Name: photopatterning proteins and cells in aqueous environment using tio2 photocatalysis
Uploaded: 2015-10-26T15:00:00
Description: Watch this Scientific Journal Video about Photopatterning Proteins and Cells in Aqueous Environment Using TiO2 Photocatalysis at JoVE.com

Authors thank Mr. Kotaro Okubo for the kind assistance with SEM imaging. This work was supported by the Japan Society for the Promotion of Science Grant-in-Aid for Basic Research (B) (20310069), Grant-in-Aid for Research Activity Start-up (25880021), and by research grants from the Kurata Memorial Hitachi Science and Technology Foundation and the Nippon Sheet Glass Foundation for Materials Science and Engineering.

1. Preparation of TiO2-coated Glass Coverslip
<ol>
	<li>Number the coverslips using a diamond scriber. This helps not only to keep track of each coverslips but also to ensure that the correct side of the sample is facing up. Clean the coverslips, first under running ddH2O, then by immersing them in piranha solution (H2SO4:H2O2 = 4:1). After 10 min, rinse the coverslips thoroughly, 8 times in ddH2O. Dry the coverslips under N2 flow.<...

<ol>
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(46), e2514 (2010).</li><li>Nakanishi, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoactivation+of+a+Substrate+for+Cell+Adhesion+under+Standard+Fluorescence+Microscopes.">Photoactivation of a Substrate for Cell Adhesion under Standard Fluorescence Microscopes.</a> J. Am. Chem. Soc. 126, 16314-16315 (2004).</li><li>Kim, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Addressable+Micropatterning+of+Multiple+Proteins+and+Cells+by+Microscope+Projection+Photolithography+Based+on+a+Protein+Friendly+Photoresist.">Addressable Micropatterning of Multiple Proteins and Cells by Microscope Projection Photolithography Based on a Protein Friendly Photoresist.</a> Langmuir. 26, 12112-12118 (2010).</li><li>Deka, G., Okano, K., Kao, F. -. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+Photopatterning+of+Cells+In+Situ+by+Q-Switched+Neodymium-Doped+Yttrium+Ortho-Vanadate.">Dynamic Photopatterning of Cells In Situ by Q-Switched Neodymium-Doped Yttrium Ortho-Vanadate.</a> Laser. J. Biomed. Opt. 19, 011012 (2014).</li><li>Robertus, J., Browne, W. R., Feringa, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+Control+over+Cell+Adhesive+Properties+using+Molecular-Based+Surface+Engineering+Strategies.">Dynamic Control over Cell Adhesive Properties using Molecular-Based Surface Engineering Strategies.</a> Chem. Soc. Rev. 39, 354-378 (2010).</li><li>Choi, I., Yeo, W. -. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Assembled+Monolayers+with+Dynamicity+Stemming+from+(Bio)chemical+Conversions:+From+Construction+to+Application.">Self-Assembled Monolayers with Dynamicity Stemming from (Bio)chemical Conversions: From Construction to Application.</a> ChemPhysChem. 14, 55-69 (2013).</li><li>Nakanishi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Switchable+Substrates+for+Analyzing+and+Engineering+Cellular+Functions.">Switchable Substrates for Analyzing and Engineering Cellular Functions.</a> Chem. 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Nanotech. 13, 213-218 (2015).</li><li>Arima, Y., Iwata, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Surface+Functional+Groups+on+Protein+Adsorption+and+Subsequent+Cell+Adhesion+using+Self-Assembled+Monolayers.">Effects of Surface Functional Groups on Protein Adsorption and Subsequent Cell Adhesion using Self-Assembled Monolayers.</a> J. Mater. Chem. 17, 4079-4087 (2007).</li><li>Fujishima, A., Zhang, X., Tryk, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TiO2+Photocatalysis+and+Related+Surface+Phenomena.">TiO2 Photocatalysis and Related Surface Phenomena.</a> Surf. Sci. Rep. 63, 515-582 (2008).</li><li>Sigal, G. B., Mrksich, M., Whitesides, G. 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In our current protocol, TiO2 film was formed by RF-magnetron sputtering. We favor this method of deposition since it allows us to reproducibly prepare a photocatalytic TiO2 film with a sub-nm roughness. Although sputter deposition processes are familiar to materials scientists and electronic engineers, it may not be quite accessible to biologists. In that case, spin-coated TiO2 film would be an alternative choice23. In this method, TiO2 nanoparticles dissolved in a ...

