The authors acknowledge funding from the National Institutes of Health R21CA182333.

1. Preparation of Polymeric Aqueous Two Phase System (ATPS)
<ol>
	<li>Weigh 0.5 g of polyethylene glycol (PEG) (MW: 35,000) and add it to 9.5 ml of complete growth medium in a sterile 15 ml conical to prepare 10 ml of 5% (w/v) aqueous PEG phase. 
	Note: Adding half of the medium to the conical first followed by adding the polymer and then the remaining amount of medium minimizes adhesion of the polymer to the conical walls and helps the polymer dissolve faster.</li>
	<li>Weigh 0.128 g of dextran (DEX) (MW: 500,000...

<ol>
	<li>Butcher, E. C., Berg, E. L., Kunkel, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systems+biology+in+drug+discovery.">Systems biology in drug discovery.</a> Nat. Biotechnol. 22, 1253-1259 (2004).</li><li>Gonzalez-Nicolini, V., Fussenegger, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+assays+for+anticancer+drug+discovery--a+novel+approach+based+on+engineered+mammalian+cell+lines.">In vitro assays for anticancer drug discovery--a novel approach based on engineered mammalian cell lines.</a> Anticancer Drugs. 16, 223-228 (2005).</li><li>Castel, D., Pitaval, A., Debily, M. A., Gidrol, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+microarrays+in+drug+discovery.">Cell microarrays in drug discovery.</a> Drug Discov. Today. 11, 616-622 (2006).</li><li>Gidrol, X., 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=2D+and+3D+cell+microarrays+in+pharmacology.">2D and 3D cell microarrays in pharmacology.</a> Current Opin. Pharmacol. 9, 664-668 (2009).</li><li>LaBarbera, D. V., Reid, B. G., Yoo, B. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+multicellular+tumor+spheroid+model+for+high-throughput+cancer+drug+discovery.">The multicellular tumor spheroid model for high-throughput cancer drug discovery.</a> Expert Opin. Drug Discov. 7, 819-830 (2012).</li><li>Ward, D. J., Martino, O. I., Simpson, S., Stevens, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decline+in+new+drug+launches:+myth+or+reality?+Retrospective+observational+study+using+30+years+of+data+from+the+UK.">Decline in new drug launches: myth or reality? Retrospective observational study using 30 years of data from the UK.</a> BMJ Open. 3, (2013).</li><li>Yamada, K. M., Cukierman, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+tissue+morphogenesis+and+cancer+in+3D.">Modeling tissue morphogenesis and cancer in 3D.</a> Cell. 130, 601-610 (2007).</li><li>Hirschhaeuser, F., 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=Multicellular+tumor+spheroids:+An+underestimated+tool+is+catching+up+again.">Multicellular tumor spheroids: An underestimated tool is catching up again.</a> J. Biotechnol. 148, 3-15 (2010).</li><li>Ghajar, C. M., Bissell, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor+engineering:+the+other+face+of+tissue+engineering.">Tumor engineering: the other face of tissue engineering.</a> Tissue Eng. A. 16, 2153-2156 (2010).</li><li>Kenny, P. 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+morphologies+of+breast+cancer+cell+lines+in+three-dimensional+assays+correlate+with+their+profiles+of+gene+expression.">The morphologies of breast cancer cell lines in three-dimensional assays correlate with their profiles of gene expression.</a> Mol. Oncol. 1, 84-96 (2007).</li><li>Carlsson, J., Yuhas, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid-overlay+culture+of+cellular+spheroids.">Liquid-overlay culture of cellular spheroids.</a> Rec. 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M., Fluri, D. A., Hengstler, J. G., Hierlemann, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reconfigurable+microfluidic+hanging+drop+network+for+multi-tissue+interaction+and+analysis.">Reconfigurable microfluidic hanging drop network for multi-tissue interaction and analysis.</a> Nat. Commun. 5, 4250 (2014).</li><li>Hsiao, A. Y., 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=Micro-ring+structures+stabilize+microdroplets+to+enable+long+term+spheroid+culture+in+384+hanging+drop+array+plates.">Micro-ring structures stabilize microdroplets to enable long term spheroid culture in 384 hanging drop array plates.</a> Biomed. Microdev. 14, 313-323 (2012).</li><li>Mehta, G., Hsiao, A. Y., Ingram, M., Luker, G. 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D., Tavana, H. <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+aqueous+biphasic+tumor+spheroid+microtechnology+for+anti-cancer+drug+testing+in+3D+culture.">Optimization of aqueous biphasic tumor spheroid microtechnology for anti-cancer drug testing in 3D culture.