Electrochemical detection of Mycobacterium tuberculosis IS6110 gene fragments based on the gold nanocrystals with uniform morphology and highly exposed high-index facets and target DNA-induced recycling amplification

Abstract

This paper reports the synthesis of gold nanocrystals via the reduction of chloroauric acid using ascorbic acid in the mixed hexadecyltrimethylammonium chloride aqueous solution with potassium bromide and potassium iodide. The resulting gold nanocrystals have trioctahedral nanostructures with uniform morphology and highly exposed high-index facets. The nanocrystals unique structure promotes enhanced chemical activity and catalytic activity. Preparation of the electrochemical sensing platform for IS6110 gene involves the modification of gold nanocrystals on hairpin DNA 2 (H2) and thionine as the redox probe for target DNA-induced signal amplification. Target DNA (IS6110 gene) hybridizes with hairpin DNA 1 (H1) pre-modified on the gold electrode, which opens the hairpin structure of H1. This can hybridize with H2 to release target DNA, which is used in the next recycle. The utilization of target DNA-induced recycling allows one target DNA to transport many redox probes to the electrode surface promoting significant signal amplification. The detection signal is further enhanced by catalyzed redox reaction of thionine with gold nanocrystals. The differential pulse voltammetric signal increases with increasing concentration of target DNA in the range of 0.1-1.0 × 105 fM with detection limit of 0.031 fM. The method provides ultrahigh sensitivity, specificity and stability and was successfully applied in the detection of tuberculosis in human blood.