Olfactory receptor-based polypeptide sensor for acetic acid VOC detection

Rapid detection of food-borne pathogens in packaged food products can prevent the spread of infectious diseases. This study investigates the application of novel sensing material that is sensitive to specific indicator volatile organic compound (VOC) related to Salmonella contamination in packaged meat. Specifically, the objective was to develop an olfactory receptor-based synthetic polypeptide sensor for the detecting acetic acid in low concentrations and at room temperature. Synthetic polypeptide was deposited on a quartz crystal microbalance (QCM) electrode and was evaluated for detecting acetic acid at 10–100 ppm. Developed sensor exhibited repeatable response to a particular concentration of acetic acid and displayed reproducibility among multiple sensors during acetic acid detection. Mean estimated lower detection limits of these sensors were about 1–3 ppm and linear calibration models showed linear relationships. Thus, the QCM sensors exhibited a great potential for detecting low concentrations of acetic acid at room temperature and can be used in the sensor array for packaged meat spoilage and contamination detection.     

Disposable receptor-based optical sensor for nitrate

A new optical absorption-based disposable sensor for nitrate is described. The nitrate-sensitive element is a bicyclic cyclophane receptor next to a suitable pH-sensitive lipophilic dye immobilized in a plasticized polymeric membrane. The rigid amide-based receptor with C3 symmetry controls the anion selectivity pattern of the optical element. The optical selectivity coefficients obtained for nitrate over a variety of naturally occurring anions in natural waters meet the requirements for the determination of nitrate in waters. The disposable sensor responds to nitrate rapidly-the typical response time is 5 min-and reversibly over a wide dynamic range (26 microM-63 mM) with sensor-to-sensor reproducibility (relative standard deviation, RSD, 3.68%, as log aNO3-, at the medium level of the range and RSD 1.39% for repeated measurements with the same sensor). The performance of the optical disposable sensor was tested for the analysis of nitrate in different types of natural waters (river, well, spring), validating results against a reference procedure. The proposed method is quick, inexpensive, selective, and sensitive and uses only conventional instrumentation.     

Solid-phase receptor-based assay for the detection of cyclic imines by chemiluminescence, fluorescence, or colorimetry

The spirolides and gymnodimines are marine phycotoxins included in the group of cyclic imines. The toxicity of these compounds to humans is still unknown, although their toxicity by intraperitoneal injection in rodents is very high. A receptor-based method was developed using the competition of the 13-desmethyl spirolide C with biotin-labeled α-bungarotoxin for binding to nicotinic acetylcholine receptors and the immobilization of the α-bungarotoxin-receptor complex on streptavidin-coated surfaces. The quantification of the immobilized receptor can be achieved using a specific antibody. Finally, after the addition of a secondary antibody labeled with horseradish peroxidase, three alternative substrates of this enzyme generate a chemiluminescent, fluorescent, or colorimetric signal. The assay performs well in shellfish extracts and the detection range is 5-150 nM of 13-desmethyl spirolide C in shellfish extracts, which is at least 5 times more sensitive than the existing fluorescence polarization assay. This assay can also detect gymnodimine, although with 10 times lower sensitivity than the spirolide. The detection of cyclic imines with microplate assays would be useful for screening purposes in order to reduce the number of samples to be processed by bioassays or analytical methods.     

A domain-extension method for quantitative detection of cavities by infrared scanning

A domain-extension method for quantitative detection of irregular-shape cavities inside irregular-shape bodies is presented. An auxiliary problem is introduced in the solution of the cavities. In the auxiliary problem, the original body domain at the cavity side is extended so that the original cavity walls become interior points. The position of the cavities can then be found by solving the temperature field in the extended domain and matching the temperatures and heat fluxes at the interior points to the conditions imposed on the cavities. A boundary-element method is used for the solution of the auxiliary problem, and by means of four examples, the accuracy of the domain extension method is established. The paper provides the details for the numerical solution of the cavities. Limitation of the method in the detection of multiple cavities is also explored. The domain-extension method has shown to be highly effective in quantitative detection of cavities in single-cavity bodies.     

