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ACS Applied Materials & Interfaces Mar 2017Accurate and precise determination of mechanical properties of nanoscale materials is mandatory since device performances of nanoelectromechanical systems (NEMS) are...
Accurate and precise determination of mechanical properties of nanoscale materials is mandatory since device performances of nanoelectromechanical systems (NEMS) are closely related to the flexural properties of the materials. In this study, the intrinsic mechanical properties of highly stressed silicon nitride (SiN) beams of varying lengths are investigated using two different techniques: Dynamic flexural measurement using optical interferometry and quasi-static flexural measurement using atomic force microscopy. The resonance frequencies of the doubly clamped, highly stressed beams are found to be inversely proportional to their length, which is not usually observed from a beam but is expected from a string-like structure. The mass density of the SiN beams can be precisely determined from the dynamic flexural measurements by using the values for internal stress and Young's modulus determined from the quasi-static measurements. As a result, the mass resolution of the SiN beam resonators was predicted to be a few attograms, which was found to be in excellent agreement with the experimental results. This work suggests that accurate and precise determination of mechanical properties can be achieved through combined flexural measurement techniques, which is a crucial key for designing practical NEMS applications such as biomolecular sensors and gas detectors.
PubMed: 28156098
DOI: 10.1021/acsami.6b16278 -
Journal of Pharmaceutical and... Feb 2017A sensitive, selective and precise liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of propofol (PRO) in rat serum and hair has been...
A sensitive, selective and precise liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of propofol (PRO) in rat serum and hair has been developed. 3-Bromomethyl-propyphenazone was used as derivatization reagent forming propofol-methyl-propyphenazone compound. The derivatization reaction was optimized and validated for maximum MS sensitivity. The MS instrumental sensitivity reached to 10 attogram. The serum samples were extracted by using Chromabond C columns, while hair samples extracted with methanol. The tendency of volatility of PRO was minimized by adding triethylamine to the extract before the use of nitrogen gas for evaporation of solvent. The limit of quantitation (LLOQ) was 0.01pg/mL and the assay was linear to 10000pg/mL. The intra-and inter-day precision (RSD%) ranged from 0.33 to 3.44% while the accuracy (E%, relative error) were -6.4 to 1.1%. The ionization suppression, due to reagent, was minimized by reacting the excess reagent with methanol, and eluting to waste before MS ionization source (2-4.5min). The method was successfully applied for detection and determination of PRO in rat serum and hair after 7-28days from administration of only one dose of propofol (10mg/kg).
Topics: Animals; Antipyrine; Chromatography, Liquid; Hair; Hypnotics and Sedatives; Male; Propofol; Rats; Rats, Wistar; Tandem Mass Spectrometry
PubMed: 27915197
DOI: 10.1016/j.jpba.2016.11.051 -
Scientific Reports Nov 2016We have designed a versatile and sensitive liquid chromatographic (LC) system, featuring a monolithic trap column and a very narrow (10 μm ID) fused silica open...
We have designed a versatile and sensitive liquid chromatographic (LC) system, featuring a monolithic trap column and a very narrow (10 μm ID) fused silica open tubular liquid chromatography (OTLC) separation column functionalized with C-groups, for separating a wide range of molecules (from small metabolites to intact proteins). Compared to today's capillary/nanoLC approaches, our system provides significantly enhanced sensitivity (up to several orders) with matching or improved separation efficiency, and highly repeatable chromatographic performance. The chemical properties of the trap column and the analytical column were fine-tuned to obtain practical sample loading capacities (above 2 μg), an earlier bottleneck of OTLC. Using the OTLC system (combined with Orbitrap mass spectrometry), we could perform targeted metabolomics of sub-μg amounts of exosomes with 25 attogram detection limit of a breast cancer-related hydroxylated cholesterol. With the same set-up, sensitive bottom-up proteomics (targeted and untargeted) was possible, and high-resolving intact protein analysis. In contrast to state-of-the-art packed columns, our platform performs chromatography with very little dilution and is "fit-for-all", well suited for comprehensive analysis of limited samples, and has potential as a tool for challenges in diagnostics.
Topics: Animals; Axin Protein; Breast Neoplasms; Chromatography, Liquid; Exosomes; Female; Humans; Hydroxycholesterols; Mice; Peptides; Proteomics; Reproducibility of Results; Sensitivity and Specificity; Tandem Mass Spectrometry
PubMed: 27897190
DOI: 10.1038/srep37507 -
Analytical Chemistry Mar 2016Ultralow level analysis of actinides in urine samples may be required for dose assessment in the event of internal exposures to these radionuclides at nuclear facilities...
