A new water soluble cellulose derivative 6-O-(2,3-bis(thiosulfato)propyl-oxy-2-hydroxy-propyl)-cellulose (TSHP) was synthesized by addition of tetrathionate to 6-O-(allyl-oxy-2-hydroxy-propyl)-cellulose (AHP). On gold surfaces, TSHP forms dense monolayers by chemisorption with a mean thickness of 4 +/- 1 nm. These monolayers were investigated by means of null-ellipsometry, AFM, FTIR-ERS, X-ray photoelectron spectroscopy and contact angle measurements. Based on the XPS results, it was proposed that the thiosulfato groups attached to the cellulose chains are homolytically cleaved and the resulting thio radicals bind covalently to the gold substrate. The formation of gold thiolates leads to a stable TSHP monolayer on the gold surface. The interaction between the TSHP films and fibrinogen and bovine serum albumin was also studied. The experimental results showed that the non-specific adsorption of these proteins was significantly reduced by the coverage of gold surfaces with TSHP.