Magnetic Recognition Research Articles

A SERS biosensor based on aptamer-based Fe3O4@SiO2@Ag magnetic recognition and embedded SERS probes for ultrasensitive simultaneous detection of Staphylococcus aureus and Escherichia coli

A rapid and sensitive SERS biosensor based on aptamer-modified Fe3O4@SiO2@Ag and Au-MPBA/DTNB@Ag was constructed for simultaneous detection of Staphylococcus aureus (S.aureus) and Escherichia coli (E.coli). This process can be simply described as a capture-enrichment-labeling (CEL) process. The monodisperse and strong magnetic Fe3O4@SiO2@Ag-P1/P2 can quickly capture and enrich pathogenic bacteria. Fe3O4@SiO2@Ag and Au@Ag synergistically enhanced the Raman signal of Raman reporters for labeling bacteria. Therefore, the dual-enhanced SERS biosensor can rapidly detect S. aureus and E. coli, and the limit of detection (LOD) is 1 CFU/mL, which is obviously superior to other SERS biosensors of the same type. It is proved to be effective in milk samples, and the total detection time is only 20 min. More importantly, when the aptamer is converted, the SERS biosensor can be used for other types of bacterial detection. The SERS biosensor based on dual-aptamer has the advantages of short analysis time, simple steps and high sensitivity.

A magnetic separation-assisted cascade hybridization chain reaction amplification strategy for sensitive detection of flap endonuclease 1

Sensitive and accurate detection of flap endonuclease 1 (FEN1) is essential to understand its roles in DNA replication and repair and explore its functions in tumor diagnosis and prognosis. Here, we designed a magnetic separation-assisted cascade hybridization chain reaction (HCR) amplification strategy for enzyme-free and sensitive detection of FEN1. Firstly, the forked dsDNAs contained the recognition site (5′ overhanging DNA flap) of FEN1 were modified on magbeads surface to form magnetic recognition probes. By the recognition and catalytic cleavage of FEN1, the 5′ flaps were removed into solution and then purified by magnetic separation. Then, the obtained flaps served as triggers to activate the linear-assembly of hairpin probes H1 and H2 (primary HCR), forming nicked double helices with split fragments. Finally, the fragments acted as new triggers to activate the branched-assembly of hairpin probes H3 and H4 (secondary HCR), causing fluorophore/quencher labeled on H3 far away and fluorescence recovery. Benefiting from the purification of triggers by magnetic separation and the signal amplification effect of cascade HCR, this strategy achieved a low detection limit of 3.6 × 10−5 U μL−1 for FEN1, and enabled the assay of it in actual samples. The results demonstrate that our strategy will provide a potent approach for sensitive detection of FEN1 in early tumor diagnosis and prognosis.

Aptamer-based novel Ag-coated magnetic recognition and SERS nanotags with interior nanogap biosensor for ultrasensitive detection of protein biomarker

• An innovative aptamer SERS biosensor for highly sensitive protein biomarker detection was presented. • The biosensor contains SERS tags and novel magnetic capture substrates. • Aptamers against CRP were modified on both SERS tag and magnetic capture substrate for specific recognition. • This method exhibits excellent selectivity and specificity and displays high accuracy in actual human serum samples. • This strategy can be extended to the detection of other biomarkers and hold great promise in the clinical diagnosis. The design of a rapid, simple, and ultrasensitive detection platform of protein biomarkers has become an urgent need in early diagnosis and treatment. Surface-enhanced Raman scattering (SERS) technology, with the unique advantages of ultra-sensitivity and fingerprint recognition, has attracted much attention in biomarker detection. An innovative aptamer SERS biosensor for highly sensitive protein biomarker detection was presented. This biosensor contains a SERS tag (reporter-labeled Au nano-bridged nanogaps particles, Au NNPs) and novel magnetic capture substrate (Ag-coated Fe 3 O 4 -Au NPs, Ag MNPs). C-reactive protein (CRP), a representative biomarker for diagnosing, was used to assess the SERS performance of this biosensor. Aptamers against CRP were modified on both SERS tag and magnetic capture substrate for specific recognition by Au NNPs-CRP-Ag MNPs sandwich assay. This strategy achieved sensitive detection of CRP with a limit of detection (LOD) of 10 fM (1.14 pg/mL), and is much lower than reported analytical methods. Besides, this method exhibits excellent selectivity and specificity for CRP under the interference of other proteins and displays high accuracy in the detection of actual human serum samples. This proposed detection strategy can be extended to the sensitive detection of other biomarker proteins and hold great promise in the clinical diagnosis of diseases.

