The authors would like to acknowledge Ohio Cancer Research (OCR), OH, USA for funding this work as well as King Saud University (KSU), Riyadh, KSA for sponsoring the first author.&#160;Molecular weight of the fluorescent peptide sensor was measured using matrix assisted, laser desorption-ionization, time-of-flight (MALDI-TOF) mass spectrometry with assistance from the Campus Chemical Instrument Center Mass Spectrometry and Proteomics Facility at The Ohio State University.

1. Hydrogel components preparation
<ol>
	<li>Synthesize the fluorescent protease-degradable peptides as described elsewhere8, utilizing fluorescein as the fluorescent molecule and dabcyl as the quencher. Dissolve the peptide in DMSO to a concentration of 10 mM and store in a -80 &#176;C freezer in small (~30 &#181;L) aliquots to avoid repeated freeze-thaw cycles. 
	NOTE: These peptides can also be purchased commercially. This protocol requires a C-terminal cysteine in the peptide sequence t...

<ol>
	<li>Baker, B. M., Chen, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deconstructing+the+third+dimension+-+how+3D+culture+microenvironments+alter+cellular+cues.">Deconstructing the third dimension - how 3D culture microenvironments alter cellular cues.</a> Journal of Cell Science. 125 (13), 3015-3024 (2012).</li><li>Duval, K., 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=Modeling+Physiological+Events+in+2D+vs.+3D+Cell+Culture.">Modeling Physiological Events in 2D vs. 3D Cell Culture.</a> Physiology. 32 (4), 266-277 (2017).</li><li>Hoarau-V&#233;chot, J., Rafii, A., Touboul, C., Pasquier, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Halfway+between+2D+and+Animal+Models:+Are+3D+Cultures+the+Ideal+Tool+to+Study+Cancer-Microenvironment+Interactions.">Halfway between 2D and Animal Models: Are 3D Cultures the Ideal Tool to Study Cancer-Microenvironment Interactions.</a> International Journal of Molecular Sciences. 19 (1), (2018).</li><li>Lee, S. -. H., Miller, J. S., Moon, J. J., West, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteolytically+Degradable+Hydrogels+with+a+Fluorogenic+Substrate+for+Studies+of+Cellular+Proteolytic+Activity+and+Migration.">Proteolytically Degradable Hydrogels with a Fluorogenic Substrate for Studies of Cellular Proteolytic Activity and Migration.</a> Biotechnology Progress. 21 (6), 1736-1741 (2005).</li><li>DeForest, C. A., Polizzotti, B. D., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sequential+click+reactions+for+synthesizing+and+patterning+three-dimensional+cell+microenvironments.">Sequential click reactions for synthesizing and patterning three-dimensional cell microenvironments.</a> Nature Materials. 8 (8), 659-664 (2009).</li><li>Chalasani, 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=Live-Cell+Imaging+of+Protease+Activity:+Assays+to+Screen+Therapeutic+Approaches.">Live-Cell Imaging of Protease Activity: Assays to Screen Therapeutic Approaches.</a> Methods in Molecular Biology. 1574, 215-225 (2017).</li><li>Jedeszko, C., Sameni, M., Olive, M., Moin, K., Sloane, B. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+Protease+Activity+in+Living+Cells:+From+Two+Dimensions+to+Four+Dimensions.">Visualizing Protease Activity in Living Cells: From Two Dimensions to Four Dimensions.</a> Current Protocols in Cell Biology. 04, (2008).</li><li>Leight, J. L., Alge, D. L., Maier, A. J., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+measurement+of+matrix+metalloproteinase+activity+in+3D+cellular+microenvironments+using+a+fluorogenic+peptide+substrate.">Direct measurement of matrix metalloproteinase activity in 3D cellular microenvironments using a fluorogenic peptide substrate.</a> Biomaterials. 34 (30), 7344-7352 (2013).</li><li>Nagase, H., Visse, R., Murphy, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+and+function+of+matrix+metalloproteinases+and+TIMPs.">Structure and function of matrix metalloproteinases and TIMPs.</a> Cardiovascular Research. 69 (3), 562-573 (2006).</li><li>Tokito, A., Jougasaki, M., Tokito, A., Jougasaki, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+Metalloproteinases+in+Non-Neoplastic+Disorders.">Matrix Metalloproteinases in Non-Neoplastic Disorders.</a> International Journal of Molecular Sciences. 17 (7), 1178 (2016).</li><li>Visse, R., Nagase, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+metalloproteinases+and+tissue+inhibitors+of+metalloproteinases:+structure,+function,+and+biochemistry.">Matrix metalloproteinases and tissue inhibitors of metalloproteinases: structure, function, and biochemistry.</a> Circulation Research. 