Binary detection of protein and nucleic acid enabled cancer diagnosis through branched hybridization chain reaction

On-site detection of OTA and AFB1 based on branched hybridization chain reaction coupled with lateral flow assay

Mycotoxins are widely prevalent in various agricultural commodities, whose excessive consumption can pose significant risks to human health. In this study, we developed a facile mycotoxin detection platform based on branched hybridization chain reaction coupled with lateral flow assay. Ochratoxin A/Aflatoxin B1 bind to aptamers triggering the release of initiators, which leads to bHCR amplification and forms three-dimensional dendritic DNA nanostructures. Using the functionalized quantum dots as a fluorescent label, by leveraging smartphones and handheld ultraviolet lamps, the qualitative and quantitative detection of OTA and AFB1 can be achieved with a significantly enhanced sensitivity level, surpassing that of commercial test strips by 2-3 orders of magnitude. The visual detection limits for OTA and AFB1 were 30 pg/mL and 4 pg/mL, respectively. This approach eliminates the necessity for enzyme catalysis or the preparation and purification of antibodies and/or hapten, thereby reducing testing expenses and streamlining operational procedures. Moreover, substituting aptamer and nucleic acid sequences can effectively expand the scope of detection targets. Consequently, the as-proposed strategy exhibits great potential as a versatile technique, suitable for various analytical scenarios due to its sensitivity, accuracy, simplicity, and portability.

Dumbbell Dual-Hairpin Triggered DNA Nanonet Assembly for Cascade-Amplified Sensing of Exosomal MicroRNA

Exosomal microRNAs (miRNAs) are valuable biomarkers closely associated with cancer progression. Therefore, sensitive and specific exosomal miRNA biosensing has been employed for cancer diagnosis, prognosis, and prediction. In this study, a miRNA-based DNA nanonet assembly strategy is proposed, enabling the biosensing of exosomal miRNAs through dumbbell dual-hairpin under isothermal enzyme-free conditions. This strategy dexterously designs a specific dumbbell dual-hairpin that can selectively recognize exosomal miRNA, inducing conformational changes to cascade-generated X-shaped DNA structures, facilitating the extension of the X-shaped DNA in three-dimensional space, ultimately forming a DNA nanonet assembly. On the basis of the target miRNA, our design enriches the fluorescence signal through the cascade assembly of DNA nanonet and realizes the secondary signal amplification. Using exosomal miR-141 as the target, the resultant fluorescence sensing demonstrates an impressive detection limit of 57.6 pM and could identify miRNA sequences with single-base variants with high specificity. Through the analysis of plasma and urine samples, this method effectively distinguishes between benign prostatic hyperplasia, prostate cancer, and metastatic prostate cancer. Serving as a novel noninvasive and accurate screening and diagnostic tool for prostate cancer, this dumbbell dual-hairpin triggered DNA nanonet assembly strategy is promising for clinical applications.

An approach for state differentiation in nucleic acid circuits: Application to diagnostic DNA computing

BACKGROUND

Differentiating between different states in nucleic acid circuits is crucial for various biological applications. One approach, there is a requirement for complicated sequential summation, which can be excessive for practical purposes. By selectively labeling biologically significant states, this study tackles the issue and presents a more cost-effective and streamlined solution. The challenge is to efficiently distinguish between different states in a nucleic acid circuit.

RESULTS

An innovative method is introduced in this study to distinguish between states in a nucleic acid circuit, emphasizing the biologically relevant ones. The circuit comprises four DNA logic gates and two detection modules, one for determining fetal gender and the other for diagnosing X-linked genetic disorders. The primary module generates a G-quadruplex DNAzyme when activated by specific biomarkers, which leads to a distinct colorimetric signal. The secondary module responds to hemophilia and choroideremia biomarkers, generating one or two DNAzymes. The absence of female fetus indicators results in no DNAzyme or color change. The circuit can differentiate various fetal states by producing one to four active DNAzymes in response to male fetus biomarkers. A single-color solution for state differentiation is provided by this approach, which promises significant advancements in DNA computing and diagnostic applications.

