Name: regeneration of arrayed gold microelectrodes equipped for a real-time cell analyzer
Uploaded: 2018-03-12T12:30:00
Description: Watch this Scientific Journal Video about Regeneration of Arrayed Gold Microelectrodes Equipped for a Real-Time Cell Analyzer at JoVE.com

The work was supported by National Natural Science Foundation of China (U1703118), a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), Jiangsu Shuangchuang Program, Open Funds of the State Key Laboratory for Chemo/Biosensing and Chemometrics (2016015) and the National Laboratory of Biomacromolecules (2017kf05) and Jiangsu Specially-Appointed Professor project, China.

NOTE: In general, the regeneration process includes trypsin digestion and rinsing step with ethanol and water. The digestion time changes according to the number of cells used, and the type and number of cells used may differ depending on the experimental purposes. It is advised to check the regenerated microchips using optical and electrochemical methods to optimize the regeneration conditions. During the experiment, soluble and insoluble chemicals may be involved, and here these two typical cases of the regeneration pr...

<ol>
	<li>Michaelis, S., Wegener, J., Robelek, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Label-free+monitoring+of+cell-based+assays:+Combining+impedance+analysis+with+SPR+for+multiparametric+cell+profiling.">Label-free monitoring of cell-based assays: Combining impedance analysis with SPR for multiparametric cell profiling.</a> Biosens. Bioelectron. 49, 63-70 (2013).</li><li>Hillger, J. 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=Whole-cell+biosensor+for+label-free+detection+of+GPCR-mediated+drug+responses+in+personal+cell+lines.">Whole-cell biosensor for label-free detection of GPCR-mediated drug responses in personal cell lines.</a> Biosens. Bioelectron. 74, 233-242 (2015).</li><li>Atienzar, F. A., 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=The+use+of+real-time+cell+analyzer+technology+in+drug+discovery:+defining+optimal+cell+culture+conditions+and+assay+reproducibility+with+different+adherent+cellular+models.">The use of real-time cell analyzer technology in drug discovery: defining optimal cell culture conditions and assay reproducibility with different adherent cellular models.</a> J. Biomol. Screen. 16 (6), 575-587 (2011).</li><li>Chen, H., 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=Label-free+luminescent+mesoporous+silica+nanoparticles+for+imaging+and+drug+delivery.">Label-free luminescent mesoporous silica nanoparticles for imaging and drug delivery.</a> Theranostics. 3 (9), 650-657 (2013).</li><li>Gao, Z., 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=Silicon+Nanowire+Arrays+for+Label-Free+Detection+of+DNA.">Silicon Nanowire Arrays for Label-Free Detection of DNA.</a> Anal. Chem. 79 (9), 3291-3297 (2007).</li><li>Giaever, I., Keese, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+morphological+biosensor+for+mammalian+cells.">A morphological biosensor for mammalian cells.</a> Nature. 366 (6455), 591-592 (1993).</li><li>Xiao, C., Lachance, B., Sunahara, G., Luong, J. H. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+cytotoxicity+using+electric+cell-substrate+impedance+sensing:+concentration+and+time+response+function+approach.">Assessment of cytotoxicity using electric cell-substrate impedance sensing: concentration and time response function approach.</a> Anal. Chem. 74 (22), 5748-5753 (2002).</li><li>Xiao, C., Lachance, B., Sunahara, G., Luong, J. H. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+in-depth+analysis+of+electric+cell-substrate+impedance+sensing+to+study+the+attachment+and+spreading+of+mammalian+cells.">An in-depth analysis of electric cell-substrate impedance sensing to study the attachment and spreading of mammalian cells.</a> Anal. Chem. 74 (6), 1333-1339 (2002).</li><li>Xing, J. Z., 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=Dynamic+monitoring+of+cytotoxicity+on+microelectronic+sensors.">Dynamic monitoring of cytotoxicity on microelectronic sensors.</a> Chem. Res. Toxicol. 18 (2), 154-161 (2005).</li><li>Abassi, Y. A., 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=Kinetic+cell-based+morphological+screening:+prediction+of+mechanism+of+compound+action+and+off-target+effects.">Kinetic cell-based morphological screening: prediction of mechanism of compound action and off-target effects.</a> Chem. Biol. 16 (7), 712-723 (2009).</li><li>Urcan, E., 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=Real-time+xCELLigence+impedance+analysis+of+the+cytotoxicity+of+dental+composite+components+on+human+gingival+fibroblasts.">Real-time xCELLigence impedance analysis of the cytotoxicity of dental composite components on human gingival fibroblasts.</a> Dent. Mater. 26 (1), 51-58 (2010).</li><li>Atienza, J. M., Zhu, J., Wang, X., Xu, X., Abassi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+monitoring+of+cell+adhesion+and+spreading+on+microelectronic+sensor+arrays.">Dynamic monitoring of cell adhesion and spreading on microelectronic sensor arrays.</a> J. Biomol. Screen. 10 (8), 795-805 (2005).