<p>Plasmonic sensing based on nanostructures offers a highly sensitive and label-free method for detecting biomolecules, making it a promising approach in biomedical research. However, metal-based plasmonic biosensors typically endure limited transmission of signal and substantial optical attenuation in mid-IR, which reduce their sensitivity. To overcome these limitations, we have proposed an optical biosensor utilizing a nanocylindrical hyperbolic metamaterial (HMM) composed of alternating graphene and Al₂O₃ multilayers. Effective medium theory was employed to characterize optical characteristics of metamaterial. Reflectance spectra were analyzed at various conditions to monitor the shifts in the spectral minima. Sensitivity of the sensor and the Figure of Merit (FOM) were quantitatively assessed. Results indicate that biosensor demonstrates excellent sensitivity, which is influenced by factors such as nanocylindrical HMM thickness, refractive index of sensing medium, distance between gold nanograting and nanocylindrical HMM multilayer, incidence angle of the incoming light, and graphene Fermi level. The main innovation of this work lies in the introduction of a hybrid architecture consisting of a graphene/Al₂O₃ hyperbolic metamaterial and an internal gold nanocylinder, which leads to the formation of hybrid resonances due to the simultaneous coupling of metamaterial modes and the metallic nanocylinder’s resonances. This resonant synergy results in intense field localization and a significant enhancement in sensing performance in the mid-infrared region.</p>