Abstract
A novel competitive host-guest strategy regulated by protein biogate was developed for sensitive and selective analysis of prion protein. The methylene blue (MB)-tagged prion aptamer (MB-Apt) was introduced to the multiwalled carbon nanotubes-β-cyclodextrins (MWCNTs-β-CD) composites-modified glassy carbon (GC) electrode through the host-guest interaction between β-CD and MB. In the absence of prion, MB-Apt could be displaced by ferrocenecarboxylic acid (FCA) due to its stronger binding affinity to β-CD, resulting in a large oxidation peak of FCA. However, in the presence of prion, the specific prion-aptamer interaction drove the formation of protein biogate to seal the cavity of β-CD, which hindered the guest displacement of MB by FCA and resulted in the oxidation peak current of MB (IMB) increased and that of FCA (IFCA) decreased. The developed aptasensor showed good response towards the target (prion protein) with a low detection limit of 160 fM. By changing the specific aptamers, this strategy could be easily extended to detect other proteins, showing promising potential for extensive applications in bioanalysis.
Highlights
Because of the simplicity, fast response, relatively low cost and low power requirement of electrochemical methods[18,19]
Inset: equivalent circuit model for electrochemical impedance measurement system and the nyquist plots of the bare glass carbon (GC) electrode and multiwalled carbon nanotubes (MWCNTs)-β -CD/GC electrode. (E) square wave voltammetry (SWV) curves of the different electrodes. (a) bovine serum albumin (BSA)/methylene blue (MB)-Apt/MWCNTs-β -CD/GC electrode, (b) BSA/ MB-tagged prion aptamer (MB-Apt)/MWCNTs-β -CD/GC electrode incubated with 200 nM prion, (c) BSA/MB-Apt/MWCNTs-β -CD/ GC electrode incubated with 20 μ M ferrocenecarboxylic acid (FCA) without prion, (d) BSA/MB-Apt/MWCNTs-β -CD/GC electrode incubated with 1 pM prion and 20 μ M FCA
The self-assembly of the negatively charged MB-Apt causes a large increase in the Rct value (765 Ω, curve d in Fig. 2D), indicating that MB-Apt is successfully attached to the electrode through the host-guest interaction between β -CD and MB
Summary
Because of the simplicity, fast response, relatively low cost and low power requirement of electrochemical methods[18,19]. The ratiometric electrochemiluminescent assay, based on dual-potential electrochemiluminescence (ECL) measurement, needs to create ECL report units with two emitting states that have the potential-dependent properties upon the substrate concentration, while the ratiometric electrochemical assay needs to choose two redox probes which can be electrochemically oxidized/reduced at different potentials Both of them possess good analytical performances (such as low detection limit, good reliability and reproducibility), which inspires us to construct the ratiometric sensing platform for prion assay. Cyclodextrins (CD) are oligosaccharides composed of six, seven, or eight glucose units (α -, β -, or γ -CD, respectively), which are toroidal in shape with a hydrophobic inner cavity for specific recognition of guest molecules and a hydrophilic exterior to provide water solubility[31,32] Due to their high recognition of guest molecules, good water-solubility, well biocompatibility and environmental friendliness, several electrochemical biosensors have been developed on the basis of host-guest recognition technique to detect biologically relevant analytes in recent years[33,34,35,36,37]. Inset: equivalent circuit model for electrochemical impedance measurement system (the upper left corner) and the nyquist plots of the bare GC electrode and MWCNTs-β -CD/GC electrode (the upper right corner). (E) SWV curves of the different electrodes. (a) BSA/MB-Apt/MWCNTs-β -CD/GC electrode, (b) BSA/ MB-Apt/MWCNTs-β -CD/GC electrode incubated with 200 nM prion, (c) BSA/MB-Apt/MWCNTs-β -CD/ GC electrode incubated with 20 μ M FCA without prion, (d) BSA/MB-Apt/MWCNTs-β -CD/GC electrode incubated with 1 pM prion and 20 μ M FCA
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