Janus nanoparticles with asymmetrically subcompartmentalized sensing and amplification modules toward fluorescence detection of microRNA

The design and interfacial engineering of DNA functionalized nanosensors with spatially separated but functionally integrated detection units holds a great promise in optical biosensors. In this study, we developed a bi-component hybrid of Janus nanoquencher particles with immobilized enzymes for fluorescence-based “off-on” detection in solution. Specifically, the hybrids consisting of a mesoporous polydopamine nanoparticle (MPDA) side (∼200 nm) asymmetrically attached with a gold (Au) particle side (∼30 nm) were generated through electrostatic repulsion-controlled growth. By regioselective binding and modification of the exposed side of the particles, fluorescent DNA probes and duplex-specific nuclease (DSN)/T7 exonuclease (T7) were subcompartmentalized on the MPDA and Au side, respectively, to realize substrate recognition and target recycling via the formation and hydrolysis of DNA hybrids. By using microRNAs (miRNAs) as a model target, the developed nanosensor realized a sensitive detection with a low limit of 32 fM (in a linear range from 20 fM–500 fM). Additionally, a high selectivity capable of discriminating a single-base mismatch, as well as a long-term detection stability were realized by the asymmetric interface designs and enzyme immobilization. The methodology is promising in the design and development of DNA probe-loaded hybrid nanosensors.