SIGNIFICANCE

The innovative approach used in this study to distinguish states in nucleic acid circuits holds great significance. By selectively labeling biologically relevant states, circuit design is simplified and complexity is reduced. This advancement enables cost-effective and efficient diagnostic applications and contributes to DNA computing, providing a valuable solution to a fundamental problem.

Multiplexed miRNA and Protein Analysis Using Digital Quantitative PCR in Microwell Arrays

Proteins and microRNAs (miRNAs) act in tandem within biological pathways to regulate cellular functions, and their misregulation has been correlated to numerous diseases. Because of their interconnectedness, both miRNAs and proteins must be evaluated together to obtain accurate insights into the molecular pathways of pathogenesis. However, few analytical techniques can measure both classes of biomolecules in parallel from a single biological sample. Here, microfluidic digital quantitative PCR (dqPCR) was developed to simultaneously quantify miRNA and protein targets in a multiplexed assay using a single detection chemistry. This streamlined analysis was achieved by integrating base-stacking PCR and immuno-PCR in a microfluidic array platform. Analyses of let-7a (miRNA) and IL-6 (protein) were first optimized separately to identify thermocycling and capture conditions amenable to both biomolecules. Singleplex dqPCR studies exhibited the expected digital signals and quantification cycles for both analytes over a range of concentrations. Multiplexed analyses were then conducted to quantify both let-7a and IL-6 with high sensitivity (LODs ∼ 3 fM) over a broad dynamic range (5-5000 fM) using only standard PCR reagents. This multiplexed dqPCR was then translated to the analysis of HEK293 cell lysate, where endogenous let-7a and IL-6 were measured simultaneously without sample purification or pretreatment. Collectively, these studies demonstrate that the integration of BS-PCR and immuno-PCR achieves a sensitive and streamlined approach for multiplexed analyses of miRNAs and proteins, which will enable researchers to gain better insights into disease pathogenesis in future applications.

Ultrasensitive reporter DNA sensors built on nucleic acid amplification techniques: Application in the detection of trace amount of protein

The detection of protein is of great significance for the study of biological physiological function, early diagnosis of diseases and drug research. However, the sensitivity of traditional protein detection methods for detecting trace amount of proteins was relatively low. By integrating sensitive nucleic acid amplification techniques (NAAT) with protein detection methods, the detection limit of protein detection methods can be substantially improved. The DNA that can specifically bind to protein targets and convert protein signals into DNA signals is collectively referred to reporter DNA. Various NAATs have been used to establish NAAT-based reporter DNA sensors. And according to whether enzymes are involved in the amplification process, the NAAT-based reporter DNA sensors can be divided into two types: enzyme-assisted NAAT-based reporter DNA sensors and enzyme-free NAAT-based reporter DNA sensors. In this review, we will introduce the principles and applications of two types of NAAT-based reporter DNA sensors for detecting protein targets. Finally, the main challenges and application prospects of NAAT-based reporter DNA sensors are discussed.

Combining hybrid nanoflowers with hybridization chain reaction for highly sensitive detection of SARS-CoV-2 nucleocapsid protein

BACKGROUND

COVID-19 (coronavirus disease 2019) pandemic has had enormous social and economic impacts so far. The nucleocapsid protein (N protein) is highly conserved and is a key antigenic marker for the diagnosis of early SARS-CoV-2 infection.

RESULTS

In this study, the N protein was first captured by an aptamer (Aptamer 58) coupled to magnetic beads (MBs), which in turn were bound to another DNA sequence containing the aptamer (Aptamer 48-Initiator). After adding 5'-biotinylated hairpin DNA Amplifier 1 and Amplifier 2 with cohesive ends for complementary hybridization, the Initiator in the Aptamer 48-Initiator began to trigger the hybridization chain reaction (HCR), generating multiple biotin-labeled DNA concatamers. When incubated with synthetic streptavidin-invertase-Ca3(PO4)2 hybrid nanoflower (SICa), DNA concatamers could specifically bind to SICa through biotin-streptavidin interaction with high affinity. After adding sucrose, invertase in SICa hydrolyzed sucrose to glucose, whose concentration could be directly read with a portable glucometer, and its concentration was positively correlated with the amount of captured N protein. The method is highly sensitive with a detection limit as low as 1 pg/mL.

