Polyoxometalate-derived MoS2 nanosheets embedded around iron-hydroxide nanorods as the platform for sensitively determining miRNA-21

A novel nanohybrid of polyoxometalate-derived MoS2 nanosheets (pd-MoS2 NSs) tightly and vertically grown over beta-FeOOH nanomds (NRs) (denoted by pd-MoS2@beta-FeOOH) was prepared and exploited as the platform to immobilize the complementary DNA (cDNA) strands of microRNA-21 (miRNA) for further detection. p-FeOOH nanorods (NRs) were utilized as the template for preparing pd-MoS2 NSs using the solvothermal method. Results revealed that beta-FeOOH NRs were embedded closely by ultrathin pd-MoS2 NSs, thus forming a novel homogeneous nanohybrid. Basic characterizations verified that the pd-MoS2@beta-FeOOH nanohybrid exhibited a multicomponent structure comprising the mixed chemical valences of Mo4+/Mo6+ and Fe-0/Fe2+/Fe3+, abundant oxygen vacancies, and Fe-O bond. Compared with miRNA-21 biosensors based on beta-FeOOH and pd-MoS2 and other previously reported sensing systems, the pd-MoS2@beta-FeOOH-based one had the superior sensing performance toward miRNA-21 with a low limit of detection (LOD) of 0.11 fM. In addition, the proposed biosensor showed high selectivity toward other mismatched DNAs, good stability, excellent reproducibility, and acceptable feasibility. The developed biosensing strategy can also be used to detect other targets when anchoring other kinds of probes and thus shows potential applications in diagnosis with biomarkers.