Tuning Toehold Length and Temperature to Achieve Rapid, Colorimetric Detection of DNA from the Disassembly of DNA-Gold Nanoparticle Aggregates

A rational design of a cascaded DNA circuit for nanoparticle assembly and its application in the discrimination of single-base changes

In the field of dynamic DNA nanotechnology, a designable DNA assembly circuit based on the toehold-mediated strand displacement reaction has demonstrated its ability to program the self-assembly of nanoparticles. However, the laborious work for the modification of nanoparticles with oligonucleotides, the long assembly time, and the circuit leakage prevent its further and scalable applications. To this end, cascaded circuits composed of two recycling circles are rationally designed in this study. Through the pre-initiation of the autonomous reaction, nanoparticles as sensing elements and no additionally exposed bases on the substrate hybridized with fuel strand, the real assembly time and signal leakage for diagnostic application can be effectively reduced and eliminated, thus offering a promising methodology for future point-of-care testing.

Reversible assembly-disassembly of plasmonic spherical nucleic acids enabling temperature-self-controllable and biomarker-activatable photothermal effects

Since the photothermal heating of plasmonic spherical nucleic acids (pSNAs) depends on the self-assembly level and melting temperature (T_m), a temperature-self-controllable and biomarker-activatable photothermal effect in vivo was thus achieved using the T_m-dependent assembly-disassembly of pSNAs.

Acceleration of DNA Hybridization Chain Reactions on 3D Nanointerfaces of Magnetic Particles and Their Direct Application in the Enzyme-Free Amplified Detection of microRNA

Accelerated DNA hybridization chain reactions (HCRs) using DNA origami as a scaffold have received considerable attention in dynamic DNA nanotechnology. However, tailor-made designs are essential for DNA origami scaffolds, hampering the practical application of accelerated HCRs. Here, we constructed the semilocalized HCR and localized HCR systems using magnetic beads (MBs) as a simple scaffold to explore them for the enzyme-free miR-21 detection. The semilocalized HCR system relied on free diffusing one hairpin DNA and MBs immobilized with another hairpin DNA, and the localized HCR system relied on MBs coimmobilized with two hairpin DNAs. We demonstrated that the DNA density on MBs plays a critical role in HCR kinetics and limit of detection (LOD). Among semilocalized HCR systems, MBs with a medium DNA density showed a faster HCR and lower LOD (10 pM) than the diffusive (conventional) HCR system (LOD: 86 pM). In contrast, the HCR further accelerated for the localized HCR systems as the DNA density increased. The localized HCR system with the highest DNA density showed the fastest HCR and the lowest LOD (533 fM). These findings are of great importance for the rational design of accelerated HCRs using simple scaffolds for practical applications.

Multiplexed and single-cell detection of microRNA with plasmonic nanoparticle assemblies

We present a label-free, low cost, and miniatured biosensing platform based on the disassembly of core-satellite plasmonic nanoparticle assemblies. The rapid and selective detection of an exemplary nucleic acid biomarker, has-miRNA-210-3p, was achieved via the strand displacement nucleic acid reaction. Target binding leads to dehybridization of the DNA linkers and changes in the scattering properties of nanostructures as monitored by darkfield microscopy. We demonstrate the ability to detect microRNA expunged from single cells and the potential to multiplex discrete assemblies to enable diverse biological applicability. The work may help translate the applicability of microRNA as diagnostic biomarkers, quantitate their abundance in the microenvironment, and facilitate the study of their correlation or causation to other biomolecules at the single-cell level.

Reverse transcription lesion-induced DNA amplification: An instrument-free isothermal method to detect RNA

One challenge in point-of-care (POC) diagnostics is the lack of room-temperature methods for RNA detection based on enzymatic amplification and visualization steps. Here we perform reverse transcription lesion-induced DNA amplification (RT-LIDA), an isothermal amplification method that only requires T4 DNA ligase. RT-LIDA involves the RNA-templated ligation of DNA primers to form complementary DNA (cDNA) followed by toehold-mediated strand displacement of the cDNA and its exponential amplification via our isothermal ligase chain reaction LIDA. Each step is tuned to proceed at 28 °C, which falls within the range of global room temperatures. Using RT-LIDA, we can detect as little as ∼100 amol target RNA and can distinguish RNA target from total cellular RNA. Finally, we demonstrate that the resulting DNA amplicons can be detected colorimetrically, also at room temperature, by rapid, target-triggered disassembly of DNA-modified gold nanoparticles. This integrated amplification/detection platform requires no heating or visualization instrumentation, which is an important step towards realizing instrument-free POC testing.