</a> Cell. Mol. Bioeng. 7, 344-354 (2014).</li><li>Albertsson, P. -. A., Tjerneld, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+diagrams.">Phase diagrams.</a> Methods Enzym. 228, 3-13 (1994).</li><li>Frampton, J. P., White, J. B., Abraham, A. T., Takayama, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+co-culture+patterning+using+aqueous+two-phase+systems.">Cell co-culture patterning using aqueous two-phase systems.</a> J. Vis. Exp. (73), (2013).</li><li>Frampton, J. P., 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=Aqueous+two-phase+system+patterning+of+detection+antibody+solutions+for+cross-reaction-free+multiplex+ELISA.">Aqueous two-phase system patterning of detection antibody solutions for cross-reaction-free multiplex ELISA.</a> Sci. Rep. 4, 4878 (2014).</li><li>Lai, D., Frampton, J. P., Tsuei, M., Kao, A., Takayama, S. <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+direct+visual+analysis+of+hydrolytic+enzyme+activity+using+aqueous+two-phase+system+droplet+phase+transitions.">Label-free direct visual analysis of hydrolytic enzyme activity using aqueous two-phase system droplet phase transitions.</a> Anal. Chem. 86, 4052-4057 (2014).</li><li>Petrak, D., Atefi, E., Yin, L., Chilian, W., Tavana, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+spatio-temporally+controlled+cell+microprinting+with+polymeric+aqueous+biphasic+system.">Automated spatio-temporally controlled cell microprinting with polymeric aqueous biphasic system.</a> Biotech. Bioeng. 11, 404-412 (2014).</li><li>Tavana, 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=Nanolitre+liquid+patterning+in+aqueous+environments+for+spatially+defined+reagent+delivery+to+mammalian+cells.">Nanolitre liquid patterning in aqueous environments for spatially defined reagent delivery to mammalian cells.</a> Nat. Mater. 8, 736-741 (2009).</li><li>Tavana, 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=Polymeric+aqueous+biphasic+system+rehydration+facilitates+high+throughput+cell+exclusion+patterning+for+cell+migration+studies.">Polymeric aqueous biphasic system rehydration facilitates high throughput cell exclusion patterning for cell migration studies.</a> Adv. Func. Mater. 21, 2920-2926 (2011).</li><li>Tavana, H., Mosadegh, B., Takayama, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymeric+aqueous+biphasic+systems+for+non-contact+cell+printing+on+cells:+engineering+heterocellular+embryonic+stem+cell+niches.">Polymeric aqueous biphasic systems for non-contact cell printing on cells: engineering heterocellular embryonic stem cell niches.</a> Adv. Mater. 22, 2628-2631 (2010).</li><li>Tavana, H., Mosadegh, B., Zamankhan, P., Grotberg, J. B., Takayama, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microprinted+feeder+cells+guide+embryonic+stem+cell+fate.">Microprinted feeder cells guide embryonic stem cell fate.</a> Biotechnol. Bioeng. 108, 2509-2516 (2011).</li><li>Kalluri, R., Zeisberg, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Nat Rev Cancer. 6, 392-401 (2006).</li><li>Olsen, C. J., Moreira, J., Lukanidin, E. M., Ambartsumian, N. 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Y., 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=Microfluidic+system+for+formation+of+PC-3+prostate+cancer+co-culture+spheroids.">Microfluidic system for formation of PC-3 prostate cancer co-culture spheroids.</a> Biomaterials. 30, 3020-3027 (2009).</li><li>Friedrich, J., Seidel, C., Ebner, R., Kunz-Schughart, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spheroid-based+drug+screen:+considerations+and+practical+approach.">Spheroid-based drug screen: considerations and practical approach.</a> Nat. Protoc. 4, 309-324 (2009).</li><li>Weigelt, B., Bissell, M. 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The authors have nothing to disclose.

Spheroids present a realistic model to better understand tumor physiology and drug efficacy and provide a useful tool for anti-cancer drug discovery. Such applications would greatly benefit from simple spheroid generation and maintenance techniques that only require standard labware, liquid handling tools and screening equipment. The use of an aqueous two-phase system to spontaneously aggregate cancer cells within the drop phase allows efficient production and maintenance of spheroids with robotic liquid handlers, and <e...

