Bingcheng Lin

Rapid prototyping of paper-based microfluidics with wax for low-cost, portable bioassay

Here we present a simple and low‐cost production method to generate paper‐based microfluidic devices with wax for portable bioassay. The wax patterning method we introduced here included three different ways: (i) painting with a wax pen, (ii) printing with an inkjet printer followed by painting with a wax pen, (iii) printing by a wax printer directly. The whole process was easy to operate and could be finished within 5–10 min without the use of a clean room, UV lamp, organic solvent, etc. Horse radish peroxidase, BSA and glucose assays were conducted to verify the performance of wax‐patterned paper.

Fabrication and Characterization of Paper-Based Microfluidics Prepared in Nitrocellulose Membrane By Wax Printing

Paper-based microfluidics is a promising technology to develop a simple, low-cost, portable, and disposable diagnostic platform for resource-limited settings. Here we report the fabrication of paper-based microfluidic devices in nitrocellulose membrane by wax printing for protein immobilization related applications. The fabrication process, which can be finished within 10 min, includes mainly printing and baking steps. Wax patterning will form hydrophobic regions in the membrane, which can be used to direct the flow path or separate reaction zones. The fabrication parameters like printing mode and baking time were optimized, and performances of the wax-patterned nitrocellulose membrane such as printing resolution, protein immobilization, and sample purification capabilities were also characterized in this report. We believe the wax-patterned nitrocellulose membrane will enhance the capabilities of paper microfluidic devices and bring new applications in this field.

Purification and identification of a ACE inhibitory peptide from oyster proteins hydrolysate and the antihypertensive effect of hydrolysate in spontaneously hypertensive rats

Oyster (Crassostrea talienwhanensis Crosse) proteins were produced from fresh oyster and subsequently digested with pepsin. The separations were performed with a Sephadex LH-20 gel filtration chromatography and a RP-HPLC. A purified peptide with sequence Val-Val-Tyr-Pro-Trp-Thr-Gln-Arg-Phe (VVYPWTQRF) was firstly isolated and characterized from oyster protein hydrolysate and its ACE inhibitory activity was determined with IC50 value of 66μmol/L in vitro. Stability study for ACE inhibitory activity showed that the isolated nonapeptide had the good heat and pH stability and strong enzyme-resistant properties against gastrointestinal proteases. Kinetic experiments demonstrated that inhibitory kinetic mechanism of this peptide was non-competitive and its Km and Ki values were calculated. The yield of this peptide from oyster proteins was 8.5%. Furthermore, the oyster protein hydrolysate (fraction II), prepared by pepsin treatment firstly exhibited antihypertensive activity when it was orally administered to spontaneously hypertensive rat (SHR) at a dose of 20mg/kg. These results demonstrated that the hydrolysate from oyster proteins prepared by pepsin treatment could serve as a source of peptides with antihypertensive activity.

Electrophoretic separations on microfluidic chips

Abstract This review presents a brief outline and novel developments of electrophoretic separation in microfluidic chips. Distinct characteristics of microchip electrophoresis (MCE) are discussed first, in which sample injection plug, joule heat, channel turn, surface adsorption and modification are introduced, and some successful strategies and recognized conclusions are also included. Important achievements of microfluidic electrophoresis separation in small molecules, DNA and protein are then summarized. This review is aimed at researchers, who are interested in MCE and want to adopt MCE as a functional unit in their integrated microsystems.

Determination of SARS-coronavirus by a microfluidic chip system.

We have developed a new experimental system based on a microfluidic chip to determine severe acute respiratory syndrome coronavirus (SARS‐CoV). The system includes a laser‐induced fluorescence microfluidic chip analyzer, a glass microchip for both polymerase chain reaction (PCR) and capillary electrophoresis, a chip thermal cycler based on dual Peltier thermoelectric elements, a reverse transcription‐polymerase chain reaction (RT‐PCR) SARS diagnostic kit, and a DNA electrophoretic sizing kit. The system allows efficient cDNA amplification of SARS‐CoV followed by electrophoretic sizing and detection on the same chip. To enhance the reliability of RT‐PCR on SARS‐CoV detection, duplex PCR was developed on the microchip. The assay was carried out on a home‐made microfluidic chip system. The positive and the negative control were cDNA fragments of SARS‐CoV and parainfluenza virus, respectively. The test results showed that 17 positive samples were obtained among 18 samples of nasopharyngeal swabs from clinically diagnosed SARS patients. However, 12 positive results from the same 18 samples were obtained by the conventional RT‐PCR with agarose gel electrophoresis detection. The SARS virus species can be analyzed with high positive rate and rapidity on the microfluidic chip system.

