Dual-Amplification Strategy-Based SERS Chip for Sensitive and Reproducible Detection of DNA Methyltransferase Activity in Human Serum

DNA Origami Plasmonic Nanoantenna for Programmable Biosensing of Multiple Cytokines in Cancer Immunotherapy

Herein, we report a DNA origami plasmonic nanoantenna for the programmable surface-enhanced Raman scattering (SERS) detection of cytokine release syndrome (CRS)-associated cytokines (e.g., tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ)) in cancer immunotherapy. Typically, the nanoantenna was made of self-assembled DNA origami nanotubes (diameter: ∼19 nm; length: ∼90 nm) attached to a silver nanoparticle-modified silicon wafer (AgNP/Si). Each DNA origami nanotube contains one miniature gold nanorod (AuNR) inside (e.g., length: ∼35 nm; width: ∼7 nm). Intriguingly, TNF-α and IFN-γ logically regulate the opening of the nanotubes and the dissociation of the AuNRs from the origami structure upon binding to their corresponding aptamers. On this basis, we constructed a complete set of Boolean logic gates that read cytokine molecules as inputs and return changes in Raman signals as outputs. Significantly, we demonstrated that the presented system enables the quantification of TNF-α and IFN-γ in the serum of tumor-bearing mice receiving different types of immunotherapies (e.g., PD1/PD-L1 complex inhibitors and STING agonists). The sensing results are consistent with those of the ELISA. This strategy fills a gap in the use of DNA origami for the detection of multiple cytokines in real systems.

Buoyant Metal-Organic Framework Corona-Driven Fast Isolation and Ultrasensitive Profiling of Circulating Extracellular Vesicles

Accurately assaying tumor-derived circulating extracellular vesicles (EVs) is fundamental in noninvasive cancer diagnosis and therapeutic monitoring but limited by challenges in efficient EV isolation and profiling. Here, we report a bioinspired buoyancy-driven metal-organic framework (MOF) corona that leverages on-bubble coordination and dual-encoded surface-enhanced Raman scattering (SERS) nanotags to streamline rapid isolation and ultrasensitive profiling of plasma EVs in a single assay for cancer diagnostics. This integrated bubble-MOF-SERS EV assay (IBMsv) allows barnacle-like high-density adhesion of MOFs on a self-floating bubble surface to enable fast isolation (2 min, near 90% capture efficiency) of tumor EVs via enhanced EV-MOF binding. Also, IBMsv harnesses four-plexed SERS nanotags to profile the captured EV surface protein markers at a single-particle level. Such a sensitive assay allows multiplexed profiling of EVs across five cancer types, revealing heterogeneous EV surface expression patterns. Furthermore, the IBMsv assay enables cancer diagnosis in a pilot clinical cohort (n = 55) with accuracies >95%, improves discrimination between cancer and noncancer patients via an algorithm, and monitors the surgical treatment response from hepatocellular carcinoma patients. This assay provides a fast, sensitive, streamlined, multiplexed, and portable blood test tool to enable cancer diagnosis and response monitoring in clinical settings.

Importance of DNA nanotechnology for DNA methyltransferases in biosensing assays

DNA methylation is the process by which specific bases on a DNA sequence acquire methyl groups under the catalytic action of DNA methyltransferases (DNMT). Abnormal changes in the function of DNMT are important markers for cancers and other diseases; therefore, the detection of DNMT and the selection of its inhibitors are critical to biomedical research and clinical practice. DNA molecules can undergo intermolecular assembly to produce functional aggregates because of their inherently stable physical and chemical properties and unique structures. Conventional DNMT detection methods are cumbersome and complicated processes; therefore, it is necessary to develop biosensing technology based on the assembly of DNA nanostructures to achieve rapid analysis, simple operation, and high sensitivity. The design of the relevant program has been employed in life science, anticancer drug screening, and clinical diagnostics. In this review, we explore how DNA assembly, including 2D techniques like hybridization chain reaction (HCR), rolling circle amplification (RCA), catalytic hairpin assembly (CHA), and exponential isothermal amplified strand displacement reaction (EXPAR), as well as 3D structures such as DNA tetrahedra, G-quadruplexes, DNA hydrogels, and DNA origami, enhances DNMT detection. We highlight the benefits of these DNA nanostructure-based biosensing technologies for clinical use and critically examine the challenges of standardizing these methods. We aim to provide reference values for the application of these techniques in DNMT analysis and early cancer diagnosis and treatment, and to alert researchers to challenges in clinical application.

