Molecularly imprinted polymer-coated gold iron nanoparticles for the sensitive detection of ketamine via surface-enhanced Raman spectroscopy

The broad application of drug detection using the surface-enhanced Raman spectroscopy (SERS) technique is limited because of the complexity of human body fluid systems. In this study, molecularly imprinted polymer (MIP)-coated AuFe nanoparticles (AuFe@MIPs) with a 19.9 ± 0.3-nm polymer shell and a 100.3 ± 1.4-nm AuFe core were prepared by applying the ketamine molecule as a template. AuFe nanoparticles were fabricated via pulsed laser ablation in solutions. By systematically evaluating sorption kinetics, isotherms, and thermodynamics, ketamine could be captured by AuFe@MIPs with fast kinetics (20.0 min), efficient maximum sorption capacity (209.9 mg/g at T 298 K and pH 7.0), excellent selectivity against the interference of coexisting drugs, and favorable recycling usage (16.9% decline of pristine capacity after six cycles). Moreover, ketamine could be efficiently detected with a SERS enhancement factor of 1.24 × 10 3 from deionized water (100 ppb) and human urine (500 ppb) by applying AuFe@MIPs as the SERS substrate. The detection presented an excellent spatial uniformity of a typical peak at 1001 cm −1 (8.4% relative standard deviation for 50 measurements of the same substrate batch and 5.3% relative standard deviation for 50 batches of SERS substrate). This study provided a valuable reference to combine laser-ablated magnetic-plasmonic nanoparticles (NPs) with drug-template MIPs for selective capture and effective SERS detection of drugs.