Multiresponsive Rolling Circle Amplification for DNA Logic Gates Mediated by Endonuclease

MicroRNA Detection with CRISPR/Cas

Low-cost detection of miRNAs has caught broad attention in recent years due to the potential application of these small noncoding RNAs for diagnostics and therapeutic purposes. Their small size and low abundance, however, derive challenges in engineering robust detection tools. To date, multiple detection assays have been developed to achieve highly specific recognition of trace amount of miRNA with state-of-the-art nucleic acid detection and signal amplification techniques. In this chapter we describe how isothermal amplification techniques and CRISPR/Cas-based techniques can be integrated to generate rationally designed miRNA detection systems for specific miRNA.

Advances in regenerative medicine applications of tetrahedral framework nucleic acid-based nanomaterials: an expert consensus recommendation

With the emergence of DNA nanotechnology in the 1980s, self-assembled DNA nanostructures have attracted considerable attention worldwide due to their inherent biocompatibility, unsurpassed programmability, and versatile functions. Especially promising nanostructures are tetrahedral framework nucleic acids (tFNAs), first proposed by Turberfield with the use of a one-step annealing approach. Benefiting from their various merits, such as simple synthesis, high reproducibility, structural stability, cellular internalization, tissue permeability, and editable functionality, tFNAs have been widely applied in the biomedical field as three-dimensional DNA nanomaterials. Surprisingly, tFNAs exhibit positive effects on cellular biological behaviors and tissue regeneration, which may be used to treat inflammatory and degenerative diseases. According to their intended application and carrying capacity, tFNAs could carry functional nucleic acids or therapeutic molecules through extended sequences, sticky-end hybridization, intercalation, and encapsulation based on the Watson and Crick principle. Additionally, dynamic tFNAs also have potential applications in controlled and targeted therapies. This review summarized the latest progress in pure/modified/dynamic tFNAs and demonstrated their regenerative medicine applications. These applications include promoting the regeneration of the bone, cartilage, nerve, skin, vasculature, or muscle and treating diseases such as bone defects, neurological disorders, joint-related inflammatory diseases, periodontitis, and immune diseases.

Biomineralized Zeolitic Imidazolate Framework-8 Nanoparticles Enable Polymerase-Driven DNA Biocomputing for Reliable Cell Identification

Investigating multiple miRNA expression patterns in living cells by DNA logic biocomputing is a valuable strategy for diagnosis and biomedical studies. The introduction of protein enzymes in DNA logic biocomputing circuits not only expands the toolbox of nucleic acid assembly techniques, but also further improves the specificity of recognizing and processing of DNA input. Herein, a polymerase-driven primer exchange reaction, acting as the sensing module, is introduced into the biocomputing system and transduces the multiple miRNAs sensing event into the intermediate triggers for activating the subsequent processing module, which further performs signal readout through DNAzyme catalytic substrate cleavage reaction. By using biomineralized zeolitic imidazolate framework-8 nanoparticles (ZIF-8 NPs) to deliver all the components of the biocomputing system, including polymerase and DNA probes, we realized polymerase-driven DNA biocomputing operations in living cells, including AND and OR gates. The results exhibited that biomineralized ZIF-8 NPs can protect the loaded cargoes against the external environment and deliver them efficiently to the cytoplasm. The polymerase-driven DNA biocomputing system based on multiple miRNAs sensing can be used for reliable cell identification and may provide a promising platform for more accurate diagnosis and programmable therapeutics.

Deoxyribonucleic acid anchored on cell membranes for biomedical application

Engineering cellular membranes with functional molecules provides an attractive strategy to manipulate cellular behaviors and functionalities. Currently, synthetic deoxyribonucleic acid (DNA) has emerged as a promising molecular tool to engineer cellular membranes for biomedical applications due to its molecular recognition and programmable properties. In this review, we summarized the recent advances in anchoring DNA on the cellular membranes and their applications. The strategies for anchoring DNA on cell membranes were summarized. Then their applications, such as immune response activation, receptor oligomerization regulation, membrane structure mimicking, cell-surface biosensing, and construction of cell clusters, were listed. The DNA-enabled intelligent systems which were able to sense stimuli such as DNA strands, light, and metal ions were highlighted. Finally, insights regarding the remaining challenges and possible future directions were provided.