Fluorogenic RNA Aptamer-Based Amplification and Transcription Strategy for Label-free Sensing of Methyltransferase Activity in Complex Matrixes

DNA methyltransferase is significant in cellular activities and gene expression, and its aberrant expression is closely linked to various cancers during initiation and progression. Currently, there is a great demand for reliable and label-free techniques for DNA methyltransferase evaluation in tumor diagnosis and cancer therapy. Herein, a low-background fluorescent RNA aptamer-based sensing approach for label-free quantification of cytosine-guanine (CpG) dinucleotides methyltransferase (M.SssI) is reported. The fluorogenic light-up RNA aptamers-based strategy exhibits high selectivity via restriction endonuclease, padlock-based recognition, and RNA transcription. By combining rolling circle amplification (RCA), and RNA transcription with fluorescence response of RNA aptamers of Spinach-dye compound, the proposed platform exhibited efficiently ultrahigh sensitivity toward M.SssI. Eventually, the detection can be achieved in a linear range of 0.02-100 U mL-1 with a detection limit of 1.6 × 10-3 U mL-1. Owing to these superior features, the method is further applied in serum samples spiked M.SssI, which delivers a recovery ranging from 92.0 to 107.0% and a relative standard deviation <7.0%, providing a promising and practical tool for determining M.SssI in complex biological matrices.

Ultrasensitive electrochemical detection and inhibition evaluation of DNA methyltransferase based on cascade strand displacement amplification

An electrochemical sensing approach for ultrasensitive DNA methyltransferase (MTase) activity assay is proposed. After specific cleavage reaction in the presence of a methylated state, strand displacement polymerization (SDP) is initiated in the solution. The product of upstream SDP further triggers downstream SDP, which enriches abundant electrochemical species at the electrode. The whole process is quite convenient with shared enzymes. Due to the cascade signal amplification, ultrahigh sensitivity is promised. Inhibitor screening results are also demonstrated to be good. Besides, target MTase can be accurately determined in human serum samples, confirming excellent practical utility. This work provides a reliable approach for the analysis of MTase activity, which is of vital importance for related biological studies and clinical applications.

Ultrasensitive discrimination of volatile organic compounds using a microfluidic silicon SERS artificial intelligence chip

Current gaseous sensors hardly discriminate trace volatile organic compounds at the ppt level. Herein, we present an integrated platform for simultaneously enabling rapid preconcentration, reliable surface-enhanced Raman scattering, (SERS) detection and automatic identification of trace aldehydes at the ppt level. For rapid preconcentration, we demonstrate that the nozzle-like microfluidic concentrator allows the enrichment of rare gaseous analytes by five-fold in only 0.01 ms. The enriched gas is subsequently captured and detected by an integrated silicon-based SERS chip, which is made of zeolitic imidazolate framework-8 coated silver nanoparticles grown in situ on a silicon wafer. After SERS measurement, a fully connected deep neural network is built to extract faint features in the spectral dataset and discriminate volatile organic compound classes. We demonstrate that six kinds of gaseous aldehydes at 100 ppt could be detected and classified with an identification accuracy of ∼80.9% by using this platform.

