chloride) (PDADMA, Mw = 200000–350000
g/mol, 20 wt % solution),
poly(styrenesulfonate sodium salt) (PSS, Mw = 500000 g/mol), and linear polyethylenimine (LPEI, Mw = 25000 g/mol) were purchased from Sigma-Aldrich, Scientific
Polymer Products, and Polysciences, Inc., respectively. Sodium chloride
(NaCl), 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPhPA),
pure ethanol (≥99.5% ACS reagent), and urea were purchased
from Sigma-Aldrich. Sodium 4-styrenesulfonate (SSNa) (98% HPLC) was
purchased from AK Scientific. 4,4′-Azobis(4-cyanovaleric acid)
(V-501) was purchased from FUJIFILM Wako Pure Chemical Corporation.
Silicon dioxide-coated QSensors (QSX 303 SiO2) were used
as substrates and were purchased from Biolin Scientific. Dialysis
tubing with a molecular weight cutoff (MWCO) of 3.5 kDa was purchased
from VWR. Milli-Q water with a resistivity of 18.2 MΩ·cm
was used for all experiments.