Conjugate of polyethylene glycol and chitosan

PEG-chitosan conjugates comprising chitosan and polyethylene glycol moieties or derivatives thereof which are bonded together and their use in medicine is described. In one embodiment, the conjugate comprises a chitosan moiety or a derivative thereof and a polyethylene glycol moiety or a derivative thereof
which are bonded together via the amino function on the chitosan by the use of an activated chitosan species. In another embodiment, the conjugate comprises a chitosan moiety or a derivative thereof and a polyethylene glycol moiety or a derivative thereof which are bonded together, the chitosan portion
of the conjugate having a molecular weight in the range of from 10 kilodaltons to 1000 kilodaltons.