Name: recombinant collagen i peptide microcarriers for cell expansion and their potential use as cell delivery system in a bioreactor model
Uploaded: 2018-02-07T15:00:00
Description: Watch this Scientific Journal Video about Recombinant Collagen I Peptide Microcarriers for Cell Expansion and Their Potential Use As Cell Delivery System in a Bioreactor Model at JoVE.com

The research leading to these results has received funding from the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement n&#176; 607051 (BIO-INSPIRE). We thank Carolien van Spreuwel-Goossens from Fujifilm Manufacturing Europe B.V., for the technical assistance during RCP manufacturing, and Werner Stracke from Fraunhofer Institute for Silicate Research ISC, for assistance with the SEM analysis.

hBMSCs were isolated from the femur head of osteoarthritis patients undergoing femur head replacement surgery. The procedure was performed under the approval of the Local Ethics Committee of the University of Wuerzburg and informed consent of the patients. Primary microvascular endothelial cells were isolated from foreskin biopsies of juvenile donors. Their legal representative(s) provided full informed consent in writing. The study was approved by the local ethical board of the University of Wuerzburg (vote 182/10)....

<ol>
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One main goal of microcarrier is the expansion of cells while maintaining their differentiation in order to deliver cells to the place of need. The represented method introduce RCP microcarriers where cells were able to attach, proliferate, and colonize the microcarriers with high cell density. This was observed by live/dead staining, in which more than 90% of viable cells were detected while only few dead cells were obtained after 7 days of dynamic cultures. Likewise, the SEM images confirmed that the cells covered the ...

One general problem in tissue engineering applications is to yield a high cell mass with the correct differentiation phenotype at the location of need. The application of microcarriers to address this issue started in 1967 with increasing significance to date in fields such as orthopaedic tissue engineering for large-scale generation of skin, bone, cartilage, and tendons1. They allow the handling of adherent cultures in ways similar to that of suspension cultures2 by expanding cells on microscale three-dimensional (3D) substrates. Thereby cells experience a homogeneous nutrient supply and cell-matrix interactions that lead to better maintenance of in vivo3,4 differentiation which is often lost over time in 2D approaches5. A higher surface-to-volume ratio - eventually leading to higher cell yields6,7, higher gas and nutrient exchange rates comparing to static systems8, the possibility to regulate and subject the culture to physical stimuli9, and the potential for scaling up of the expansion process7 are further advantages. Several features such as diameter, density, porosity, surface charge, and adhesion properties10,11 distinguish the different commercially available micro- and macro-carriers. However, one of the main advantage is their delivery potential as microtissues to site defect or demand.
For applications of the microcarrier technology in bone tissue engineering, we illustrated in a previous report12 the production of a new microcarrier type constituted of a recombinant collagen I peptide (RCP, commercially available as Cellnest). This new microcarrier allows the GMP-compliant up scaling of scaffold and cell production, as needed for cell delivery in a clinical scenario. In this context, tuning of scaffold stability, degradation rate, and surface properties through proper choice of a suited crosslinking strategy allows to adapt the technique to the selected application, cell type of interest or target tissue13. In particular, the potential employment of this microcarrier as an injectable cell delivery system for therapeutic application14 makes them particularly interesting in a clinical setting.
In this paper, we therefore illustrate the culturing procedure for the isolation and expansion of human bone marrow-derived mesenchymal stromal cells (hBMSCs) and human dermal microvascular endothelial cells (HDMECs) on collagen-I-based recombinant peptide-based microcarriers, and their preparation for delivery in a clinical setting. Furthermore, we describe additional protocols useful for the maintenance of cell viability upon implantation.
Cell viability after implantation is in fact strongly dependent on vascularization15,16,17, which ensures exchange of oxygen and nutrients and facilitates waste removal. Bioreactors constitute one approach to overcome vascularization challenges in tissue engineering and maintain cell viability, through perfusion of culture medium providing thereby oxygen and nutrients18. Here, we illustrate an in vitro method to evaluate the migration capability of microvascular endothelial cells from the RCP microcarriers to a biomatrix and their ability to contribute to the de novo vascularization and angiogenesis. This biomatrix is a decellularized segment of porcine jejunum termed BioVaSc (Biological Vascularized Scaffold), rich in collagen and elastin and with preserved vascular structures, which includes a feeding artery and a draining vein19 that has been applied for implantation issues20.

