Spectralon baseline

UV-Vis absorption studies were performed using a Nicolet Evolution 300 UV-Vis spectrophotometer (Thermo Electron Corporation, Madison, WI, USA). Diffuse reflectance UV-Vis (DR UV-Vis) spectra were acquired using a Praying Mantis accessory (Harrick Scientific Products, Inc., Pleasantville, NY, USA) and a Spectralon^® baseline. Over the course of 12 weeks, pH values were obtained using a Mettler Toledo Seven Easy pH meter equipped with a Mettler Toledo InLab^® Routine Pro pH probe (Mettler Toledo, Columbus, OH, USA). Dilutions for pH tests were prepared using ultrapure water to make 11.1% w/v solutions at room temperature. Viscosity was analyzed using a Fungilab Viscolead Pro rotational viscometer (Fungilab, Barcelona, Spain). Viscosity measurements were obtained for S-nitrosated and non-nitrosated, hyaluronic acid-free samples using spindles L4 Fungilab at 60 revolutions per min (rpm) and L3 Fungilab at 12 rpm, respectively. The sample temperature was controlled with a water bath and maintained at 25 °C.