Huijie Huang

Rapid quantitative detection of Yersinia pestis by lateral-flow immunoassay and up-converting phosphor technology-based biosensor

Abstract Up-converting phosphor technology (UPT)-based lateral-flow immunoassay has been developed for quantitative detection of Yersinia pestis rapidly and specifically. In this assay, 400nm up-converting phosphor particles were used as the reporter. A sandwich immumoassay was employed by using a polyclonal antibody against F1 antigen of Y. pestis immobilized on the nitrocellulose membrane and the same antibody conjugated to the UPT particles. The signal detection of the strips was performed by the UPT-based biosensor that could provide a 980nm IR laser to excite the phosphor particles, then collect the visible luminescence emitted by the UPT particles and finally convert it to the voltage as a signal. V T and V C stand for the multiplied voltage units for the test and the control line, respectively, and the ratio V T/V C is directly proportional to the number of Y. pestis in a sample. We observed a good linearity between the ratio and logCFU/ml of Y. pestis above the detection limit, which was approximately 104 CFU/ml. The precision of the intra- and inter-assay was below 15% (coefficient of variation, CV). Cross-reactivity with related Gram-negative enteric bacteria was not found. The UPT-LF immunoassay system presented here takes less than 30min to perform from the sample treatment to the data analysis. The current paper includes only preliminary data concerning the biomedical aspects of the assay, but is more concentrated on the technical details of establishing a rapid manual assay using a state-of-the-art label chemistry.

Development of an up-converting phosphor technology-based 10-channel lateral flow assay for profiling antibodies against Yersinia pestis

In this study, a 10-channel up-converting phosphor technology-based lateral flow (TC-UPT-LF) assay was developed to profile antibodies against Yersinia pestis. Ten expressed Y. pestis proteins were covalently conjugated with an up-converting phosphor particle to develop double-antigen sandwich immunochromatographic strips to detect corresponding antibodies. After optimization one by one, each strip was integrated into a TC-UPT-LF disc for simultaneously detection of different antibodies. A scanning biosensor was also developed to acquire the results. The performance of the TC-UPT-LF assay was evaluated by using standard samples and plague monkey serum samples. Fifty-one patient serum samples were detected by the TC-UPT-LF assay. The TC-UPT-LF disc could be stable for 10 days at 37°C with an average CV of 10.3%. Its sensitivity and qualitative results are comparable to those of ELISA. Its linearity fitting coefficient of determination (R2) for different antibody detection is between 0.93 and 0.99. Besides F1 antibody, the LcrV and YopD antibodies also showed higher positive ratio than the other seven antibodies, as 100% (13/13) and 92% (12/13) in monkey sera and 86.3% (44/51) and 66.7% (34/51) in patient sera, respectively. It is suggested that the TC-UPT-LF assay has been successfully developed for multi-detection and LcrV and YopD can be the potential diagnostic markers of the plague.

A Simple Optical Reader for Upconverting Phosphor Particles Captured on Lateral Flow Strip

A simple optical reader was developed for rapid and sensitive quantification of lateral flow (LF) strip with upconverting phosphor (UCP) particles as reporters. The excitation beam from a 980 nm laser diode (LD) was focused to a 4 mm (length) times 0.02 mm (width) rectangular spot on LF strip. A rectangular slit with 4 mm times 0.02 mm before the photomultiplier tube (PMT) which was selected as receiver was introduced as field diaphragm to prevent stray light from entering the PMT. The scanning resolution was 20 mum, and the scanning speed was 0.75 mm/s, and the scanning range was 10 mm. With the above optical reader, serial dilutions of Yersinia pestis F1 antigen were detected to achieve the test sensitivity was 5 ng/ml, and the dynamic range reached 150 ng/ml. The algorithms of the low-pass filter and the first derivative were used to search the boundaries of T line and C line from the original data acquired by the reader. A four-parameter logistic mathematical model was used to deduce the quantitative equation for determination of unknown F1 antigen concentration. Our 1-D optical reader possessed the following characteristics: high 1-D testing resolution, high sensitivity, simple structure, simple data processing method, high testing efficiency, and small total volume.

