Name: fabrication of anisotropic polymeric artificial antigen presenting cells for cd8+ t cell activation
Uploaded: 2018-10-12T13:30:00
Description: Watch this Scientific Journal Video about Fabrication of Anisotropic Polymeric Artificial Antigen Presenting Cells for CD8+ T Cell Activation at JoVE.com

EBA (DGE-1746891) and KRR (DGE-1232825) thank the NSF Graduate Research Fellowship program for support. RAM thanks the National Research Service Award NIH NCI F31 (F31CA214147) and the Achievement Rewards for College Scientists Fellowship for support. The authors thank the NIH (R01EB016721 and R01CA195503), the Research to Prevent Blindness James and Carole Free Catalyst Award, and the JHU Bloomberg-Kimmel Institute for Cancer Immunotherapy for support.

All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Johns Hopkins University.
1. Fabrication of Spherical PLGA Particles of Tunable Size
<ol>
	<li>Preparation of materials for particle synthesis
	<ol>
		<li>Prepare 5% w/w polyvinyl alcohol (PVA) solution.
		<ol>
			<li>Add 500 mL of deionized (DI) water to an Erlenmeyer flask with a magnetic stir bar and place on hot plate stirrer at 500 rpm and monitor temperature with thermometer. Cov...

<ol>
	<li>Eggermont, L. J., Paulis, L. E., Tel, J., Figdor, C. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+efficient+cancer+immunotherapy:+Advances+in+developing+artificial+antigen-presenting+cells.">Towards efficient cancer immunotherapy: Advances in developing artificial antigen-presenting cells.</a> Trends in Biotechnology. 32 (9), 456-465 (2014).</li><li>Maus, M. V., Riley, J. L., Kwok, W. W., Nepom, G. T., June, C. 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F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+contact+requirements+for+activation+of+cytotoxic+T+lymphocytes.">Surface contact requirements for activation of cytotoxic T lymphocytes.</a> The Journal of Immunology. 149 (7), 2402-2405 (1992).</li><li>Steenblock, E. R., Fahmy, T. 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K., Mitragotri, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Particle+shape:+a+new+design+parameter+for+micro-+and+nanoscale+drug+delivery+carriers.">Particle shape: a new design parameter for micro- and nanoscale drug delivery carriers.</a> Journal of Controlled Release. 121 (1-2), 3-9 (2007).</li><li>Meyer, R. A., Meyer, R. S., Green, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+automated+multidimensional+thin+film+stretching+device+for+the+generation+of+anisotropic+polymeric+micro-+and+nanoparticles.">An automated multidimensional thin film stretching device for the generation of anisotropic polymeric micro- and nanoparticles.</a> Journal of Biomedical Materials Research Part A. 103 (8), 2747-2757 (2015).</li><li>Ho, C. C., Keller, A., Odell, J. A., Ottewill, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+monodisperse+ellipsoidal+polystyrene+particles.">Preparation of monodisperse ellipsoidal polystyrene particles.</a> Colloid and Polymer Science. 271 (5), 469-479 (1993).</li><li>Shum, H. 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This protocol details a versatile method for the precise generation of anisotropic polymeric particles. The thin film stretching technique described here is scalable, highly reproducible and inexpensive. Alternative techniques for generating anisotropic particles suffer from many limitations, including high cost, low throughput, and limited particle size. The thin film stretching approach is also advantageous because the particles are modified to be anisotropic after synthesis, and, as a result, is compatible with a wide...

