In recent years there has been widespread interest in the development of intelligent polymer-based materials for biomedical applications. Materials assembled from polyelectrolytes, including DNA, are drawing increasing interest in the fields of drug delivery, diagnostics and sensing. This presentation will focus on the programmable assembly of oligonucleotides onto planar and colloidal surfaces to prepare nanostructured DNA films and capsules. Engineering oligonucleotides with specific sequences allows site-specific, programmable hybridization of films and capsules with tailored composition, structure and function. The permeability of the DNA capsules will be analyzed using a novel technique based on DNA molecular beacons, allowing the first rapid, real-time and label-free measurement of thin DNA films. A new method for the encapsulation of oligonucleotides within biodegradable polymer capsules for potential drug delivery applications will also be presented. This involves encapsulation of DNA within semipermeable capsules by adsorption of DNA onto amine-functionalized silica particles, followed by polymer multilayer formation, and removal of the sacrificial silica particles. Several types of DNA have been encapsulated within microcapsules, including plasmid, linear double-stranded DNA, and short oligonucleotides. DNA that was encapsulated and subsequently released was active in enzymatic reactions. Further, to demonstrate the utility of capsules for targeted delivery, the specific binding of antigen-functionalized capsules to colorectal cancer cells will be highlighted. These studies are aimed at designing advanced, nanoengineered particles for targeted therapy and diagnostics.