Semiconductor lithography processes and its derivatives &#8212; such as photolithography1,2, electron-beam lithography3-6, and microcontact printing7-10 &#8212; have now become an established tool in cell biology to grow living cells in a defined position and geometry. The patterning method relies on the use of microfabricated substrates, consisting of micro-island of cell permissive coating in a non-permissive background. Such substrate serves as a template to pattern the cells. These technologies have provided us the novel methods to engineer cells and their function at a single- and multi-cellular level, to extract the intrinsic properties of cells, and to increase the throughput of cell-based drug screening11.
The degree-of-freedom in cell patterning would greatly increase if the template pattern geometry could be altered in situ, i.e., while cells are cultured on the surface. The conventional methods for pattern formation cannot be directly applied here, since they process samples in atmosphere or in vacuum. Therefore various new surface modification techniques have been proposed, which are based, e.g., on photoreactive compounds12,13 or laser ablation5,14, just to name a few. The proposed methods have been nicely reviewed by Robertus et al.15, and more recently by Choi et al.16 and by Nakanishi17.
Here in this article, we describe a novel protocol of in-situ surface modification, which takes advantage of photocatalytic decomposition of organic molecules on a titanium dioxide (TiO2) surface18,19. In this method, a TiO2 film is inserted between the glass substrate and the organic film that interfaces the cells, and the organic film is decomposed in situ by locally irradiating ultraviolet (UV) light to a region of interest (&#955; &#60; 388 nm). We show that the new protocol can be used to create micropatterns of extracellular matrix proteins and living cells both ex situ and in situ. TiO2 is biocompatible, chemically stable, and optically transparent, features of which makes it friendly to introduce in cell-culture experiments. This protocol provides a materials science-based alternative for modifying cell-culture scaffolds in cell-culture environment.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Glass coverslip</td>
			<td>Warner Instruments</td>
			<td>CS-15R15</td>
			<td>15 mm, #1.5 thickness</td>
		</tr>
		<tr>
			<td>Diamond scriber</td>
			<td>Ogura Jewel Industry</td>
			<td>D-Point Pen</td>
			<td></td>
		</tr>
		<tr>
			<td>RF sputtering system</td>
			<td>ANELVA</td>
			<td>SPC350</td>
			<td></td>
		</tr>
		<tr>
			<td>TiO2 sputtering target</td>
			<td>Kojundo Chemical Lab</td>
			<td>Titanium (IV) oxide, target</td>
			<td>Purity, 99.9%</td>
		</tr>
		<tr>
			<td>Plasma reactor</td>
			<td>Yamato</td>
			<td>PR301</td>
			<td></td>
		</tr>
		<tr>
			<td>n-octadecyltrichlorosilane 
			(OTS)</td>
			<td>Aldrich</td>
			<td>104817</td>
			<td></td>
		</tr>
		<tr>
			<td>Toluene</td>
			<td>Wako</td>
			<td>204-01866</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue-culture dish (35 mm)</td>
			<td>Greiner</td>
			<td>627160</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue-culture dish (60 mm)</td>
			<td>BD Falcon</td>
			<td>353002</td>
			<td></td>
		</tr>
		<tr>
			<td>Type-IV collagen</td>
			<td>Nitta Gelatin</td>
			<td>Cellmatrix Type IV</td>
			<td></td>
		</tr>
		<tr>
			<td>D-PBS</td>
			<td>Gibco</td>
			<td>14190-144</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s modified Eagle&#39;s medium (DMEM)</td>
			<td>Gibco</td>
			<td>11885-084</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Gibco</td>
			<td>12483-020</td>
			<td>Heat-inactivate and pass through a 0.22 mm filter before use</td>
		</tr>
		<tr>
			<td>Horse serum</td>
			<td>Gibco</td>
			<td>26050-088</td>
			<td>Pass through a 0.22 mm filter before use</td>
		</tr>
		<tr>
			<td>Penicillin-streptomycin (100x)</td>
			<td>Nacalai tesque</td>
			<td>26253-84</td>
			<td></td>
		</tr>
		<tr>
			<td>7S nerve growth factor (NGF)</td>
			<td>Alomone Labs</td>
			<td>N-130</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA)</td>
			<td>Sigma</td>
			<td>A2153</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Dojindo</td>
			<td>N001</td>
			<td>Stock solution in 0.5 M</td>
		</tr>
		<tr>
			<td>TiO2 nanoparticle</td>
			<td>Tayca</td>
			<td>TKD-701</td>
			<td></td>
		</tr>
	</tbody>
</table>

