Contractile Hairpin DNA-Mediated Dual-Mode Strategy for Simultaneous Quantification of Lactoferrin and Iron Ion by Surface-Enhanced Raman Scattering and Fluorescence Analysis

DNA-mediated self-assembly technology with good sensitivity and affinity ability has been rapidly developed in the field of probe sensing. The efficient and accurate quantification of lactoferrin (Lac) and iron ions (Fe³⁺) in human serum and milk samples by the probe sensing method can provide useful clues for human health and early diagnosis of anemia. In this paper, contractile hairpin DNA-mediated dual-mode probes of Fe₃O₄/Ag-ZIF8/graphitic quantum dot (Fe₃O₄/Ag-ZIF8/GQD) NPs were prepared to realize the simultaneous quantification of Lac by surface-enhanced Raman scattering (SERS) and Fe³⁺ by fluorescence (FL). In the presence of targets, these dual-mode probes would be triggered by the recognition of aptamer and release GQDs to produce FL response. Meanwhile, the complementary DNA began to shrink and form a new hairpin structure on the surface of Fe₃O₄/Ag, which produced hot spots and generated a good SERS response. Thus, the proposed dual-mode analytical strategy possessed excellent selectivity, sensitivity, and accuracy due to the dual-mode switchable signals from "off" to "on" in SERS mode and from "on" to "off" in FL mode. Under the optimized conditions, a good linear range was obtained in the range of 0.5-100.0 μg/L for Lac and 0.01-5.0 μmol/L for Fe³⁺ and with detection limits of 0.14 μg/L and 3.8 nmol/L, respectively. Finally, the contractile hairpin DNA-mediated SERS-FL dual-mode probes were successfully applied in the simultaneous quantification of iron ion and Lac in human serum and milk samples.