Artificial antigen presenting cells (aAPC) have shown promise as immunomodulatory agents because they can generate a robust antigen-specific T cell response. Essential to these platforms are their ability to efficiently present crucial signals for T cell activation. Acellular aAPC are an attractive alternative to cell-based aAPC because they are easier and less costly to fabricate, face fewer challenges during scale-up and translation, and alleviate risks associated with cell-based therapies. Acellular aAPC also allow for a high degree of control over signal presentation parameters and physical properties of the surface that will interface with T cells1.
aAPC must recapitulate a minimum of two signals essential for T cell activation. Signal 1 provides antigen recognition and occurs when the T cell receptor (TCR) recognizes and engages with an MHC class I or II bearing its cognate antigen, culminating in signaling through the TCR complex. To bypass the antigen specificity requirement, aAPC systems often bear an agonistic monoclonal antibody against the CD3 receptor, which nonspecifically stimulates the TCR complex. Recombinant forms of MHC, particularly MHC multimers, have also been used on the surface of aAPC to provide antigen specificity2,3. Signal 2 is a costimulatory signal that directs T cell activity. To provide the costimulation necessary for T cell activation, the CD28 receptor is generally stimulated with an agonistic antibody presented on the aAPC surface, although other costimulatory receptors such as 4-1BB have been successfully targeted4. Signal 1 and 2 proteins are typically immobilized on the surface of rigid particles to synthesize aAPC. Historically, aAPC have been fabricated from a variety of materials, including polystyrene4,5 and iron dextran6. Newer systems utilize biodegradable polymers like poly(lactic-co-glycolic acid) (PLGA) to generate aAPC that can be easily coupled to signal proteins, are suitable for direct administration in vivo, and can facilitate the sustained release of encapsulated cytokines or soluble factors to augment T cell activation7,8.
In addition to the presence of necessary signal proteins, receptor engagement over a sufficiently large surface area during the aAPC/T cell interaction is essential for T cell activation. Thus, physical parameters of the aAPC such as size and shape drastically alter their available contact area and affect their ability to stimulate T cells. Micron-sized aAPC have been shown to be more effective at stimulating T cells than their nanoscale counterparts9,10. However, nano-aAPC can have superior biodistribution and better drainage to the lymph nodes that may enhance their performance in vivo over micro-aAPC11. Shape is another variable of interest in particle-based aAPC systems. Anisotropic aAPC have recently been shown to be more effective than isotropic particles at stimulating T cells, mainly due to enhanced interaction with target cells coupled with reduced non-specific cell uptake. Cells preferentially bind to the long axis of ellipsoidal particles, and the larger radius of curvature and flatter surface allow for more contact between the aAPC and T cell12. The long axis of ellipsoidal particles also discourages phagocytosis, resulting in increased circulation time compared to spherical particles following in vivo administration12,13. Because of these advantages, ellipsoidal particles mediate greater expansion of antigen-specific T cells in vitro and in vivo compared to spherical particles, an effect observed at both the micro and nanoscales12,13. There are various strategies to fabricate anisotropic particles, but thin-film stretching is a simple, widely accepted method used to generate a range of diverse particle shapes14. Following synthesis, particles are cast into films and stretched in one or two dimensions at a temperature above the glass transition temperature of the particle material. The film is then dissolved to retrieve the particles. Despite growing interest in anisotropic particles, current approaches for fabricating particle-based aAPC are mostly limited to isotropic systems, and methods of altering particle shape can be difficult to implement, incompatible with certain aAPC synthesis strategies, and lack precision and reproducibility15. Our thin-film stretching technique can be performed manually or in an automated fashion to rapidly generate anisotropic particles synthesized from a variety of biodegradable polymers, stretched to a desired aspect ratio in one or two dimensions15.
Based on our previous work, we developed a biodegradable particle-based approach combined with scalable thin-film stretching technology to rapidly generate aAPC with tunable size and shape in a standardized fashion for T cell expansion ex vivo or in vivo. Our protein conjugation strategy can be used to couple any protein(s) of interest to carboxyl groups on the particle surface at a desired density, giving this aAPC system a high degree of flexibility. We also describe methods to characterize the size, morphology, and surface protein content of aAPC, and to evaluate their functionality in vitro. This protocol can be easily adapted to expand immune cells ex vivo or in vivo for a variety of immunotherapeutic applications.