<table>
	<tbody>
		<tr>
			<td>3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT)</td>
			<td>Serva Electrophoresis GmbH</td>
			<td>20395.01</td>
			<td></td>
		</tr>
		<tr>
			<td>4&#8217;,6-Diamidino-2-phenylindoldihydrochloride (DAPI)</td>
			<td>Sigma-Aldrich</td>
			<td>D9542</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid 100%</td>
			<td>Sigma-Aldrich</td>
			<td>533,001</td>
			<td></td>
		</tr>
		<tr>
			<td>Analytical balance Kern EG 2200-2NM</td>
			<td>Kern &#38; Sohn GmbH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ascorbate-2-phosphate</td>
			<td>Sigma-Aldrich</td>
			<td>A8960</td>
			<td></td>
		</tr>
		<tr>
			<td>Bioreactor</td>
			<td>Chair of Tissue Engineering and Regenerative Medicine, Wuerzburg, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bright field microscope Axiovert 40C</td>
			<td>Carl Zeiss AG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cellnest</td>
			<td>Fujifilm</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge tubes (15 mL, 50 mL)</td>
			<td>Greiner Bio-One</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Collagen R solution 0,4%</td>
			<td>Serva Electrophoresis GmbH</td>
			<td>47254.01</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM-F12</td>
			<td>Gibco</td>
			<td>11320-033</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Phosphate Buffered Saline</td>
			<td>Sigma-Aldrich</td>
			<td>D8537</td>
			<td>Modified, without calcium chloride and magnesium chloride</td>
		</tr>
		<tr>
			<td>Eosin 1%</td>
			<td>Morphisto</td>
			<td>10177.01000</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol 96%</td>
			<td>Carl Roth GmbH</td>
			<td>T171.4</td>
			<td>Denatured</td>
		</tr>
		<tr>
			<td>Fetal calf serum (FCS)</td>
			<td>Bio&#38;SELL</td>
			<td>FCS.ADD.0500</td>
			<td>not heat-inactivated</td>
		</tr>
		<tr>
			<td>Fluorescence microscope BZ-9000</td>
			<td>Keyence</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Haematoxylin</td>
			<td>Morphisto</td>
			<td>10231.01000</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexamethyldisilazane</td>
			<td>Sigma-Aldrich</td>
			<td>440191</td>
			<td>Reagent grade, &#8805;99%</td>
		</tr>
		<tr>
			<td>Incubator for bioreactor</td>
			<td>Chair of Tissue Engineering and Regenerative Medicine, Wuerzburg, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Live/Dead Cell Double Staining Kit</td>
			<td>Fluka</td>
			<td>04511KT-F</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic stirrer plate</td>
			<td>2Mag</td>
			<td>80002</td>
			<td></td>
		</tr>
		<tr>
			<td>Medium 199</td>
			<td>Sigma-Aldrich</td>
			<td>M0650</td>
			<td>10X</td>
		</tr>
		<tr>
			<td>Microplate reader 
			Tecan Infinite M200</td>
			<td>Tecan</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Needle 21G 16mm</td>
			<td>VWR</td>
			<td>613-5389</td>
			<td></td>
		</tr>
		<tr>
			<td>Papain from papaya latex</td>
			<td>Sigma-Aldrich</td>
			<td>P4762</td>
			<td>lyophilized powder, &#8805; 10 units/mg protein</td>
		</tr>
		<tr>
			<td>Paraffin</td>
			<td>Carl Roth GmbH</td>
			<td>6642.6</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Sigma-Aldrich</td>
			<td>P4333</td>
			<td></td>
		</tr>
		<tr>
			<td>Peristaltic pump</td>
			<td>Ismatec</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Quanti-iT PicoGreen dsDNA assay kit</td>
			<td>Thermo Fischer Scientific</td>
			<td>P7589</td>
			<td></td>
		</tr>
		<tr>
			<td>Histofix 4%</td>
			<td>Carl Roth GmbH</td>
			<td>P087</td>
			<td></td>
		</tr>
		<tr>
			<td>Scanning Electron Microscope Supra 25</td>
			<td>Carl Zeiss AG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide solution 1.0 N</td>
			<td>Sigma-Aldrich</td>
			<td>S2770</td>
			<td></td>
		</tr>
		<tr>
			<td>Spinner flasks (25 mL)</td>
			<td>Wheaton</td>
			<td>356879</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe 1 mL</td>
			<td>VWR</td>
			<td>720-2561</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue culture flasks (25 cm2, 75 cm2, 150 cm2)</td>
			<td>TPP Techno Plastik Products AG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan blue 0.4%</td>
			<td>Sigma-Aldrich</td>
			<td>T8154</td>
			<td></td>
		</tr>
		<tr>
			<td>VascuLife VEGF-Mv</td>
			<td>Lifeline cell technology</td>
			<td>LL-0005</td>
			<td></td>
		</tr>
	</tbody>
</table>

recombinant collagen i peptide microcarriers for cell expansion and their potential use as cell delivery system in a bioreactor model

