Tris 2 carboxyethyl phosphine hydrochloride tcep

All of the DNA sequences were synthesized by Sangon Biological Engineering Technology & Services Co. Inc. (Shanghai, China). The DNA sequences of tetrahedron probe are shown in Table S1 in the Supplementary Materials, which were synthesized based on our previous works [32 (link),33 (link),34 (link)]. The detected DNA in use was as follows:

Target detection (BRCA1): 5′-GAACAAAAGGAAGAAAATC-3′,

Mismatch DNA sequence: 5′-TGCAAGGTGTCAGTATAATCCGACGTTTT-3′.

3,3′,5,5′-tetramethylbenzidine (TMB, H₂O₂ included) was provided by Sigma-Aldrich (St. Louis, Mo, USA). Tris (2-carboxyethyl) phosphine hydrochloride (TCEP) and other chemical reagents were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China).

All the DNA used in this study was purchased from Kangbei Biotechnology Co. Ltd. (Ningbo, China), and sequences of all the designed nucleic acid structures are listed in Additional file 1: Table S1. Tris, polyacrylamide, and agarose were obtained from Sangon Biotechnology Co. Ltd. (Shanghai, China). Chloroauric acid (HAuCl₄), ferric trichloride (FeCl₃), magnesium acetate (MgAC₂), 4-nitrobenzenethiol, Tris (2-carboxyethyl) phosphine hydrochloride (TCEP) and all of the other analytical grade reagents were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). Serum was obtained from Ma’anshan First People's Hospital (Ma’anshan, China).

The DNA oligonucleotides were synthesized by Sangon (Shanghai, China). The sequences are shown in Table S1 in supplementary materials. 3,3′,5,5′-tetramethylbenzidine with hydrogen peroxide (TMB, H₂O₂ included) and SA-HRP were purchased from Sigma-Aldrich (St. Louis, Mo, USA). Bovine serum albumin (BSA), casein, tween-20, tris (2-carboxyethyl) phosphine hydrochloride (TCEP), KCl, NaCl, Na₂HPO₄, KH₂PO₄ and other chemical reagents were all purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). HAuCl₄ and AuNPs solution were purchased from Bailingwei Technology Co., Ltd. (Shanghai, China) and Yuanmai Biological Technology Co., Ltd. (Shanghai, China). PB solution (10 mM, 200 mM, pH = 7.6), PBS solution (100 mM, pH = 7.6), PBST solution (PBS, tween-20 included), TE buffer (10 mM Tris, 1 mM EDTA, pH 8.0) and TM buffer (20 mM Tris, 50 mM MgCl₂, pH 8.0) were all prepared with Milli-Q water (18.2 MΩ·cm resistivity). 16-channel screen-printed electrodes (16-SPE) and the HSBS16x electrochemical workstation were purchased from HuasenXinke (Suzhou) Nanotechnology Co. Ltd. (Suzhou, China) Microscope images were obtained by a Multimode-8 atomic force microscope (AFM), a Nova Nano 450 scanning electron microscope (SEM) and a JEM-1400Plus transmission electron microscope (TEM). Absorption spectra were recorded by an UH5300 ultraviolet-visible (UV-vis) spectrophotometer.