Fluorescent sensing of pyrophosphate anion in synovial fluid based on DNA-attached magnetic nanoparticles

• Fe3O4 NPs as an efficient fluorescence quencher for F*-ssDNA was proposed.
• A new fluorescent method for sensitive detection of pyrophosphate anion in the synovial fluid was developed.
• The sensing relies on the competitive coordination interaction of Fe3O4 NPs between PPi and F*-ssDNA.
• The protocol exhibits excellent selectivity for PPi over other phosphate-containing compounds.
• The system is simple in design and convenient in operation.

In this work, a new fluorescent method for sensitive detection of pyrophosphate anion (P2O74−, PPi) in the synovial fluid was developed using fluorophore labeled single-stranded DNA-attached Fe3O4 NPs. The sensing approach is based on the strong affinity of PPi to Fe3O4 NPs and highly efficient fluorescent quenching ability of Fe3O4 NPs for fluorophore labeled single-stranded DNA. In the presence of PPi, the fluorescence would enhance dramatically due to desorption of fluorophore labeled single-stranded DNA from the surface of Fe3O4 NPs, which allowed the analysis of PPi in a very simple manner. The proposed sensing system allows for the sensitive determination of PPi in the range of 2.0×10−7–4×10−6 M with a detection limit of 76 nM. Importantly, the protocol exhibits excellent selectivity for the determination of PPi over other phosphate-containing compounds. The method was successfully applied to the determination of PPi in the synovial fluid, which suggests our proposed method has great potential for diagnostic purposes.