Correction: Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood.

Correction for ‘Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood’ by Kaisong Yuan et al., Chem. Sci., 2018, DOI: 10.1039/c8sc04637a.

Antimicrobial peptide based magnetic recognition elements and Au@Ag-GO SERS tags with stable internal standards: a three in one biosensor for isolation, discrimination and killing of multiple bacteria in whole blood.

In this study, a new biosensor based on a sandwich structure has been developed for the isolation and detection of multiple bacterial pathogens via magnetic separation and SERS tags. This novel assay relies on antimicrobial peptide (AMP) functionalized magnetic nanoparticles as "capturing" probes for bacteria isolation and gold coated silver decorated graphene oxide (Au@Ag-GO) nanocomposites modified with 4-mercaptophenylboronic acid (4-MPBA) as SERS tags. When different kinds of bacterial pathogens are combined with the SERS tags, the "fingerprints" of 4-MPBA show corresponding changes due to the recognition interaction between 4-MPBA and different kinds of bacterial cell wall. Compared with the label-free SERS detection of bacteria, 4-MPBA here can be used as an internal standard (IS) to correct the SERS intensities with high reproducibility, as well as a Raman signal reporter to enhance the sensitivity and amplify the differences among the bacterial "fingerprints". Thus, three bacterial pathogens (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) were successfully isolated and detected, with the lowest concentration for each of the strains detected at just 101 colony forming units per mL (CFU mL-1). According to the changes in the "fingerprints" of 4-MPBA, three bacterial strains were successfully discriminated using discriminant analysis (DA). In addition, the AMP modified Fe3O4NPs feature high antibacterial activities, and can act as antibacterial agents with low cellular toxicology in the long-term storage of blood for future safe blood transfusion applications. More importantly, this novel method can be applied in the detection of bacteria from clinical patients who are infected with bacteria. In the validation analysis, 97.3% of the real blood samples (39 patients) could be classified effectively (only one patient infected with E. coli was misclassified). The multifunctional biosensor presented here allows for the simultaneous isolation, discrimination and killing of bacteria, suggesting its high potential for clinical diagnosis and safe blood transfusions.

Identification of constituents of the Alpine plant Rhinanthus glacialis by 13C nuclear magnetic resonance pattern recognition

Identification of constituents of the Alpine plant Rhinanthus glacialis by 13C nuclear magnetic resonance pattern recognition

Co-assembly of CdTe quantum dots and magnetic nanoparticles in imprinted matrices for magnetic separation and specific recognition of endocrine disrupting chemicals

Co-assembly of CdTe quantum dots and magnetic nanoparticles in imprinted matrices for magnetic separation and specific recognition of endocrine disrupting chemicals

Recognizing Check Magnetic Code Based on Peak-Valley Code and Distance

The check is a popular form for the non-cash payment and accounts for more than 50% of the non-cash transactions. Magnetic ink character recognition system can recognize the check magnetic code automatically and get the information of the bank and account. In magnetic ink character recognition system, the recognizing algorithm is mostly based on correlation coefficient. The computational cost of this algorithm is very high. This paper has proposed a new algorithm based on the peak-valley code and peak-valley distance after analyzing the characteristics of magnetic code signals in E-13B standards to simplify the calculations and system design. Firstly, the magnetic code signal is normalized and separated into magnetic character signals by the thresholds of peak and valley. Secondly, the features of the peak-valley code and peak-valley distance of each magnetic character signal are extracted, then the recognition based on peak-valley code and the nearest neighbor recognition algorithm based on peak-valley distance are utilized to recognize the magnetic code. The recognition results and statistical parameters from a large number of experiments show that the new method has high recognition rate, good robustness and low computational cost.

