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.