Search Results (145)

G-quadruplex (G4) DNA structures have recently emerged as promising chiral scaffolds for enantioselective catalysis. This study investigates how thymidine loop modifications influence the catalytic performance of the telomeric G4 sequence HT21 in the asymmetric sulfoxidation of thioanisole. To this end, several singly or doubly modified HT21 derivatives were synthesized by using β-L-2′-deoxythymidine, 5-hydroxymethyl-2′-deoxyuridine, and 5-bromo-2′-deoxyuridine instead of a T residue, or β-L-2′-deoxyadonesine instead of an A residue, in specific positions within the TTA loops. The catalytic activity of these analogues was evaluated in the Cu(II)-mediated oxidation of thioanisole using hydrogen peroxide as oxidant. All modified sequences maintained complete substrate conversion, but their enantioselectivities varied markedly. Whereas the highest enantiomeric excess (84% ee) had previously been achieved with the HT21 analogue bearing a β-L-2′-deoxyadenosine in the first loop, the thymidine-based modifications, either alone or in combination, resulted in lower ee values, suggesting that loop alterations critically affect the chiral microenvironment, not all loop positions are functionally equivalent, and single substitutions within the same loop can result in different enantioselectivities. These findings highlight new insights on how individual loop residues contribute to asymmetric induction and offer further details for tuning G4-based catalytic scaffolds. Full article

Split G-quadruplex DNAzymes offer unique opportunities for building gated biosensors with a wide range of applications. Splitting G4 DNAzymes involves separating guanine tracts in the G-quadruplex DNA sequence into two non-functional sequences that reconstitute into a functional G-quadruplex with peroxidase activity upon hybridisation of the aptamer probe region within the split system with the target molecule. Several studies have demonstrated the reassembly of split G4 DNAzymes and their applications in the detection of various analytes. This approach offers unique opportunities for modular biosensor construction, target-dependent activation, lack of requirement for labelling, amplification-free high sensitivity, and specificity over traditional G4 sensing. In this review, we explore the strategies of splitting G-quadruplex and their applications in biomedical diagnosis, environmental sensing, food safety monitoring, cell detection, and the integration of the technology with nanomaterials for enhanced stability and sensitivity. We considered the classical intermolecular split strategies that utilise binary probes and intramolecular split systems, which integrate the spacer DNA that allow for single probes as the model G4 sequence. Finally, we explore the current challenges required to develop split G-quadruplex DNAzymes into tools for routine practical applications. Full article

Background/Objectives: GATA-binding protein 3 (GATA-3) is a crucial transcription factor that drives type 2 immune responses, and it is actively involved in allergic conditions such as asthma, allergic rhinitis (AR), and atopic dermatitis (AD). However, the molecular mechanisms GATA-3 uses to modulate immune responses and its potential therapeutic targeting are not fully understood. This systematic review aimed to summarize studies on the role of GATA-3 in immune responses, particularly in allergic diseases, and evaluate GATA-3’s potential as a therapeutic target. Methods: We searched PubMed, Scopus, Web of Science, Cochrane, and Science Direct for studies published before April 2025. Articles were sifted through using predefined criteria, and risk of bias was measured with RoB 2 for clinical trials and SYRCLE for animal models and in vitro studies; evidence was graded using the GRADE system. Results: Twenty-nine eligible studies reported that GATA-3 is a key regulator of Th2 and ILC2 differentiation, promoting the production of IL-4, IL-5, and IL-13. Animal models and in vitro studies demonstrated its role in exacerbating allergic inflammation and highlighted the promise of targeting strategies such as DNAzymes and nanocapsules. Clinical trials showed that targeting GATA-3, particularly with DNAzymes, can reduce allergic responses in asthma. Conclusions: GATA-3’s role in driving allergic inflammation through Th2 and ILC2 pathways suggests it as a promising therapeutic target. Understanding its broader regulatory mechanisms is imperative for designing effective GATA-3 targeting-based therapies. Full article