Tissue engineering is a promising field, focused on developing solutions for the increasing demand on tissues and organs regarding transplantation purposes. The process to generate such tissues is complex, and includes an appropriate combination of specific cell types, scaffolds, and physical or biochemical stimuli to guide cell growth and differentiation. Microcarriers represent an appealing tool to expand cells in a three-dimensional (3D) microenvironment, since they provide higher surface-to volume ratios and mimic more closely the in vivo situation compared to traditional two-dimensional methods. The vascular system, supplying oxygen and nutrients to the cells and ensuring waste removal, constitutes an important building block when generating engineered tissues. In fact, most constructs fail after being implanted due to lacking vascular support. In this study, we present a protocol for endothelial cell expansion on recombinant collagen-based microcarriers under dynamic conditions in spinner flask and bioreactors, and we explain how to determine in this setting cell viability and functionality. In addition, we propose a method for cell delivery for vascularization purposes without additional detachment steps necessary. Furthermore, we provide a strategy to evaluate the cell vascularization potential in a perfusion bioreactor on a decellularized&#160;biological matrix. We believe that the use of the presented methods could lead to the development of new cell-based therapies for a large range of tissue engineering applications in the clinical practice.

As shown in Figure 1A, we obtained high number of viable cells on the RCP microcarriers after 7 days of culture, determined by live/dead staining. Those results were confirmed by SEM analysis, in which completely colonized microcarriers were observed around the pores, partly overgrowing them (Figure 1B). On the other hand, experiments in which cells were not evenly seeded resulted in several empty microcarriers. Failed experiment...

Watch this Scientific Journal Video about Recombinant Collagen I Peptide Microcarriers for Cell Expansion and Their Potential Use As Cell Delivery System in a Bioreactor Model at JoVE.com

Recombinant Collagen I Peptide Microcarriers for Cell Expansion and Their Potential Use As Cell Delivery System in a Bioreactor Model

We propose a cell expansion protocol on macroporous microcarriers and their use as delivery system in a perfusion bioreactor to seed a decellularized tissue matrix. We also include different techniques to determine cell proliferation and viability of cells cultured on microcarriers. Furthermore, we demonstrate functionality of cells after bioreactor cultures.

Tissue engineering is a promising field, focused on developing solutions for the increasing demand on tissues and organs regarding transplantation ...

