Coupling nanomaterials with biomolecular recognition events represents a new direction in nanotechnology toward the development of novel molecular diagnostic tools. Here a graphene oxide (GO)‐based multicolor fluorescent DNA nanoprobe that allows rapid, sensitive, and selective detection of DNA targets in homogeneous solution by exploiting interactions between GO and DNA molecules is reported. Because of the extraordinarily high quenching efficiency of GO, the fluorescent ssDNA probe exhibits minimal background fluorescence, while strong emission is observed when it forms a double helix with the specific targets, leading to a high signal‐to‐background ratio. Importantly, the large planar surface of GO allows simultaneous quenching of multiple DNA probes labeled with different dyes, leading to a multicolor sensor for the detection of multiple DNA targets in the same solution. It is also demonstrated that this GO‐based sensing platform is suitable for the detection of a range of analytes when complemented with the use of functional DNA structures.

Isothermal amplification of nucleic acids is a simple process that rapidly and efficiently accumulates nucleic acid sequences at constant temperature. Since the early 1990s, various isothermal amplification techniques have been developed as alternatives to polymerase chain reaction (PCR). These isothermal amplification methods have been used for biosensing targets such as DNA, RNA, cells, proteins, small molecules, and ions. The applications of these techniques for in situ or intracellular bioimaging and sequencing have been amply demonstrated. Amplicons produced by isothermal amplification methods have also been utilized to construct versatile nucleic acid nanomaterials for promising applications in biomedicine, bioimaging, and biosensing. The integration of isothermal amplification into microsystems or portable devices improves nucleic acid-based on-site assays and confers high sensitivity. Single-cell and single-molecule analyses have also been implemented based on integrated microfluidic systems. In this review, we provide a comprehensive overview of the isothermal amplification of nucleic acids encompassing work published in the past two decades. First, different isothermal amplification techniques are classified into three types based on reaction kinetics. Then, we summarize the applications of isothermal amplification in bioanalysis, diagnostics, nanotechnology, materials science, and device integration. Finally, several challenges and perspectives in the field are discussed.

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Over the past decade, we have seen rapid advances in applying nanotechnology in biomedical areas including bioimaging, biodetection, and drug delivery. As an emerging field, DNA nanotechnology offers simple yet powerful design techniques for self-assembly of nanostructures with unique advantages and high potential in enhancing drug targeting and reducing drug toxicity. Various sequence programming and optimization approaches have been developed to design DNA nanostructures with precisely engineered, controllable size, shape, surface chemistry, and function. Potent anticancer drug molecules, including Doxorubicin and CpG oligonucleotides, have been successfully loaded on DNA nanostructures to increase their cell uptake efficiency. These advances have implicated the bright future of DNA nanotechnology-enabled nanomedicine. In this review, we begin with the origin of DNA nanotechnology, followed by summarizing state-of-the-art strategies for the construction of DNA nanostructures and drug payloads delivered by DNA nanovehicles. Further, we discuss the cellular fates of DNA nanostructures as well as challenges and opportunities for DNA nanostructure-based drug delivery.

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Hepatitis B virus (HBV) infects more than 300 million people and is a leading cause of liver cancer and disease. The HBV HBx protein is essential for infection; HBx activation of Src is important for HBV DNA replication. In our study, HBx activated cytosolic calcium-dependent proline-rich tyrosine kinase-2 (Pyk2), a Src kinase activator. HBx activation of HBV DNA replication was blocked by inhibiting Pyk2 or calcium signaling mediated by mitochondrial calcium channels, which suggests that HBx targets mitochondrial calcium regulation. Reagents that increased cytosolic calcium substituted for HBx protein in HBV DNA replication. Thus, alteration of cytosolic calcium was a fundamental requirement for HBV replication and was mediated by HBx protein.

Aptamers are artificial oligonucleotide receptors originated from in vitro selection (SELEX). 1 In principle, aptamers with high specificity and affinity can be selected for any given target, ranging from small molecules to large proteins and even cells. 2 Therefore, aptamers are widely recognized as highly promising tools for a variety of important applications. 3,4 Aptamers are particularly useful as the biosensing element as they are chemically stable, readily available, and offer high flexibility in biosensor design. [5][6][7][8][9][10][11] Recently, Heeger, Plaxco, and others developed a series of novel electrochemical aptamer-based (E-AB) sensors for thrombin, cocaine, and potassium, [12][13][14] an analogous version to the electrochemical DNA (E-DNA) sensor. 8,15 These E-AB sensors are based on binding-induced conformational changes of redox-tagged and surface-confined aptamers, which have proven highly sensitive and selective. 12-14 Also, because E-AB sensors are electrochemistrybased, they are inherently fast, portable, and cost-effective. However, since E-AB relies on unique structures of aptamers, these sensors have to be designed case-by-case for different aptamertarget pairs. As a step further, Xiao et al. recently developed a potentially generalizable E-AB sensor for thrombin by using targetinduced strand displacement. 16 Here we report a target-responsive electrochemical aptamer switch (TREAS), which is a signal-on sensor featuring both generalizability and simplicity in design, toward reagentless detection of adenosine triphosphate (ATP) with high sensitivity and selectivity.We employed an in vitro selected 27-base anti-ATP aptamer, which possesses high affinity for ATP while not for its analogues, cytidine triphosphate (CTP), guanosine triphosphate (GTP), and uridine triphosphate (UTP). 17 The anti-ATP aptamer dually labeled with 3′-SH and 5′-ferrocene is self-assembled on gold electrodes in its duplex form (Scheme 1). We reason that ferrocene is distal to the electrode surface, thus cannot efficiently exchange electrons with the underlying electrodes due to large distance separation (∼10 nm) in this eT OFF state. In the presence of the target ATP, the tertiary aptamer structure is stabilized, which responsively denatures the duplex and liberates the complementary DNA, similar to the aptamer structural switch in solution. 18 As a consequence of this structural switch from the duplex to the tertiary aptamer structure (duplex-to-aptamer), the ferrocene moiety approaches the electrode surface and generates measurable electrochemical signals (eT ON). Of note, compared to the E-AB thrombin sensor reported by Xiao et al., 16 our TREAS is similarly generalizable while it has several advantages. First, the sensor architecture is simpler. The sensing DNA strand of E-AB contains three parts, aptamer region (for recognition), duplex region (structural support), and spacer region (linkage), thus is inherently longer than the corresponding TREAS sensing strand (only aptamer sequence). Second, TREAS has two we...