Name: alginate encapsulation of pluripotent stem cells using a co-axial nozzle
Uploaded: 2015-07-02T10:00:00.000+00:00
Duration: 7 min 13 s
Description: Watch this Scientific Journal Video about Alginate Encapsulation of Pluripotent Stem Cells Using a Co-axial Nozzle at JoVE.com

This research was supported by the S-Innovation project of the Japan Science and technology Agency (JST), the Graduate Program for Leaders in Life Innovation (GPLLI) of the University of Tokyo, and the Research Fellowship for Young Scientists of Japan Society for the Promotion of Science. We thank nac Image Technology Inc. for taking movies using a hi-speed camera.

1.準備材料<ol><li> 10mMのHEPES緩衝液を準備します。 RTでpHを7.0に調整し、0.9％に塩化ナトリウムを加えます。 </li><li> 1.1で調製したHEPES緩衝生理食塩水を混合することにより、5％アルギン酸塩溶液および10mM EDTA溶液を準備します。 RTでpHを7.0に調整します。 </li><li> 121℃で20分間、試薬（1.1、1.2）をオートクレーブ。 </li><li> 90、10％ES-修飾FBSおよびマイトマイシンC10μg/ mlのを含むDMEM内でインキュベートすることにより、フィーダー細胞として処理され、2.0×10 6マウス胚性線維芽細胞（MEF）細胞、 - 1.2層状ゼラチンコーティングされた60ミリメートルの料理を準備します - 120分。 </li><li>マウス人工多能性幹（iPS）皿上の細胞を5mlの存在ES修飾FBS、2-メルカプトエタノール、非必須アミノ酸、50μM、および抗生物質（20％を含むDMEM高グルコース中のフィーダー細胞を維持しますペニシリンGナトリウム、硫酸ストレプトマイシンを100μg/ mlと100単位/ ml、およびamphoteriの250 ng / mlでCINのB）。 </li><li>シード4×10 5ゼラチンコーティングされた60ミリメートル皿にiPS細胞と37℃、5％CO 2でそれらをインキュベートします。インキュベーション中に、毎日培地を変更します。 3の後- 4日間培養し、37℃で0.02％EDTA、5％CO 2を含む0.05％トリプシンの500μlの1分間細胞をトリプシン処理。その後、培養皿を10回タップすることで細胞を剥離。 </li><li> （3回千μlをマイクロピペットでピペッティングにより単一細胞に解離マウスiPS細胞を以下）ES-修飾FBSおよび抗生物質の10％を含むDMEM 2.5 mlを加え3分間160×gで遠心分離細胞懸濁液、上清を除去し、細胞をカウント。細胞計数の後、ゼラチンコートディッシュに回収した細胞を再シードし、MEF細胞からiPS細胞を単離するために30分間インキュベートします。細胞の計数した後（通常は1 - 3×10 6細胞/皿を収集することができます）、上の4×10 5 iPS細胞を再シード皿。 </li></ol>アルギン酸ハイドロゲルカプセルに2細胞のカプセル化<ol><li> 1.5および1.6に記載の方法と同様の方法により細胞を収集します。 3分間160×gで遠心分離した後、三回HEPES緩衝生理食塩水でのiPS細胞ペレットを洗浄します。 HEPES緩衝化生理食塩水で細胞を再懸濁した後、それ以外の場合はノズルを詰まらせる可能性が大きな凝集体を除去するために40μmのセルストレーナーを通して細胞懸濁液を濾過します。 </li><li> HEPES緩衝生理食塩水内の細胞懸濁液2mlを、5％ALG-ナトリウム溶液3mlを混合します。最後に、3％のALG-Na溶液中で細胞懸濁液5mlを得られます。細胞密度は、望ましくは10以上6細胞/ mlです。 </li><li> 5ミリリットルシリンジに細胞懸濁液を収集した後、注射器に同軸ノズル（ 図1A、B）をインストールし、シリンジポンプに設定してください。同軸ノズルの外針を通してN 2ガ ​​ス流量（リットル/分より低い）を放出し、内側ノズルを通して細胞懸濁液を追い出します。 </li><li> 0.5％のCaCl 2溶液250ml中に液滴を収集し、10を待つ- 60〜90 rpmで攪拌しながら、ゲル化のために20分。 </li></ol>アルギン酸カプセルの3処理（オプション） <ol><li> 0.05％、37℃で5分間、5％CO 2（w / v）のポリ-L-リジン（PLL）溶液をALG-カルシウムカプセルをインキュベートします。 </li><li> HEPES緩衝生理食塩水でカプセルを洗浄した後、それらの表面上の電荷を中和するために10％FBSを含むDMEM中でそれらを培養します。コーティングされたカプセル（ 図1C）として、それらを利用しています。 </li><li> 5分間、10mMのEDTAを含むHEPES緩衝生理食塩水でカプセルをインキュベートします。 EDTA処理したカプセルは、中空カプセル（ 図1C）として利用されます。 </li></ol> 4.文化アルギン酸カプセルの細胞を収集<ol><li> 37℃および5％CO 2で振とうしながら75 rpmでカプセル化された細胞をインキュベート10日間。 </li><li>収集し、10分間CO 2を 37℃で、10mMのEDTAでカプセルをインキュベートし、5％。 3分間1,000×gで遠心分離することにより、PLL処理なしのアルギン酸カプセルから細胞を収集します。 </li><li> 5分間5,000×gで - アルギン酸塩カプセルはPLLで処理している場合は、シリンジに取り付けられた1000でそれを遠心針で上下にピペッティング10回の周りによってALG-PLL膜を破ります。針の直径は、カプセルサイズ25 G（260μm）の針が、この実験で使用されているよりも低くなければならない（600ミクロン） </li><li>あなたは、細胞からのmRNAのサンプルを収集したい場合は、遠心分離した後、壊れたALG-PLL膜から厳密に細胞ペレットを収集します。残りのALG-PLL膜は、おそらくmRNA精製を防ぎます。 </li></ol>

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The authors have nothing to disclose.