92 (8), 827-839 (2003).</li><li>Vihinen, P., K&#228;h&#228;ri, V. -. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+metalloproteinases+in+cancer:+Prognostic+markers+and+therapeutic+targets.">Matrix metalloproteinases in cancer: Prognostic markers and therapeutic targets.</a> International Journal of Cancer. 99 (2), 157-166 (2002).</li><li>Yodkeeree, S., Garbisa, S., Limtrakul, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tetrahydrocurcumin+inhibits+HT1080+cell+migration+and+invasion+via.+downregulation+of+MMPs+and+uPA1.">Tetrahydrocurcumin inhibits HT1080 cell migration and invasion via. downregulation of MMPs and uPA1.</a> APHS Acta Pharmacologica Sinica. 29 (7), 853-860 (2008).</li><li>Yodkeeree, S., Chaiwangyen, W., Garbisa, S., Limtrakul, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Curcumin,+demethoxycurcumin+and+bisdemethoxycurcumin+differentially+inhibit+cancer+cell+invasion+through+the+down-regulation+of+MMPs+and+uPA.">Curcumin, demethoxycurcumin and bisdemethoxycurcumin differentially inhibit cancer cell invasion through the down-regulation of MMPs and uPA.</a> The Journal of Nutritional Biochemistry. 20 (2), 87-95 (2009).</li><li>Mabry, K. M., Schroeder, M. E., Payne, S. Z., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-Dimensional+High-Throughput+Cell+Encapsulation+Platform+to+Study+Changes+in+Cell-Matrix+Interactions.">Three-Dimensional High-Throughput Cell Encapsulation Platform to Study Changes in Cell-Matrix Interactions.</a> ACS Applied Materials &amp; Interfaces. 8 (34), 21914-21922 (2016).</li><li>Sridhar, B. V., Doyle, N. R., Randolph, M. A., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalently+tethered+TGF-&#946;1+with+encapsulated+chondrocytes+in+a+PEG+hydrogel+system+enhances+extracellular+matrix+production.">Covalently tethered TGF-&#946;1 with encapsulated chondrocytes in a PEG hydrogel system enhances extracellular matrix production.</a> Journal of Biomedical Materials Research. Part A. 102 (12), 4464-4472 (2014).</li><li>Sridhar, B. V., 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=Development+of+a+cellularly+degradable+PEG+hydrogel+to+promote+articular+cartilage+extracellular+matrix+deposition.">Development of a cellularly degradable PEG hydrogel to promote articular cartilage extracellular matrix deposition.</a> Advanced Healthcare Materials. 4 (5), 702-713 (2015).</li><li>Fairbanks, B. D., Schwartz, M. P., Bowman, C. N., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoinitiated+polymerization+of+PEG-diacrylate+with+lithium+phenyl-2,4,6-trimethylbenzoylphosphinate:+polymerization+rate+and+cytocompatibility.">Photoinitiated polymerization of PEG-diacrylate with lithium phenyl-2,4,6-trimethylbenzoylphosphinate: polymerization rate and cytocompatibility.</a> Biomaterials. 30 (35), 6702-6707 (2009).</li><li>Mucha, 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=Membrane+Type-1+Matrix+Metalloprotease+and+Stromelysin-3+Cleave+More+Efficiently+Synthetic+Substrates+Containing+Unusual+Amino+Acids+in+Their+P1'+Positions.">Membrane Type-1 Matrix Metalloprotease and Stromelysin-3 Cleave More Efficiently Synthetic Substrates Containing Unusual Amino Acids in Their P1' Positions.</a> Journal of Biological Chemistry. 273 (5), 2763-2768 (1998).</li><li>Chai, S. C., Goktug, A. N., Chen, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assay+Validation+in+High+Throughput+Screening+-+from+Concept+to+Application.">Assay Validation in High Throughput Screening - from Concept to Application.</a> Drug Discovery and Development. , (2015).</li><li>Iversen, P. W., 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=HTS+Assay+Validation.">HTS Assay Validation.</a> Assay Guidance Manual. , (2004).</li><li>Leight, J. L., Tokuda, E. Y., Jones, C. E., Lin, A. J., Anseth, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifunctional+bioscaffolds+for+3D+culture+of+melanoma+cells+reveal+increased+MMP+activity+and+migration+with+BRAF+kinase+inhibition.">Multifunctional bioscaffolds for 3D culture of melanoma cells reveal increased MMP activity and migration with BRAF kinase inhibition.</a> Proceedings of the National Academy of Sciences of the United States of America. 112 (17), 5366-5371 (2015).</li><li>Patterson, J., Hubbell, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+proteolytic+degradation+of+molecularly+engineered+PEG+hydrogels+in+response+to+MMP-1+and+MMP-2.">Enhanced proteolytic degradation of molecularly engineered PEG hydrogels in response to MMP-1 and MMP-2.</a> Biomaterials. 31 (30), 7836-7845 (2010).</li></ol>

