The increasing use of automated laser welding processes causes high demands on process monitoring. This work demonstrates methods that use a camera mounted on the focussing optics to perform pre-, ...in-, and post-process monitoring of welding processes. The implementation uses machine learning methods. All algorithms consider the integration into industrial processes. These challenges include a small database, limited industrial manufacturing inference hardware, and user acceptance.
Photoelectrochemical (PEC) DNA bioanalysis has been drawing more attention in recent years due to the advantages of PEC technique and the vital importance of DNA biomolecules. DNAzymes are unique ...catalytic nucleic acid molecules that are capable of catalyzing specific biochemical reactions. Using the target-binding-induced conformation change of hairpin DNA probe to hemin/G-quadruplex-based DNAzyme and a plasmonic Au@Ag nanoparticles (NPs)/TiO
nanorods (NRs)/fluorine-doped tin oxide (FTO) heterostructured photoelectrode, this work reported a novel and sensitive PEC DNA analysis on the basis of a DNAzyme-stimulated biocatalytic precipitation (BCP) strategy. In such a design, the BCP-induced decrease of plasmonic photocurrent can be related to the target-responsive formation of DNAzymes and thus be monitored to assay the target DNA from 0.1 and 100 nM. In brief, with a plasmonic photoelectrode and a hairpin probe, this work reported a general plasmonic DNAzyme-based PEC DNA analysis, which could also be easily extended to aptasensing toward numerous targets of interest.
The anti-apoptotic protein survivin is one of the most promising cancer biomarkers owing to its high expression in human cancers and rare occurrence in normal adult tissues. In this work, we have ...investigated the role of supramolecular interactions between a graphene oxide (GO) nanosheet nanocarrier and a survivin molecular beacon (SurMB), functionalized by attaching fluorophore Joe and quencher Dabcyl (SurMB-Joe). Molecular dynamics simulations revealed hydrogen bonding of Joe moiety and Dabcyl to GO carriers that considerably increase the SurMB-GO bonding strength. This was confirmed in experimental work by the reduced fluorescence background in the OFF state, thereby increasing the useful analytical signal range for mRNA detection. A new mechanism of hairpin⁻hairpin interaction of GO@SurMB with target oligonucleotides has been proposed. A low limit of detection, LOD = 16 nM (S/N = 3), has been achieved for complementary tDNA using GO@SurMB-Joe nanocarriers. We have demonstrated an efficient internalization of SurMB-Joe-loaded GO nanocarriers in malignant SW480 cells. The proposed tunability of the bonding strength in the attached motifs for MBs immobilized on nanocarriers, via structural modifications, should be useful in gene delivery systems to enhance the efficacy of gene retention, cell transfection and genomic material survivability in the cellular environment.
In numerous malignancies, miRNA-155 is overexpressed and has oncogenic activity because it is one of the most efficient microRNAs for inhibiting apoptosis in human cancer cells. As a result, the ...highest sensitive detection of the miRNA-155 gene is a technological instrument that can enable early cancer screening. In this study, a miRNA-155 biosensor was created to create a hairpin probe that can bind to the miRNA-155 gene using lambda nucleic acid exonuclease, which can cut the 5′ phosphorylated double strand, and by the DNA probe is recognized by the Cas12a enzyme, which then activates Cas12a to catalyze trans-cutting produces strong fluorescence. Research finding, the target concentration's logarithm and corresponding fluorescence intensity have a strong linear connection, and the limit of detection (LOD) of the sensing system was determined to be 8.3 pM. In addition, the biosensor displayed exceptional specificity, low false-positive signal, and high sensitivity in detecting the miRNA-155 gene in serum samples. This study's creation of a biosensor that has high sensitivity, good selectivity, and is simple to operate provides promising opportunities for research into biosensor design and early cancer detection.
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•A highly sensitive biosensor for miRNA-155 detection using λ exonuclease and CRISPR/ cas12a assisted amplification was constructed.•An ultra-sensitive detection sensor platform for miRNA-155 with a detection limit of 8.3 pM.•The biosensor is suitable for the complex human serum environment, and the technology is portable.
The COVID-19 pandemic, caused by the novel coronavirus, has had a profound impact on global health and economies worldwide. This unprecedented crisis has affected individuals, communities, and ...nations in diverse manners. Developing simple and accurate diagnostic methods is an imperative task for frequent testing to mitigate the spread of the virus. Among these methods, SARS-CoV-2 antigen tests in clinical specimens have emerged as a promising diagnostic method for COVID-19 due to their sensitive and accurate detection of spike (S) protein, which plays a crucial role in viral infection initiation.