<table>
	<tbody>
		<tr>
			<td>Poly(vinyl alcohol), MW 25000, 88% hydrolyzed</td>
			<td>Polysciences, Inc.</td>
			<td>02975-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma-Aldrich</td>
			<td>G9012</td>
			<td></td>
		</tr>
		<tr>
			<td>Digital Thermometer</td>
			<td>Fluke</td>
			<td>N/A</td>
			<td>Model name: Fluke 52 II</td>
		</tr>
		<tr>
			<td>Immersion Temperature Probe</td>
			<td>Fluke</td>
			<td>N/A</td>
			<td>Model name: Fluke 80PK 22</td>
		</tr>
		<tr>
			<td>Digital Hotplate &#38; Stirrer</td>
			<td>Benchmark Scientific</td>
			<td>H3760-HS</td>
			<td></td>
		</tr>
		<tr>
			<td>Multipoint stirrer</td>
			<td>Thermo Fisher Scientific</td>
			<td>50093538</td>
			<td></td>
		</tr>
		<tr>
			<td>Resomer RG 504 H, Poly(D,L-lactide-co-glycolide)</td>
			<td>Sigma-Aldrich</td>
			<td>719900</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichloromethane</td>
			<td>Sigma-Aldrich</td>
			<td>D65100</td>
			<td></td>
		</tr>
		<tr>
			<td>Homogenizer</td>
			<td>IKA</td>
			<td>&#160;0003725001</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator</td>
			<td>Sonics &#38; Materials, Inc.</td>
			<td>N/A</td>
			<td>Model number: VC 505</td>
		</tr>
		<tr>
			<td>Sonicator sound abating enclosure</td>
			<td>Sonics &#38; Materials, Inc.</td>
			<td>N/A</td>
			<td>Part number: 630-0427</td>
		</tr>
		<tr>
			<td>Sonicator probe</td>
			<td>Sonics &#38; Materials, Inc.</td>
			<td>N/A</td>
			<td>Part number: 630-0220</td>
		</tr>
		<tr>
			<td>Sonicator microtip</td>
			<td>Sonics &#38; Materials, Inc.</td>
			<td>N/A</td>
			<td>Part number: 630-0423</td>
		</tr>
		<tr>
			<td>High speed centrifuge</td>
			<td>Beckman Coulter</td>
			<td>N/A</td>
			<td>Model number: J-20XP (discontinued), alternative model: J-26XP</td>
		</tr>
		<tr>
			<td>High speed centrifuge rotor</td>
			<td>Beckman Coulter</td>
			<td>369691</td>
			<td>Model number: JA-17</td>
		</tr>
		<tr>
			<td>High speed polycarbonate centrifuge tubes</td>
			<td>Thermo Fisher Scientific</td>
			<td>3118-0050</td>
			<td>50 mL, screw cap</td>
		</tr>
		<tr>
			<td>Rectangular disposable petri dish</td>
			<td>VWR International</td>
			<td>25384-322</td>
			<td>75 x 50 x 10 mm</td>
		</tr>
		<tr>
			<td>Square disposable petri dish</td>
			<td>VWR International</td>
			<td>10799-140</td>
			<td>100 mm x 100 mm</td>
		</tr>
		<tr>
			<td>LEAF&#160;Purified anti-mouse CD3&#949; Antibody</td>
			<td>Biolegend</td>
			<td>100314</td>
			<td></td>
		</tr>
		<tr>
			<td>InVivoMab anti-mouse CD28, clone 37.51</td>
			<td>Bio X Cell</td>
			<td>BE0015-1</td>
			<td></td>
		</tr>
		<tr>
			<td>N-(3-Dimethylaminopropyl)-N&#8242;-ethylcarbodiimide hydrochloride</td>
			<td>Sigma-Aldrich</td>
			<td>E6383</td>
			<td></td>
		</tr>
		<tr>
			<td>N-Hydroxysulfosuccinimide sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>56485</td>
			<td></td>
		</tr>
		<tr>
			<td>MES</td>
			<td>Sigma-Aldrich</td>
			<td>M3671</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 anti-mouse CD3 Antibody</td>
			<td>Biolegend</td>
			<td>100212</td>
			<td></td>
		</tr>
		<tr>
			<td>APC anti-mouse CD28 Antibody</td>
			<td>Biolegend</td>
			<td>102109</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning&#160;96 Well Solid Polystyrene Microplate</td>
			<td>Sigma-Aldrich</td>
			<td>CLS3915</td>
			<td>flat bottom, black polystyrene</td>
		</tr>
		<tr>
			<td>Protein LoBind Tubes, 1.5 mL</td>
			<td>Eppendorf</td>
			<td>22431081</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI 1640 Medium (+ L-Glutamine)</td>
			<td>ThermoFisher Scientific</td>
			<td>11875093</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Sigma-Aldrich</td>
			<td>F4135</td>
			<td>Heat Inactivated, sterile-filtered</td>
		</tr>
		<tr>
			<td>Ciprofloxacin</td>
			<td>Sigma-Aldrich</td>
			<td>17850</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol</td>
			<td>Sigma-Aldrich</td>
			<td>M6250</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Human IL-2 (carrier-free)</td>
			<td>Biolegend</td>
			<td>589102</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Pyruvate (100 mM)</td>
			<td>ThermoFisher Scientific</td>
			<td>11360070</td>
			<td></td>
		</tr>
		<tr>
			<td>MEM Non-Essential Amino Acids Solution (100X)</td>
			<td>ThermoFisher Scientific</td>
			<td>11140050</td>
			<td></td>
		</tr>
		<tr>
			<td>MEM Vitamin Solution (100X)</td>
			<td>ThermoFisher Scientific</td>
			<td>11120052</td>
			<td></td>
		</tr>
		<tr>
			<td>CD8a+&#160;T Cell Isolation Kit, mouse</td>
			<td>Miltenyi Biotech</td>
			<td>130-104-075</td>
			<td></td>
		</tr>
		<tr>
			<td>CellTrace CFSE Cell Proliferation Kit</td>
			<td>ThermoFisher Scientific</td>
			<td>C34554</td>
			<td></td>
		</tr>
		<tr>
			<td>LS Columns</td>
			<td>Miltenyi Biotech</td>
			<td>130-042-401</td>
			<td></td>
		</tr>
		<tr>
			<td>MidiMACS Separator</td>
			<td>Miltenyi Biotech</td>
			<td>130-042-302</td>
			<td></td>
		</tr>
		<tr>
			<td>MACS Multistand</td>
			<td>Miltenyi Biotech</td>
			<td>130-042-303</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Cytometer</td>
			<td>Accuri C6</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Synergy 2 Multi-Detection Microplate Reader</td>
			<td>BioTek</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>autoMACS Running Buffer</td>
			<td>Miltenyi BIotech</td>
			<td>130-091-221</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Strainer</td>
			<td>ThermoFisher Scientific</td>
			<td>22363548</td>
			<td>Sterile, 70 &#181;m nylon mesh</td>
		</tr>
		<tr>
			<td>ACK Lysing Buffer</td>
			<td>ThermoFisher Scientific</td>
			<td>A1049201</td>
			<td></td>
		</tr>
		<tr>
			<td>C57BL/6J (Black 6) Mouse</td>
			<td>The Jackson Laboratory</td>
			<td>000664</td>
			<td>Male, at least 7 weeks old</td>
		</tr>
		<tr>
			<td>U-Bottom Tissue Culture Plates</td>
			<td>VWR</td>
			<td>353227</td>
			<td>Sterile, 96-well tissue culture treated polystyrene plates</td>
		</tr>
		<tr>
			<td>40 V DC Power Supply</td>
			<td>Probotix</td>
			<td>LPSK-4010</td>
			<td></td>
		</tr>
		<tr>
			<td>PTFE Coated Wire</td>
			<td>Mouser</td>
			<td>602-5858-100-01</td>
			<td>This is for a 100 ft. spool but an equivalent wire will work</td>
		</tr>
		<tr>
			<td>Stepper Motor Driver</td>
			<td>Probotix</td>
			<td>MondoStep5.6</td>
			<td></td>
		</tr>
		<tr>
			<td>IDC Connector Kit</td>
			<td>Probotix</td>
			<td>IDCM-10-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcontroller</td>
			<td>Probotix</td>
			<td>PBX-RF</td>
			<td></td>
		</tr>
		<tr>
			<td>4A Fuses</td>
			<td>Radio Shack</td>
			<td>2701026</td>
			<td>Equivalent fuses will work as well</td>
		</tr>
		<tr>
			<td>DB25 Male to Male Cable</td>
			<td>Probotix</td>
			<td>DB25-6</td>
			<td></td>
		</tr>
		<tr>
			<td>USB-A to USB-B Cable</td>
			<td>Staples</td>
			<td>2094915</td>
			<td>Equivalent cable will work as well</td>
		</tr>
		<tr>
			<td>8-Pin Amphenol Connectors Male and Female</td>
			<td>Mouser</td>
			<td>654-97-3100A-20-7P and 654-97-3106A20-7S</td>
			<td></td>
		</tr>
		<tr>
			<td>Stepper Motor</td>
			<td>Probotix</td>
			<td>HT23-420-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Right Hand Lead Screw</td>
			<td>Roton</td>
			<td>60722</td>
			<td></td>
		</tr>
		<tr>
			<td>Left Hand Lead Screw</td>
			<td>Roton</td>
			<td>60723</td>
			<td></td>
		</tr>
		<tr>
			<td>Screws</td>
			<td>McMaster Carr</td>
			<td>92196A151</td>
			<td></td>
		</tr>
		<tr>
			<td>Neoprene Rubber</td>
			<td>McMaster Carr</td>
			<td>8698K51</td>
			<td></td>
		</tr>
		<tr>
			<td>Right Handed Flanged Lead Nut</td>
			<td>Roton</td>
			<td>91962</td>
			<td></td>
		</tr>
		<tr>
			<td>Left Handed Flanged Lead Nut</td>
			<td>Roton</td>
			<td>91963</td>
			<td></td>
		</tr>
		<tr>
			<td>Linux Control Computer</td>
			<td>Probotix</td>
			<td>LCNC-PC</td>
			<td>Any computer with matching specification and Linux operating system will work</td>
		</tr>
		<tr>
			<td>Corning bottle-top vacuum filter system</td>
			<td>Sigma-Aldrich</td>
			<td>CLS431097</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan Blue Solution, 0.4 %</td>
			<td>ThermoFisher Scientific</td>
			<td>15250061</td>
			<td></td>
		</tr>
	</tbody>
</table>