</li><li>Rahim, S., Uren, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Real-time+Electrical+Impedance+Based+Technique+to+Measure+Invasion+of+Endothelial+Cell+Monolayer+by+Cancer+Cells.">A Real-time Electrical Impedance Based Technique to Measure Invasion of Endothelial Cell Monolayer by Cancer Cells.</a> J. Vis. Exp. (50), e2792 (2011).</li><li>Moodley, K., Angel, C. E., Glass, M., Graham, E. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+profiling+of+NK+cell+killing+of+human+astrocytes+using+xCELLigence+technology.">Real-time profiling of NK cell killing of human astrocytes using xCELLigence technology.</a> J. Neurosci. Meth. 200 (2), 173-180 (2011).</li><li>Marinova, Z., Walitza, S., Grunblatt, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+impedance-based+cell+analyzer+as+a+tool+to+delineate+molecular+pathways+involved+in+neurotoxicity+and+neuroprotection+in+a+neuronal+cell+line.">Real-time impedance-based cell analyzer as a tool to delineate molecular pathways involved in neurotoxicity and neuroprotection in a neuronal cell line.</a> J. Vis. Exp. (90), e51748 (2014).</li><li>Chatelier, R. C., Gengenbach, T. R., Griesser, H. J., Brighamburke, M., Oshannessy, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+general+method+to+recondition+and+reuse+Biacore+sensor+chips+fouled+with+covalently+immobilized+protein/peptide.">A general method to recondition and reuse Biacore sensor chips fouled with covalently immobilized protein/peptide.</a> Anal. Biochem. 229 (1), 112-118 (1995).</li><li>Vashist, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+regenerating+gold+surface+for+prolonged+reuse+of+gold-coated+surface+plasmon+resonance+chip.">A method for regenerating gold surface for prolonged reuse of gold-coated surface plasmon resonance chip.</a> Anal. Biochem. 423 (1), 23-25 (2012).</li><li>Nguyen, T. T., 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=A+regenerative+label-free+fiber+optic+sensor+using+surface+plasmon+resonance+for+clinical+diagnosis+of+fibrinogen.">A regenerative label-free fiber optic sensor using surface plasmon resonance for clinical diagnosis of fibrinogen.</a> Int. J. Nanomed. 10, 155-163 (2015).</li><li>Xu, Z., 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=A+general+method+to+regenerate+arrayed+gold+microelectrodes+for+label-free+cell+assay.">A general method to regenerate arrayed gold microelectrodes for label-free cell assay.</a> Anal. Biochem. 516, 57-60 (2017).</li><li>Wang, H., 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=Three-dimensionally+controllable+synthesis+of+multichannel+silica+nanotubes+and+their+application+as+dual+drug+carriers.">Three-dimensionally controllable synthesis of multichannel silica nanotubes and their application as dual drug carriers.</a> ChemPlusChem. 80 (11), 1615-1623 (2015).</li><li>Verrier, S., Notingher, I., Polak, J. M., Hench, L. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+monitoring+of+cell+death+using+Raman+microspectroscopy.">In situ monitoring of cell death using Raman microspectroscopy.</a> Biopolymers. 74 (1-2), 157-162 (2004).</li><li>Keighley, S. D., Li, P., Estrela, P., Migliorato, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+DNA+immobilization+on+gold+electrodes+for+label-free+detection+by+electrochemical+impedance+spectroscopy.">Optimization of DNA immobilization on gold electrodes for label-free detection by electrochemical impedance spectroscopy.</a> Biosens. Bioelectron. 23 (8), 1291-1297 (2008).</li><li>Kandimalla, V. B., 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=Regeneration+of+ethyl+parathion+antibodies+for+repeated+use+in+immunosensor:+a+study+on+dissociation+of+antigens+from+antibodies.">Regeneration of ethyl parathion antibodies for repeated use in immunosensor: a study on dissociation of antigens from antibodies.</a> Biosens. Bioelectron. 20 (4), 903-906 (2004).</li><li>McGovern, J. P., Shih, W. Y., Shih, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+detection+of+Bacillus+anthracis+spores+using+fully+submersible,+self-exciting,+self-sensing+PMN-PT/Sn+piezoelectric+microcantilevers.">In situ detection of Bacillus anthracis spores using fully submersible, self-exciting, self-sensing PMN-PT/Sn piezoelectric microcantilevers.</a> Analyst. 132 (8), 777-783 (2007).</li><li>Loo, L., 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=A+rapid+method+to+regenerate+piezoelectric+microcantilever+sensors+(PEMS).">A rapid method to regenerate piezoelectric microcantilever sensors (PEMS).</a> Sensors. 11 (5), 5520-5528 (2011).</li><li>Fischer, L. 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=Gold+cleaning+methods+for+electrochemical+detection+applications.">Gold cleaning methods for electrochemical detection applications.</a> Microelectron. Eng. 86 (4-6), 1282-1285 (2009).</li></ol>

We summarized several available methods17,23,24,25,26 for regenerating microchips in Table 1. Basically, these methods involved relatively harsh experimental conditions to achieve the complete regeneration of chips because of the presence of strong molecule-molecule interactions such as that of the immune complex used for SPR chips. However, t...