Grafting epoxy-modified hydrophilic polymers onto poly(dimethylsiloxane) microfluidic chip to resist nonspecific protein adsorption

In order to achieve a simple covalent hydrophilic polymer coating on poly(dimethylsiloxane) (PDMS) microfluidic chip, epoxy modified hydrophilic polymers were synthesized in aqueous solution with a persulfate radical initiation system, and crosslinked onto PDMS pretreated by oxygen plasma and silanized with 3-aminopropyl-triethoxysilanes (APTES). Glycidyl methacrylate (GMA) was copolymerized with acrylamide (poly(AAM-co-GMA)) or dimethylacrylamide (poly(DAM-co-GMA)), and graft polymerized with polyvinylpyrrolidone (PVP-g-GMA) or polyvinylalcohol (PVA-g-GMA). The epoxy groups in the polymers were determined by UV spectra after derivation with benzylamine. Reflection absorption infrared spectroscopy (RAIRS) confirmed covalent grafting of GMA-modified polymers onto PDMS surface. Electroosmotic flow (EOF) in the polymer grafted microchannel was strongly suppressed within the range pH 3-11. Surface adsorption of lysozyme and bovine serum albumin (BSA) was reduced to less than 10% relative to that on the native PDMS surface. On the GMA-modified polymer coated PDMS microchip, basic proteins, peptides, and sodium dodecyl sulfate (SDS) denatured proteins were separated successfully.

Low cost, portable detection of gold nanoparticle-labeled microfluidic immunoassay with camera cell phone.

This paper describes the use of camera cell phone to detect the gold nanoparticle‐labeled immunoassay results on microfluidic chip. On‐chip heterogeneous immunoassay between anti‐human IgG and human IgG (hIgG) was performed and the results were amplified by gold nanoparticle‐enhanced silver staining to transform the nano‐scale probe into detectable silver precipitation film. The detection results obtained by camera phone showed good correlation with the concentration of hIgG. This detection scheme is simple, low cost and easy to use and has significant promise for portable diagnosis and point of care testing on microfluidic platform.

A microfluidic device for characterizing the invasion of cancer cells in 3-D matrix

A microfluidic device was developed for the study of directed invasion of cancer cells in 3‐D matrix with concentration gradient. This device consists of two parallel perfusion channels connected by two cell culture chambers. To mimic extracellular matrix (ECM), gelled basement membrane extract (BME) was used to support 3‐D distribution of breast cancer cells (MCF7) in cell culture chambers. A stable linear concentration gradient of epidermal growth factor (EGF) was generated across the chambers by continuous perfusion. Using the device, we investigated MCF7 cell invasion induced by different concentrations of EGF in 3‐D matrix. It was found that cancer cells responded to EGF stimulation with forming cellular protrusions and migrating towards high EGF concentration. We further investigated the anti‐invasion effect of GM 6001, a matrix metalloproteinase inhibitor. We identified that matrix metalloproteinase inhibition repressed both cellular protrusion formation and cell migration in 3‐D matrix. These findings suggest that EGF is able to induce MCF7 cell invasion in 3‐D extracellular matrix and this effect is dependent on proteolytic activity. This device is relatively simple to construct and operate. It should be a useful platform for elucidating the mechanism of cancer invasion and screening anti‐invasion drugs for cancer therapy.

Characterization of the interaction between fibroblasts and tumor cells on a microfluidic co-culture device

Fibroblasts and tumor cells have been involved in the process of cancer development, progression and therapy. Here, we present a simple microfluidic device which enables to study the interaction between fibroblasts and tumor cells by indirect contact co‐culture. The device is composed of multiple cell culture chambers which are connected by a parallel of cell migration regions, and it enables to realize different types of cells to communicate each other on the single device. In this work, human embryonic lung fibroblasts cells were observed to exhibit obvious migration towards tumor cells instead of normal epithelial cells on the co‐culture device. Moreover, transdifferentiation of human embryonic lung fibroblast cells was recognized by the specific expression of α‐smooth musle actin, indicating the effect of tumor cells on the behavior of fibroblasts. Furthermore, multiple types of cell co‐culture can be demonstrated on the single device which enables to mimic the complicated microenviroment in vivo. The device is simple and easy to operate, which enables to realize real‐time observation of cell migration after external stimulus. This microfluidic device allows for the characterization of various cellular events on a single device sequentially, faciliating the better understanding of interaction between heterotypic cells in a more complex microenvironment.

Separation of enatiomers of drugs by capillary electrophoresis III. β-cyclodextrin as chiral solvating agent

Enantiomer separation by capillary zone electrophoresis was studied for a set of 34 chiral drugs. Keeping the concentration of beta-cyclodextrin as a chiral solvating agent as constant as possible led to the separation of seven enantiomeric pairs. Carvedilol, Tetryzoline, Tropicamide and Zopiclone gave a baseline separation, Chlorphenamine, Ketamine, and Orciprenaline a partial separation. Statistical analysis revealed that the best separation factors were observed for a medium degree of interaction with the cyclodextrin. A theory explaining this effect provides a helpful guideline for further optimization.