the present invention provides compositions and methods for tissue repair using a cytocompatible self - gelling cross - linked hydrogel . the composition comprises a biocompatible mixture of chitosan , bifunctional dialdehyde , and hydroxylated polymer , which can be used to immobilize or encapsulate viable cells , or bioactive substances . the method includes the process of mixing bioactive substances , live cells , and / or extracellular matrix components with a cross - linking solution comprising a bifunctional aldehyde - treated hydroxylated polymer such as hydroxyethyl cellulose . the cross - linking solution is then mixed homogenously with a neutral isotonic chitosan solution . the chitosan becomes cross - linked by the bifunctional aldehyde , while the cells are protected from potentially nocive effects of the aldehyde cross - linker by the hydroxylated polymer . the injectable solution retains cell viability and bioactivity , and immobilizes cells at the site of injection or delivery . depending on the particular application , mixtures of chitosan and bifunctional dialdehyde may be employed . the injectable solution also liberates bioactive substances with controlled release kinetics from the site of injection .