SIGNIFICANCE

We believe this study provided a practical solution for the early detection of SARS-CoV-2 infection, and offered a new method for detecting other viruses through different target proteins.

The rate-limiting procedure of 3D DNA walkers and their applications in tandem technology

DNA walkers, artificial dynamic DNA nanomachines, can mimic actin to move rapidly along a predefined nucleic acid track. They can generally be classified as one- (1D), two- (2D), and three-dimensional (3D) DNA walkers. In particular, 3D DNA walkers demonstrate amazing sustainable walking ability, strong enrichment ability, and fantastic signal amplification ability. In light of these, 3D DNA walkers have been widely used in fields such as biosensors, bioanalysis and cell imaging. Most notably, the strong compatibility of 3D DNA walkers allows their integration with a range of amplification strategies, effectively enhancing signal transduction and amplifying biosensor sensing signals. Herein, we first systematically expound the walking principle of the 3D walkers in this review. Then, by presenting representative examples, the research direction of 3D walkers in recent years is discussed. Furthermore, we also categorize and evaluate diverse tandem signal amplification strategies in 3D walkers. Finally, the challenges and development trends of 3D DNA walkers in the emerging field of analysis are carefully discussed. It is believed that this work can provide new ideas for researchers to quickly understand 3D DNA walkers and their applications in diverse biosensors.

A triple-cycle amplification biosensor for colorimetric detection of mutant PIK3CAE545K based on cascade-driven DNA walker and branched hybridization strand reaction

Circulating tumor DNA (ctDNA) is an ideal candidate for liquid biopsy biomarkers. Therefore, detecting a low abundance of ctDNA is essential for early cancer diagnosis. Here, we developed a novel triple circulation amplification system integrating entropy and enzyme cascade-driven three-dimensional (3D) DNA walker and branched hybridization strand reaction (B-HCR) for ultrasensitive detection of breast cancer-related ctDNA. In this study, the 3D DNA walker was constructed by inner track probes (NH) and complex S on a microsphere. Once the DNA walker was triggered by the target, the strand replacement reaction ran first and kept circulating to rapidly displace the DNA walker containing 8-17 DNAzyme. Secondly, the DNA walker could repeatedly cleave NH autonomously along the inner track, generating numerous initiators, and then promoting B-HCR to activate the third cycle. Subsequently, the split G-rich fragments were brought in close to form the G-quadruplex/hemin DNAzyme by adding hemin, with the addition of H₂O₂ and ABTS, the target could be observed. Benefiting from triplex cycles, the PIK3CA^E545K mutation detection possesses a good linear range from 1-10³ fM, and the limit of detection was 0.65 fM. Due to the low cost and high sensitivity, the proposed strategy has great potential in early diagnosis of breast cancer.

Biosensors based on functional nucleic acids and isothermal amplification techniques

In the past few years, with the in-depth research of functional nucleic acids and isothermal amplification techniques, their applications in the field of biosensing have attracted great interest. Since functional nucleic acids have excellent flexibility and convenience in their structural design, they have significant advantages as recognition elements in biosensing. At the same time, isothermal amplification techniques have higher amplification efficiency, so the combination of functional nucleic acids and isothermal amplification techniques can greatly promote the widespread application of biosensors. For the purpose of further improving the performance of biosensors, this review introduces several widely used functional nucleic acids and isothermal amplification techniques, as well as their classification, basic principles, application characteristics, and summarizes their important applications in the field of biosensing. We hope to provide some references for the design and construction of new tactics to enhance the detection sensitivity and detection range of biosensing.