<html>カプセル化培養物を直接懸濁培養物と比較することができます。浮遊培養は、カプセル化方法よりも多能性幹細胞を大量に得るための簡単​​な方法です。しかし、懸濁培養中の細胞の凝集を制御することは依然として困難です。カプセル化方法において、細胞凝集は、カプセル内に限定されるので、十分に制御することができます。以前の刊行物は、大きな細胞塊が自由懸濁培養7で登場し、一方カプセル化された細胞は、均一な大きさの凝集体を形成することを示しました。さらに、以前の報告は、強力な攪拌がPS細胞の直接懸濁培養における細胞死を引き起こすことを実証しました。このように制限された撹拌速度を必要とします。対照的に、カプセル化もサスペンション条件下で剪断応力から細胞を保護することができます。懸濁液中の細胞を成長させる際のカプセル化方法は、したがって、運転条件の自由度を可能にします。 「ove_content&gt;はカプセル化は、量産プロセスの変更だけでなく、幹細胞研究の両方のための有用なツールである。幹細胞のカプセル化は、細胞外マトリックスおよび増殖因子を含む、幹細胞のニッチを研究するのに有用である。いくつかの研究者がいることを実証しましたVEGF共役アガロースヒドロゲルにマウスES細胞のカプセル化は、血液前駆細胞8への細胞の分化を促進しました。 この記事では、同軸ノズルとN 2の流れを利用して簡単にサイズ制御ALG-カルシウムカプセルにマウスiPS細胞をカプセル化する方法を示しています。このような蠕動ポンプ9と電気電圧10等の様々なツールを使用して、いくつかのカプセル化プロセスがあるが、N 2フローを使用してカプセル化は、他の方法よりも簡単で安全な方法です。さらに、この方法は、（約600ミクロンよりも大きい）蠕動ポンプを用いる方法よりも小さなカプセルを形成することができます（約3mmより大きい）。大きなカプセルは完全にゲル化のために長い時間がかかるとのCaCl 2での長時間のインキュベーションは、おそらく細胞特性に影響を与えます。また、大きなカプセルはまた、おそらく、グルコースや酸素などの栄養素や廃棄物の物質移動の問題を抱えています。したがって、N 2流量（600 -1000ミクロン）によって形成されたカプセルの大きさは、内部の細胞培養に理想的なサイズです。 この方法は、小さなカプセルを準備し、正確にサイズを制御するのに適していません。そのため、液滴の分解のため、この方法は、500ミクロンよりも小さいカプセルを製造するのに適していません。また、カプセルの大きさを決定することができる唯一の​​視覚的観察は、従って、この方法により、カプセルの大きさを制御することは困難です。この場合、マイクロ流体デバイスの使用は、おそらく、これらの問題を解決することができる11。 ALG-のNaゲルはCaCl 2をsolutを満たした直後しかし、時には目詰まりがマイクロデバイスで発生しますイオン。 アルギン酸塩は、その高粘度の化学的修飾には適していないが、PEGのように、カプセル化のために使用することも困難であり、ヒドロゲルを有するハイブリッドカプセルを形成することができます。以前の刊行物は、RGDペプチドコンジュゲートPEG-ALGハイブリッドヒドロゲルカプセルでマウスiPS細胞のカプセル化は、細胞増殖を12向上したことを示しました。化学修飾なしで、単にハイドロゲルカプセルへの細胞のカプセル化は、分泌因子を保持することにより、幹細胞のニッチを修正することが予想されます。実際、以前の研究はmicrobioreactorに保持分泌成長因子は、幹細胞の運命13,14を制御するのに有効であったことを実証しました。 カプセルからの細胞の収集は依然として多能性幹細胞の大量生産へのカプセル化方法の適用に関する未解決の問題です。以前の報告は、PLLコーティングがkに必要であることを示しました7内部のEEPマウスiPS細胞。 ALG-カルシウムハイドロゲルカプセルはよくこのようなPLL（プロトコル3.1から3.2）のようなポリカチオンでコーティングされている場合は、いずれかの酵素またはキレート試薬によってカプセルを破壊することが困難になります。この場合、針でピペッティングなどの機械的な方法は、（プロトコル4.3）が必要です。遠心分離は、おそらく高いG力に細胞生存率に影響を与える可能性があるが、回収された細胞は、より多い5,000×gで遠心分離で破断膜から単離することができます。このように、静かに細胞から破片を除去するだけでなく、カプセルを破壊する技術は、カプセル化技術を開発する上で重要です。いくつかのさらなる発展を細胞の大量生産にこの方法を適用するために必要ですが、カプセル化は、大量生産や幹細胞研究の両方のための有望な技術です。

Induced pluripotent stem cells (iPS cells) are currently the source of intense research due to their role in regenerative medicine. However, huge amounts of cells are required for tissue regeneration. For instance approximately one billion pancreatic cells required for a type 1 diabetic patient1. However, conventional dish culture is only able to obtain 1 &#215; 105 cells/cm2, thus requiring 1 m2 of culture area to obtain enough stem cell-derived pancreatic cells to treat a type 1 diabetic patient. The development of a system for the mass-culture of pluripotent stem cells, such as microcarrier2 and suspension culture is therefore required for regenerative medicine. Suspension culture represents a promising method of mass culture but controlling the aggregation of cells is challenging in direct suspension cultures of human iPS cells3. Indeed, suspended cells are exposed to shear stress, which causes cell damage3 or differentiation4.
Research into hydrogel-based encapsulation has been conducted to solve problems associated with suspension culture. In hydrogel capsules, cells are protected from the flow of the medium. Previous reports have documented the use of various types of hydrogel, including agarose5, PEG6, and alginate (Alg), for cellular encapsulation. Alg-Ca hydrogel is one of the most useful hydrogels for cell encapsulation because Alg&#8722;Ca hydrogel is formed immediately after dropping alginate solution into a CaCl2 solution and is also readily digested by enzymes or chelating reagents. 
Here, we have established a stable alginate encapsulation process for iPS cells using a co-axial nozzle. By using N2 gas flow for forming droplets, it is possible to encapsulate cells into uniform capsules without the need for other reagents such as oil. In this method, the flow rate of N2 and concentration of both CaCl2 and alginate are the major operating conditions affecting the size, shape, and uniformity of capsules. This report demonstrates the optimization of these operating conditions through the use of a hi-speed camera and a microscope.