photopatterning proteins and cells in aqueous environment using tio2 photocatalysis

Organic contaminants adsorbed on the surface of titanium dioxide (TiO2) can be decomposed by photocatalysis under ultraviolet (UV) light. Here we describe a novel protocol employing the TiO2 photocatalysis to locally alter cell affinity of the substrate surface. For this experiment, a thin TiO2 film was sputter-coated on a glass coverslip, and the TiO2 surface was subsequently modified with an organosilane monolayer derived from octadecyltrichlorosilane (OTS), which inhibits cell adhesion. The sample was immersed in a cell culture medium, and focused UV light was irradiated to an octagonal region. When a neuronal cell line PC12 cells were plated on the sample, cells adhered only on the UV-irradiated area. We further show that this surface modification can also be performed in situ, i.e., even when cells are growing on the substrate. Proper modification of the surface required an extracellular matrix protein collagen to be present in the medium at the time of UV irradiation. The technique presented here can potentially be employed in patterning multiple cell types for constructing coculture systems or to arbitrarily manipulate cells under culture.

Figure 2A shows a cross-sectional scanning electron microscopy (SEM) image of the sputter-deposited TiO2 film. From the observation, thickness of the film was estimated to be approximately 150 nm. Noticeable here is the flatness of the deposited TiO2 film. Further analysis by atomic force microscopy (AFM) revealed that the root-mean-square (rms) roughness of the surface was 0.2 nm (Figure 2B).
When the TiO2 surface is modified ...

Watch this Scientific Journal Video about Photopatterning Proteins and Cells in Aqueous Environment Using TiO2 Photocatalysis at JoVE.com

Photopatterning Proteins and Cells in Aqueous Environment Using TiO2 Photocatalysis

We describe a protocol for modifying cell affinity of a scaffold surface in aqueous environment. The method takes advantage of titanium dioxide photocatalysis to decompose organic film in the photo-irradiated region. We show that it can be used to create microdomains of scaffolding proteins, both ex situ and in situ.

Photopatterning Proteins and Cells in Aqueous Environment Using TiO2 Photocatalysis

Organic contaminants adsorbed on the surface of titanium dioxide (TiO2) can be decomposed by photocatalysis under ultraviolet (UV) light. Here we describe ...

photopatterning-proteins-cells-aqueous-environment-using-tio2

Research

JoVE Journal

Bioengineering

Fabrication of Electrochemical-DNA Biosensors for the Reagentless Detection of Nucleic Acids, Proteins and Small Molecules

As medicine is currently practiced, doctors send specimens to a central laboratory for testing and thus must wait hours or days to 
receive the results. Many patients would be better served by rapid, bedside tests. To this end our laboratory and others have developed a versatile, reagentless 
biosensor platform that supports the quantitative, reagentless, electrochemical detection of nucleic acids (DNA, RNA), proteins (including antibodies) and small 
molecules analytes directly in unprocessed clinical and environmental samples. In this video, we demonstrate the preparation and use of several biosensors in this 
"E-DNA" class. In particular, we fabricate and demonstrate sensors for the detection of a target DNA sequence in a polymerase chain reaction mixture, an HIV-specific antibody and the drug cocaine. The preparation procedure requires only three hours of hands-on effort followed by an overnight incubation, and their use requires only minutes.