Owing to its efficient and less labor-intensive experimental process, label-free cell-based technology has witnessed rapid growth over the past decade for analytical as well as screening purposes such as in the aspect of proteomics1,2, drug delivery3, etc.4,5 Compared with traditional biochemical methods aimed at cell analysis, label-free real-time cell assay with the prototype developed by Giaever and coworkers previously6 is based on the principle of recording electric signal changes on the surface of cell-attached microchips, which permit a continuous measurement of cell growth or migration in a quantitative manner. Following this strategy, a real-time cell electronic sensing (RT-CES) system using electric impedance-based detection principle was introduced7,8 and more recently a commercial real-time cell analyzer (RTCA) was launched for laboratory research9.
The commercial real-time cell analyzer mainly reads out the cells&#39; evoked signals of electric impedance, which result from the physiological changes of incubated cells including cell proliferation, migration, viability, morphology, and adherence on the surface of microchips10,11. Such electric signals are further converted by the analyzer into a dimensionless parameter named the Cell Index (CI) to assess the cell status. The change of the impedance of microchips mainly reflects the local ionic environment of covered cells at the electrode/solution interface. Therefore, the analytical performance of the cell analyzer relies heavily on the core sensing unit, the disposable microchips (i.e., so-called electronic plates, e.g., 96/16/8-well), which are made of arrayed gold microelectrodes lithographically printed at the bottom of incubation wells. The gold microelectrodes assemble in a circle-on-line format (Figure 1) and cover most of the surface area of the incubation wells, which allow for dynamic and sensitive detection of attached cells3,12,13,14. The CI will increase in the case of more surface coverage of cells on the chip, and decrease when cells are exposed to a toxicant resulting in apoptosis. Although the real-time cell analyzer has been frequently used to determine cytotoxicity11 and neurotoxicity15 and provide more kinetic information than classical endpoints method, the disposable electronic plates are the costliest consumable.
Until now, there have been no available methods for the regeneration of the electronic plate, which is probably due to the fact that harsh regeneration conditions, such as piranha solution or acetic acid are involved16,17,18, which may alter the electric status of gold microchips. Therefore, a mild and efficient method to remove the adherent cells and other substances from the surface of gold chips will be desirable for the electronic plate regeneration process. We have recently developed a protocol aimed at the regeneration of disposable electronic plates using non-corrosive reagents and the regenerated chips were characterized by electrochemical as well as optical methods19. By using readily available and moderate laboratory reagents including trypsin and ethanol, we have established a general method to regenerate the commercial electronic plate without adverse effects, which is successfully applied to regenerate the two main types of electronic plate (both 16 and L8) used for RTCA.

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			<td style="width:317px;">Southern Biotech</td>
			<td style="width:263px;">Cat# 0100-20&#160;</td>
			<td style="width:192px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">Poly-D-Lysine&#160;</td>
			<td style="width:317px;">Sigma</td>
			<td style="width:263px;">Cat# A-003-E</td>
			<td style="width:192px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">Primaria Plates&#160;</td>
			<td style="width:317px;">VWR</td>
			<td style="width:263px;">Cat# 62406-456</td>
			<td style="width:192px;"></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:293px;">Stock reagents&#160;</td>
			<td style="width:317px;">reconstitution&#160;</td>
			<td style="width:263px;">Concentration used</td>
			<td style="width:192px;">Storage</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">Apo-transferrin</td>
			<td style="width:317px;">10 mg/mL in PBS&#160;</td>
			<td style="width:263px;">1:100</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:293px;">N-acetyl cysteine</td>
			<td style="width:317px;">5 mg/mL in H2O&#160;</td>
			<td style="width:263px;">1:1,000</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:293px;">Sodium selenite</td>
			<td style="width:317px;">2.5 mg/mL in H2O&#160;</td>
			<td style="width:263px;">1:25,000</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">Collagen IV</td>
			<td style="width:317px;">200 &#956;g/mL in PBS&#160;</td>
			<td style="width:263px;">1:100</td>
			<td>-80&#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">TGF-b2</td>
			<td style="width:317px;">20 &#956;g/mL in PBS&#160;</td>
			<td style="width:263px;">1:10,000</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">IL-34</td>
			<td style="width:317px;">100 &#956;g/mL in PBS&#160;</td>
			<td style="width:263px;">1:1,000</td>
			<td>-80&#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">Ovine wool cholesterol</td>
			<td style="width:317px;">1.5 mg/mL in 100% ethanol&#160;</td>
			<td style="width:263px;">1:1,000</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:293px;">Heparan sulfate</td>
			<td style="width:317px;">1 mg/mL in H2O</td>
			<td style="width:263px;">1:1,000</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:293px;">Oleic acid/Gondoic acid</td>
			<td style="width:317px;">Gondoic: 0.001 mg/mL; Oleic: 0.1 mg/mL in 100% ethanol&#160;</td>
			<td style="width:263px;">1:1,000</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">Heparin</td>
			<td style="width:317px;">50 mg/mL in PBS&#160;</td>
			<td style="width:263px;">1:100</td>
			<td>-20&#176;C</td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:293px;">Solutions&#160;</td>
			<td style="width:317px;">Recipe&#160;</td>
			<td style="width:263px;"></td>
			<td style="width:192px;">Comments</td>
		</tr>
		<tr height="48">
			<td height="48" style="height:48px;">Perfusion Buffer</td>
			<td style="width:317px;">50 &#956;g/mL heparin in DPBS++ (PBS with Ca++ and Mg+ +)</td>
			<td style="width:263px;"></td>
			<td style="width:192px;">Use when ice-cold</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Douncing Buffer</td>
			<td style="width:317px;">200 &#956;L of 0.4% DNaseI in 50 mL of DPBS++</td>
			<td style="width:263px;"></td>
			<td style="width:192px;">Use when ice-cold</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">Panning Buffer</td>
			<td style="width:317px;">2 mg/mL of peptone from milk solids in DPBS++</td>
			<td style="width:263px;"></td>
			<td style="width:192px;"></td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;">Microglia Growth Medium (MGM)</td>
			<td style="width:317px;">DMEM/F12 containing 100 units/mL penicillin, 100 &#956;g/mL streptomycin, 2 mM glutamine, 5 &#956;g/mL N-acetyl cysteine, 5 &#956;g/mL insulin, 100 &#956;g/mL apo-transferrin, and 100 ng/mL sodium selenite</td>
			<td style="width:263px;"></td>
			<td style="width:192px;">Use ice-cold MGM to pan microglia off of immnopanning dish.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Collagen IV Coating</td>
			<td style="width:317px;">MGM containing 2 &#956;g/mL collagen IV</td>
			<td style="width:263px;"></td>
			<td style="width:192px;"></td>
		</tr>
		<tr height="50">
			<td height="50" style="height:50px;">Myelin Seperation Buffer</td>
			<td style="width:317px;">9 mL Percoll PLUS, 1 mL 10x PBS without Ca++ and Mg++, 9 &#956;L 1 M CaCl2, 5 &#956;L 1 M MgCl2</td>
			<td style="width:263px;"></td>
			<td style="width:192px;">Mix well after the addition of&#160; CaCl2 and MgCl2</td>
		</tr>
		<tr height="235">
			<td height="235" style="height:235px;width:293px;">TGF-b2/IL-34/Cholesterol containing growth media (TIC)&#160;</td>
			<td style="width:317px;">MGM containing human 2 ng/mL TGF-b2, 100 ng/mL murine IL-34, 1.5 &#956;g/mL ovine wool cholesterol, 10 &#956;g/mL heparan sulfate, 0.1 &#956;g/ml oleic acid, and 0.001 &#956;g/ml gondoic acid</td>
			<td style="width:263px;"></td>
			<td style="width:192px;">Make sure to add cholesterol to media warmed to 37 &#176;C and do not add more than 1.5 &#956;g/mL or it will precipitate out. Do not filter cholesterol-containing media. Equilibrate TIC media with 10% CO2 for 30 min- 1 hr before adding to cells to insure optimal pH.&#160;</td>
		</tr>
	</tbody>
</table>

