Advances in tumor-endothelial cells co-culture and interaction on microfluidics

The metastasis in which the cancer cells degrade the extracellular matrix （ECM） and invade to the sur- rounding and far tissues of the body is the leading cause of mortality in cancer patients, With a lot of advancement in the field, yet the biological cause of metastasis are poorly understood, The microfluidic system provides advanced technology to reconstruct a variety of in vivo-like environment for studying the interactions between tumor ceils （TCs） and endothelial ceils （ECs）. This review gives a brief account of both two-dimensional models and three-dimensional microfluidic systems for the analysis of TCs-ECs co- culture as well as their applications to anti-cancer drug screening, Furthermore, the advanced methods for analyzing cell-to-cell interactions at single-cell level were also discussed,

A microfluidic photolithography for controlled encapsulation of single cells inside hydrogel microstructures

A microfluidic approach to generate hydrogel microstructures inside microchannels for controlled encapsulation of single cells was developed. The method was based,on a modified microscope projection photolithography which allowed for the photopolymerization of poly（ethylene glycol） diacrylate （PEGDA） inside microchannels. Uniformsized hydrogel microstmctures （-50 pan in diameter） were generated one by one with determined positions to encapsulate single cells without losing the viability. Cells of interest could be identified by any kinds of visible labels to be selectively encapsulated inside the formed hydrogel microstructures. Large-scale encapsulation of single cells was achieved with a relatively high efficiency of 80% and the viability of encapsulated cells could be guaranteed by removing the dead cells identified with Trypan blue. This method is simple, fast and convenient to pattern the microchannels with single cells for a wide range of cell-based applications. For demonstration, two intracellular enzyme assays of carboxylesterase were performed to investigate the distribution of enzyme concentrations and the kinetic information within the encapsulated single HepG2 cells.

Microfluidic adhesion analysis of single glioma cells for evaluating the effect of drugs

Cancer metastasis is one of the most serious problems for tumor therapy,which is closely related to cell adhesion and deadhesion process.Better comprehension of cell adhesion ability will benefit drug research.Here,a biomimetic microfluidic enzyme digestion method was proposed to gently measure the influence of drugs on cell-matrix adhesion ability at the single cell level.The method can selectively digest the extracellular matrix(ECM)that linked to a single cell,and the trypsin concentration around the cell is relatively uniform and constant,thus the measured cell adhesion strength should be precise.Commercially available anti-cancer agents including 5-fluorouracil(5-FU),actinomycin D(Act D),temozolomide(TMZ)and allicin were evaluated,and the data showed only TMZ and allicin can inhibit cell adhesion significantly under our experiment conditions.The influence of TMZ became more and more obvious as the increase of duration and the effect became prominent only after 6 h adhesion process,which could provide a quick evaluation of whether the drugs are effective to cancer cell(compared with Calcein-AM/PI cell viability test).The adhesion strength of U87 cells decreased when the concentration of TMZ increased,and the effect of TMZ can be effectively inhibited by adding lactic acid to culture medium,which indicated acidic tumor microenvironment could promote drug resistance of tumor cells.Different from conventional evaluation methods which focus on the drugs’influence on cellular viability or metabolism,this work provides a new perspective to study the effect of drugs,which is helpful to enrich the drug evaluation system.

Chip-based SALDI-MS for rapid determination of intracellular ratios of glutathione to glutathione disulfide

Alterations in the ratio of glutathione(GSH) to glutathione disulfide(GSSG) reveal the cell living state and are associated with a variety of diseases. In this study, an Au NPs grafted nanoporous silicon chip was used for surface assisted laser desorption ionization-mass spectrometry(SALDI-MS) detection of GSH. Due to the bond interaction between thiol of GSH and Au NPs modified on the chip surfaces, GSH could be captured from the complex cellular lysate. Meanwhile, the composite nanostructures of Au NPs grafted porous silicon surface presented good desorption/ionization efficiency for GSH detection. The GSH levels in different tumor cells were successfully detected. Chip-based SALDI-MS was optimized for quantification of intracellular GSH/GSSG ratio changing under drug stimulation in liver tumor cells, GSSG was reduced to GSH by reductant of tris(2-carboxyethyl)phosphine(TCEP) and isotope-labeling GSH was as an internal standard. It was found that the increasing concentration of drug irinotecan and hypoxia culture condition caused the rapid consumption of GSH and a decrease of GSH/GSSG ratio in liver tumor cells. The developed SALDI-MS method provided a convenient way to accurately measure and rapidly monitor cellular GSH value and the ratios of GSH/GSSG.

Multi-channel microfluidic chip-mass spectrometry platform for cell analysis

In this review, we highlight the latest development of multi-channel microfluidic chip-mass spectrometry（chip-MS） in cell analysis and metabolite detection. Following a brief introduction about history and development of multi-channel microchip and MS combination, we will elaborate the key issues of constructing chip-MS platform interface. Then exciting progresses made in this field should be reviewed with well exemplified works, including chip-MS technology for cell introduction, pretreatment of cell secretions and cell metabolite analysis. We will also describe the development of integrated total analysis systems proposed by our group. We hope this brief review will inspire interested readers and provide knowledge about chip-MS platform in the bioanalysis field, particularly in cell analysis and metabolite identifying applications.

A chemo-mechanical switchable valve on microfluidic chip based on a thermally responsive block copolymer

Microfluidic devices have become a powerful tool for chemical and biologic applications.To control different functional parts on the microchip,valve plays a key role in the device.In conventional methods,physio-mechanical valves are usually used on microfluidic chip.Herein,we reported a chemo-mechanical switchable valve on microfluidic chip by using a thermally responsive block copolymer.The wettability changes of capillary with copolymer modification on inner surface were investigated to verify the function as a valve.Capillaries with modification of poly-(N-isopropylacrylamide-co-hexafluoroisopropyl acrylate)(P(NIPAAm-co-HFIPA))with a 20%HFIPA was demonstrated capable of control aqueous solution stop or go through.Then short capillaries with copolymer modification were integrated in microchannels as valves.With the temperature changing around lower critical solution temperature(LCST),the integrated chemo-mechanical switchable valve exhibited excellent“OPEN–CLOSE”behavior for microflow control.After optimization of the block copolymer sequences and molar ratio,a switching time as low as 20 s was achieved.The developed micro valve was demonstrated effective for flow control on microchip.

Inhibition of anaerobic probiotics on colorectal cancer cells using intestinal microfluidic systems

Intestinal flora play an important role in human's immune system. Many bacteria adhere to the wall of the testinal wall. These Intestinal flora help digestion, and also stop their disease-causing counterparts from invading. Most of the current researches focused on the interaction between cells and the construction of organs, but few researches studied on the role of microorganisms and cells. Here, we developed an in vitro living cell systems to simulate the structure, absorption, transport and pathophysiological characteristics of the human intestinal tract and the key microbial symbiosis. The co-culture of Clostridium butyricum(C.butyricum) and colon cancer cells showed a different immune effect. C. butyricum could inhibit the proliferation of HCT116 cells, cause cell cycle arrest and promote apoptosis. But it had no significant effect on Caco-2 cells. Thus, basic functional characteristics of the gut were successfully simulated in a controlled microfluidic system. This approach is suggested as a powerful method in the investigation on drug metabolism and intestinal diseases.