Detection of microRNAs using toehold-initiated rolling circle amplification and fluorescence resonance energy transfer

Multi-enzymatic systems synergize new RCA technique amplified super-long dsDNA from DNA circle

BACKGROUND

In the field of DNA amplification, there are great challenges in the effectively amplify of long-chain amplification, especially amplification up to several hundred kb level.

RESULTS

A novel technique for the unbiased whole genome amplification from a thimbleful of DNA circles, such as low as 10 ng/ 10 μL of the circular cpDNA or low as 5 ng/ 10 μL of the plasmid, is developed, which can amplify an abundance of the whole genome sequences. Specifically, the new technique that combines rolling-amplification and triple-enzyme system presents a tightly controlled process of a series of buffers/reactions and optimized procedures, that applies from the primer-template duplexes to the Elution step. The result of this technique provides a new approach for extending RCA capacity, where it can reach 200 kb from the circular cpDNA amplification and 150 kb from the plasmid DNA amplification, that demonstrates superior breadth and evenness of genome coverage, high reproducibility, small amplification bias with the amplification efficiency.

SIGNIFICANCE AND NOVELTY

This new technique will develop into one of the powerful tools for isothermal DNA amplification in vitro, genome sequencing/analysis, phylogenetic analysis, physical mapping, and other molecular biology applications.

An electrochemical determination strategy for miRNA based on bimetallic nanozyme and toehold-mediated DNA replacement procedure

An electrochemical strategy based on bimetallic nanozyme in collaboration with toehold-mediated DNA replacement effect is proposed for the sensitive determination of miRNA-21. The AuPt nanoparticles (AuPt NPs) are prepared as a catalytic beacon; it shows favorable peroxidase properties with a Michaelis contant (K_m) of 0.072 mM for H₂O₂, which is capable of catalyzing H₂O₂ to induce an intense redox reaction, and causing a measurable electrochemical signal. To further enhance the strength of the signal response, a novel toehold-mediated DNA replacement strategy is employed. DNA strands with specific sequences are modified on electrodes and AuPt NPs, respectively. In the presence of miRNA-21, a cyclic substitution effect is subsequently activated via a specific toehold sequence and leads to a large accumulation of AuPt NPs on the electrodes. Subsequently, a strong signal depending on the amount of miRNA-21 is obtained after adding a small amount of H₂O₂. The analytical range of this determination method is from 0.1 pM to 1.0 nM, and the LOD is 84.1 fM. The spike recoveries for serum samples are 95.0 to 102.4% and the RSD values are 3.7 to 5.8%. The results suggests a promising application of the established method in clinical testing and disease diagnosis.

Recent Progress on Optical Biosensors Developed for Nucleic Acid Detection Related to Infectious Viral Diseases

Optical biosensors have many advantages over traditional analytical methods. They enable the identification of several biological and chemical compounds directly, instantly, and without the need of labels. Their benefits include excellent specificity, sensitivity, compact size, and low cost. In this review, the main focus is placed on the nucleic acid-based optical biosensor technologies, including colorimetric, fluorescence, surface plasmon resonance (SPR), Evanescent-Wave Optical, Fiber optic and bioluminescent optical fibre. The fundamentals of each type of biosensor are briefly explained, and particular emphasis has been placed on the achievements which have been gained in the last decade on the field of diagnosis of infectious viral diseases. Concluding remarks concerning the perspectives of further developments are discussed.

Palindrome-Embedded Hairpin Structure and Its Target-Catalyzed Padlock Cyclization for Label-Free MicroRNA-Initiated Rolling Circle Amplification

Highly sensitive detection of microRNAs (miRNAs) is of great significance in early diagnosis of cancers. Here, we develop a palindrome-embedded hairpin structure and its target-catalyzed padlock cyclization for rolling circle amplification, named PHP-RCA for simplicity, which can be applied in label-free ultrasensitive detection of miRNA. PHP-RCA is a facile system that consists of only an oligonucleotide probe with a palindrome-embedded hairpin structure (PHP). The two ends of PHP were extended as overhangs and designed with the complementary sequences of the target. Hence, the phosphorylated PHP can be cyclized by T4 DNA ligase in the presence of the target that serves as the ligation template. This ligation has formed a palindrome-embedded dumbbell-shaped probe (PDP) that allows phi29 polymerase to perform a typical target-primed RCA on PDP by taking miRNA as a primer, resulting in the production of a lengthy tandem repeat. Benefits from the palindromic sequences and hairpin-shaped structure in padlock double-stranded structures can be infinitely produced during the RCA reaction and provide numerous binding sites for SYBR Green I, a double-stranded dye, achieving a sharp response signal for label-free target detection. We have demonstrated that the proposed system exhibits a good linear range from 0.1 fM to 5 nM with a low detection limit of 0.1 fM, and the non-target miRNA can be clearly distinguished. The advantages of high efficiency, label-free signaling, and the use of only one oligonucleotide component make the PHP-RCA suitable for ultrasensitive, economic, and convenient detection of target miRNAs. This simple and powerful system is expected to provide a promising platform for tumor diagnosis, prognosis, and therapy.