Ultralow level analysis of actinides in urine samples may be required for dose assessment in the event of internal exposures to these radionuclides at nuclear facilities and nuclear power plants. A new bioassay method for analysis of sub-femtogram levels of Am and Cm in large-volume urine samples was developed. Americium and curium were co-precipitated with hydrous titanium oxide from the urine matrix and purified by column chromatography separation. After target preparation using mixed titanium/iron oxides, the final sample was measured by compact accelerator mass spectrometry. Urine samples spiked with known quantities of Am and Cm isotopes in the range of attogram to femtogram levels were measured for method evaluation. The results are in good agreement with the expected values, demonstrating the feasibility of compact accelerator mass spectrometry (AMS) for the determination of minor actinides at the levels of attogram/liter in urine samples to meet stringent sensitivity requirements for internal dosimetry assessment.
Topics: Americium; Curium; Isotopes; Limit of Detection; Mass Spectrometry
PubMed: 26822907
DOI: 10.1021/acs.analchem.5b04546 -
Biosensors & Bioelectronics Jun 2016Rapid, ultrasensitive diagnostic/triaging kits for early detection of malarial parasites are critical for prevention of malarial epidemic, especially in developing and...
A highly sensitive self assembled monolayer modified copper doped zinc oxide nanofiber interface for detection of Plasmodium falciparum histidine-rich protein-2: Targeted towards rapid, early diagnosis of malaria.
Rapid, ultrasensitive diagnostic/triaging kits for early detection of malarial parasites are critical for prevention of malarial epidemic, especially in developing and tropical countries. Unlike traditional microscopic diagnosis, these kits rely on the detection of antigens specific to malarial parasites. One such antigen which is routinely used in these diagnostic kits is Histidine-rich protein-2; a protein synthesized and released into the blood stream by the parasite Plasmodium falciparum. In this paper, we demonstrate an ultrasensitive nanobiosensor detection platform for Histidine-rich protein-2 having a limit of detection of attogram/ml. This nanobiosensor platform comprises of Mercaptopropylphosphonic acid functionalized copper doped zinc oxide nanofibers synthesized by electrospinning technique. Ultrasensitivity of attogram/ml can be attributed to the complimentary effects of Mercaptopropylphosphonic acid and copper doping in zinc oxide. Mercaptopropylphosphonic acid enhances the functional groups required for immobilizing antibody. Copper doping in zinc oxide not only increases the conductivity of the nanofibers but also pre-concentrates the target analyte onto the Mercaptopropylphosphonic acid treated nanofiber surface due to inherent electric field generated at the copper/zinc oxide heterojunction interface. The impedimetric detection response of copper-doped zinc oxide nanofiber modified electrode shows excellent sensitivity (28.5 kΩ/(gm/ml)/cm(2)) in the detection ranges of 10 ag/ml-10 µg/ml, and a detection limit of 6 attogram/ml. In addition, the proposed biosensor is highly selective to targeted HRP2 protein with a relative standard deviation of 1.9% in the presence of various interference of nonspecific molecules. To the best of our knowledge, this biosensor shows the lowest detection limit of malarial parasites reported in the literature spanning different nanomaterials and different detection mechanisms. Since the nanobiosensor platform is based on immunoassay technique, with a little modification, it can be extended for developing point-of-care diagnostic devices for several biomarkers of importance.
Topics: Antigens, Protozoan; Biosensing Techniques; Copper; Early Diagnosis; Humans; Malaria, Falciparum; Nanofibers; Plasmodium falciparum; Protozoan Proteins; Zinc Oxide
PubMed: 26803412
DOI: 10.1016/j.bios.2016.01.036 -
Light, Science & Applications Jan 2016High-throughput small-molecule assays play essential roles in biomedical diagnosis, drug discovery, environmental analysis, and physiological function research....
High-throughput small-molecule assays play essential roles in biomedical diagnosis, drug discovery, environmental analysis, and physiological function research. Nanoplasmonics holds a great potential for the label-free detection of small molecules at extremely low concentrations. Here, we report the development of nanoplasmonic paper (NP-paper) for the rapid separation and ultrasensitive detection of mixed small molecules. NP-paper employs nanogap-rich silver nanoislands on cellulose fibers, which were simply fabricated at the wafer level by using low-temperature solid-state dewetting of a thin silver film. The nanoplasmonic detection allows for the scalable quantification and identification of small molecules over broad concentration ranges. Moreover, the combination of chromatographic separation and nanoplasmonic detection allows both the highly sensitive fluorescence detection of mixed small molecules at the attogram level and the label-free detection at the sub-nanogram level based on surface-enhanced Raman scattering. This novel material provides a new diagnostic platform for the high-throughput, low-cost, and label-free screening of mixed small molecules as an alternative to conventional paper chromatography.
