Abstract: A biodegradable hydrogel comprises a water-soluble dextran having aldehyde groups cross-linked with a water-soluble chitosan. Various chemical agents may be encapsulated in the hydrogel or bonded thereto for controlled release. The hydrogel may be applied as a coating to reduce the likelihood of bacterial attachment and biofilm growth; used in tissue engineering applications to prevent tissue ingrowth; or used as a matrix in which cells may proliferate. The components of the hydrogel can be applied sequentially as a spray or by immersion and will gel spontaneously at environmental or physiological temperatures.