A polysaccharide derivative as an optical whitening agent

Provided herein are polysaccharide derivatives substituted (a) at a degree of substitution (DS1) of at least 0.05 by a fluo-rescent group (FG) comprising a mono or polycyclic ring system comprising at least one heteroatom selected from N， O and S and conjugated double bonds， and having an absorption band in the UV region of light and an emission band in the visible region of light， and a bonded via a first linker to any one of the native functional groups of the polysaccharide repeating units; and (b) at a degree of substitution (DS2) ) of at least 0.05 by a charged group (CG) bonded via a second linker to any one of the native functional groups of the polysaccharide repeating units. Provided herein are polysaccharide derivatives substituted (a) at a degree of substitution (DS1) of at least 0.05 by a fluo-rescent group (FG) comprising a mono or polycyclic ring system comprising at least one heteroatom selected from N， O and S and conjugated double bonds， and having an absorption band in the UV region of light and an emission band in the visible region of light， and a bonded via a first linker to any one of the native functional groups of the polysaccharide repeating units; and (b) at a degree of substitution (DS2) ) of at least 0.05 by a charged group (CG) bonded via a second linker to any one of the native functional groups of the polysaccharide repeating units.