Electrochemical system designed on a paper platform as a label-free immunosensor for cancer derived exosomes based on a mesoporous carbon foam- ternary nanocomposite

Mesoporous carbon as a new class of three-dimensional conductive carbon materials has attracted more attention due to its significant surface area, unique flexibility, and lots of porosity. In this paper, a cost-effective, biodegradable electrochemical sensor was fabricated based on a highly flexible chromatographic paper with a lab-made carbon ink. The electrochemical response was enhanced with mesoporous carbon functionalized with multi-carbon nanotubes and gold nanoparticles ([email protected]/MWCNTs). Then, the CD9 antibodies were immobilized on the porous surface of the nanocomposite to combine with proteins overexpressed on the exosomal membrane. This structure and electrostatic repulsion effectively protect the electron transfer of the redox probe and lead to quantitative detection of exosomes using changes in the current. This paper-based immunosensor revealed a high sensitivity (the very low detection limit of 70 exosomes/µL and a linear range of 1 × 102 to 1 × 107 exosomes/µL) and suitable selectivity for detection of exosomes in the plasma sample. This paper-based immunosensor can prepare a clear horizon for using this kind of biosensors in the early detection and screening of diseases such as cancers in miniaturization and accessible system, especially Point of Care Testing (POCT) devices.