Name: selective cell elimination from mixed 3d culture using a near infrared photoimmunotherapy technique
Uploaded: 2016-03-14T14:00:00
Description: Watch this Scientific Journal Video about Selective Cell Elimination from Mixed 3D Culture Using a Near Infrared Photoimmunotherapy Technique at JoVE.com

This research was supported by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, Center for Cancer Research.

Note: The following protocol describes the necessary steps to eliminate specific cells using NIR-PIT. Controls and other details about NIR-PIT and cell viability can be found elsewhere18.
1. Conjugation of IR700 to Monoclonal Antibodies (mAb)
<ol>
	<li>Prepare mAb of interest at 2-5 mg/ml in 0.1 M Na2HPO4 (pH 8.6) solution.</li>
	<li>Mix 6.8 nmol of mAb with 30.8 nmol of 10 mM IR700 in 0.1 M Na2HPO4 solution (pH 8.6) in a microcentrifuge tube and incubate at...

<ol>
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H., Saha, K., Jaenisch, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pluripotency+and+cellular+reprogramming:+facts,+hypotheses,+unresolved+issues.">Pluripotency and cellular reprogramming: facts, hypotheses, unresolved issues.</a> Cell. 143 (4), 508-525 (2010).</li><li>Lee, M. -. O., Moon, S. 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=Inhibition+of+pluripotent+stem+cell-derived+teratoma+formation+by+small+molecules.">Inhibition of pluripotent stem cell-derived teratoma formation by small molecules.</a> Proc. Natl. Acad. Sci. U.S.A. 110 (35), 3281-3290 (2013).</li><li>Miura, K., Okada, 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=Variation+in+the+safety+of+induced+pluripotent+stem+cell+lines.">Variation in the safety of induced pluripotent stem cell lines.</a> Nat. Biotechnol. 27 (8), 743-745 (2009).</li><li>Tang, C., Lee, A. S., 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=An+antibody+against+SSEA-5+glycan+on+human+pluripotent+stem+cells+enables+removal+of+teratoma-forming+cells.">An antibody against SSEA-5 glycan on human pluripotent stem cells enables removal of teratoma-forming cells.</a> Nat. Biotechnol. 29 (9), 829-834 (2011).</li><li>Mitsunaga, M., Ogawa, M., Kosaka, N., Rosenblum, L. T., Choyke, P. 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L., Kobayashi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Near+Infrared+Photoimmunotherapy+in+the+Treatment+of+Disseminated+Peritoneal+Ovarian+Cancer.">Near Infrared Photoimmunotherapy in the Treatment of Disseminated Peritoneal Ovarian Cancer.</a> Mol. Cancer Ther. 14 (8), 141-150 (2014).</li><li>Sato, K., Choyke, P. L., Kobayashi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoimmunotherapy+of+Gastric+Cancer+Peritoneal+Carcinomatosis+in+a+Mouse+Model.">Photoimmunotherapy of Gastric Cancer Peritoneal Carcinomatosis in a Mouse Model.</a> PloS one. 9 (11), 113276 (2014).</li><li>Sato, K., Nagaya, T., Choyke, P. 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L., Kobayashi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+cell+elimination+in+vitro+and+in+vivo+from+tissues+and+tumors+using+antibodies+conjugated+with+a+near+infrared+phthalocyanine.">Selective cell elimination in vitro and in vivo from tissues and tumors using antibodies conjugated with a near infrared phthalocyanine.</a> RSC Adv. 5, 25105-25114 (2015).</li><li>Watanabe, R., Hanaoka, 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=Photoimmunotherapy+Targeting+Prostate-Specific+Membrane+Antigen:+Are+Antibody+Fragments+as+Effective+as+Antibodies.">Photoimmunotherapy Targeting Prostate-Specific Membrane Antigen: Are Antibody Fragments as Effective as Antibodies.</a> J. Nucl. Med. 56 (1), 140-144 (2014).</li><li>Nakajima, T., Sano, K., Choyke, P. 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We demonstrate a method of specific cell elimination from a mixed 3D cell culture without damage to non-target cells by using NIR-PIT. So far, there is no practical method of cell elimination once the tissue is established or after transplantation. Thus, NIR-PIT is a promising method to accomplish this. This technique could also be utilized in vivo18,22, since APCs show similar pharmacokinetics as mAb itself. The target cell type can be adapted with various APC. Various antibodies or antibody...

