Bingwen Yu

A localized temporary negative pressure assisted microfluidic device for detecting keratin 19 in A549 lung carcinoma cells with digital PCR

Digital polymerase chain reaction (dPCR) has played a major role in biological research, especially by providing an accurate counting of single nucleic acid molecules. Here, we present a syringe filter-like microfluidic device to realize sample loading, encapsulation, moisturizing and running dPCR. The gas-permeability of polydimethylsiloxane (PDMS) is utilized for sample loading under negative pressure. The air in the chambers is evacuated to the negative pressure side, resulting in the sample solution entering into the chambers. We also add a vaporproof-layer (VPL) in the chip to moisturize or restrain evaporation caused by the gas-permeability of PDMS under thermal cycling. Digital PCR is applied to test keratin 19 on this microdevice with 650 chambers, each having a volume of 6.28 nL, using the cDNA from the A549 cell line. The results exhibit linear regression under five dilution concentrations, thus demonstrating the robustness of the dPCR chip. This device is easy to be fabricated without multiple overlay exposures or high alignment precision, and should prove to be an effective tool for biological research.

An integrated microfluidic system for bovine DNA purification and digital PCR detection

In this paper, we described an integrated modularized microfluidic system that contained two distinct functional modules, one for nucleic acids (NA) extraction and the other for digital PCR (dPCR), allowing for detecting the bovine DNA in ovine tissue.

Development of particle swarm optimization–support vector regression (PSO-SVR) coupled with microwave plasma torch–atomic emission spectrometry for quality control of ginsengs

As people have become more focused on their own health, the role of ginseng for medical uses has begun to receive substantial interest. However, the quality control of ginseng remains in question because different species vary considerably in this respect. In this paper, particle swarm optimization–support vector regression combined with microwave plasma torch–atomic emission spectrometry (MPT‐AES) was used, for the first time, for quality control of ginseng. To build calibration models, quantitative determination of target element concentrations in ginseng samples was conducted by MPT‐AES because ginseng quality was closely related to the place of origin and can thus be judged by the elemental composition. Characteristic spectral lines were extracted via principal component analysis to reduce the computational effort and improve the representativeness of the input variables. Two heuristic algorithms, particle swarm optimization and a genetic algorithm, were selected to optimize the parameters (eg, c, g, and ε) that were extremely significant in the construction of the support vector regression (SVR) models. Another linear regression approach, partial least squares regression (PLSR), was also used and compared. The comparisons were based on evaluation indexes, namely, the root mean square error and the squared correlation coefficient (R2). A significant difference between SVR and PLSR showed that SVR outperformed PLSR in such a multivariate regression problem. The acquired results showed that particle swarm optimization was slightly better than a genetic algorithm. In conclusion, the proposed MPT‐AES combined with particle swarm optimization–support vector regression is appropriate for quantitative elemental analysis and further application in the quality control of ginseng.

High-speed photographic analysis of microwave plasma torch source behaviour

Spatiotemporal motion characteristics of the microwave plasma torch (MPT) source were for the first time investigated with a high-speed camera. It was found that the cone shape with a central channel of the Ar MPT, which is beneficial for the introduction of the sample analyzed, is formed by the regular and high-speed rotary motion of the discharge filament(s), and it is also the origin of the unique performance compared with other microwave plasma sources. The rotational frequency of the plasma filament is typically 100 Hz, which is affected by the flow-rates and microwave forward power level. To investigate their relationship, the parametric analysis was used, suggesting that the support gas flow-rate is the major factor, followed by microwave power and the carrier gas flow rate. It was also illustrated that the structural symmetry of the torch is important for the stability of the excitation source. In addition, the excitation process of MgCl2 aerosol in the MPT was preliminary studied on the microscopic time scale. Knowledge of this spatiotemporal behaviour is relevant to studies of the fundamental properties of the MPT and its applications.

Support vector machine classification for determination of geographical origin of Chinese ginseng using microwave plasma torch-atomic emission spectrometry

The geographical origin of Chinese ginseng is of great concern to customers, since quality varies tremendously with geographical origin. Therefore, accurately distinguishing the region of origin of specific types of ginseng, in order to differentiate the quality, is of great significance. In this paper, MPT-AES integrated with support vector machine (SVM) was proposed and applied to determine and classify the geographical origin of ginseng samples by using the chemical elemental compositions obtained. Specific data sets were extracted and dimensions were reduced through wavelet transformation. A classification model was built, relying on training sets, and then two parameters (c and g) were optimized in the SVM approach. SVM and Gaussian process classification (GPC) models were evaluated entirely on their prediction accuracy for unknown ginseng samples. Under optimized conditions, SVM outperformed GPC with a prediction accuracy of 100%, compared to 97.41%, in distinguishing the geographical origins. SVM also proved valid in the classification of individual types of ginseng with 99.81% accuracy, compared to GPC with 71.67%. These advanced chemometrics worked well for American ginseng identification. This study illustrates that chemometrics, together with the MPT-AES spectrochemical method, is a helpful and innovative technique for identifying and classifying ginseng samples, and is promising for accurate, convenient, automatic and reliable analysis.