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.

Ultrasensitive fluorescence detection of microRNA through DNA-induced assembly of carbon dots on gold nanoparticles with no signal amplification strategy

An ultrasensitive fluorescence assay strategy on the basis of carbon dots (CDs) and cDNA-modified gold nanoparticles (AuNP-cDNA) was developed for the determination of microRNA-21 (miRNA-21) via internal filtering effect (IFE). Positively charged CDs (PEI-CDs), the fluorophores in IFE, were synthesized via a hydrothermal method using polyethyleneimine (PEI) as surface ligand. The maximum emission wavelength is located at 500 nm under the excitation of 410 nm. AuNPs, the absorbers, were modified with single-stranded DNA (cDNA), which is completely complementary to miRNA-21. The fluorescence of PEI-CDs is quenched due to the assembly of PEI-CDs and AuNPs-cDNA. In the presence of miRNA-21, the hybridization between miRNA-21 and cDNA causes the release of PEI-CDs and the recovery of fluorescence intensity.The fluorescence recovery degree is linearly correlated with the logarithm of miRNA-21 concentration in the range of 1-1000 fM. This method can be applied to determine miRNA-21 in real serum samples, and the detection results are in well agreement with those of qRT-PCR. The determination of miRNA-21 spiked into diluted human serum samples displays satisfactory recovery within the range 88.44-112.7%, which confirmed the reliability for miRNAs detection in real samples.

Label-free and sensitive microRNA detection method based on the locked nucleic acid assisted fishing amplification strategy

Herein, a label free and sensitive miRNA detection method with enhanced practical applicability was developed based on the locked nucleic acid (LNA) assisted repeated fishing amplification strategy. The working mechanism of the proposed method is as follows: 1) a DNA probe (i.e, L-DNA) with LNA bases is immobilized onto the surface of a gold foil. The L-DNA hybridizes with the 3' terminus of the first strands of complementary deoxyribonucleic acid (cDNA) of the target miRNA in the test samples; 2) The protruding 5' terminus of the cDNA serves as a 'fishhook' to repeatedly fish the products of a hybridization chain reaction (HCR) out from a 'reaction tube'; 3) The HCR products can be unloaded from the gold foil into a 'product tube' through temperature-controlled dehybridization; 4) The concentration of the target miRNA is determined based on the fluorescence intensity generated by the addition of SYBR-Green I (SG) into the 'product tube'. The proposed platform was applied to the detection of miRNA-122 in cell lysate samples and obtained quantitative results with accuracy comparable to the quantitative reverse transcription PCR method (qRT-PCR). It is worth pointing out that the proposed platform achieved a limit of detection value of 2.9 fM for miRNA-122 by a simple but effective LNA-assisted repeated fishing amplification strategy instead of complicated enzyme-based amplification techniques. It is reasonable to expect that the proposed method provides a competitive alternative for designing practically applicable, cost-effective and label-free miRNA detection methods.

A novel method for miRNA detection based on target-triggered transcription of a light-up RNA aptamer

We herein describe a novel method for miRNA detection based on target-triggered transcription of a light-up RNA aptamer (TTRApt), consequently producing a highly enhanced fluorescence signal through specific binding of a light-up RNA aptamer to the corresponding dye. Using this strategy, we successfully identified target miRNA down to 59.4 aM with excellent specificity.

Engineered G-Quadruplex-Embedded Self-Quenching Probes Regulate Single Probe-Based Multiplex Isothermal Amplification to Light Road Lamp Probes for Sensitized Determination of microRNAs

Design of oligonucleotide probe-based isothermal amplification with the ability to identify miRNA biomarkers is crucial for molecular diagnostics. In this work, we engineered a miRNA-21-responsive G-quadruplex-embedded self-quenching probe (GE-SQP) that can regulate single probe-based multiplex amplifications. The free GE-SQP is tightly locked in a quenching state with no active G-quadruplexes. Introduction of target miRNA to hybridize with GE-SQP would induce a multiplex isothermal amplification to significantly build a lot of one-bulb-contained road lamp probe (OC-RLP) and two-bulb-contained road lamp probe (TC-RLP) using G-quadruplex as the lamp bulb. When lightened by thioflavin T (ThT), beams of fluorescence were emitted to show the presented miRNA-21. Specially, the whole amplification is only a one probe-involved one-step reaction without any wasted species. The mix-to-detection and all-in amplification behavior allows the sensing system a maximally maintained operation simplicity and high assay performance. In such a way, the detection range of miRNA-21 is from 1 fM to 1 nM with a limit of detection of 0.86 fM. The practicability was demonstrated by determining miRNA-21 from serum samples with acceptable results. We expect that this method can open a new avenue for exploring advanced biosensors with improved analytical performances.

