Combined cryoablation and PD-1 inhibitor synergistically enhance antitumor immune responses in Lewis lung adenocarcinoma mice via the PI3K/AKT/mTOR pathway.

Cryoablation is a therapeutic modality for lung adenocarcinoma that destroys target tumors using lethal levels of cold, resulting in the release of large amounts of specific antigens that activate immune responses. However, tumor immune checkpoint escape mechanisms prevent these released self-antigens from inducing effective anti-tumor immune responses. To overcome this challenge, we propose the use of immune checkpoint inhibitors to relieve T cell inhibition by immune checkpoints and enhance the anti-tumor immune response mediated by cryoablation. We used bilateral tumor-bearing mouse models and a specific cryoablation instrument to study the efficacy of cryoablation combined with PD-1 inhibitors in Lewis lung adenocarcinoma model mice. We found that cryoablation combined with PD-1 inhibitors significantly inhibited the growth of mouse lung adenocarcinoma, prolonged mouse survival, and enhanced the anti-tumor immune response. Moreover, this combined regimen could synergistically promote the activation and proliferation of T cells via the PI3K/AKT/mTOR pathway. The present study provides a strong theoretical basis for the clinical combination of cryoablation and PD-1 inhibitors.

MALAT1 and NEAT1 Are Neuroprotective During Hypoxic Preconditioning in the Mouse Hippocampus Possibly by Regulation of NR2B.

Wang L, Fu G, Han R, Fan P, Yang J, Gong K, Zhao Z, Zhang C, Sun K, Shao GMALAT1 and NEAT1 Are Neuroprotective during Hypoxic Preconditioning in the Mouse Hippocampus Possibly by Regulation of NR2B High Alt Med Biol. 00:000-000, 2024. Background: The regulation of noncoding ribonucleic acid (ncRNA) has been shown to be involved in cellular and molecular responses to hypoxic preconditioning (HPC), a situation created by the induction of sublethal hypoxia in the brain. The ncRNAs metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and nuclear paraspeckle assembly transcript 1 (NEAT1) are abundantly expressed in the brain, where they regulate the expression of various genes in nerve cells. However, the exact roles of MALAT1 and NEAT1 in HPC are not fully understood. Methods: A mouse model of acute repeated hypoxia was used as a model of HPC, and MALAT1 and NEAT1 levels in the hippocampus were measured using real-time polymerase chain reaction (PCR). The mRNA and protein levels of N-methyl-d-aspartate receptor subunit 2 B (NR2B) in the mouse hippocampus were measured using real-time PCR and western blotting, respectively. HT22 cells knocked-down for MALAT1 and NEAT1 were used for in vitro testing. Expression of NR2B, which is involved in nerve cell injury under ischemic and hypoxic conditions, was also evaluated. The levels of spectrin and cleaved caspase-3 in MALAT1 and NEAT1 knockdown HT22 cells under oxygen glucose deprivation/reperfusion (OGD/R) were determined by western blotting. Results: HPC increased the expression of MALAT1 and NEAT1 and decreased the expression of NR2B mRNA in the mouse hippocampus (p < 0.05). Knockdown of MALAT1 and NEAT1 increased both NR2B mRNA and protein levels nearly twofold and caused damage under OGD/R conditions in HT22 cells (p < 0.05). Conclusion: MALAT1 and NEAT1 exert neuroprotective effects by influencing the expression of NR2B.

Construction of a 3D Quantum Dot Nanoassembly with Two-Step FRET for One-Step Sensing of Human Telomerase RNA in Breast Cancer Cells and Tissues.

