Stimuli-responsive incremental DNA machine auto-catalyzed CRISPR-Cas12a feedback amplification permits ultrasensitive molecular diagnosis of esophageal cancer-related microRNA

Development of new diagnostic methods is essential for disease diagnosis and treatment. In this work, we present a stimuli-responsive incremental DNA machine auto-catalyzed CRISPR-Cas12a (SRI-DNA machine/CRISPR-Cas12a) feedback amplification for ultrasensitive molecular detection of miRNA-21, which is an important biomarker related closely to the initiation and development of cancers, such as esophageal cancer. Strategically, the powerful SRI-DNA machine and efficient trans-cleavage activity of the CRISPR-Cas12a system are ingeniously integrated via a rationally designed probe termed as stem-elongated functional hairpin probe (SEF-HP). The SRI-DNA machine begins with the target miRNA, the trigger of the reaction, binding complementarily to the SEF-HP, followed by autonomously performed mechanical strand replication, cleavage, and displacement circuit at multiple sites. This conversion process led to the amplified generation of numerous DNA activators that are complementary with CRISPR RNA (CrRNA). Once formed the DNA activator/CrRNA heteroduplex, the trans-cleavage activity of the CRISPR-Cas12a was activated to nonspecific cleavage of single-stranded areas of a reporter probe for fluorescence emission. Under optimal conditions, the target miRNA can be detected with a wide linear range and an excellent specificity. As a proof-of-concept, this SRI-DNA machine/CRISPR-Cas12a feedback amplification system is adaptable and scalable to higher-order artificial amplification circuits for biomarkers detection, highlighting its promising potential in early diagnosis and disease treatment.

Harnessing intermolecular G-quadruplex-based spatial confinement effect for accelerated activation of CRISPR/Cas12a empowers ultra-sensitive detection of PML/RARA fusion genes

Accurate detection and classification of the three isoforms of PML/RARA genomic fragments are crucial for predicting disease progression, stratifying risk, and administering precise drug therapies in acute promyelocytic leukemia (APL). In this study, we have developed a highly specific nucleic acid detection platform capable of quantifying the long isoform of the three main PML-RARA isoforms at a constant temperature. This platform integrates the strengths of the CRISPR/Cas12a nuclease-based method and the rolling circle amplification (RCA) technique. Notably, the RCA-assisted CRISPR/Cas12a trans-cleavage system incorporates a spatial confinement effect by utilizing intermolecular G-quadruplex structures. This innovative design effectively enhances the local concentration of CRISPR/Cas12a, thereby accelerating its cleaving efficiency towards reporter nucleic acids and enabling the detection of PML/RARA fusion gene expression through spectroscopy. The robust detection of PML/RARA fusion gene from human serum samples validates the reliability and potential of this platform in the screening, diagnosis, and prognosis of APL cases. Our findings present an approach that holds significant potential for the further development of the robust CRISPR/Cas sensor system, offering a rapid and adaptable paradigm for APL diagnosis.

Recent advances in cascade isothermal amplification techniques for ultra-sensitive nucleic acid detection

Nucleic acid amplification techniques have always been one of the hot spots of research, especially in the outbreak of COVID-19. From the initial polymerase chain reaction (PCR) to the current popular isothermal amplification, each new amplification techniques provides new ideas and methods for nucleic acid detection. However, limited by thermostable DNA polymerase and expensive thermal cycler, PCR is difficult to achieve point of care testing (POCT). Although isothermal amplification techniques overcome the defects of temperature control, single isothermal amplification is also limited by false positives, nucleic acid sequence compatibility, and signal amplification capability to some extent. Fortunately, efforts to integrating different enzymes or amplification techniques that enable to achieve intercatalyst communication and cascaded biotransformations may overcome the corner of single isothermal amplification. In this review, we systematically summarized the design fundamentals, signal generation, evolution, and application of cascade amplification. More importantly, the challenges and trends of cascade amplification were discussed in depth.