CRISPR Cas12a-Powered Silicon Surface-Enhanced Raman Spectroscopy Ratiometric Chip for Sensitive and Reliable Quantification

Sensitive and reliable clustered regularly interspaced short palindromic repeats (CRISPR) quantification without preamplification of the sample remains a challenge. Herein, we report a CRISPR Cas12a-powered silicon surface-enhanced Raman spectroscopy (SERS) ratiometric chip for sensitive and reliable quantification. As a proof-of-concept application, we select the platelet-derived growth factor-BB (PDGF-BB) as the target. We first develop a microfluidic synthetic strategy to prepare homogeneous silicon SERS substrates, in which uniform silver nanoparticles (AgNPs) are in situ grown on a silicon wafer (AgNPs@Si) by microfluidic galvanic deposition reactions. Next, one 5'-SH-3'-ROX-labeled single-stranded DNA (ssDNA) is modified on AgNPs via Ag-S bonds. In our design, such ssDNA has two fragments: one fragment hybridizes to its complementary DNA (5'-Cy3-labeled ssDNA) to form double-stranded DNA (dsDNA) and the other fragment labeled with 6'-carboxy-X-rhodmine (ROX) extends out as a substrate for Cas12a. The cleavage of the ROX-tagged fragment by Cas12a is controlled by the presence or not of PDGF-BB. Meanwhile, Cy3 molecules serving as internal standard molecules still stay at the end of the rigid dsDNA, and their signals remain constant. Thereby, the ratio of ROX signal intensity to Cy3 intensity can be employed for the reliable quantification of PDGF-BB concentration. The developed chip features an ultrahigh sensitivity (e.g., the limit of detection is as low as 3.2 pM, approximately 50 times more sensitive than the fluorescence counterpart) and good reproducibility (e.g., the relative standard deviation is less than 5%) in the detection of PDGF-BB.

A fluorescent biosensor based on exponential amplification reaction-initiated CRISPR/Cas12a (EIC) strategy for ultrasensitive DNA methyltransferase detection

DNA methyltransferase (DNA MTase) catalyzes the process of DNA methylation, and the aberrant DNA MTase activity is closely associated with cancer incidence and progression. Inspired by the exponential amplification reaction (EXPAR) characteristics, we developed an EXPAR-initiated CRISPR/Cas12a (EIC) strategy for sensitively detecting DNA MTase activity. A hairpin probe (HP) was designed with a palindromic sequence in the stem as substrate and NH₂-modified 3' end to prevent nonspecific amplification. HP could be methylated by DNA adenine methyltransferase (Dam MTase) and then digested by DpnI to generate an oligonucleotide that can serve as an EXPAR primer. With the assistance of Nt.BstNBI nicking enzyme and Vent(exo-) polymerase, this primer bound to template and induced EXPAR. Interestingly, the product of Cycle 1 in EXPAR can function as primer to initiate Cycle 2. Both EXPAR products can further activate the collateral cleavage of CRISPR/Cas12a-crRNA, resulting in the fragmentation of fluorescence reporters and fluorescence recovery. Due to the highly efficient amplification (about 5 times signal-to-noise of SDA) and the robust trans-cleavage of CRISPR/Cas12a, the EIC system owned an extreme limit of detection (LOD) of 2 × 10^-4 U/mL and a broad detection range from 2 × 10^-4 to 10 U/mL for Dam MTase. In addition, this method has succeeded in inhibitor screening and evaluation, showing magnificent promise in drug discovery and cancer therapy.