<table><tbody><tr><td>Mouse embryo fibroblast</td><td>Cell Biolabs</td><td>SNL 76/7</td><td></td></tr><tr><td>Mouse induced pluripotent stem cell</td><td>RIKEN Bio resorce centre</td><td>iPS-MEF-Ng-20D-17</td><td></td></tr><tr><td>DMEM high-glucose</td><td>GIBCO</td><td>11995</td><td></td></tr><tr><td>ES qualified&amp;nbsp; FBS</td><td>GIBCO</td><td>16141079</td><td></td></tr><tr><td>Antibacterial Antibiotics</td><td>GIBCO</td><td>15240</td><td></td></tr><tr><td>Nonessential Amino Acid</td><td>GIBCO</td><td>11140</td><td></td></tr><tr><td>2-mercaptoethanol</td><td>GIBCO</td><td>21985-023</td><td></td></tr><tr><td>ESGRO Leukemia Inhibitory Factor</td><td>Merck Millipore</td><td>ESG1107</td><td></td></tr><tr><td>Trypsin/EDTA</td><td>GIBCO</td><td>25300</td><td></td></tr><tr><td>26 G/16 G needle</td><td>Hoshiseido</td><td></td><td></td></tr><tr><td>10 ml Syringe</td><td>TERUMO</td><td>SS-10ESZ</td><td></td></tr><tr><td>Sodium&amp;nbsp; Chloride</td><td>Wako</td><td>191-01665</td><td></td></tr><tr><td>HEPES</td><td>SIGMA</td><td>H4034</td><td></td></tr><tr><td>Sodium Alginate</td><td>Wako</td><td>194-09955</td><td></td></tr><tr><td>Calcium Chloride</td><td>Wako</td><td>039-00475</td><td></td></tr><tr><td>Poly-L-lysine (MW = 15,000 - 30,000)</td><td>SIGMA</td><td>P7890</td><td></td></tr><tr><td>EDTA</td><td>DOJINDO</td><td>345-01865</td><td></td></tr><tr><td>Sylinge pump</td><td>AS ONE</td><td></td><td></td></tr><tr><td>Microscope</td><td>Olympus</td><td>IX71</td><td></td></tr><tr><td>Microscope</td><td>Leica</td><td>DM IRB</td><td></td></tr><tr><td>Hispeed camera</td><td>nac image technology</td><td>Memrecam HX-3</td><td></td></tr></tbody></table>

alginate encapsulation of pluripotent stem cells using a co-axial nozzle

Pluripotent stem cells (PS cells) are the focus of intense research due to their role in regenerative medicine and drug screening. However, the development of a mass culture system would be required for using PS cells in these applications. Suspension culture is one promising culture method for the mass production of PS cells, although some issues such as controlling aggregation and limiting shear stress from the culture medium are still unsolved. In order to solve these problems, we developed a method of calcium alginate (Alg-Ca) encapsulation using a co-axial nozzle. This method can control the size of the capsules easily by co-flowing N2 gas. The controllable capsule diameter must be larger than 500 &#181;m because too high a flow rate of N2 gas causes the breakdown of droplets and thus heterogeneous-sized capsules. Moreover, a low concentration of Alg-Na and CaCl2 causes non-spherical capsules. Although an Alg-Ca capsule without a coating of Alg-PLL easily dissolves enabling the collection of cells, they can also potentially leak out from capsules lacking an Alg-PLL coating. Indeed, an alginate-PLL coating can prevent cellular leakage but is also hard to break. This technology can be used to research the stem cell niche as well as the mass production of PS cells because encapsulation can modify the micro-environment surrounding cells including the extracellular matrix and the concentration of secreted factors.