In this work, a dual-signal amplification surface enhanced Raman scattering (SERS)-based S protein biosensor was constructed based on Au NPs/COFs and enzyme-free catalytic hairpin assembly (CHA) amplification method. The approach relies on a released free DNA sequence (T), which is generated from the competition reaction between Aptamer/T and Aptamer/S protein, to trigger a CHA reaction. Due to the high binding affinity and selectivity between the S protein and its aptamer, CHA process was triggered with the maximum SERS tags (H2-conjugated Au@4-mercaptobenzonitrile@Ag) anchored onto Au NPs/COFs substrate surface. This SERS platform could detect the S protein at concentrations with high sensitivity (limit of detection = 3.0 × 10−16 g/mL), wide detection range (1 × 10−16 to 1 × 10−11 g/mL), acceptable reproducibility (relative standard deviation = 7.01 %) and excellent specificity. The biosensor was also employed to detect S protein in artificial human salivas.
Thus, this study not only developed a novel Au NPs/COFs substrate exhibiting strong SERS enhancement ability and high reproducibility, but also proposed a promising dual-signal amplification SERS-based diagnostic method for COVID-19, holding immense potential for the detection of a wide range of antigens and infectious diseases in future applications.
An ideal dual-signal amplification biosensor was constructed based on catalytic-hairpin-assembly amplification technology integrated with Au@4-MBN@Ag SERS tags and hierarchical sheaf-like Au NPs/COFs substrate, which achieved the sensitive detection of SARS-CoV-2 spike protein. Display omitted
•A dual-signal amplification SERS platform was proposed for sensitive SARS-CoV-2 S protein diagnosis with high sensitivity.•A hierarchical sheaf-like Au/COFs microrod was fabricated with excellent SERS enhancement ability and reproducibility.•The innovative designed CHA amplification strategy generated more hotspots and further increased the detection sensitivity.
HIV-1 RNA dimerization is a critical step in viral life cycle. It is a prerequisite for genome packaging and plays an important role in reverse transcription and recombination. Dimerization is ...promoted by the DIS (dimerization initiation site) hairpin located in the 5' leader of HIV-1 genome. Despite the high genetic diversity in HIV-1 group M, only five apical loops (AAGCGCGCA, AAGUGCGCA, AAGUGCACA, AGGUGCACA and AGUGCAC) are commonly found in DIS hairpins. We refer to the parent DISes with these apical loops as DIS
, DIS
, DIS
, DIS
, and DIS
, respectively. Based on identity or similarity of DIS hairpins to parent DISes, we distributed HIV-1 M genomes into five dimerization groups. Comparison of the primary and secondary structures of DIS, SD and Psi hairpins in about 3000 HIV-1 M genomes showed that the mutation frequencies at particular nucleotide positions of these hairpins differ among the dimerization groups, and DIS
may be an origin of other parent DISes. We found that DIS, SD and Psi hairpins have hundreds of variants, only some of them occurring rather frequently. The lower part of DIS hairpin with G x AGG internal loop is highly conserved in both HIV-1 and SIV genomes. We supposed that the G-quadruplex, located 56 nts downstream of the Gag start codon, may participate in switching of HIV-1 leader RNA from BMH (branched multiple hairpins) to LDI (long distance interaction) conformation.
Echovirus 11 (ECHO 11) is a positive-stranded RNA virus. The infections of ECHO 11 are associated with many clinical syndromes, thus the deployment of rapid point-of-care diagnostics is necessary. ...This study reported a new diagnostic assay based on All-In-One CRISPR/Cas13a and a DNA circuit (termed AIOC) for ECHO 11 detection. By combination of CRISPR/Cas13a and catalytic hairpin assembly (CHA) circuit in one-pot reaction, multiple handling steps and uncapping contamination could be effectively avoided. After recognition of target RNA, the activation of CRISPR/Cas13a induced the RNase activity of Cas13a to cleave hairpin probes, resulting in subsequent CHA amplification. This simplified assay was able to detect ECHO 11 RNA in the range of 500 × 10-18 M to 5 × 10-9 M for VP1 gene and 100 × 10-18 M to 5 × 10-9 M for RdRP gene. And the limit of detection was 152 × 10-18 M and 24 × 10-18 M, respectively. More importantly, the practicability of AIOC assay was validated by clinical ECHO samples. Taking together, the AIOC assay is rapid (∼30 min), isothermal (37 ℃), ultrasensitive, specific, user-friendly and does not need the step of RNA reverse-transcription, making it an excellent detection performance in one-pot point-of-care assay.
