Determination of vitamin B ₁₂ in blood samples using a SERS aptasensor based on dual-layer core–satellite plasmonic nanostructures

As an essential trace nutrient, vitamin B₁₂ (VB₁₂) plays a crucial role in maintaining normal metabolic processes and physiological functions in the human body, particularly in neurological development, overall growth, and energy metabolism in children. Therefore, the accurate and sensitive determination of VB₁₂ levels in blood is of great significance for monitoring and evaluating children's growth and developmental status. In this study, a surface-enhanced Raman scattering (SERS) aptasensor was designed for ultrasensitive detection of VB₁₂ in blood samples. The VB₁₂ aptamer was modified on the surface of Fe₃O₄@Au nanoparticles (Fe₃O₄@Au NPs) to serve as the capture probe. Meanwhile, complementary DNA (cDNA) was immobilized on the surface of gold nanoparticles (Au NPs) functionalized with the Raman reporter molecule 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB), serving as the signal probe. In this sensor, the VB₁₂ aptamer hybridizes with the cDNA, forming a dual-layer core-satellite plasmonic nanostructure (Fe₃O₄@Au NPs-Apt/Au NPs-DTNB-cDNA). Quantitative detection was achieved by measuring the SERS signal intensity of DTNB at 1033 cm^-1. Based on this design, the developed aptasensor exhibits high sensitivity toward VB₁₂ with a detection limit as low as 0.73 pg mL^-1. Furthermore, the SERS aptasensor demonstrates excellent specificity and stability when applied to the detection of VB₁₂ in blood samples.