Polyethyleneimine mediated interaction for highly sensitive, magnetically assisted detection of tetracycline hydrochloride

Abstract

Antibiotic residues in food have become the focus of attention. In this work, we report a simple self-assembly method to fabricate magnetic Fe3O4@PEI@Ag complex substrate for surface enhanced Raman scattering (SERS) detection of tetracycline hydrochloride (TC), a widely used antibiotics in breeding industry. Assembled Ag nanoparticles (AgNPs) on Fe3O4 NPs helps form more SERS hotspots by magnetic induction, which facilitate the direct aqueous detection and high sensitivity (EF = 4.0 × 106 in wet state) of the Fe3O4@PEI@Ag sensor. Polyethyleneimine (PEI) not only acts as interlayer for AgNPs assembly on Fe3O4 particles, but can also direct the interaction between TC and SERS substrate. The binding ratio between B, C, D rings of TC and PEI is calculated to be 1:4 by Ultraviolet–visible spectroscopy (UV–vis) characterization. Simulation study also confirms the multiple TC-PEI interaction mode (hydrogen, σ-π, cation-π). Fe3O4@PEI@Ag sensor also shows very high stability (signal decreases < 5% after 93 days). Fe3O4@PEI@Ag SERS sensing array could have a great potential for real-time sensitive detection of analytes. More importantly, this rational adjustment of interaction sites between substrate and analyte is expected to be a new strategy for the improvement of SERS detection sensitivity and selectivity.