Bidirectional motivated bimodal isothermal strand displacement amplifier with a table tennis-like movement for the ultrasensitive fluorescent and colorimetric detection of depression-related microRNA

An increasing number of studies have highlighted the potential of microRNAs (miRNAs) as physiological indicators of major depressive disorder (MDD). Herein, we developed a bidirectional-motivated bimodal isothermal strand displacement amplifier (BB-ISDA) for the ultrasensitive fluorescent and colorimetric detection of MDD-related miRNA-132. In the BB-ISDA system, a pair of functionalized hairpin probes (HP1 and HP2) with nicking recognition sites are designed to recognize target miRNA. The recognition of target miRNA by HP1 (or HP2) generates copious numbers of nicked triggers by HP1 (or HP2)-based ISDA to recognize HP2 (or HP1) by autonomous strand polymerization, cleavage, and displacement, which in turn induces the subsequent generation of copious numbers of nicked G-quadruplex triggers by HP2 (or HP1)-based ISDA to recognize HP1 (or HP2) along a same line. After many cycles, this bidirectional motivated table-tennis-like movement amplifies the fluorescent signal from HP1 and the colorimetric signal from HP2, simultaneously. The dual-signal output pattern was cross-validated for sensing miRNA-132. Each of the detection modal shows the capability for qualitative and quantitative detection of miRNA-132 with high sensitivity and specificity. The adaptability of the bimodal mechanism was verified via the detection of target miRNA-132 from clinical human blood samples. We envision that this BB-ISDA with dual-signal output for accurate and reliable analysis of miRNA is promising for the molecular diagnosis of human mental diseases.

A highly-efficient 3D DNAzyme motor for sensitive biosensing analysis

Herein, driven by the need of highly-efficient DNAzyme-amplified detection strategy, a novel 3D DNAzyme motor was designed as a biosensor platform for realizing sensitive detection of target DNA. The 3D DNAzyme motor was composed of target-activated DNAzyme nanowires and substrates H1-Fc that co-immobilized on Au@Fe₃O₄ nanoparticles (Au@Fe₃O₄NP_S) surface, possessing high local concentration of DNA reactants and shortened distance between DNAzyme and substrates for enhancing electrochemical signal. Compared with traditional DNAzyme-powered machines, the target-activated DNAzyme nanowires of 3D DNAzyme motor had greater flexibility and more powerful cleavage capability without troublesome sequence optimization, which overcame the space limitation and simultaneously interacted with adjacent and distant substrates H1-Fc to output a large amount of cleavage products with high signal response. Therefore, on account of the above-mentioned merits of nanoparticles localization DNA design and DNAzyme nanowires, the reported 3D DNAzyme motor ingeniously overcame many defects existing in traditional DNAzyme-amplified detection strategies such as low reactants concentration, limited flexibility of DNAzyme and small DNAzyme swing range, realizing the sensitive detection of target DNA with a detection limit of 1.7 fM ranging from 5 fM to 50 nM. Impressively, the 3D DNAzyme motor here presented a new strategy to achieve effective DNAzyme signal amplification and provided a reference for the assembly of various and functional 3D DNA machines in the future.

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.

Structure and function encoding of a bidirectional activatable synergetic DNA machine for speeded and ultrasensitive determination of microRNAs

This work describes the unique design of a bidirectional activatable synergetic DNA machine (BAS-DNA machine) for speeded and ultrasensitive determination of microRNA-21 (miR-21), a well-known biomarker for biomedical research and early diagnosis of lung cancer. The BAS-DNA machine is composed by a pair of track strands (Track 1 and Track 2) encoding with two regions in the opposite direction for miR-21 recognition. Introduction of miR-21 can hybridize either with Track 1 or with Track 2 to activate the BAS-DNA machine with a synergistic effect for speeded amplifying the fluorescence signal. Moreover, compared with common DNA machine with only one switch for exogenous target recognition, the BAS-DNA machine with two switches for miR-21 binding allows the speeded and strong operation of the autonomous strand scission, replication, and displacement on Track 1 and Track 2 simultaneously. This behavior makes the BAS-DNA machine powerful for ultrasensitive, specific, and fast screening of miR-21 even from real biological samples, and the fluorescence signal was found to be linear from 1 pM to 10 nM with a detection limit of 703.6 fM. We envision this BAS-DNA machine with its superior assay performance will provide a new avenue for simple, sensitive, and affordable biomedical assays.

Construction of a dual-functional dumbbell probe-based fluorescent biosensor for cascade amplification detection of miRNAs in lung cancer cells and tissues

We develop a dual-functional dumbbell probe-based fluorescent biosensor for cascade amplification detection of miRNAs in lung cancer cells and tissues by integrating primer exchange reaction (PER) with CRISPR-Cas12a system. This...