The authors have nothing to disclose.

3D in vitro cell culture recapitulates many important aspects of the in vivo environment. However, 3D culture also makes assessing cell function and signaling challenging, as many biological assays require cellular retrieval and large numbers of cells. Therefore, the development of a simple 3D culture system that enables measurement of cellular function without further sample processing would greatly increase the utility of 3D culture systems. The 3D system described here can be adapted for a variety of different applica...

Three-dimensional (3D) culture systems often more closely recapitulate in vivo cellular responses than traditional two-dimensional (2D) culture systems, see several excellent publications1,2,3. However, utilizing 3D culture systems to measure cell function has been challenging due to the difficulty of cellular retrieval and further sample processing. This difficulty limits the measurement of many cellular functions in 3D culture systems. To overcome this difficulty, new techniques are needed that enable easy measurement of cell function within 3D environments. One way to address this need is the development of materials that not only support 3D cell culture but also incorporate sensors to measure cell function. For example, several hydrogel systems have incorporated fluorogenic protease cleavable moieties to enable visualization of protease activity within 3D environments4,5,6,7. While these systems were originally utilized for microscopic imaging, these systems can also be adapted for use in a global matrix metalloproteinase (MMP) activity assay using a standard plate reader, enabling facile measurement of a cell function in a 3D environment8.
MMPs, a superfamily of zinc proteases, play critical roles in normal tissue homeostasis and in many diseases. MMPs degrade and remodel extracellular matrix (ECM), cleave cell surface receptors and cytokines and activate other MMPs9,10. MMPs play critical roles in physiological processes such as wound healing and in diseases such as arthritis, atherosclerosis, Alzheimer&#39;s, and cancer (see reviews in 9,10,11). In cancer, high MMP expression levels are strongly correlated with cancer metastasis and poor prognosis12. Furthermore, MMPs contribute to tumor progression by promoting cancer cell invasion and migration, cellular processes that are inherently 3D phenomena13,14. Therefore, there is much interest in the ability to measure MMP activity in 3D culture in many contexts, including fundamental biological studies and drug screening assays.
PEG hydrogels are widely used for 3D cell culture due to their high water content, resistance to protein adsorption, and tunable nature. PEG hydrogels have been functionalized with a number of moieties to direct cell function, such as with ECM mimetic peptides like RGD, RLD, and IKVAV to facilitate cell adhesion, or direct tethering of growth factors such as transforming growth factor-&#946; (TGF-&#946;)15,16. More recently, PEG hydrogels have been functionalized with sensor peptides that enable measurement of cell function as well5,8. Specifically, the use of a PEG hydrogel system functionalized with a fluorogenic MMP-degradable peptide enabled measurement of cellular MMP activity in 3D cultures with a standard plate reader and required no further processing. These systems are also compatible with other measurements of cellular function, including metabolic activity. Here, a protocol is described for the measurement of MMP activity of cells cultured in a 3D PEG hydrogel functionalized with a fluorogenic MMP-degradable peptide, and results presented demonstrating the initial optimization experiments needed for use of this assay. Human melanoma cells (A375) were encapsulated in the fluorogenic hydrogels over a range of seeding densities to determine the appropriate seeding densities that are within the working range of the assay. After 24 h of encapsulation, MMP and metabolic activity were measured utilizing a standard microplate reader. Next, MMP activity was normalized to metabolic activity to determine the seeding densities within the linear range of the assay. Finally, intra-plate coefficient of variation percentages (% CV) were calculated between triplicates to reflect the reproducibility of the obtained results. This method enables simple and fast 3D cell culture, and easy measurement of protease activity with minimal sample processing.