Cell-based assays provide an important tool for the development and discovery of new anti-cancer drugs.1,2 Historically, monolayer cultures of cancer cells have been employed to investigate the efficacy of candidate compounds against particular types of cancer cells. The ease of maintenance of monolayer cultures in standard culture plates, the compatibility of standard plates with commercial robotic tools for addition of reagents, and with screening equipment for downstream analysis of cellular responses to chemical compounds are the major benefits that render 2D cultures an attractive tool for drug testing.3 Unfortunately, monolayer cell assays often fail to predict the efficacy of compounds in vivo, making drug development and discovery an extremely costly process.4,5 Despite significant investment and effort by pharmaceutical companies and academic units, only ~1% of anti-cancer drugs in clinical trials were approved by the FDA over the past two decades.6 Disparity between 2D cultures and the complex 3D environment of cancer cells in vivo is a major shortcoming of monolayer culture systems.7 Therefore, screening of candidate compounds against tumor cells in a setting that more closely resembles the 3D tumor environment may expedite development of novel chemotherapy drugs.8
Cancer cell spheroids present a relevant 3D tumor model in vitro.9,10 Spheroids are compact clusters that form through spontaneous or induced assembly of cancer cells on non-adherent surfaces or in suspension using techniques such as spinner flask, liquid overlay, microfabricated micro-well arrays, microfluidics, and hanging drops.11-16 Spheroids mimic key features of solid tumors including geometry and limited transport of oxygen, nutrients, and drug compounds into the central zone; hence, they more closely regenerate drug response of solid tumors compared to monolayer cultures.17-19 Despite this marked benefit, spheroids are not routinely used for screening of chemical compounds against cancer cells. Difficulty of producing uniform sized spheroids in a standard high throughput setting that is compatible with commercially available robotics and screening/imaging tools impedes incorporation of spheroid culture into drug development pipeline. Although custom materials and plates have recently become commercially available to address this need, cost considerations deter their widespread use.
Two major techniques with the capability of producing consistent sized spheroids in high throughput use a new hanging drop platform and microfabricated micro-wells.13,16,20 However, both approaches require special plates and devices that are expensive to fabricate and inconvenient for endpoint users in core research centers and pharmaceutical industries where the most major efforts for the discovery of new anti-cancer drugs are made. Despite some improvements in the stability of cell-containing drops with a recent design of hanging drop plates, only every other hole of the plate is still used during culture to avoid spreading/merging of drops.16 This significantly decreases experimental throughput. Drug addition and renewal is difficult with manual or robotic pipetting and spheroids need to be transferred into a standard plate for biochemical analysis because this plate configuration is not readily compatible with conventional screening equipment such as plate readers.21 Micro-wells fabricated using soft lithography also allow controlled size spheroid production.13,20 However, incompatibility of this platform with standard pipetting tools prevents treating of individual spheroids with different drug compounds/concentrations, exposing all spheroids to a single treatment condition. Thus, this method is not appropriate for high throughput compound screening that requires simultaneous testing of multiple compounds/concentrations.
To overcome these obstacles, a new technique for high throughput production of consistently sized cancer cell spheroids in standard 96-well plates has been developed.22,23 The approach is based on a polymeric aqueous two-phase system (ATPS) with polyethylene glycol (PEG) and dextran (DEX) as phase-forming polymers.24 ATPSs have recently been utilized in a variety of novel cell biological applications to enable cell micropatterning and localized delivery of biological reagents to cells in highly aqueous media.25-32 To form a spheroid, cancer cells are mixed with the aqueous DEX phase and a sub-microliter drop of the resulting suspension is pipetted into a well containing the immersion aqueous PEG phase solution. The drop remains immiscible from the immersion phase and confines cells to facilitate formation of a spheroid. Importantly, the highly aqueous immersion phase provides nutrients to cells of the spheroid and minimizes the well-known problem of media evaporation common to some other assays that causes changes in media osmolality and fluctuations of drug concentrations. This technique enables spheroid production and drug treatment only using commercially-available reagents and pipetting tools in standard 96-well plates. Importantly, analysis of cellular responses of spheroids is performed in the same plate using standard biochemical assays and plate readers. The ease of working with ATPS and adaptability of the approach to robotic liquid handling makes high throughput generation of both mono-culture and co-culture spheroids a straightforward laboratory technique. This new approach will be a major step forward toward integration of cancer cell spheroids into drug development and discovery processes with improved testing throughput and cost-effectiveness (increasing numbers of tested compounds and reduced reagent consumption) and efficiency (reducing hands-on time).
A detailed protocol for robotic production of cancer cell spheroids in 96-well plates using the ATPS approach is described below. In addition, details of drug treatment of resulting spheroids and downstream analysis of cellular responses using a commercial biochemical assay are presented.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Reagents and Consumables</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylene glycol, Mw: 35,000</td>
			<td>Sigma-Aldrich</td>
			<td>94646</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextran, Mw: 500,000</td>
			<td>Pharmacosmos</td>
			<td>5510 0500 9007</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium (DMEM)</td>
			<td>Sigma-Aldrich</td>
			<td>D6429</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Sigma-Aldrich</td>
			<td>12306C</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutamine</td>
			<td>Life Technologies</td>
			<td>35050-061</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic</td>
			<td>Life Technologies</td>
			<td>15240-062</td>
			<td></td>
		</tr>
		<tr>
			<td>Clacein AM</td>
			<td>Life Technologies</td>
			<td>C3100MP</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoechst</td>
			<td>Life Technologies</td>
			<td>33342</td>
			<td></td>
		</tr>
		<tr>
			<td>Cisplatin</td>
			<td>Spectrum Chemicals</td>
			<td>15663-27-1</td>
			<td></td>
		</tr>
		<tr>
			<td>PrestoBlue</td>
			<td>Life Technologies</td>
			<td>A-13261</td>
			<td></td>
		</tr>
		<tr>
			<td>Pluronic F-108</td>
			<td>Sigma Aldrich</td>
			<td>542342</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable Tips (10 &#181;l)</td>
			<td>Fluotics</td>
			<td>C-P10V11.ST</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable Tips (70 &#181;l)</td>
			<td>Fluotics</td>
			<td>C-P70V11.ST</td>
			<td></td>
		</tr>
		<tr>
			<td>Round-bottom 96-well plates</td>
			<td>Corning</td>
			<td>7007</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Liquid Handler</td>
			<td>Agilent Technologies</td>
			<td>SRT Bravo</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate Reader</td>
			<td>Biotek Instruments</td>
			<td>Synergy H1M</td>
			<td></td>
		</tr>
	</tbody>
</table>

