Construction of multiple concentration gradients for single-cell level drug screening.

Isolation and manipulation of single cells play a crucial role in drug screening. However, previously reported single-cell drug screening lacked multiple-dose concentration gradient studies, which limits their ability to predict drug performance accurately. To solve this problem, we constructed a multiconcentration gradient generator in which a Tai Chi-spiral mixer can accelerate solution mixing in a short time and produce a linear concentration gradient. Later, a gradient generator combined with a single-cell capture array was adopted to investigate the effects of single or combined doses of 5-fluorouracil and cisplatin on human hepatoma cells and human breast carcinoma cells (at the single-cell level). The results showed that both drugs were effective in inhibiting the growth of cancer cells, and the combination was more effective for human hepatoma cells. In addition, the relationship between the biomechanical heterogeneity (e.g., deformability and size) of tumor cells and potential drug resistance at the single-cell level was investigated, indicating that small and/or deformable cells were more resistant than large and/or less deformable cells. The device provides a simple and reliable platform for studying the optimal dosage of different drug candidates at the single-cell level and effectively screening single-agent chemotherapy regimens and combination therapies.

[Cloning and temporal-spatial expression analysis of dfr gene from Scutellaria baicalensis with different colors].

Dihydroflavanol-4-reductase (Dfr) is a key enzyme that regulates the synthesis of anthocyanin and proanthocyanidin in the flavonoid biosynthesis pathway. To investigate the difference of dfr gene in Scutellaria baicalensis Georgi with different colors in the same ecological environment, three complete full-length sequences of dfr gene were cloned from the cDNA of S. baicalensis with white, purple-red and purple colors using homologous cloning and RACE techniques. The three genes were named Sbdfr1, Sbdfr2 and Sbdfr3, respectively, and their corresponding structures were analyzed. The results showed that all three Dfr proteins have highly conserved NADPH binding sites and substrate-specific binding sites. Phylogenetic analysis showed that they are closely related to that of the known S. viscidula (ACV49882.1). Analysis of key structural domains and 3D models revealed differences in the catalytically active regions on the surface of all three Dfr proteins, and their unique structural characteristics may provide favorable conditions for studying the substrate specificity of different Dfr proteins. qRT-PCR analysis shows that dfr was expressed at different level in all tissues except the roots of S. baicalensis in full-bloom. During floral development, the expression level of dfr in white and purple-flowered Scutellaria showed an overall upward trend. In purple-red-flowered Scutellaria, the expression first slowly increased, followed by a decrease, and then rapidly increased to the maximum. This research provides a theoretical basis for further exploring the mechanism and function of Dfr substrate selectivity, and are of great scientific value for elucidating the molecular mechanism of floral color variation in S. baicalensis.

Numerical Study of Multivortex Regulation in Curved Microchannels with Ultra-Low-Aspect-Ratio.

The field of inertial microfluidics has been significantly advanced in terms of application to fluid manipulation for biological analysis, materials synthesis, and chemical process control. Because of their superior benefits such as high-throughput, simplicity, and accurate manipulation, inertial microfluidics designs incorporating channel geometries generating Dean vortexes and helical vortexes have been studied extensively. However, existing technologies have not been studied by designing low-aspect-ratio microchannels to produce multi-vortexes. In this study, an inertial microfluidic device was developed, allowing the generation and regulation of the Dean vortex and helical vortex through the introduction of micro-obstacles in a semicircular microchannel with ultra-low aspect ratio. Multi-vortex formations in the vertical and horizontal planes of four dimension-confined curved channels were analyzed at different flow rates. Moreover, the regulation mechanisms of the multi-vortex were studied systematically by altering the micro-obstacle length and channel height. Through numerical simulation, the regulation of dimensional confinement in the microchannel is verified to induce the Dean vortex and helical vortex with different magnitudes and distributions. The results provide insights into the geometry-induced secondary flow mechanism, which can inspire simple and easily built planar 2D microchannel systems with low-aspect-ratio design with application in fluid manipulations for chemical engineering and bioengineering.

Concentration Gradient Constructions Using Inertial Microfluidics for Studying Tumor Cell-Drug Interactions.

With the continuous development of cancer therapy, conventional animal models have exposed a series of shortcomings such as ethical issues, being time consuming and having an expensive cost. As an alternative method, microfluidic devices have shown advantages in drug screening, which can effectively shorten experimental time, reduce costs, improve efficiency, and achieve a large-scale, high-throughput and accurate analysis. However, most of these microfluidic technologies are established for narrow-range drug-concentration screening based on sensitive but limited flow rates. More simple, easy-to operate and wide-ranging concentration-gradient constructions for studying tumor cell-drug interactions in real-time have remained largely out of reach. Here, we proposed a simple and compact device that can quickly construct efficient and reliable drug-concentration gradients with a wide range of flow rates. The dynamic study of concentration-gradient formation based on successive spiral mixer regulations was investigated systematically and quantitatively. Accurate, stable, and controllable dual drug-concentration gradients were produced to evaluate simultaneously the efficacy of the anticancer drug against two tumor cell lines (human breast adenocarcinoma cells and human cervical carcinoma cells). Results showed that paclitaxel had dose-dependent effects on the two tumor cell lines under the same conditions, respectively. We expect this device to contribute to the development of microfluidic chips as a portable and economical product in terms of the potential of concentration gradient-related biochemical research.

Three-gradient constructions in a flow-rate insensitive microfluidic system for drug screening towards personalized treatment.

Research and development of innovative targeted therapies is a great challenge in the fight against cancer. Although many treatment methods are currently available, there is no simple and effective system for promptly conducting anti-cancer drug screening and dose-response evaluation of the cancer patients to the drug. Herein, we developed an easy and compact flow rate independent microfluidic chip that can rapidly construct three concentration gradients of multiple solutes based on Dean flow under a wide range of flow rates. Chemical gradient dynamics were investigated systematically and quantitatively. Three stable, accurate, and controllable drug gradients were generated to evaluate treatments of two tumor cell lines (MCF-7 and HepG2). Results showed the dose- and time-dependent antitumor effects of the drugs, indicating the suitability of the proposed system to evaluate the individual actions and interactions of the anti-cancer drugs (doxorubicin and cisplatin) on one tumor cell line under the same conditions. In addition, cell viability in the microfluidic chip under gradient conditions showed a linear relationship to the viability of the traditional culture experiment. In summary, our microfluidic device can be used to develop insensitive techniques to operational conditions for simultaneously establishing multi-drug concentration gradients, which has the potential to promote the development of specific drug screening tools for targeting multiple vulnerabilities of tumor cells and evaluating the most effective personalized treatment technique.

Enhanced Gas Sensitivity and Sensing Mechanism of Network Structures Assembled from α-Fe2O3 Nanosheets with Exposed {104} Facets.

Network structures assembled from α-Fe2O3 nanosheets with exposed {104} facets were successfully prepared by heating Fe(NO3)3 solution containing polyvinylpyrrolidone (PVP) in air. The α-Fe2O3 nanosheet-based network structures demonstrate significantly higher response to ethanol and triethylamine than α-Fe2O3 commercial powders. The excellent sensing performances can be ascribed to the exposed (104) facet terminated with Fe atoms. A concept of the unsaturated Fe atoms serving as the sensing reaction active sites is thus proposed, and the sensing reaction mechanism is described at the atomic and molecular level for the first time in detail. The concept of the surface metal atoms with dangling bonds serving as active sites can deepen understanding of the sensing and other catalytic reaction mechanisms and provides new insight into the design and fabrication of highly efficient sensing materials, catalysts, and photoelectronic devices.