Telomerase is an important biomarker for early diagnosis of cancers, but current telomerase assays usually rely on measuring the extension products of telomerase substrates, which increases the assay complexity. More evidence indicates that human telomerase RNA (hTR), as a core component of telomerase, is positively correlated with the telomerase activity. Herein, we demonstrate the development of a duplex-specific nuclease (DSN)-propelled 3D quantum dot (QD) nanoassembly with two-step Föster resonance energy transfer (FRET) for the one-step sensing of hTR in breast cancer cells and tissues. This assay involves only one hairpin probe modified with a Cy5 at the sixth base from the 5'-biotin end and a BHQ2 at the 3'-terminus, which integrates three functions of target recognition, target recycling amplification, and signal readout. The anchoring of the hairpin probe on the 605QD surface results in the formation of a 3D 605QD-Cy5-probe-BHQ2 nanoassembly in which two-step FRET occurs among the 605QD, Cy5, and BHQ2 quencher. Notably, the formation of 605QD-Cy5-probe-BHQ2 nanoassembly facilitates the reduction of background signal and the increase of signal-to-background ratio due to its dense, highly oriented nucleic acid shell-induced steric hindrance effect. This assay can achieve one-step and rapid detection of hTR with a detection limit of 2.10 fM, which is the simplest and most rapid hTR assay reported so far. Moreover, this assay can efficiently distinguish single-base mismatched sequences, and it can discriminate the hTR level between breast cancer patients and healthy donors with a high accuracy of 100%, with great prospects for early diagnosis of cancers.

One-Dimensional Covalent Organic Framework with Improved Charge Transfer for Enhanced Electrochemiluminescence.

We present a dimensional regulating charge transfer strategy to achieve an enhanced electrochemiluminescence (ECL) by constructing a one-dimensional pyrene-based covalent organic framework (1D-COF). The dual-chain-like edge architecture in 1D-COF facilitates the stabilization of aromatic backbones, the enhancement of electronic conjugations, and the decrease of energy loss. The 1D-COF generates enhanced anodic (92.5-fold) and cathodic (3.2-fold) signals with tripropylamine (TPrA) and K2S2O8 as the anodic and cathodic coreactants, respectively, compared with 2D-COF. The anodic and cathodic ECL efficiencies of 1D-COF are 2.08- and 3.08-fold higher than those of 2D-COF, respectively. According to density functional theory (DFT), the rotational barrier energy (ΔE) of 1D-COF enhances sharply with the increase of dihedral angle, suggesting that the architecture in 1D-COF restrains the intramolecular spin of aromatic chains, which facilitates the decrease of nonradiative transitions and the enhancement of ECL. Furthermore, 1D-COF can be used to construct an ECL biosensor for sensitive detection of dopamine.

Calcipotriol Nanosuspension-Loaded Trilayer Dissolving Microneedle Patches for the Treatment of Psoriasis: In Vitro Delivery and In Vivo Antipsoriatic Activity Studies.

Psoriasis, affecting 2-3% of the global population, is a chronic inflammatory skin condition without a definitive cure. Current treatments focus on managing symptoms. Recognizing the need for innovative drug delivery methods to enhance patient adherence, this study explores a new approach using calcipotriol monohydrate (CPM), a primary topical treatment for psoriasis. Despite its effectiveness, CPM's therapeutic potential is often limited by factors like the greasiness of topical applications, poor skin permeability, low skin retention, and lack of controlled delivery. To overcome these challenges, the study introduces CPM in the form of nanosuspensions (NSs), characterized by an average particle size of 211 ± 2 nm. These CPM NSs are then incorporated into a trilayer dissolving microneedle patch (MAP) made from poly(vinylpyrrolidone) and w poly(vinyl alcohol) as needle arrays and prefrom 3D printed polylactic acid backing layer. This MAP features rapidly dissolving tips and exhibits good mechanical properties and insertion capability with delivery efficiency compared to the conventional Daivonex ointment. The effectiveness of this novel MAP was tested on Sprague-Dawley rats with imiquimod-induced psoriasis, demonstrating efficacy comparable to the marketed ointment. This innovative trilayer dissolving MAP represents a promising new local delivery system for calcipotriol, potentially revolutionizing psoriasis treatment by enhancing drug delivery and patient compliance.

Defect Engineering Simultaneously Regulating Exciton Dissociation in Carbon Nitride and Local Electron Density in Pt Single Atoms Toward Highly Efficient Photocatalytic Hydrogen Production.