Eliminating specific cells without damaging other cells is extremely difficult, especially in established tissue, and there is an urgent need for a cell elimination method in the tissue engineering field. Nowadays in the field of regenerative medicine, tissue cultures using embryonic stem cells (ES), pluripotent stem cells (PSCs), or induced pluripotent stem cell (iPS) are promising materials1-3.
Although this tissue regeneration is promising, contamination with unwanted cells is a major concern. Moreover, there is a safety concern of tumorigenicity after transplantation4,5. Although many studies have focused on these issues to eliminate specific cells, especially in regenerative medicine6-8, no practical method has been developed.
Near infrared photoimmunotherapy (NIR-PIT) is a treatment based on an antibody-photoabsorber conjugate (APC). An APC consists of a cell-specific monoclonal antibody (mAb) and a photoabsorber, IR700. IR700 is a hydrophilic silica-phthalocyanine derivative and does not induce phototoxicity by itself9. IR700 is covalently conjugated to the antibody via amide residues on the side chain of lysine molecules. The APC binds target molecules on the cell membrane and then induces nearly immediate cell necrosis after exposure to NIR light at 690 nm. During the exposure to NIR-light, the cellular membrane ruptures leading to cell death9-14. NIR-PIT has proven to be effective with multiple antibodies or antibody fragments, including anti-EGFR, anti-HER2, anti-PSMA, anti-CD25, anti-mesothelin, anti-GPC3, and anti-CEA15-21. Therefore, NIR-PIT can be used against a wide variety of target molecules. Moreover, NIR-PIT is a well-controlled treatment that allows selective treatment of specific regions by restricting the NIR-light irradiation18,22.
Here, we present a method of specific cell elimination using NIR-PIT from mixed 3D cultures.

<table border="0" cellpadding="0" cellspacing="0" width="1083">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:424px;">IRDye 700DX Ester Infrared Dye</td>
			<td style="width:364px;">LI-COR Bioscience (Lincoln, NE, USA)</td>
			<td style="width:191px;">929-70011</td>
			<td style="width:104px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Na2HPO4</td>
			<td>SIGMA-ALDRICH (St. Louis, MO, USA)</td>
			<td>S9763</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sephadex G25 column (PD-10)&#160;</td>
			<td>GE Healthcare (Piscataway, NJ, USA)</td>
			<td>17-0851-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Coomassie (bradford) Plus protein assay</td>
			<td>Thermo Fisher Scientific Inc (Waltham, MA, USA)</td>
			<td>PI-23200</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Perfecta3D 96-Well hanging Drop Plates</td>
			<td>3D Biomatrix Inc (Ann Arbor, MI, USA)</td>
			<td>HDP1096-8</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Optical power meter</td>
			<td>Thorlabs (Newton, NJ, USA)</td>
			<td>PM100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LED: L690-66-60</td>
			<td>Marubeni America Co. (Santa Clara, CA, USA)</td>
			<td>L690-66-60</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vectibix (panitumumab)</td>
			<td>Amgen (Thousand Oaks, CA, USA)</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">35mm glass bottom dish, dish size 35mm, well size 10mm</td>
			<td>Cellvis (Mountain View, CA, USA)</td>
			<td>D35-10-0-N</td>
			<td></td>
		</tr>
	</tbody>
</table>

selective cell elimination from mixed 3d culture using a near infrared photoimmunotherapy technique

Recent developments in tissue engineering offer innovative solutions for many diseases. For example, tissue engineering using induced pluripotent stem cell (iPS) emerged as a new method in regenerative medicine. Although this tissue regeneration is promising, contamination with unwanted cells during tissue cultures is a major concern. Moreover, there is a safety concern regarding tumorigenicity after transplantation. Therefore, there is an urgent need for eliminating specific cells without damaging other cells that need to be protected, especially in established tissue. Here, we present a method for specific cell elimination from a mixed 3D cell culture in vitro with near infrared photoimmunotherapy (NIR-PIT) without damaging non-targeted cells. This technique enables the elimination of specific cells from mixed cell cultures or tissues.

