Local　surface　plasmon　resonance　(LSPR)　biosensors　find　widespread　applications　in　biomedical　engineering,　environmental　monitoring,　and　food　safety　owing　to　their　non-destructive　and　rapid　detection　capabilities.　However,　the　sensitivity　of　LSPR　sensor　is　constrained　by　their　broad　spectral　response.　This　study　introduces　a　tunable　Fano　resonance　biosensor　leverages　the　coupling　of　LSPR　and　Rayleigh　Anomaly　(RA).　The　refractive　index　sensitivity　of　the　sensor　was　evaluated　through　measurements　of　glucose/water　solutions　at　various　concentrations,　demonstrating　a　refractive　index　sensitivity　of　685　nm/RIU.　Furthermore,　the　sensor　chip　functionalized　with　IgG　antibodies,　enables　label-free　detection　of　IgG　antigens　and　real-time　monitoring　of　biological　reactions　dynamics.　The　sensor　chip　exhibits　a　detection　limit　of　40　ng/mL.　This　straightforward　and　highly　sensitive　biosensor　chip　holds　promise　for　applications　in　immunoassays,　clinical　diagnostics,　and　drug　screening　in　the　future.　　©　2025　IEEE.