Ti3C2/Fe3O4 - based surface plasmon resonance imaging biosensor for efficient separation and sensitive detection of CA125 in serum

Abstract

A surface plasmon resonance imaging (SPRi) biosensor is presented which facilitates rapid and sensitive detection of the ovarian cancer biomarker carbohydrate antigens 125 (CA125). The CA125 protein was specifically captured and directly recognized by polyadenylic (polyA)-modified DNA aptamer on the surface of a Au chip. The biosensor demonstrated a linear range of direct detection of CA125 based on SPRi from 20 nM to 0.5 nM, with a detection limit of 0.47 nM. Furthermore, Fe₃O₄ nanoparticles were synthesized in situ on the carboxyl-functionalized two-dimensional (2D) material Ti₃C₂ to obtain MXC/Fe₃O₄ nanocomposites. The large surface area of Ti₃C₂ provides ample binding sites for the in situ generation of Fe₃O₄ and this facilitates subsequent immobilization of DNA aptamers. The amino-modified DNA aptamer interacted with carboxylate sites activated on the surface of Ti₃C₂, and the aptamer was immobilized on the MXC/Fe₃O₄ nanocomposite surface. Due to the magnetic properties of Fe₃O₄ nanoparticles within the composite material, CA125 protein in serum can be effectively captured and separated under an external magnetic field. The captured protein forms a sandwich amplification structure with the DNA adapter on the surface of the Au chip, thereby enhancing the detection signal of CA125. The biosensor demonstrates a linear detection range from 0.5 pM to 1000 pM, with a detection limit as low as 81 fM. The unique separation capability of the composite nanomaterials enables the biosensor to detect CA125 protein as low as 1 pM in complex liquid matrices such as serum, achieving exceptional selectivity, accuracy, and sensitivity in detecting the ovarian cancer marker. This capability significantly supports the early diagnosis of ovarian cancer.

Graphical abstract