Highly sensitive cholesterol detection using electrophoretic deposition of silica-coated gold nanoparticles to enhance the FRET effect

We report a sensitive detection method that employs silica‑coated gold nanoparticles (Au@SiO₂) to enhance Förster resonance energy transfer (FRET) between fluorescence molecules rhodamine green (RG) and rhodamine B (RB), which has been applied to the detection of cholesterol as a proof-of-concept study. Excitation spectroscopy and time-resolved fluorescence decay analyses revealed that the presence of Au@SiO₂ enhanced the excitation of RB, shortened the donor’s fluorescence lifetime, facilitated the energy transfer process, and increased both the FRET efficiency and rate. In this process, uniformly sized Au@SiO₂ nanoparticles are synthesized using a one-pot method, with their localized surface plasmon resonance (LSPR) peak matching the excitation peak of RB. An enhancement substrate is fabricated by immobilization of these nanoparticles on an ITO slide using an optimized electrophoretic deposition method, followed by surface amination with aminopropyl silane. RG-modified carboxymethyl-β-cyclodextrin (CR) is employed as the cholesterol recognition unit, which is subsequently linked with the amino-functionalized Au@SiO₂ nanoparticles through an amide bonding reaction. RB was employed as the FRET acceptor, and cholesterol is detected by recording the fluorescence of CR, achieving a detection limit of 8.0 pmol/L, and the system also demonstrates reusable performance.