Activation of palindromes on a degradable modular grafting probe enables ultrasensitive detection of microRNAs

This work describes a single-stranded degradable modular grafting probe for analyzing microRNA-21. In the system, the exonuclease activity of phi29 polymerase restrains the SYBR Green I/ssDNA induced background. The palindrome activation caused remarkable target fluorescence. The detection limit was achieved as 0.26 fM, showing potential in biochemical analysis.

Periodically programmed building and collapse of DNA networks enables an ultrahigh signal amplification effect for ultrasensitive nucleic acids analysis

ANALYSIS

of molecular species is needed for applications in diagnosis of infections and genetic diseases. Herein, we demonstrate a target DNA-responsive ultrahigh fluorescence signal-on DNA amplification system via periodically programmed building and collapse of DNA networks. In this system, a pair of oligonucleotides of padlock probe (PP) and palindromic hairpin probe (PHP) are utilized. The presence of target DNA firstly hybridizes with PP, allowing the occurrence of rolling circle amplification (RCA) to produce RCA products with tandem repeats in abundance to bind and unfold numbers of PHPs. The conformational change of PHPs enables the building of DNA networks via the intermolecular palindrome pairing, but then makes the DNA networks collapsed via the palindrome-induced strand displacement polymerization. The displaced RCA products are dynamically reused to undergo periodically programmed multiple rounds of DNA network building and collapse. Depend on the bidirectional DNA assembly and disassembly, a strikingly amplified fluorescence can be collected to ultrasensitive and specific detection of target DNA. The practicability has been demonstrated by evaluating target-spiked human serum, saliva, and urine samples with acceptable recoveries and reproducibility. Therefore, this newly explored method opens a promising avenue for the detection of nucleic acids with low abundance in biochemical analysis and diseases diagnosis.

A simple, one-pot and ultrasensitive DNA sensor via Exo III-Assisted target recycling and 3D DNA walker cascade amplification

Rapid, sensitive, and user-friendly nucleic acid detection is of growing importance in early clinical diagnosis. Here, we construct a simple, one-pot and ultrasensitive DNA sensor via exonuclease III (Exo III)-assisted target recycling amplification (ERA) combined with 3D DNA walker cascade amplification. In the presence of single-stranded DNA target, the ERA process is activated to generate numerous walker strands (WS). Thereafter, Exo III-powered WSs autonomously move along magnetic bead (MB)-based 3D track to release numerous AgNCs into the supernatant as an amplified signal output. This biosensor had a low detection limit of 18 fM and an analytical range of 40 fM to 1 pM. Furthermore, the practical application potential of this biosensor was also confirmed by the spiking experiments of p53 into human serum and urine samples.

A molecular device: A DNA molecular lock driven by the nicking enzymes

As people are placing more and more importance on information security, how to realize the protection of information has become a hotspot of current research. As a security device, DNA molecular locks have great potential to realize information protection at the molecular level. However, building a highly secure molecular lock is still a serious challenge. Therefore, taking advantage of the DNA strand displacement and enzyme control technology, we constructed a molecular lock with a self-destructive mechanism. This molecular lock is mainly composed of logic circuits and takes nicking enzymes as inputs. To build this molecular lock, we first constructed a series of cascade circuits, including a YES–YES cascade circuit and a YES–AND cascade circuit. Then, an Inhibit logic gate was constructed to explore the inhibitory properties between different combinations of two nicking enzymes. Finally, using the characteristics of mutual inhibition between several enzymes, a DNA molecular lock driven by three nicking enzymes was constructed. In this molecular device, only the correct sequence of nicking enzymes can be input to ensure the normal operation of the molecular lock. Once the wrong password is entered, the device will be destroyed and cannot be recovered, which effectively prevents intruders from cracking the lock through exhaustive methods. The molecular lock has the function of simulating an electronic keyboard, which can realize the protection of information at the molecular level, and provides a new implementation method for building more advanced and complex molecular devices.

Intense electrochemiluminescence from an organic microcrystal accelerated H2O2-free luminol system for microRNA detection

The 9,10-diphenylanthracene microcrystals (DPA MCs) was developed as a novel coreactant accelerator for H₂O₂-free luminol system, which was attributed to the efficiently catalysis towards dissolved O₂ for more reactive oxygen species generation.