Surface plasmon resonance based ultra-sensitive cholesterol detection using AuNPs/MPBA/β-CD functionalized gold-coated tilted fiber Bragg grating

Cholesterol is one of the key indicators in clinical biochemical testing and the diagnosis and treatment for diseases. Here we develop a high-sensitivity cholesterol concentration sensor based on tilted fiber Bragg grating surface plasmon resonance (TFBG-SPR) technology. The sensor excites surface plasmon resonance (SPR) by coating a gold film on the surface of TFBG, and then sequentially assembles gold nanoparticles (AuNPs), 4-mercaptobenzoic acid (MPBA) and β-cyclodextrin (β-CD) on the surface of the gold film through self-assembly technology to realize a cholesterol fiber probe. The high surface area ratio of AuNPs can effectively increase the number of β-CD bound to their surface, thereby increasing the binding sites between β-CD and cholesterol. MPBA can bind with β-CD to form a structure with a conical hydrophobic cavity, which stabilizes hydrophobic molecules such as cholesterol through hydrophobic interactions and non-covalent forces such as van der Waals forces, encapsulating cholesterol to form stable inclusion complexes. The experimental results showed that there is a good linear relationship between the intensity change of SPR resonant peak and the concentration of cholesterol solution. The proposed sensor shows a detection limit of 0.002 fM, which is four orders of magnitude lower than that of the existing similar cholesterol sensor.