regeneration of arrayed gold microelectrodes equipped for a real-time cell analyzer

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability to provide more dynamic information about cells under physiological conditions than classical biochemical assays, this label-free real-time cell assay based on the electric impedance principle is attracting more attention during the past decade. However, its practical utilization may be limited due to the relatively expensive cost of measurement, in which costly consumable disposable gold microchips are used for the cell analyzer. In this protocol, we have developed a general strategy to regenerate arrayed gold microelectrodes equipped for a commercial label-free cell analyzer. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step. The proposed method has been tested and shown to be effective for the regeneration and repeated usage of commercial electronic plates at least three times, which will help researchers save on the high running cost of real-time cell assays.

Surface properties of gold microchips: The regeneration procedures used in this protocol were outlined in Figure 1. Figure 2 shows the microscopic surface pictures of fresh and regenerated electronic plates by the optical microscope. As shown in Figure 2A and Figure 2C, microscopic observations indicated that there was virtually no diffe...

Watch this Scientific Journal Video about Regeneration of Arrayed Gold Microelectrodes Equipped for a Real-Time Cell Analyzer at JoVE.com

Regeneration of Arrayed Gold Microelectrodes Equipped for a Real-Time Cell Analyzer

This protocol describes a general strategy to regenerate commercial arrayed gold microelectrodes equipped for a label-free cell analyzer aimed at saving on the high running costs ofmicrochip-based assays. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step, which enables repeated usage of microchips.

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability ...

