A portable smartphone detection of ctDNA using MnB2 nanozyme and paper-based analytical device

The development of point-of-care testing (POCT) for circulating tumor DNA (ctDNA) is meaningful for the noninvasive cancers screening and diagnosis, particularly in resource-limited settings. The microfluidic paper-based analytical device (mu PAD) provides an ideal platform, its application in ctDNA assays remains underexplored. In this work, a multifunctional mu PAD was manufactured, which can enhance the efficiency and reduce the cost of ctDNA sensing. Additionally, a smartphone-based application analysis was fabricated for convenient, portable detection and colorimetric signal readout. Moreover, the novel oxidase-like MnB2 nanozyme was introduced in the sandwiches sensing strategy, utilizing its catalytic properties to effectively generate a colorimetric signal. The use of MnB2 nanozyme in sensing application is relatively novel, and its catalytic performance and mechanism was thoroughly evaluated via experiment and density functional theory (DFT) calculations. After optimizing the detection conditions, the proposed biosensor exhibited satisfactory results. Furthermore, the method was successfully used to detect ctDNA in tumor cell lysates and peripheral blood samples from tumor-bearing mice. The results were consistent with standard qPCR method, affirming the reliability of our POCT analysis device in ctDNA detection. Thus, this work not only provides a paper-based POCT device and intelligent analysis tool for portable cancers diagnosis, but it also paves a new application path for MnB2 nanozyme in the sensing filed.