Circulating microRNAs (miRNAs) are effective cancer biomarkers that are highly stable in body fluids enabling noninvasive detection. Portable, low-cost and efficient biosensing systems is crucial for early on-site diagnosis, especially in resource-limited settings. Present work deals with the development of a smartphone-based biosensing system for electrochemical detection of circulating microRNA-21 (miR-21) biomarker in saliva as a proof-of-concept. The smartphone-based biosensing system composed of a disposable screen-printed biosensor modified with reduced graphene oxide/gold (rGO/Au) composite, a circuit board for detection and a Bluetooth-enabled smartphone equipped with specially designed Android application. The hybridization between miR-21 target and ssDNA probe on the rGO/Au-modified electrode resulted in the decrease in peak current with increase in miR-21 target concentration. The smartphone-based biosensing system showed comparable performance with commercial electrochemical workstation, for miR-21 detection in the concentration range of 1 × 10^-4 M to 1 × 10^-12 M with correlation coefficient (r²) of 0.99. In addition to good selectivity in discriminating mismatched and non-target sequences, the biosensing system also showed acceptable recovery rate ranging from 96.2% to 107.2% in spiked artificial saliva. The smartphone-based biosensing system is envisioned to be able to realize rapid and highly sensitive detection of circulating miRNA biomarker in body fluid for point-of-care testing in remote areas.

循环微RNA（miRNA）是有效的癌症生物标记物，在体液中高度稳定，可进行无创检测。便携式，低成本和高效的生物传感系统对于早期现场诊断至关重要，尤其是在资源有限的环境中。目前的工作涉及基于智能手机的生物传感系统的开发，以对唾液中循环的microRNA-21（miR-21）生物标志物进行电化学检测，以此作为概念验证。基于智能手机的生物传感系统，包括用减少的氧化石墨烯/金（rGO / Au）复合材料改性的一次性丝网印刷生物传感器，用于检测的电路板和配备了特别设计的Android应用程序的蓝牙智能手机。miR-21靶标和ssDNA探针在rGO / Au修饰电极上的杂交导致峰值电流随miR-21靶标浓度的增加而降低。基于智能手机的生物传感系统表现出与商用电化学工作站相当的性能，可在1×10的浓度范围内进行miR-21检测^-4 M至1×10 ^-12 M，相关系数（r ²）为0.99。除了在区分错配序列和非靶序列方面具有良好的选择性外，该生物传感系统还显示出在加标人工唾液中可接受的回收率为96.2％至107.2％。设想基于智能手机的生物传感系统能够实现对体液中循环miRNA生物标志物的快速，高度灵敏的检测，以在偏远地区进行即时点检测。