The overall goal of this procedure is to regenerate commercial electronic plates equipped for a Real-Time Cell Analyzer, or RTCA. This method can help answer key questions in the regeneration of disposable gold-based chips field, including the regeneration of electronic plans used in RTCA. The main advantage of this technique is that the regeneration procedure can be conducted using mild and readily available lab reagents with low toxicity.We first had the idea for this method when we started to use the Real-Time Cell Analyzer which the cost gold-based chips. Begin this procedure with incubation and proliferation of A549 cells in cell-culture dish as described in the text protocol. Add 150 microliters of cell medium to each incubation well of the electronic plate L8.Leave the plate for 30 minutes in the bio-safety hood for equilibration.After 30 minutes, manually insert the electronic plate L8 in the Real-Time Cell Analyzer in the CO2 incubator at 37 degrees Celsius. Next, launch the Real-Time Cell Analyzer operation program on the computer. On the default experiment pattern setup page, select Experiment Model, and name the running assay.On its layout page, select the corresponding wells that are included in the experiment, and input the information such as cell type, number, and drug names in the edit boxes. On its schedule page, add the experimental steps, then select the running time of each step and interval of realtime data acquisition. Click start to measure the background impedance of the media.The experiment file will be saved. The resulting data will be automatically subtracted. On the plot page, add wells, and the graph of time-cell index will be showed.For the cell-proliferation experiment, first click the pause button to pause the program. Then take out the electronic plate, and add 100 microliters of A549 cell suspension buffer per well at room temperature. Leave the plate for 30 minutes in the bio-safety hood to let the cells settle to the bottom of incubation wells.Manually insert the electronic plate in the realtime cell-analyzer station. Then click the start button to continue the experiment. On the plot page, the analyzer continuously records cell index values, or curves, throughout the experiment.When the experiment is complete, enter the plot page, and open the experiment file. Then select all the tested incubation wells and the resulting cell index curves that can be averaged or normalized for the last time before adding pharmaceutical drugs or changing medium to reduce variations between assays. On the data-analysis page, EC50 or IC50 can be calculated.After performing cytotoxicity evaluation of anticancer drug as described in the text protocol, take out the electronic plate containing cells from the Real-Time Cell Analyzer station. Place the used electronic plate in a sterile bio-safety hood at room temperature, and mix the culture medium thoroughly using a pipette. Then use a pipette to aspirate the entire medium.Rinse the electronic plates with 200 microliters of deionized water for three times at room temperature. Digest the remaining cells on the electronic plates with 0.25%freshly-prepared trypsin for one to two hours in an incubator at 37 degrees Celsius. When the digestion is completed, work in the bio-safety hood at room temperature to mix the incubation solution five to 10 times using a pipette, and then remove the solution.Rinse the electronic plates with 200 microliters of deionized water two times. Then wash with 200 microliters of 100%ethanol two times, followed by the same volume of 75%ethanol two times. Finally, rinse with another 200 microliters of deionized water two times.Invert the electronic plate on a sterile gauze or tissue paper to decant the remaining water at room temperature. Then perform ultraviolet sterilization on the regenerated electronic plate for one to two hours in the bio-safety hood at room temperature. After using the plates for drug delivery using mesoporous material as described in the text protocol, digest the remaining cells with trypsin as before.As the pipette is frequently used in the experiments, attention should be taken by the person to avoid scratching of the tip and the surface of the microchips. Rinse the microchips with 200 microliters of deionized water once in the bio-safety hood at room temperature. Then rise the microchips with 200 microliters of absolute ethanol two times at room temperature.Next, rinse the microchips with 200 microliters of 75%ethanol once at room temperature. Add 250 microliters of 75%ethanol in each well, and seal the electronic plate with the sealing film at room temperature. After spinning the electronic plate at 114 times G for two minutes, empty the plate.Invert the electronic plate on a sterile gauze or tissue paper to decant the remaining liquid at room temperature. Repeat the 75%ethanol rinses followed by the spin. Then perform ultraviolet sterilization on the regenerated electronic plate for one to two hours in the bio-safety hood at room temperature.Assess optical characteristics of the regenerated electronic-plate surface by first disassembling the bottom part of the incubation well as described in the text protocol. To evaluate the viability of attached cells after anticancer-drug uptake on the fresh and regenerated electronic plates, use a confocal laser-scanning microscope to monitor the spontaneous fluorescence of DOX molecules absorbed by A549 cells. To record the spontaneous fluorescence of absorbed DOX by the cells, use a 63-times oil objective and 485 nanometers as the excitation wavelength.Next, assess the electrochemical behaviors of regenerated electrodes by first polishing the gold electrode and the glassy carbon electrode to a mirror-like surface with an illuminoslurry on a polishing cloth. Then sonicate the electrodes in water to remove any particles. Next, activate the gold electrode in 0.5-molar sulfuric acid.Obtain Electrochemical Impedance Spectroscopy, or EIS data, of the bare gold electrode and the glassy carbon electrode in 10-millimolar potassium-chloride-electrolyte solution, containing one millimolar potassium pheracyanide. Now, drop 10 microliters of a cell suspension on the surface of the gold electrode in the GCE. After adding the cells, incubate the gold electrode in the GCE in a 37-degree-Celsius incubator for three hours before obtaining EIS data of the electrodes modified with cells, as described in the text protocol.To regenerate the electrodes, immerse the gold electrode in the GCE modified with cells in 0.25%trypsin for 0.5 to two hours. Rinse both electrodes softly with water four times. Then, rinse the electrodes softly with absolute ethanol four times.Next, immerse the gold electrode in the GCE in 75%ethanol for approximately five minutes. After five minutes, rinse the chip softly with 75%ethanol four times before obtaining EIS data of the regenerated electrodes, as described in the text protocol. To evaluate the regeneration efficiency of the arrayed gold electronic plate, microscopic observations were made for both fresh and treated electronic plates.No virtual difference in the optical properties of microchip surface was found. Throescence of doxorubicin molecules is used to assess the cell status on the gold microchips before and after regeneration. The similar homogeneity and well-defined cellular morphology demonstrated the reusability of the chips.The regeneration protocol is applied for the real test of cell proliferation. The growth curves obtained from multiple incubation wells of a tested electronic plate show good consistency, indicating the successful regeneration of the commercial chip. Shown here, the regenerated electronic plate L8 was tested for cytotoxicity evaluation using mesoporous silica materials.The cell index of the mesoporous-materials-treated sample decreased as compared with the control, indicating a slight cytotoxicity of the materials. Further encapsulation and release of the anticancer drug doxorubicin by mesoporous materials caused a dramatic decrease in the growth curve of A549 cells. Once mastered, this technique can be done in four hours if it is performed properly.While attempting this procedure it is important to remember that the type sink digestion time may differ from chip to chip. Following this procedure, other method like confocal laser-scanning microscopy, or even spectroscopy, electrochemical impedance spectroscopy can be performed in order to answer additional questions like assessment of the regeneration effect.