Obesity plays a crucial role in the progression of insulin resistance and type 2 diabetes which are related to inflammation and liver disease. GATA-3 is a transcription factor that is involved in adipogenesis and inflammation. Therefore, it could be a potential therapeutic target for obesity-associated metabolic disorders. This study aimed to examine the effects of GATA-3 suppression on body weight, fat depot redistribution, liver histopathology, and inflammatory markers in transgenic db/db obese mice. Male db/db mice received subcutaneous injections of GATA-3-specific DNAzyme (hgd40; 10 or 100 µg/mL), pioglitazone (as a positive control), or vehicle only (as a negative control), twice weekly for two weeks. Body weight, organ weights, liver histopathology, mRNA expression of selected genes and serum cytokine levels were assessed. GATA-3 expression was not region specific, and its suppression did not significantly affect fat depot distribution or organ weights. However, the low dose of hgd40 accelerated body weight gain transiently. It also increased Il10 mRNA expression in the liver and significantly increased IL-10 protein concentration in the serum. In addition, a high dose of hgd40 resulted in a marked decrease in hepatocyte ballooning degeneration. These findings suggest that GATA-3 suppression may modulate inflammation and liver injury in obesity, warranting further investigation into its therapeutic potential for obesity-related metabolic disorders. Full article

G-quadruplex (G4) DNAzymes, guanine-rich sequences that fold into four-stranded structures and bind hemin to mimic peroxidase activity, are widely used in biosensing. Split G4 DNAzymes offer conditional activation upon target recognition, enabling high specificity and modularity. However, achieving low OFF-state leakage remains a major challenge. Here, we systematically characterized four representative G4 scaffolds, C-myc, Bcl2, PS5.M, and C-kit, under standardized ABTS/H₂O₂ conditions to assess their kinetic properties and suitability for split designs. C-myc exhibited the highest sustained activity and near-linear concentration dependence, making it ideal for quantitative sensing, while Bcl2 showed durable catalysis suited for extended read windows. C-kit produced rapid bursts with early plateaus, favoring binary outputs, and PS5.M initiated quickly but inactivated rapidly, suggesting potential application of systems requiring fast response. Split-mode analysis revealed that symmetric 2:2 partitions often retained significant activity, whereas asymmetric 3:1 splits reduced but did not eliminate leakage. Among the four G4 DNAzymes, PS5.M demonstrated the most promising OFF-state suppression. Design strategies to minimize leakage including non-classical splits, loop/flank edits, and template-assisted assembly could be used to optimize biosensor functionalities. These findings identify essential factors critical for designing robust split DNAzyme biosensors, advancing applications in diagnostics and molecular logic gates. Full article

Smart nucleic acid hydrogels (SNAHs), endowed with stimulus responsiveness, function as programmable molecular switches that can perceive diverse external stimuli and undergo rapid, reversible, and highly specific conformational or performance changes. These dynamic properties have enabled the rational design of biosensors with bionic behaviors, facilitating cascaded “recognition–decision–execution” processes that support advanced biological analysis. Consequently, SNAHs are recognized as a core breakthrough for the next generation of intelligent biosensing units. However, a systematic mapping between SNAH design strategies, specific stimuli, and application fields remains lacking. This review mainly analyzes advances in SNAH-based biosensors over the past five years, proposing flexible and feasible design strategies and key trends in customization. Firstly, we systematically summarize molecular recognition modules involved in the construction of SNAHs, including aptamers, DNAzymes, antibodies, and specific binding peptides. Subsequently, we elaborate on the responses of these modules to external stimuli, so as to further facilitate the signal transduction of signals derived from physical, chemical, and biological sources involving temperature, light, magnetic fields, pH, nucleic acids, proteins, other biomolecules, and pathogens. Additionally, the review outlines the research progress of SNAHs in environmental monitoring, food safety, and medical diagnostics. Finally, we provide an integrated perspective on future opportunities and challenges, highlighting the innovative framework for designing SNAH-based biosensors and offering a practical roadmap for next-generation intelligent sensing applications. Full article

In this study, a sliding microfluidic biosensor integrating RPA-SDA cascaded amplification was developed for the rapid, visual detection of Shigella. A novel RPA primer targeting the specific ipaH gene was designed to include a 5′-end G-quadruplex (G4) sequence and the complementary sequence of an Nt.BstNBI endonuclease recognition site. The RPA product templates a subsequent SDA reaction, generating abundant G4 structures that form peroxidase-mimicking DNAzymes with hemin, catalyzing a TMB reaction that produces a distinct blue color for visual readout (on-chip detection at OD₃₇₀, distinct from conventional tube assays at OD₄₅₀). The core on-chip detection process was completed within 13 min (10 min for SDA and 3 min for color development), achieving a limit of detection of 3.5 × 10⁻⁴ ng/μL for Shigella genomic DNA. This timing explicitly excludes the preceding, off-chip steps of nucleic acid extraction and RPA amplification. Validation using spiked lettuce samples confirmed the platform’s high specificity and sensitivity. This work establishes a proof-of-concept for a portable screening tool, highlighting its potential for on-site food safety applications. However, further validation in diverse food matrices and under real-world field conditions is required to fully establish its practical utility. Full article

