Use of gum arabic to improve the fabrication of chitosan-gelatin-based nanofibers for tissue engineering.

Current techniques for fabricating chitosan-gelatin-based nanofibers require the use of corrosive and expensive solvents. Our novel method, however, using gum arabic and a mild (20 wt%) aqueous acetic acid solution as solvent can produce a solution with much higher chitosan-gelatin content (16 wt%). Without gum arabic, which greatly decreases the viscosity of the solution, such an outcome was unachievable. The solution was utilized to prepare electrospun chitosan-gelatin-polyvinyl alcohol-gum arabic nanofibers with a weight ratio of 8:8:2:0.5 (C8G8P2A0.5 nanofibers), in which polyvinyl alcohol could stabilize the electrospinning process. The stability and tensile strength (2.53 MPa) of C8G8P2A0.5 nanofibers (mats) were enhanced by glutaraldehyde crosslinking. Furthermore, mesenchymal stem cells attached and proliferated well on the mat. The strength-enhanced and cytocompatible C8G8P2A0.5 mats are thereby suitable for tissue engineering applications. More importantly, we have created a less expensive and safer method (one not using hazardous solvents) to fabricate chitosan-gelatin-based nanofibers.

Chitosan/pectin/gum Arabic polyelectrolyte complex: process-dependent appearance, microstructure analysis and its application.

Novel chitosan/pectin/gum Arabic polyelectrolyte complex (PEC) solutions and membranes with various compositions were prepared for biomedical applications. The appearance of the PEC solutions, either clear or turbid, was process-dependent and depended on how the three components were dissolved and mixed. The addition of gum Arabic to the chitosan and pectin significantly decreased the viscosities of the resultant PEC solutions due to the formation of globe-like microstructures that was accompanied by network-like microstructures and other molecular entanglements. The mechanical strength and hydrophilicity of the PEC membranes manufactured from the PEC solutions, especially for a weight ratio of 84/8/8 (chitosan/pectin/gum Arabic), were enhanced compared to pure chitosan membranes. Moreover, the use of the 84/8/8 PEC membranes as a drug carrier exhibited steady and fairly complete release of a drug (insulin) for 6h. Based on these promising results, the chitosan/pectin/gum Arabic PEC membranes have great potential in controlled drug release applications.

Kinetics of biodegradation of phenolic wastewater in a biofilm reactor.

This work presents a mathematical model to describe the biodegradation of phenolic wastewater in a fixed-biofilm process. The model incorporates diffusive mass transport and Haldane kinetics mechanisms. The model was solved using a combination of the orthogonal collocation method and Gear's method. A laboratory-scale column reactor was employed to verify the model. Batch kinetic tests were conducted independently to determine biokinetic parameters for the model simulation with the initial biofilm thickness assumed. The model simulated the phenol effluent concentration results well. Removal efficiency for phenol was approximately 94-96.5% for different hydraulic retention times at a steady-state condition. Model simulations results are in agreement with experimental results. The approaches of model and experiments presented in this paper could be used to design a pilot-scale or full-scale fixed-biofilm reactor system for the biodegradation of phenolic wastewater from petrochemical and oil refining plants.

Preparation and characterization of RGD-immobilized chitosan scaffolds.

Chitosan scaffolds were modified with RGDS (Arg-Gly-Asp-Ser) in the present work via an imide-bond forming reaction between amino groups in chitosan and carboxyl groups in peptides. Successful immobilization was verified with FTIR spectroscopy, and the immobilized amount was determined to be on the order of 10(-12) mol/cm2 through analysis of the immobilized amino acids. Results of experiments of cell culture with rat osteosarcoma (ROS) cells demonstrated that RGDS immobilization could enhance the attachment of ROS cells onto the chitosan, resulting in higher cell density attached to the RGDS-modified scaffold than to the unmodified scaffold. It should be noted that only RGDS, but not other peptide such as RGES, is effective in enhancing cell attachment and possible proliferation. Experiments of in vitro mineralization indicated that there were more cells on the RGDS-modified scaffold than on the unmodified scaffold, which tended to form bone-like tissues. The results presented in this work suggest that immobilization of RGDS can make chitosan scaffolds more compatible for the culture of osteoblast-like cells and the regeneration of bone-like tissues.

Preparation of porous scaffolds by using freeze-extraction and freeze-gelation methods.

Freeze-fixation and freeze-gelation methods are presented in this paper which can be used to prepare highly porous scaffolds without using the time and energy consuming freeze-drying process. The porous structure was generated during the freeze of a polymer solution, following which either the solvent was extracted by a non-solvent or the polymer was gelled under the freezing condition; thus, the porous structure would not be destructed during the subsequent drying stage. Compared with the freeze-drying method, the presented methods are time and energy-saving, with less residual solvent, and easier to be scaled up. Besides, the problem of formation of surface skin can be resolved and the limitation of using solvent with low boiling point can be lifted by the presented methods. With the freeze-extraction and freeze-gelation methods, porous PLLA, PLGA, chitosan and alginate scaffolds were successfully fabricated. In addition to the presentation of the morphologies of the fabricated scaffolds, preliminary data of cell culture on them are as well included in the present work.