A two-dimensional molecular beacon for mRNA-activated intelligent cancer theranostics

Ideal theranostics should possess directly correlated imaging and therapy modalities that could be simultaneously activated in the disease site to generate high imaging contrast and therapeutic efficacy with minimal side effects. However, so far it still remains challenging to engineer all these characteristics into a single theranostic probe. Herein, we report a new type of photosensitizer (PS)-derived "two-dimensional" molecular beacon (TMB) that could be specifically activated within tumor cells to exhibit both high imaging contrast and therapeutic efficacy that outperforms conventional photosensitizers for cancer theranostics. The TMB is constructed by integrating a photosensitizer (chlorin e6 (Ce6)), a quantum dot (QD), and a dark quencher (BHQ3) into a hairpin DNA molecule to generate multiple synergistic FRET modes. The imaging modality and therapy modality, which are mediated by FRET between the QD and BHQ3 and FRET between the QD and Ce6 respectively, are interconnected within the TMB and could be simultaneously activated by tumor mRNA molecules. We show that highly effective cancer imaging and therapy could be achieved for cancer cell lines and xenografted tumor models. The reported TMB represents an unprecedented theranostic platform for intelligent cancer theranostics.