Articles, compositions, kits, and methods relating to nanostructures, including synthetic nanostructures, are provided. Certain embodiments described herein include structures having a core-shell type arrangement; for instance, a nanostructure core may be surrounded by a shell including a material, such as a lipid bilayer, and may include other components such as oligonucleotides. In some embodiments, the structures, when introduced into a subject, can be used to deliver nucleic acids and/or can regulate gene expression. Accordingly, the structures described herein may be used to diagnose, prevent, treat or manage certain diseases or bodily conditions. In some cases, the structures are both a therapeutic agent and a diagnostic agent.