Self-Assembled DNA–Protein Hybrid Nanospheres: Biocompatible Nano-Drug-Carriers for Targeted Cancer Therapy

We developed hybrid nanospheres comprised of two of the most important biomolecules in nature, DNA and proteins, which have excellent biocompatibility, high drug payload capacity, in vivo imaging ability, and in vitro/in vivo cancer targeting capability. The synthesis can be done in a facile one-pot assembly system that includes three steps: step-growth polymerization of two DNA oligomers, addition of streptavidin to assemble spherical hybrid nanostructures, and functionalization of hybrid nanospheres with biotinylated aptamers. To test the feasibility of cancer targeting and drug-loading capacity of the hybrid nanospheres, MUC1-specific aptamers (MA3) were conjugated to nanosphere surfaces (apt-nanospheres), and doxorubicin (Dox) was loaded into nanospheres by DNA intercalation. The successful construction of nanospheres and apt-nanospheres was confirmed by agarose gel electrophoresis and dynamic light scattering (DLS). Their uniform spherical morphology was confirmed by transmission electron microscopy (TEM). Fluorescence spectra of nanospheres demonstrated high Dox-loading capability and slow-release characteristics. In vitro MUC1-specific binding of the apt-nanospheres was confirmed by flow cytometry and confocal microscopy. Dox-loaded apt-nanospheres significantly increased cytotoxicity of the MUC1-positive cancer cells due to aptamer-mediated selective internalization, as shown via cell viability assays. Apt-nanospheres could also be imaged in vivo through the synthesis of hybrid nanospheres using fluorescent dye-conjugated DNA strands. Finally, in vivo specific targeting ability of apt-nanospheres was confirmed in a MUC1-positive 4T1 tumor-bearing mouse model, whereas apt-nanospheres did not cause any sign of systemic toxicity in normal mice. Taken together, our self-assembled DNA-streptavidin hybrid nanospheres show promise as a biocompatible cancer targeting material for contemporary nanomedical technology.