<table border="0" cellpadding="0" cellspacing="0" style="width:723px;" width="723">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">1X Phosphate Buffered Saline</td>
			<td style="width:268px;">Fisher Scientific</td>
			<td style="width:119px;">10-010-049</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Activated charcoal&#160;</td>
			<td style="width:268px;">Sigma-Aldrich</td>
			<td style="width:119px;">C3345</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Black round bottom 96-well plate</td>
			<td style="width:268px;">Brand-Tech</td>
			<td style="width:119px;">89093-600</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Cell adhesion peptide (CRGDS)</td>
			<td style="width:268px;">GenScript USA Inc.</td>
			<td style="width:119px;">custom made</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Collagenase enzyme type I&#160;</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">17100-017</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Dextran</td>
			<td style="width:268px;">Sigma-Aldrich</td>
			<td style="width:119px;">D4876</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">DMEM High Glucose Media</td>
			<td style="width:268px;">Invitrogen</td>
			<td style="width:119px;">11965118</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Fetal bovine serum (FBS)&#160;</td>
			<td style="width:268px;">Seradigm</td>
			<td style="width:119px;">1500-500</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Fluorescence microplate reader&#160;</td>
			<td style="width:268px;">BioTek</td>
			<td style="width:119px;">Cytation 3</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Hemocytometer</td>
			<td style="width:268px;">Hausser Scientific Co.</td>
			<td style="width:119px;">3200</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">L-glutamine</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">25030-081</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:272px;">MMP-degradable peptide crosslinker (KCGPQG&#8595;IWGQCK)</td>
			<td style="width:268px;">GenScript USA Inc.</td>
			<td style="width:119px;">custom made</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">NaOH</td>
			<td style="width:268px;">Fisher Scientific</td>
			<td style="width:119px;">S318500</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Penicillin /streptomycin</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">15140-122</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Resazurin (Alamar Blue)</td>
			<td style="width:268px;">Life Technologies</td>
			<td style="width:119px;">DAL1100</td>
			<td style="width:64px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:272px;">UV light&#160;</td>
			<td style="width:268px;">UVP</td>
			<td style="width:119px;">95-0006-02</td>
			<td style="width:64px;"></td>
		</tr>
	</tbody>
</table>

measuring global cellular matrix metalloproteinase and metabolic activity in 3d hydrogels

