Manganese carbonate superparticles as DNA- and pH-responsive magnetic resonance imaging contrast agents

Manganese carbonate nanoparticles (NPs) have been developed as pH-triggered responsive magnetic resonance imaging (MRI) contrast agents for tumor diagnosis, but the signal amplification of MRI is still limited due to the lack of response to other pathological parameters of tumors. Here, random single-stranded deoxyribonucleic acid (ssDNA) was explored as a biomimetic template to prepare manganese carbonate superparticles (MnCO₃ SPs) assembled from ultrasmall particles. We focused on the degradation ability of DNA-MnCO₃ SPs triggered by DNA and its trigger mechanism. The results show that different sequences of DNA could trigger the disassembly of these DNA-MnCO₃ SPs and result in MR signal amplification. Further investigations show the DNA-MnCO₃ SPs possess good physiological stability, but increased degradation sensitivity under dual triggering of DNA and low pH. In vivo MR and FL dual-modal imaging for tumor region display T₁-signal rapid amplification, suggesting rapid responsiveness of DNA-MnCO₃ SPs to DNA. Therefore, the design of DNA- and pH-triggered DNA-MnCO₃ SPs may provide a new idea for the construction of next-generation activatable contrast agents with high specificity and high sensitivity.