Spray-spinning: a novel method for making alginate/chitosan fibrous scaffold.

The subject of our investigations was the process of obtaining alginate/chitosan polyelectrolyte complex (PEC) fibers. In this study, a novel method named "spray-spinning" was developed for the making of these hybrid fibers. In spray-spinning, a chitosan solution was sprayed into a flowing sodium alginate solution and sheared into streamlines. The elongated streamlines subsequently transformed into alginate/chitosan PEC fibers. Average diameter of the fibers increased with the increasing of chitosan concentration used in spinning. The fibers showed a high water-absorbability of about 45 folds of water to their dry weight and retained their integrity after incubation in Minimum Essential Medium (MEM) for up to 30 days. In vitro co-culture experiments indicated that the fibers could support the three-dimensional growth of HepG2 cells and did not display any cyto-toxicity. Moreover, in vivo implanting experiments indicated that the connective tissue cells infiltrated into the implanted fibrous scaffolds in 3 weeks after surgery. These results demonstrated the potential applications of the as-spun fibers in regenerative medicine and tissue engineering.

[FTIR analysis of the enzymatic degradation of chitosan blend membranes].

Chitosan blend membranes were prepared by casting the mixture solution of highly deacetylated chitosan (HDC) and moderately deacetylated chitosan (MDC). FTIR was used to investigate the components of the blend membranes before and after lysozymic degradation. It was found that the ratio of MDC in the blen d membranes had a linear relation with the degree of deacetylation (DD) of the membranes. In enzymatic degradation process, DD of the membranes exhibited an increasing tendency. The FTIR data indicate that MDC component in the blend membranes can be removed by selective enzymatic degradation. This also suggests that FTIR can be used as an efficient and rapid method to investigate the degradation process of chitosan.

Hydro-spinning: a novel technology for making alginate/chitosan fibrous scaffold.

Alginate/chitosan polyelectrolyte complex (PEC) hybrid fibers are promising materials for scaffold-making in tissue engineering. In this study, a new method termed "hydro-spinning" was developed to make alginate/chitosan hybrid fibers. In hydro-spinning, a chitosan solution was pumped into a flowing sodium alginate solution and sheared into streamlines. These elongated streamlines subsequently transformed into alginate/chitosan PEC ribbon-like fibers before breaking up into pieces. Average diameter and chitosan content of the fibers correlated positively with the chitosan concentration used in spinning. These hybrid fibers showed a high water-absorbability of around 50-fold to 60-fold of water to their dry weight and could retain their integrity after saturation in minimum essential medium (MEM) medium for 30 days. In vitro culture experiments demonstrated that these fibers were able to support the three-dimensional growth of MCF-7, suggesting the potential applications of these fibers in biomedical and bioengineering fields such as tissue engineering.

Effect of surface wettability and charge on protein adsorption onto implantable alginate-chitosan-alginate microcapsule surfaces.

Alginate-chitosan-alginate (ACA) microcapsules have been developed as a device for the transplantation of living cells. However, protein adsorption onto the surface of microcapsules immediately upon their implantation decides their ultimate biocompatibility. In this work, the chemical composition of the ACA membranes was determined using X-ray photoelectron spectroscopy (XPS). The surface wettability and charge were determined by contact angle and zeta potential measurements, respectively. Then, the effects of surface wettability and charge on bovine fibrinogen (Fgn) and gamma globulin (IgG) adsorption onto ACA microcapsules were evaluated. The results showed that ACA microcapsules had a hydrophilic membrane. So, the surface wettability of ACA microcapsules had little effect on protein adsorption. There was a negative zeta potential of ACA microcapsules which varies with the viscosity or G content of alginate used, indicating a varying degree of net negatively charged groups on the surface of ACA microcapsules. The amount of adsorbed protein increased with increasing of positive charge. Furthermore, the interaction between proteins and ACA microcapsules is dominated by electrostatic repulsion at pH 7.4 and that is of electrostatic attraction at pH 6.0. This work could help to explain the bioincompatibility of ACA microcapsules and will play an important role in the optimization of the microcapsule design.