PubMed: 30167113
DOI: 10.1038/lsa.2016.9 -
Analytica Chimica Acta Jan 2016
PubMed: 28751005
DOI: 10.1016/j.aca.2015.11.005 -
Biosensors & Bioelectronics Mar 2016In this work, an ultrasensitive immobilization-free photoelectrochemical (PEC) biosensor was successfully developed for the first time based on a novel enzyme-free...
A versatile immobilization-free photoelectrochemical biosensor for ultrasensitive detection of cancer biomarker based on enzyme-free cascaded quadratic amplification strategy.
In this work, an ultrasensitive immobilization-free photoelectrochemical (PEC) biosensor was successfully developed for the first time based on a novel enzyme-free cascaded quadratic signal amplification strategy. This rationally designed homogeneous dual amplification strategy consists of a target-analog recycling circuit based on catalytic hairpin assembly (CHA) and a hybridization chain reaction (HCR) mediated amplification circuit. In the presence of carcinoembryonic antigen (CEA), a proof-of-concept target, target-analog is released to trigger the upstream CHA recycling circuit. The generated dsDNA complexes from CHA recycling could further induce the downstream HCR amplification, leading to the formation of numerous hemin/G-quadruplex DNAzymes. This would accordingly stimulate the biocatalytic precipitation of 4-chloro-1-naphthol, inducing a distinct decrease in the photocurrent signal due to the formed insoluble/insulating products on electrode surface. Under the optimal conditions, this PEC biosensor achieved ultrasensitive detection of CEA down to the atto-gram level. The introduction of this aptamer-based cascaded quadratic amplification strategy not only remarkably improves the selectivity and sensitivity of CEA assay, but also allows the ultrasensitive detection of other proteins by designing specific aptamers, providing a universal, isothermal and label-free PEC biosensing platform for ultrasensitive detection of different kinds of cancer biomarkers and holding a great potential for early-diagnosis of cancer.
Topics: Biomarkers, Tumor; Carcinoembryonic Antigen; Conductometry; DNA; Enzymes; Equipment Design; Equipment Failure Analysis; Humans; Nucleic Acid Amplification Techniques; Photometry; Reproducibility of Results; Sensitivity and Specificity
PubMed: 26409022
DOI: 10.1016/j.bios.2015.09.041 -
Nano Letters Sep 2015Operation of nanomechanical devices in liquid has been challenging due to the strong viscous damping that greatly impedes the mechanical motion. Here we demonstrate an...
Operation of nanomechanical devices in liquid has been challenging due to the strong viscous damping that greatly impedes the mechanical motion. Here we demonstrate an optomechanical microwheel resonator integrated in microfluidic system that supports low-loss optical resonances at near-visible wavelength with quality factor up to 1.5 million, which allows the observation of the thermal Brownian motion of the mechanical mode in both air and water environment with high signal-to-background ratio. A numerical model is developed to calculate the hydrodynamic effect on the device due to the surrounding water, which agrees well with the experimental results. With its very high resonance frequency (170 MHz) and small loaded mass (75 pg), the present device has an estimated mass sensitivity at the attogram level in water.
PubMed: 26226184
DOI: 10.1021/acs.nanolett.5b02388 -
Small (Weinheim An Der Bergstrasse,... Oct 2015A carbon-nanotube-enabling scanning probe technique/nanotechnology for manipulating and measuring lithium at the nano/mesoscale is introduced. Scanning Li-nanopipette...
A carbon-nanotube-enabling scanning probe technique/nanotechnology for manipulating and measuring lithium at the nano/mesoscale is introduced. Scanning Li-nanopipette and probe microscopy (SLi-NPM) is based on a conductive atomic force microscope (AFM) cantilever with an open-ended multi-walled carbon nanotube (MWCNT) affixed to its apex. SLi-NPM operation is demonstrated with a model system consisting of a Li thin film on a Si(111) substrate. By control of bias, separation distance, and contact time, attograms of Li can be controllably pipetted to or from the MWCNT tip. Patterned surface Li features are then directly probed via noncontact AFM measurements with the MWCNT tip. The subsequent decay of Li features is simulated with a mesoscale continuum model, developed here. The Li surface diffusion coefficient for a four (two) Li layer thick film is measured as D=8(±1.2)×10(-15) cm(2) s(-1) (D=1.75(±0.15)×10(-15) cm(2) s(-1)). Dual-Li pipetting/measuring with SLi-NPM enables a broad range of time-dependent Li and nanoelectrode characterization studies of fundamental importance to energy-storage research.
PubMed: 26182911
DOI: 10.1002/smll.201500999