▎ 摘　　要

Electrochemistry: Ultrasensitive detection of cancer biomarker using graphene-modified biosensors A low-cost electrochemical paper-based sensor has been developed for the highly sensitive detection of epidermal growth factor receptor (EGFR). EGFR normally activates relevant genes, resulting in cell division and proliferation, although its overexpression has been observed in some forms of cancer. There is thus a growing interest in determining EGFR levels as a biomarker for early-stage disease diagnosis. A team headed by Xinxia Cai at the Chinese Academy of Sciences, Beijing succeeded in developing a biosensor for EGFR by combining the screen printing of a graphene-modified nanocomposite electrode onto an origami paper-folding for enabling microfluidic reagent and sample processing. The device gave a low detection limit and linear responses across a wide range of EGFR concentrations in human serum (electronic input values). The authors believe that their device can be easily adapted to other soluble biomarkers and that it has potential for use as a handheld instrument as point-of-care testing in early diagnosis and efficacy evaluation of cancer. In this work, an electrochemical paper-based aptasensor was fabricated for label-free and ultrasensitive detection of epidermal growth factor receptor (EGFR) by employing anti-EGFR aptamers as the bio-recognition element. The device used the concept of paper-folding, or origami, to serve as a valve between sample introduction and detection, so reducing sampling volumes and improving operation convenience. Amino-functionalized graphene (NH2-GO)/thionine (THI)/gold particle (AuNP) nanocomposites were used to modify the working electrode not only to generate the electrochemical signals, but also to provide an environment conducive to aptamer immobilization. Electrochemical characterization revealed that the formation of an insulating aptamer-antigen immunocomplex would hinder electron transfer from the sample medium to the working electrode, thus resulting in a lower signal. The experimental results showed that the proposed aptasensor exhibited a linear range from 0.05 to 200 ngmL(-1) (R-2 = 0.989) and a detection limit of 5 pgmL(-1) for EGFR. The analytical reliability of the proposed paper-based aptasensor was further investigated by analyzing serum samples, showing good agreement with the gold-standard enzyme-linked immunosorbent assay.