Potassium dihydrogen phosphate kh2po4

Monoclonal anti-human α-subunit of follicle-stimulating hormone (Mab-FSH) with an affinity constant of 2.8 × 10⁻⁹ M⁻¹, and monoclonal anti-human chorionic gonadotropin (Mab-hCG) with an affinity constant of 4.9 × 10⁻⁹ M⁻¹, were purchased from Medix Biochemica (Kauniainen, Finland). A colloidal solution of Au nanoparticles of diameter 40 nm was purchased from Tanaka Kikinzoku Kogyo K. K. (Tokyo, Japan). Bovine serum albumin (BSA) was purchased from Sigma-Aldrich, (St. Louis, MO, USA). Hydrazine (N₂H₄), disodium hydrogen phosphate (Na₂HPO₄), sodium dihydrogen phosphate (NaH₂PO₄), polyethylene glycol (PEG), and potassium dihydrogen phosphate (KH₂PO₄) were purchased from Wako Pure Chemical Industries (Osaka, Japan). Sodium azide (NaN) was purchased from Nacalai Tesque (Kyoto, Japan). All chemicals used in this work were of analytical grade, and all solutions were prepared using Milli-Q water from Millipore (R ≥ 18. 2 M Ω cm⁻¹).