scholarly journals Single-Molecule Detection of DNA in a Nanochannel by High-Field Strength-Assisted Electrical Impedance Spectroscopy

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 189 ◽  
Author(s):  
Porpin Pungetmongkol ◽  
Takatoki Yamamoto
Keyword(s):  
Single Molecule ◽  
High Intensity ◽  
High Sensitivity ◽  
Electrical Impedance Spectroscopy ◽  
Random Coil ◽  
Label Free ◽  
Electrode Gap ◽  
Label Free Detection ◽  
Intensity Field ◽  
Nanogap Electrodes

Many researchers have fabricated micro and nanofluidic devices incorporating optical, chemical, and electrical detection systems with the aim of achieving on-chip analysis of macromolecules. The present study demonstrates a label-free detection of DNA using a nanofluidic device based on impedance measurements that is both sensitive and simple to operate. Using this device, the electrophoresis and dielectrophoresis effect on DNA conformation and the length dependence were examined. A low alternating voltage was applied to the nanogap electrodes to generate a high intensity field (>0.5 MV/m) under non-faradaic conditions. In addition, a 100 nm thick gold electrode was completely embedded in the substrate to allow direct measurements of a solution containing the sample passing through the gap, without any surface modification required. The high intensity field in this device produced a dielectrophoretic force that stretched the DNA molecule across the electrode gap at a specific frequency, based on back and forth movements between the electrodes with the DNA in a random coil conformation. The characteristics of 100 bp, 500 bp, 1 kbp, 5 kbp, 10 kbp, and 48 kbp λ DNA associated with various conformations were quantitatively analyzed with high resolution (on the femtomolar level). The sensitivity of this system was found to be more than about 10 orders of magnitude higher than that obtained from conventional linear alternating current (AC) impedance for the analysis of bio-polymers. This new high-sensitivity process is expected to be advantageous with regard to the study of complex macromolecules and nanoparticles.

scholarly journals Biological Nanopores: Engineering on Demand

Life ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 27
Author(s):  
Ana Crnković ◽  
Marija Srnko ◽  
Gregor Anderluh
Keyword(s):  
Molecular Biology ◽  
Single Molecule ◽  
Enzymatic Reactions ◽  
Label Free ◽  
Natural Sources ◽  
On Demand ◽  
Label Free Detection ◽  
Long Read ◽  
Inorganic Molecules ◽  
Standard Molecular Biology

Nanopore-based sensing is a powerful technique for the detection of diverse organic and inorganic molecules, long-read sequencing of nucleic acids, and single-molecule analyses of enzymatic reactions. Selected from natural sources, protein-based nanopores enable rapid, label-free detection of analytes. Furthermore, these proteins are easy to produce, form pores with defined sizes, and can be easily manipulated with standard molecular biology techniques. The range of possible analytes can be extended by using externally added adapter molecules. Here, we provide an overview of current nanopore applications with a focus on engineering strategies and solutions.

scholarly journals An Aptamer-Based Capacitive Sensing Platform for Specific Detection of Lung Carcinoma Cells in the Microfluidic Chip

Biosensors ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 98 ◽  
Author(s):  
Ngoc-Viet Nguyen ◽  
Chun-Hao Yang ◽  
Chung-Jung Liu ◽  
Chao-Hung Kuo ◽  
Deng-Chyang Wu ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Lung Carcinoma ◽  
Early Stage ◽  
A549 Cells ◽  
Microfluidic Channel ◽  
Electrical Impedance Spectroscopy ◽  
Label Free ◽  
Early Stage Lung Cancer ◽  
Sensing Platform ◽  
Label Free Detection

Improvement of methods for reliable and early diagnosis of the cellular diseases is necessary. A biological selectivity probe, such as an aptamer, is one of the candidate recognition layers that can be used to detect important biomolecules. Lung cancer is currently a typical cause of cancer-related deaths. In this work, an electrical sensing platform is built based on amine-terminated aptamer modified-gold electrodes for the specific, label-free detection of a human lung carcinoma cell line (A549). The microdevice, that includes a coplanar electrodes configuration and a simple microfluidic channel on a glass substrate, is fabricated using standard photolithography and cast molding techniques. A procedure of self-assembly onto the gold surface is proposed. Optical microscope observations and electrical impedance spectroscopy measurements confirm that the fabricated microchip can specifically and effectively identify A549 cells. In the experiments, the capacitance element that is dominant in the change of the impedance is calculated at the appropriate frequency for evaluation of the sensitivity of the biosensor. Therefore, a simple, inexpensive, biocompatible, and selective biosensor that has the potential to detect early-stage lung cancer would be developed.

