A facile fluorescence method for versatile biomolecular detection based on pristine α-Fe₂O₃ nanoparticle-induced fluorescence quenching

This work investigated the interactions of α-Fe2O3 nanoparticles (NPs) with different structural nucleic acids and their fluorescence quenching ability towards fluorophore-labelled nucleic acid probes. Different from bulk α-Fe2O3 samples, nanoscale α-Fe2O3 particles exhibit the unique properties of strong adsorption and fluorescence quenching to fluorophore-labelled single-stranded DNA (ssDNA) probes. Based on these findings, a facile fluorescence method was developed for versatile quantification of nucleic acids. The size scale of NPs makes a significant impact on this sensing platform. Better selectivity was given by bigger NP (50-100 nm)-based nucleic acid-sensing platform compared with smaller NP (30 nm)-based one. In the 50-100 nm α-Fe2O3 NP-based sensing platform, single nucleotide mismatch or single base-pair mismatch can even be effectively discriminated. The targets of micro-RNA (miRNA), ssDNA and double-stranded DNA (dsDNA) are sensitively detected with detection limits of 0.8 nM, 1.1 nM and 0.64 nM (S/N=3), respectively. Significantly, α-Fe2O3 NPs possess different affinities towards ssDNA probes with different lengths, and can be used as a universal quencher for ssDNA probes labelled with different fluorescent dyes. On the basis of these properties, the pristine α-Fe2O3 NPs hold the potential to be widely utilized in the development of novel biosensors with signal amplification or simultaneous multiple target detection strategies.