Tris 2 carboxyethyl phosphine hydrochloride tcep

All the DNAs were provided by Shanghai Sangon Biotechnology (Shanghai, China); a thrombin aptamer (TBA 15) was used as a “nanoclaw” and integrated into the input strands Ca and Cb. Thrombin (TB) and 6-mercaptohexanol (MCH) were purchased from Sigma Aldrich (USA). Tris (2-carboxyethyl) phosphine hydrochloride (TCEP) was purchased from Bio Basic Inc (Markham Ontario, Canada). K₃Fe[CN]₆ and K₄Fe[CN]₆ were obtained from Xilong Chemical Co. Ltd. (Guangdong, China). NMM (N-methyl mesoporphyrin IX, a kind of porphyrin dye that could generate an enhanced fluorescence signal after binding with G-quadruplex) was provided by J&K (Beijing, China). Tris–HCl S-buffer (20 mM Tris, 100 mM NaCl, 5 mM TCEP, pH 7.4) was used to dissolve SH-DNA. Tris–HCl M-buffer (20 mM Tris, 2 mM MCH, pH 7.4) was applied to block the electrode and decrease nonspecific adsorption. Tris–HCl W-buffer (5 mM Tris, pH 7.4) acted as the washing buffer. Other DNAs were dissolved with 1× HEPES buffer (25 mM HEPES, 10 mM KCl, 100 mM NaCl, pH 7.4). Distilled water was purified using a Millipore system.

Gold tetrachloroauric acid [HAuCl4.3H2O] and iodine [I₂] were purchased from Sigma Aldrich. Sodium phosphate monobasic [NaH₂PO₄], sodium phosphate dibasic [Na₂HPO₄], SDS [C₁₂H₂₅OSO₃Na], potassium iodide [KI], with molecular biology grade, were purchased from Acros. Tris (2-carboxyethyl) phosphine hydrochloride (TCEP) [C₉H₁₅O₆P.HCl] was supplied by Bio Basic (USA). Tri-sodium citrate dihydrate [Na3C6H5O7.2H₂O], sodium chloride [NaCl], and Potassium chloride [KCl] were obtained from Merck. Milli-Q water was used in preparation of all the solutions. All glasswares were cleaned with freshly prepared Aqua regia cleaning solution [HCl–HNO3 (3:1)], rinsed with water and finally were oven-dried before using them.
The buffer solutions used for conjugation of DNAi and Au-NPs were prepared as follows: salting buffer (2 M of NaCl in 10 mM of phosphate buffer saline (PBS), pH 7.4), phosphate adjustment buffer (100 mM, pH 7).
The DNAi oligonucleotides as described by Tolcher et al49 (link) were provided by Reza Sheikhnejad. DNAi has the sequence of 5′-CACGCACGCGCATCCCCGCCCGTG-3′. The non-specific oligonucleotides purchased from Macrogen Company, South Korea, and the sequence is 5′-GCCATATACAATAACAAGGC-3′. MCF-7 cells were purchased from Iranian Biological Resource Center. Medical ethics committee of Tarbiat Modares University approved cell experiments.