Dual SERS enhancement based on Ag@Au Nanopizza combined with superhydrophobic silicon substrate for the detection of early bladder cancer marker-APOA1

Currently, clinical detection of early bladder cancer (BC) biomarkers suffers from insufficient specificity and sensitivity. In this study, a novel triangular nanostructure with protrusions on the surface shaped like a pizza was prepared. It combined with a superhydrophobic Si substrate to achieve trace and ultra-sensitive Surface-enhanced Raman spectroscopy (SERS) detection of APOA1, a urinary biomarker for early BC. Firstly, we precisely controlled the number and spacing of gold protrusions on the surface of Ag@Au Nanopizza to achieve an enhancement factor (EF) of 3.86 × 10⁷ for Ag@Au Nanopizza. In addition, we prepared substrates with superhydrophobic properties by functionalized modification using PS microsphere films as substrate. The enrichment of nanoparticles on the superhydrophobic Si substrate achieves a secondary enhancement of its SERS performance (EF = 5.73 × 10⁷), while also attenuating the coffee-ring effect and improving the homogeneity of the substrate performance. The double SERS enhanced strategy was successfully applied to detect early BC biomarker APOA1. In a wide range (100 fg/mL-100 ng/mL), we achieved quantitative detection of APOA1 with a limit of detection (LOD) of 52 fg/mL. This provides an ultrasensitive, specific, and non-invasive diagnostic strategy for the early diagnosis of BC.