Sub-attomolar electrochemical measurement of DNA hybridization based on the detection of high coverage biobarcode latex labels at PNA-modified screen printed electrodes

Publication date: 15 May 2017
Source:Talanta, Volume 167
Author(s): Tarina Widaningrum, Endrika Widyastuti, Feby Wijaya Pratiwi, Ai Imas Faidoh Fatimah, Patsamon Rijiravanich, Mithran Somasundrum, Werasak Surareungchai
We have constructed biobarcode labels based on 468nm diameter latex spheres. Modification with polyallylamine and then glutaraldehyde was used to attach a high DNA loading, consisting of aminated probe DNA (approx. 1.01×10² molecules per sphere) and biobarcode DNA (approx. 1.66×10⁴ molecules per sphere). Detection of the biobarcodes was performed by application of a Ag enhancer solution, causing association of the Ag⁺ ions with the phosphate groups of the DNA. The deposited Ag was detected by differential pulse voltammetry. A 30 mer sequence from the BL21 strain of E. coli was detected with an LOD of 2.6fM (calibration range 10 aM to 0.1pM, r²=0.91, n=45). The LOD was lowered to 0.56aM (calibration range 100zM to 0.1nM, r²=0.991, n=50) by utilizing a sandwich assay with PNA-modified screen printed electrodes, which lowered the Ag background current. The sandwich assay platform was used to calibrate E. coli strain BL2(DE3) with an LOD of 17.0 CFU mL⁻¹ (calibration range 10 to 10⁶ CFU mL⁻¹, r²=0.99, n=33) with good discrimination against Salmonella.

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