Analysis of freeze-gelation and cross-linking processes for preparing porous chitosan scaffolds

Abstract

A newly developed freeze-gelation method for fabricating porous chitosan scaffolds for tissue engineering applications was analyzed. The influences of three process variables of freeze-gelation method on the tensile properties of the scaffolds were investigated. It was found that a higher freezing temperature (−20 °C) and concentration of acetic acid (1–2 M) significantly increased the tensile stress and strain of the scaffolds at maximum load, whereas a higher ethanol concentration (95%) in the rinse buffer slightly increased the tensile stress of the scaffolds at maximum load. Further, we successfully established a correlation to quantify the influence of these process variables of the freeze-gelation method on the tensile properties of the scaffolds. Hence, the correlation can be used for quantitative predictions of the tensile properties of the scaffolds. To enhance the tensile strength, the scaffolds were cross-linked using glutaraldehyde (GTA), N-(3-dimethyl-aminopropyl)- N′-ethylcarbodiimide hydrochloride (EDC), or tripolyphosphate (TPP). We found that both the tensile stress and strain at maximum load significantly and dose-dependently increased with the addition of the cross-linking agent, GTA. However, the addition of the cross-linking agents, EDC and TPP, only moderately increased the tensile stress and strain at maximum load, but no dose response was observed. In summary, our study analyzed the freeze-gelation and cross-linking processes for fabricating porous chitosan tissue engineering scaffolds with different tensile properties.