Abstract: We describe the preparation of multibranched gold-silica -molecularly imprinted polymer (bAu@mSiO2@MIP) core-shell nanoparticles, with their specific ability to recognize enrofloxacin (ENRO), and their application as label-free nanosensors for the specific detection of the antimicrobial by surface-enhanced Raman scattering. The use of these nanocomposites results in a large enhancement of the Raman scattering of ENRO upon binding of an antibiotic to the selective recognition sites in the MIP. These are in the proximity of the gold core branches that act as intrinsic hot spots providing highly localized and strongly enhanced electromagnetic fields caused by plasmon resonance. The effect of the multibranched morphology of the gold cores (bAu) on the optical spectroscopic response of the bAu@mSiO2@MIP nanosensors is investigated with the aim of improving ENRO detection. The optimized nanostructures allowed us to achieve a detection limit of 1.5 nM for ENRO, which is 2 orders of magnitude lower than those for previously reported Au@MIP nanosensors, additionally providing negligible cross-reactivity toward other potential interfering species.

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