Ultrasensitive IgG quantification using DNA nano-pyramids
Liang Yuan1,3, Marcella Giovanni1,3, Jianping Xie1, Chunhai Fan2, David Tai Leong1*
1Department of Chemical and Biomolecular Engineering, National University of Singapore. 4 Engineering Drive 4, Singapore 117585, Singapore
2Division of Physical Biology, and Bioimaging Center, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
3 Both authors contributed equally.
*Corresponding author (D.T.L)
Table S1. Synthetic Oligonucleotide Probes
Name / SequencePyra-A / 5'-COOH-TTTTTTTTTT ACA TTC CTA AGT CTG AAA CAT TAC AGC TTG CTA CAC GAG AAG AGC CGC CAT AGT A-3’ (65 bases)
Pyra -B / 5'-HS-C6- TAT CAC CAG GCA GTT GAC AGT GTA GCA AGC TGT AAT AGA TGC GAG GGT CCA ATA C -3' (55 bases)
Pyra -C / 5'-HS-C6- TCA ACT GCC TGG TGA TAA AAC GAC ACT ACG TGG GAA TCT ACT ATG GCG GCT CTT C -3' (55 bases)
Pyra -D / 5'-HS-C6- TTC AGA CTT AGG AAT GTG CTT CCC ACG TAG TGT CGT TTG TAT TGG ACC CTC GCA T -3' (55 bases)
Pyra-Free / 5'-ACA TTC CTA AGT CTG AAA CAT TAC AGC TTG CTA CAC GAG AAG AGC CGC CAT AGT A-3’ (55 bases)
Figure S1 X-Ray Photoelectron Spectroscopy analysis of as-synthesized (a) FeC, (b) anti-IgG, and (c)ferrocene-labeled anti-IgG (FeC-Ab2).
FigureS2Nyquist diagrams and the illustration of each step in the preparation process of the DNA nano-pyramid-based immunosensor. From Electrochemical Impedance Spectra (EIS) measurement, the high frequency region of the impedance plot shows a semicircle pattern depicted signals of the redox-probe [Fe(CN)6]3-/4-. The diameter of the semicircle represents the electron transfer resistance (Ret) which corresponded to the ease of electron transfer between the redox probe and the electrode surface. Inset: the equivalent circuit.
FigureS3Decreased impedance after ferrocene incorporation. Nyquist diagrams of (a) Au-DP-Ab1-Ag-(Fc-Ab2) and (b) Au-DP-Ab1-Ag-Ab2 in PBS 10 (pH 7.4) containing 5mM Fe(CN)63-/Fe(CN)64- and 0.1M KCl.
FigureS4The DNA nano-pyramid based immunosensor showed a diffusion-controlled nature of redox species in the electrochemical process. Cyclic voltammograms of Au-DP-Ab1-Ag-(Fc-Ab2) electrode in PBS 10 (pH 7.4) with a change of the scan rate from 50 to 500 mV s-1. Inset: the relationship between the cathodic and anodic peak currents and the scan rate.
FigureS5DNA nano-pyramid based immunosensor showed high selectivity and signal transduction with IgG but not with other proteins. Other proteins do not appear to interfere significantly with the detection of IgG. The SWV response curves of the DNA pyramid-based immunosensing system after being exposed to different proteins in PBS 1 (pH 7.4). Concentration of each protein is 1 ng ml-1.
FigureS6 Effect of coupling efficiency by turning the ration of DNA pyramids and carboxyl-free DNA pyramids. The SWV response curves of the DNA pyramid-based immunosensor with different DNA pyramids diluted with carboxyl-free DNA pyramids, the ratio of DP: f-DP were (a) 1:0, (b) 1:1, (c) 1:2, (d) 1:5, (e) 1:10, (f) 1:20 and (g) 0:1.
FigureS7Optimized pH, incubation time and working temperature of the DNA nano-pyramid immunosensor. Dependence of SWV peak currents on (A) pH of PBS 1, (B) incubation time and (C) incubation temperature. The concentration of IgG was 1 ng mL-1.