Re-entrant melting as a design principle for DNA-coated colloids.

Colloids functionalized with DNA hold great promise as building blocks for complex self-assembling structures. However, the practical use of DNA-coated colloids (DNACCs) has been limited by the narrowness of the temperature window where the target structures are both thermodynamically stable and kinetically accessible. Here we propose a strategy to design DNACCs, whereby the colloidal suspensions crystallize on cooling and then melt on further cooling. In a phase diagram with such a re-entrant melting, kinetic trapping of the system in non-target structures should be strongly suppressed. We present model calculations and simulations that show that real DNA sequences exist that should bestow this unusual phase behaviour on suitably functionalized colloidal suspensions. We present our results for binary systems, but the concepts that we develop apply to multicomponent systems and should therefore open the way towards the design of truly complex self-assembling colloidal structures.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Achieving Selective Targeting Using Engineered Nanomaterials

The development of Drug Delivery Systems (DDS) able to selectively deliver a controlled amount of a drug only to diseased cells would represent a dramatic development in nanomedicine. One of the multiple challenges still paving the way towards this goal is the elaboration of strategies that would allow targeting with extreme accuracy specific cells, as cancerous cells, among a large variety of closely related ones. In this work, we review the most recent nanotechnology applications aiming at controlling the selectivity of the interaction of delivery nanosystems with cells, with a focus on multivalent targeting. We briefly review thermodynamic models of multivalent interactions and highlight the challenges that still need to be addressed to transfer theoretical design principles into practical applications. In particular, suitable experimental systems based on multivalent models often require the control of the nanocarrier characteristics at the molecular level. Traditional delivery methods, however, fail to provide such degree of control. DNA nanotechnology is a growing field of nanoscience that has witnessed impressive developments in the past decades and has led to major advances in the fabrication of nanostructures and self-assembled systems. Relying on the possibility of controlling their molecular interactions by sequence design, nucleic acids can serve the drug delivery program by providing desired nanostructures with nearly atomic precision. In combination with the recent achievements in the research on DNA aptamers, short nucleic acid sequences isolated to interact selectively with a specific target, DNA nanotechnology is undoubtedly one of the most promising tools for the development of selective DDS.info:eu-repo/semantics/publishe