Fluorescence biosensor for the H₅N₁ antibody based on a metal-organic framework platform

Based on the adsorption of a metal-organic framework (MOF) to DNA, a fluorescent biosensor for H₅N₁ antibodies has been developed. In this system, a short oligonucleotide was modified with the fluorescent dye 5'6-FAM (5'6-carboxyfluorescein) as the fluorescent DNA probe. With the introduction of a MOF aqueous solution, the DNA probe can be adsorbed by the MOF and the fluorescence of the dye will be quenched by the MOF. Subsequently, exonuclease I (Exo I) is employed to specifically hydrolyze the DNA probe at the 3'-terminus and the fluorescent dye FAM is released from the MOF, which results in recovery of the fluorescence. If the 3'-ends of the DNA probe are linked to H₅N₁ antigens, which can specifically recognize the H₅N₁ antibody, the hydrolysis of Exo I would be inhibited, so the fluorescence of the system would not recover. The fluorescence is related to the logarithm of the H₅N₁ antibody concentration in the range 1.0 × 10^-6-5.0 × 10^-9 mol L^-1 with a detection limit of 1.6 × 10^-9 mol L^-1 (S/N = 3). The proposed method has been applied to detect the H₅N₁ antibody in serum samples with satisfactory results.