•An all-in-one assay for isothermal, ultrasensitive and specific detection of ECHO 11 RNA was developed.•The assay reduced the analysis time to 30 min.•Both the trans-cleavage activity of Cas13a and CHA circuit contribute to the signal amplification.•The detection performance of the proposed assay had been validated using clinical samples.•This assay can be used for other targets detection by flexibly designing the spacer region of crRNA.
•A novel fluorescent assay for Hg2+ detection based on graphene oxide and catalytic hairpins self-assembly have been presented.•The limit of detection was comparable or even better than enzyme-based ...or other enzyme-free amplification strategies.•This method provided an effective “turn-on” and sensitive approach for Hg2+ detection.
We have reported an enzyme-free amplification fluorescent strategy for ultra-sensitive detection of Hg2+ based on graphene oxide (GO) and catalytic hairpins self-assembly. Three fluorophore labled metastable hairpin DNA probes can be closely adsorbed onto GO surface via π−π stacking to quench the fluorescent signal. T-Hg2+-T interaction was utilized to induce the catalytic self-assembly of hairpins with the aid of helper DNA. The formed rigid DNA triangles containing double strand DNA (dsDNA) was stiffer, and released from the surface of GO to cause a “turn-on” fluorescent signal. The limit of detection was 25 pM, which was comparable with those reported amplification strategies. This strategy showed good selectivity for Hg2+, and promising application for real samples.
Accumulative evidences have indicated that abnormal expression of microRNAs (miRNAs) is closely associated with many health disorders, making them be regarded as potentialbiomarkers for early ...clinical diagnosis. Therefore, it is extremely necessary to develop a highly sensitive, specific and reliable approach for miRNA analysis. Catalytic hairpin assembly (CHA) signal amplification is an enzyme-free toehold-mediated strand displacement method, exhibiting significant potential in improving the sensitivity of miRNA detection strategies. In this review, we first describe the potential of miRNAs as disease biomarkers and therapeutics, and summarize the latest advances in CHA signal amplification-based sensing strategies for miRNA monitoring. We describe the characteristics and mechanism of CHA signal amplification and classify the CHA-based miRNA sensing strategies into several categories based on the “signal conversion substance”, including fluorophores, enzymes, nanomaterials, and nucleotide sequences. Sensing performance, limit of detection, merits and disadvantages of these miRNA sensing strategies are discussed. Moreover, the current challenges and prospects are also presented.
This review mainly described the potential of miRNAs as disease biomarkers and therapeutics, and summarized the latest advances in catalytic hairpin assembly (CHA) signal amplification-based sensing strategies for miRNA detection. Sensing performance, limitation of detection, advantages and disadvantages of these miRNA sensing strategies were discussed. Furthermore, the current challenges and prospects are also presented. Display omitted
•MiRNAs as potential disease biomarkers and therapeutics are shortly introduced.•This paper mainly reviews CHA-based sensing strategies for miRNA detection.•The performance of various CHA-based sensing strategies has been described.•Further trends and perspectives of CHA-based sensing platforms for miRNA detection are presented.
Recently, hairpin windings (HWs) have been among the most studied and implemented winding topologies to enhance torque and power density of electrical machines (EMs), especially in the automotive ...sector. The aim of this work is threefold. First, it proposes an asymmetrical configuration for HWs, which exploits the possibility of reducing AC losses through the implementation of conductors featuring variable cross-section within the slot. Second, this asymmetrical winding is envisioned using additive manufacturing (AM), given the constraints imposed by the conventional manufacturing process of HWs. Third, a suitable aluminium (Al) alloy is selected as winding material, thus replacing copper (Cu), with the aim of achieving a more sustainable design. These three objectives are achieved through extensive analytical and numerical analyses and comparisons between conventional and asymmetrical windings, as well as among different materials. A practical demonstrator is then built to validate analyses, methodologies and concepts proposed in this paper. Finally, an experimental campaign is carried out on the asymmetrical winding demonstrator, highlighting the loss reduction and sustainability potentials of the proposed layout.
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