"E-DNA" sensors, reagentless, electrochemical biosensors that perform well even when challenged directly in blood and other complex matrices, have been adapted to the detection of a wide range of nucleic acid, protein and small molecule analytes. Here we present a general procedure for the fabrication and use of such sensors.

As medicine is currently practiced, doctors send specimens to a central laboratory for testing and thus must wait hours or days to 
receive the results. ...

Visualizing Proteins and Macromolecular Complexes by Negative Stain EM: from Grid Preparation to Image Acquisition

Single particle electron microscopy (EM), of both negative stained or frozen hydrated biological samples, has become a versatile tool in structural biology 1. In recent years, this method has achieved great success in studying structures of proteins and macromolecular complexes 2, 3. Compared with electron cryomicroscopy (cryoEM), in which frozen hydrated protein samples are embedded in a thin layer of vitreous ice 4, negative staining is a simpler sample preparation method in which protein samples are embedded in a thin layer of dried heavy metal salt to increase specimen contrast 5. The enhanced contrast of negative stain EM allows examination of relatively small biological samples. In addition to determining three-dimensional (3D) structure of purified proteins or protein complexes 6, this method can be used for much broader purposes. For example, negative stain EM can be easily used to visualize purified protein samples, obtaining information such as homogeneity/heterogeneity of the sample, formation of protein complexes or large assemblies, or simply to evaluate the quality of a protein preparation.
In this video article, we present a complete protocol for using an EM to observe negatively stained protein sample, from preparing carbon coated grids for negative stain EM to acquiring images of negatively stained sample in an electron microscope operated at 120kV accelerating voltage. These protocols have been used in our laboratory routinely and can be easily followed by novice users.

Visualizing protein samples by negative stain electron microscopy (EM) has become a popular structural analysis method. It is useful for quantitative structural analysis, such as calculating a 3D reconstruction of the molecules being studied, and also for qualitative examination of the quality of protein preparations. In this article we present detailed protocols for preparing the EM grids, staining the sample and visualizing the sample in an electron microscope. Novice users can follow these protocols easily and to utilize negative stain EM as a routine assay, in addition to other biochemical assays, for evaluating their protein samples.

Single particle electron microscopy (EM), of both negative stained or frozen hydrated biological samples, has become a versatile tool in structural ...

A Toolkit to Enable Hydrocarbon Conversion in Aqueous Environments

This work puts forward a toolkit that enables the conversion of alkanes by Escherichia coli and presents a proof of principle of its applicability. The toolkit consists of multiple standard interchangeable parts (BioBricks)9 addressing the conversion of alkanes, regulation of gene expression and survival in toxic hydrocarbon-rich environments.
A three-step pathway for alkane degradation was implemented in E. coli to enable the conversion of medium- and long-chain alkanes to their respective alkanols, alkanals and ultimately alkanoic-acids. The latter were metabolized via the native &beta;-oxidation pathway. To facilitate the oxidation of medium-chain alkanes (C5-C13) and cycloalkanes (C5-C8), four genes (alkB2, rubA3, rubA4and rubB) of the alkane hydroxylase system from Gordonia sp. TF68,21 were transformed into E. coli. For the conversion of long-chain alkanes (C15-C36), theladA gene from Geobacillus thermodenitrificans was implemented. For the required further steps of the degradation process, ADH and ALDH (originating from G. thermodenitrificans) were introduced10,11. The activity was measured by resting cell assays. For each oxidative step, enzyme activity was observed.
To optimize the process efficiency, the expression was only induced under low glucose conditions: a substrate-regulated promoter, pCaiF, was used. pCaiF is present in E. coli K12 and regulates the expression of the genes involved in the degradation of non-glucose carbon sources.
The last part of the toolkit - targeting survival - was implemented using solvent tolerance genes, PhPFD&alpha; and &beta;, both from Pyrococcus horikoshii OT3. Organic solvents can induce cell stress and decreased survivability by negatively affecting protein folding. As chaperones, PhPFD&alpha; and &beta; improve the protein folding process e.g. under the presence of alkanes. The expression of these genes led to an improved hydrocarbon tolerance shown by an increased growth rate (up to 50%) in the presences of 10% n-hexane in the culture medium were observed.
Summarizing, the results indicate that the toolkit enables E. coli to convert and tolerate hydrocarbons in aqueous environments. As such, it represents an initial step towards a sustainable solution for oil-remediation using a synthetic biology approach.

