Engineering two-in-one DNA nanohybrids to evaluate anti-cancer effects through activatable RNA imaging

The development of DNA-based imaging techniques provides a promising way for theranostic applications. However, the dramatic chemical difference between DNA probes and therapeutics significantly hinders the construction of an ideal theranostic system for evaluation of therapeutic effects via in situ molecular imaging. In this work, we report a simple approach for the construction of a two-in-one DNA nanohybrid via one-step assembly of DNA probes and small molecular drugs, enabling evaluation of therapeutic effects via sensitive imaging of apoptosis-related mRNA. The nanohybrid was self-assembled from a rationally designed molecular beacon (MB) probe, doxorubicin (DOX, a chemotherapeutic drug) and Fe (II) ions through coordination interactions, which possesses anti-cancer effects from chemotherapeutics and the capability of efficient co-delivery of DNA probes without transfection agents. By tracking pro-apoptotic Bax mRNA expression with the MB, this system allows real-time monitoring of cell apoptotic process in response to drug treatment, enabling assessment of therapeutic effects of small molecular drugs. In addition, the approach is extended to the imaging of target microRNA in the drug treatment based on flexible DNA probe design, demonstrating the universality of this strategy. Moreover, the modular design of this DNA nanohybrid allows the introduction of photosensitizers into this system for efficient photodynamic therapy and simultaneous mRNA monitoring. This strategy expands the theranostic toolbox for the in situ evaluation of treatment response and screening anticancer drugs.