Jie Chao

A proximity-based programmable DNA nanoscale assembly line

Our ability to synthesize nanometre-scale chemical species, such as nanoparticles with desired shapes and compositions, offers the exciting prospect of generating new functional materials and devices by combining them in a controlled fashion into larger structures. Self-assembly can achieve this task efficiently, but may be subject to thermodynamic and kinetic limitations: reactants, intermediates and products may collide with each other throughout the assembly time course to produce non-target species instead of target species. An alternative approach to nanoscale assembly uses information-containing molecules such as DNA to control interactions and thereby minimize unwanted cross-talk between different components. In principle, this method should allow the stepwise and programmed construction of target products by linking individually selected nanoscale components—much as an automobile is built on an assembly line. Here we demonstrate that a nanoscale assembly line can be realized by the judicious combination of three known DNA-based modules: a DNA origami tile that provides a framework and track for the assembly process, cassettes containing three independently controlled two-state DNA machines that serve as programmable cargo-donating devices and are attached in series to the tile, and a DNA walker that can move on the track from device to device and collect cargo. As the walker traverses the pathway prescribed by the origami tile track, it sequentially encounters the three DNA devices, each of which can be independently switched between an ‘ON’ state, allowing its cargo to be transferred to the walker, and an ‘OFF’ state, in which no transfer occurs. We use three different types of gold nanoparticle species as cargo and show that the experimental system does indeed allow the controlled fabrication of the eight different products that can be obtained with three two-state devices.

Single-step rapid assembly of DNA origami nanostructures for addressable nanoscale bioreactors.

Self-assembled DNA origami nanostructures have shown great promise for bottom-up construction of complex objects with nanoscale addressability. Here we show that DNA origami-based 1D nanoribbons and nanotubes are one-pot assembled with controllable sizes and nanoscale addressability with high speed (within only 10-20 min), exhibiting extraordinarily high cooperativity that is often observed in assembly of natural molecular machines in cells (e.g. ribosome). By exploiting the high specificity of DNA-based self-assembly, we can precisely anchor proteins on these DNA origami nanostructures with sub-10 nm resolution and at the single-molecule level. We attach a pair of enzymes (horseradish peroxidase and glucose oxidase) at the inner side of DNA nanotubes and observe high coupling efficiency of enzyme cascade within this confined nanospace. Hence, DNA nanostructures with such unprecedented properties shed new light on the design of nanoscale bioreactors and nanomedicine and provide an artificial system for studying enzyme activities and cascade in highly organized and crowded cell-mimicking environments.

Dynamic patterning programmed by DNA tiles captured on a DNA origami substrate

The aim of nanotechnology is to put specific atomic and molecular species where we want them, when we want them there. Achieving such dynamic and functional control could lead to programmable chemical synthesis and nanoscale systems that are responsive to their environments. Structural DNA nanotechnology offers a powerful route to this goal by combining stable branched DNA motifs with cohesive ends to produce programmed nanomechanical devices and fixed or modified patterned lattices. Here, we demonstrate a dynamic form of patterning in which a pattern component is captured between two independently programmed DNA devices. A simple and robust error-correction protocol has been developed that yields programmed targets in all cases. This capture system can lead to dynamic control either on patterns or on programmed elements; this capability enables computation or a change of structural state as a function of information in the surroundings of the system.

Gold nanoparticle-decorated MoS2 nanosheets for simultaneous detection of ascorbic acid, dopamine and uric acid

An electrochemical sensor has been developed for simultaneous detection of dopamine (DA), uric acid (UA) and ascorbic acid (AA) based on a gold nanoparticle-decorated MoS2 nanocomposite (AuNPs@MoS2) modified electrode. The AuNPs@MoS2 nanocomposite has been synthesized by electrodeposition of AuNPs on the MoS2 nanosheets, which possesses better properties than pure AuNPs and MoS2. The AuNPs@MoS2 film modified electrode showed excellent electrocatalytic activity toward the oxidation of AA, DA and UA with three well-resolved oxidation peaks. The peak separation of AA–DA, DA–UA and AA–UA is 151 mV, 137 mV and 288 mV, respectively, which permits the modified electrode to individually or simultaneously analyze AA, DA and UA by differential pulse voltammetry (DPV). Under optimum conditions, the AuNPs@MoS2 modified electrode exhibits linear response toward AA, DA and UA in the range of 50–100 000 μM, 0.05–30 μM and 50–40 000 μM, respectively. Moreover, the MoS2-based modified electrode was successfully employed to determine DA in human serum samples with satisfactory results.

