(Poly)cation-induced protection of conventional and wireframe DNA origami nanostructures

DNA nanostructures hold immense potential to be used for biological and medical applications. However, they are extremely vulnerable towards salt depletion and nucleases, which are common under physiological conditions. In this contribution, we used chitosan and linear polyethyleneimine for coating and long-term stabilization of several three-dimensional DNA origami nanostructures. The impact of the degree of polymerization and the charge density of the polymer together with the N/P charge ratio (ratio of the amines in polycations to the phosphates in DNA) on the stability of encapsulated DNA origami nanostructures in the presence of nucleases and in low-salt media was examined. The polycation shells were compatible with enzyme- and aptamer-based functionalization of the DNA nanostructures. Additionally, we showed that despite being highly vulnerable to salt depletion and nucleolytic digestion, self-assembled DNA nanostructures are stable in cell culture media up to a week. This was contrary to unassembled DNA scaffolds that degraded in one hour, showing that placing DNA strands into a spatially designed configuration crucially affect the structural integrity. The stability of naked DNA nanostructures in cell culture was shown to be mediated by growth media. DNA origami nanostructures kept in growth media were significantly more resistant towards low-salt denaturation, DNase I and serum-mediated digestion than when in a conventional buffer. Moreover, we confirmed that DNA origami nanostructures remain not only structurally intact but also fully functional after exposure to cell media. Agarose gel electrophoresis and negative stain transmission electron microscopy analysis revealed the hybridization of DNA origami nanostructures to their targets in the presence of serum proteins and nucleases. The structural integrity and functionality of DNA nanostructures in physiological fluids validate their use particularly for short-time biological applications in which the shape and structural details of DNA nanodevices are functionally critical.

Temperature-Responsive Smart Nanocarriers for Delivery Of Therapeutic Agents: Applications and Recent Advances

Smart drug delivery systems (DDSs) have attracted the attention of many scientists, as carriers that can be stimulated by changes in environmental parameters such as temperature, pH, light, electromagnetic fields, mechanical forces, etc. These smart nanocarriers can release their cargo on demand when their target is reached and the stimulus is applied. Using the techniques of nanotechnology, these nanocarriers can be tailored to be target-specific, and exhibit delayed or controlled release of drugs. Temperature-responsive nanocarriers are one of most important groups of smart nanoparticles (NPs) that have been investigated during the past decades. Temperature can either act as an external stimulus when heat is applied from the outside, or can be internal when pathological lesions have a naturally elevated termperature. A low critical solution temperature (LCST) is a special feature of some polymeric materials, and most of the temperature-responsive nanocarriers have been designed based on this feature. In this review, we attempt to summarize recent efforts to prepare innovative temperature-responsive nanocarriers and discuss their novel applications.