A sustainable auto regulating bacterial system for the remediation of oil pollutions was designed using standard interchangeable DNA parts (BioBricks). An engineered E. coli strain was used to degrade alkanes via &beta;-oxidation in toxic aqueous environments. The respective enzymes from different species showed alkane degradation activity. Additionally, an increased tolerance to n-hexane was achieved by introducing genes from alkane-tolerant bacteria.

This work puts forward a toolkit that enables the conversion of alkanes by Escherichia coli and presents a proof of principle of its applicability. The ...

Time-lapse Fluorescence Imaging of Arabidopsis Root Growth with Rapid Manipulation of The Root Environment Using The RootChip

The root functions as the physical anchor of the plant and is the organ responsible for uptake of water and mineral nutrients such as nitrogen, phosphorus, sulfate and trace elements that plants acquire from the soil. If we want to develop sustainable approaches to producing high crop yield, we need to better understand how the root develops, takes up a wide spectrum of nutrients, and interacts with symbiotic and pathogenic organisms. To accomplish these goals, we need to be able to explore roots in microscopic detail over time periods ranging from minutes to days.
We developed the RootChip, a polydimethylsiloxane (PDMS)- based microfluidic device, which allows us to grow and image roots from Arabidopsis seedlings while avoiding any physical stress to roots during preparation for imaging1 (Figure 1). The device contains a bifurcated channel structure featuring micromechanical valves to guide the fluid flow from solution inlets to each of the eight observation chambers2. This perfusion system allows the root microenvironment to be controlled and modified with precision and speed. The volume of the chambers is approximately 400 nl, thus requiring only minimal amounts of test solution.
Here we provide a detailed protocol for studying root biology on the RootChip using imaging-based approaches with real time resolution. Roots can be analyzed over several days using time lapse microscopy. Roots can be perfused with nutrient solutions or inhibitors, and up to eight seedlings can be analyzed in parallel. This system has the potential for a wide range of applications, including analysis of root growth in the presence or absence of chemicals, fluorescence-based analysis of gene expression, and the analysis of biosensors, e.g. FRET nanosensors3.

This article provides a protocol for cultivation of Arabidopsis seedlings in the RootChip, a microfluidic imaging platform that combines automated control of growth conditions with microscopic root monitoring and FRET-based measurement of intracellular metabolite levels.

The root functions as the physical anchor of the plant and is the organ responsible for uptake of water and mineral nutrients such as nitrogen, ...

Cell Co-culture Patterning Using Aqueous Two-phase Systems

Cell patterning technologies that are fast, easy to use and affordable will be required for the future development of high throughput cell assays, platforms for studying cell-cell interactions and tissue engineered systems. This detailed protocol describes a method for generating co-cultures of cells using biocompatible solutions of dextran (DEX) and polyethylene glycol (PEG) that phase-separate when combined above threshold concentrations. Cells can be patterned in a variety of configurations using this method. Cell exclusion patterning can be performed by printing droplets of DEX on a substrate and covering them with a solution of PEG containing cells. The interfacial tension formed between the two polymer solutions causes cells to fall around the outside of the DEX droplet and form a circular clearing that can be used for migration assays. Cell islands can be patterned by dispensing a cell-rich DEX phase into a PEG solution or by covering the DEX droplet with a solution of PEG. Co-cultures can be formed directly by combining cell exclusion with DEX island patterning. These methods are compatible with a variety of liquid handling approaches, including manual micropipetting, and can be used with virtually any adherent cell type.

Aqueous two-phase systems were used to simultaneously pattern multiple populations of cells. This fast and easy method for cell patterning takes advantage of the phase separation of aqueous solutions of dextran and polyethylene glycol and the interfacial tension that exists between the two polymer solutions.

Cell patterning  technologies that are fast, easy to use and affordable will be required for the  future development of high throughput cell assays, ...