The high exciton binding energy (Eb) and sluggish surface reaction kinetics have severely limited the photocatalytic hydrogen production activity of carbon nitride (CN). Herein, a hybrid system consisting of nitrogen defects and Pt single atoms is constructed through a facile self-assembly and photodeposition strategy. Due to the acceleration of exciton dissociation and regulation of local electron density of Pt single atoms along with the introduction of nitrogen defects, the optimized Pt-MCT-3 exhibits a hydrogen production rate of 172.0 µmol h-1 (λ ≥ 420 nm), ≈41 times higher than pristine CN. The apparent quantum yield for the hydrogen production is determined to be 27.1% at 420 nm. The experimental characterizations and theoretical calculations demonstrate that the nitrogen defects act as the electron traps for the exciton dissociation, resulting in a decrease of Eb from 86.92 to 43.20 meV. Simultaneously, the stronger interaction between neighboring nitrogen defects and Pt single atoms directionally drives free electrons to aggregate around Pt single atoms, and tailors the d-band electrons of Pt, forming a moderate binding strength between Pt atoms and H* intermediates.

Hypoxia preconditioning increases Notch1 activity by regulating DNA methylation in vitro and in vivo.

BACKGROUND: Our previous research has demonstrated that hypoxic preconditioning (HPC) can improve spatial learning and memory abilities in adult mice. Adult hippocampal neurogenesis has been associated with learning and memory. The Neurogenic locus notch homolog protein (Notch) was involved in adult hippocampal neurogenesis, as well as in learning and memory. It is currently unclear whether the Notch pathway regulates hippocampal neuroregeneration by modifying the DNA methylation status of the Notch gene following HPC. METHOD: The HPC animal model and cell model were established through repeated hypoxia exposure using mice and the mouse hippocampal neuronal cell line HT22. Step-down test was conducted on HPC mice. Real-time PCR and Western blot analysis were used to assess the mRNA and protein expression levels of Notch1 and hairy and enhancer of split1 (HES1). The presence of BrdU-positive cells and Notch1 expression in the hippocampal dental gyrus (DG) were examined with confocal microscopy. The methylation status of the Notch1 was analyzed using methylation-specific PCR (MS-PCR). HT22 cells were employed to elucidate the impact of HPC on Notch1 in vitro. RESULTS: HPC significantly improved the step-down test performance of mice with elevated levels of mRNA and protein expression of Notch1 and HES1 (P < 0.05). The intensities of the Notch1 signal in the control group, the H group and the HPC group were 2.62 ± 0.57 × 107, 2.87 ± 0.84 × 107, and 3.32 ± 0.14 × 107, respectively, and the number of BrdU (+) cells in the hippocampal DG were 1.83 ± 0.54, 3.71 ± 0.64, and 7.29 ± 0.68 respectively. Compared with that in C and H group, the intensity of the Notch1 signal and the number of BrdU (+) cells increased significantly in HPC group (P < 0.05). The methylation levels of the Notch1 promoter 0.82 ± 0.03, 0.65 ± 0.03, and 0.60 ± 0.02 in the C, H, and HPC groups, respectively. The methylation levels of Notch1 decreased significantly (P < 0.05). The effect of HPC on HT22 cells exhibited similarities to that observed in the hippocampus. CONCLUSION: HPC may confer neuroprotection by activating the Notch1 signaling pathway and regulating its methylation level, resulting in the regeneration of hippocampal neurons.

Integrative Analyses of Bulk and Single-Cell RNA Seq Identified the Shared Genes in Acute Respiratory Distress Syndrome and Rheumatoid Arthritis.