Photonic crystals: A platform for label-free and enhanced fluorescence biomolecular and cellular assays

2008 ◽  
Vol 1133 ◽  
Author(s):  
Brian T. Cunningham ◽  
Leo Chan ◽  
Patrick C. Mathias ◽  
Nikhil Ganesh ◽  
Sherine George ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
High Throughput Screening ◽  
High Sensitivity ◽  
Excitation Wavelength ◽  
Label Free ◽  
Crystal Surfaces ◽  
Enhanced Fluorescence ◽  
Preferred Direction ◽  
Label Free Detection

Abstract Photonic crystal surfaces represent a class of resonant optical structures that are capable of supporting high intensity electromagnetic standing waves with near-field and far-field properties that can be exploited for high sensitivity detection of biomolecules and cells. While modulation of the resonant wavelength of a photonic crystal by the dielectric permittivity of adsorbed biomaterials enables label-free detection, the resonance can also be tuned to coincide with the excitation wavelength of common fluorescent tags - including organic molecules and semiconductor quantum dots. Photonic crystals are also capable of efficiently channeling fluorescent emission into a preferred direction for enhanced extraction efficiency. Photonic crystals can be designed to support multiple resonant modes that can perform label free detection, enhanced fluorescence excitation, and enhanced fluorescence extraction simultaneously on the same device. Because photonic crystal surfaces may be inexpensively produced over large surface areas by nanoreplica molding processes, they can be incorporated into disposable labware for applications such as pharmaceutical high throughput screening. In this talk, the optical properties of surface photonic crystals will be reviewed and several applications will be described, including results from screening a 200,000-member chemical compound library for inhibitors of protein-DNA interactions, gene expression microarrays, and high sensitivity of protein biomarkers.

scholarly journals Rapid label-free SERS detection of foodborne pathogenic bacteria based on hafnium ditelluride-Au nanocomposites

2020 ◽  
Vol 13 (05) ◽  
pp. 2041004 ◽  
Author(s):  
Yang Li ◽  
Yanxian Guo ◽  
Binggang Ye ◽  
Zhengfei Zhuang ◽  
Peilin Lan ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Limit Of Detection ◽  
Principal Component ◽  
High Sensitivity ◽  
Chemical Mechanism ◽  
Sers Substrate ◽  
Label Free ◽  
Label Free Detection ◽  
Surface Enhanced Raman ◽  
Foodborne Pathogenic Bacteria

Two-dimensional (2D) nanomaterials have captured an increasing attention in biophotonics owing to their excellent optical features. Herein, 2D hafnium ditelluride (HfTe[Formula: see text], a new member of transition metal tellurides, is exploited to support gold nanoparticles fabricating HfTe2-Au nanocomposites. The nanohybrids can serve as novel 2D surface-enhanced Raman scattering (SERS) substrate for the label-free detection of analyte with high sensitivity and reproducibility. Chemical mechanism originated from HfTe2 nanosheets and the electromagnetic enhancement induced by the hot spots on the nanohybrids may largely contribute to the superior SERS effect of HfTe2-Au nanocomposites. Finally, HfTe2-Au nanocomposites are utilized for the label-free SERS analysis of foodborne pathogenic bacteria, which realize the rapid and ultrasensitive Raman test of Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Salmonella with the limit of detection of 10 CFU/mL and the maximum Raman enhancement factor up to [Formula: see text]. Combined with principal component analysis, HfTe2-Au-based SERS analysis also completes the bacterial classification without extra treatment.

scholarly journals The Localized Enhancement of Surface Plasmon Standing Waves Interacting With Single Nanoparticles

