Ultrasensitive Label-Free Biosensor for Triglyceride Detection Based on Exposed-Core Optical Fiber

Accurate detection of triglycerides (TGs) is important for the prevention and monitoring of dyslipidemia and for understanding the mechanisms of metabolic diseases. In this article, an ultrasensitive label-free sensor for measuring TGs based on an exposed-core optical fiber is presented. The sensor head was formed by splicing a single-mode optical fiber, a multimode optical fiber, and an exposed-core fiber in a Mach–Zehnder interferometer configuration. The Mach–Zehnder interference (MZI) occurs between the exposed core of the fiber, which is only micrometer in size, and the external environment. This allows the light path to pass directly through the liquid sample, resulting in an ultrahigh refractive index sensitivity of 13300 nm/RIU in the refractive index range of 1.331–1.332. In addition, lipase is immobilized on the optical fiber sensor to measure the concentration of TGs by detecting the change in the refractive index of the sample solution caused by the hydrolysis of TGs by lipase. The results showed that this sensor can specifically detect the concentration of TGs with a sensitivity of 1.72 nm/nM and a detection limit of 35 pM. It has the potential to revolutionize the diagnosis and monitoring of TGs and thus impact the prevention and treatment of dyslipidemia and other metabolic diseases.