Extended-Gate Field-Effect Transistor Consisted of a CD9 Aptamer and MXene for Exosome Detection in Human Serum

Cancer progresses silently to the terminal stage of theimpossibleoperable condition. There are many limitations in the treatment optionsof cancer, but diagnosis in an early stage can improve survival ratesand low recurrence. Exosomes are the biomolecules released from cancercells and are promising candidates for clinical diagnosis. Among them,the cluster of differentiation 9 (CD9) protein is an important exosomalbiomarker that can be used for exosome determination. Therefore, here,a CD9 aptamer was first synthesized and applied to an extended-gatefield-effect transistor (EGFET)-type biosensor containing a disposablesensing membrane to suggest the possibility of detecting exosomesin a clinical environment. Systematically evaluating ligands usingthe exponential enrichment (SELEX) technique was performed to selectnucleic acid sequences that can specifically target the CD9 protein.Exosomes were detected according to the electrical signal changeson a membrane, which is an extended gate using an Au microelectrode.The fabricated biosensor showed a limit of detection (LOD) of 10.64pM for CD9 proteins, and the detection range was determined from 10pM to 1 & mu;M in the buffer. In the case of the clinical test,the LOD and detection ranges of exosomes in human serum samples were6.41 x 10(2) exosomes/mL and 1 x 10(3) to 1 x 10(7) exosomes/mL, respectively, showing highlyreliable results with low error rates. These findings suggest thatthe proposed aptasensor can be a powerful tool for a simple and earlydiagnosis of exosomes.