fabrication of anisotropic polymeric artificial antigen presenting cells for cd8+ t cell activation

Artificial antigen presenting cells (aAPC) are a promising platform for immune modulation due to their potent ability to stimulate T cells. Acellular substrates offer key advantages over cell-based aAPC, including precise control of signal presentation parameters and physical properties of the aAPC surface to modulate its interactions with T cells. aAPC constructed from anisotropic particles, particularly ellipsoidal particles, have been shown to be more effective than their spherical counterparts at stimulating T cells due to increased binding and larger surface area available for T cell contact, as well as reduced nonspecific uptake and enhanced pharmacokinetic properties. Despite increased interest in anisotropic particles, even widely accepted methods of generating anisotropic particles such as thin-film stretching can be challenging to implement and use reproducibly.
To this end, we describe a protocol for the rapid, standardized fabrication of biodegradable anisotropic particle-based aAPC with tunable size, shape, and signal presentation for T cell expansion ex vivo or in vivo, along with methods to characterize their size, morphology, and surface protein content, and to assess their functionality. This approach to fabricating anisotropic aAPC is scalable and reproducible, making it ideal for generating aAPC for &#34;off-the-shelf&#34; immunotherapies.

A schematic for the automated 2D thin film stretching device is given in Figure 1. A schematic and description for a 1D thin film stretching device is given in Ho et al.17 The stretcher is constructed from aluminum parts using standard milling and machining techniques. Similar to the 1D stretcher, the 2D stretcher consists of metallic grips and guide rails. Bidirectional lead screws are used to translate linear to rotational motion. Th...

Watch this Scientific Journal Video about Fabrication of Anisotropic Polymeric Artificial Antigen Presenting Cells for CD8+ T Cell Activation at JoVE.com

Fabrication of Anisotropic Polymeric Artificial Antigen Presenting Cells for CD8+ T Cell Activation

Here, we present a protocol to quickly and reproducibly generate biologically inspired, biodegradable articifical antigen presenting cells (aAPC) with tunable size, shape, and surface protein presentation for T cell expansion ex vivo or in vivo.

Artificial antigen presenting cells (aAPC) are a promising platform for immune modulation due to their potent ability to stimulate T cells. Acellular ...