The overall goal of this procedure is to expand the cells on a high available surface area and to further deliver these cells to sites of defect or demand for clinical applications. This method can help answer key questions in the tissue engineering field, such as cell expansion, cell delivery, and vascularization. The main advantage of this technique is that we can expand the cells and deliver them, without any harvesting step, into defect sites, in a biocompatible way.Visual demonstration of this method is critical, as working microcarriers and bioreactors can be complicated, at first, due to the many steps involved. Helping with the procedure will be Jihyoung Choi, a PhD student from our laboratory. One day before the experiments, set up the spinner flasks and prepare them for sterilization by autoclave.Wrap the spinner flasks with aluminum foil around the side caps separately to avoid contamination during unwrapping. Wrap the flasks with one to two layers of aluminum foil for autoclaving to minimize contamination risks after sterilization. Leave the caps of the spinner flasks loose and when possible, sterilize them in an upright position.Next, weigh the required amount of RCP macroporous microcarriers in 20 milliliters of Dulbecco's phosphate buffered saline. Let them hydrate for at least one hour before heat sterilization by autoclave. Use the bioreactor system referenced in text protocol to produce vascularized tissue equivalents.This bioreactor consists of a vessel in which the biomatrix is placed, a medium reservoir, and a pressure bottle. Connect the vessel with the medium reservoir and the pressure bottle through silicone tubes. Leave the caps loose and place the system in an autoclave plastic bag.Close the bag well and place this in a second autoclave plastic bag before sterilizing by autoclave. Let the sterilized RCP macroporous microcarriers settle to the bottom and wash them with 10 milliliters of culture medium. Repeat this process three times.Also wash the spinner flasks with 10 milliliters of culture medium. Next, add 30 milligrams of RCP macroporous microcarriers per spinner flask in eight milliliters of culture medium. Equilibrate the spinner flasks RCP macroporous microcarriers at 37 degrees Celsius and 5%carbon dioxide for 30 minutes before seeding the cells.Then, seed half a million human bone marrow derived mesenchymal stromal cells, or human dermal microvascular endothelial cells per spinner flask in two milliliters of culture medium. Place the spinner flasks on a stirrer plate at 37 degrees Celsius and 5%carbon dioxide and start stirring at 90rpm for five minutes. Then, rest for 55 minutes for a total of one hour static dynamic incubation.Repeat this incubation cycle four times. Now, add 10 milliliters of cell culture medium per spinner flask. Then start continuous stirring at 95rpm while incubating at 37 degrees Celsius and 5%carbon dioxide.One day before starting the bioreactor cultures, cut open the biomatrix longitudinally on the antimesenteric side and fix it in a previously disinfected polycarbonate frame. After detaching and counting the cells, use a two milliliter syringe to inject 10 million HDMECs in one thousand microliters of culture medium through the preserved vasculature of the biomatrix. Inject approximately 700 microliters through the arterial inlet, and approximately 300 microliters through the vein outlet.Incubate the biomatrix with injected cells at 37 degrees Celsius and 5%carbon dioxide for three hours to allow cell attachment. Following incubation, the connection of the biomatrix to the bioreactor has to be done by two individuals, taking care that the arterial and the venous pedicles are connected to the medium flow correctly. Fill the bioreactor system with 350 milliliters of the vascular endothelial growth factor, 1%penicillin streptomycin, and incubate at 37 degrees Celsius and 5%carbon dioxide.Place the frame inside the vessel of the bioreactor. Then, carefully connect the arterial and venous pedicles to the vessel. Start perfusion by connecting the bioreactor system to a peristaltic pump.Set the pressure at 10 millimeters of mercury amplitude plus minus one. Increase the pressure stepwise every hour until reaching a pressure of 100 millimeters of mercury amplitude plus minus 20. Mix 330 microliters of 0.4%Collagen R solution, 170 microliters of 0.1%acetic acid, and 50 microliters of medium M199 in a 15 milliliter Falcon tube.Keep the mixture on ice. Then, take the RCP microcarriers from the spinner flasks. Remove the culture medium completely.Next, add the volume of sodium hydroxide required to neutralize the collagen mixture. Once neutralized, immediately mix the mixture with the RCP microcarriers. It is important to allow gelation of the collagen gel before starting medium flow.Otherwise, the gel will detach and the microcarriers will be washed away from the lumen of the biomatrix. Add the collagen gel RCP microcarrier mixture on the lumen of the biomatrix. Allow gelation for 30 minutes.Then, connect the bioreactor to the peristaltic pump and set up the pressure at 100 millimeters of mercury amplitude plus minus 20. Finally, perform analysis and read outs of bioreactor cultures as described in the text protocol. Representative results of cell proliferation on microcarriers is shown by live dead staining in which many living cells can be observed on the microcarriers after seven days of dynamic cultures.These results were confirmed by scanning electron microscopy analysis showing completely colonized microcarriers after seven days of dynamic cultures. HDMECs kept their functionality after seven days of dynamic cultures on RCP microcarriers. Here, bright field microscopy reveals sprouts growing from the colonized microcarriers when cultured on a collagen gel.RFP labeled HDMECs were observed in the vascular structures of the biomatrix after 21 days of bioreactor cultures, indicating their migration from the RCP microcarriers to the biomatrix. Furthermore, after 21 days of bioreactor cultures, the scanning electron microscopy image shows that the microcarriers were in close proximity to the biomatrix. Interestingly, they are not colonized by cells anymore.After watching this video, you should have a good understanding on how to expand the cells on microcarriers to prepare them in an injectable cell delivery system for therapeutic application. Once mastered, this technique can be done in four hours. This procedure represents a promising strategy in regenerative medicine to obtain and maximize cell expansion and to deliver cells to implantation sites where they could improve vascularization for tissue engineered grafts.The implications of this technique extend toward vascularization because it can be used on any cell type for a tissue specific application in a clinical scenario. This method can also provide understanding into the potential employment of microcarriers as an injectible cell delivery system for therapeutic purposes. Don't forget that working with primary cells can be extremely hazardous, and precautions such as wearing gloves and lab coat, and working in a biosafety cabinet should always be taken when performing this procedure.After its development, this technique paved the way for researchers in the field of tissue engineering to explore cell migration in vitro which could help to understand or predict in vivo situations.

