Hao Pei

A DNA nanostructure-based biomolecular probe carrier platform for electrochemical biosensing.

A critical challenge in surface-based biomolecular detection is the reduced accessibility of target molecules to probes arranged on a heterogeneous surface compared to probe–target recognition in homogeneous solution.[1–5] To improve the recognition abilities of such heterogeneous surface probes, much effort has been devoted to control the surface chemistry, conformation, and packing density of the probe molecules as well as the size and geometry of the surface.[6–11] Here, we devise a new concept to achieve improved probe–target recognition properties by introducing a probe bearing a 3D DNA nanostructure-based chip platform. DNA nanotechnology has attracted intense interest because the unparalleled self-recognition properties of DNA offer flexibility and convenience for the ‘bottom-up’ construction of exquisite nanostructures with high controllability and precision.[12–20] Our strategy to design and construct 3D nanostructured recognition probes on a surface provides a significantly enhanced spatial positioning range and accessibility of the probes on a surface over previously reported linear or stem-loop probe structures.[2,7]

Reconfigurable Three‐Dimensional DNA Nanostructures for the Construction of Intracellular Logic Sensors

Right out of the (logic) gate: Logic gates made from 3D DNA nanotetrahedra were constructed that are responsive to various ions, small molecules, and short strands of DNA. By including dynamic sequences in one or more edges of the tetrahedra, a FRET signal can be generated in the manner of AND, OR, XOR, and INH logic gates, as well as a half-adder circuit. These DNA logic gates were also applied to intracellular detection of ATP.

Smart Drug Delivery Nanocarriers with Self-Assembled DNA Nanostructures

Self-assembled DNA nanostructures have emerged as a type of nano-biomaterials with precise structures, versatile functions and numerous applications. One particularly promising application of these DNA nanostructures is to develop universal nanocarriers for smart and targeted drug delivery. DNA is the genetic material in nature, and inherently biocompatible. Nevertheless, cell membranes are barely permeable to naked DNA molecules, either single- or double- stranded; transport across the cell membrane is only possible with the assistance of transfection agents. Interestingly, recent studies revealed that many DNA nanostructures could readily go into cells with high cell uptake efficiency. In this Progress Report, we will review recent advances on using various DNA nanostructures, e.g., DNA nanotubes, DNA tetrahedra, and DNA origami nanorobot, as drug delivery nanocarriers, and demonstrate several examples aiming at therapeutic applications with CpG-based immunostimulatory and siRNA-based gene silencing oligonucleotides.

Gold-Nanoparticle-Mediated Jigsaw-Puzzle-like Assembly of Supersized Plasmonic DNA Origami

DNA origami has rapidly emerged as a powerful and programmable method to construct functional nanostructures. However, the size limitation of approximately 100u2005nm in classic DNAu2005origami hampers its plasmonic applications. Herein, we report a jigsaw-puzzle-like assembly strategy mediated by gold nanoparticles (AuNPs) to break the size limitation of DNA origami. We demonstrated that oligonucleotide-functionalized AuNPs function as universal joint units for the one-pot assembly of parent DNA origami of triangular shape to form sub-microscale super-origami nanostructures. AuNPs anchored at predefined positions of the super-origami exhibited strong interparticle plasmonic coupling. This AuNP-mediated strategy offers new opportunities to drive macroscopic self-assembly and to fabricate well-defined nanophotonic materials and devices.

Self-Assembly of Poly-Adenine-Tailed CpG Oligonucleotide-Gold Nanoparticle Nanoconjugates with Immunostimulatory Activity

Synthetic unmethylated cytosine-guanine (CpG) oligodeoxynucleotides (CpG ODNs) possess high immunostimulatory activity and have been widely used as a therapeutic tool for various diseases including infection, allergies, and cancer. A variety of nanocarriers have been developed for intracellular delivery of CpG ODNs that are otherwise nonpermeable through the cellular membrane. For example, previous studies showed that gold nanoparticles (AuNPs) could efficiently deliver synthetic thiolated CpG ODNs into cultured cells and induce expression of proinflammatory cytokines. Nevertheless, the necessity of using thiolated CpG ODNs for the modification of AuNPs inevitably complicates the synthesis of the nanoconjugates and increases the cost. A new approach is demonstrated for facile assembly of AuNP-CpG nanoconjugates for cost-effective drug delivery. It is found that non-thiolated, diblock ODNs containing a CpG motif and a poly-adenine (polyA) tail can readily self-assemble on the surface of AuNPs with controllable and tunable density. Such nanoconjugates are efficiently delivered into RAW264.7 cells and induce immune response in a Toll-like receptor 9 (TLR9)-dependent manner. Under optimal conditions, polyA-CpG-AuNPs show significantly higher immunostimulatory activity than their thiolated counterpart. In addition, the immunostimulatory activity of CpG-AuNPs can be modulated by varying the length of the polyA tail. In vivo induction of immune responses in mice is demonstrated by using polyA-tailed CpG-AuNP nanoconjugates.