2021 ◽  
Author(s):  
hongyao liu ◽  
Xuqing Sun ◽  
Xue Wang ◽  
Fei Wang ◽  
Chang Wang ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
Electric Dipole ◽  
Surrounding Medium ◽  
Standing Waves ◽  
High Sensitivity ◽  
Detection Sensitivity ◽  
Label Free ◽  
Vertical Electric Dipole ◽  
Lower Dielectric Constant ◽  
Label Free Detection

Abstract Real-time, high-sensitivity, and label-free detection to single nanoparticles has been achieved via visualizing the interaction between surface plasmon polaritons (SPPs) and nanoparticles, which is widely applied to chemistry and biology. In this work, aiming to enhance the detection sensitivity to nanoparticles, we explore the interaction of SPP standing waves with single nanoparticles. Compared with SPPs, the inhomogeneous fields of SPP standing waves modulate charge distributions around the particle and excite different electric dipole modes that tailor localized enhancements. For nanoparticles situating at electric antinodes of SPP standing waves, a vertical electric dipole is excited and high-density charges are stimulated around nanoparticle-film nanocavities, leading to further increased localized enhancement. The localized enhancement experiences more increase with smaller particle size, lower dielectric constant of surrounding medium, and lower particle refractive index. Via tailoring the localized enhancement by SPP standing waves, the sensitivity of SPP microscopy can be improved, which would broaden its applications on nanotechnology, biomedicine, and environmental monitoring.

scholarly journals Evaluation of Three Peptide Immobilization Techniques on a QCM Surface Related to Acetaldehyde Responses in the Gas Phase

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3942 ◽  
Author(s):  
Tomasz Wasilewski ◽  
Bartosz Szulczyński ◽  
Wojciech Kamysz ◽  
Jacek Gębicki ◽  
Jacek Namieśnik
Keyword(s):  
Spin Coating ◽  
Olfactory Receptors ◽  
High Sensitivity ◽  
Dip Coating ◽  
Label Free ◽  
Optimal Method ◽  
Spin Coating Method ◽  
Whole Cells ◽  
Label Free Detection ◽  
Coating Method

The quartz-crystal microbalance is a sensitive and universal tool for measuring concentrations of various gases in the air. Biochemical functionalization of the QCM electrode allows a label-free detection of specific molecular interactions with high sensitivity and specificity. In addition, it enables a real-time determination of its kinetic rates and affinity constants. This makes QCM a versatile bioanalytical screening tool for various applications, with surface modifications ranging from the detection of single molecular monolayers to whole cells. Various types of biomaterials, including peptides mapping the binding sites of olfactory receptors, can be deposited as a sensitive element on the surface of the electrodes. One of key ways to ensure the sensitivity and accuracy of the sensor is provided by application of an optimal and repeatable method of immobilization. Therefore, effective sensors operation requires development of an optimal method of deposition. This paper reviews popular techniques (drop-casting, spin-coating, dip-coating) for coating peptides on piezoelectric crystals surface. Peptide (LEKKKKDC-NH2) derived from an aldehyde binding site in the HarmOBP7 protein was synthesized and used as a sensing material for the biosensor. The degree of deposition of the sensitive layer was monitoring by variations in the sensors frequency. The highest mass threshold for QCM measurements for peptides was approximately 16.43 µg·mm−2 for spin coating method. Developed sensor exhibited repeatable response to acetaldehyde. Moreover, responses to toluene was observed to evaluate sensors specificity. Calibration curves of the three sensors showed good determination coefficients (R2 > 0.99) for drop casting and dip coating and 0.97 for the spin-coating method. Sensors sensitivity vs. acetaldehyde were significantly higher for the dip-coating and drop-casting methods and lower for spin-coating one.

Bifunctional Nanoparticles as a Recyclable Fluorescent Sensor for pH and Cu2+ Detection and Removal of Heavy Metal Ions

NANO ◽  
2020 ◽  
Vol 15 (04) ◽  
pp. 2050048
Author(s):  
Yong Qian ◽  
Xiangfu Meng ◽  
Hongji Liu ◽  
Xingyu Wang ◽  
Hui Wang
Keyword(s):  
Aqueous Solution ◽  
Heavy Metal Ions ◽  
High Efficiency ◽  
Fluorescent Sensor ◽  
High Sensitivity ◽  
Label Free ◽  
Practical Applications ◽  
Surrounding Environment ◽  
Label Free Detection ◽  
Recyclable Adsorbent