This method can help answer key questions in the amino-engineering field. Such as, what is the role of particle physical properties on biomaterial immune cell interactions and activation. The main advantage of this technique is that it enables an independent control of the size and shape of biomimetic particles.The implications of this technique extend toward the therapy of cancer as it is an off the shelf particle therapy that can cause in vivo cell mediated immune responses. Though this method can provide insight into cancer amino-therapy, it can also be applied to other systems. Such as, infectious disease or Type One diabetes.For micro-particle synthesis, begin by weighing out 100 milligrams of poly(lactic-co-glycolic acid)or PLGA, into a scintillation vial and dissolving the PLGA in five milliliters of dichloromethane by vortexing. Place a homogenizer in a beaker containing 50 milliliters of 1%polyvinyl alcohol, or PVA solution, so that the homogenizer is as close to the bottom of the beaker as possible without touching it. Turn on the homogenizer to the appropriate speed and add the PLGA solution to the beaker for one minute of homogenization.At the end of the homogenization, pour the polyvinyl alcohol PLGA micro-particle solution into a beaker containing 100 milliliters of 5%PVA solution on a stir plate in a chemical hood and stir the solution for at least four hours. When the solvent has evaporated, pour the particle solution into 50 milliliter conical tubes and collect the particles by centrifugation. Replace the supernatant in each tube with 20 milliliters of de-ionized water and re-suspend the particles by vortexing.Then bring the final volume in each tube up to 50 milliliters with fresh de-ionized water and wash the particles two more times as just demonstrated. For nano-particle synthesis, dissolve 200 milligrams of PLGA in five milliliters of dichloromethane and place a sonicator probe in a beaker containing 50 milliliters of 1%PVA solution on ice without touching the bottom of the beaker. Begin the sonication at 12 watts and immediately add the PLGA solution to the beaker for a two minute sonication to generate nano-particles with an approximate 200 nanometer diameter.After sonication, pour the 1%polyvinyl alcohol PLGA nano-particle solution into a beaker containing 100 milliliters of 5 PVA solution on a stir plate for four hours of solvent evaporation in a chemical fume hood. When all of the solvent is evaporated, pour the particle solution into 50 milliliter conical tubes for centrifugation to remove any micro-particles and remove the supernatants. Then transfer the nano-particles into high speed centrifuge tubes for three washes in de-ionized water as demonstrated.For polymeric particle fabrication, after the last wash, re-suspend the particles in approximately one milliliter of fresh de-ionized water and add film casting solution to the particles to a final concentration of 2.5 milligrams per milliliter particles. Transfer the particle suspension in 10 milliliter aliquots into 75 by 50 millimeter rectangular Petri dishes for one dimensional stretching. Or in 15 milliliter aliquots into 100 by 100 millimeter square Petri dishes for two dimensional stretching.After overnight drying in a chemical hood, use tweezers to remove the films and trim the edges with scissors. For 1D stretching, place the two short edges of one film between two pieces of neoprene rubber for mounting onto the aluminum blocks of one axis of an automated thin film stretching device. Then use an Allen wrench to screw the metal grips on top of the rubber to hold the film in place.For 2D stretching, mount all four edges onto four aluminum blocks to stretch the film on both axes measure and record the length of film in between the aluminum blocks on one axis for one D stretching or both axes for 2D stretching and calculate the distance required to stretch the film in one or two directions based on the desired fold stretch. Then place the film loaded stretching device in an oven at 90 degrees Celsius next to a larger beaker of a small amount of water to bring the film to temperature over 10 minutes. When the stretching is complete, let the film cool to room temperature for 20 minutes.For 1D stretching, cut the film out of the stretching device at the edges. For 2D stretching, cut out and save the center square of film that is uniformly stretched on both axes. Place the films in 50 milliliter conical tubes with no more than two films per tube and add approximately 25 milliliters of de-ionized water to each tube for vortexing.When the films have dissolved, wash the particles three times in de-ionized water as demonstrated. Re-suspending the particles in approximately one milliliter of fresh de-ionized water per tube after the last wash. Then freeze the particles at minus 80 degrees Celsius for one hour or overnight lyophilization.The next morning, re-suspend the lyophilized micro or nano-particles at 20 milligrams per milliliter in freshly prepared MES buffer with vortexing. Add 100 microliters of the particle solution to a polypropylene micro centrifuge tube containing 900 microliters of MES buffer and add 100 microliters of freshly prepared EDC NHS solution. Mix the particles by vortexing and incubate the particles on an inverter at room temperature for 30 minutes.At the end of the incubation, collect the particles by centrifugation and re-suspend the micro-particle pellets in one milliliter of PBS by vortexing or re-suspend the nano-particles in one milliliter of PBS by five seconds of sonication at two to three watts. Next, add eight micrograms of a suitable signal one protein and 10 micrograms of anti mouse CD28 antibody to the micro-particles, or 16 micrograms of the signal one protein and 20 micrograms of anti mouse CD28 to the nano-particles. Bring the final volume in each tube to 1.1 milliliter with PBS and incubate the particles overnight on an inverter at four degrees Celsius.The next day, wash the particles three times in de-ionized water as demonstrated. These PLGA nano and micro-particles were synthesized using the single emulsion techniques as demonstrated and imaged using transmission and scanning electron microscopy. After homogenization, the micro-particles demonstrated an average diameter of about three micrometers.The spherical micro-particles had an aspect ration of about one, while the 1D stretched prolate ellipsoidal particles had a larger aspect ratio of about three and a half and the 2D stretched oblate ellipsoidal particles had an aspect ratio of about 1.2, roughly maintaining an aspect ratio of one. Conjugation efficiency results reveal the similar amounts of protein on the surface of spherical and ellipsoidal micro-artificial antigen presenting cells, or AAPC and nano-AAPC, demonstrating that protein coupling during AAPC synthesis occurs in a concentration dependent manner. Prolate ellipsoidal AAPC were found to induce higher levels of T cell proliferation at sub-saturating doses than spherical AAPC with the best separation achieved at a 01 milligram dose.After seven days, manual counting of the T cells revealed that prolate ellipsoidal AAPC more effectively stimulate T cells compared to their spherical counterparts at the micro and nano scale in a dose dependent manner. Following this procedure, AAPC can be administrated in vivo to gauge their therapeutic efficacy and pharmacokinetics. After its development, this technique helped pave the way for researchers in the field of immuno-engineering to explore the effect of anisotropy on AAPC efficacy.