Acute respiratory distress syndrome (ARDS), a progressive status of acute lung injury (ALI), is primarily caused by an immune-mediated inflammatory disorder, which can be an acute pulmonary complication of rheumatoid arthritis (RA). As a chronic inflammatory disease regulated by the immune system, RA is closely associated with the occurrence and progression of respiratory diseases. However, it remains elusive whether there are shared genes between the molecular mechanisms underlying RA and ARDS. The objective of this study is to identify potential shared genes for further clinical drug discovery through integrated analysis of bulk RNA sequencing datasets obtained from the Gene Expression Omnibus database, employing differentially expressed genes (DEGs) analysis and weighted gene co-expression network analysis (WGCNA). The hub genes were identified through the intersection of common DEGs and WGCNA-derived genes. The Random Forest (RF) and least absolute shrinkage and selection operator (LASSO) algorithms were subsequently employed to identify key shared target genes associated with two diseases. Additionally, RA immune infiltration analysis and COVID-19 single-cell transcriptome analysis revealed the correlation between these key genes and immune cells. A total of 59 shared genes were identified from the intersection of DEGs and gene clusters obtained through WGCNA, which analyzed the integrated gene matrix of ALI/ARDS and RA. The RF and LASSO algorithms were employed to screen for target genes specific to ALI/ARDS and RA, respectively. The final set of overlapping genes (FCMR, ADAM28, HK3, GRB10, UBE2J1, HPSE, DDX24, BATF, and CST7) all exhibited a strong predictive effect with an area under the curve (AUC) value greater than 0.8. Then, the immune infiltration analysis revealed a strong correlation between UBE2J1 and plasma cells in RA. Furthermore, scRNA-seq analysis demonstrated differential expression of these nine target genes primarily in T cells and NK cells, with CST7 showing a significant positive correlation specifically with NK cells. Beyond that, transcriptome sequencing was conducted on lung tissue collected from ALI mice, confirming the substantial differential expression of FCMR, HK3, UBE2J1, and BATF. This study provides unprecedented evidence linking the pathophysiological mechanisms of ALI/ARDS and RA to immune regulation, which offers novel understanding for future clinical treatment and experimental research.

Autonomous enzymatic synthesis of functional nucleic acids for sensitive measurement of long noncoding RNA in human lung tissues.

Aberrant long noncoding RNA (lncRNA) expression is linked to varied pathological processes and malignant tumors, and lncRNA can serve as potential disease biomarkers. Herein, we demonstrate the autonomous enzymatic synthesis of functional nucleic acids for sensitive measurement of lncRNA in human lung tissues on the basis of multiple primer generation-mediated rolling circle amplification (mPG-RCA). This assay involves two padlock probes that act as both a detection probe for recognizing target lncRNA and a domain for producing complementary DNAzyme. Two padlock probes can hybridize with target lncRNA at different sites, followed by ligation to form a circular template with the aid of RNA ligase. The circular template can initiate mPG-RCA to generate abundant Mg2+-dependent DNAzymes that can specifically cleave signal probes to induce the recovery of Cy3 fluorescence. The inherent characteristics of ligase-based ligation reaction and DNAzymes endow this assay with excellent specificity, and the introduction of multiple padlock probes endows this assay with high sensitivity. This strategy can rapidly and sensitively measure lncRNA with a wide linear range of 1 fM - 1 nM and a detection limit of 678 aM within 1.5 h, and it shows distinct advantages of simplicity and immobilization-free without the need of precise temperature control and tedious procedures of nanomaterial preparation. Moreover, it enables accurate measurement of lncRNA level in normal cells and malignant tumor cells as well as differentiation of lncRNA expressions in tissues of non-small cell lung cancer (NSCLC) patients and normal individuals, with promising applications in biomedical studies and disease diagnosis.

Recent advances in nucleic acid signal amplification-based aptasensors for sensing mycotoxins.

Mycotoxin contamination in food products may cause serious health hazards and economic losses. The effective control and accurate detection of mycotoxins have become a global concern. Even though a variety of methods have been developed for mycotoxin detection, most conventional methods suffer from complicated operation procedures, low sensitivity, high cost, and long assay time. Therefore, the development of simple and sensitive methods for mycotoxin assay is highly needed. The introduction of nucleic acid signal amplification technology (NASAT) into aptasensors significantly improves the sensitivity and facilitates the detection of mycotoxins. Herein, we give a comprehensive review of the recent advances in NASAT-based aptasensors for assaying mycotoxins and summarize the principles, features, and applications of NASAT-based aptasensors. Moreover, we highlight the challenges and prospects in the field, including the simultaneous detection of multiple mycotoxins and the development of portable devices for field detection.

Novel Pt(IV) complexes containing salvigenin ligand reverse cisplatin-induced resistance by inhibiting Rap1b-mediated cancer cell stemness in esophageal squamous cell carcinoma treatments.