Interest in non-canonical DNA structures continues to grow, in part fueled by the recent discovery of a new structure, G-triplex DNA. Originally proposed as folding intermediates for G-quadruplex DNA, G-triplex DNA has more recently been shown to form from truncated G-quadruplex sequence oligonucleotides and other, specifically designed sequences. In this review, we provide the first, comprehensive survey of G-triplex DNA and RNA, covering the literature up to 2024. We include reports of G-triplex DNA from bulk solution and single-molecule approaches, the structural characterization of G-triplex DNA, and the breadth of oligonucleotide sequences that have been reported to form these structures. The formation of G-triplex RNA structures is also reviewed. The evolving understanding of sequence and environmental effects on G-triplex formation are presented together with challenges due to structural polymorphism and competing formation of multimeric G-quadruplex structures. Hints of the biological relevance of G-triplexes are provided by reports of protein recognition of these structures and their effects on DNA replication in vitro. Interaction of G-triplex DNA with a variety of ligands has been reported, although the search for selective ligands that can distinguish G-triplex from G-quadruplex is on-going. The vast majority of publications in the area have focused on the utilization of G-triplex in biosensing applications, which has shown some advantages compared to G-quadruplex-based systems. These results highlight the potential utility of G-triplex structures in a variety of domains and show its promise in applications in biotechnology, medicine, and research. Full article

The sensitive and efficient detection of ochratoxin A (OTA) is critical for protecting agricultural ecosystems and public health. A dual-mode plasmonic colorimetric/photothermal aptasensor, based on a Mn²⁺-powered DNA walker for mediating gold nanobipyramid (AuNB) growth, is proposed for OTA detection in this study. In sensing the target OTA, the walking DNA (W-DNA) on the magnetic walker probe was independent and then the environment-friendly Mn²⁺ powered the generation of DNAzyme, where abundant thiol-modified DNA (DNA-SH) was produced by autonomous walking. The positively related DNA-SH level could mediate AuNB growth and reflect dual-mode plasmonic signals. Ultrasensitivity is demonstrated with a limit of detection (LOD) value of 48.6 pg mL⁻¹ for colorimetric mode and 37.6 pg mL⁻¹ for photothermal mode. The aptasensor exhibited high specificity (with cross-reactivity values below 6.2% for other analytes) and high reliability for OTA detection. The requisite practicability and accessibility are verified via its application in agricultural byproduct samples. The findings of this study offer an alternative and efficient biosensing pathway for improving detection performance, enabling green, enzyme-free, homogeneous, and dual-mode strategies for monitoring other pollutants. Full article

With nuclear power playing an increasing role in efforts to reduce carbon emissions, the development of effective and sensitive monitoring tools for (radio)toxic elements in the environment has become essential. This review highlights recent advances in fluorescent probes developed for the detection of key elements associated with the nuclear industry, including uranium, cesium, strontium, technetium, zirconium, and beryllium. Various sensor platforms, ranging from organic ligands and DNAzymes to metal–organic frameworks and quantum dots, offer promising features, such as high sensitivity, selectivity, and suitability for environmental matrices. Several recent designs now achieve detection limits in the nanomolar to picomolar range, revealing new perspectives for environmental and biological applications. Full article

Enteric viruses are a major cause of waterborne infections due to their high environmental stability and extremely low infectious dose. Current molecular diagnostic methods, while accurate, often depend on thermal cycling and centralized laboratory facilities, limiting their applicability in decentralized or resource-limited settings. In this study, we developed an isothermal biosensor based on a split deoxyribozyme that reconstitutes its catalytic core upon hybridization with a conserved sequence of enteroviral RNA. This activation leads to site-specific cleavage of a fluorogenic substrate, producing a quantifiable fluorescent signal. The system was experimentally validated using both synthetic enteroviral RNA and RNA extracted from environmental water samples. To enhance detection sensitivity, the DNAzyme-based assay was coupled with isothermal RNA amplification. The results demonstrate high selectivity and compatibility with real-world samples, supporting the sensor’s utility for field-deployable viral RNA detection. Overall, this study highlights the potential of the DNAzyme-based platform as a portable, sequence-specific, and amplification-assisted diagnostic tool for environmental surveillance of enteric viruses. Full article