Three-dimensional (3D) cell culture systems often more closely recapitulate in vivo cellular responses and functions than traditional two-dimensional (2D) culture systems. However, measurement of cell function in 3D culture is often more challenging. Many biological assays require retrieval of cellular material which can be difficult in 3D cultures. One way to address this challenge is to develop new materials that enable measurement of cell function within the material. Here, a method is presented for measurement of cellular matrix metalloproteinase (MMP) activity in 3D hydrogels in a 96-well format. In this system, a poly(ethylene glycol) (PEG) hydrogel is functionalized with a fluorogenic MMP cleavable sensor. Cellular MMP activity is proportional to fluorescence intensity and can be measured with a standard microplate reader. Miniaturization of this assay to a 96-well format reduced the time required for experimental set up by 50% and reagent usage by 80% per condition as compared to the previous 24-well version of the assay. This assay is also compatible with other measurements of cellular function. For example, a metabolic activity assay is demonstrated here, which can be conducted simultaneously with MMP activity measurements within the same hydrogel. The assay is demonstrated with human melanoma cells encapsulated across a range of cell seeding densities to determine the appropriate encapsulation density for the working range of the assay. After 24 h of cell encapsulation, MMP and metabolic activity readouts were proportional to cell seeding density. While the assay is demonstrated here with one fluorogenic degradable substrate, the assay and methodology could be adapted for a wide variety of hydrogel systems and other fluorescent sensors. Such an assay provides a practical, efficient and easily accessible 3D culturing platform for a wide variety of applications.

The current assay was adapted from a previously developed and characterized 3D hydrogel culture system functionalized with a fluorogenic MMP cleavable sensor8. The fluorogenic MMP sensor used here consists of a peptide sequence, GPLAC(pMeOBzl)&#8595;WARKDDK(AdOO)C (&#8595; indicates the cleavage site) that was previously optimized for cleavage by MMP-14 and MMP-1119. The peptide is labeled with a fluorescent molecule (fluorescein) and a quen...

Watch this Scientific Journal Video about Measuring Global Cellular Matrix Metalloproteinase and Metabolic Activity in 3D Hydrogels at JoVE.com

Measuring Global Cellular Matrix Metalloproteinase and Metabolic Activity in 3D Hydrogels

Here, a protocol is presented for encapsulating and culturing cells in poly(ethylene glycol) (PEG) hydrogels functionalized with a fluorogenic matrix metalloproteinase (MMP)-degradable peptide. Cellular MMP and metabolic activity are measured directly from the hydrogel cultures using a standard microplate reader.

Three-dimensional (3D) cell culture systems often more closely recapitulate in vivo cellular responses and functions than traditional two-dimensional (2D) ...