Transplantation of Induced Pluripotent Stem Cell-derived Mesoangioblast-like Myogenic Progenitors in Mouse Models of Muscle Regeneration

Patient-derived iPSCs could be an invaluable source of cells for future autologous cell therapy protocols. iPSC-derived myogenic stem/progenitor cells similar to pericyte-derived mesoangioblasts (iPSC-derived mesoangioblast-like stem/progenitor cells: IDEMs) can be established from iPSCs generated from patients affected by different forms of muscular dystrophy. Patient-specific IDEMs can be genetically corrected with different strategies (e.g. lentiviral vectors, human artificial chromosomes) and enhanced in their myogenic differentiation potential upon overexpression of the myogenesis regulator MyoD. This myogenic potential is then assessed in vitro with specific differentiation assays and analyzed by immunofluorescence. The regenerative potential of IDEMs is further evaluated in vivo, upon intramuscular and intra-arterial transplantation in two representative mouse models displaying acute and chronic muscle regeneration. The contribution of IDEMs to the host skeletal muscle is then confirmed by different functional tests in transplanted mice. In particular, the amelioration of the motor capacity of the animals is studied with treadmill tests. Cell engraftment and differentiation are then assessed by a number of histological and immunofluorescence assays on transplanted muscles. Overall, this paper describes the assays and tools currently utilized to evaluate the differentiation capacity of IDEMs, focusing on the transplantation methods and subsequent outcome measures to analyze the efficacy of cell transplantation.

Induced pluripotent stem cell (iPSC)-derived myogenic progenitors are promising candidates for cell therapy strategies to treat muscular dystrophies. This protocol describes transplantation and functional measurements required to evaluate the engraftment and differentiation of iPSC-derived mesoangioblasts (a type of muscle progenitors) in mouse models of acute and chronic muscle regeneration.

Patient-derived iPSCs could be an invaluable source of cells for future autologous cell therapy protocols. iPSC-derived myogenic stem/progenitor cells ...

Luminescence Resonance Energy Transfer to Study Conformational Changes in Membrane Proteins Expressed in Mammalian Cells

Luminescence Resonance Energy Transfer, or LRET, is a powerful technique used to measure distances between two sites in proteins within the distance range of 10-100 &#197;. By measuring the distances under various ligated conditions, conformational changes of the protein can be easily assessed. With LRET, a lanthanide, most often chelated terbium, is used as the donor fluorophore, affording advantages such as a longer donor-only emission lifetime, the flexibility to use multiple acceptor fluorophores, and the opportunity to detect sensitized acceptor emission as an easy way to measure energy transfer without the risk of also detecting donor-only signal. Here, we describe a method to use LRET on membrane proteins expressed and assayed on the surface of intact mammalian cells. We introduce a protease cleavage site between the LRET fluorophore pair. After obtaining the original LRET signal, cleavage at that site removes the specific LRET signal from the protein of interest allowing us to quantitatively subtract the background signal that remains after cleavage. This method allows for more physiologically relevant measurements to be made without the need for purification of protein.

We describe here an improved Luminescence Resonance Energy Transfer (LRET) method where we introduce a protease cleavage site between the donor and acceptor fluorophore sites. This modification allows us to obtain specific LRET signals arising from membrane proteins of interest, allowing for the study of membrane proteins without protein purification.

Luminescence Resonance Energy Transfer, or LRET, is a powerful technique used to measure distances between two sites in proteins within the distance range ...

Electrotaxis Studies of Lung Cancer Cells using a Multichannel Dual-electric-field Microfluidic Chip

The behavior of directional cell migration under a direct current electric-field (dcEF) is referred to as electrotaxis. The significant role of physiological dcEF in guiding cell movement during embryo development, cell differentiation, and wound healing has been demonstrated in many studies. By applying microfluidic chips to an electrotaxis assay, the investigation process is shortened and experimental errors are minimized. In recent years, microfluidic devices made of polymeric substances (e.g., polymethylmethacrylate, PMMA, or acrylic) or polydimethylsiloxane (PDMS) have been widely used in studying the responses of cells to electrical stimulation. However, unlike the numerous steps required to fabricate a PDMS device, the simple and rapid construction of the acrylic micro&#64258;uidic chip makes it suitable for both device prototyping and production. Yet none of the reported devices facilitate the efficient study of the simultaneous chemical and dcEF effects on cells. In this report, we describe our design and fabrication of an acrylic-based multichannel dual-electric-field (MDF) chip to investigate the concurrent effect of chemical and electrical stimulation on lung cancer cells. The MDF chip provides eight combinations of electrical/chemical stimulations in a single test. The chip not only greatly shortens the required experimental time but also increases accuracy in electrotaxis studies.