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Research

JoVE Journal

Bioengineering

Organotypic Collagen I Assay: A Malleable Platform to Assess Cell Behaviour in a 3-Dimensional Context

Cell migration is fundamental to many aspects of biology, including development, wound healing, the cellular responses of the immune system, and metastasis of tumor cells. Migration has been studied on glass coverslips in order to make cellular dynamics amenable to investigation by light microscopy. However, it has become clear that many aspects of cell migration depend on features of the local environment including its elasticity, protein composition, and pore size, which are not faithfully represented by rigid two dimensional substrates such as glass and plastic 1. Furthermore, interaction with other cell types, including stromal fibroblasts 2 and immune cells 3, has been shown to play a critical role in promoting the invasion of cancer cells. Investigation at the molecular level has increasingly shown that molecular dynamics, including response to drug treatment, of identical cells are significantly different when compared in vitro and in vivo 4. 
Ideally, it would be best to study cell migration in its naturally occurring context in living organisms, however this is not always possible. Intermediate tissue culture systems, such as cell derived matrix, matrigel, organotypic culture (described here) tissue explants, organoids, and xenografts, are therefore important experimental intermediates. These systems approximate certain aspects of an in vivo environment but are more amenable to experimental manipulation such as use of stably transfected cell lines, drug treatment regimes, long term and high-resolution imaging. Such intermediate systems are especially useful as proving grounds to validate probes and establish parameters required to image the dynamic response of cells and fluorescent reporters prior to undertaking imaging in vivo 5. As such, they can serve an important role in reducing the need for experiments on living animals.

A method is described for the preparation of a 3-dimensional matrix consisting of collagen type I and primary human fibroblasts. This organotypic gel serves as a useful substrate to assess invasive cell migration because it mimics basic features of tissue stroma and is amenable to many forms of microscopy.

Cell migration is fundamental to many aspects of biology, including development, wound healing, the cellular responses of the immune system, and ...

Rotating Cell Culture Systems for Human Cell Culture: Human Trophoblast Cells as a Model

The field of human trophoblast research aids in understanding the complex environment established during placentation. Due to the nature of these studies, human in vivo experimentation is impossible. A combination of primary cultures, explant cultures and trophoblast cell lines1 support our understanding of invasion of the uterine wall2 and remodeling of uterine spiral arteries3,4 by extravillous trophoblast cells (EVTs), which is required for successful establishment of pregnancy. Despite the wealth of knowledge gleaned from such models, it is accepted that in vitro cell culture models using EVT-like cell lines display altered cellular properties when compared to their in vivo counterparts5,6. Cells cultured in the rotating cell culture system (RCCS) display morphological, phenotypic, and functional properties of EVT-like cell lines that more closely mimic differentiating in utero EVTs, with increased expression of genes mediating invasion (e.g. matrix metalloproteinases (MMPs)) and trophoblast differentiation7,8,9. The Saint Georges Hospital Placental cell Line-4 (SGHPL-4) (kindly donated by Dr. Guy Whitley and Dr. Judith Cartwright) is an EVT-like cell line that was used for testing in the RCCS.
The design of the RCCS culture vessel is based on the principle that organs and tissues function in a three-dimensional (3-D) environment. Due to the dynamic culture conditions in the vessel, including conditions of physiologically relevant shear, cells grown in three dimensions form aggregates based on natural cellular affinities and differentiate into organotypic tissue-like assemblies10,11,12 . The maintenance of a fluid orbit provides a low-shear, low-turbulence environment similar to conditions found in vivo. Sedimentation of the cultured cells is countered by adjusting the rotation speed of the RCCS to ensure a constant free-fall of cells. Gas exchange occurs through a permeable hydrophobic membrane located on the back of the bioreactor. Like their parental tissue in vivo, RCCS-grown cells are able to respond to chemical and molecular gradients in three dimensions (i.e. at their apical, basal, and lateral surfaces) because they are cultured on the surface of porous microcarrier beads. When grown as two-dimensional monolayers on impermeable surfaces like plastic, cells are deprived of this important communication at their basal surface. Consequently, the spatial constraints imposed by the environment profoundly affect how cells sense and decode signals from the surrounding microenvironment, thus implying an important role for the 3-D milieu13.
We have used the RCCS to engineer biologically meaningful 3-D models of various human epithelial tissues7,14,15,16. Indeed, many previous reports have demonstrated that cells cultured in the RCCS can assume physiologically relevant phenotypes that have not been possible with other models10,17-21. In summary, culture in the RCCS represents an easy, reproducible, high-throughput platform that provides large numbers of differentiated cells that are amenable to a variety of experimental manipulations. 
In the following protocol, using EVTs as an example, we clearly describe the steps required to three-dimensionally culture adherent cells in the RCCS.

