Mirror-Image L-DNA Nanocubes for Stable and Targeted Multimodal Drug Delivery

Nucleic acid nanostructures provide programmable architectures for molecular delivery but remain limited by rapid nuclease degradation, poor in vivo persistence and inefficient intracellular cargo release. Here we report a mirror-image L-DNA nanocube as a biologically persistent and modular therapeutic delivery platform. The nanocube self-assembles from synthetic L-DNA oligonucleotides into a structurally defined architecture that exhibits substantially enhanced resistance to enzymatic degradation and prolonged stability under physiological conditions compared with the corresponding D-DNA nanostructure. Surface functionalization with folic acid enables selective tumour targeting in vitro and in vivo. The L-DNA nanocube supports the delivery of chemically distinct therapeutic cargos, including doxorubicin, a bortezomib prodrug and MCL1-targeting small interfering RNA (siRNA). In tumour-bearing mice, L-DNA nanocube-mediated delivery improves therapeutic efficacy while reducing systemic toxicity relative to free drug and D-DNA nanocube controls. For siRNA delivery, we engineer a pH-responsive release mechanism that promotes endosomal escape and cytosolic cargo localization, as visualized by cryo-electron tomography, resulting in efficient gene silencing. Together, these results establish mirror-image nucleic acid nanostructures as a class of biologically functional nanomaterials for programmable intracellular therapeutic delivery.