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Supplementary Material
Gene Specific Impedimetric Bacterial DNA Sensor for Rheumatic Heart Disease
Swati Singh1,2 . Ankur Kaushal1 . Sunil Gupta3 . Ashok Kumar1,2()
1
CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi-110007, India
2
Academy of Scientific and Innovative Research (AcSIR), New Delhi, 110025, India
3
National Centre for Disease Control, Sham Nath Marg, Delhi-110054, India
S1: FTIR Studies
The % transmittance of the unmodified gold (Au) electrode was not found to be specific for functional
groups whereas, transmittance of Au-MPA-PAMAM electrode (Fig.S1A) showing peaks at 546 and 662 cm-1
specific for gold-sulphur bond formation due to monolayer attachment of mercaptopropionic acid (MPA) on the
gold working surface [1]. The peak at 732 cm-1 corresponds to NH stretches and peaks at 3480, 3740 and 3872
cm-1 for C-H stretching. The peak at 1410 cm-1 showed for C-O-H and peak at 1558 cm-1 for CO-NH bond
confirming the linkage of PAMAM with MPA via amide bond formation [2]. The FTIR spectrum of Au-MPAPAMAM-ssDNA (Fig.S1 B) showed peaks at 1044, 1182, 638 and 732 cm-1 corresponding to in-plane vibration
of cytosine, C7=N vibration of adenine, C2=O stretch of thymine and C=O stretch of guanine, respectively
confirming the presence of all four nucleotides of DNA. The peaks of Au-MPA-PAMAM-dsDNA (Fig.S1C)
were similar to Au-MPA-PAMAM-ssDNA except few peaks at 1238 and 1044 cm-1 corresponding to phosphate
and deoxyribose backbone, increased in amplitude and more prominent confirming the hybridization of ssGDNA to the probe [2,3].
Fig. S1 FTIR spectra of A) Au-MPA-PAMAM, B) Au-MPA-PAMAM-ssDNA, C) Au-MPA-PAMAMdsDNA at 400- 4000 cm-1.
References
1. Tlili A, Abdelghani A, Hleli S, Areef M (2004) Electrical characterization of a thiol SAM on gold as a first step for
the fabrication of immunosensors based on a quartz crystal microbalance. Sensors 4: 105-114. doi:10.3390/s40670105
2. Singh S, Kaushal A, Khare S, Kumar A (2014) Gold-mercaptopropionic acid-polyethylenimine composite based DNA
sensor for early detection of rheumatic heart disease. Analyst 139:3600-3606. doi: 10.1039/C4AN00324A
3. Marty R, Nsoukpoe-Kossi CN, Charbonneau D, Winert CM, Karepalk L, Tajmir-Riahi HA (2009) Structural analysis
of DNA complexation with cationic lipids. Nucleic Acids Res 37: 849-857. doi: 10.1093/nar/gkn1003