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Research

JoVE Journal

Environment

Measuring Fluxes of Mineral Nutrients and Toxicants in Plants with Radioactive Tracers

Unidirectional influx and efflux of nutrients and toxicants, and their resultant net fluxes, are central to the nutrition and toxicology of plants. Radioisotope tracing is a major technique used to measure such fluxes, both within plants, and between plants and their environments. Flux data obtained with radiotracer protocols can help elucidate the capacity, mechanism, regulation, and energetics of transport systems for specific mineral nutrients or toxicants, and can provide insight into compartmentation and turnover rates of subcellular mineral and metabolite pools. Here, we describe two major radioisotope protocols used in plant biology: direct influx (DI) and compartmental analysis by tracer efflux (CATE). We focus on flux measurement of potassium (K+) as a nutrient, and ammonia/ammonium (NH3/NH4+) as a toxicant, in intact seedlings of the model species barley (Hordeum vulgare L.). These protocols can be readily adapted to other experimental systems (e.g., different species, excised plant material, and other nutrients/toxicants). Advantages and limitations of these protocols are discussed.

In planta measurement of nutrient and toxicant fluxes is essential to the study of plant nutrition and toxicity. Here, we cover radiotracer protocols for influx and efflux determination in intact plant roots, using potassium (K+) and ammonia/ammonium (NH3/NH4+) fluxes as examples. Advantages and limitations of such techniques are discussed.

Unidirectional influx and efflux of nutrients and toxicants, and their resultant net fluxes, are central to the nutrition and toxicology of plants. ...

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) was extracted using six different methods (centrifugation, sonication, ethylenediaminetetraacetic acid (EDTA), formamide with sodium hydroxide (NaOH), formaldehyde with NaOH and sodium carbonate (Na2CO3) with heat and constant mixing). AGS was collected from a pilot wastewater treatment reactor. The ionic gel-forming property of the extracted EPS of the six different extraction methods was tested with calcium ions (Ca2+). From the six extraction methods used, only the Na2CO3 extraction could solubilize the hydrogel matrix of AGS. The alginate-like extracellular polymers (ALE) recovered with this method formed ionic gel beads with Ca2+. The Ca2+-ALE beads were stable in EDTA, formamide with NaOH and formaldehyde with NaOH, indicating that ALE are one part of the structural polymers in EPS. It is recommended to use an extraction method that combines physical and chemical treatment to solubilize AGS and extract structural EPS.

The protocol provides a methodology to solubilize aerobic granular sludge in order to extract alginate-like extracellular polymers (ALE).

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) ...

Functionalization and Dispersion of Carbon Nanomaterials Using an Environmentally Friendly Ultrasonicated Ozonolysis Process

Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the as-received form, carbon nanomaterials, such as carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs), may contain large agglomerates. Both agglomerates and impurities will diminish the benefits of the unique electrical and mechanical properties offered when CNTs or GNPs are incorporated into polymers or composite material systems. Whilst a variety of methods exist to functionalize carbon nanomaterials and to create stable dispersions, many the processes use harsh chemicals, organic solvents, or surfactants, which are environmentally unfriendly and may increase the processing burden when isolating the nanomaterials for subsequent use. The current research details the use of an alternative, environmentally friendly technique for functionalizing CNTs and GNPs. It produces stable, aqueous dispersions free of harmful chemicals. Both CNTs and GNPs can be added to water at concentrations up to 5 g/L and can be recirculated through a high-powered ultrasonic cell. The simultaneous injection of ozone into the cell progressively oxidizes the carbon nanomaterials, and the combined ultrasonication breaks down agglomerates and immediately exposes fresh material for functionalization. The prepared dispersions are ideally suited for the deposition of thin films onto solid substrates using electrophoretic deposition (EPD). CNTs and GNPs from the aqueous dispersions can be readily used to coat carbon- and glass-reinforcing fibers using EPD for the preparation of hierarchical composite materials.

Here, a novel method for the functionalization and stable dispersion of carbon nanomaterials in aqueous environments is described. Ozone is injected directly into an aqueous dispersion of carbon nanomaterial that is continuously recirculated through a high-powered ultrasonic cell.

Functionalization of carbon nanomaterials is often a critical step that facilitates their integration into larger material systems and devices. In the ...

Ecosystem Fabrication (EcoFAB) Protocols for The Construction of Laboratory Ecosystems Designed to Study Plant-microbe Interactions

Beneficial plant-microbe interactions offer a sustainable biological solution with the potential to boost low-input food and bioenergy production. A better mechanistic understanding of these complex plant-microbe interactions will be crucial to improving plant production as well as performing basic ecological studies investigating plant-soil-microbe interactions. Here, a detailed description for ecosystem fabrication is presented, using widely available 3D printing technologies, to create controlled laboratory habitats (EcoFABs) for mechanistic studies of plant-microbe interactions within specific environmental conditions. Two sizes of EcoFABs are described that are suited for the investigation of microbial interactions with various plant species, including Arabidopsis thaliana, Brachypodium distachyon, and Panicum virgatum. These flow-through devices allow for controlled manipulation and sampling of root microbiomes, root chemistry as well as imaging of root morphology and microbial localization. This protocol includes the details for maintaining sterile conditions inside EcoFABs and mounting independent LED light systems onto EcoFABs. Detailed methods for addition of different forms of media, including soils, sand, and liquid growth media coupled to the characterization of these systems using imaging and metabolomics are described. Together, these systems enable dynamic and detailed investigation of plant and plant-microbial consortia including the manipulation of microbiome composition (including mutants), the monitoring of plant growth, root morphology, exudate composition, and microbial localization under controlled environmental conditions. We anticipate that these detailed protocols will serve as an important starting point for other researchers, ideally helping create standardized experimental systems for investigating plant-microbe interactions.

