Improved sensitivity for ratiometric fluorescence detection of ricin based on “kinetic competition” aptasensing strategy

Abstract

The aptamer recognition mechanisms have been well developed based on equilibration between aptamer conformations modulated by ligand, and can be compatible with almost all kinds of readout techniques for aptamer-based biosensors (i.e., aptasensors). A novel and robust aptasensing strategy named “kinetic competition” has also been investigated in which the blocker kinetically competes the aptamer and probe DNA (e.g., molecular beacon). It improved general methodology for developing aptasensors because it does not require a lengthy pre-equilibration, but the pre-binding of target and its aptamer alters kinetic competition for transducing signal. However, some disadvantages still limited its practical applications, such as high background signal, low sensitivity and accuracy in complex matrices and so on. Herein, we firstly reported the ratiometric “kinetic competition” aptasensor for ricin A chain (RTA) detection. It can well avoid false positive results and minimize background signals, which achieves more sensitive, accurate, reliable and effective detection. Under optimal conditions, this strategy effectively improved the sensitivity and reduced the background signal. A limit of detection (LOD) of 0.23 nM for RTA could be achieved without any separation and amplification techniques. The recovery data (73.8 %–111.0 %) was also satisfactory for RTA analysis in food powder samples and serum matrix.