Esophageal squamous cell carcinoma (ESCC) is a malignant tumor that is highly susceptible to metastasis, recurrence and resistance, and few therapeutic targets have been identified and proven effective. Herein, we demonstrated for the first time that Rap1b can positively regulate ESCC cell stemness, as well as designed and synthesized a novel class of Pt(IV) complexes that can effectively inhibit Raplb. In vitro biological studies showed that complex-1 exhibited stronger cytotoxicity than cisplatin and oxaliplatin against a variety of ESCC cells, and effectively reversed cisplatin-induced resistance of TE6 cells by increasing cellular accumulation of platinum and inhibiting cancer cell stemness. Significantly, complex-1 also exhibited strong ability to reversal cisplatin-induced cancer cell resistance and inhibit tumor growth in TE6/cDDP xenograft mice models, with a tumor growth inhibition rate of 73.3 % at 13 mg/kg and did not show significant systemic toxicity. Overall, Rap1b is a promising target to be developed as an effective treatment for ESCC. Complex-1, as the first Pt(IV) complex that can strongly inhibit Rap1b, is also worthy of further in-depth study.

RUNX1-BMP2 promotes vasculogenic mimicry in laryngeal squamous cell carcinoma via activation of the PI3K-AKT signaling pathway.

BACKGROUND: Laryngeal squamous cell carcinoma (LSCC) is one of the most common malignant tumors of the head and neck. Vasculogenic mimicry (VM) is crucial for tumor growth and metastasis and refers to the formation of fluid channels by invasive tumor cells rather than endothelial cells. However, the regulatory mechanisms underlying VM during the malignant progression of LSCC remain largely unknown. METHODS: Gene expression and clinical data for LSCC were obtained from the TCGA and Gene GEO (GSE27020) databases. A risk prediction model associated with VM was established using LASSO and Cox regression analyses. Based on their risk scores, patients with LSCC were categorized into high- and low-risk groups. The disparities in immune infiltration, tumor mutational burden (TMB), and functional enrichment between these two groups were examined. The core genes in LSCC were identified using the machine learning (SVM-RFE) and WGCNA algorithms. Subsequently, the involvement of bone morphogenetic protein 2 (BMP2) in VM and metastasis was investigated both in vitro and in vivo. To elucidate the downstream signaling pathways regulated by BMP2, western blotting was performed. Additionally, ChIP experiments were employed to identify the key transcription factors responsible for modulating the expression of BMP2. RESULTS: We established a new precise prognostic model for LSCC related to VM based on three genes: BMP2, EPO, and AGPS. The ROC curves from both TCGA and GSE27020 validation cohorts demonstrated precision survival prediction capabilities, with the nomogram showing some net clinical benefit. Multiple algorithm analyses indicated BMP2 as a potential core gene. Further experiments suggested that BMP2 promotes VM and metastasis in LSCC. The malignant progression of LSCC is promoted by BMP2 via the activation of the PI3K-AKT signaling pathway, with the high expression of BMP2 in LSCC resulting from its transcriptional activation by runt-related transcription factor 1 (RUNX1). CONCLUSION: BMP2 predicts poor prognosis in LSCC, promotes LSCC VM and metastasis through the PI3K-AKT signaling pathway, and is transcriptionally regulated by RUNX1. BMP2 may be a novel, precise, diagnostic, and therapeutic biomarker of LSCC.

Construction of a glycosylation-mediated fluorescent biosensor for label-free measurement of site-specific 5-hydroxymethylcytosine in cancer cells with zero background signal.

