A biosensor based on surface plasmon resonance (SPR) with triangular indentations is proposed to detect and identify five types of cancer cells, exhibiting refractive indices ranging from $1.368$ to $1.401$. This advanced biosensor features a multi-layer architecture comprising BK$7$/Ag/TiO$_2$/Al$_2$O$_3$ grating and operates within the optical telecommunication band (OTB) ($1260$-$1625$ nm). To enhance the biosensor’s performance, HeLa cells are employed as reference cells, and various parameters—including the angle of light incidence, the thickness of the Ag and TiO$_2$ layers, and grating specifications—are systematically analyzed to design a sensor with maximum sensitivity. The sensitivities achieved for the HeLa, Jurkat, PC-$12$, MDA-MB-$231$, and MCF-$7$ cells are $9208.33$, $9714.28$, $10857.14$, $11785.71$, and $12214.28$ nm/RIU, respectively. Furthermore, the highest values for the sensor’s figure of merit (FoM) and quality factor (QF) are determined to be $122.14$/RIU and $14.53$. The highest FoM is recorded for MCF-$7$ cell detection, while the maximum QF is observed for HeLa cell detection. Analysis of the electric field distribution under resonant conditions reveals that the sensor exhibits a strong electric field with a penetration depth of 500 nm. A comparative analysis of the proposed sensor against previous designs indicates a substantial enhancement in various performance parameters, including sensitivity, FoM, and QF.