Magnetic and fluorescent-based sensors have demonstrated widely applications due to their easily recycle and quickly optical response. However, the complex synthesis and weaker function of these sensors limit their practical applications. Herein, an unmodified, magnetic-functionalized carbon dots-based fluorescent sensor has been developed for label-free detection of pH and Cu[Formula: see text] with high sensitivity. The sensors can not only reversibly quench and recover the fluorescence signals in response to the variation of surrounding environment including pH and Cu[Formula: see text], but also be used as a high-efficiency recyclable adsorbent for removing Cu[Formula: see text], Hg[Formula: see text], Cr[Formula: see text] and Pb[Formula: see text] from aqueous solution.

scholarly journals An Overview of High Frequency Acoustic Sensors—QCMs, SAWs and FBARs—Chemical and Biochemical Applications

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4395 ◽  
Author(s):  
Adnan Mujahid ◽  
Adeel Afzal ◽  
Franz L. Dickert
Keyword(s):  
High Frequency ◽  
Piezoelectric Materials ◽  
Fundamental Property ◽  
High Sensitivity ◽  
Enzyme Linked Immunosorbent Assay ◽  
Label Free ◽  
Detection Mechanism ◽  
Acoustic Transducers ◽  
Resonance Frequencies ◽  
Label Free Detection

Acoustic devices have found wide applications in chemical and biosensing fields owing to their high sensitivity, ruggedness, miniaturized design and integration ability with on-field electronic systems. One of the potential advantages of using these devices are their label-free detection mechanism since mass is the fundamental property of any target analyte which is monitored by these devices. Herein, we provide a concise overview of high frequency acoustic transducers such as quartz crystal microbalance (QCM), surface acoustic wave (SAW) and film bulk acoustic resonators (FBARs) to compare their working principles, resonance frequencies, selection of piezoelectric materials for their fabrication, temperature-frequency dependency and operation in the liquid phase. The selected sensor applications of these high frequency acoustic transducers are discussed primarily focusing on the two main sensing domains, i.e., biosensing for working in liquids and gas/vapor phase sensing. Furthermore, the sensor performance of high frequency acoustic transducers in selected cases is compared with well-established analytical tools such as liquid chromatography mass spectrometry (LC-MS), gas chromatographic (GC) analysis and enzyme-linked immunosorbent assay (ELISA) methods. Finally, a general comparison of these acoustic devices is conducted to discuss their strengths, limitations, and commercial adaptability thus, to select the most suitable transducer for a particular chemical/biochemical sensing domain.

scholarly journals Optical Biosensors for Label-Free Detection of Small Molecules

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4126 ◽  
Author(s):  
Riikka Peltomaa ◽  
Bettina Glahn-Martínez ◽  
Elena Benito-Peña ◽  
María Moreno-Bondi
Keyword(s):  
Small Molecules ◽  
High Sensitivity ◽  
Surface Enhanced Raman Spectroscopy ◽  
Optical Biosensors ◽  
Label Free ◽  
Fiber Sensors ◽  
Label Free Detection ◽  
Surface Enhanced Raman ◽  
Resonance Surface ◽  
Small Molecule Detection

Label-free optical biosensors are an intriguing option for the analyses of many analytes, as they offer several advantages such as high sensitivity, direct and real-time measurement in addition to multiplexing capabilities. However, development of label-free optical biosensors for small molecules can be challenging as most of them are not naturally chromogenic or fluorescent, and in some cases, the sensor response is related to the size of the analyte. To overcome some of the limitations associated with the analysis of biologically, pharmacologically, or environmentally relevant compounds of low molecular weight, recent advances in the field have improved the detection of these analytes using outstanding methodology, instrumentation, recognition elements, or immobilization strategies. In this review, we aim to introduce some of the latest developments in the field of label-free optical biosensors with the focus on applications with novel innovations to overcome the challenges related to small molecule detection. Optical label-free methods with different transduction schemes, including evanescent wave and optical fiber sensors, surface plasmon resonance, surface-enhanced Raman spectroscopy, and interferometry, using various biorecognition elements, such as antibodies, aptamers, enzymes, and bioinspired molecularly imprinted polymers, are reviewed.

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