Fiber-optic SPR cholesterol sensor based on Au film- AuNPs coupling enhancement

Cholesterol is a vital biomolecule in the human body. Abnormal blood cholesterol levels may increase the risk of cardiovascular disease and Alzheimer’s disease. Therefore, there is an urgent need to develop a highly sensitive and rapid method of detecting cholesterol concentration in clinical settings. To meet this demand, we developed a reflective fiber-optic cholesterol sensor based on multimode and single-mode fibers (MMF-SMF). The probe uses AuNPs, synthesised using the sodium citrate reduction method, as a sensitising material, and cholesterol oxidase serves as the sensing membrane. This reflective optical fiber surface plasmon resonance (SPR) biosensor enables the detection of cholesterol concentration with high sensitivity. Experimental results demonstrated that Au film- AuNPs coupling enhances the refractive index sensitivity by 41.3 % to 2243.9 nm/RIU. Cholesterol detection sensitivity increases by 16.02 % to 0.210 nm/nM, and the linear detection range expands from 0–50 nM to 0–70 nM and the detection limit decreases to 4.586 nM. The sensor also exhibits excellent selectivity and stability, and can be used for the detection of cholesterol concentration in real serum samples, offering an efficient solution for developing portable biosensors.