DNA-carbon nanotube conjugates prepared by a versatile method using streptavidin-biotin recognition

DNA-directed assembly of nanomaterials and their biomedical applications

In the past decades, DNA has been widely used in the field of nanostructures due to its unique programmable properties. Besides being used to form its own diverse structures such as the assembly of DNA origami, DNA can also be used for the assembly of nanostructures with other materials. In this review, different strategies for the functionalization of DNA on nanoparticle surfaces are listed, and the roles of DNA in the assembly of nanostructures as well as the influencing factors are discussed. Finally, the biomedical applications of DNA-assembled nanostructures were summarized. This review provided new insight into the application of DNA in nanostructure assembly.

Triblock probe-polyA-probe electrochemical interfacial engineering for the sensitive analysis of RNAi plants

RNA interference (RNAi) is under fast development in agriculture and brings new challenge for GMO analysis. We developed a electrochemical biosensor for the analysis of GM maize samples based on a polyA-DNA capturing probe. Ultrasensitive detection of 10 fM RNA was realized.

Construction and characterization of metal ion-containing DNA nanowires for synthetic biology and nanotechnology

DNA is an attractive candidate for integration into nanoelectronics as a biological nanowire due to its linear geometry, definable base sequence, easy, inexpensive and non-toxic replication and self-assembling properties. Recently we discovered that by intercalating Ag+ in polycytosine-mismatch oligonucleotides, the resulting C-Ag+-C duplexes are able to conduct charge efficiently. To map the functionality and biostability of this system, we built and characterized internally-functionalized DNA nanowires through non-canonical, Ag+-mediated base pairing in duplexes containing cytosine-cytosine mismatches. We assessed the thermal and chemical stability of ion-coordinated duplexes in aqueous solutions and conclude that the C-Ag+-C bond forms DNA duplexes with replicable geometry, predictable thermodynamics, and tunable length. We demonstrated continuous ion chain formation in oligonucleotides of 11-50 nucleotides (nt), and enzyme ligation of mixed strands up to six times that length. This construction is feasible without detectable silver nanocluster contaminants. Functional gene parts for the synthesis of DNA- and RNA-based, C-Ag+-C duplexes in a cell-free system have been constructed in an Escherichia coli expression plasmid and added to the open-source BioBrick Registry, paving the way to realizing the promise of inexpensive industrial production. With appropriate design constraints, this conductive variant of DNA demonstrates promise for use in synthetic biological constructs as a dynamic nucleic acid component and contributes molecular electronic functionality to DNA that is not already found in nature. We propose a viable route to fabricating stable DNA nanowires in cell-free and synthetic biological systems for the production of self-assembling nanoelectronic architectures.

Tuning the Coupling in Single-Molecule Heterostructures: DNA-Programmed and Reconfigurable Carbon Nanotube-Based Nanohybrids

Herein a strategy is presented for the assembly of both static and stimuli-responsive single-molecule heterostructures, where the distance and electronic coupling between an individual functional nanomoiety and a carbon nanostructure are tuned via the use of DNA linkers. As proof of concept, the formation of 1:1 nanohybrids is controlled, where single quantum dots (QDs) are tethered to the ends of individual carbon nanotubes (CNTs) in solution with DNA interconnects of different lengths. Photoluminescence investigations-both in solution and at the single-hybrid level-demonstrate the electronic coupling between the two nanostructures; notably this is observed to progressively scale, with charge transfer becoming the dominant process as the linkers length is reduced. Additionally, stimuli-responsive CNT-QD nanohybrids are assembled, where the distance and hence the electronic coupling between an individual CNT and a single QD are dynamically modulated via the addition and removal of potassium (K+) cations; the system is further found to be sensitive to K+ concentrations from 1 pM to 25 × 10-3 m. The level of control demonstrated here in modulating the electronic coupling of reconfigurable single-molecule heterostructures, comprising an individual functional nanomoiety and a carbon nanoelectrode, is of importance for the development of tunable molecular optoelectronic systems and devices.

Site-Specific One-to-One Click Coupling of Single Proteins to Individual Carbon Nanotubes: A Single-Molecule Approach

We report the site-specific coupling of single proteins to individual carbon nanotubes (CNTs) in solution and with single-molecule control. Using an orthogonal Click reaction, Green Fluorescent Protein (GFP) was engineered to contain a genetically encoded azide group and then bound to CNT ends in different configurations: in close proximity or at longer distances from the GFP's functional center. Atomic force microscopy and fluorescence analysis in solution and on surfaces at the single-protein level confirmed the importance of bioengineering optimal protein attachment sites to achieve direct protein-nanotube communication and bridging.

Three-dimensional surface patterning by DNA-modifying enzymes

Self-assembled patterned multilayers may be fabricated using DNA monolayers and the orchestrated reactions of DNA-modifying enzymes. To demonstrate this approach, DNA monolayers were formed on silicon and cleaved quantitatively with a restriction enzyme. Subsequently, fluorescently labeled nucleotides were covalently incorporated to the cleaved DNA. Nucleotide addition was shown to be highly selective according to the sequence at the cleavage site, and no nonspecific adsorption to the surface was observed. The dual action of the DNA-modifying enzymes was quantitative and could be utilized in the fabrication of multilayered structures. Other DNA-modifying enzymes can be exploited in this manner to enrich the repertoire of self-assembly supramolecular structure fabrication.

DNA origami as a nanoscale template for protein assembly

We describe two general approaches to the utilization of DNA origami structures for the assembly of materials. In one approach, DNA origami is used as a prefabricated template for subsequent assembly of materials. In the other, materials are assembled simultaneously with the DNA origami, i.e. the DNA origami technique is used to drive the assembly of materials. Fabrication of complex protein structures is demonstrated by these two approaches. The latter approach has the potential to be extended to the assembly of multiple materials with single attachment chemistry.

A three-branched DNA template for carbon nanotube self-assembly into nanodevice configuration

We report here the first realization of an artificial branched DNA template where a single wall carbon nanotube is positioned with the necessary geometry of an individually gated field effect transistor.