プロトコル2.5で、排出されたアルギン酸塩溶液は直ちに放出（ - H図2A）の後に球状をなします。懸濁液を1L / minより低いN 2流量で排出された場合、液滴の大きさが均一（ 図2I）です。 N 2流量は、1L /分よりも大きい場合には、液滴（ 図2G、白矢印）を分解し、液滴の大きさは、不均一（ 図2J）となります。これを考えると、この方法を使用して500ミクロン未満の液滴を調製することは困難です。 ALG-NA（3％以上）の濃度が十分に（ 図3E-H、K、I）であればゲル化工程（プロトコル2.4）では、ALG-Naが塩化カルシウム溶液中の球状ALG-カルシウムカプセルを形成される液滴。しかし、ALG-ナトリウム（3％未満）の低濃度は、非球面せ、カプセルの非滑らかな形状（ 図3A-D、I）、そのコー​​ティングプロセスで問題があります。 ALG-Na濃度が十分でない場合でも、球状カプセルは、 塩化カルシウム濃度（ 図3J）を増加させることによって形成することができます。のCaCl 2の高すぎる濃度は、細胞増殖および生存率を低下させるしかし、CaCl 2を50mMの周りに（データは示していない）カプセル化に適しています。 塩化カルシウム溶液中に滴下した後、必要に応じて、あなたは、ゲル化のために、数分待つことができるが、 塩化カルシウムで長すぎるインキュベーションは時々細胞の成長に影響を与えるので、我々は、 塩化カルシウム溶液からカプセルを拾ってお勧めします。時には、濃度が十分であっても、非球面形状のカプセルを得ます。携帯ペレットを洗浄すると、ALG-Na溶液中に細胞を再懸濁する前に、十分ではないためと考えられます。血清などの残留試薬は、おそらくゲル化を防止します。 カプセル化された細胞は、カプセルが、携帯漏れで成長することができます（ 図に矢印図4（a））は、ALG-PLLコーティング（ 図4A）なしでカプセルの中に発生する可能性があります。細胞が互いに凝集し、各中空カプセル（ 図4C）で単一の球状凝集体を形成するのに対し、マウスiPS細胞の場合、細胞は、各ALG-カルシウムカプセル（ 図4B）で円盤状の凝集体を形成します。初期細胞密度は、カプセルが、低い細胞密度（10 5細胞/ mlゲル）中の凝集体の大きさに影響する（データは示さず）まで成長する障害が発生していません。従って、10 6細胞/ mlゲルを封入することが望ましいです。 ALG-PLLコーティングは、酵素または化学薬品で溶解することは困難であるが、カプセルから細胞を採取するには、ALG-カルシウムハイドロゲルは、アルギン酸リアーゼまたはキレート試薬で溶解させることができます。 ALG-PLLは、したがって、物理的に、例えば、ピペット操作で破壊されるべきです。壊れた膜は、遠心分離によって細胞から分離することができます。 カプセル化システムとカプセルの図1の画像。（A）クリーンベンチ上のALG-カルシウムのカプセル化のためのカプセル化システムのイメージ。 （B）カプセル化のための同軸ノズルの概略画像。 （C）本報告書で得られたカプセルの3つの異なるタイプ。 <a href="https://www.jove.com/files/ftp_upload/52835/52835fig1large.jpg" target="_blank">この図の拡大版を表示するには、こちらをクリックしてください。</a> <img alt="図2" src="/files/ftp_upload/52835/52835fig2.jpg" /> N 2中の同軸ノズルから、3％ALG-Na溶液の液滴形成の様子（I、J） -図2カプセルの形態でN 2フローの効果の連続画像（H A）。1 L /分で流れる（A - D、I）及び2リットル/分（E - H、J）。連続画像は、ハイスピー​​ドカメラで撮影しました。ハイドロゲルカプセルは、0.5％のCaCl 2に形成されている。 <a href="https://www.jove.com/files/ftp_upload/52835/52835fig2large.jpg" target="_blank">この図の拡大版を表示するには、こちらをクリックしてください。</a> <img alt="図3" src="/files/ftp_upload/52835/52835fig3.jpg" /> ALG-Naを図3.効果とのCaCl 2濃度カプセルの形態での連続画像（A - H）。外観- ALG-Naを（I L）は、 塩化カルシウム溶液中にゲル化液滴。 、 - （H E）の50mMのCaCl 2溶液中でゲル化されている- （D A）および3％の連続画像では、ALG-ナトリウム、2％の異なる濃度を有する液滴。連続画像はハイテクによって捕捉されます-speedカメラ。外観画像は、ALG-ナトリウム、2％（L、J）と3％（K、L）とのCaCl 2、50mMの（L、K）および500 mMの異なる濃度により形成されたALG-カルシウムカプセルの形態学的差異を示します（J、L）。 <a href="https://www.jove.com/files/ftp_upload/52835/52835fig3large.jpg" target="_blank">この図の拡大版を表示するには、こちらをクリックしてください。</a> <img alt="図4" src="/files/ftp_upload/52835/52835fig4.jpg" /> カプセルにカプセル化マウスiPS細胞凝集体の図4形態 4、6、8、10日間培養したiPS細胞凝集体の顕微鏡写真画像（1 - 4それぞれ）のカプセルの3種類で：（A）裸（ B）コーティングされ、および（C）中空カプセル。 <a href="https://www.jove.com/files/ftp_upload/52835/52835fig4large.jpg" target="_blank">クリックしてください</a>ここで、この図の拡大版を表示します。

Watch this Scientific Journal Video about Alginate Encapsulation of Pluripotent Stem Cells Using a Co-axial Nozzle at JoVE.com

Alginate Encapsulation of Pluripotent Stem Cells Using a Co-axial Nozzle

We established a method of encapsulating pluripotent stem cells (PS cells) into alginate hydrogel capsules using a co-axial nozzle. This prevents cells from aggregating excessively and limits the shear stress experienced by cells in suspension culture. The technique is applicable to the mass production of PS cells as well as research on stem cell niche.

同軸ノズルを用いて多能性幹細胞のアルギン酸カプセル化

Pluripotent stem cells (PS cells) are the focus of intense research due to their role in regenerative medicine and drug screening.  However, the ...

alginate-encapsulation-pluripotent-stem-cells-using-co-axial

Nanyang Technological University

Research

JoVE Journal

Developmental Biology

12.6K ビュー.  The University of Tokyo. We established a method of encapsulating pluripotent stem cells (PS cells) into alginate hydrogel capsules using a co-axial nozzle. This prevents cells from aggregating excessively and limits the shear stress experienced by cells in suspension culture. The technique is applicable to the mass production of PS cells as well as research on stem cell niche.

