Recyclable SERS-Based Immunoassay Guided by Photocatalytic Performance of Fe3O4@TiO2@Au Nanocomposites

Abstract

A novel recyclable surface-enhanced Raman scattering (SERS)-based immunoassay was demonstrated and exhibited extremely high sensitivity toward prostate specific antigen (PSA). The immunoassay, which possessed a sandwich structure, was constructed of multifunctional Fe3O4@TiO2@Au nanocomposites as immune probe and Ag-coated sandpaper as immune substrate. First, by adjusting the density of outside Au seeds on Fe3O4@TiO2 core-shell nanoparticles (NPs), the structure-dependent SERS and photocatalytic performance of the samples was explored by monitoring and degradating 4-mercaptobenzonic acid (4MBA). Afterwards, the SERS enhancement capability of Ag-coated sandpaper with different meshes was investigated, and a limit of detection (LOD), as low as 0.014 mM, was achieved by utilizing the substrate. Subsequently, the recyclable feasibility of PSA detection was approved by zeta potential measurement, absorption spectra, and SEM images and, particularly, more than 80% of SERS intensity still existed after even six cycles of immunoassay. The ultralow LOD of the recyclable immunoassay was finally calculated to be 1.871 pg/mL. Therefore, the recyclable SERS-based immunoassay exhibits good application prospects for diagnosis of cancer in clinical measurements.

Recent development of surface-enhanced Raman scattering for biosensing

“…The diagnostic methods could achieve the simultaneous detection of dual PSA biomarkers within the gray zone between 4.0 and 10.0 ng/mL for clinical samples. Jiang et al constructed an Fe3O4@TiO 2 @Au nanocomposite immunoprobe with a detection limit of 1.871 pg/mL LOD for PSA [ 64 ]. Notably, the SERS immunoprobe can be recycled multiple times due to the excellent catalytic properties of TiO 2 .…”

SERS Immunosensors for Cancer Markers Detection

“…Microparticles with a core of Fe 3 O 4 coated with a layer of TiO 2 and then with Au nanoparticles (Fe 3 O 4 @TiO 2 @Ag microparticles) were investigated as a recyclable substrate for a SERS-based PSA immunoassay [ 68 , 69 ]. It was found that the photocatalytic degradation of the microparticles could be adjusted by tuning the thickness of the middle TiO 2 shell and the density of the Ag nanoparticles at the outer surface, while the magnetic properties of the Fe 3 O 4 core enhanced the photocatalytic activity of the microspheres [ 68 ].…”

“…A LOD of 16.25 pg/mL was claimed, and a linear dynamic range from 0.1 ng/mL to 100 μg/mL [ 68 ]. Microspheres with the same structure have also been employed as labels in a non-competitive PSA immunoassay after their modification with the Raman tag 4-MBA and an anti-PSA antibody [ 69 ]. SiC sandpapers with sputtered Ag films were used as substrates after modification with an anti-PSA antibody.…”

“…SiC sandpapers with sputtered Ag films were used as substrates after modification with an anti-PSA antibody. Through optimization of both the substrate and the labels, a LOD of 1.871 pg/mL was achieved [ 69 ].…”

Si/TiO2/Ag Multistorey Structures with Interfacial Charge Transfer for a Recyclable Surface-Enhanced Raman Scattering Substrate

“…Recently, many researchers have begun to focus on the chemical enhancement mechanism of SERS. − The charge transfer (CT) enhancement related with semiconductor materials is used in these studies. − Because intermolecular interactions can alter the electron density distribution and the Raman scattering cross section, SERS would improve the different Raman vibration modes of probe molecules and detection specificity. − In previous studies, the CT and EM mechanisms were often discussed separately. There has been a lack of effective methodology for combining the two mechanisms into a single-material system to design the most efficient SERS substrate.…”