A zinc(II)-based two-dimensional MOF for sensitive and selective sensing of HIV-1 ds-DNA sequences

Coordination reaction of a known three-dimensional (3D) polymer precursor {Na₃Na₉(Cbdcp)₆(H₂O)₁₈]}_n (A, Cbdcp = N-(4-carboxybenzyl)-(3,5-dicarboxyl)pyridinium) with Zn(NO₃)₂·6H₂O in H₂O or H₂O/DMF at 100 °C and in the presence of aspirin, 5-fluorouracil (5-FU) as modulators, trans-1,2-bis(4-pyridyl)ethylene (bpe) or 1,2-bis(4-pyridyl)ethane (bpea) as ancillary ligands afforded six novel Zn(II)-based metal-organic frameworks (MOFs), that is, {Zn(Cbdcp)(H₂O)₃]·H₂O}_n (1, 1D zigzag chain), {Zn(HCbdcp)₂]·H₂O}_n (2, 2D sheet), {Zn(Cbdcp)(bpe)_1/2]·2H₂O}_n (3, 3D polymer), {Zn(Cbdcp)(bpe)_1/2]·2H₂O}_n (4, 2D network), {Zn(Cbdcp)(bpea)_1/2]·2H₂O}_n (5, 3D polymer) and {Zn(Cbdcp)(bpea)_1/2]·2H₂O}_n (6, 2D network). Among them, compound 2 contains aromatic rings, positively charged pyridinium, Zn²⁺ cation centers and carboxylic acid groups lined up on the 2D sheet structure with a certain extended surface exposure. The unique structure of 2 facilitates effective association with carboxyfluorescein (FAM) labeled probe single stranded DNA (probe ss-DNA, delineates as P-DNA) to yield a P-DNA@2 system, and leads to fluorescence quenching of FAM via a photoinduced electron transfer process. The P-DNA@2 system is effective and reliable for the detection of human immunodeficiency virus 1 ds-DNA (HIV ds-DNA) sequences and capable of distinguishing complementary HIV ds-DNA from mismatched target sequences with the detection limit as low as 10 pM (S/N = 3).