Simple Detection of DNA Methyltransferase with an Integrated Padlock Probe

DNA methyltransferases (MTases) can be regarded as biomarkers, as demonstrated by many studies on genetic diseases. Many researchers have developed biosensors to detect the activity of DNA MTases, and nucleic acid amplification, which need other probe assistance, is often used to improve the sensitivity of DNA MTases. However, there is no integrated probe that incorporates substrates and template and primer for detecting DNA MTases activity. Herein, we first designed a padlock probe (PP) to detect DNA MTases, which combines target detection with rolling circle amplification (RCA) without purification or other probe assistance. As the substrate of MTase, the PP was methylated and defended against HpaII, lambda exonuclease, and ExoI cleavage, as well as digestion, by adding MTase and the undestroyed PP started RCA. Thus, the fluorescent signal was capable of being rapidly detected after adding SYBR^TM Gold to the RCA products. This method has a detection limit of approximately 0.0404 U/mL, and the linear range was 0.5–110 U/mL for M.SssI. Moreover, complex biological environment assays present prospects for possible application in intricacy environments. In addition, the designed detection system can also screen drugs or inhibitors for MTases.

Methylation-blocked cascade strand displacement amplification for rapid and sensitive fluorescence detection of DNA methyltransferase activity

DNA methylation catalyzed by DNA adenine methylation methyltransferase (Dam MTase) is strongly connected with a variety of biological processes, hence, monitoring Dam MTase activity is of great importance. Here, we developed a rapid and sensitive fluorescence sensing strategy for the detection of Dam MTase activity based on methylation-blocked enzymatic recycling amplification. In this fluorescence sensing system, Dam MTase-induced methylation blocked the subsequent reactions. In contrast, in the absence of Dam MTase, the unmethylated probe initiated the cascade strand displacement amplification for significant signal amplification. Under optimized conditions, this method has a lower detection limit of 0.67 U/mL and a shorter assay time (90 min) compared with previously reported similar methodologies.

Plasmonic Au nanocube enhanced SERS biosensor based on heated electrode and strand displacement amplification for highly sensitive detection of Dam methyltransferase activity

In this work, a novel "turn-on" mode Au nanocubes (AuNCs) enhanced surface-enhanced Raman scattering (SERS) biosensing platform coupled with heated Au electrode (HAuE) and strand displacement amplification (SDA) strategy was proposed for highly sensitive detection of DNA adenine methylation (Dam) Methyltransferase (MTase) activity. The Dam MTase and DpnI enzyme activities were significantly increased by elevating the HAuE surface temperature, resulting in the rapid production of template DNA for later SDA. During the SDA process, the released single-stranded DNA (ssDNA) could be amplified exponentially, and its concentration was positively related to the Dam MTase activity. The plasmonic AuNCs in SERS tags could provide significant SERS enhancement due to their "lightning rod" effect resulting from the sharp feature of the edges and corners of AuNCs. Because of these factors, the proposed biosensors exhibited high sensitivity in detecting the Dam MTase activity. The limit of detection was estimated to be 8.65 × 10^-5 U mL^-1, which was lower than that in most of the sensors for detection of Dam MTase activity in the literature. This SERS biosensor could also be used to screen inhibitors of Dam MTase and had the potential for detecting Dam MTase activity in real biological samples.

An entropy-driven signal-off DNA circuit for label-free, visual detection of small molecules with enhanced accuracy

An entropy-driven DNA circuit offers an efficient means of sensitive analyte detection with signal amplification. In this article, we rationally engineered an aptamer-based entropy-driven signal-off DNA circuit for colorimetric detection of small molecules. The proposed signal-off DNA circuit is activated by target small molecule binding to drive the collapse of G-quadruplex DNAzyme, accompanied by the colour change of the detection solution from dark blue to light blue. Entropy-driven recycling hybridization significantly magnified the input signal of the target small molecule. Such an assay enables naked-eye detection of adenosine triphosphate and oxytetracycline at concentrations as low as 0.5 μM and 1 μM respectively. Moreover, when compared with the signal-on DNA circuit, the entropy-driven signal-off DNA circuit for colorimetric detection has two advantages. Firstly, unlike in the signal-on DNA circuit, the unavoidable formation of waste complexes in the absence of a target in the signal-off DNA circuit has no influence on target detection performance as its background signal is only determined by the substrate complex. Secondly, the signal-on DNA circuit cannot distinguish false-positive signals generated by invasive catalysts (e.g., HRP, serum, Fe₃O₄), while the signal-off DNA circuit can distinguish those signals as undesired signals. Overall, the signal-off DNA circuit affords a novel strategy for sensitive and accurate detection of small molecules.

