Tetrahedral DNA Nanostructures: A Structural-Family-Aware Review from Computational Design and Biological Stability to Translational Nanomedicine.

DNA has evolved from a carrier of genetic information into a programmable material for constructing nanoscale architectures with precise structural and functional control. Among these systems, tetrahedral DNA nanostructures (TDNs) comprise at least two experimentally distinct structural families: small scaffold-free tetrahedra assembled from a few synthetic oligonucleotides, often termed tetrahedral framework nucleic acids (tFNAs), and larger scaffolded or wireframe tetrahedral DNA-origami objects. This review integrates assembly principles, computational and sequence-level design, physicochemical stability, fabrication, structural validation, biological performance, and translational evidence while keeping these two families analytically separate. For few-strand TDNs, particular attention is given to ionic conditions, pH, temperature, serum and nuclease exposure, cellular uptake, targeting aptamers, and delivery of drugs and regulatory nucleic acids; scaffolded tetrahedral origami is discussed where its routing, mechanics, manufacturing, or larger spatial capacity are directly relevant. Recent in vivo studies provide evidence for tissue distribution, transdermal delivery, and short-term biocompatibility of selected few-strand TDN formulations, but the translational evidence remains predominantly preclinical. Rather than positioning TDNs as universally superior nanocarriers, this review emphasizes architecture-specific evidence, quantitative experimental conditions, and the limits of transferring conclusions between structural families. Progress toward translational nanomedicine will require validated design rules, matched-condition benchmarking, pharmacokinetic and biodistribution studies, scalable manufacturing, standardized quality attributes, and rigorous safety assessment.