To optically monitor the effect of NIR-PIT, the A431 cell line, which overexpresses EGFR, was genetically modified to also express GFP and luciferase (A431-luc-GFP). As a non-target of NIR-PIT, the Balb/3T3 cell line was optically modified to express RFP (3T3-RFP). The APC, panitumumab-IR700 (pan-IR700), was synthesized. Mixed spheroids, which were composed of various ratios of cells (A431-luc-GFP and 3T3-RFP) were fabricated according to this protocol (Figure 1). Repeate...

Watch this Scientific Journal Video about Selective Cell Elimination from Mixed 3D Culture Using a Near Infrared Photoimmunotherapy Technique at JoVE.com

Selective Cell Elimination from Mixed 3D Culture Using a Near Infrared Photoimmunotherapy Technique

Eliminating specific cells without damaging other cells is extremely difficult, especially in established tissue, yet there is an urgent need for a cell elimination method in the tissue engineering field. Here, we present a method for specific cell elimination from a mixed 3D cell culture using near infrared photoimmunotherapy (NIR-PIT).

Recent developments in tissue engineering offer innovative solutions for many diseases. For example, tissue engineering using induced pluripotent stem ...

The overall goal of this experimental procedure is to demonstrate the elimination of specific cells of interest from a mixed 3D cell culture using near infrared photoimmunotherapy. This method can help answer key questions in the tissue-engineering field about regenerating medicine. The main advantage of this technique that it can be used against a variety of target molecules and that the treatment can be restricted to specific lesions of interest.Thus can minimize the side effect. For IR700 conjugation to monoclonal antibodies, incubate the antibodies of interest with IR700 in Disodium Phosphate in a microcentrefuge tube at room temperature for one hour covered in aluminum foil. At the end of the incubation, wash a PD10 column two times with 15 milliliters of PBS.Then, load the antibody solution onto the column and purify the mixture by PBS elution according to the manufacturer's instructions. To confirm the number of fluoro-4 molecules conjugated to each monoclonal antibody molecule, use a spectrophotometer to determine the monoclonal antibody protein concentration. Then, store the conjugate at 4-degree Celsius.To prepare the mixed 3D cell culture, add 1 milliliter of sterile water into the plate reservoir section of a 96-well hanging drop plate. Then, plate various ratios of the cell types of interest in the appropriate cell culture medium at at least 5, 000 cells per 50 microliters of medium per well for five to seven days in a humidified incubator at 37-degree Celsius and 5%carbon dioxide. Change the culture medium every two days and observe the morphology and size of the spheroids daily with an inverted bright-field microscope at 10 to 40 times magnification.When the spheroids have reached 400 to 600 microns in diameter, replace the hanging drop plate medium with antibody photoabsorber conjugate-containing medium, and return the plate to the incubator for six hours. At the end of the incubation, wash the spheroids two times with fresh phenol red free-culture medium. Then use a 200-microliter pipette tip with a cut-off end to transfer one spheroid at a time into individual glass-bottom 50-millimeter dishes containing 100 microliters of fresh phenol red free-culture medium per dish.Use the inverted microscope to observe changes in the spheroid morphology. To irradiate the spheroids, place a light-emitting diode no higher than 5 inches above the glass-bottom dishes. And use an optical power meter to confirm the emission of a 670 to 710 nanometer wavelength at 2 joules per centimeter squared.After the NIR infrared photoimmunotherapy, transfer the spheroids into a new hanging drop plate with 50 microliters of fresh-culture medium per well for one day in the cell-culture incubator. Then, using another 200-microliter pipette tip with a cut-off end, gently transfer the spheroids into new glass-bottom dishes containing 100 microliters of phenol red free-culture medium, and assess the optical reporter expression under the flourescent microscope. Finally, detect the dead cells by the addition of propidium iodide to the medium.Or by the loss of cytoplasmic GFP flourescence. In this representative experiment, mixed spheroids composed of various ratios of A431-luc-GFP and 3T3-RFP cells were prepared as just demonstrated. Repeated NIR infrared photoimmunotherapy was then performed with the incubation of panitumumab-IR700 as illustrated.And the target cell elimination was monitored through the assessment of the flourescent and luciferase activities within the hanging drop cultures. Once mastered, this technique can be completed in one hour if it is performed properly. While attempting this procedure, it's important to remember that light energy decreases according to inverse-square law.