ビデオ: Alginate Encapsulation of Pluripotent Stem Cells Using a Co-axial Nozzle

Alginate Microcapsule as a 3D Platform for Propagation and Differentiation of Human Embryonic Stem Cells (hESC) to Different Lineages

Human embryonic stem cells (hESC) are emerging as an attractive alternative source for cell replacement therapy since they can be expanded in culture indefinitely and differentiated to any cell types in the body. Various types of biomaterials have also been used in stem cell cultures to provide a microenvironment mimicking the stem cell niche1-3. The latter is important for promoting cell-to-cell interaction, cell proliferation, and differentiation into specific lineages as well as tissue organization by providing a three-dimensional (3D) environment4 such as encapsulation. The principle of cell encapsulation involves entrapment of living cells within the confines of semi-permeable membranes in 3D cultures2. These membranes allow for the exchange of nutrients, oxygen and stimuli across the membranes, whereas antibodies and immune cells from the host that are larger than the capsule pore size are excluded5. Here, we present an approach to culture and differentiate hESC DA neurons in a 3D microenvironment using alginate microcapsules. We have modified the culture conditions2 to enhance the viability of encapsulated hESC. We have previously shown that the addition of p160-Rho-associated coiled-coil kinase (ROCK) inhibitor, Y-27632 and human fetal fibroblast-conditioned serum replacement medium (hFF-CM) to the 3D platform significantly enhanced the viability of encapsulated hESC in which the cells expressed definitive endoderm marker genes1. We have now used this 3D platform for the propagation of hESC and efficient differentiation to DA neurons. Protein and gene expression analyses after the final stage of DA neuronal differentiation showed an increased expression of tyrosine hydroxylase (TH), a marker for DA neurons, &gt;100 folds after 2 weeks. We hypothesized that our 3D platform using alginate microcapsules may be useful to study the proliferation and directed differentiation of hESC to various lineages. This 3D system also allows the separation of feeder cells from hESC during the process of differentiation and also has potential for immune-isolation during transplantation in the future.

Alginate Microcapsule as a 3D Platform for Propagation and Differentiation of Human Embryonic Stem Cells hESC to Different Lineages

We have optimized a microencapsulation technique as an effective 3D platform for propagation and differentiation of embryonic stem cells to endoderm and dopaminergic (DA) neurons. It also provides an opportunity for immune-isolation of cells from the host during transplantation. This platform can be adapted for other cell types.

異なる系統にヒト胚性幹細胞（hESCの）の伝播との差別化のための3Dプラットフォームとしてのアルギン酸マイクロカプセル

Human embryonic stem cells (hESC) are emerging as an attractive alternative source for cell replacement therapy since they can be expanded in culture ...

生物工学

High Throughput Single-cell and Multiple-cell Micro-encapsulation

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 &mu;m polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency Pk=1 of 83.7% and a double-particle encapsulation efficiency Pk=2 of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. 
Introduction 
Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify signals from bioreactor products. Drops also provide the ability to re-merge drops into larger aqueous samples or with other drops for intercellular signaling studies.1,2 The reduction in dilution implies stronger detection signals for higher accuracy measurements as well as the ability to reduce potentially costly sample and reagent volumes.3 Encapsulation of cells in drops has been utilized to improve detection of protein expression,4 antibodies,5,6 enzymes,7 and metabolic activity8 for high throughput screening, and could be used to improve high throughput cytometry.9 Additional studies present applications in bio-electrospraying of cell containing drops for mass spectrometry10 and targeted surface cell coatings.11 Some applications, however, have been limited by the lack of ability to control the number of cells encapsulated in drops. Here we present a method of ordered encapsulation12 which increases the demonstrated encapsulation efficiencies for one and two cells and may be extrapolated for encapsulation of a larger number of cells.
To achieve monodisperse drop generation, microfluidic "flow focusing" enables the creation of controllable-size drops of one fluid (an aqueous cell mixture) within another (a continuous oil phase) by using a nozzle at which the streams converge.13 For a given nozzle geometry, the drop generation frequency f and drop size can be altered by adjusting oil and aqueous flow rates Qoil and Qaq. As the flow rates increase, the flows may transition from drop generation to unstable jetting of aqueous fluid from the nozzle.14 
When the aqueous solution contains suspended particles, particles become encapsulated and isolated from one another at the nozzle. For drop generation using a randomly distributed aqueous cell suspension, the average fraction of drops Dk containing k cells is dictated by Poisson statistics, where Dk = &lambda;k exp(-&lambda;)/(k!) and &lambda; is the average number of cells per drop. The fraction of cells which end up in the "correctly" encapsulated drops is calculated using Pk = (k x Dk)/&Sigma;(k' x Dk'). The subtle difference between the two metrics is that Dk relates to the utilization of aqueous fluid and the amount of drop sorting that must be completed following encapsulation, and Pk relates to the utilization of the cell sample. As an example, one could use a dilute cell suspension (low &lambda;) to encapsulate drops where most drops containing cells would contain just one cell. While the efficiency metric Pk would be high, the majority of drops would be empty (low Dk), thus requiring a sorting mechanism to remove empty drops, also reducing throughput.15
Combining drop generation with inertial ordering provides the ability to encapsulate drops with more predictable numbers of cells per drop and higher throughputs than random encapsulation. Inertial focusing was first discovered by Segre and Silberberg16 and refers to the tendency of finite-sized particles to migrate to lateral equilibrium positions in channel flow. Inertial ordering refers to the tendency of the particles and cells to passively organize into equally spaced, staggered, constant velocity trains. Both focusing and ordering require sufficiently high flow rates (high Reynolds number) and particle sizes (high Particle Reynolds number).17,18 Here, the Reynolds number Re =uDh/&nu; and particle Reynolds number Rep =Re(a/Dh)2, where u is a characteristic flow velocity, Dh [=2wh/(w+h)] is the hydraulic diameter, &nu; is the kinematic viscosity, a is the particle diameter, w is the channel width, and h is the channel height. Empirically, the length required to achieve fully ordered trains decreases as Re and Rep increase. Note that the high Re and Rep requirements (for this study on the order of 5 and 0.5, respectively) may conflict with the need to keep aqueous flow rates low to avoid jetting at the drop generation nozzle. Additionally, high flow rates lead to higher shear stresses on cells, which are not addressed in this protocol. The previous ordered encapsulation study demonstrated that over 90% of singly encapsulated HL60 cells under similar flow conditions to those in this study maintained cell membrane integrity.12 However, the effect of the magnitude and time scales of shear stresses will need to be carefully considered when extrapolating to different cell types and flow parameters. The overlapping of the cell ordering, drop generation, and cell viability aqueous flow rate constraints provides an ideal operational regime for controlled encapsulation of single and multiple cells.
Because very few studies address inter-particle train spacing,19,20 determining the spacing is most easily done empirically and will depend on channel geometry, flow rate, particle size, and particle concentration. Nonetheless, the equal lateral spacing between trains implies that cells arrive at predictable, consistent time intervals. When drop generation occurs at the same rate at which ordered cells arrive at the nozzle, the cells become encapsulated within the drop in a controlled manner. This technique has been utilized to encapsulate single cells with throughputs on the order of 15 kHz,12 a significant improvement over previous studies reporting encapsulation rates on the order of 60-160 Hz.4,15 In the controlled encapsulation work, over 80% of drops contained one and only one cell, a significant efficiency improvement over Poisson (random) statistics, which predicts less than 40% efficiency on average.12
In previous controlled encapsulation work,12 the average number of particles per drop &lambda; was tuned to provide single-cell encapsulation. We hypothesize that through tuning of flow rates, we can efficiently encapsulate any number of cells per drop when &lambda; is equal or close to the number of desired cells per drop. While single-cell encapsulation is valuable in determining individual cell responses from stimuli, multiple-cell encapsulation provides information relating to the interaction of controlled numbers and types of cells. Here we present a protocol, representative results using polystyrene microspheres, and discussion for controlled encapsulation of multiple cells using a passive inertial ordering channel and drop generation nozzle.