regeneration-arrayed-gold-microelectrodes-equipped-for-real-time-cell

Research

JoVE Journal

Biochemistry

Highly Sensitive and Rapid Fluorescence Detection with a Portable FRET Analyzer

Recent improvements in F&#246;rster resonance energy transfer (FRET) sensors have enabled their use to detect various small molecules including ions and amino acids. However, the innate weak signal intensity of FRET sensors is a major challenge that prevents their application in various fields and makes the use of expensive, high-end fluorometers necessary. Previously, we built a cost-effective, high-performance FRET analyzer that can specifically measure the ratio of two emission wavelength bands (530 and 480 nm) to achieve high detection sensitivity. More recently, it was discovered that FRET sensors with bacterial periplasmic binding proteins detect ligands with maximum sensitivity in the critical temperature range of 50 - 55 &#176;C. This report describes a protocol for assessing sugar content in commercially-available beverage samples using our portable FRET analyzer with a temperature-specific FRET sensor. Our results showed that the additional preheating process of the FRET sensor significantly increases the FRET ratio signal, to enable more accurate measurement of sugar content. The custom-made FRET analyzer and sensor were successfully applied to quantify the sugar content in three types of commercial beverages. We anticipate that further size reduction and performance enhancement of the equipment will facilitate the use of hand-held analyzers in environments where high-end equipment is not available.

This protocol describes the rapid and highly sensitive quantification of F&#246;rster resonance energy transfer (FRET) sensor data using a custom-made portable FRET analyzer. The device was used to detect maltose within a critical temperature range that maximizes detection sensitivity, enabling practical and efficient assessment of sugar content.

Recent improvements in F&#246;rster resonance energy transfer (FRET) sensors have enabled their use to detect various small molecules including ions and ...

A Protein Preparation Method for the High-throughput Identification of Proteins Interacting with a Nuclear Cofactor Using LC-MS/MS Analysis

Transcriptional coregulators are vital to the efficient transcriptional regulation of nuclear chromatin structure. Coregulators play a variety of roles in regulating transcription. These include the direct interaction with transcription factors, the covalent modification of histones and other proteins, and the occasional chromatin conformation alteration. Accordingly, establishing relatively quick methods for identifying proteins that interact within this network is crucial to enhancing our understanding of the underlying regulatory mechanisms. LC-MS/MS-mediated protein binding partner identification is a validated technique used to analyze protein-protein interactions. By immunoprecipitating a previously-identified member of a protein complex with an antibody (occasionally with an antibody for a tagged protein), it is possible to identify its unknown protein interactions via mass spectrometry analysis. Here, we present a method of protein preparation for the LC-MS/MS-mediated high-throughput identification of protein interactions involving nuclear cofactors and their binding partners. This method allows for a better understanding of the transcriptional regulatory mechanisms of the targeted nuclear factors.

We have established a method for the purification of coregulatory interaction proteins using the LC-MS/MS system.

Transcriptional coregulators are vital to the efficient transcriptional regulation of nuclear chromatin structure. Coregulators play a variety of roles in ...

Real-time Tracking of DNA Fragment Separation by Smartphone

Slab gel electrophoresis (SGE) is the most common method for the separation of DNA fragments; thus, it is broadly applied to the field of biology and others. However, the traditional SGE protocol is quite tedious, and the experiment takes a long time. Moreover, the chemical consumption in SGE experiments is very high. This work proposes a simple method for the separation of DNA fragments based on an SGE chip. The chip is made by an engraving machine. Two plastic sheets are used for the excitation and emission wavelengths of the optical signal. The fluorescence signal of the DNA bands is collected by smartphone. To validate this method, 50, 100, and 1,000 bp DNA ladders were separated. The results demonstrate that a DNA ladder smaller than 5,000 bp can be resolved within 12 min and with high resolution when using this method, indicating that it is an ideal substitute for the traditional SGE method.

Traditional slab gel electrophoresis (SGE) experiments require a complicated apparatus and high chemical consumption. This work presents a protocol that describes a low-cost method to separate DNA fragments within a short timeframe.

Slab gel electrophoresis (SGE) is the most common method for the separation of DNA fragments; thus, it is broadly applied to the field of biology and ...

A Fluorescence Fluctuation Spectroscopy Assay of Protein-Protein Interactions at Cell-Cell Contacts

A variety of biological processes involves cell-cell interactions, typically mediated by proteins that interact at the interface between neighboring cells. Of interest, only few assays are capable of specifically probing such interactions directly in living cells. Here, we present an assay to measure the binding of proteins expressed at the surfaces of neighboring cells, at cell-cell contacts. This assay consists of two steps: mixing of cells expressing the proteins of interest fused to different fluorescent proteins, followed by fluorescence fluctuation spectroscopy measurements at cell-cell contacts using a confocal laser scanning microscope. We demonstrate the feasibility of this assay in a biologically relevant context by measuring the interactions of the amyloid precursor-like protein 1 (APLP1) across cell-cell junctions. We provide detailed protocols on the data acquisition using fluorescence-based techniques (scanning fluorescence cross-correlation spectroscopy, cross-correlation number and brightness analysis) and the required instrument calibrations. Further, we discuss critical steps in the data analysis and how to identify and correct external, spurious signal variations, such as those due to photobleaching or cell movement.
In general, the presented assay is applicable to any homo- or heterotypic protein-protein interaction at cell-cell contacts, between cells of the same or different types and can be implemented on a commercial confocal laser scanning microscope. An important requirement is the stability of the system, which needs to be sufficient to probe diffusive dynamics of the proteins of interest over several minutes.