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Research

JoVE Journal

Bioengineering

A Simple Hanging Drop Cell Culture Protocol for Generation of 3D Spheroids

Studies of cell-cell cohesion and cell-substratum adhesion have historically been performed on monolayer cultures adherent to rigid substrates. Cells within a tissue, however, are typically encased within a closely packed tissue mass in which cells establish intimate connections with many near-neighbors and with extracellular matrix components. Accordingly, the chemical milieu and physical forces experienced by cells within a 3D tissue are fundamentally different than those experienced by cells grown in monolayer culture. This has been shown to markedly impact cellular morphology and signaling. Several methods have been devised to generate 3D cell cultures including encapsulation of cells in collagen gels1or in biomaterial scaffolds2. Such methods, while useful, do not recapitulate the intimate direct cell-cell adhesion architecture found in normal tissues. Rather, they more closely approximate culture systems in which single cells are loosely dispersed within a 3D meshwork of ECM products. Here, we describe a simple method in which cells are placed in hanging drop culture and incubated under physiological conditions until they form true 3D spheroids in which cells are in direct contact with each other and with extracellular matrix components. The method requires no specialized equipment and can be adapted to include addition of any biological agent in very small quantities that may be of interest in elucidating effects on cell-cell or cell-ECM interaction. The method can also be used to co-culture two (or more) different cell populations so as to elucidate the role of cell-cell or cell-ECM interactions in specifying spatial relationships between cells. Cell-cell cohesion and cell-ECM adhesion are the cornerstones of studies of embryonic development, tumor-stromal cell interaction in malignant invasion, wound healing, and for applications to tissue engineering. This simple method will provide a means of generating tissue-like cellular aggregates for measurement of biomechanical properties or for molecular and biochemical analysis in a physiologically relevant model.

We describe a simple, rapid method of generating 3D tissue-like spheroids and their potential application to quantify differences in cell-cell interactions.

Studies of cell-cell cohesion and cell-substratum adhesion have historically been performed on monolayer cultures adherent to rigid substrates. Cells ...

Preparation of 3D Fibrin Scaffolds for Stem Cell Culture Applications

Stem cells are found in naturally occurring 3D microenvironments in vivo, which are often referred to as the stem cell niche 1. Culturing stem cells inside of 3D biomaterial scaffolds provides a way to accurately mimic these microenvironments, providing an advantage over traditional 2D culture methods using polystyrene as well as a method for engineering replacement tissues 2. While 2D tissue culture polystrene has been used for the majority of cell culture experiments, 3D biomaterial scaffolds can more closely replicate the microenvironments found in vivo by enabling more accurate establishment of cell polarity in the environment and possessing biochemical and mechanical properties similar to soft tissue.3 A variety of naturally derived and synthetic biomaterial scaffolds have been investigated as 3D environments for supporting stem cell growth. While synthetic scaffolds can be synthesized to have a greater range of mechanical and chemical properties and often have greater reproducibility, natural biomaterials are often composed of proteins and polysaccharides found in the extracelluar matrix and as a result contain binding sites for cell adhesion and readily support cell culture. Fibrin scaffolds, produced by polymerizing the protein fibrinogen obtained from plasma, have been widely investigated for a variety of tissue engineering applications both in vitro and in vivo 4. Such scaffolds can be modified using a variety of methods to incorporate controlled release systems for delivering therapeutic factors 5. Previous work has shown that such scaffolds can be used to successfully culture embryonic stem cells and this scaffold-based culture system can be used to screen the effects of various growth factors on the differentiation of the stem cells seeded inside 6,7.
 This protocol details the process of polymerizing fibrin scaffolds from fibrinogen solutions using the enzymatic activity of thrombin. The process takes 2 days to complete, including an overnight dialysis step for the fibrinogen solution to remove citrates that inhibit polymerization. These detailed methods rely on fibrinogen concentrations determined to be optimal for embryonic and induced pluripotent stem cell culture. Other groups have further investigated fibrin scaffolds for a wide range of cell types and applications - demonstrating the versatility of this approach 8-12.

