A Target Responsive Metal Organic Framework Derived Bimetallic Apta-Switch for Reagentless Molecular Recognition

By integrating iron-cobalt squarate bimetallic metal-organic framework (Fe-Co-SqBMoF) based smart material (SM) with functional DNA (fDNA), we designed a target responsive fDNA@Fe-Co-SqBMoF bioelectrode that exhibits recognition induced switchable response to serve as a reagentless single step electrochemical apta-switch (REA). The construct takes advantage of fDNA ability to bind and concentrate target on the receptor interface, while Fe-Co-SqBMoF@SM multifeatures to serve as an immobilization matrix and a signal generating electrochemical switch. Fe-Co-SqBMoF was introduced to prepare a redox active pencil graphite electrode (PGE), while fDNA (aptamer) was decorated on the receptor PGE to impart specificity and selectivity. The Fe-Co-SqBMoF synthesis was characterized through X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy, dynamic light scattering (DLS), and UV-visible (UV-vis) analysis, while each step of fDNA decoration and bioelectrode fabrication was characterized via field emission scanning electron microscopy (FE-SEM), static water contact angle measurements, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). To explore the potential application of the fDNA@Fe-Co-SqBMoF bioelectrode, we designed a REA for detection of aflatoxin B1 (AFB1) which permitted the detection of AFB1 in the linear range 0.7-1000 pg/mL with an LOD of 0.54 pg. The practical applicability of an fDNA@Fe-Co-SqBMoF based REA was demonstrated in milk and water samples.