Tuning the density profile of surface-grafted hyaluronan and the effect of counter-ions Ida Berts, Giovanna Fragneto, Jöns Hilborn and Adrian R. Rennie Eur. Phys. J. E, 36 7 (2013) 70 Published online: 16 July 2013 DOI: 10.1140/epje/i2013-13070-7