A high-performance BaTiO3/Ag/BP-based plasmonic biosensor for label-free detection of cancer biomarkers

Cancer remains a major global health challenge, emphasizing the need for early and accurate detection to improve treatment outcomes and survival rates. Surface plasmon resonance (SPR) biosensors have gained popularity as advanced diagnostic tools, offering label-free and real-time detection with high sensitivity to changes in the refractive index (RI) of biological specimens. In this work, we propose a multilayer SPR biosensor based on a BK₇/BaTiO₃/Ag/black phosphorus (BP) structure, designed using the Kretschmann configuration to enhance performance and biocompatibility. The optical response of the biosensor was first evaluated using the Transfer Matrix Method (TMM) and subsequently compared to Finite-Difference Time-Domain (FDTD) simulations to ensure accuracy and reliability. Optimization results showed that a structure comprising 35 nm of BaTiO₃, 50 nm of Ag, and five BP layers delivers enhanced sensing performance. In practical applications, the biosensor successfully distinguished various cancer cell types based on their unique RI values, with a peak sensitivity of 417.86°/RIU for MCF-7 cells (breast cancer type II). Additionally, the biosensor reached a peak QF of 109.29 RIU⁻¹ and a DA of 2.33, confirming reliable performance. With its strong linearity across a broad RI range (1.335–1.405) and compatibility with standard fabrication techniques, the proposed biosensor offers a scalable, non-invasive solution for early-stage cancer diagnostics and high-throughput clinical screening.