Ecosystem Fabrication EcoFAB Protocols for The Construction of Laboratory Ecosystems Designed to Study Plant-microbe Interactions

This article describes detailed protocols for ecosystem fabrication of devices (EcoFABs) that enable the studies of plants and plant-microbe interactions in highly controlled laboratory conditions.

Beneficial plant-microbe interactions offer a sustainable biological solution with the potential to boost low-input food and bioenergy production. A ...

A Strain Gauge Monitor (SGM) for Continuous Valve Gape Measurements in Bivalve Molluscs in Response to Laboratory Induced Diel-cycling Hypoxia and pH

An inexpensive, laboratory-based, strain gauge valve gape monitor (SGM) was developed to monitor the valve gape behavior of bivalve molluscs in response to diel-cycling hypoxia. A Wheatstone bridge was connected to strain gauges that were attached to the shells of oysters (Crassostrea virginica). The recorded signals allowed for the opening and closing of the bivalves to be recorded continuously over two-day periods of experimentally-induced diel-cycling hypoxia and diel-cycling changes in pH. Here, we describe a protocol for developing an inexpensive strain gauge monitor and describe, in an example laboratory experiment, how we used it to measure the valve gape behavior of Eastern oysters (C. virginica), in response to diel-cycling hypoxia and cyclical changes in pH. Valve gape was measured on oysters subjected to cyclical severe hypoxic (0.6 mg/L) dissolved oxygen conditions with and without cyclical changes in pH, cyclical mild hypoxic (1.7 mg/L) conditions and normoxic (7.3 mg/L) conditions. We demonstrate that when oysters encounter repeated diel cycles, they rapidly close their shells in response to severe hypoxia and close with a time lag to mild hypoxia. When normoxia is restored, they rapidly open again. Oysters did not respond to cyclical pH conditions superimposed on diel cycling severe hypoxia. At reduced oxygen conditions, more than one third of the oysters closed simultaneously. We demonstrate that oysters respond to diel-cycling hypoxia, which must be considered when assessing the behavior of bivalves to dissolved oxygen. The valve SGM can be used to assess responses of bivalve molluscs to changes in dissolved oxygen or contaminants. Sealing techniques to better seal the valve gape strain gauges from sea water need further improvement to increase the longevity of the sensors.

A Strain Gauge Monitor SGM for Continuous Valve Gape Measurements in Bivalve Molluscs in Response to Laboratory Induced Diel-cycling Hypoxia and pH

Understanding the behavioral responses of bivalve suspension-feeders to environmental variables, such as dissolved oxygen, can explain some ecosystem processes. We have developed an inexpensive, laboratory-based, strain gauge monitor (SGM) to measure valve gape responses of oysters, Crassostrea virginica, to diel-cycling hypoxia and cyclical pH.

An inexpensive, laboratory-based, strain gauge valve gape monitor (SGM) was developed to monitor the valve gape behavior of bivalve molluscs in response ...

Bioindication Testing of Stream Environment Suitability for Young Freshwater Pearl Mussels Using In Situ Exposure Methods

Knowledge of habitat suitability for freshwater mussels is an important step in the conservation of this endangered species group. We describe a protocol for performing in situ juvenile exposure tests within oligotrophic river catchments over one-month and three-month periods. Two methods (in both modifications) are presented to evaluate the juvenile growth and survival rate. The methods and modifications differ in value for the locality bioindication and each has its benefits as well as limitations. The sandy cage method works with a large set of individuals, but only some of the individuals are measured and the results are evaluated in bulk. In the mesh cage method, the individuals are kept and measured separately, but a low individual number is evaluated. The open water exposure modification is relatively easy to apply; it shows the juvenile growth potential of sites and can also be effective for water toxicity testing. The within-bed exposure modification needs a high workload but is closer to the conditions of a natural juvenile environment and it is better for reporting the real suitability of localities. On the other hand, more replications are needed in this modification due to its high-hyporheic environment variability.

Bioindication Testing of Stream Environment Suitability for Young Freshwater Pearl Mussels Using In Situ Exposure Methods

In situ bioindications enable determination of the suitability of an environment for endangered mussel species. We describe two methods based on the juvenile exposure of freshwater pearl mussels in cages to oligotrophic river habitats. Both methods are implemented in variants for open water and hyporheic water environments.

Knowledge of habitat suitability for freshwater mussels is an important step in the conservation of this endangered species group. We describe a protocol ...

Cultivation of Green Microalgae in Bubble Column Photobioreactors and an Assay for Neutral Lipids

There is significant interest in the study of microalgae for engineering applications such as the production of biofuels, high value products, and for the treatment of wastes. As most new research efforts begin at laboratory scale, there is a need for cost-effective methods for culturing microalgae in a reproducible manner. Here, we communicate an effective approach to culture microalgae in laboratory-scale photobioreactors, and to measure the growth and neutral lipid content of that algae. Instructions are also included on how to set up the photobioreactor system. Although the example organisms are species of Chlorella and Auxenochlorella, this system can be adapted to cultivate a wide range of microalgae, including co-cultures of algae with non-algae species. Stock cultures are first grown in bottles to produce inoculum for the photobioreactor system. Algae inoculum is concentrated and transferred to photobioreactors for cultivation in batch mode. Samples are collected daily for the optical density readings. At the end of the batch culture, cells are harvested by centrifuge, washed, and freeze dried to obtain a final dry weight concentration. The final dry weight concentration is used to create a correlation between the optical density and the dry weight concentration. A modified Folch method is subsequently used to extract total lipids from the freeze-dried biomass and the extract is assayed for its neutral lipid content using a microplate assay. This assay has been published previously but protocol steps were included here to highlight critical steps in the procedure where errors frequently occur. The bioreactor system described here fills a niche between simple flask cultivation and fully-controlled commercial bioreactors. Even with only 3-4 biological replicates per treatment, our approach to culturing algae leads to tight standard deviations in the growth and lipid assays.

