Construction of dual-signal electrochemical sensors based on the coordination chemical reaction of Fe2+ and K3[Fe(CN)6] for detecting Brucella vaccine and wild strains

A dual-signal strategy was developed based on a coordination reaction between iron(II) ions (Fe 2+ ) and potassium hexacyanoferrate(III) (K 3 [Fe(CN) 6 ]) to distinguish between brucella vaccine and wild strain. Utilizing metal-organic frameworks (MOFs), MOF Al (aluminum) @Fe 2+ @P 1 and MOF Fe @P 2 were synthesized and affixed to a hyaluronic acid (HA)-doped electrode. Hairpin probe 1 (P 1 ) has a common sequence (P 1 ') recognizing a fragment (T 1 ) in vaccines and wild strains. In contrast, hairpin probe 2 (P 2 ) has a differential sequence (P 2 ') only targeting a specific fragment (T 2 ) in the wild strain. Experimental findings indicated that activation of T 1 led to the dissociation of P 1 from MOF Al @Fe 2+ @P 1 , which released Fe 2+ into a buffer containing trace Fe 2+ . Following this, the addition of hydrogen peroxide (H 2 O 2 ) and K 3 [Fe(CN) 6 ] resulted in the formation of KFe[Fe(CN) 6 ] (PB). In contrast, specific activation of T 2 caused the detachment of P 2 from MOF Fe , thereby exposing its catalytic site. In H 2 O 2 , this catalytic site facilitated the conversion of trace Fe 2+ in buffer to Fe 3+ , with no PB generated after the addition of K 3 [Fe(CN) 6 ]. Simultaneous activation of T 1 and T 2 promoted the oxidation of Fe 2+ released from MOF Al by the exposed catalytic site of MOF Fe . The ratio of K 3 [Fe(CN) 6 ] to PB exhibited dynamic changes. Specifically, the ratio below 2.37 ± 0.05 indicated a Brucella-positive sample, whereas a ratio under 0.9 ± 0.02 suggested a sample derived from the vaccine. The scarcity of dual-signal sensors employing coordination reactions underscores the significance of this approach. Moreover, it addressed the challenges associated with brucella detection, demonstrating robust analytical performance.