Dual-functional Fe3O4@SiO2@Ag triple core-shell microparticles as an effective SERS platform for adipokines detection

A novel SERS-based immunoassay for adipokines in patient's serum dependent on dual-functional Fe3O4@SiO2@Ag triple core-shell microparticles (TCSMPs) was developed. The construction and morphology of the Fe3O4@SiO2@Ag TCSMPs were investigated by XRD, SEM, and TEM. Particularly, the size and quantity of Ag NPs and its density on the surface of SiO2 shell can be controlled by adjusting the concentration of AgNO3 in the precursor solution. Consequently, the highest SERS activity of Fe3O4@SiO2@Ag TCSMPs can be obtained by choosing the sample with the proper coating density of Ag NPs. Meanwhile, the Fe3O4 core endowed the TCSMPs with superior magnetic nature, which enabled their convenient separation. With the two crucial features, the Fe3O4@SiO2@Ag TCSMPs were eventually applied in the SERS-based immunoassay for adiponectin and leptin in PBS solution and patient's serum, respectively. The detection linear ranges of adiponectin and leptin in PBS solution were from 25 mu g mL(-1) to 25 pg mL(-1) and 200 mu g mL(-1) to 20 pg mL(-1) with the detection limits as low as 25 and 20 pg mL(-1), respectively. More significantly, the trace adiponectin (0.934 ng mL(-1)) and leptin (2.636 pg mL(-1)) in obesity patient's serum, which had been diluted by three orders of magnitude, were successfully detected using such an immunoassay. Therefore, this method has an enormous potential for accurately testing clinical obesity and diabetes.