Here, we present a protocol to construct lab-scale bubble column photobioreactors and use them to culture microalgae. It also provides a method for the determination of the culture growth rate and neutral lipid content.

There is significant interest in the study of microalgae for engineering applications such as the production of biofuels, high value products, and for the ...

PARbars: Cheap, Easy to Build Ceptometers for Continuous Measurement of Light Interception in Plant Canopies

Ceptometry is a technique used to measure the transmittance of photosynthetically active radiation through a plant canopy using multiple light sensors connected in parallel on a long bar. Ceptometry is often used to infer properties of canopy structure and light interception, notably leaf area index (LAI) and effective plant area index (PAIeff). Due to the high cost of commercially available ceptometers, the number of measurements that can be taken is often limited in space and time. This limits the usefulness of ceptometry for studying genetic variability in light interception, and precludes thorough analysis of, and correction for, biases that can skew measurements depending on the time of day. We developed continuously logging ceptometers (called PARbars) that can be produced for USD $75 each and yield high quality data comparable to commercially available alternatives. Here we provide detailed instruction on how to build and calibrate PARbars, how to deploy them in the field and how to estimate PAI from collected transmittance data. We provide representative results from wheat canopies and discuss further considerations that should be made when using PARbars.

Here, we present detailed instructions on how to build and calibrate research quality ceptometers (light sensors that integrate light intensity across many sensors arrayed linearly along a horizontal bar).

Ceptometry is a technique used to measure the transmittance of photosynthetically active radiation through a plant canopy using multiple light sensors ...

A Guide to Concentration Alternating Frequency Response Analysis of Fuel Cells

An experimental setup capable of generating a periodic concentration input perturbation of oxygen was used to perform concentration-alternating frequency response analysis (cFRA) on proton-exchange membrane (PEM) fuel cells. During cFRA experiments, the modulated concentration feed was sent to the cathode of the cell at different frequencies. The electric response, which can be cell potential or current depending on the control applied on the cell, was registered in order to formulate a frequency response transfer function. Unlike traditional electrochemical impedance spectroscopy (EIS), the novel cFRA methodology makes it possible to separate the contribution of different mass transport phenomena from the kinetic charge transfer processes in the frequency response spectra of the cell. Moreover, cFRA is able to differentiate between varying humidification states of the cathode. In this protocol, the focus is on the detailed description of the procedure to perform cFRA experiments. The most critical steps of the measurements and future improvements to the technique are discussed.

We present a protocol for concentration alternating frequency response analysis of fuel cells, a promising new method of studying fuel cell dynamics.

An experimental setup capable of generating a periodic concentration input perturbation of oxygen was used to perform concentration-alternating frequency ...

Isolation of Quartz Grains for Optically Stimulated Luminescence (OSL) Dating of Quaternary Sediments for Paleoenvironmental Research

Optically stimulated luminescence (OSL) dating quantifies the time since mineral grains were deposited and shielded from additional light or heat exposure, which effectively resets the luminescence clock. The systematics of OSL dating is based on the dosimetric properties of common minerals, like quartz and feldspar. The acquired luminescence with exposure to natural ionizing radiation after burial provides a depositional age for many Quaternary sedimentary systems, spanning the past 0.5 Ma. This contribution details the procedures for separating pure quartz grains of a known range of particle sizes to facilitate luminescence analysis with small or single grain aliquots. Specifically, protocols are given for the needed data and interpretations for effective OSL dating of terrestrial sediment cores or sample tubes from exposures. These cores, 5-20 m long in 1.2 m sections, are split lengthwise and crown-cut leaving 80% of core volume undisturbed, which facilitates sampling of light-protected sediment for OSL dating deep within the core. Sediment samples are then subjected to a series of physical separations to obtain a certain grain-size interval (e.g., 150-250 &#181;m). Magnetic minerals are removed in wet and dry states using magnets. A series of chemical digestions starts with soaking in H2O2 to remove organic matter, followed by HCl exposure to remove carbonate minerals, followed by density separation. Subsequently, grains are soaked in HF for 80 min and after in HCl to render solely quartz grains. The mineralogic purity (&#62;99%) of the quartz extract is quantified with grain petrographic assessment and Raman spectroscopy. Repeating this quartz isolation procedure may be necessary with sediment that contains &#60;15% quartz grains. Excitation of the purified quartz grains by LED-derived blue and IR light allows calculations of the fast and IR depletion ratios, which are metrics to assess the dominance of luminescence emissions from quartz.

Isolation of Quartz Grains for Optically Stimulated Luminescence OSL Dating of Quaternary Sediments for Paleoenvironmental Research

This protocol is for the isolation of quartz grains by size for luminescence dating of sediments. Outlined are physical cleansing and chemical digestions by soaking sequentially in H2O2, HCl, HF, and HCl again to isolate quartz grains. The quartz purity is quantified with microscopic assessment, Raman spectroscopy, and IR depletion ratio.