The nitric oxide donor composition of the present invention comprises a chitosan polymer and a nitric oxide [N2O2 ???] dimer, said composition having the general formula: wherein R1 is an organic group having from about 1 to about 18 carbon atoms, x is from about 0.5 to about 0.8, y is from about 0.2 to about 0.5 and x and y are the mole fractions of each unit and the sum of x and y is 1.