The Application Of Coaxial Electrospinning In The Surface Modification Of Tissue Engineering Scaffolds

A facile procedure based on coaxial electrospinning was adopted to prepare biodegradable core-shell fibrous scaffolds for tissue engineering. Biodegradable poly(e-caprolactone) (PCL) was used as the core material to maintain the mechanical strength of the composite scaffolds. Biocompatible gelatin or zein formed the shell structure of the fibers to enhance cell adhesion and proliferation. Primarily, the PCL/gelatin core-shell fibrous system was studied. The effect of the feed rate of the inner PCL fluid on the fibers' properties, such as fiber morphology, composition and/or mechanical characteristic, was investigated. It was found that core-shell structured fibers with narrow size distribution and smooth surface morphology could be obtained when the feed rate of the inner dope was below the critical rate. With the increase of the feed rate of the inner dope, there was an increase in the diameter of both the inner PCL fibers and the whole core-shell fibers. Gelatin content in the core-shell fibrous membranes, as well as the relative molar percent of alpha carbon atoms from gelatin molecules to all the alpha carbon atoms at the surface of the core-shell fibers, decreased with an increase in the feed rate. PCL chains in the inner layer of the core-shell fibers had higher orientation degree than those in the membranes prepared by uni-axial electrospinning. The outer gelatin layer in the core-shell fibers was crosslinked with glutaraldehyde solution in ethanol. By optimizing glutaraldehyde/gelatin feed ratio, the crosslinked membranes with high porosity could be obtained. The core-shell fibrous membranes displayed different stress-strain response from the electrospun membranes composed of a single component. A discontinuous feature of the stress-strain curves was observed, which could be attributed to the asynchronous failure of the inner PCL fiber and the outer gelatin layer. Crosslinking of the outer gelatin layer strengthened the core-shell fibrous membranes. The hydrated, crosslinked core-shell fibrous membranes showed comparable mechanical property to the electrospun PCL membrane. Preliminary results of cell culture suggested that the crosslinked, core-shell fibrous scaffold couldprompt fibroblast adhesion and proliferation.Latterly, we studied the PCL/zein core-shell fibrous system. Like the former system, it was found that core-shell structured fibers with narrow size distribution and smooth surface morphology could be obtained when the feed rate of the inner dope was below the critical rate. With the increase of the feed rate of the inner dope, there was an increase in the diameter of both the inner PCL fibers and the whole core-shell fibers. The zein shell layer improved the wettability of the inner PCL fiber greatly. The aggregation of PCL chains in the inner layer of the core-shell fibers was similar to those in the membranes prepared by uni-axial electrospinning. The mechanical properties of the as-spun membrane were sensitive to the composition of the membrane. With the increase of the content of inner PCL layer in the core-shell fibers, the break elongation increased, while the yield strength decreased. In addition, more PCL the composite fibers contain, more stable the fibrous scaffold is in the cell culture condition.From our study, it can be concluded that cyto-compatible fibrous scaffolds with morphology stability could be prepared simply by co-axial electrospinning. In other words, the surface modification of uni-axial electrospun fibers can be achieved by co-axial electrospinning.