Metal coordination induced SERS nanoprobe for sensitive and selective detection of histamine in serum

Sensitivity and credibility detecting histamine (HA) as an important neurotransmitter in biofluids is of importance in analytical science and physiology. Surface-enhanced Raman spectroscopy (SERS) is able to realize the high sensitivity with single molecules level, but providing the high sensitivity for HA with a small cross section remains a challenge. Here we develop the metal complex-based SERS nanoprobe nitrilotriacetic acid-Ni²⁺ (NTA-Ni²⁺) combined with self-assemble Au NPs active substrates for sensitive detection of HA. The NTA-Ni²⁺ can capture the HA molecules close to Au NPs substrates and then amplify the Raman signals of HA owing to the formation of a complex of NTA-Ni²⁺-HA. The self-assemble Au film through the evaporation-driven method can provide the high-density hot spots substrate with high stability and reproducibility. The NTA-Ni²⁺ decorated Au NPs as nanoprobe responds to HA with 1 μM level of sensitivity. More importantly, the developed SERS nanoprobe composing of NTA-Ni²⁺ and self-assemble Au NPs can be utilized to detect and monitor the HA spiked into serum, indicating the potential prospect in analysis of HA in complex specimen.

A review on colorimetric assays for DNA virus detection

Early detection is one of the ways to deal with DNA virus widespread prevalence, and it is necessary to know new diagnostic methods and techniques. Colorimetric assays are one of the most advantageous methods in detecting viruses. These methods are based on color change, which can be seen either with the naked eye or with special devices. The aim of this study is to introduce and evaluate effective colorimetric methods based on amplification, nanoparticle, CRISPR/Cas, and Lateral flow in the diagnosis of DNA viruses and to discuss the effectiveness of each of the updated methods. Compared to the other methods, colorimetric assays are preferred for faster detection, high efficiency, cheaper cost, and high sensitivity and specificity. It is expected that the spread of these viruses can be prevented by identifying and developing new methods.

Detection of Mercury Ion with High Sensitivity and Selectivity Using a DNA/Graphene Oxide Hybrid Immobilized on Glass Slides

Excessive mercury ions (Hg²⁺) cause great pollution to soil/water and pose a major threat to human health. The high sensitivity and high selectivity in the Hg²⁺ detection demonstrated herein are significant for the research areas of analytical chemistry, chemical biology, physical chemistry, drug discovery, and clinical diagnosis. In this study, a series of simple, low-cost, and highly sensitive biochips based on a graphene oxide (GO)/DNA hybrid was developed. Hg²⁺ is detected with high sensitivity and selectivity by GO/DNA hybrid biochips immobilized on glass slides. The performance of the biosensors can be improved by introducing more phosphorothioate sites and complementary bases. The best limit of detection of the biochips is 0.38 nM with selectivity of over 10:1. This sensor was also used for Hg²⁺ detection in Dendrobium. The results show this biochip is promising for Hg²⁺ detection.

Cyclometalated Iridium(III) Complex-Sensitized NiO-Based-Cathodic Photoelectrochemical Platform for DNA Methyltransferase Assay