Creating SERS Hot Spots on MoS2 Nanosheets with in Situ Grown Gold Nanoparticles

Herein, a reliable surface-enhanced Raman scattering (SERS)-active substrate has been prepared by synthesizing gold nanoparticles (AuNPs)-decorated MoS2 nanocomposite. The AuNPs grew in situ on the surface of MoS2 nanosheet to form efficient SERS hot spots by a spontaneous redox reaction with tetrachloroauric acid (HAuCl4) without any reducing agent. The morphologies of MoS2 and AuNPs-decorated MoS2 nanosheet were characterized by TEM, HRTEM, and AFM. The formation of hot spots greatly depended on the ratio of MoS2 and HAuCl4. When the concentration of HAuCl4 was 2.4 mM, the as-prepared AuNPs@MoS2-3 nanocomposite exhibited a high-quality SERS activity toward probe molecule due to the generated hot spots. The spot-to-spot SERS signals showed that the relative standard deviation (RSD) in the intensity of the main Raman vibration modes (1362, 1511, and 1652 cm(-1)) of Rhodamine 6G were about 20%, which displayed good uniformity and reproducibility. The AuNPs@MoS2-based substrate was reliable, sensitive, and reproducible, which showed great potential to be an excellent SERS substrate for biological and chemical detection.

Rolling Circle Amplification‐Based DNA Origami Nanostructrures for Intracellular Delivery of Immunostimulatory Drugs

Several single-stranded scaffold DNA, obtained from rolling circle amplification (RCA), are folded by different staples to form DNA nanoribbons. These DNA nanoribbons are rigid, simple to design, and cost-effective drug carriers, which are readily internalized by mammalian cells and show enhanced immunostimulatory activity.

Folding super-sized DNA origami with scaffold strands from long-range PCR

A 26 kilobase single strand DNA fragment was obtained from long-range PCR amplification and subsequent enzymatic digestion, which we folded into a super-sized DNA origami nanostructure by using ∼800 staple strands.

An Exonuclease III‐Powered, On‐Particle Stochastic DNA Walker

DNA-based machines have attracted rapidly growing interest owing to their potential in drug delivery, biocomputing, and diagnostic applications. Herein, we report a type of exonuclease III (Exo III)-powered stochastic DNA walker that can autonomously move on a spherical nucleic acid (SNA)-based 3D track. The motion is propelled by unidirectional Exo III digestion of hybridized DNA tracks in a burnt-bridge mechanism. The operation of this Exo III-propelled DNA walker was monitored in real time and at the single-particle resolution using total internal reflection fluorescence microscopy (TIRF). We further interrogated the morphological effect of the 3D track on the nuclease activity, which suggested that the performance of the DNA walker was critically dependent upon the DNA density and the track conformation. Finally, we demonstrated potential bioanalytical applications of this SNA-based stochastic DNA walker by exploiting movement-triggered cascade signal amplification.

Multivalent capture and detection of cancer cells with DNA nanostructured biosensors and multibranched hybridization chain reaction amplification.

Sensitive detection of cancer cells plays a critically important role in the early detection of cancer and cancer metastasis. However, because circulating tumor cells are extremely rare in peripheral blood, the detection of cancer cells with high analytical sensitivity and specificity remains challenging. Here, we have demonstrated a simple, sensitive and specific detection of cancer cells with the detection sensitivity of four cancer cells, which is lower than the cutoff value with respect to correlation with survival outcomes as well as predictive of metastatic disease in clinical diagnostics. We re-engineered the hybridization chain reaction (HCR) to multibranched HCR (mHCR) that can produce long products with multiple biotins for signal amplification and multiple branched arms for multivalent binding. The capturing gold surface is modified with DNA tetrahedral probes, which provide superior hybridization conditions for the multivalent binding. The synergetic effect of mHCR amplification and multivalent binding lead to the high sensitivity of our detection platform.

Structural DNA Nanotechnology for Intelligent Drug Delivery

Drug delivery carriers have been popularly employed to improve solubility, stability, and efficacy of chemical and biomolecular drugs. Despite the rapid progress in this field, it remains a great challenge to develop an ideal carrier with minimal cytotoxicity, high biocompatibility and intelligence for targeted controlled release. The emergence of DNA nanotechnology offers unprecedented opportunities in this regard. Due to the unparalleled self-recognition properties of DNA molecules, it is possible to create numerous artificial DNA nanostructures with well-defined structures and DNA nanodevices with precisely controlled motions. More importantly, recent studies have proven that DNA nanostructures possess greater permeability to the membrane barrier of cells, which pave the way to developing new drug delivery carriers with nucleic acids, are summarized. In this Concept, recent advances on the design and fabrication of both static and dynamic DNA nanostructures, and the use of these nanostructures for the delivery of various types of drugs, are highlighted. It is also demonstrated that dynamic DNA nanostructures provide the required intelligence to realize logically controlled drug release.