3D culture makes it more difficult to measure cellular function, using standard biological assays. This protocol enables measurement of cellular and somatic activity without further sample processing, using a fluorescent sensor and a standard microplate reader. This protocol enables a number of new applications, including high throughput drug screening.Additionally, the fluorescent sensor can be exchanged with a different sensor to measure other proteases or cell functions. It is important to carefully plan out the experiment in advance, complete all calculations for the hydrogel preparation, and setup all equipments and reagents to minimize the time cells are in suspension. To begin, prepare the assay media with 1%charcoal stripped Fetal Bovine Serum, two mM L-glutamine, 10 units per mL of penicillin, and 10 micrograms per mL of streptomycin.Do not use phenol red media, which has more fluorescence interference. To make positive controls, add bacterial collagenase enzyme type one to the assay media at the concentrations of 10 and 1000 micrograms per mL. Next, prepare the hydrogel precursor solution by adding the reagents to a 1.5 mL tube.Make sure to vortex after addition of each component. Then divide the solution into multiple 1.5 mL tubes for different conditions. To encapsulate cells in hydrogels, first prepare a single cell suspension by washing a 10 cm dish of A375 melanoma cells with 10 mL of PBS.Then, add 0.05%trypsin to the dish, to trypsinize cells. Incubate the dish at 37 degrees Celsius and 5%carbon dioxide, for three minutes. After incubation, count the cells with a hemocytometer.Next, centrifuge the cell solution at 314 times G for three minutes. Aspirate the culture media, and resuspend cells in PBS buffer at approximately three times the final encapsulated density. Count the cells again to ensure an accurate cell concentration.Then, add suspended cells in PBS to each tube of the hydrogel precursor solution according to the required seeding density, and mix by pipetting up and down. For controlled conditions, only add PBS and vortex. Next, pipette 10 microliters of the hydrogel precursor solution into the middle of each well of a sterile, black, round-bottomed 96 well plate.Visually inspect the placement of the hydrogels within the wells. Non-centered hydrogels can be repositioned using a pipette tip before polymerization. To polymerize the hydrogel precursor solution, expose the plate to UV light at 4 milliwatts per square centimeter, for three minutes.Next, add 150 microliters of the assay media to all wells containing encapsulated cells, and 150 microliters of the collagenase enzyme solution to the wells of positive controls. Add 150 microliters of PBS buffer to the outer wells of the plate to reduce evaporation during incubation. Use a microplate reader to measure the fluorescent intensity of the plate at zero hour, immediately post encapsulation.Select the opaque 96 well plate protocol with 494 nanometer excitation, and 521 nanometer emission wavelengths. Next, incubate the plate at 37 degrees Celsius in 5%carbon dioxide, for 18 hours. Then add metabolic activity reagents at a one to 10 volume to volume ratio per well for all conditions and controls.Incubate the plate in 37 degrees Celsius, 5%carbon dioxide, for six hours. Finally, measure the fluorescent intensity of the plate at 24 hours, post encapsulation. Select the opaque 96 well plate protocol, with 494 nanometer excitation, and 521 nanometer emission wavelengths, for MMP activity.To measure the metabolic activity, select 560 nanometer excitation, and 590 nanometer emission wavelengths. In this study, upon exposure of the fluorogenic sensor to the appropriate protease, the quencher and fluorophore are separated, and fluorescence increases. Fluorescence measurements of the incubated hydrogels with bacterial collagenase enzyme type one, show that the lowest detected signal was produced by negative controls, with no collagenase.While the highest detected signal was produced by 1000 microgram per mL of collagenase or above, when the signal begins to plateau. The calculated working range was from approximately 0.16 to 474 micrograms per mL of collagenase. Fluorescence readings for A375 melanoma cell line, encapsulated in a range of densities right after encapsulation, were low across seeding densities, and similar to control gels without cells as expected.24 hours after encapsulation, MMP activity was directly proportional to the seeding density, and seeding densities at or greater than 1 million cells per mL, fall within the limits of the working range. Metabolic activity measurements of the A375 cell line, were also directly proportional to the cell seeding density. By normalizing MMP activity to metabolic activity, there was no significant difference in MMP activity per cell at seeding densities greater than 2 million cells per mL.Proper pipetting techniques is important. This include pre-wetting tips to achieve accurate volumes of viscous solutions. Also, centering hydrogel precursor solution within the well, is critical to achieve accurate measurements by the plate reader.To identify specific MMPs that contribute to MMP activity measured here, expression assays such as western blot or PCR could be used. The use of live cells requires proper biosafety procedure, aseptic technique, and a biological safety cabinet. The UV light is hazardous, use a shield to protect the user, and do not look directly into the light.

measuring-global-cellular-matrix-metalloproteinase-metabolic-activity

Research

JoVE Journal

Bioengineering

7.3K Görüntüleme.  The Ohio State University. 3D kültür, standart biyolojik tahliller kullanarak hücresel fonksiyonu ölçmeyi daha da zorlaştırır. Bu protokol, floresan sensör ve standart bir mikroplaka okuyucu kullanarak, daha fazla numune işleme olmadan hücresel ve somatik aktivitenin ölçülmesini sağlar. Bu protokol, yüksek iş kadar uyuşturucu taraması da dahil olmak üzere bir dizi yeni uygulama sağlar.Ayrıca, floresan sensör diğer proteazlar veya hücre fonksiyonlarını ölçmek için farklı bir sensör...