDS-PAGE in four-day intervals and the densitometric analyses of the gels were carried out. According to the results, minor changes were determined in the major bands of the sarcoplasmic and myofibrillar muscle fractions of trouts as a result of HHP application and CFW. The most important change occurred in the myofibrillar muscle fraction as a decrease in the densities of the bands at 200 and 31.4 kDa after HHP application. Similarly, the sarcoplasmic muscle fraction of trout fillet decreased in the densities of the bands at 39.3, 26.6 and 23.3 kDa after HHP application. In addition, it is thought that the bands that occur at 30 kDa in the myofibrillar muscle fraction and at 20.7 kDa at the sarcoplasmic muscle fraction may be related with the degradation of trouts during cold storage.     

Preparation and Characterization of New Biodegradable Films Made from Poly(L-Lactic Acid) and Chitosan Blends Using a Common Solvent

Poly-(L-lactic acid) (PLLA) has been widely used for various biomedical applications due to its interesting properties such as its mechanical behavior, processability, biocompatibility, and biodegradability. Blending this polymer with chitosan that, besides being biodegradable and hydrophilic, can interact with anionic glycosaminoglycans, proteoglycans, and other negatively charged molecules of the extracellular matrix, could constitute an excellent way to improve the biological performance of PLLA in these kinds of applications. Such blends could also be used in environmental applications. In this work a new and simple method of preparing biodegradable blends of chitosan and PLLA at room temperature was developed. To the best of our knowledge, this is the first time that a common solvent for the two polymers has been used, hexafluor-2-propanol (HFIP), to produce a homogeneous solution containing both PLLA and chitosan. We also anticipate that this solvent can also be used to compatibilize other combinations of natural and synthetic polymers. Membranes were then obtained by solvent casting. Films with different fractions of each component were successfully prepared and didn't show visible phase separation. The prepared films were characterized by differential scanning calorimetry (DSC) in order to analyze the miscibility of the two components as a function of the composition of the film.     

Studies on the Miscibility of Chitosan/Poly(vinyl pyrrolidone) Blend in Solution by Viscometry,Ultrasonic Velocity,Density and Refractometry Techniques at 30, 40, and 50°C

Polymer blends of chitosan (CHI) with poly(vinyl pyrrolidone) (PVP) have been prepared by solution blending, and their miscibility studies were carried out by using physical techniques over an extended range of concentration and composition in buffer solution. The viscosity, ultrasonic velocity, density, and refractive index were measured at 30, 40, and 50°C, respectively. Using viscosity data, the interaction parameter μ and α were computed to probe the miscibility. These values revealed that the blend is miscible when the chitosan content is more than 60% in the blend at all temperatures. The obtained results were further confirmed by the ultrasonic velocity, density, and refractive index measurements.     

Properties and Preparation of Chitosan/Silanol Quaternary Ammonium Modified Silica Hybrids Using Sol–Gel Process

Chitosan/modified silica nanocomposites, with a sol–gel process being used to prepare a silanol quaternary ammonium modified silica possessing antimicrobial activity, were investigated, as well as the thermal properties, morphology, optical, mechanical, antimicrobial, and adsorption properties of this type of nanocomposite. Grafting of the modifier onto nanosilica was confirmed through the Fourier transform infrared (FTIR) spectra. X-ray diffraction patterns indicated that the chitosan structure was not disrupted from the incorporation of the modified silica. Fracture surfaces with no clear micro-phase separation were observed by scanning electron microscopy (SEM), which indicated the good interaction of chitosan and the modified silica. The organic modifier tended to cause the aggregation of the modified silica at higher content on a submicron scale based on transmission electron microscopy (TEM) analysis, which might be due to a decrease of the stability factor originating from the negative charges on silica. With the introduction of modified silica, the optical transmittance decreased at higher organic modifier content in agreement with TEM analysis. The elongation at break remained largely unchanged, but tensile strength and Young's moduli deteriorated in modified silica filled systems in comparison with pure silica filled systems. The introduction of the organic modified silica gave a higher antibacterial activity. All nanocomposites were capable of chelating Cu (II) as well as Fe (III) at a different degree. Thus, the prepared chitosan/modified silica nanocomposites exhibited both antimicrobial and chelating properties.     

Preparation of Long-Chain Fatty Acyl-Grafted Chitosan in an Ionic Liquid and Their Self-Assembled Micelles in Water

Controllable synthesis of self-associating lauroyl-grafted chitosan with high molecular weight was realized in ionic liquid reacting media. The obtained lauroyl chitosan with different grafting degrees was characterized by FT-IR and ¹H-NMR spectra. The chitosan derivatives were able to self-assemble into spherical polymeric micelles in water. The onset of micellization or critical micelle concentration (CMC) was estimated by fluorescence spectroscopy. The hydrodynamic diameters of various lauroyl chitosan micelles, determined by dynamic light scattering, were in the range of 122–295 nm. The morphology of the micelles was observed by scanning electron microscopy. The self-assembly behavior and the size of the assembled micelles of lauroyl chitosan were affected by the grafting degree of lauroyl groups. Generally, higher grafting degree resulted in lower CMC and smaller micelle size. These lauroyl chitosan nano-micelles may have potential applications in biological and medical fields.     

Direct Electrochemistry of Hemoglobin in Chitosan/Multiwalled Carbon Nanotubes/Ionic Liquid–Modified Carbon-Paste Electrode

Abstract

The direct electrochemistry of hemoglobin (Hb) was realized on chitosan and multiwalled carbon nanotubes (MWCNTs)–modified carbon ionic liquid electrode (CILE). The CILE was fabricated first and further modified by MWCNTs to get an electrode as MWCNTs/CILE. The Hb was immobilized on the surface of MWCNTs/CILE with the help of chitosan film. Ultraviolet–visible (UV-vis) and Fourier transform–infrared (FT-IR) spectra indicated that Hb kept its native structure in the modified film. A pair of well-defined quasi-reversible redox peaks of heme Fe(III)/Fe(II) couple appeared with the formal potential (E^0′) as ?0.314 V (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The modified electrode showed good electrocatalytic ability for the reduction of trichloroacetic acid.