The article describes the development of a hetro-core optical fiber sensor structure based on localized surface plasmon resonance (LSPR) for the detection of cardiac troponin I (cTnI) solution. This was accomplished by fabricating a single-mode fiber - multimode fiber - single-mode fiber (SMS) structure. Then, fiber structure is immobilized with gold nanoparticles (AuNPs) and cerium oxide nanoparticles (CeO2-NPs) to improve its sensing capabilities. An UV-Vis spectrophotometer and a high-resolution transmission electron microscope (HR-TEM) are used to determine the morphology of synthesized nanoparticles. Scanning electron microscopy (SEM) is used to examine the state of immobilized NPs on the surface of sensing region. The developed sensor probe has a linear range of 0 to 1000 ng/mL cTnI, a sensitivity of 3 pm/(ng/mL), and a limit of detection (LoD) of 108.15 ng/mL. In real time, the proposed sensor will be used in a practice to detect acute myocardial infarction (AMI).