Simple Single-Legged DNA Walkers at Diffusion-Limited Nanointerfaces of Gold Nanoparticles Driven by a DNA Circuit Mechanism

We designed and prepared a single-legged DNA walker that relies on the creation of a simple diffusion-limited nanointerface on a gold nanoparticle (DNA/PEG⁽⁺⁾-GNP) track co-modified with fluorescence-labeled hairpin DNA and poly(ethylene glycol) (PEG) containing a positively charged amino group at one end. The movement of our single-legged DNA walker is driven by an enzyme-free DNA circuit mechanism through cascading toehold mediated DNA displacement reactions (TMDRs) using fuel hairpin DNAs. The acceleration of TMDRs was observed for the DNA/PEG⁽⁺⁾-GNP track through electrostatic interaction between the positively charged track and negatively charged DNAs, resulting in the acceleration of the DNA circuit and amplification of the fluorescence signal. Furthermore, the DNA/PEG⁽⁺⁾-GNP track allowed autonomous and persistent movement of a walker DNA strand on the same GNP track, because the intraparticle DNA circuit occurred preferentially by preventing diffusion of the negatively charged free walker DNA strand from near the positively charged tracks into solution through electrostatic interaction. Based on comparative study of kinetics of TMDRs and DNA walking behaviors, it is to be noted that the DNA/PEG⁽⁺⁾-GNP track showed the fastest DNA circuit reaction (walking rate) and the largest number of steps taken by the walker DNA strand compared to other GNP tracks with varying nanointerfaces that differ in terms of their type of charges (no and negative charges), density of positive charges, and number of hairpin DNAs per GNP track. These facts reveal that the positive charges on the GNP track play an important role in the acceleration of the DNA circuit, as well as the successful walking motion of the single-legged DNA strand. By using the fluorescence signal amplification functions, our single-legged DNA walker could be applied directly and successfully to enzyme-free miRNA-detection systems. The miRNA-detection system provided higher discrimination of other mismatched miRNAs and higher sensitivity (the lowest LOD: 4.0 pM) when compared to other miRNA-detection systems based on other GNP tracks without positive charges. Unlike existing single-legged DNA walkers, our single-legged DNA walkers do not require complex processes, such as immobilization of the walker DNA strand on the tracks and precise adjustment of the sequence of walker DNA. Therefore, our strategy, based on the creation of diffusion-limited nanointerfaces, has enormous potential for the applications of single-legged DNA walkers to biosensors, bioimaging, and computing.

Performance Evaluation of Surface-Enhanced Raman Scattering-Polymerase Chain Reaction Sensors for Future Use in Sensitive Genetic Assays

We report a surface-enhanced Raman scattering (SERS)-based polymerase chain reaction (PCR) assay platform for the sensitive and rapid detection of a DNA marker (pagA) of Bacillus anthracis. Real-time quantitative PCR (RT-qPCR) has been recently considered a gold standard for the quantitative evaluation of a target gene, but it still suffers from the problem of a long thermocycling time. To address this issue, we developed a conceptually new SERS-PCR platform and evaluated its performance by sequentially measuring the Raman signals of B. anthracis DNA after the completion of different thermocycling numbers. According to our experimental data, SERS-PCR has lower limits of detection (LODs) than RT-qPCR under the small cycle number of 20. Particularly, it was impossible to detect a target DNA amplicon using RT-qPCR before the number of cycles reached 15, but SERS-PCR enabled DNA detection after only five cycles with an LOD value of 960 pM. In addition, the dynamic range for SERS-PCR (0.1-1000 pM) is wider than that for RT-qPCR (150-1000 pM) under the same condition. We believe that this SERS-PCR technique has a strong potential to be a powerful tool for the rapid and sensitive diagnosis of infectious diseases in the near future.

DNA-Functionalized Plasmonic Nanomaterials for Optical Biosensing

Plasmonic nanomaterials, especially Au and Ag nanomaterials, have shown attractive physicochemical properties, such as easy functionalization and tunable optical bands. The development of this active subfield paves the way to the fascinating biosensing platforms. In recent years, plasmonic nanomaterials-based sensors have been extensively investigated because they are useful for genetic diseases, biological processes, devices, and cell imaging. In this account, a brief introduction of the development of optical biosensors based on DNA-functionalized plasmonic nanomaterials is presented. Then the common strategies for the application of the optical sensors are summarized, including colorimetry, fluorescence, localized surface plasmon resonance, and surface-enhanced resonance scattering detection. The focus is on the fundamental aspect of detection methods, and then a few examples of each method are highlighted. Finally, the opportunities and challenges for the plasmonic nanomaterials-based biosensing are discussed with the development of modern technologies.

