Metal-Enhanced Fluorescence for Alpha-Fetoprotein Detection and for SERS Using Hybrid Nanoparticles of Magnetic Cluster Core—Plasmonic Shell Composite

Abstract

We demonstrated that the hybrid core–shell nanostructure of Fe3O4 (core) and gold (shell) could be a good substrate candidate both for metal-enhanced fluorescence (MEF) and surface-enhanced Raman spectroscopy (SERS). The magnetic properties of the core material could provide functionalities such as the magnetically induced aggregation/distribution of nanostructures to increase the hot-spot density, while the nano-thickness gold shell allows for the plasmonic enhancement of both fluorescence and SERS. The gold-capped magnetic (Fe3O4) nanoparticles (GMPs) were facilely synthesized using a newly developed chemical method. The relative molar ratio of the constituent materials of the core–shell composite was optimized for tuning the plasmonic resonance wavelengths for MEF and SERS. We employed GMP-based MEF to detect alpha-fetoprotein (AFP), with concentrations ranging from 0.05 to 1000 ng/mL, and obtained a limit of detection (LOD) as low as 3.8 × 10−4 ng/mL. The signal enhancement factor (EF) in the GMP-based MEF was 1.5 at maximum. In addition, the GMPs were used in SERS to detect rhodamine B (RhB). Its LOD was 3.5 × 10−12 M, and the EF was estimated to be about 2 × 108. The hybrid core–shell nanoparticles could find potential applications in diagnostic assays based on MEF and SERS in various fields such as food verification, environmental testing/monitoring, and disease diagnosis.

Review—Quantum Biosensors: Principles and Applications in Medical Diagnostics

“…SERS QBs can be used to detect a wide variety of biomolecules, including proteins, nucleic acids, and viruses. A SERS biosensor has been developed to detect the protein alpha-fetoprotein, 88 which is a biomarker for liver cancer, to detect the DNA of the Zika virus and to detect the SARS-CoV-2 virus, which causes COVID-19. 89 A viable replacement for the present therapeutic drug monitoring methods is continuous drug monitoring, which has the potential to transform our knowledge of pharmacokinetic variability and advance personalized medicine.…”

Emerging Biosensing Methods to Monitor Lung Cancer Biomarkers in Biological Samples: A Comprehensive Review

“…Phuc et al developed a MEF method for the detection of AFP cancer biomarkers using gold-capped magnetic (Fe 3 O 4 ) nanoparticles (GMPs). The nano-thick gold-coated shell on the core improved the sensor’s fluorescence signal in the linear range of AFP protein concentration from 0.05 to 1000 ng/mL, yielding a LOD of 0.38 pg/mL [ 189 ]. Yang et al developed an immunochromatography test strip (ICTS) and homemade test strips to quickly detect AFP in human serum.…”