Combining monodisperse drop generation with inertial ordering of cells and particles, we describe a method to encapsulate a desired number of cells or particles in a single drop at kHz rates. We demonstrate efficiencies twice exceeding those of unordered encapsulation for single- and double-particle drops.

ハイスループットマイクロカプセル化シングルセルと複数セル

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement ...

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering 

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development of constructs for tissue engineering. This environment better mimics what cells observe in vivo, compared to standard tissue culture, due to the tissue-like properties and 3D environment. Synthetic polymeric hydrogels are water-swollen networks that can be designed to be stable or to degrade through hydrolysis or proteolysis as new tissue is deposited by encapsulated cells. A wide variety of polymers have been explored for these applications, such as poly(ethylene glycol) and hyaluronic acid. Most commonly, the polymer is functionalized with reactive groups such as methacrylates or acrylates capable of undergoing crosslinking through various mechanisms. In the past decade, much progress has been made in engineering these microenvironments - e.g., via the physical or pendant covalent incorporation of biochemical cues - to improve viability and direct cellular phenotype, including the differentiation of encapsulated stem cells (Burdick et al.).
The following methods for the 3D encapsulation of cells have been optimized in our and other laboratories to maximize cytocompatibility and minimize the number of hydrogel processing steps. In the following protocols (see Figure 1 for an illustration of the procedure), it is assumed that functionalized polymers capable of undergoing crosslinking are already in hand; excellent reviews of polymer chemistry as applied to the field of tissue engineering may be found elsewhere (Burdick et al.) and these methods are compatible with a range of polymer types. Further, the Michael-type addition (see Lutolf et al.) and light-initiated free radical (see Elisseeff et al.) mechanisms focused on here constitute only a small portion of the reported crosslinking techniques. Mixed mode crosslinking, in which a portion of reactive groups is first consumed by addition crosslinking and followed by a radical mechanism, is another commonly used and powerful paradigm for directing the phenotype of encapsulated cells (Khetan et al., Salinas et al.).

Cellular Encapsulation in 3D Hydrogels for Tissue Engineering

We present protocols for the 3-dimensional (3D) encapsulation of cells within synthetic hydrogels. The encapsulation procedure is outlined for two commonly used methods of crosslinking (michael-type addition and light-initiated free radical mechanisms), as well as a number of techniques for assessing encapsulated cell behavior.

組織工学のための3Dハイドロゲルの細胞のカプセル化

The 3D encapsulation of cells within hydrogels represents an increasingly important and popular technique for culturing cells and towards the development ...

生物学

Automated Robotic Dispensing Technique for Surface Guidance and Bioprinting of Cells

This manuscript describes the introduction of cell guidance features followed by the direct delivery of cells to these features in a hydrogel bioink using an automated robotic dispensing system. The particular bioink was selected as it allows cells to sediment towards and sense the features. The dispensing system bioprints viable cells in hydrogel bioinks using a backpressure assisted print head. However, by replacing the print head with a sharpened stylus or scalpel, the dispensing system can also be employed to create topographical cues through surface etching. The stylus movement can be programmed in steps of 10 &#181;m in the X, Y and Z directions. The patterned grooves were able to orientate mesenchymal stem cells, influencing them to adopt an elongated morphology in alignment with the grooves&#39; direction. The patterning could be designed using plotting software in straight lines, concentric circles, and sinusoidal waves. In a subsequent procedure, fibroblasts and mesenchymal stem cells were suspended in a 2% gelatin bioink, for bioprinting in a backpressure driven extrusion printhead. The cell bearing bioink was then printed using the same programmed coordinates used for the etching. The bioprinted cells were able to sense and react to the etched features as demonstrated by their elongated orientation along the direction of the etched grooves.

This protocol describes a bioprinting methodology using an automated robotic depositing system that incorporates etched topographical guidance cues with the precision deposition of a cell bearing hydrogel bioink. The printed cells are directly delivered to the etched features and are able to sense and orientate with them.

