Assembling Defined DNA Nanostructure with Nitrogen‐Enriched Carbon Dots for Theranostic Cancer Applications

DNA nanostructures as scaffolds for drug delivery, biosensing, and bioimaging are hindered by its vulnerability in physiological settings, less favorable of incorporating arbitrary guest molecules and other desirable functionalities. Noncanonical self‐assembly of DNA nanostructures with small molecules in an alternative system is an attractive strategy to expand their applications in multidisciplinary fields and is rarely explored. This work reports a nitrogen‐enriched carbon dots (NCDs)‐mediated DNA nanostructure self‐assembly strategy. Given the excellent photoluminescence and photodynamic properties of NCDs, the obtained DNA/NCDs nanocomplex holds great potential for bioimaging and anticancer therapy. NCDs can mediate DNA nanoprism (NP^NCD) self‐assembly isothermally at a large temperature and pH range in a magnesium‐free manner. To explore the suitability of NP^NCD in potential biomedical applications, the cytotoxicity and cellular uptake efficiency of NP^NCD are evaluated. NP^NCD with KRAS siRNA (NP^NCDK) is further conjugated for KRAS‐mutated nonsmall cell lung cancer therapy. The NP^NCDK shows excellent gene knockdown efficiency and anticancer effect in vitro. The current study suggests that conjugating NCDs with programmable DNA nanostructures is a powerful strategy to endow DNA nanostructures with new functionalities, and NP^NCD may be a potential theranostic platform with further fine‐tuned properties of CDs such as near‐red fluorescence or photothermal activities.     

Self‐Assembly of Microparticles by Supramolecular Homopolymerization of One Component DNA Molecule

DNA is a superb molecule for self‐assembly of nanostructures. Often many DNA strands are required for the assembly of one DNA nanostructure. For lowering the cost of synthesizing DNA strands and facilitating the assembly process, it is highly desirable to use a minimal number of unique strands for potential technological applications. Herein, a strategy is reported to assemble a series of DNA microparticles (DNAµPs) from one component DNA strand. As a demonstration of the application of the resulting DNAµPs, the design and assembled DNAµPs are modified to carry additional single‐stranded tails on their surfaces. The modified DNAµPs can either capture other nucleic acids or display CpG motifs to stimulate immune responses.     

Orthogonal protein decoration of DNA nanostructures

The development of robust DNA-protein coupling techniques is mandatory for applications of DNA nanostructures in biomedical diagnostics, fundamental biochemistry, and other fields in biomolecular nanosciences. The use of self-labeling fusion proteins, which are orthogonal to biotin-streptavidin and antibody-antigen interactions, is described for the site-selective protein decoration of two exemplary DNA nanostructures: a four-way junction X-tile motif and a 3D DNA tetrahedron. Multifunctional DNA superstructures bearing up to four different proteins are generated and characterized by electrophoresis and microplate-based functionality assays. Steric and electrostatic interactions are identified as critical parameters controlling the efficiency of DNA-protein ligation. The results indicate that this method is versatile and broadly applicable, not only for the functionalization of DNA architectures but also for the site-specific decoration of other molecular materials and devices containing several different proteins.     

Self‐Assembly: I‐Motif Nanospheres: Unusual Self‐Assembly of Long Cytosine Strands (Small 8/2011)

The synthesis and characterization of novel DNA structures based on tetraplex cytosine (C) arrangements, known as i‐motifs or i‐tetraplexes, is reported. Atomic force microscopy (AFM) investigation shows that long C‐strands in mild acidic conditions form compact spherically shaped nanostructures. The DNA nanospheres are characterized by a typical uniform shape and narrow height distribution. Electrostatic force microscopy (EFM) measurements performed on the i‐motif spheres clearly show their electrical polarizability. Further investigations by scanning tunneling microscopy (STM) at ultrahigh vacuum reveals that the structures exhibit an average voltage gap of 1.9 eV, which is narrower than the voltage gap previously measured for poly(dG)–poly(dC) molecules in similar conditions.