Traditional, two dimensional cell culture techniques often result in altered characteristics with respect to differentiation markers, cytokines and growth factors. Three-dimensional cell culture in the rotating cell culture system (RCCS) reestablishes expression of many of these factors as shown here with an extravillous trophoblast cell line.

The field of human trophoblast research aids in  understanding the complex environment established during placentation. Due to the  nature of these ...

Constructing a Collagen Hydrogel for the Delivery of Stem Cell-loaded Chitosan Microspheres

Multipotent stem cells have been shown to be extremely useful in the field of regenerative medicine1-3. However, in order to use these cells effectively for tissue regeneration, a number of variables must be taken into account. These variables include: the total volume and surface area of the implantation site, the mechanical properties of the tissue and the tissue microenvironment, which includes the amount of vascularization and the components of the extracellular matrix. Therefore, the materials being used to deliver these cells must be biocompatible with a defined chemical composition while maintaining a mechanical strength that mimics the host tissue. These materials must also be permeable to oxygen and nutrients to provide a favorable microenvironment for cells to attach and proliferate. Chitosan, a cationic polysaccharide with excellent biocompatibility, can be easily chemically modified and has a high affinity to bind with in vivo macromolecules4-5. Chitosan mimics the glycosaminoglycan portion of the extracellular matrix, enabling it to function as a substrate for cell adhesion, migration and proliferation. In this study we utilize chitosan in the form of microspheres to deliver adipose-derived stem cells (ASC) into a collagen based three-dimensional scaffold6. An ideal cell-to-microsphere ratio was determined with respect to incubation time and cell density to achieve maximum number of cells that could be loaded. Once ASC are seeded onto the chitosan microspheres (CSM), they are embedded in a collagen scaffold and can be maintained in culture for extended periods. In summary, this study provides a method to precisely deliver stem cells within a three dimensional biomaterial scaffold.

A major hurdle in current stem cell therapies is determining the most effective method to deliver these cells to host tissues. Here, we describe a chitosan-based delivery method that is efficient and simple in approach, while allowing adipose-derived stem cells to maintain their multipotency.

Multipotent stem cells have been shown to be extremely useful in the field of regenerative medicine1-3. However, in order to use these cells effectively ...

Skin Tattooing As A Novel Approach For DNA Vaccine Delivery

Nucleic acid-based vaccination is a topic of growing interest, especially plasmid DNA (pDNA) encoding immunologically important antigens. After the engineered pDNA is administered to the vaccines, it is transcribed and translated into immunogen proteins that can elicit responses from the immune system. Many ways of delivering DNA vaccines have been investigated; however each delivery route has its own advantages and pitfalls. Skin tattooing is a novel technique that is safe, cost-effective, and convenient. In addition, the punctures inflicted by the needle could also serve as a potent adjuvant. Here, we a) demonstrate the intradermal delivery of plasmid DNA encoding enhanced green fluorescent protein (pCX-EGFP) in a mouse model using a tattooing device and b) confirm the effective expression of EGFP in the skin cells using confocal microscopy.

Skin tattooing is a potent and safe way to delivery DNA vaccine intradermally. Here, a DNA plasmid encoding EGFP is delivered by tattooing to the skin of a laboratory mouse, and the expression of EGFP in the skin cells is then inspected by confocal microscopy.

Nucleic acid-based vaccination is a topic of growing interest, especially plasmid DNA (pDNA) encoding immunologically important antigens. After the ...

Microfluidic Picoliter Bioreactor for Microbial Single-cell Analysis: Fabrication, System Setup, and Operation

In this protocol the fabrication, experimental setup and basic operation of the recently introduced microfluidic picoliter bioreactor (PLBR) is described in detail. The PLBR can be utilized for the analysis of single bacteria and microcolonies to investigate biotechnological and microbiological related questions concerning, e.g.&#160;cell growth, morphology, stress response, and metabolite or protein production on single-cell level. The device features continuous media flow enabling constant environmental conditions for perturbation studies, but in addition allows fast medium changes as well as oscillating conditions to mimic any desired environmental situation. To fabricate the single use devices, a silicon wafer containing sub micrometer sized SU-8 structures served as the replication mold for rapid polydimethylsiloxane casting. Chips were cut, assembled, connected, and set up onto a high resolution and fully automated microscope suited for time-lapse imaging, a powerful tool for spatio-temporal cell analysis. Here, the biotechnological platform organism Corynebacterium glutamicum&#160;was seeded into the PLBR and cell growth and intracellular fluorescence were followed over several hours unraveling time dependent population heterogeneity on single-cell level, not possible with conventional analysis methods such as flow cytometry. Besides insights into device fabrication, furthermore, the preparation of the preculture, loading, trapping of bacteria, and the PLBR cultivation of single cells and colonies is demonstrated. These devices will add a new dimension in microbiological research to analyze time dependent phenomena of single bacteria under tight environmental control. Due to the simple and relatively short fabrication process the technology can be easily adapted at any microfluidics lab and simply tailored towards specific needs.