細胞の表面のガイダンスとBioprintingための自動ロボット調剤技術

This manuscript describes the introduction of cell guidance features followed by the direct delivery of cells to these features in a hydrogel bioink using ...

Mammalian Cell Encapsulation in Alginate Beads Using a Simple Stirred Vessel

Cell encapsulation in alginate beads has been used for immobilized cell culture in vitro as well as for immunoisolation in vivo. Pancreatic islet encapsulation has been studied extensively as a means to increase islet survival in allogeneic or xenogeneic transplants. Alginate encapsulation is commonly achieved by nozzle extrusion and external gelation. Using this method, cell-containing alginate droplets formed at the tip of nozzles fall into a solution containing divalent cations that cause ionotropic alginate gelation as they diffuse into the droplets. The requirement for droplet formation at the nozzle tip limits the volumetric throughput and alginate concentration that can be achieved. This video describes a scalable emulsification method to encapsulate mammalian cells in 0.5% to 10% alginate with 70% to 90% cell survival. By this alternative method, alginate droplets containing cells and calcium carbonate are emulsified in mineral oil, followed by a decrease in pH leading to internal calcium release and ionotropic alginate gelation. The current method allows the production of alginate beads within 20 min of emulsification. The equipment required for the encapsulation step consists in simple stirred vessels available to most laboratories.

This video and manuscript describe an emulsion-based method to encapsulate mammalian cells in 0.5% to 10% alginate beads which can be produced in large batches using a simple stirred vessel. The encapsulated cells can be cultured in vitro or transplanted for cellular therapy applications.

シンプルな攪拌槽を用いたアルギン酸ビーズにおける哺乳類細胞のカプセル化

Cell encapsulation in alginate beads has been used for immobilized cell culture in vitro as well as for immunoisolation in vivo. Pancreatic islet ...

Core/shell Printing Scaffolds For Tissue Engineering Of Tubular Structures

Three-dimensional (3D) printing of core/shell filaments allows direct fabrication of channel structures with a stable shell that is cross-linked at the interface with a liquid core. The latter is removed post-printing, leaving behind a hollow tube. Integrating an additive manufacturing technique (like the one described here with tailor-made [bio]inks, which structurally and biochemically mimic the native extracellular matrix [ECM]) is an important step towards advanced tissue engineering. However, precise fabrication of well-defined structures requires tailored fabrication strategies optimized for the material in use. Therefore, it is sensible to begin with a set-up that is customizable, simple-to-use, and compatible with a broad spectrum of materials and applications. This work presents an easy-to-manufacture core/shell nozzle with luer-compatibility to explore core/shell printing of woodpile structures, tested with a well-defined, alginate-based scaffold material formulation.

Presented here is a simple-to-use, core/shell, three-dimensional bioprinting set-up for one-step fabrication of hollow scaffolds, suitable for tissue engineering of vascular and other tubular structures.

管状構造の組織工学のためのコア/シェル印刷足場

Three-dimensional (3D) printing of core/shell filaments allows direct fabrication of channel structures with a stable shell that is cross-linked at the ...

Microfluidic Fabrication of Core-Shell Microcapsules carrying Human Pluripotent Stem Cell Spheroids

Three-dimensional (3D) or spheroid cultures of human pluripotent stem cells (hPSCs) offer the benefits of improved differentiation outcomes and scalability. In this paper, we describe a strategy for the robust and reproducible formation of hPSC spheroids where a co-axial flow focusing device is utilized to entrap hPSCs inside core-shell microcapsules. The core solution contained single cell suspension of hPSCs and was made viscous by the incorporation of high molecular weight poly(ethylene glycol) (PEG) and density gradient media. The shell stream comprised of PEG-4 arm-maleimide or PEG-4-Mal and flowed alongside the core stream toward two consecutive oil junctions. Droplet formation occurred at the first oil junction with shell solution wrapping itself around the core. Chemical crosslinking of the shell occurred at the second oil junction by introducing a di-thiol crosslinker (1,4-dithiothreitol or DTT) to these droplets. The crosslinker reacts with maleimide functional groups via click chemistry, resulting in the formation of a hydrogel shell around the microcapsules. Our encapsulation technology produced 400 &#181;m diameter capsules at a rate of 10 capsules per second. The resultant capsules had a hydrogel shell and an aqueous core that allowed single cells to rapidly assemble into aggregates and form spheroids. The process of encapsulation did not adversely affect the viability of hPSCs, with &gt;95% viability observed 3 days post-encapsulation. For comparison, hPSCs encapsulated in solid gel microparticles (without an aqueous core) did not form spheroids and had &lt;50% viability 3 days after encapsulation. Spheroid formation of hPSCs inside core-shell microcapsules occurred within 48 h after encapsulation, with the spheroid diameter being a function of cell inoculation density. Overall, the microfluidic encapsulation technology described in this protocol was well-suited for hPSCs encapsulation and spheroid formation.

This article describes encapsulation of human pluripotent stem cells (hPSCs) using a co-axial flow focusing device. We demonstrate that this microfluidic encapsulation technology enables efficient formation of hPSC spheroids.

ヒト多能性幹細胞スフェロイドを担持したコアシェル型マイクロカプセルのマイクロ流体作製

Three-dimensional (3D) or spheroid cultures of human pluripotent stem cells (hPSCs) offer the benefits of improved differentiation outcomes and ...