BACKGROUND: 5-hydroxymethylcytosine (5hmC) as an epigenetic modification can regulate gene expression, and its abnormal level is related with various tumor invasiveness and poor prognosis. Nevertheless, the current methods for 5hmC assay usually involve expensive instruments/antibodies, radioactive risk, high background, laborious bisulfite treatment procedures, and non-specific/long amplification time. RESULTS: We develop a glycosylation-mediated fluorescent biosensor based on helicase-dependent amplification (HDA) for label-free detection of site-specific 5hmC in cancer cells with zero background signal. The glycosylated 5hmC-DNA (5ghmC) catalyzed by ß-glucosyltransferase (ß-GT) can be cleaved by AbaSI restriction endonuclease to generate two dsDNA fragments with sticky ends. The resultant dsDNA fragments are complementary to the biotinylated probes and ligated by DNA ligases, followed by being captured by magnetic beads. After magnetic separation, the eluted ligation products act as the templates to initiate HDA reaction, generating abundant double-stranded DNA (dsDNA) products within 20 min. The dsDNA products are measured in a label-free manner with SYBR Green I as an indicator. This biosensor can measure 5hmC with a detection limit of 2.75 fM and a wide linear range from 1 × 10-14 to 1 × 10-8 M, and it can discriminate as low as 0.001% 5hmC level in complex mixture. Moreover, this biosensor can measure site-specific 5hmC in cancer cells, and distinguish tumor cells from normal cells. SIGNIFICANCE: This biosensor can achieve a zero-background signal without the need of either 5hmC specific antibody or bisulfite treatment, and it holds potential applications in biological research and disease diagnosis.

Construction of an Enzymatically Controlled DNA Nanomachine for One-Step Imaging of Telomerase in Living Cells.

Telomerase is a basic reverse transcriptase that maintains the telomere length in cells, and accurate and specific sensing of telomerase in living cells is critical for medical diagnostics and disease therapeutics. Herein, we demonstrate for the first time the construction of an enzymatically controlled DNA nanomachine with endogenous apurinic/apyrimidinic endonuclease 1 (APE1) as a driving force for one-step imaging of telomerase in living cells. The DNA nanomachine is designed by rational engineering of substrate probes and reporter probes embedded with an enzyme-activatable site (i.e., AP site) and their subsequent assembly on a gold nanoparticle (AuNP). Upon recognition and cleavage of the AP site in the substrate probe by APE1, the loop of the substrate probe unfolds, exposing telomeric primer (TP) with the 3'-OH end. Subsequently, the TP is elongated by telomerase at the 3'-OH end to generate a long telomeric product. The resultant telomeric product acts as a swing arm that can hybridize with a reporter probe to initiate the APE1-powered walking reaction, ultimately generating a significantly enhanced fluorescence signal. Notably, endogenous APE1 is used as the driving force of the DNA nanomachine, avoiding the introduction of exogenous auxiliary cofactors into the cellular microenvironment. Owing to the high kinetics and high amplification efficiency of the APE1-powered DNA nanomachine, this strategy enables one-step sensitive sensing of telomerase in vitro and in vivo. It can successfully discriminate telomerase activity between cancer cells and normal cells, screen telomerase inhibitors, and monitor the variations of telomerase activity in living cells, offering a prospective platform for molecular diagnostics and drug discovery.

Construction of Gold/Rhodium Freestanding Superstructures as Antenna-Reactor Photocatalysts for Plasmon-Driven Nitrogen Fixation.

Precisely controlling the architecture and spatial arrangement of plasmonic heterostructures offers unique opportunities to tailor the catalytic property, whereas the lack of a wet-chemistry synthetic approach to fabricating nanostructures with high-index facets limits their practical applications. Herein, we describe a universal synthetic strategy to construct Au/Rh freestanding superstructures (SSs) through the selective growth of ordered Rh nanoarrays on high-index-faceted Au nanobipyramids (NBPs). This synthetic strategy works on various metal nanocrystal substrates and can yield diverse Au/Rh and Pd/Rh SSs. Especially, the obtained Au NBP/Rh SSs exhibit high photocatalytic activity toward N2 fixation as a result of the spatially separated architecture, local electric field enhancement, and the antenna-reactor mechanism. Both theoretical and experimental results reveal that the Au NBPs can function as nanoantennas for light-harvesting to generate hot charge carriers for driving N2 fixation, while the Rh nanoarrays can serve as the active sites for N2 adsorption and activation to synergistically promote the overall catalytic activity in the Au NBP/Rh SSs. This work offers new avenues to rationally designing and constructing spatially separated plasmonic photocatalysts for high-efficiency catalytic applications.

Integration of Demethylation-Activated DNAzyme with a Single Quantum Dot Nanosensor for Sensitive Detection of O6-Methylguanine DNA Methyltransferase in Breast Tissues.

