Effects of Neutralization and Crosslinking Agents on the Morphology of Chitosan Electrospun Scaffolds

Chitosan, a natural polymer derived from chitin by deacetylation process of chitin, has gained an enormous interest in tissue engineering due to its unique features such as antibacterial activity and wound healing properties. Electrospinning of acidified chitosan solution is one of the most widely-used approaches in fabrication of 3D scaffolds. Although there are some reports addressing morphology tailoring of the chitosan nanofibers through solution electrospinning, there is no comparative report concerning the neutralization and stabilization conditions of chitosan electrospun fibers. Therefore, this article compares the effects of different neutralizing agents such as aqueous solutions of sodium carbonate (Na2CO3) and potassium carbonate (K2CO3), and crosslinking reagents including glutaraldehyde (GA) and genipin on morphology of electrospun chitosan fibers. After neutralization and stabilization processes, Fourier transform infrared spectroscopy (FTIR) was employed to investigate the morphology of fibers. Furthermore, the influence of the aforementioned parameters on stability of fibers was probed using scanning electron microscopy. SEM images illustrated that the scaffold resulting from electrospinning of 4 wt% chitosan solution in a mixture of trifluoroacetic acid (TFA) and dichloromethane (DCM) possessed a well-formed nanofibrous structure. Afterwards, different methods for neutralization and stabilization of the electrospun chitosan nanofiber mats were performed. In this respect, aqueous solutions of both Na2CO3 and K2CO3 salts (1M) were employed as neutralization agents and GA and genipin were used as two different crosslinking agents. Based on SEM analysis, the chitosan fibers, crosslinked with genipin, showed better morphology than a scaffold which was crosslinked with glutaraldehyd

Hydroxyapatite scaffolds infiltrated with thermally crosslinked polycaprolactone fumarate and polycaprolactone itaconate

In this work, two unsaturated derivatives of polycaprolactone (PCL), polycaprolactone fumarate (PCLF), and polycaprolactone itaconate (PCLI), have been synthesized and used as an infiltrating polymer to improve the mechanical properties of brittle hydroxyapatite (HA) scaffolds. PCLF and PCLI were first synthesized through polyesterification of the low molecular weight PCL diols with fumaryl chloride and itaconyl chloride respectively, and then characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and differential scanning calorimetry analysis. HA scaffolds were sintered using a foam replication technique, with porosity of about 60%. Polymer-HA composites were obtained by infiltrating the HA scaffolds with PCLF and PCLI solution (12.5 and 30 w/v in dichloromethane) followed by thermal crosslinking. The polymer infiltrated HA scaffolds were characterized by scanning electron microscopy, porosimetry, and gravimetrical analysis. The polyesterification reaction of PCL diols with fumarate chloride was more efficient than itaconyl chloride and dependent upon the molecular weight of the initial PCL precursor; the resultant PCLF demonstrated a degree of substitution of 1.2, 4.2, and 2.7 times higher than PCLIs. Polymer infiltration improved the compressive strength of the HA scaffolds, and based upon the type of macromer (PCLF or PCLI) and also their concentration in infiltrating solution (12.5 or 30 w/v %) compressive strength increased about 14-328%. In all studied samples, the reinforcement effect of PCLF infiltration was higher than PCLI. The macromers and their corresponding infiltrated HA scaffolds did not show any significant cytotoxicity toward human primary osteogenic sarcoma cell (G92 cell lines), in vitro. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 98A: 257-267, 2011