In this protocol the fabrication, setup and basic operation of a microfluidic picoliter bioreactor (PLBR) for single-cell analysis of prokaryotic microorganisms is introduced. Industrially relevant microorganisms were analyzed as proof of principle allowing insights into growth rate, morphology, and phenotypic heterogeneity over certain time periods, hardly possible with conventional methods.

In this protocol the fabrication, experimental setup and basic operation of the recently introduced microfluidic picoliter bioreactor (PLBR) is described ...

Cell Squeezing as a Robust, Microfluidic Intracellular Delivery Platform

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This technology has shown potential in addressing previously challenging applications; including, delivery to primary immune cells, cell reprogramming, carbon nanotube, and quantum dot delivery. This vector-free microfluidic platform relies on mechanical disruption of the cell membrane to facilitate cytosolic delivery of the target material. Herein, we describe the detailed method of use for these microfluidic devices including, device assembly, cell preparation, and system operation. This delivery approach requires a brief optimization of device type and operating conditions for previously unreported applications. The provided instructions are generalizable to most cell types and delivery materials as this system does not require specialized buffers or chemical modification/conjugation steps. This work also provides recommendations on how to improve device performance and trouble-shoot potential issues related to clogging, low delivery efficiencies, and cell viability.

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This protocol provides detailed steps on how to use the system for a broad range of applications.

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This ...

Analysis of Cell Migration within a Three-dimensional Collagen Matrix

The ability to migrate is a hallmark of various cell types and plays a crucial role in several physiological processes, including&#160;embryonic development, wound healing, and immune responses. However, cell migration is also a key mechanism in cancer enabling these cancer cells to detach from the primary tumor to start metastatic spreading. Within the past years various cell migration assays have been developed to analyze the migratory behavior of different cell types. Because the locomotory behavior of cells markedly differs between a two-dimensional (2D) and three-dimensional (3D) environment it can be assumed that the analysis of the migration of cells that are embedded within a 3D environment would yield in more significant cell migration data. The advantage of the described 3D collagen matrix migration assay is that cells are embedded within a physiological 3D network of collagen fibers representing the major component of the extracellular matrix. Due to time-lapse video microscopy real cell migration is measured allowing the determination of several migration parameters as well as their alterations in response to pro-migratory factors or inhibitors. Various cell types could be analyzed using this technique, including lymphocytes/leukocytes, stem cells, and tumor cells. Likewise, also cell clusters or spheroids could be embedded within the collagen matrix concomitant with analysis of the emigration of single cells from the cell cluster/ spheroid into the collagen lattice. We conclude that the 3D collagen matrix migration assay is a versatile method to analyze the migration of cells within a physiological-like 3D environment.

Cell migration is a biological phenomenon that is involved in a plethora of physiological, such as wound healing and immune responses, and pathophysiological processes, like cancer. The 3D-collagen matrix migration assay is a versatile tool to analyze the migratory properties of different cell types within in a 3D physiological-like environment.

The ability to migrate is a hallmark of various cell types and plays a crucial role in several physiological processes, including&#160;embryonic ...

Cultivation of Mammalian Cells Using a Single-use Pneumatic Bioreactor System

Recent advances in mammalian, insect, and stem cell cultivation and scale-up have created tremendous opportunities for new therapeutics and personalized medicine innovations. However, translating these advances into therapeutic applications will require in vitro systems that allow for robust, flexible, and cost effective bioreactor systems. There are several bioreactor systems currently utilized in research and commercial settings; however, many of these systems are not optimal for establishing, expanding, and monitoring the growth of different cell types. The culture parameters most challenging to control in these systems include, minimizing hydrodynamic shear, preventing nutrient gradient formation, establishing uniform culture medium aeration, preventing microbial contamination, and monitoring and adjusting culture conditions in real-time. Using a pneumatic single-use bioreactor system, we demonstrate the assembly and operation of this novel bioreactor for mammalian cells grown on micro-carriers. This bioreactor system eliminates many of the challenges associated with currently available systems by minimizing hydrodynamic shear and nutrient gradient formation, and allowing for uniform culture medium aeration. Moreover, the bioreactor&#8217;s software allows for remote real-time monitoring and adjusting of the bioreactor run parameters. This bioreactor system also has tremendous potential for scale-up of adherent and suspension mammalian cells for production of a variety therapeutic proteins, monoclonal antibodies, stem cells, biosimilars, and vaccines.