robotic production of cancer cell spheroids with an aqueous two-phase system for drug testing

Cancer cell spheroids present a relevant in vitro model of avascular tumors for anti-cancer drug testing applications. A detailed protocol for producing both mono-culture and co-culture spheroids in a high throughput 96-well plate format is described in this work. This approach utilizes an aqueous two-phase system to confine cells into a drop of the denser aqueous phase immersed within the second aqueous phase. The drop rests on the well surface and keeps cells in close proximity to form a single spheroid. This technology has been adapted to a robotic liquid handler to produce size-controlled spheroids and expedite the process of spheroid production for compound screening applications. Spheroids treated with a clinically-used drug show reduced cell viability with increase in the drug dose. The use of a standard micro-well plate for spheroid generation makes it straightforward to analyze viability of cancer cells of drug-treated spheroids with a micro-plate reader. This technology is straightforward to implement both robotically and with other liquid handling tools such as manual pipettes.

The workstation of the robotic liquid handler is shown in Figure 1. The pipetting head and all stations used in the robotic printing of spheroids in section 4.6 are labeled. The image shows the use of two different stations for tip boxes (one set of tips for mixing and the second set for aspirating/dispensing of cell suspension&#8211;aqueous DEX phase mixture). The entire setup is housed within a standard biological safety cabinet to maintain sterility. Figure 2 depicts a schematic of th...

Watch this Scientific Journal Video about Robotic Production of Cancer Cell Spheroids with an Aqueous Two-phase System for Drug Testing at JoVE.com

Robotic Production of Cancer Cell Spheroids with an Aqueous Two-phase System for Drug Testing

A protocol for robotic printing of cancer cell spheroids in a high throughput 96-well plate format using an aqueous two-phase system is presented.

Cancer cell spheroids present a relevant in vitro model of avascular tumors for anti-cancer drug testing applications. A detailed protocol for producing ...

robotic-production-cancer-cell-spheroids-with-an-aqueous-two-phase

Research

JoVE Journal

Bioengineering

8.9K visualizações.  The University of Akron. A protocol for robotic printing of cancer cell spheroids in a high throughput 96-well plate format using an aqueous two-phase system is presented.