Many microfluidic devices have been developed for use in the study of electrotaxis. Yet, none of these chips allows the efficient study of the simultaneous chemical and electric-field (EF) effects on cells. We developed a polymethylmethacrylate-based device that offers better-controlled coexisting EF and chemical stimulation for use in electrotaxis research.

The behavior of directional cell migration under a direct current electric-field (dcEF) is referred to as electrotaxis. The significant role of ...

Aqueous Droplets Used as Enzymatic Microreactors and Their Electromagnetic Actuation

For the successful implementation of microfluidic reaction systems, such as PCR and electrophoresis, the movement of small liquid volumes is essential. In conventional lab-on-a-chip-platforms, solvents and samples are passed through defined microfluidic channels with complex flow control installations. The droplet actuation platform presented here is a promising alternative. With it, it is possible to move a liquid drop (microreactor) on a planar surface of a reaction platform (lab-in-a-drop). The actuation of microreactors on the hydrophobic surface of the platform is based on the use of magnetic forces acting on the outer shell of the liquid drops which is made of a thin layer of superhydrophobic magnetite particles. The hydrophobic surface of the platform is needed to avoid any contact between the liquid core and the surface to allow a smooth movement of the microreactor. On the platform, one or more microreactors with volumes of 10 &#181;L can be positioned and moved simultaneously. The platform itself consists of a 3 x 3 matrix of electrical double coils which accommodate either neodymium or iron cores. The magnetic field gradients are automatically controlled. By variation of the magnetic field gradients, the microreactors' magnetic hydrophobic shell can be manipulated automatically to move the microreactor or open the shell reversibly. Reactions of substrates and corresponding enzymes can be initiated by merging the microreactors or bringing them into contact with surface immobilized catalysts.

Lab-in-a-drop reaction systems allow the versatile implementation of complex reactions in a microfluidic scale. An automated actuation platform consisting of a 3 x 3 matrix of electromagnetic coils was developed and successfully used to merge two 10 &#181;L microreactors and thereby initiate an enzymatic reaction in the resulting liquid marbles.

For the successful implementation of microfluidic reaction systems, such as PCR and electrophoresis, the movement of small liquid volumes is essential. In ...

A Versatile Method of Patterning Proteins and Cells

Substrate and cell patterning techniques are widely used in cell biology to study cell-to-cell and cell-to-substrate interactions. Conventional patterning techniques work well only with simple shapes, small areas and selected bio-materials. This article describes a method to distribute cell suspensions as well as substrate solutions into complex, long, closed (dead-end) polydimethylsiloxane (PDMS) microchannels using negative pressure. This method enables researchers to pattern multiple substrates including fibronectin, collagen, antibodies (Sal-1), poly-D-lysine (PDL), and laminin. Patterning of substrates allows one to indirectly pattern a variety of cells. We have tested C2C12 myoblasts, the PC12 neuronal cell line, embryonic rat cortical neurons, and amphibian retinal neurons. In addition, we demonstrate that this technique can directly pattern fibroblasts in microfluidic channels via brief application of a low vacuum on cell suspensions. The low vacuum does not significantly decrease cell viability as shown by cell viability assays. Modifications are discussed for application of the method to different cell and substrate types. This technique allows researchers to pattern cells and proteins in specific patterns without the need for exotic materials or equipment and can be done in any laboratory with a vacuum.

This report describes a simple, easy to perform technique, using low pressure vacuum, to fill microfluidic channels with cells and substrates for biological research.

Substrate and cell patterning techniques are widely used in cell biology to study cell-to-cell and cell-to-substrate interactions. Conventional patterning ...