A colorimetric aptamer biosensor based on cationic polythiophene derivative as peroxidase mimetics for the ultrasensitive detection of thrombin

Abstract

A colorimetric assay for the ultrasensitive determination of thrombin was presented, in which the cationic polythiophene derivative was used as catalyst of the 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 reaction and the thrombin-binding aptamer (TBA) was used as inducing polymer's different conformation elements. It was found the cationic polythiophene derivative, poly[3-(3′-N,N,N-triethylamino-1′-propyloxy)-4-methyl-2,5-t-hiophene hydrochloride] (PMNT), can catalyze the oxidation reaction of TMB in the presence of H2O2 to produce a blue color solution. The catalytic activity of PMNT on the TMB–H2O2 reaction was closely relevant to the conformation of PMNT. The absorbance of TMB–H2O2 was distinctly increased in the presence of TBA. With the addition of thrombin, TBA interacted with thrombin to form a G-quadruplex structure. The conformational change weakened the catalytic activity of PMNT and resulted in a decrease in the absorbance. The colorimetric sensor could detect thrombin down to 4pM with high selectivity against other interfering proteins. This work is not only of importance for a better understanding of the unique properties of cationic polythiophenes derivative but also have great potential for medical diagnostics and therapy for human health.