O6-Methylguanine-DNA-methyltransferase (MGMT) is a demethylation protein that dynamically regulates the O6-methylguanine modification (O6 MeG), and dysregulated MGMT is implicated in various malignant tumors. Herein, we integrate demethylation-activated DNAzyme with a single quantum dot nanosensor to sensitively detect MGMT in breast tissues. The presence of MGMT induces the demethylation of the O6 MeG-caged DNAzyme and the restoration of catalytic activity. The activated DNAzyme then specifically cleaves the ribonucleic acid site of hairpin DNA to expose toehold sequences. The liberated toehold sequence may act as a primer to trigger a cyclic exponential amplification reaction for the generation of enormous signal strands that bind with the Cy5/biotin-labeled probes to form sandwich hybrids. The assembly of sandwich hybrids onto 605QD obtains 605QD-dsDNA-Cy5 nanostructures, inducing efficient FRET between the 605QD donor and Cy5 acceptor. Notably, the introduction of a mismatched base in hairpin DNA can greatly minimize the background and improve the signal-to-noise ratio. This nanosensor achieves a dynamic range of 1.0 × 10-8 to 0.1 ng/µL and a detection limit of 155.78 aM, and it can screen MGMT inhibitors and monitor cellular MGMT activity with single-cell sensitivity. Moreover, it can distinguish the MGMT level in tissues of breast cancer patients and healthy persons, holding great potential in clinical diagnostics and epigenetic research studies.

Elongation and Ligation-Mediated Differential Coding for Label-Free and Locus-Specific Analysis of 8-Oxo-7,8-dihydroguanine in DNA.

Oxidative DNA damage is closely associated with the occurrence of numerous human diseases and cancers. 8-Oxo-7,8-dihydroguanine (8-oxoG) is the most prevalent form of DNA damage, and it has become not only an oxidative stress biomarker but also a new epigenetic-like biomarker. However, few approaches are available for the locus-specific detection of 8-oxoG because of the low abundance of 8-oxoG damage in DNA and the limited sensitivity of existing assays. Herein, we demonstrate the elongation and ligation-mediated differential coding for label-free and locus-specific analysis of 8-oxoG in DNA. This assay is very simple without the involvement of any specific labeled probes, complicated steps, and large sample consumption. The utilization of Bsu DNA polymerase can specifically initiate a single-base extension reaction to incorporate dATP into the opposite position of 8-oxoG, endowing this assay with excellent selectivity. The introduction of cascade amplification reaction significantly enhances the sensitivity. The proposed method can monitor 8-oxoG with a limit of detection of 8.21 × 10-19 M (0.82 aM), and it can identify as low as 0.001% 8-oxoG damage from a complex mixture with excessive undamaged DNAs. This method can be further applied to measure 8-oxoG levels in the genomic DNA of human cells under diverse oxidative stress, holding prospect potential in the dynamic monitoring of critical 8-oxoG sites, early clinical diagnosis, and gene damage-related biomedical research.

Construction of single-molecule counting-based biosensors for DNA-modifying enzymes: A review.

DNA-modifying enzymes act as critical regulators in a wide range of genetic functions (e.g., DNA damage & repair, DNA replication), and their aberrant expression may interfere with regular genetic functions and induce various malignant diseases including cancers. DNA-modifying enzymes have emerged as the potential biomarkers in early diagnosis of diseases and new therapeutic targets in genomic research. Consequently, the development of highly specific and sensitive biosensors for the detection of DNA-modifying enzymes is of great importance for basic biomedical research, disease diagnosis, and drug discovery. Single-molecule fluorescence detection has been widely implemented in the field of molecular diagnosis due to its simplicity, high sensitivity, visualization capability, and low sample consumption. In this paper, we summarize the recent advances in single-molecule counting-based biosensors for DNA-modifying enzyme (i.e, alkaline phosphatase, DNA methyltransferase, DNA glycosylase, flap endonuclease 1, and telomerase) assays in the past four years (2019 - 2023). We highlight the principles and applications of these biosensors, and give new insight into the future challenges and perspectives in the development of single-molecule counting-based biosensors.