An approach to increase efficiency of DOE based pupil shaping technique for off-axis illumination in optical lithography

Off axis illumination (OAI) is one of the key resolution enhancement technologies in projection lithography system. Recently, phase type diffractive optical elements (DOEs) are adopted by most of the lithography machine manufactures to realize OAI. In general, the efficiency of the OAI unit is the main consideration compared with uniformity. However, the main goal of the traditional constraint of iterative Fourier transformation algorithm (IFTA) is used to optimize the SNR, while diffraction efficiency is the secondary consideration. Therefore a constraint for IFTA is well designed to increase the efficiency of DOE in this paper. This constraint can guarantee the pole balance at the same time. The main idea of this constraint is to apply amplitude and phase freedoms in the signal window and to control the total energy of each pole. Based on the proposed constraint several DOEs are designed for high NA lithography illumination system. And remarkable improvement in the efficiency is observed compared with the traditional constraint. Furthermore, the efficiency and uniformity could be weighted by adjusting the parameter with extending this constraint to general case. To demonstrate the proposed constraints, experiments are carried out where a spatial light modulator is utilized to represent DOEs.

Impact of temperature, CO2 fixation and nitrate reduction on selenium reduction, by a paddy soil Clostridium strain

To elucidate the impact of CO2 fixation, nitrate reduction and temperature on selenium reduction by a newly identified acetogenic bacterium, Clostridium sp. BXM.

Study of a dual-frequency laser interferometer with unique optical subdivision techniques

A dual-frequency laser interferometer has been developed based on a low-performance commercial interferometer. An optical resolution of 1.24 nm and a nanometer-scale accuracy have been achieved by using unique techniques to obtain an optical subdivision factor of 1/8. A method for reducing static positioning errors was also shown. The measurement of a free-falling body was performed to test the maximum achievable target velocity of the device. The experimental setup for measuring the static positioning errors was also given. The new interferometer could be widely used in nanometer-scale fabrications and measurements.

Lateral shearing interferometer with variable shearing for measurement of a small beam

A lateral shearing interferometer with variable shearing for measurement of a small beam is proposed. The interferometer is composed of a polarization beam splitter, a thick birefringent plate, a quarter-wave plate, a mirror, and an image sensor. The shearing amount can be tiny by using the thick birefringent plate as the shear generator. The shearing amount of the interferometer can be continuously adjusted by rotating the thick birefringent plate, and 2D interferograms can be obtained by rotating the thick birefringent plate along the mutually perpendicular directions. The optical path difference is compensated with a double lateral shearing by using a quarter-wave plate and a mirror. The interferometer is verified by simulation and experiment; the experiment result is well coincident with the simulation result. The usefulness of the interferometer is verified.

Model of freeform illumination mode and polarization mode for 193nm immersion lithographic machine

The 193nm immersion lithographic machine has already achieved 22nm node and beyond, and its illuminator has become a polarized and off-axis illumination system. Illumination modes and polarization modes can be formed by different diffraction optical elements and polarization optical elements. This paper proposes a model including a micromirror array and a variable retarder array for forming freeform illumination mode and polarization mode. They can be achieved by controlling the retardations of the variable retarders and two-dimensional tilt angles of the micromirrors. The principles of the model are analyzed, and some equations are acquired. Circular illumination mode, tangential polarization modes have been obtained in the simulation experiments. The simulation results show the model is feasible for the 193 nm immersion lithography machine.

Multiplexed bead-based mesofluidic system for gene diagnosis and genotyping.

We have developed a novel multiplexed bead-based mesofluidic system (MBMS) based on the specific recognition events on the surface of a series of microbeads (diameter 250 μm) arranged in polydimethylsiloxane (PDMS) microchannels (diameter 300 μm) with the predetermined order and assembled an apparatus implementing automatically the high-throughput bead-based assay and further demonstrated its feasibility and flexibility of gene diagnosis and genotyping, such as β-thalassemia mutation detection and HLA-DQA genotyping. The apparatus, consisting of bead-based mesofluidic PDMS chip, liquid-processing module, and fluorescence detection module, can integrate the procedure of automated-sampling, hybridization reactions, washing, and in situ fluorescence detection. The results revealed that MBMS is fast, has high sensitivity, and can be automated to carry out parallel and multiplexed genotyping and has the potential to open up new routes to flexible, high-throughput approaches for bioanalysis.

Design and application of fiber optic evanescent wave biosensor

A fiber-optic biosensor is developed based on the principle of evanescent wave while light propagates in optical fiber. The biosensor uses a red laser diode at 636.85 nm for exciting Cy5 fluorescent dye. Sensitivity limit of 0.01 nnmol/l is obtained from the detection of serial Cy5 solutions with various concentrations. In log-to-log plot, excellent linear response characteristic is seen in the Cy5 concentrations ranging from 0.01 nmlo/l to 100 nmol/l. And a good result of signal-to-noise ratio of 4.61 is obtained when the biosensor is used to measure Legionella pneumophila solution of 0.01 μmol/l. All the results are comparable with those that are obtained by a commercial biochip scanner GeneTAC 1000.