No-nonspecific recognition-based amplification strategy for endonuclease activity screening with dual-color DNA nano-clew

The inevitable nonspecific recognition severely restricted widely used nucleic acid amplification strategies, which has become an urgent problem in current scientific research. Herein, we developed a novel no-nonspecific recognition-based amplification strategy to construct dual-color dye loaded nano-clew as ultrabright illuminant for screening endonuclease activity with Escherichia coliRY13 I (EcoR I) as a model, which overcame some major drawbacks such as nonspecific recognition and photobleaching. Typically, the target endonuclease induces cleavage of the customized dumbbell-shape substrate (DSS) to generate two same triggers that can initiate the rolling circle amplification (RCA) to prepare long single-strand DNA (lssDNA), which could self-assemble into irregular DNA nano-clew based on the electrostatic interactions with Mg²⁺ to furtherly capture the donor and accepter fluorophore proximately, constructing the dye loaded nano-clew with dual-color fluorescence (FL) emission to resist photobleaching. Importantly, in absence of EcoR I, even if the DSS could combine with circular template a little, the reaction system performed hardly RCA reaction due to no cohesive terminus, resulting an extremely low background fluorescence signal because of the prevention of nonspecific RCA reaction. As expected, the proposed sensing platform with a low limit of detection (LOD) of 3.4 × 10^-7 U/μL was demonstrated to work well for endonuclease inhibitors screening also. Furthermore, the proposed no-nonspecific recognition strategy could be readily extended to various DNA or RNA enzymes such as DNA methyltransferase, DNA repair-related enzymes and polynucleotide kinase just by simply changing the recognition sequence in the DNA substrate, performing great potential of endonucleases-related clinical diagnosis and drugs discovery.

Biocomputing Based on DNA Strand Displacement Reactions

The high sequence specificity and precise base complementary pairing principle of DNA provides a rich orthogonal molecular library for molecular programming, making it one of the most promising materials for developing bio-compatible intelligence. In recent years, DNA has been extensively studied and applied in the field of biological computing. Among them, the toehold-mediated strand displacement reaction (SDR) with properties including enzyme free, flexible design and precise control, have been extensively used to construct biological computing circuits. This review provides a systemic overview of SDR design principles and the applications. Strategies for designing DNA-only, enzymes-assisted, other molecules-involved and external stimuli-controlled SDRs are described. The recently realized computing functions and the application of DNA computing in other fields are introduced. Finally, the advantages and challenges of SDR-based computing are discussed.

A "signal-on" electrochemical biosensor based on DNAzyme-driven bipedal DNA walkers and TdT-mediated cascade signal amplification strategy

In this work, a dual amplified signal enhancement approach based on coupling deoxyribozyme (DNAzyme)-driven bipedal DNA walkers (BDW) and terminal deoxynucleotidyl transferase (TdT)-mediated DNA elongation signal amplifications has been developed for highly sensitive and label-free electrochemical detection of thrombin in human serums. In presence of thrombin, the BDW complex, which is comprised from the target thrombin and two DNAzyme-containing probes, can exhibit autonomous cleavage behavior on the surface of the substrate DNA (SD) modified electrode, and remove the cleaved DNA fragment from the electrode surface. Subsequently, the TdT can catalyze the elongation of the SD with free 3'-OH termini and formation of many G-quadruplex sequence replicates with the presence of 2'-deoxyaguanosine-5'-triphosphate (dGTP) and adenosine 5'-triphosphate (dATP) at a molar ratio of 6:4. These G-quadruplex sequences bind hemin and generate drastically amplified current response for sensitive detection of thrombin in a "signal-on" and completely label-free fashion. Under optimized conditions, the response peak current was linear with the concentration of thrombin in the range from 0.5 pM to 100000 pM with detection limit of 0.31 pM. This research provides us a sustainable idea for the hyphenated multiple amplification strategies and a stable and effective method for the detection of protein biomarkers.

Probe computing model based on small molecular switch

Background

DNA is a promising candidate for the construction of biological devices due to its unique properties, including structural simplicity, convenient synthesis, high flexibility, and predictable behavior. And DNA has been widely used to construct the advanced logic devices.

Results

Herein, a molecular probe apparatus was constructed based on DNA molecular computing to perform fluorescent quenching and fluorescent signal recovery, with an ’ ON/OFF’ switching function. In this study, firstly, we program the streptavidin-mediated fluorescent quenching apparatus based on short-distance strand migration. The variation of fluorescent signal is acted as output. Then DNAzyme as a switching controller was involved to regulate the fluorescent signal increase. Finally, on this base, a cascade DNA logic gate consists of two logic AND operations was developed to enrich probe machine.

Conclusion

The designed probe computing model can be implemented with readout of fluorescence intensity, and exhibits great potential applications in the field of bioimaging as well as disease diagnosis.