This work reports an efficient [(C6)₂Ir(dppz)]⁺PF₆^- (C6 = coumarin 6 and dppz = dipyridophenazine)-sensitized NiO photocathode and its application in photoelectrochemical (PEC) bioanalysis field for the first time. This dye-sensitized NiO photocathode was found to exhibit a markedly enhanced cathodic photocurrent. A sensitive cathodic PEC platform was proposed integrating the as-prepared photocathode with enzyme-free cascaded amplification strategies of the catalytic hairpin assembly (CHA) and the hybridization chain reaction (HCR) for DNA methyltransferase (MTase) assay. A hairpin DNA(H_Dam) with specific recognition site of Dam MTase in its stem was designed. The site of H_Dam was methylated in the presence of Dam MTase and then cut by endonuclease DpnI. The released loop fragment, as an initiator, triggered the CHA circuit and the follow-up HCR circuit, resulting in long dsDNA concatemers on the ITO electrode. Numerous [(C6)₂Ir(dppz)]⁺PF₆^- were intercalated into dsDNA, and highly efficient signal amplification was realized. Benefiting from the superior iridium(III) complex-sensitized NiO photocathode and effective amplification strategy, a detection limit of 0.0028 U/mL for the determination of Dam MTase was achieved. Moreover, this work further demonstrated that these proposed tactics could be applied to screen Dam MTase activity inhibitors.

A novel DNA biosensor for the ultrasensitive detection of DNA methyltransferase activity based on a high-density "hot spot" SERS substrate and rolling circle amplification strategy

Herein, we proposed a novel biosensor based on a high-density "hot spot" Au@SiO₂ array substrate and rolling circle amplification (RCA) strategy for the ultrasensitive detection of CpG methyltransferase (M.SssI) activity. In the presence of M.SssI, the RCA process can be triggered, causing the augmentation of the single-stranded DNA (ssDNA) at the tail of the double-stranded DNA (dsDNA), and the ssDNA can be hybridized with numerous DNA probes labeled with Raman reporters in the next steps. Afterwards, the resultant ssDNA can be modified to the Au@SiO₂ array substrate with the SERS enhancement factor of 7.49 × 10⁶. The substrate was synthesized by using a monolayer SiO₂ array to pick up the Au nanoparticle (AuNP) array and finite-difference time-domain (FDTD) simulation showed its excellent SERS effect. Particularly, the developed biosensor displayed a significant sensitivity with a broad detection range covering from 0.005 to 50 U mL^-1, and the limits of detection (LODs) in PBS buffer and human serum were 2.37 × 10^-4 U mL^-1 and 2.51 × 10^-4 U mL^-1, respectively. Finally, in order to verify the feasibility of its clinical application, the serum samples of healthy subjects and breast cancer, prostate cancer, gastric cancer and cervical cancer patients were analyzed, and the reliability of the results was also confirmed by western blot (WB) experiments. Taking advantage of these merits, the proposed biosensor can be a very promising alternative tool for the detection of M.SssI activity, which is of vital importance in the early detection and prevention of tumors.

Ultrasensitive DNA methyltransferase activity sensing and inhibitor evaluation with highly photostable upconversion nanoparticle transducer

Sensitive and accurate detection of DNA methyltransferase (MTase) is conducive to the understanding of the fundamental biological processes related to DNA methylation, clinical disease diagnosis, and drug discovery. Herein, a new fluorescence transducer based on Förster resonance energy transfer (FRET) between the donor upconversion nanoparticles (UCNPs) and the efficient acceptor gold nanorods (AuNRs) for MTase activity analysis and its inhibitor screening is presented. A double-strand DNA linker between UCNPs and AuNRs could be digested by restriction endonuclease HhaI, preventing the FRET process and recovering the upconversion luminescence (UCL) intensity. With the treatment of MTase, the cutting site was disturbed by the methylation of cytosine, blocking the enzyme digestion. The transducer presented here showed an excellent analytical performance toward MTase M.HhaI in the concentration range 0.08~24 U mL-1 with a detection limit of 0.057 U mL-1 calculated according to the UCL intensity changes at 656 nm excited by 980 nm CW laser, which is superior to most of the reported methods. Furthermore, the as-fabricated transducer also demonstrated high testing and screening capability toward enzyme inhibitors' evaluation. The method takes the advantage of low background fluorescence of UCNPs to improve the accuracy of the measurement, which can be developed as a general strategy for the analysis of various disease-related methyltransferase activity and their corresponding inhibitors, offering a promising strategy for high-performance diagnosis, high-efficient drug exploitation, and treatment effectiveness evaluation.