This protocol describes a fluorescence fluctuation spectroscopy-based approach to investigate interactions among proteins mediating cell-cell interactions, i.e. proteins localized in cell junctions, directly in living cells. We provide detailed guidelines on instrument calibration, data acquisition and analysis, including corrections to possible artefact sources.

A variety of biological processes involves cell-cell interactions, typically mediated by proteins that interact at the interface between neighboring ...

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51

The DNA strand exchange reaction mediated by Rad51 is a critical step of homologous recombination. In this reaction, Rad51 forms a nucleoprotein filament on single-stranded DNA (ssDNA) and captures double-stranded DNA (dsDNA) non-specifically to interrogate it for a homologous sequence. After encountering homology, Rad51 catalyzes DNA strand exchange to mediate pairing of the ssDNA with the complementary strand of the dsDNA. This reaction is highly regulated by numerous accessary proteins in vivo. Although conventional biochemical assays have been successfully employed to examine the role of such accessory protein in vitro, kinetic analysis of intermediate formation and its progression into a final product has proven challenging due to the unstable and transient nature of the reaction intermediates. To observe these reaction steps directly in solution, fluorescence resonance energy transfer (FRET)-based real-time observation systems of this reaction were established. Kinetic analysis of real-time observations shows that the DNA strand exchange reaction mediated by Rad51 obeys a three-step reaction model involving the formation of a three-strand DNA intermediate, maturation of this intermediate, and the release of ssDNA from the mature intermediate. The Swi5-Sfr1 complex, an accessary protein conserved in eukaryotes, strongly enhances the second and third steps of this reaction. The FRET-based assays presented here enable us to uncover the molecular mechanisms through which recombination accessary proteins stimulate the DNA strand exchange activity of Rad51. The primary goal of this protocol is to enhance the repertoire of techniques available to researchers in the field of homologous recombination, particularly those working with proteins from species other than Schizosaccharomyces pombe, so that the evolutionary conservation of the findings presented herein can be determined.

Fluorescence resonance energy transfer-based real-time observation systems of the DNA strand exchange reaction mediated by Rad51 were developed. Using the protocols presented here, we are able to detect the formation of reaction intermediates and their conversion into products, while also analyzing the enzymatic kinetics of the reaction.

The DNA strand exchange reaction mediated by Rad51 is a critical step of homologous recombination. In this reaction, Rad51 forms a nucleoprotein filament ...

Real-Time, Semi-Automated Fluorescent Measurement of the Airway Surface Liquid pH of Primary Human Airway Epithelial Cells

In recent years, the importance of mucosal surface pH in the airways has been highlighted by its ability to regulate airway surface liquid (ASL) hydration, mucus viscosity and activity of antimicrobial peptides, key parameters involved in innate defense of the lungs. This is of primary relevance in the field of chronic respiratory diseases such as cystic fibrosis (CF) where these parameters are dysregulated. While different groups have studied ASL pH both in vivo and in vitro, their methods report a relatively wide range of ASL pH values and even contradictory findings regarding any pH differences between non-CF and CF cells. Furthermore, their protocols do not always provide enough details in order to ensure reproducibility, most are low throughput and require expensive equipment or specialized knowledge to implement, making them difficult to establish in most labs. Here we describe a semi-automated fluorescent plate reader assay that enables the real-time measurement of ASL pH under thin film conditions that more closely resemble the in vivo situation. This technique allows for stable measurements for many hours from multiple airway cultures simultaneously and, importantly, dynamic changes in ASL pH in response to agonists and inhibitors can be monitored. To achieve this, the ASL of fully differentiated primary human airway epithelial cells (hAECs) are stained overnight with a pH-sensitive dye in order to allow for the reabsorption of the excess fluid to ensure thin film conditions. After fluorescence is monitored in the presence or absence of agonists, pH calibration is performed in situ to correct for volume and dye concentration. The method described provides the required controls to make stable and reproducible ASL pH measurements, which ultimately could be used as a drug discovery platform for personalized medicine, as well as adapted to other epithelial tissues and experimental conditions, such as inflammatory and/or host-pathogen models.

We present a protocol to make dynamic measurements of the airway surface liquid pH under thin film conditions using a plate-reader.

In recent years, the importance of mucosal surface pH in the airways has been highlighted by its ability to regulate airway surface liquid (ASL) ...

Monitoring GPCR-&#946;-arrestin1/2 Interactions in Real Time Living Systems to Accelerate Drug Discovery

Interactions between G-protein coupled receptors (GPCRs) and &#946;-arrestins are vital processes with physiological implications of great importance. Currently, the characterization of novel drugs towards their interactions with &#946;-arrestins and other cytosolic proteins is extremely valuable in the field of GPCR drug discovery particularly during the study of GPCR biased agonism. Here, we show the application of a novel structural complementation assay to accurately monitor receptor-&#946;-arrestin interactions in real time living systems. This method is simple, accurate and can be easily extended to any GPCR of interest and also it has the advantage that it overcomes unspecific interactions due to the presence of a low expression promoter present in each vector system. This structural complementation assay provides key features that allow an accurate and precise monitoring of receptor-&#946;-arrestin interactions, making it suitable in the study of biased agonism of any GPCR system as well as GPCR c-terminus &#8216;phosphorylation codes&#8217; written by different GPCR-kinases (GRKs) and post-translational modifications of arrestins that stabilize or destabilize the receptor-&#946;-arrestin complex.