Photoresponsive Self-Assembled DNA Nanomaterials: Design, Working Principles, and Applications

Photoresponsive DNA nanomaterials represent a new class of remarkable functional materials. By adjusting the irradiation wavelength, light intensity, and exposure time, various photocontrolled DNA-based systems can be reversibly or irreversibly regulated in respect of their size, shape, conformation, movement, and dissociation/association. This Review introduces the most updated progress in the development of photoresponsive DNA-based system and emphasizes their advantages over other stimuli-responsive systems. Their design and mechanisms to trigger the photoresponses are shown and discussed. The potential application of these photon-responsive DNA nanomaterials in biology, biomedicine, materials science, nanophotonic and nanoelectronic are also covered and described. The challenges faced and further directions of the development of photocontrolled DNA-based systems are also highlighted.

A new electrochemical aptasensor for sensitive assay of a protein based on the dual-signaling electrochemical ratiometric method and DNA walker strategy

Herein, a new electrochemical aptamer-based biosensor for highly sensitive assay of thrombin has been developed based on the dual-signaling electrochemical ratiometric method and the DNA walker strategy, and shows a low detection limit of about 56 fM.

Logic circuit controlled multi-responsive branched DNA scaffolds

A logic circuit controlled multi-responsive sensing platform built on a three-way DNA junction (TWJ) is reported. It enabled the construction of novel fluorescent sensing platforms responsive to any target out of HIV gene, ATP and pH value, and furthermore were logically regulated by two other targets and then behaved as different logic circuits, which consist of two tandem AND gates or cascaded NAND and INH gates by varying the positions of the fluorescent tags.

Photo-switchable patterning of gold nanoparticles along 3D DNA nanotubes

We have developed a reversible photoswitching platform based on 3D DNA nanotubes by integrating photoisomerizable azobenzene molecules along the edges. This would allow the reversible conformational changes of the nanotubes between linear and bent features and the switchable patterning of gold nanoparticles in response to UV/Vis irradiation. This work provides a new strategy to create reversibly reconfigurable transformative nanomaterials for potential applications in the fields of renewable energy, sensing, nanorobotics and nanomedicine.

Highly Effective and Low-Cost MicroRNA Detection with CRISPR-Cas9

MicroRNAs have been reported as related to multiple diseases and have potential applications in diagnosis and therapeutics. However, detection of miRNAs remains improvable, given their complexity, high cost, and low sensitivity as of currently. In this study, we attempt to build a novel platform that detects miRNAs at low cost and high efficacy. This detection system contains isothermal amplification, detecting and reporting process based on rolling circle amplification, CRISPR-Cas9, and split-horseradish peroxidase techniques. It is able to detect trace amount of miRNAs from samples with mere single-base specificity. Moreover, we demonstrated that such scheme can effectively detect target miRNAs in clinical serum samples and significantly distinguish patients of non-small cell lung cancer from healthy volunteers by detecting the previously reported biomarker: circulating let-7a. As the first to use CRISPR-Cas9 in miRNA detection, this method is a promising approach capable of being applied in screening, diagnosing, and prognosticating of multiple diseases.

Target induced reconstruction of DNAzymatic amplifier nanomachines in living cells for concurrent imaging and gene silencing

A novel DNAzymatic amplifier nanomachine that enables the functions of concurrent mRNA imaging and gene silencing in living cells has been reported.

A label-free and universal platform for the construction of an odd/even detector for decimal numbers based on graphene oxide and DNA-stabilized silver nanoclusters

Molecular logic devices with different functions can perform various tasks in the areas of biological molecule detection, disease diagnosis, multivariate analysis, and bioimaging. Herein, a series of logic circuits based on silver nanoclusters (AgNCs)/graphene oxide (GO) are constructed to execute nonarithmetic functions, including 3-, 4-, and 5-bit odd/even checking. The resulting devices can differentiate between even and odd decimal numbers in the range from 0 to 31. Moreover, the devices can be expanded to operate with wider ranges of numbers when more inputs are added. The signal reporter is structured using AgNCs and GO, preventing laborious modification of biomolecules. The designed DNA-based logic nanodevices share the same DNA platform and a constant threshold value, showing great potential for application in information processing at the molecular level. Additionally, these devices can stably carry out their logic operations in a biological matrix, indicating that the AgNC/GO-based system can operate in a complicated biological environment. Given the biocompatibility and design flexibility of DNA, this study provides novel outcomes towards the development of label-free intelligent nanodevices. This may open a new path for the application of AgNCs/GO in molecular logic circuits and fluorescence imaging.