Staphylococcus aureus is the primary pathogen responsible for mastitis in dairy cows and foodborne illnesses, posing a significant threat to public health and food safety. Here, we developed an enhanced sensor based on solid-phase separation using gold-magnetic nanoparticles (Au@Fe₃O₄) and signal amplification via dendritic DNA nanostructures. The substrate chain was specifically immobilized using thiol–gold coordination, and a three-dimensional dendritic structure was constructed through sequential hybridization of DNAzymes, L chains, and Y chains, resulting in a 2.8-fold increase in initial fluorescence intensity. Upon specific cleavage of the substrate chain at the rA site by S. aureus DNA, the complex dissociates, resulting in fluorescence intensity decay. The fluorescence intensity is negatively correlated with the concentration of Staphylococcus aureus. After optimization, the biosensor maintains a detection limit of 1 CFU/mL within 3 min, with a linear range extended to 1–10⁷ CFU/mL (R² = 0.998) and recovery rates of 85.6–102.1%, significantly enhancing resistance to matrix interference. This provides an innovative solution for rapid on-site detection of foodborne pathogens. Full article

Magnesium ions (Mg²⁺) play an important role in animal health, with their concentration in the bloodstream serving as a key indicator for hypomagnesemia diagnosis. In this study, a flexible hydrophobic paper-based microfluidic field-effect biosensor was developed for point-of-care Mg²⁺ detection, which integrated flexible hydrophobic paper, semiconducting single-walled carbon nanotubes (SWNTs) and a Mg²⁺-specific RNA-cleaving DNAzyme(RCD)-based DNA nanostructure. Flexible hydrophobic paper was synthesized by using cellulose paper and octadecyltrichlorosilane, improving mechanical strength and decreasing biological interference. To achieve high sensitivity, the Mg²⁺-specific RCD was functionalized with SWNTs, and then repeatedly self-assembled two different Y-shaped DNAs to construct a DNA nanostructure based on a similar DNA origami technique. This proposed biosensor exhibited a linear detection range from 1 μM to 1000 μM, with a detection limit of 0.57 μM, demonstrating its great stability, selectivity, and anti-interference performance. This innovative design offers promising potential for Mg²⁺ monitoring in real applications. Full article

The B Cell Lymphoma-2 (BCL-2) family proteins are central regulators of apoptosis, and their dysregulation is frequently associated with cancer progression and resistance to therapy. While small molecules like venetoclax have shown promise, nucleic acid-based therapeutics targeting BCL-2 remain underexplored. Here, we report a novel in vitro evolution strategy to generate trans-acting RNA-cleaving DNAzymes targeting natural BCL-2 mRNA without requiring covalent substrate-linking. Using a 50-base region of BCL-2 mRNA as a selection target, we evolved several DNAzymes that demonstrate significant RNA cleavage activity. These DNAzymes downregulated BCL-2 expression, induced apoptosis, and reduced cell viability in HepG2 and MCF-7 cancer cells. In vivo, our novel DNAzymes significantly suppressed tumor growth in a syngeneic mouse breast cancer model, with efficacy comparable to 5-Fluorouracil. This study presents a proof of concept for a novel strategy to evolve functional DNAzymes against native mRNA sequences and highlights their potential as gene-silencing tools in cancer therapy. Future studies will explore the therapeutic potential of these findings in cancer patients. Additionally, investigating the underlying molecular mechanisms in more complex cancer models will further validate the observed effects. Full article

The rapid and ultrasensitive detection of Salmonella holds strategic significance for food safety surveillance and public health protection systems. This study innovatively developed a label-free biosensing platform based on the synergistic integration of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas12a and the fluorescent deoxyribozyme Aurora for the efficient detection of foodborne Salmonella. The detection mechanism operates through a molecular cascade reaction: target-activated Cas12a protein specifically degrades Aurora deoxyribozyme via its trans-cleavage activity, thereby abolishing the enzyme’s catalytic capability to convert 4-methylumbelliferyl phosphate (4-MUP) into the highly fluorescent product 4-methylumbelliferone (4-MU). This cascade ultimately enables quantitative target analysis through fluorescence signal attenuation. Following systematic optimization of critical reaction parameters, the biosensing system demonstrated exceptional analytical performance: a detection limit of 1.29 CFU/mL with excellent linearity (R² = 0.992) spanning six orders of magnitude (1.65 × 10¹–10⁶ CFU/mL), along with high specificity against multiple interfering bacterial strains. Spike-and-recovery tests in complex food matrices (milk, chicken, and lettuce) yielded recoveries of 90.91–99.40% (RSD = 3.55–4.72%), confirming robust practical applicability. Notably, the platform design allows flexible detection of other pathogens through simple replacement of CRISPR guide sequences. Full article