2.1. Materials

Spherical AuNPs with a citric acid coated surface and a size of 5, 60, 80 and 120 nm were purchased from Nanopartz (Loveland, CO, USA). Dulbecco’s modified Eagle’s medium (DMEM) containing 4.5 g/L glucose and 1 g/L glucose for cell culture was obtained from Merck (Darmstadt, Germany) and fetal bovine serum (FBS) was bought from Biowest (Nuaillé, France). Dialysis membranes (molecular weight cut-off = 25,000 and 3500 Da) were purchased from Carl Roth (Karlsruhe, Germany) and sodium hyaluronate (HA; 13 kDa) from Lifecore Biomedicals (Chaska, Minnesota, USA). All other chemicals were purchased from Merck (Darmstadt, Ger-many). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was obtained from PanReac AppliChem (Darmstadt, Germany).