Isothermal Amplification for MicroRNA Detection: From the Test Tube to the Cell

MicroRNAs (miRNAs) are a class of small noncoding RNAs that act as pivotal post-transcriptional regulators of gene expression, thus involving in many fundamental cellular processes such as cell proliferation, migration, and canceration. The detection of miRNAs has attracted significant interest, as abnormal miRNA expression is identified to contribute to serious human diseases such as cancers. Particularly, miRNAs in peripheral blood have recently been recognized as important biomarkers potential for liquid biopsy. Furthermore, as miRNAs are expressed heterogeneously in different cells, investigations into single-cell miRNA expression will be of great value for resolving miRNA-mediated regulatory circuits and the complexity and heterogeneity of miRNA-related diseases. Thus, the development of miRNA detection methods, especially for complex clinic samples and single cells is in great demand. In this Account, we will present recent progress in the design and application of isothermal amplification enabling miRNA detection transition from the test tube to the clinical sample and single cell, which will significantly advance our knowledge of miRNA functions and disease associations, as well as its translation in clinical diagnostics. miRNAs present a huge challenge in detection because of their extremely short length (∼22 nucleotides) and sequence homology (even with only single-nucleotide variation). The conventional golden method for nucleic acid detection, quantitative PCR (qPCR), is not amenable to directly detecting short RNAs and hardly enables distinguishing between miRNA family members with very similar sequences. Alternatively, isothermal amplification has emerged as a powerful method for quantification of nucleic acids and attracts broad interest for utilization in developing miRNA assays. Compared to PCR, isothermal amplification can be performed without precise control of temperature cycling and is well fit for detecting short RNA or DNA. We and other groups are seeking methods based on isothermal amplification for detecting miRNA with high specificity (single-nucleotide resolution) and sensitivity (detection limit reaching femtomolar or even attomolar level). These methods have recently been demonstrated to quantify miRNA in clinical samples (tissues, serum, and plasma). Remarkably, attributed to the mild reaction conditions, isothermal amplification can be performed inside cells, which has recently enabled miRNA detection in single cells. The localized in situ amplification even enables imaging of miRNA at the single-molecule level. The single-cell miRNA profiling data clearly shows that genetically identical cells exhibit significant cell-to-cell variation in miRNA expression. The leap of miRNA detection achievements will significantly contribute to its full clinical adoption and translation and give us new insights into miRNA cellular functions and disease associations.

Stimuli-Responsive Self-Assembled DNA Nanomaterials for Biomedical Applications

Stimuli-responsive DNA-based materials represent a major class of remarkable functional nanomaterials for nano-biotechnological applications. In this review, recent progress in the development of stimuli-responsive systems based on self-assembled DNA nanostructures is introduced and classified. Representative examples are presented in terms of their design, working principles and mechanisms to trigger the response of the stimuli-responsive DNA system upon expose to a large variety of stimuli including pH, metal ions, oligonucleotides, small molecules, enzymes, heat, and light. Substantial in vitro studies have clearly revealed the advantages of the use of stimuli-responsive DNA nanomaterials in different biomedical applications, particularly for biosensing, drug delivery, therapy and diagnostic purposes in addition to bio-computing. Some of the challenges faced and suggestions for further development are also highlighted.

Multifunctional Graphene/DNA-Based Platform for the Construction of Enzyme-Free Ternary Logic Gates

In this work, we have successfully realized multivalued logic circuits including ternary INHIBIT and ternary OR logic gates in an enzyme-free condition by integration of graphene oxide and DNA for the first time. Compared to the binary logic gate with two states of "0" and "1", the multivalued logic gate contains three different states of "0", "1", and "2", which can increase the information content in a system and further improve the ability of information processing. Such types of multivalued logic operations provide a wider field of vision toward DNA-based algebra logical operations to make applications more accurate with complexity reduction and accelerate the development of advanced logic gates.

Applying DNA rolling circle amplification in fluorescence imaging of cell surface glycans labeled by a metabolic method

Glycans on the cell surfaces are essential for cellular communication. Metabolically labeling glycans can introduce unnatural sugars into cellular glycans, which can facilitate further labeling. We report herein imaging cell surface glycosylation by using click chemistry and DNA rolling circle amplification (RCA) to improve detection sensitivity. Through the RCA amplification, the image resolution of a cell was significantly improved and much fewer unnatural sugars were used than required previously. The advantage of this method is that it avoids introducing too much unnatural sugar, which can interfere with normal, physiological cell function. Simultaneously, the enhanced fluorescence intensity conveniently facilitates the detection of cells' own biosynthetic glycans by simply using a microplate reader. The results indicate that the metabolically labelling ability is different for different carbohydrates and different cells. Next, the RCA technique was adopted in a fluorescence resonance energy transfer (FRET)-based methodology that facilitated the glycan imaging of specific proteins on the cell surface. This method is broadly applicable to imaging the glycosylation of cellular proteins. Our results highlight the applications of RCA in metabolic glycan labeling, which can be used to monitor the glycosylation status on cells, and study the means by which glycosylation regulates cell function.

