Biosensor BS comprising at least one polymer P wherein said polymer P is a copolymer of at least monomer M and at least one ester E of (meth)acrylic acid and polyethylene oxide, wherein said monomer M is different from ester E and has at least one ethylenically unsaturated double bond, wherein polymer P has a surface adsorption SA of at least 200 ng/cm2 on the respective surface where polymer P is deposited, said SA being determined by quartz crystal microbalance.