Charge Transport within a Three-Dimensional DNA Nanostructure Framework

Three-dimensional (3D) DNA nanostructures have shown great promise for various applications including molecular sensing and therapeutics. Here we report kinetic studies of DNA-mediated charge transport (CT) within a 3D DNA nanostructure framework. A tetrahedral DNA nanostructure was used to investigate the through-duplex and through-space CT of small redox molecules (methylene blue (MB) and ferrocene (Fc)) that were bound to specific positions above the surface of the gold electrode. CT rate measurements provide unambiguous evidence that the intercalative MB probe undergoes efficient mediated CT over longer distances along the duplex, whereas the nonintercalative Fc probe tunnels electrons through the space. This study sheds new light on DNA-based molecular electronics and on designing high-performance biosensor devices.

Dynamic and Quantitative Control of the DNA-Mediated Growth of Gold Plasmonic Nanostructures†

Reproducible and controllable growth of nanostructures with well-defined physical and chemical properties is a longstanding problem in nanoscience. A key step to address this issue is to understand their underlying growth mechanism, which is often entangled in the complexity of growth environments and obscured by rapid reaction speeds. Herein, we demonstrate that the evolution of size, surface morphology, and the optical properties of gold plasmonic nanostructures could be quantitatively intercepted by dynamic and stoichiometric control of the DNA-mediated growth. By combining synchrotron-based small-angle X-ray scattering (SAXS) with transmission electron microscopy (TEM), we reliably obtained quantitative structural parameters for these fine nanostructures that correlate well with their optical properties as identified by UV/Vis absorption and dark-field scattering spectroscopy. Through this comprehensive study, we report a growth mechanism for gold plasmonic nanostructures, and the first semiquantitative revelation of the remarkable interplay between their morphology and unique plasmonic properties.

Pattern Recognition Analysis of Proteins Using DNA‐Decorated Catalytic Gold Nanoparticles

A label-free protein analysis strategy is based on patterns of gold nanoparticle (AuNP) growth. AuNPs pretreated with different oligonucleotides are challenged with various proteins. After Au reduction, the colorimetric patterns are processed with linear discriminant analysis. This method discriminates different proteins, or one protein of different concentrations, in mixed samples or even serum and urine.

A MoS2?based system for efficient immobilization of hemoglobin and biosensing applications

A novel hydrogen peroxide (H2O2) and nitric oxide (NO) biosensor was fabricated by immobilizing hemoglobin (Hb) on a gold nanoparticle-decorated MoS2 nanosheet (AuNPs@MoS2) nanocomposite film modified glass carbon electrode. The AuNPs@MoS2 nanocomposite not only made the immobilized Hb keep its native biological activity but also facilitated the electron transfer between electrode and the electroactive center of Hb due to its excellent conductivity and biocompatibility. The direct electrochemistry and bioelectrocatalytic activity of Hb were investigated by cyclic voltammetry (CV). The modified electrode showed good electrocatalytic ability toward the reduction of H2O2 and NO. Under optimal conditions, the current response was linear with the concentration of H2O2 and NO in the range from 10 to 300 μM and 10 to 1100 μM with a detection limit of 4 and 5 μM, respectively. This MoS2-based biosensor was sensitive, reproducible and stable, indicating that AuNPs@MoS2 nanocomposite maybe a promising platform to construct electrochemical sensors for chemical and biological molecules detection.

Self-assembled DNA tetrahedral optofluidic lasers with precise and tunable gain control

We have applied self-assembled DNA tetrahedral nanostructures for the precise and tunable control of the gain in an optofluidic fluorescence resonance energy transfer (FRET) laser. By adjusting the ratio of the donor and the acceptor attached to the tetrahedral vertices, 3.8 times reduction in the lasing threshold and 28-fold enhancement in the lasing efficiency were demonstrated. This work takes advantage of the self-recognition and self-assembly capabilities of biomolecules with well-defined structures and addressability, enabling nano-engineering of the laser down to the molecular level.