Production of dumbbell probe through hairpin cleavage-ligation and increasing RCA sensitivity and specificity by circle to circle amplification

Dumbbell probe (DP) attracts increasing interests in rolling circle amplification (RCA). A universal DP production method through cleavage-ligation of hairpin was proposed and optimized. The production is characterized by restriction endonuclease (RE)-induced cleavage ends ligation. It has the advantage of phosphorylation-free, splint-free and purification-free. To optimize designing, we found that the position of RE cleavage sequence in the stem and the primer position in the loop affected the formation and amplification of DP obviously. Both sticky and blunt ends cleaved by RE produce DP efficiently. Moreover, we introduced this DP into circle to circle (C2C) RCA based on the same cleavage-ligation principle, and acquired high sensitivity. By combining a two-ligation design and the C2C strategy, specificity for detecting let-7 family members was increased extremely. Furthermore, coreaction of different steps facilitated convenient formation and amplification process of DP.

Triplex DNA logic gate based upon switching on/off their structure by Ag(+)/cysteine

The formation of intramolecular triplex DNA can be regulated by Ag(+) and Cys (cysteine), which switch off/on the fluorescence of the oligonucleotides, 5'-TAMRA-TTC TCT TCC TCT TCC TTC TGA CGA CAG TTG ACT CTT CCT TCT CCT TCT CTT-BHQ-2-3' (Oligo 1) and 3'-GAA GGA AGA GGA AGA GAA-5' (Oligo 2). Based on this principle, sensors for Ag(+) and Cys are developed. The sensor for Ag(+) has a linear range of 2.5 nM-40 nM and a detection limit of 1.8 nM, whereas the sensor for Cys has a linear range of 10.0 nM-120.0 nM and a detection limit of 8.2 nM. Furthermore, the fluorescence is reversible with the alternate addition of Ag(+) and Cys. We constructed a DNA logic gate using Ag(+) and Cys as the input, and the fluorescence intensity as the output. The DNA logic gate is simple; moreover, it has a fast response and good reversibility.

DNA Nanotechnology for Precise Control over Drug Delivery and Gene Therapy

Nanomedicine has been growing exponentially due to its enhanced drug targeting and reduced drug toxicity. It uses the interactions where nanotechnological components and biological systems communicate with each other to facilitate the delivery performance. At this scale, the physiochemical properties of delivery systems strongly affect their capacities. Among current delivery systems, DNA nanotechnology shows many advantages because of its unprecedented engineering abilities. Through molecular recognition, DNA nanotechnology can be used to construct a variety of nanostructures with precisely controllable size, shape, and surface chemistry, which can be appreciated in the delivery process. In this review, different approaches that are currently used for the construction of DNA nanostructures are reported. Further, the utilization of these DNA nanostructures with the well-defined parameters for the precise control in drug delivery and gene therapy is discussed.

Molecular logic gates based on DNA tweezers responsive to multiplex restriction endonucleases

Self-assembled DNA tweezers containing four different restriction endonuclease recognition sites were designed and a set of logic gates were constructed.

A universal platform for building molecular logic circuits based on a reconfigurable three-dimensional DNA nanostructure

Molecular logic gates are capable of performing various logic tasks for biomarker detection, disease diagnostics and therapy, and controlling biological progress. Herein, we integrated multiple components of a logic device into a single DNA 3D nano-assembly with a triangular prism structure. Compared with the separate construction of each component in previously reported DNA logic gate systems, such an integrated design strategy made the 3D DNA nanoprism universal for logic gates, it can be reconfigured to execute diverse logic operations. Binary basic logic gates (OR, AND, INHIBIT and XOR), combinatorial gates (INHIBIT-OR), and multi-valued logic gates (ternary INHIBIT gate) were readily achieved by taking this DNA nanoprism as a universal platform. Moreover, a logic gate system for identification of even numbers and odd numbers from natural numbers was established successfully by employing only this single DNA nanoprism and four short single-stranded DNA. The universality of this nanoprism greatly simplified the design of DNA logic gate system. Additionally, this nanoprism was able to perform logic operation steadily in a biological matrix, indicating that this box-like DNA nanostructure applies to logic gates in a complicated environment. This study provided a unique opportunity to design versatile 3D DNA nanostructure-based intelligent nanodevices, which show great potential in biocomputing, multi-parameter sensing, and intelligent disease diagnostics and therapy.