This work details the preparation of 3D fibrin scaffolds for culturing and differentiating plutipotent stem cells. Such scaffolds can be used to screen the effects of various biological compounds on stem cell behavior as well as modified to contain drug delivery systems.

Stem cells are found in naturally occurring 3D microenvironments in vivo, which are often referred to as the stem cell niche 1. Culturing stem cells ...

A Novel Method for Localizing Reporter Fluorescent Beads Near the Cell Culture Surface for Traction Force Microscopy

PA gels have long been used as a platform to study cell traction forces due to ease of fabrication and the ability to tune their elastic properties. When the substrate is coated with an extracellular matrix protein, cells adhere to the gel and apply forces, causing the gel to deform. The deformation depends on the cell traction and the elastic properties of the gel. If the deformation field of the surface is known, surface traction can be calculated using elasticity theory. Gel deformation is commonly measured by embedding fluorescent marker beads uniformly into the gel. The probes displace as the gel deforms. The probes near the surface of the gel are tracked. The displacements reported by these probes are considered as surface displacements. Their depths from the surface are ignored. This assumption introduces error in traction force evaluations. For precise measurement of cell forces, it is critical for the location of the beads to be known. We have developed a technique that utilizes simple chemistry to confine fluorescent marker beads, 0.1 and 1 &#181;m in diameter, in PA gels, within 1.6 &#956;m of the surface. We coat a coverslip with poly-D-lysine (PDL) and fluorescent beads. PA gel solution is then sandwiched between the coverslip and an adherent surface. The fluorescent beads transfer to the gel solution during curing. After polymerization, the PA gel contains fluorescent beads on a plane close to the gel surface.

Traditional techniques for fabricating polyacrylamide (PA) gels containing fluorescent probes involve sandwiching a gel between an adherent surface and a glass slide. Here, we show that coating this slide with poly-D-lysine (PDL) and fluorescent probes localizes the probes to within 1.6 &#181;m from the gel surface.

PA gels have long been used as a platform to study cell traction forces due to ease of fabrication and the ability to tune their elastic properties. When ...

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials.

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

The use of fluorophores for in vivo imaging can be greatly limited by opsonization, rapid clearance, low detection sensitivity and cytotoxic effects on the host. Encapsulation of fluorophores in liposomes by film hydration and extrusion leads to fluorescence quenching and protection which enables in vivo imaging with high detection sensitivity.

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous ...

Tunable Hydrogels from Pulmonary Extracellular Matrix for 3D Cell Culture

Here we present a method for establishing multiple component cell culture hydrogels for in vitro lung cell culture. Beginning with healthy en bloc lung tissue from porcine, rat, or mouse, the tissue is perfused and submerged in subsequent chemical detergents to remove the cellular debris. Histological comparison of the tissue before and after processing confirms removal of over 95% of double stranded DNA and alpha galactosidase staining suggests the majority of cellular debris is removed. After decellularization, the tissue is lyophilized and then cryomilled into a powder. The matrix powder is digested for 48 hr in an acidic pepsin digestion solution and then neutralized to form the pregel solution. Gelation of the pregel solution can be induced by incubation at 37 &#176;C and can be used immediately following neutralization or stored at 4 &#176;C for up to two weeks. Coatings can be formed using the pregel solution on a non-treated plate for cell attachment. Cells can be suspended in the pregel prior to self-assembly to achieve a 3D culture, plated on the surface of a formed gel from which the cells can migrate through the scaffold, or plated on the coatings. Alterations to the strategy presented can impact gelation temperature, strength, or protein fragment sizes. Beyond hydrogel formation, the hydrogel stiffness may be increased using genipin.