Grade classification of neuroepithelial tumors using high-resolution magic-angle spinning proton nuclear magnetic resonance spectroscopy and pattern recognition

Clinical data have shown that survival rates vary considerably among brain tumor patients, according to the type and grade of the tumor. Metabolite profiles of intact tumor tissues measured with high-resolution magic-angle spinning proton nuclear magnetic resonance spectroscopy (HRMAS (1)H NMRS) can provide important information on tumor biology and metabolism. These metabolic fingerprints can then be used for tumor classification and grading, with great potential value for tumor diagnosis. We studied the metabolic characteristics of 30 neuroepithelial tumor biopsies, including two astrocytomas (grade I), 12 astrocytomas (grade II), eight anaplastic astrocytomas (grade III), three glioblastomas (grade IV) and five medulloblastomas (grade IV) from 30 patients using HRMAS (1)H NMRS. The results were correlated with pathological features using multivariate data analysis, including principal component analysis (PCA). There were significant differences in the levels of N-acetyl-aspartate (NAA), creatine, myo-inositol, glycine and lactate between tumors of different grades (P<0.05). There were also significant differences in the ratios of NAA/creatine, lactate/creatine, myo-inositol/creatine, glycine/creatine, scyllo-inositol/creatine and alanine/creatine (P<0.05). A soft independent modeling of class analogy model produced a predictive accuracy of 87% for high-grade (grade III-IV) brain tumors with a sensitivity of 87% and a specificity of 93%. HRMAS (1)H NMR spectroscopy in conjunction with pattern recognition thus provides a potentially useful tool for the rapid and accurate classification of human brain tumor grades.

1H-Nuclear magnetic resonance pattern recognition studies with N-phenylanthranilic acid in the rat: time- and dose-related metabolic effects

N-Phenylanthranilic acid (NPAA) causes renal papillary necrosis (RPN) in the rat following repeated oral dosing. Non-invasive early detection of RPN is difficult, but a number of potential biomarkers have been investigated, including phospholipid and uronic acid excretion. This study used 1H-nuclear magnetic resonance (NMR) spectroscopic analysis of urine to investigate urinary metabolic perturbations occurring in the rat following exposure to NPAA. Male Alderley Park rats received NPAA (300, 500 or 700 mg kg−1 day−1 orally) for 7 days, and urine was collected on days 7–8, 14–15, 21–22 and 28–29. In a separate study, urine was collected on days 1–2, 3–4, 5–6 and 7–8 from rats receiving 500 mg kg−1 day−1. Samples were analysed by 1H NMR spectroscopy combined with multivariate data analysis and clinical chemistry. Histopathology and clinical chemistry analysis of terminal blood samples was carried out following termination on days 4, 6, 8 and 29 (4 week time course) and days 2, 4, 6 and 8 (8 day study). Urine analysis revealed a marked, though variable, excretion of β-hydroxybutyrate, acetoacetate and acetone (ketone bodies) seen on days 3–4, 5–6 and 7–8 of the study. It is postulated that the ketonuria might be secondary to an alteration in fatty acid metabolism due to inhibition of prostaglandin synthesis. In addition, an elevation in urinary ascorbate was observed during the first 8 days of the study. Ascorbate is considered to be a biomarker of hepatic response, probably reflecting an increased hepatic activity due to glucuronidation of NPAA.