Development of the DNA-based biosensors for high performance in detection of molecular biomarkers: More rapid, sensitive, and universal

The molecular biomarkers are molecules that are closely related to specific physiological states. Numerous molecular biomarkers have been identified as targets for disease diagnosis and biological research. To date, developing highly efficient probes for the precise detection of biomarkers has become an attractive research field which is very important for biological and biochemical studies. During the past decades, not only the small chemical probe molecules but also the biomacromolecules such as enzymes, antibodies, and nucleic acids have been introduced to construct of biosensor platform to achieve the detection of biomarkers in a highly specific and highly efficient way. Nevertheless, improving the performance of the biosensors, especially in clinical applications, is still in urgent demand in this field. A noteworthy example is the Corona Virus Disease 2019 (COVID-19) that breaks out globally in a short time in 2020. The COVID-19 was caused by the virus called SARS-CoV-2. Early diagnosis is very important to block the infection of the virus. Therefore, during these months scientists have developed dozens of methods to achieve rapid and sensitive detection of the virus. Nowadays some of these new methods have been applied for producing the commercial detection kit and help people against the disease worldwide. DNA-based biosensors are useful tools that have been widely applied in the detection of molecular biomarkers. The good stability, high specificity, and excellent biocompatibility make the DNA-based biosensors versatile in application both in vitro and in vivo. In this paper, we will review the major methods that emerged in recent years on the design of DNA-based biosensors and their applications. Moreover, we will also briefly discuss the possible future direction of DNA-based biosensors design. We believe this is helpful for people interested in not only the biosensor field but also in the field of analytical chemistry, DNA nanotechnology, biology, and disease diagnosis.

A sensing system constructed by combining a structure-switchable molecular beacon with nicking-enhanced rolling circle amplification for highly sensitive miRNA detection

A novel amplification assay strategy is developed for the highly sensitive detection of miRNA-21 based on a combination of a structure-switchable molecular beacon with nicking-enhanced rolling circle amplification.

Functional nucleic acid biosensors utilizing rolling circle amplification

Functional nucleic acids regulate rolling circle amplification to produce multiple detection outputs suitable for the development of point-of-care diagnostic devices.

Recent advances in biological detection with rolling circle amplification: design strategy, biosensing mechanism, and practical applications

Rolling circle amplification (RCA) is a simple and isothermal DNA amplification technique that is used to generate thousands of repeating DNA sequences using circular templates under the catalysis of DNA polymerase.

Recent advances of fluorescent biosensors based on cyclic signal amplification technology in biomedical detection

The cyclic signal amplification technology has been widely applied for the ultrasensitive detection of many important biomolecules, such as nucleic acids, proteins, enzymes, adenosine triphosphate (ATP), metal ions, exosome, etc. Due to their low content in the complex biological samples, traditional detection methods are insufficient to satisfy the requirements for monitoring those biomolecules. Therefore, effective and sensitive biosensors based on cyclic signal amplification technology are of great significance for the quick and simple diagnosis and treatment of diseases. Fluorescent biosensor based on cyclic signal amplification technology has become a research hotspot due to its simple operation, low cost, short time, high sensitivity and high specificity. This paper introduces several cyclic amplification methods, such as rolling circle amplification (RCA), strand displacement reactions (SDR) and enzyme-assisted amplification (EAA), and summarizes the research progress of using this technology in the detection of different biomolecules in recent years, in order to provide help for the research of more efficient and sensitive detection methods.

Recent advances in rolling circle amplification-based biosensing strategies-A review

Rolling circle amplification (RCA) is an efficient enzymatic isothermal reaction that using circular probe as a template to generate long tandem single-stranded DNA or RNA products under the initiation of short DNA or RNA primers. As a simplified derivative of natural rolling circle replication which synthesizes copies of circular nucleic acids molecules such as plasmids, RCA amplifies the circular template rapidly without thermal cycling and finds various applications in molecular biology. Compared with other amplification strategies, RCA has many obvious advantages. Firstly, because of the strict complementarity required in ligation of a padlock probe, it endows the RCA reaction with high specificity and can even be utilized to distinguish single base mismatches. Secondly, through the introduction of multiple primers, exponential amplification can be achieved easily and leads to a good sensitivity. Thirdly, RCA products can be customized by manipulating circular templates to generate functional nucleic acids such as aptamer, DNAzymes and restriction enzyme sites. Moreover, the RCA has good biocompatibility and is especially suitable for in situ detection. Therefore, RCA has attracted considerable attention as an efficient and potential tool for highly sensitive detection of biomarkers. Herein, we comprehensively introduce the fundamental principles of RCA technology, summarize it from three aspects including initiation mode, amplification mode and signal output mode, and discuss the recent application of RCA-based biosensor in this review.