This is a method to create a 3-dimensional cell culture scaffold from pulmonary extracellular matrix. Intact lung is processed into hydrogels that can support the growth of cells in three-dimensions.

Here we present a method for establishing multiple component cell culture hydrogels for in vitro lung cell culture. Beginning with healthy en bloc lung ...

Bioprinting of Cartilage and Skin Tissue Analogs Utilizing a Novel Passive Mixing Unit Technique for Bioink Precellularization

Bioprinting is a powerful technique for the rapid and reproducible fabrication of constructs for tissue engineering applications. In this study, both cartilage and skin analogs were fabricated after bioink pre-cellularization utilizing a novel passive mixing unit technique. This technique was developed with the aim to simplify the steps involved in the mixing of a cell suspension into a highly viscous bioink. The resolution of filaments deposited through bioprinting necessitates the assurance of uniformity in cell distribution prior to printing to avoid the deposition of regions without cells or retention of large cell clumps that can clog the needle. We demonstrate the ability to rapidly blend a cell suspension with a bioink prior to bioprinting of both cartilage and skin analogs. Both tissue analogs could be cultured for up to 4 weeks. Histological analysis demonstrated both cell viability and deposition of tissue specific extracellular matrix (ECM) markers such as glycosaminoglycans (GAGs) and collagen I respectively.

Cartilage and skin analogs were bioprinted using a nanocellulose-alginate based bioink. The bioinks were cellularized prior to printing via a single step passive mixing unit. The constructs were demonstrated to be uniformly cellularized, have high viability, and exhibit favorable markers of differentiation.

Bioprinting is a powerful technique for the rapid and reproducible fabrication of constructs for tissue engineering applications. In this study, both ...

Fabrication of Custom Agarose Wells for Cell Seeding and Tissue Ring Self-assembly Using 3D-Printed Molds

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease modeling. Self-assembled tissues offer advantages over scaffold-based tissue engineering, such as enhanced matrix deposition, strength, and function. However, there are few available methods for fabricating 3D tissues without seeding cells on or within a supporting scaffold. Previously, we developed a system for fabricating self-assembled tissue rings by seeding cells into non-adhesive agarose wells. A polydimethylsiloxane (PDMS) negative was first cast in a machined polycarbonate mold, and then agarose was gelled in the PDMS negative to create ring-shaped cell seeding wells. However, the versatility of this approach was limited by the resolution of the tools available for machining the polycarbonate mold. Here, we demonstrate that 3D-printed plastic can be used as an alternative to machined polycarbonate for fabricating PDMS negatives. The 3D-printed mold and revised mold design is simpler to use, inexpensive to produce, and requires significantly less agarose and PDMS per cell seeding well. We have demonstrated that the resulting agarose wells can be used to create self-assembled tissue rings with customized diameters from a variety of different cell types. Rings can then be used for mechanical, functional, and histological analysis, or for fabricating larger and more complex tubular tissues.

This protocol describes a platform for fabricating self-assembled tissue rings in variable sizes using a customized 3D-printed plastic mold. PDMS negatives are cured in the 3D-printed mold; then agarose is cast in the cured PDMS negatives. Cells are seeded into the resulting agarose wells where they aggregate into tissue rings.

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease ...

