DNA is an ideal candidate to organize matter on the nanoscale, primarily due to the specificity and complexity of DNA based interactions. Recent advances in this direction include the self-assembly of colloidal crystals using DNA grafted particles. I
n this article we theoretically study the self-assembly of DNA-caged particles. These nanoblocks combine DNA grafted particles with more complicated purely DNA based constructs. Geometrically the nanoblock is a sphere (DNA grafted particle) inscribed inside a polyhedron (DNA cage). The faces of the DNA cage are open, and the edges are made from double stranded DNA. The cage vertices are modified DNA junctions. We calculate the equilibriuim yield of self-assembled, tetrahedrally caged particles, and discuss their stability with respect to alternative structures. The experimental feasability of the method is discussed. To conclude we indicate the usefulness of DNA-caged particles as nanoblocks in a hierarchical self-assembly strategy.
In recent years there have been a number of proposals to utilize the specificity of DNA based interactions for potential applications in nanoscience. One interesting direction is the self-assembly of micro- and nanoparticle clusters using DNA scaffol
ds. In this letter we consider a DNA scaffold method to self-assemble clusters of colored particles. Stable clusters of microspheres have recently been produced by an entirely different method. Our DNA based approach self-assembles clusters with additional degrees of freedom associated with particle permutation. We demonstrate that in the non-equilibrium regime of irreversible binding the self-assembly process is experimentally feasible. These color degrees of freedom may allow for more diverse intercluster interactions essential for hierarchical self-assembly of larger structures.
We study theoretically a novel drug delivery system that utilizes the overexpression of certain proteins in cancerous cells for cell specific chemotherapy. The system consists of dendrimers conjugated with keys (ex: folic acid) which key-lock bind to
particular cell membrane proteins (ex: folate receptor). The increased concentration of locks on the surface leads to a longer residence time for the dendrimer and greater incorporation into the cell. Cooperative binding of the nanocomplexes leads to an enhancement of cell specificity. However, both our theory and detailed analysis of in-vitro experiments indicate that the degree of cooperativity is kinetically limited. We demonstrate that cooperativity and hence the specificity to particular cell type can be increased by making the strength of individual bonds weaker, and suggest a particular implementation of this idea. The implications of the work for optimizing the design of drug delivery vehicles are discussed.