GPCR-&#946;-arrestin interactions are an emerging field in GPCR drug discovery. Accurate, precise and easy to set up methods are necessary to monitor such interactions in living systems. We show a structural complementation assay to monitor GPCR-&#946;-arrestin interactions in real time living cells, and it can be extended to any GPCR.

Interactions between G-protein coupled receptors (GPCRs) and &#946;-arrestins are vital processes with physiological implications of great importance. ...

Using an Extracellular Flux Analyzer to Measure Changes in Glycolysis and Oxidative Phosphorylation during Mouse Sperm Capacitation

Mammalian sperm acquire fertilization capacity in the female reproductive tract in a process known as capacitation. Capacitation-associated processes require energy. There remains an ongoing debate about the sources generating the ATP which fuels sperm progressive motility, capacitation, hyperactivation, and acrosome reaction. Here, we describe the application of an extracellular flux analyzer as a tool to analyze changes in energy metabolism during mouse sperm capacitation. Using H+- and O2- sensitive fluorophores, this method allows monitoring glycolysis and oxidative phosphorylation in real-time in non-capacitated versus capacitating sperm. Using this assay in the presence of different energy substrates and/or pharmacological activators and/or inhibitors can provide important insights into the contribution of different metabolic pathways and the intersection between signaling cascades and metabolism during sperm capacitation.

We describe the application of an extracellular flux analyzer to monitor real-time changes in glycolysis and oxidative phosphorylation during mouse sperm capacitation.

Mammalian sperm acquire fertilization capacity in the female reproductive tract in a process known as capacitation. Capacitation-associated processes ...

Measuring Nucleotide Binding to Intact, Functional Membrane Proteins in Real Time

We have developed a method to measure binding of adenine nucleotides to intact, functional transmembrane receptors in a cellular or membrane environment. This method combines expression of proteins tagged with the fluorescent non-canonical amino acid ANAP, and FRET between ANAP and fluorescent (trinitrophenyl) nucleotide derivatives. We present examples of nucleotide binding to ANAP-tagged KATP ion channels measured in unroofed plasma membranes and excised, inside-out membrane patches under voltage clamp. The latter allows for simultaneous measurements of ligand binding and channel current, a direct readout of protein function. Data treatment and analysis are discussed extensively, along with potential pitfalls and artefacts. This method provides rich mechanistic insights into the ligand-dependent gating of KATP channels and can readily be adapted to the study of other nucleotide-regulated proteins or any receptor for which a suitable fluorescent ligand can be identified.

This protocol presents a method for measuring adenine nucleotide binding to receptors in real time in a cellular environment. Binding is measured as F&#246;rster resonance energy transfer (FRET) between trinitrophenyl nucleotide derivatives and protein labeled with a non-canonical, fluorescent amino acid.

We have developed a method to measure binding of adenine nucleotides to intact, functional transmembrane receptors in a cellular or membrane environment. ...

Enabling Real-Time Compensation in Fast Photochemical Oxidations of Proteins for the Determination of Protein Topography Changes

Fast photochemical oxidation of proteins (FPOP) is a mass spectrometry-based structural biology technique that probes the solvent-accessible surface area of proteins. This technique relies on the reaction of amino acid side chains with hydroxyl radicals freely diffusing in solution. FPOP generates these radicals in situ by laser photolysis of hydrogen peroxide, creating a burst of hydroxyl radicals that is depleted on the order of a microsecond. When these hydroxyl radicals react with a solvent-accessible amino acid side chain, the reaction products exhibit a mass shift that can be measured and quantified by mass spectrometry. Since the rate of reaction of an amino acid depends in part on the average solvent accessible surface of that amino acid, measured changes in the amount of oxidation of a given region of a protein can be directly correlated to changes in the solvent accessibility of that region between different conformations (e.g., ligand-bound versus ligand-free, monomer vs. aggregate, etc.) FPOP has been applied in a number of problems in biology, including protein-protein interactions, protein conformational changes, and protein-ligand binding. As the available concentration of hydroxyl radicals varies based on many experimental conditions in the FPOP experiment, it is important to monitor the effective radical dose to which the protein analyte is exposed. This monitoring is efficiently achieved by incorporating an inline dosimeter to measure the signal from the FPOP reaction, with laser fluence adjusted in real-time to achieve the desired amount of oxidation. With this compensation, changes in protein topography reflecting conformational changes, ligand-binding surfaces, and/or protein-protein interaction interfaces can be determined in heterogeneous samples using relatively low sample amounts.

Fast photochemical oxidation of proteins is an emerging technique for the structural characterization of proteins. Different solvent additives and ligands have varied hydroxyl radical scavenging properties. To compare the protein structure in different conditions, real-time compensation of hydroxyl radicals generated in the reaction is required to normalize reaction conditions.

Fast photochemical oxidation of proteins (FPOP) is a mass spectrometry-based structural biology technique that probes the solvent-accessible surface area ...