Construction of a Multilayered Mesenchymal Stem Cell Sheet with a 3D Dynamic Culture System

Stem cell therapy shows a promising future in regenerating injured organ and tissues, and the cell sheet technique has been developed to improve the low cell retention and poor survival within the target zone. However, during the in vitro construction process, a solution for maintaining stem cell bioactivity and increasing the cell amount within the cell sheet is urgently needed. Here, this protocol presents a method for constructing a multilayered cell sheet with favorable stem cell bioactivity and optimal operability. Decellularized porcine pericardium (DPP) is prepared by phospholipase A2 (PLA2) decellularization method as the cell sheet scaffold, and rat bone marrow mesenchymal stem cells (BMSCs) are isolated and expanded as the seeded cells. The temporary multilayered cell sheet structure is constructed by using RAD16-I peptide hydrogel. Finally, the cell sheet is cultured with a dynamic perfusion system to stabilize the three-dimensional (3D) structure, and the cell sheet could be obtained following a 48-hour culture in vitro. This protocol provides an efficient and feasible method for constructing a multilayered stem cell sheet, and the cell sheet could be developed as a favorable stem cell therapy product in the future.

This article provides an efficient and feasible method for constructing multilayered stem cell sheets with favorable stem cell property.

Stem cell therapy shows a promising future in regenerating injured organ and tissues, and the cell sheet technique has been developed to improve the low ...

Synthesis of Near-Infrared Emitting Gold Nanoclusters for Biological Applications

Over the past decade, fluorescent gold nanoclusters (AuNCs) have witnessed growing popularity in biological applications and enormous efforts have been devoted to their development. In this protocol, a recently developed, facile method for preparation of water soluble, biocompatible, and colloidally stable near-infrared emitting AuNCs have been described in detail. This room-temperature, bottom-up chemical synthesis provides easily functionalizable AuNCs capped with thioctic acid and thiol-modified polyethylene glycol in aqueous solution. The synthetic approach requires neither organic solvents or additional ligand exchange nor extensive knowledge of synthetic chemistry to reproduce. The resulting AuNCs offer free surface carboxylic acids, which can be functionalized with various biological molecules bearing a free amine group without adversely affecting the photoluminescent properties of the AuNCs. A quick, reliable procedure for flow cytometric quantification and confocal microscopic imaging of AuNC uptake by HeLa cells also been described. Due to the large Stokes shift, proper setting of filters in flow cytometry and confocal microscopy is necessary for efficient detection of near-infrared photoluminescence of AuNCs.

A reliable and easily reproducible method for preparation of functionalizable, near-infrared emitting photoluminescent gold nanoclusters and their direct detection inside HeLa cells by flow cytometry and confocal laser scanning microscopy is described.

Over the past decade, fluorescent gold nanoclusters (AuNCs) have witnessed growing popularity in biological applications and enormous efforts have been ...

A Human 3D Extracellular Matrix-Adipocyte Culture Model for Studying Matrix-Cell Metabolic Crosstalk

The extracellular matrix (ECM) plays a central role in regulating tissue homeostasis, engaging in crosstalk with cells and regulating multiple aspects of cellular function. The ECM plays a particularly important role in adipose tissue function in obesity, and alterations in adipose tissue ECM deposition and composition are associated with metabolic disease in mice and humans. Tractable in vitro models that permit dissection of the roles of the ECM and cells in contributing to global tissue phenotype are sparse. We describe a novel 3D in vitro model of human ECM-adipocyte culture that permits study of the specific roles of the ECM and adipocytes in regulating adipose tissue metabolic phenotype. Human adipose tissue is decellularized to isolate ECM, which is subsequently repopulated with preadipocytes that are then differentiated within the ECM into mature adipocytes. This method creates ECM-adipocyte constructs that are metabolically active and retain characteristics of the tissues and patients from which they are derived. We have used this system to demonstrate disease-specific ECM-adipocyte crosstalk in human adipose tissue. This culture model provides a tool for dissecting the roles of the ECM and adipocytes in contributing to global adipose tissue metabolic phenotype and permits study of the role of the ECM in regulating adipose tissue homeostasis.

We describe a 3D human extracellular matrix-adipocyte in vitro culture system that permits dissection of the roles of the matrix and adipocytes in contributing to adipose tissue metabolic phenotype.

The extracellular matrix (ECM) plays a central role in regulating tissue homeostasis, engaging in crosstalk with cells and regulating multiple aspects of ...