Using a pneumatic bioreactor, we demonstrate the assembly, operation, and performance of this single-use bioreactor system for the growth of mammalian cells.

Recent advances in mammalian, insect, and stem cell cultivation and scale-up have created tremendous opportunities for new therapeutics and personalized ...

Minced Tissue in Compressed Collagen: A Cell-containing Biotransplant for Single-staged Reconstructive Repair

Conventional techniques for cell expansion and transplantation of autologous cells for tissue engineering purposes can take place in specially equipped human cell culture facilities. These methods include isolation of cells in single cell suspension and several laborious and time-consuming events before transplantation back to the patient. Previous studies suggest that the body itself could be used as a bioreactor for cell expansion and regeneration of tissue in order to minimize ex vivo manipulations of tissues and cells before transplanting to the patient. The aim of this study was to demonstrate a method for tissue harvesting, isolation of continuous epithelium, mincing of the epithelium into small pieces and incorporating them into a three-layered biomaterial. The three-layered biomaterial then served as a delivery vehicle, to allow surgical handling, exchange of nutrition across the transplant, and a controlled degradation. The biomaterial consisted of two outer layers of collagen and a core of a mechanically stable and slowly degradable polymer. The minced epithelium was incorporated into one of the collagen layers before transplantation. By mincing the epithelial tissue into small pieces, the pieces could be spread and thereby the propagation of cells was stimulated. After the initial take of the transplants, cell expansion and reorganization would take place and extracellular matrix mature to allow ingrowth of capillaries and nerves and further maturation of the extracellular matrix. The technique minimizes ex vivo manipulations and allow cell harvesting, preparation of autograft, and transplantation to the patient as a simple one-stage intervention. In the future, tissue expansion could be initiated around a 3D mold inside the body itself, according to the specific needs of the patient. Additionally, the technique could be performed in an ordinary surgical setting without the need for sophisticated cell culturing facilities.

Tissue engineering often includes in vitro expansion in order to create autografts for tissue regeneration. In this study a method for tissue expansion, regeneration, and reconstruction in vivo was developed in order to minimize the processing of cells and biological materials outside the body.

Conventional techniques for cell expansion and transplantation of autologous cells for tissue engineering purposes can take place in specially equipped ...

Fabrication of Extracellular Matrix-derived Foams and Microcarriers as Tissue-specific Cell Culture and Delivery Platforms

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus of this article is on the methods for fabricating ECM-derived porous foams and microcarriers for use as biologically-relevant substrates in advanced 3D in vitro cell culture models or as pro-regenerative scaffolds and cell delivery systems for tissue engineering and regenerative medicine. Using decellularized tissues or purified insoluble collagen as a starting material, the techniques can be applied to synthesize a broad array of tissue-specific bioscaffolds with customizable geometries. The approach involves mechanical processing and mild enzymatic digestion to yield an ECM suspension that is used to fabricate the three-dimensional foams or microcarriers through controlled freezing and lyophilization procedures. These pure ECM-derived scaffolds are highly porous, yet stable without the need for chemical crosslinking agents or other additives that may negatively impact cell function. The scaffold properties can be tuned to some extent by varying factors such as the ECM suspension concentration, mechanical processing methods, or synthesis conditions. In general, the scaffolds are robust and easy to handle, and can be processed as tissues for most standard biological assays, providing a versatile and user-friendly 3D cell culture platform that mimics the native ECM composition. Overall, these straightforward methods for fabricating customized ECM-derived foams and microcarriers may be of interest to both biologists and biomedical engineers as tissue-specific cell-instructive platforms for in vitro and in vivo applications.

The tissue-specific extracellular matrix (ECM) is a key mediator of cell function. This article describes methods for synthesizing pure ECM-derived foams and microcarriers that are stable in culture without the need for chemical crosslinking for applications in advanced 3D in vitro cell culture models or as pro-regenerative bioscaffolds.

Cell function is mediated by interactions with the extracellular matrix (ECM), which has complex tissue-specific composition and architecture. The focus ...