Lossy mode resonance sensors based on nanocoated multimode-coreless-multimode fibre

•Lossy mode resonances can be generated with a multimode coreless multimode fiber.•Spectral, SEM and refractive index sensitivity characterization was performed.•The maximum sensitivity attained with this structure approaches 10000 nm/RIU.•A biosensor for anti-IgGs was fabricated, which could detect from 1 to 40 mgr/L.