Feasibility of peak volume algorithm in electrothermal vaporization microwave plasma atomic emission spectrometry: FEASIBILITY OF PEAK VOLUME ALGORITHM IN ETV-MPT-AES

Electro‐thermal vaporization has served as an alternative sample introduction method in atomic spectrometry for some time and provided a better solution for quick analysis of complicated samples because of its high sensitivity and effective separation of analyte from matrix materials. The quick heating process produces sharp signals that can provide much better limits of detection with significant improvements compared with the nebulization sample introduction method. However, it also makes the results worse repeatable, which leads to a worse analytical precision. To improve the precision of the newly developed electrothermal vaporization microwave plasma atomic emission spectrometry and to make good use of the limited data obtained in a limited period of time, some different evaluation methods, such as peak height (symbol, Ih), peak area (symbol, IΣt), and peak volume (symbol, IΣλ‐t) for the results treatment are compared in this paper. It comes out that the results calculated by the optimized peak volume algorithm can significantly improve the precision and retain the high linearity at the same time. Limit of detection of this electrothermal vaporization microwave plasma atomic emission spectrometry system used in this paper for Cu was shown to be 1 μg/L, and the relative standard deviation of 11 repeated measurements can be improved from 10% to 5.6% while retaining good linearity, as expressed by both the squared correlation coefficient obtained with optimized peak volume algorithm and with raw peak height method (squared correlation coefficient of the standard curve R2 > 0.999).

Investigation of self-ignition characteristics of the microwave plasma torch

The traditional method for ignition of plasma sustained with the microwave plasma torch (MPT) is by touching the central tube with a metal rod or with the aid of a spark from a Tesla coil, which might put the operator in danger of microwave leakage or might need an additional high-voltage circuit. The resonant characteristics and electric field distribution at the opening end of the torch, especially between the intermediate tube and inner tube of the torch, were simulated. It was shown that by slightly extruding the inner tube, microwave energy can be easily coupled into the ignition region of the MPT. A torch with such configuration was tested and shown to be easily self-ignited. The ignition process was also investigated with a high-speed camera. Therefore, an additional igniter is no longer needed in MPT atomic emission instrumentation, which leads to significant simplification in its construction, enhancement of its usability and reliability, and being beneficial for the commercialization of MPT-AES (MPT atomic emission spectrometry) technology.

Development of a Novel Kilowatt Microwave Plasma Torch Source for Atomic Emission Spectrometry

Traditional low power-microwave plasma torch(MPT) excitation source of atomic emission spectrometry was shown to be good for the introduction of dry aerosols, but poor for wet sample aerosols. In this work, some significant modifications have been made to traditional MPT. A new MPT excitation source working at kilowatt microwave power has been developed. The kilowatt MPT source can sustain stable plasmas with double or even more filaments, presenting a “bell” form, where the region around the converging point is the optimum region for analysis. The tolerance to aqueous aerosol of the torch is enhanced significantly compared to the traditional one. Therefore, the desolvation system that the low power MPT source has to be relied on can be gotten rid of. A set of favorable detection results have been obtained with direct wet sample aerosol introduction. The kilowatt MPT source is expected to become a practical excitation source for atomic emission spectrometry that will be widely used.

Smartphone Based Healthcare Platform and Challenges

With the rapid penetration of mobile devices into society, potential of using smartphones in healthcare are very exciting. Smartphone based healthcare platforms bringing the advanced laboratory instruments to rural areas, develop-ing countries and in case of emergency. It is foreseeable that the ubiquitous smartphone based platform would generate tremendous data. We need to find better ways to manage and analyze them. Other challenges involving reliability, usability and security are also important issues to take into account. Mobile is the future of healthcare. The way of healthcare will be changed stupendously after mitigate the barriers and limitations.

Structure and fabrication details of an integrated modularized microfluidic system

This article contains schemes, original experimental data and figures for an integrated modularized microfluidic system described in “An integrated microfluidic system for bovine DNA purification and digital PCR detection [1]”. In this data article, we described the structure and fabrication of the integrated modularized microfluidic system. This microfluidic system was applied to isolate DNA from ovine tissue lysate and detect the bovine DNA with digital PCR (dPCR). The DNA extraction efficiency of the microdevice was compared with the efficiency of benchtop protocol.