DNA-nanoparticle assemblies go organic: macroscopic polymeric materials with nanosized features

Abstract

Background: One of the goals in the field of structural DNA nanotechnology is the use of DNA to build up 2- and 3-D nanostructures. The research in this field is motivated by the remarkable structural features of DNA as well as by its unique and reversible recognition properties. Nucleic acids can be used alone as the skeleton of a broad range of periodic nanopatterns and nanoobjects and in addition, DNA can serve as a linker or template to form DNA-hybrid structures with other materials. This approach can be used for the development of new detection strategies as well as nanoelectronic structures and devices.

Method: Here we present a new method for the generation of unprecedented all-organic conjugated-polymer nanoparticle networks guided by DNA, based on a hierarchical self-assembly process. First, microphase separation of amphiphilic block copolymers induced the formation of spherical nanoobjects. As a second ordering concept, DNA base pairing has been employed for the controlled spatial definition of the conjugated-polymer particles within the bulk material. These networks offer the flexibility and the diversity of soft polymeric materials. Thus, simple chemical methodologies could be applied in order to tune the network's electrical, optical and mechanical properties.

Results and conclusions: One- two- and three-dimensional networks have been successfully formed. Common to all morphologies is the integrity of the micelles consisting of DNA block copolymer (DBC), which creates an all-organic engineered network.

Figure 1

First design of higher-ordered structures: A rigid duplex, consisting of 120 bp and two terminal 24mer overhangs (a) which were complementary to the DNA present in the corona of DBC micelles (b).

Figure 2

AFM and HRTEM images of DNA-conjugated polymer nanoparticle network as described in scheme 1. Insets show high magnification of the scanned area. a-c) AFM scans of the linear (scale bar 200 nm), 2-D (scale bar 500 nm) and 3-D materials (scale bar- 1.9 μm, inset 400 nm), respectively and d-f) the corresponding HRTEM pictures (scale bars: d,e. 1 μm, 100 nm, f. 1 μm and 50 nm).

Figure 3

Second design of higher-ordered structures: Pairs of micelles III are assembled with template I and sequence II. Subsequent hybridization with connector oligonucleotides IV leads to superstructures (see text for details).

Figure 4

AFM analysis of the second type of DBC micelle superstructure according to scheme 2. Each image represents DBC architectures with different linker lengths, a) no linker, b) 24 bp- and c) 44 bp linker IV.