Electrochemical System Designed on a Paper Platform as a Label-Free Immunosensor for Cancer Derived Exosomes

As a latest mode of cell-cell communication, extracellular vehicles (EVs) play significant roles in intercellular transportation and triggering phenotypic changes in recipient cells via a unique set of RNAs, DNAs and proteins [۱]. EVs are generally described as diverse cell-released membrane fragments [۲], secreted by virtually any cell types including epithelial cells, cancerous cells and leukocytes. They could be detected in all biofluids such as blood, saliva, urine, cerebrospinal fluid, breast milk, and other bodily fluids [۳]. Due to this fact that they can be detected in a variety of body solutions and are reminder of their parent cells, they have a good potential in clinical diagnoses, especially in diagnosis and prognosis of the non-invasive cancer. However, the reliable, cost-effective and fast methods are still needed to their determination. Point-of-care testing (POCT) involves a wide range of diagnostic tools that meet this purpose. Electrochemical paper-based devices (ePADs) have been introduced as simple, inexpensive, portable and disposable measurement devices to be used in many POCT applications, especially in handling emergencies and outpatient as well as remote usages. Electrochemical detection is a real quantitative detection method with better sensitivity, selectivity and detection limits than indirect measurement methods [۴].In the current study, a cost-effective, biodegradable electrochemical device based on a highly flexible chromatographic paper was fabricated. The electrode modification was performed with materials carbon functionalized with multi-carbon nanotubes and gold nanoparticles. An antibody was immobilized on the porous surface of the materials carbon to combine with proteins overexpressed on the exosomal membrane. This structure effectively protects the electron transfer of a redox prop and leads to quantitative detection of exosomes using current changes. The electrochemical measurements were investigated using cyclic voltammetry (CV), differential palls voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) technique. This paper platform had a high sensitivity (a detection limit of ۱۲۵ exosomes/μL and a linear range of ۵× ۱۰۲ to ۱ × ۱۰۶ exosomes/μL) and suitable selectivity for detection of exosomes in the real sample