Microgel-Extracellular Matrix Composite Support for the Embedded 3D Printing of Human Neural Constructs

The embedded 3D printing of cells inside a granular support medium has emerged in the past decade as a powerful approach for the freeform biofabrication of soft tissue constructs. However, granular gel formulations have been restricted to a limited number of biomaterials that allow for the cost-effective generation of large amounts of hydrogel microparticles. Therefore, granular gel support media have generally lacked the cell-adhesive and cell-instructive functions found in the native extracellular matrix (ECM).
To address this, a methodology has been developed for the generation of self-healing annealable particle-extracellular matrix (SHAPE) composites. SHAPE composites consist of a granular phase (microgels) and a continuous phase (viscous ECM solution) that, together, allow for both programmable high-fidelity printing and an adjustable biofunctional extracellular environment. This work describes how the developed methodology can be utilized for the precise biofabrication of human neural constructs.
First, alginate microparticles, which serve as the granular component in the SHAPE composites, are fabricated and combined with a collagen-based continuous component. Then, human neural stem cells are printed inside the support material, followed by the annealing of the support. The printed constructs can be maintained for weeks to allow the differentiation of the printed cells into neurons. Simultaneously, the collagen continuous phase allows for axonal outgrowth and the interconnection of regions. Finally, this works provides information on how to perform live-cell fluorescence imaging and immunocytochemistry to characterize the 3D-printed human neural constructs.

This work describes a protocol for the freeform embedded 3D printing of neural stem cells inside self-healing annealable particle-extracellular matrix composites. The protocol enables the programmable patterning of interconnected human neural tissue constructs with high fidelity.

ヒト神経構築物の埋め込み3D印刷のためのミクロゲル-細胞外マトリックス複合サポート

The embedded 3D printing of cells inside a granular support medium has emerged in the past decade as a powerful approach for the freeform biofabrication ...

Proteolytically Degraded Alginate Hydrogels and Hydrophobic Microbioreactors for Porcine Oocyte Encapsulation

In reproductive biology, the biotechnology revolution that began with artificial insemination and embryo transfer technology led to the development of assisted reproduction techniques such as oocyte in vitro maturation (IVM), in vitro fertilization (IVF) and cloning of domestic animals by nuclear transfer from somatic cell. IVM is the method particularly of significance. It is the platform technology for the supply of mature, good quality oocytes for applications such as reduction of the generation interval in commercially important or endangered species, research concerning in vitro human reproduction, and production of transgenic animals for cell therapies. The term oocyte quality includes its competence to complete maturation, be fertilized, thereby resulting in healthy offspring. This means that oocytes of good quality are paramount for successful fertilization including IVF procedures. This poses many difficulties to develop a reliable culture method that would support growth not only of human oocytes but also of other large mammalian species. The first step in IVM is the in vitro culture of oocytes. This work describes two protocols for the 3D culture of porcine oocytes. In the first, 3D model cumulus-oocyte complexes (COCs) are encapsulated in a fibrin-alginate bead interpenetrating network, in which a mixture of fibrin and alginate are gelled simultaneously. In the second one, COCs are suspended in a drop of medium and encapsulated with fluorinated ethylene propylene (FEP; a copolymer of hexafluoropropylene and tetrafluoroethylene) powder particles to form microbioreactors defined as Liquid Marbles (LM). Both 3D systems maintain the gaseous in vitro culture environment. They also maintain COCs 3D organization by preventing their flattening and consequent disruption of gap junctions, thereby preserving the functional relationship between the oocyte, and surrounding follicular cells.

Presented here are two protocols for the encapsulation of porcine oocytes in 3D culture conditions. In the first, cumulus-oocyte complexes (COCs) are encapsulated in fibrin-alginate beads. In the second, they are enclosed with fluorinated ethylene propylene powder particles (microbioreactors). Both systems ensure optimal conditions to maintain their 3D organization.

ポルシン卵母細胞カプセル化のためのタンパク質分解アルギン酸ヒドロゲルおよび疎水性マイクロバイオリアクター

In reproductive biology, the biotechnology revolution that began with artificial insemination and embryo transfer technology led to the development of ...

A Two-Step Strategy that Combines Epigenetic Modification and Biomechanical Cues to Generate Mammalian Pluripotent Cells

Cell phenotype can be reversed or modified with different methods, with advantages and limitations that are specific for each technique. Here we describe a new strategy that combines the use of chemical epigenetic erasing with mechanosensing-related cues, to generate mammalian pluripotent cells. Two main steps are required. In the first step, adult mature (terminally differentiated) cells are exposed to the epigenetic eraser 5-aza-cytidine to drive them into a pluripotent state. This part of the protocol was developed, based on the increasing understanding of the epigenetic mechanisms controlling cell fate and differentiation, and involves the use of the epigenetic modifier to erase cell differentiated state and then drive into a transient high plasticity window.
In the second step, erased cells are encapsulated in polytetrafluoroethylene (PTFE) micro-bioreactors, also known as Liquid Marbles, to promote 3D cell rearrangement to extend and stably maintain the acquired high plasticity. PTFE is a non-reactive hydrophobic synthetic compound and its use permits the creation of a cellular microenvironment, which cannot be achieved in traditional 2D culture systems. This system encourages and boosts the maintenance of pluripotency though bio-mechanosensing-related cues.
The technical procedures described here are simple strategies to allow for the induction and maintenance of a high plasticity state in adult somatic cells. The protocol allowed the derivation of high plasticity cells in all mammalian species tested. Since it does not involve the use of gene transfection and is free of viral vectors, it may represent a notable technological advance for translational medicine applications. Furthermore, the micro-bioreactor system provides a notable advancement in stem cell organoid technology by in vitro re-creating a specific micro-environment that allows for the long-term culture of high plasticity cells, namely as ESCs, iPSCs, epigenetically erased cells and MSCs.

We here present a method that combines the use of chemical epigenetic erasing with mechanosensing-related cues to efficiently generate mammalian pluripotent cells, without the need of gene transfection or retroviral vectors. This strategy is, therefore, promising for translational medicine and represents a notable advancement in stem cell organoid technology.

エピジェネティック修飾と生体力学的手がかりを組み合わせて哺乳類多能性細胞を生成する2段階戦略

Cell phenotype can be reversed or modified with different methods, with advantages and limitations that are specific for each technique. Here we describe ...