IMAGE RECOGNITION BY INTEGRATION OF CONNECTIONIST AND SYMBOLIC APPROACHES

This paper presents a methodology for integrating connectionist and symbolic approaches to 2D image recognition. The proposed integration paradigm exploits the synergy of the two approaches for both the training and the recognition phases of an image recognition system. In the training phase, a symbolic module provides an approximate solution to a given image-recognition problem in terms of symbolic models. Such models are hierarchically organized into different abstraction levels, and include contextual descriptions. After mapping such models into a complex neural architecture, a neural training process is carried out to optimize the solution of the recognition problem. The so-obtained neural networks are used during the recognition phase for pattern classification. In this phase, the role of symbolic modules consists of managing complex aspects of information processing: abstraction levels, contextual information, and global recognition hypotheses. A hybrid system implementing the proposed integration paradigm is presented, and its advantages over single approaches are assessed. Results on Magnetic Resonance image recognition are reported, and comparisons with some well-known classifiers are made.

General Electric enters the computer business-revisited

Perhaps General Electric got into the "Computer Business" without tremendous foresight, but the first steps in that direction were immensely successful. Starting with the Bank of America's Electronic Recording Method of Accounting (ERMA) system, and combined with the development of Magnetic Ink Character Recognition (MICR) for the rapid processing of bank checks, and backed by one of the largest corporations in the world, GE had the opportunity to effectively chase and catch IBM in the field of data processing. Succeeding developments also portended well for the future but the continuing reluctance of the GE headquarters to support the Computer Department competitively with other companies whose one and only product was a computer eventually led to the sale of the operation to Honeywell Corporation. This is the story of those beginnings as seen and remembered by the first general manager of the Computer Department.

Esophageal Atresia, Tracheomalacia and Arterial Compression: Role of Aortopexy

Between 1985 and 1990, we treated 46 cases of esophageal atresia in the pediatric surgery department in Marseille. In 17 of these patients atresia was associated with tracheomalacia. The most common respiratory manifestations were acute apneic attacks, cyanotic spells and recurring pneumopathy. The underlying cause was arterial compression of the airways by the innominate artery in 6 cases, the aortic arch in 2 cases, and a common origin of the innominate and left carotid arteries in 2 cases. Eleven patients underwent surgery to relieve arterial compression: suspension of the aorta from the under surface of the sternum (10 cases) and reimplantation of the innominate artery (1 case). Results in terms of tracheal caliber and symptomatic relief were excellent in 10 cases including 1 case requiring redo, and poor in 1 case. For diagnosis, our experience shows the importance of endoscopy, nuclear magnetic resonance and recognition of gastroesophageal reflux which is often associated (9/11). The role of tracheomalacia is discussed. On the basis of our results and those previously reported, aortopexy appears to be an effective surgical technique in patients with esophageal atresia presenting respiratory complications due to arterial compression.

Grooved bar-code pattern recognition system with magnetoresistive sensor

A magnetic bar-code pattern recognition system with a magnetoresistive sensor is proposed. The bar-code consists of a set of grooves on an iron plate, similar to an optical bar-code pattern. When a magnet passes above the grooves on an iron plate, the magnetic field produced by the magnet is bent by the grooves. The bar-code pattern of grooves can be reconstructed by detecting the bend using the magnetoresistive sensor. Computer simulation results on magnetic flux density distribution near the grooves are presented, and prototype recognition systems with a magnetoresistive sensor are described. It is shown that a two-groove bar-code configuration with different groove depths depending on groove width and a thin-film magnetoresistive sensor construction are useful in realizing high-resolution detection systems. >

Fabrication of grouped magnetic heads

A new magnetic transducer has been developed for use in the measurement of mechanical displacement. Experiments suggest that the transducer could be used for various purposes: for instance, readout information from magnetic drums or disks of computers, nondestructive readout from thin-film memories, magnetic pattern recognition, and an unconventional flux sensor. The transducer is composed of flux-sensitive magnetic heads which are fabricated from a sheet of ferromagnetic thin film by photoetching process. By using the etching process, a large number of heads are produced simultaneously, and the heads are operated in a group. The characteristics, performances, and an application of grouped magnetic heads are described in this paper.