SERS and fluorescence dual-mode sensing strategy based on competitive host-guest interaction for cholesterol and amantadine detection

Cholesterol is currently most detected by enzyme immunoassay, which is expensive and complicated. Therefore, it is necessary to develop new simple and effective non-enzymatic methods for cholesterol detection. Cholesterol and amantadine have small Raman cross sections and low affinity for metal surfaces, seriously limiting direct and effective SERS detection. Based on competitive interactions between target substances and R6G in β-cyclodextrin (β-CDs) cavities on the surface of cyclodextrin functionalized silver nanoparticles (Ag-β-CDs), a sensor was designed for detecting cholesterol and amantadine by surface enhanced Raman spectroscopy (SERS) and fluorescence (FL) dual modes. R6G entered hydrophobic cavities of Ag-β-CDs through hydrophobic interaction to form host-guest inclusion complexes resulting in fluorescence quenching, adding competitive guest cholesterol or amantadine that bound more strongly to cyclodextrins replaced R6G and recovered its fluorescence. Meanwhile, Ag-β-CDs were also used as SERS substrates. One cholesterol forms more stable inclusion complexes with two Ag-β-CDs nanoparticles, causing some degree of Ag-β-CDs aggregation and generating hot spots to enhance SERS signals of free R6G; Spatial structure of amantadine and extremely strong binding to β-CDs made it bind to only one β-CD, competing out R6G molecules to keep them away from electromagnetic-enhanced regions, and SERS signals weakened. In addition, the dual-mode sensing strategy was successfully applied to detect cholesterol and amantadine in real samples, and the two sets of data obtained complemented and verified each other with the advantages of high accuracy and sensitivity, which has great application prospects in disease surveillance and drug control.