Vwr symphony ph meter

Dispersions were prepared based on a protocol recently developed by the authors^{16 (link)}. Sonication was performed in deionized water (DI H₂O) using the critical dispersion sonication energy (DSE_cr), which was determined as previously described for each ENM^{16 (link)}. ENMs were dispersed at 5 mg cm⁻³ in 3 ml of solute in 15 ml conical polyethylene tubes using a Branson Sonifier S-450A (Branson Ultrasonics, Danbury, CT, USA), calibrated by the calorimetric calibration method previously described^{16 (link),26 (link)}, whereby the power delivered to the sample was determined to be 1.75 W, fitted with a 3 inch cup horn (maximum power output of 400 W at 60 Hz, continuous mode, output level 3) in which tubes were immersed so that sample and cup water menisci were aligned. Stock DI H₂O suspensions were then diluted to final concentrations in either RPMI or F12K cell culture media, each either alone or supplemented with 10% heat inactivated fetal bovine serum (FBS), and vortexed for 30 seconds. Dispersions were analyzed for hydrodynamic diameter (d_H), polydispersity index (PdI), zeta potential (ζ), and specific conductance (σ) by DLS using a Zetasizer Nano-ZS (Malvern Instruments, Worcestershire, UK). pH was measured using a VWR sympHony pH meter (VWR International, Radnor, PA, USA).