Gold nanomaterials as key suppliers in biological and chemical sensing, catalysis, and medicine

BACKGROUND

Gold nanoparticles (AuNPs) with unique physicochemical properties have received a great deal of interest in the field of biological, chemical and biomedical implementations. Despite the widespread use of AuNPs in chemical and biological sensing, catalysis, imaging and diagnosis, and more recently in therapy, no comprehensive summary has been provided to explain how AuNPs could aid in developing improved sensing and catalysts systems as well as medical settings.

SCOPE OF REVIEW

The chemistry of Au-based nanosystems was followed by reviewing different applications of Au nanomaterials in biological and chemical sensing, catalysis, imaging and diagnosis by a number of approaches, and finally synergistic combination therapy of different cancers. Afterwards, the clinical impacts of AuNPs, future application of AuNPs, and opportunities and challenges of AuNPs application were also discussed.

MAJOR CONCLUSIONS

AuNPs show exclusive colloidal stability and are considered as ideal candidates for colorimetric detection, catalysis, imaging, and photothermal transducers, because their physicochemical properties can be tuned by adjusting their structural dimensions achieved by the different manufacturing methods.

GENERAL SIGNIFICANCE

This review provides some details about using AuNPs in sensing and catalysis applications as well as promising theranostic nanoplatforms for cancer imaging and diagnosis, and sensitive, non-invasive, and synergistic methods for cancer treatment in an almost comprehensive manner.

Chemically Fueled Plasmon Switching of Gold Nanorods by Single-Base Pairing of Surface-Grafted DNA

The interactions between metal ions and biomolecules are crucial to various bioprocesses. Development of plasmon switching nanodevices that exploit these molecular interactions is of fundamental and technological interest. Here, we show plasmon switching based on rapid aggregation/dispersion of double-stranded DNA-modified gold nanorods (dsDNA-AuNRs) that exhibit colloidal behaviors depending on pairing/unpairing of the terminal bases. The dsDNA-AuNRs bearing a thymine-thymine (T-T) mismatch at the penultimate position undergo spontaneous non-cross-linking aggregation in the presence of Hg²⁺ due to T-Hg-T base pairing. Inversely, the subsequent addition of cysteine (Cys) gives rise to the removal of Hg²⁺ from the T-Hg-T base pair to reproduce the T-T mismatch, resulting in stable dispersion of the dsDNA-AuNRs. The chemical-responsive plasmon switch allows for the rapid and repeatable cycles at room temperature. The validity of the present method is further exemplified by developing another plasmon switch fueled by Ag⁺ and Cys by installing the Ag⁺-binding DNA sequence in the dsDNA-AuNR.

Facile Strategy for Visible Disassembly of Spherical Nucleic Acids Programmed by Catalytic DNA Circuits

The programmable toehold-mediated DNA-strand-displacement reaction has demonstrated its extraordinary capability in driving the spherical nucleic acid assembly. Here, a facile strategy of integrating a DNA-strand-displacement-based DNA circuit with a universal spherical nucleic acid aggregate system was developed for the visible disassembly of spherical nucleic acids. This integrated system exhibited rapid colorimetric response and good sensitivity in the disassembly reaction and demonstrated its capability in the application of single nucleotide polymorphism discrimination. Moreover, an OR logic gate used for multiplex detection was constructed through combining the fixed spherical nucleic acid disassembly system with two DNA circuits. This strategy will have great potential in the fabrication of a portable low-cost DNA diagnostic kit, and it is also a very promising method to be used in other applications, such as complex DNA networks and programmable phase transformation of nanoparticle superlattices.

Non-Cross-Linking Aggregation of DNA-Carrying Polymer Micelles Triggered by Duplex Formation

Colloidal behaviors of particles functionalized with biomolecules are generally complicated. This study describes that colloidal behaviors of double-stranded (ds) DNA-carrying polymer micelles are well controlled by altering the molar ratio of single-stranded (ss) DNA moiety in the dsDNA shell. ssDNA-carrying micelles composed of a poly( N-isopropylacrylamide) (PNIPAAm) core surrounded by a dense shell of ssDNAs were prepared through self-assembly of PNIPAAm grafted with ssDNA by incubating its solution above the lower critical solution temperature. Spontaneous, non-cross-linking aggregation of the micelles was triggered by DNA duplex formation on the surface. Comparison of the critical coagulation concentration of NaCl among a series of the DNA-carrying micelles revealed the relationship between the helical structure of the surface-bound DNA and the colloidal stability of the micelles. The electrophoretic mobility analysis of the micelles indicated that the duplex formation reduced the structural flexibility of the surface-bound DNA, thereby decreasing the interparticle entropic repulsion. It is also suggested that the augmented rigidity of the surface-bound DNA increases the number of terminal base pairs facing the solvent, which could lead to multiple blunt-end stacking interaction among the micelles. Therefore, small DNA molecules could be considered unique surface-modifiers capable of controlling interactions between the surfaces of materials.