MOR定量测定系统的设计

本文介绍了免疫层析法MOR定量测定系统的硬件方案及其信号分析,该测定系统具有简单、快速及稳定性好的优点,可应用于毒品的认定,戒毒治疗过程的监测等禁毒戒毒工作场合。     

A quantitative acoustic microscope with multiple detection modes

An acoustic microscope that permits operation with both toneburst and impulse excitation of the lens is presented. Either mode can be selected and combined with mechanical scanning in any direction. In the impulse-excited mode, the specular and Rayleigh signals from the sample are resolved in time, and analysis is performed to obtain surface wave propagation parameters. The power of the simultaneous application of these techniques is illustrated by measurements on specimens of intact and fractured glass and duraluminum. Reflection and transmission coefficients for a crack are measured, and conclusions are drawn about V(z) processing. These results are significant because the images of cracks produced by the conventional toneburst scanning acoustic microphone (SAM) tend to be complex. Diffraction from the tips of cracks is observed in the microscope.     

A sensitive and quantitative element-tagged immunoassay with ICPMS detection

We report a set of novel immunoassays in which proteins of interest can be detected using specific element-tagged antibodies. These immunoassays are directly coupled with an inductively coupled plasma mass spectrometer (ICPMS) to quantify the elemental (in this work, metal) component of the reacted tagged antibodies. It is demonstrated that these methods can detect levels of target proteins as low as 0.1-0.5 ng/mL and yield a linear response to protein concentration over 3 orders of magnitude.     

Xerogel optical sensor films for quantitative detection of nitroxyl

Xerogel sensing films were synthesized via sol-gel chemistry were used to fabricate optical nitroxyl (HNO) sensors [corrected] Selective detection of HNO in solution was achieved by monitoring the rates of manganese(III) meso-tetrakis(4-sulfonatophenyl) porphyrinate (MnIIITPPS) reductive nitrosylation in the anaerobic interior of aminoalkoxysilane-derived xerogel films. Nitroxyl permeability in sensor films deposited in round-bottom 96-well plates was enhanced via incorporation of trimethoxysilyl-terminated poly(amidoamine-organosilicon) dendrimers in the xerogel network. The selectivity of MnIIITPPS for HNO, the overall sensitivity, and the working dynamic range of the resulting sensors were characterized. The HNO-sensing microtiter plates were used to quantify pH-dependent HNO generation by the recently described HNO-donor sodium 1-(isopropylamino)diazene-1-ium-1,2-diolate (IPA/NO), and compare HNO production efficiency between IPA/NO and Angeli's salt, a traditional HNO-donor.     

A simple and novel method for the quantitative detection of 5-hydroxymethylcytosine using carbon nanotube field-effect transistors

5-hydroxymethylcytosine (5-hmC) is an important epigenetic derivative of cytosine and quantitative detection of 5-hmC could be used as a reliable biomarker for a variety of human diseases. Current technologies used in 5-hmC detection are complicated and time/cost inefficient. In this work, we report the first application of antibody-functionalized carbon nanotube field-effect transistors (CNT-FETs) in quantitative detection of 5-hmC from mouse tissues. This method achieves facile and ultra-sensitive 5-hmC detection based on electrical performance device and avoids complicated processing for DNA samples. The 5-hmC content percentages of normal mouse cerebrum, cerebellum, spleen, lung, liver, and heart samples presented in the genomic DNA were measured as 0.653, 0.573, 0.002, 0.020, 0.076, and 0.009, respectively, which is consistent with previous reports. This technology could be developed into facile routine 5-hmC monitoring devices for clinic human disease diagnoses.

Open image in new window

     

SERS-encoded nanocomposites for dual pathogen bioassay

Surface-enhanced Raman spectroscopy(SERS) has been successfully applied to detect various biomolecules, but it is still in challenge to assay living cells or bacteria sensitively, selectively and quantitatively in complex environments. In this paper, 4-ATP and DTNB are assembled on Ag nanoparticle(NP)-decorated poly(styrene-co-acrylic acid)(PSA) nanospheres and then sealed by silica shells to form sensitive SERS labels based on the localized surface plasmon resonance of Ag NPs and large light scattering cross-sections of PSA nanospheres. They are further developed as encoding tags for dual detection of S. aureus and E. coli after assembling corresponding aptamers, which demonstrate ultralow detection limits of 8 cell L-1 for S. aureus and 2 cell L-1 for E. coli. Such a bioassay indicates a point-of-care strategy of ultrasensitively biomedical detections by encoding specific SERS tags.     

