Abstract: The present invention provides a method for immobilizing a polysaccharide (PS) to a solid surface, said polysaccharide having a keto-carboxy group (—C(?O)—COOH) or a ketal or hemiketal group corresponding thereto, e.g. derived from KDO (2-keto-3-deoxy-D-manno-octonic acid)), the method comprising the steps of: (a) forming a covalent bond between the carboxy group of the polysaccharide and a reporter molecule (RM), thereby forming a polysaccharide-reporter molecule conjugate (PS-RM), said reporter molecule comprising a recognition/substrate site (e.g. biotin or an anthraquinone); and (b) immobilizing the polysaccharide-report molecule conjugate by forming a specific bond (e.g. by photocoupling or formation of an affinity pair) between the recognition/substrate site of said reporter molecule and a reception/reagent site of the solid surface. The present invention also provides a solid surface thus obtainable and the use of such solid surfaces for diagnostic purposes, e.g.