A review of aptamer-based SERS biosensors: Design strategies and applications

Surface-enhanced Raman spectroscopy, due to its high sensitivity, unique vibrational fingerprint identification of molecules and easy operation, has been extensively applied in different fields. Aptamers, being the unique single stranded DNA/RNA sequences that can specifically recognize and seize the target analytes, combined with Surface-enhanced Raman spectroscopy (SERS), can offer potent multiplex detection capacity with high specificity and sensitivity. In this review, we summarize and classify the general working strategies of different types of aptamer-based SERS biosensors with diversified protocols which either take aptamer conformational change as intrinsic reporter, or make use of various extrinsic Raman reporters in different sensor designs via on/off approach, sandwich-type and magnetic nanoparticles (NPs)-assisted approach, and catalytic reaction assisted approach with amplification of alternative Raman signals. The advantages, applications and perspectives of these aptamer-based SERS biosensors are also discussed.

Unsupported liquid-state platform for SERS-based determination of triazophos

A highly reproducible surface-enhanced Raman scattering (SERS) unsupported liquid-state platform (ULP) was developed for accurate quantitative determination of triazophos. Herein, citrate-reduced Ag NPs suspension was concentrated and placed in a stainless steel perforated template to form the SERS ULP. The relative standard deviation of the SERS measurements was less than 5% (n ≥ 10), and the R² of the calibration curve was 0.994. The developed SERS ULP was applied for determination of triazophos in spiked agricultural products (rice, cabbage, and apple). Experiment results showed that the coefficient of variation ranged from 5.3 to 6.2% for intra-day and from 5.5 to 6.3% for inter-day (n = 3), which proved excellent SERS reproducibility. Moreover, the results were in good agreement with those from HPLC analysis. As a liquid-state SERS substrate, the highly reproducible ULP can perform precision quantitative analysis without surface modification of NPs, which is a significant improvement. This method provides a new perspective for quantitative SERS analysis of pesticide residues. Graphical abstract.

A dual signal amplification strategy for the highly sensitive fluorescence detection of nucleic acids

A dual signal amplification strategy comprising target-triggered recycling and DSN-mediated amplifications was designed and proposed for a highly sensitive fluorescence assay of nucleic acids.

Immuno-DNA binding directed template-free DNA extension and enzyme catalysis for sensitive electrochemical DNA methyltransferase activity assay and inhibitor screening

A new electrochemical immuno-DNA sensing platform for DNA methyltransferase activity assay and inhibitor screening.

Graphene Oxide-Assisted and DNA-Modulated SERS of AuCu Alloy for the Fabrication of Apurinic/Apyrimidinic Endonuclease 1 Biosensor

Fabrication of high-performance surface-enhanced Raman scattering (SERS) biosensors relies on the coordination of SERS substrates and sensing strategies. Herein, a SERS active AuCu alloy with a starfish-like structure is prepared using a surfactant-free method. By covering the anisotropic AuCu alloy with graphene oxide (GO), enhanced SERS activity is obtained owing to graphene-enhanced Raman scattering and assembly of Raman reporters. Besides, stability of SERS is promoted based on the protection of GO to the AuCu alloy. Meanwhile, it is found that SERS activity of AuCu/GO can be regulated by DNA. The regulation is sequence and length dual-dependent, and short polyT reveals the strongest ability of enhancing the SERS activity. Relying on this phenomenon, a SERS biosensor is designed to quantify apurinic/apyrimidinic endonuclease 1 (APE1). Because of the APE1-induced cycling amplification, the biosensor is able to detect APE1 sensitively and selectively. In addition, APE1 in human serum is analyzed by the SERS biosensor and enzyme-linked immunosorbent assay (ELISA). The data from the SERS method are superior to that from ELISA, indicating great potential of this biosensor in clinical applications.