Assembly of bioconjugated rod-nanotags and multilayer plasmonic nanorod-array for ultrasensitive SERS detection of S. aureus bacteria

A highly-efficient bioconjugation protocol of bimetallic rod-nanotags interacted with bacterial anti-S. aureus-IgG has been firstly demonstrated. Controllable fabrication of multilayer plasmonic nanorod-array (MPNRA) can be successfully obtained by facet functionalization of nanorods stacked on an activated Si/SiO₂ chip. Vancomycin coating of MPNRA is favorable to immobilize S. aureus bacteria via multiple hydrogen bonding interactions, i.e., peptidoglycan of the bacterial cell and carbonyl/amine groups of the vancomycin. Moreover, the bimetallic rod-nanotags can be assembled around MPNRA via a bacterial biointerface. Ultrasensitive SERS detection of S. aureus bacteria with limit-of-detection (LOD) can be achieved up to 17.8 cfu/mL via combination of rod-nanotag and multilayer plasmonic nanorod-array perpendicular a chip (MPNRA-perpendicular substrate), which could be ascribed to dual plasmonic enhancement from bioconjugated rod-nanotags aggregates and large-scaled plasmonic nanorod-array.