Single-molecule detection of surface-hybridized human papilloma virus DNA for quantitative clinical screening

We present an improved method to quantify viral DNA in human cells at the single- molecule level. Human papilloma virus (HPV)-16 DNA was hybridized to probes that were covalently bound to a glass surface and detected with a single-molecule imaging system. In the single-probe mode, the whole genome and target DNA were fluorescently labeled before hybridization. In the dual-probe mode, a second probe was introduced that has a fluorescently labeled 1-kb DNA strand connected to the 50-nt probe sequence. With the single-probe method, the detection limit was 0.7 copy/cell, which was similar to that reported in a flow system earlier. With the dual-probe method, the linear dynamic range covers 1.44-7000 copies/cell, which is typical of early infection to near-cancer stages. Both methods were applied to cell line samples with known HPV-16 infection, and the result showed a good match with the reported viral load. DNA from cervical cells, collected with the Pap smear sampling method, was spiked with HPV-16 DNA and submitted to this assay to show compatibility with conventional sampling methods. The dual-probe method was further tested with a crudely prepared sample. The cells were heat lyzed and spun down, and the supernatant was immediately submitted to hybridization. Even with reduced hybridization efficiency caused by the interference of cellular materials, we were still able to differentiate infected cells with 600 copies/cell from healthy cells.     

使用光纤实现荧光定量PCR检测

阐述了光纤在荧光定量PCR检测中的应用特点和荧光产生机理,给出了光纤耦合效率的计算公式。介绍了试验装置的构成和工作原理,列举了限制荧光检测的实际问题并提供了消除模块背景的方法。试剂检测的结果证实了使用光纤的检测系统具有很高的检测分辨率和8个数量级以上的动态线性范围,完全满足荧光定量PCR检测的要求。     

New applications advisable for gallium nitride

GaN-based visible light-emitting diodes and laser diodes are already commercialized for a variety of lighting and data storage applications. This materials system is also showing promise for microwave and high power electronics intended for radar, satellite, wireless base stations, and utility grid applications; for biological detection systems; and for a new class of spin-transport electronics (spintronics) in which the spin of charge carriers is exploited.The explosive increase of interest in the AlGaInN family of materials in recent years has been fueled by the application of blue/green/UV light-emitting diodes (LEDs) in full-color displays, traffic lights, automotive lighting, and general room lighting (using so-called white LEDs)¹. In addition, blue/green laser diodes can be used in high storage-capacity digital versatile disk (DVD) systems². AlGaN-based photodetectors are also useful for solar-blind UV detection and have applications as flame sensors for control of gas turbines or detection of missiles.     

Wash-free, electrochemical platform for the quantitative, multiplexed detection of specific antibodies

The diagnosis, prevention, and treatment of many illnesses, including infectious and autoimmune diseases, would benefit from the ability to measure specific antibodies directly at the point of care. Thus motivated, we designed a wash-free, electrochemical method for the rapid, quantitative detection of specific antibodies directly in undiluted, unprocessed blood serum. Our approach employs short, contiguous polypeptide epitopes coupled to the distal end of an electrode-bound nucleic acid "scaffold" modified with a reporting methylene blue. The binding of the relevant antibody to the epitope reduces the efficiency with which the redox reporter approaches, and thus exchanges electrons with, the underlying sensor electrode, producing readily measurable change in current. To demonstrate the versatility of the approach, we fabricated a set of six such sensors, each aimed at the detection of a different monoclonal antibody. All six sensors are sensitive (subnanomolar detection limits), rapid (equilibration time constants ～8 min), and specific (no appreciable cross reactivity with the targets of the other five). When deployed in a millimeter-scale, an 18-pixel array with each of the six sensors in triplicate support the simultaneous measurement of the concentrations of multiple antibodies in a single, submilliliter sample volume. The described sensor platform thus appears be a relatively general approach to the rapid and specific quantification of antibodies in clinical materials.