Ultrasensitive optical biosensor for detection of miRNA-155 using positively charged Au nanoparticles

An ultrasensitive optical biosensor for microRNA-155 (miR-155) was developed to diagnose breast cancer at early stages. At first, the probe DNA covalently bind to the negatively charged gold nanoparticles (citrate-capped AuNPs). Then, the target miR-155 electrostatically adsorb onto the positively charged gold nanoparticles (polyethylenimine-capped AuNP) surface. Finally, by mixing citrate-capped AuNP/probe and polyethylenimine-capped AuNP/miR-155, hybridization occurs and the optical signal of the mixture give a measure to quantify the miR-155 content. The proposed biosensor is able to specify 3-base-pair mismatches and genomic DNA from target miR-155. The novelty of this biosensor is in its ability to trap the label-free target by its branched positively charged polyethylenimine. This method increases loading the target on the polyethylenimine-capped AuNPs' surface. So, proposed sensor enables miR-155 detection at very low concentrations with the detection limit of 100 aM and a wide linear range from 100 aM to 100 fM.

Nanotechnology-Enhanced No-Wash Biosensors for in Vitro Diagnostics of Cancer

In vitro biosensors have been an integral component for early diagnosis of cancer in the clinic. Among them, no-wash biosensors, which only depend on the simple mixing of the signal generating probes and the sample solution without additional washing and separation steps, have been found to be particularly attractive. The outstanding advantages of facile, convenient, and rapid response of no-wash biosensors are especially suitable for point-of-care testing (POCT). One fast-growing field of no-wash biosensor design involves the usage of nanomaterials as signal amplification carriers or direct signal generating elements. The analytical capacity of no-wash biosensors with respect to sensitivity or limit of detection, specificity, stability, and multiplexing detection capacity is largely improved because of their large surface area, excellent optical, electrical, catalytic, and magnetic properties. This review provides a comprehensive overview of various nanomaterial-enhanced no-wash biosensing technologies and focuses on the analysis of the underlying mechanism of these technologies applied for the early detection of cancer biomarkers ranging from small molecules to proteins, and even whole cancerous cells. Representative examples are selected to demonstrate the proof-of-concept with promising applications for in vitro diagnostics of cancer. Finally, a brief discussion of common unresolved issues and a perspective outlook on the field are provided.

Disulfide-induced self-assembled targets: A novel strategy for the label free colorimetric detection of DNAs/RNAs via unmodified gold nanoparticles

A modified non-cross-linking gold-nanoparticles (Au-NPs) aggregation strategy has been developed for the label free colorimetric detection of DNAs/RNAs based on self-assembling target species in the presence of thiolated probes. Two complementary thiol- modified probes, each of which specifically binds at one half of the target introduced SH groups at both ends of dsDNA. Continuous disulfide bond formation at 3' and 5' terminals of targets leads to the self-assembly of dsDNAs into the sulfur- rich and flexible products with different lengths. These products have a high affinity for the surface of Au-NPs and efficiently protect the surface from salt induced aggregation. To evaluate the assay efficacy, a small part of the citrus tristeza virus (CTV) genome was targeted, leading to a detection limit of about 5 × 10-9 mol.L-1 over a linear ranged from 20 × 10-9 to 10 × 10-7 mol.L-1. This approach also exhibits good reproducibility and recovery levels in the presence of plant total RNA or human plasma total circulating RNA extracts. Self-assembled targets can be then sensitively distinguished from non-assembled or mismatched targets after gel electrophoresis. The disulfide reaction method and integrating self-assembled DNAs/RNAs targets with bare AuNPs as a sensitive indicator provide us a powerful and simple visual detection tool for a wide range of applications.

An Efficient Particle-Based DNA Circuit System: Catalytic Disassembly of DNA/PEG-Modified Gold Nanoparticle-Magnetic Bead Composites for Colorimetric Detection of miRNA

An efficient particle-based DNA circuit system for a new colorimetric miRNA assay is designed and devised based on a catalytic disassembly strategy through a target miRNA-triggered DNA circuit mechanism. The new particle-based DNA circuit system shows a rapid color change as well as significant improvement of sensitivity without need for other enzymes or instruments.