Preparation of novel bilayer hydrogels by combination of irradiation and freeze–thawing and their physical and biological properties

Abstract

AbstractBACKGROUND: Hydrogels made by irradiation or freeze–thawing often exhibit poor mechanical strength; therefore we investigated a novel synthetic method to circumvent this detrimental effect. We report a series of novel bilayer poly(vinyl alcohol) (PVA)/water‐soluble chitosan (ws‐chitosan)/glycerol hydrogels prepared by a combination of irradiation and freeze–thawing. Scanning electron microscopy morphology, swelling behavior, mechanical strength, elongation at break, PVA dissolution behavior and bovine serum albumin (BSA) release profile of the bilayer hydrogels were compared with those of hydrogels made by irradiation and freeze–thawing followed by irradiation. The cytotoxicity of the bilayer hydrogels was studied using a tetrazolium salt (MTT) assay.RESULTS: The novel bilayer hydrogels contain one layer made by freeze–thawing followed by irradiation and the other layer made by irradiation. The preparation method provides the two layers with good combination force in the wet state. However, the two layers are not combined very well in the freeze‐dried state due to the difference in microstructure. The bilayer hydrogels have large swelling capacity and good mechanical strength, and these properties can be varied by changing freeze–thawing cycles, irradiation doses and the relative thickness of the two layers. The PVA and BSA release behaviors show that the bilayer hydrogels have a small amount of dissolved PVA and can prolong the BSA release time. The MTT assay shows that extracts of the bilayer hydrogels are non‐toxic towards L929 mouse fibroblasts.CONCLUSION: The novel bilayer hydrogels prepared in this study show good physical properties with no cytotoxicity, indicating that they are suitable for biomedical applications, such as in wound dressings and drug delivery devices. Copyright © 2009 Society of Chemical Industry