Chloroauric acid haucl4 aq

AuNRs were prepared following the seed-mediated method [37 (link)]. The seed solution was prepared by the addition of ice-cold sodium borohydride (NaBH₄) (10 mM, 0.3 mL, Sigma-Aldrich) to a solution of hexadecyltrimethylammonium bromide (CTAB) (0.1 M, 5 mL, Sigma-Aldrich) containing chloroauric acid (HAuCl₄.aq) (0.25 mM, Sigma-Aldrich). The solution was stirred for 2 min and then kept at 25 °C for 8 min. The growth solution was prepared by the sequential addition of silver nitrate (AgNO₃) (5 mM, 3.2 mL), HAuCl₄· × H₂O (50 mM, 2 mL) and ascorbic acid (0.1 M, 1.5 mL, Sigma-Aldrich) to a CTAB solution (0.1 M, 200 mL, Sigma-Aldrich), mixing gently after each step. Finally, the seed solution was kept at 28 °C for 2 h and then centrifuged twice at 9000g (20 min) to purify the AuNRs.

Aniline (ACS reagent, ≥99.5%), chloroauric acid (HAuCl₄.aq), potassium ferricyanide (K₃[Fe(CN)₆]), potassium ferrocyanide (K₄[Fe(CN)₆].3H₂O), sulfuric acid (98%, H₂SO₄), sodium acetate (C₂H₃NaO₂), and sodium metaperiodate (NaIO₄) were purchased from Sigma Aldrich and were used without further purification. The Fe(CN)₆^3−/4− redox probe was prepared using a solution of 0.1 M phosphate buffer saline (PBS) containing a mixture of 5 mM potassium ferro/ferricyanide. 0.1 M PBS was prepared by mixing 0.1 M sodium phosphate dibasic (Na₂HPO₄), 0.1 M sodium dihydrogen phosphate (NaH₂PO₄) and 0.1 M potassium (KCl) stock solutions with the pH adjusted at 7. Commercial screen-printing carbon paste (C-1011-6) was obtained from Advanced Electronic Materials Inc., Taiwan. Mouse monoclonal anti-human serum albumin antibody (Ab-HSA), native human serum albumin (HSA), native actin protein and bovine serum albumin (BSA) were purchased from Abcam. The J82 bladder cancer cell line was obtained from the Bioresource Collection and Research Center (BCRC), Hsinchu, Taiwan. The cells were cultured in McCoy’s 5A medium (GIBCO, Thermo Fisher Scientific) followed by lysing and harvesting using a protein extraction buffer (GE Healthcare). The original protein concentration in the obtained lysate was determined using a Bio-Rad DC protein assay kit.