Mitochondria-Targeted Polymeric Liposomes for Pre-miRNA Imaging and Gene Therapy

Mitochondria-related microRNAs (miRNAs) play a pivotal role in regulating mitochondrial functions, making accurate imaging and precise modulation of these miRNAs essential for enhancing their clinical potential in diagnosing and treating various diseases. However, accurate delivery of nucleic acid probes and control regulation of functional action toward miRNAs in mitochondrial compartments remain significant challenges. Hence, we proposed pH-responsive liposomes capable of targeting mitochondria for the efficient delivery of nucleic acid probes for pre-miRNA-34a imaging and miRNA-34a gene therapy. The liposome, R@DA-TPP-SA, composed of TPP-SA, lecithin, cholesterol, and pH-responsive DA-modified PEG-b-PLys through self-assembly, simultaneously encapsulated DNA probes and small interfering RNA (siRNA). Upon internalization in A549 cancer cells, hairpin DNA strands were released in an acidic intracellular environment, triggering a hybridization chain reaction (HCR) in the presence of pre-miRNA-34a. This resulted in a substantial fluorescence signal increase, facilitating cancer diagnosis and real-time monitoring of cargo delivery. Meanwhile, a portion of R@DA-TPP-SA escaped from lysosomes and further enabled the targeted delivery of siRNA-34a to mitochondria due to the specific recognition of triphenylphosphine (TPP), which suppressed the expression level of its target mRNA/protein, disrupted mitochondrial membrane potential, and induced mitochondrial dysfunction, ultimately leading to the apoptosis of cancer cells. Both in vitro and in vivo experiments confirmed the liposomes' anticancer performance with good biocompatibility and low toxicity. By addressing the unmet need for precise delivery and functional manipulation of miRNAs, this work sets the stage for broader applications in the diagnosis and treatment of mitochondrial dysfunction-associated diseases.