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The incorporation of nanotechnology into electrochemical sensing has transformed the field of biosensors. Developing smart electroactive heterostructure of 10% Fe-doped CeO2 (Fe0.1Ce0.9O2) and laboratory-prepared buckypaper from multiwalled carbon nanotubes (MWCNs) (L-BP) has resulted in considerable advances in electrochemical aptasensing assays. This heterostructure, when combined with aptamers, acts as redox-active switches that enable the detection and quantification of biomolecular recognition events. The unique redox properties of the Fe0.1Ce0.9O2-L-BPs heterostructure, coupled with the conformational changes of the aptamers upon conjugation, were carefully considered when designing surface-based switchable aptasensing platforms. Moreover, the redox properties of the Fe0.1Ce0.9O2-L-BP heterostructure at the surface changed upon incubation with the aptamer and target analyte, which enabled rapid and highly sensitive detection and measurement of biomolecular interactions. Physical and electrochemical evidences indicated that the Fe0.1Ce0.9O2-L-BP heterostructure aptaswitch developed for the aptasensing detection of ochratoxin A (OTA), could detect concentrations as low as 0.08 nM within the dynamic linear range of 0.1–120 nM. Importantly, this assay does not require any nucleotide modification of the heterostructured particles’ surface, demonstrating a novel approach and new route for electrochemical sensing based on aptamer recognition.

Thrombin plays a crucial role in regulating normal hemostatic function and various internal body processes but is rarely detected in vivo because anticoagulant substances in the blood can quickly neutralize it after early-stage coagulation. In this article, we designed a novel perovskite semiconductor Ba $_{{0}.{5}}$ Sr $_{{0}.{5}}$ FeO $_{{3}-\delta }$ by a one-step hydrothermal method as a sensing platform maintaining electroactive characteristics that can be used to conjugate the bio-recognition of aptamers and auto-probing of binding events for highly sensitive thrombin detection. In particular, the introduction of 10% Sb-dopant into Ba $_{{0}.{5}}$ Sr $_{{0}.{5}}$ FeO $_{{3}-\delta }$ semiconductor to tune the energy band structure for fast transport of charged species. Further, the synthesized Ba $_{{0}.{5}}$ Sr $_{{0}.{5}}$ SbxFe1.0-xO3-δ ( ${x}={0}$ –0.1) materials are physically characterized via XRD, FE-SEM, HR-TEM assisted by EDS, XPS, UV-Vis, and UPS. Moreover, aptamer plays a key role in amplifying the electrical signal, where the prepared BaSrSb $_{{0}.{1}}$ Fe $_{{0}.{9}} 0_{{3}-{\delta }}$ particles show dispersion and aggregation upon binding with aptamers and target analyte thrombin, respectively, thereby increasing the sensitivity of the aptasensor. The electrostatic forces are responsible for making it complex between aptamers and particles, while conformational changes in aptamers pursue biomolecular binding of aptamer with thrombin. Accordingly, the electrochemical aptasensor for thrombin detection shows an impressive low limit-of-detection (LOD) of 0.02 pM in a dynamic linear range (0.05 pM–0.3 nM). The proposed electrochemical aptasensor does not require special labeling of oligonucleotides or particle surface decoration.