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Technical Briefs

Encapsulation of Living Cells in Small (100μm) Alginate Microcapsules by Electrostatic Spraying: A Parametric Study

[+] Author and Article Information
Wujie Zhang

Department of Mechanical Engineering and Biomedical Engineering Program, University of South Carolina, 300 Main Street, Columbia, SC 29208

Xiaoming He1

Department of Mechanical Engineering and Biomedical Engineering Program, University of South Carolina, 300 Main Street, Columbia, SC 29208xmhe@sc.edu

1

Corresponding author.

J Biomech Eng 131(7), 074515 (Jun 30, 2009) (6 pages) doi:10.1115/1.3153326 History: Received September 12, 2008; Revised May 07, 2009; Published June 30, 2009

A parametric study was performed to understand the effect of preparation parameters on size, morphology, and encapsulation efficiency (i.e., cells/microcapsule) of alginate microcapsules prepared using the electrostatic spray method. The preparation parameters studied include sodium alginate concentration, spray voltage, flow rate, and cell density. It was found that both the flow rate and spray voltage have a significant impact on microcapsule size while the microcapsule morphology is greatly influenced by both the sodium alginate concentration and spray voltage. To obtain small (100μm) cell-loaded microcapsules with good morphology (i.e., round in shape and uniform in size) and high encapsulation efficiency (>5 cells/microcapsule), the optimal ranges of spray voltage, flow rate, alginate concentration, and cell density are from 1.6–1.8 kV, 1.5–3 ml/h, >1.5% (w/v), and (3–5)×106 cells/ml, respectively. Under optimal preparation conditions, cells were found to survive the microencapsulation process well.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

A sketch (not to scale) of the electrostatic spray device used for generating alginate microcapsules in this study

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Figure 2

Microcapsule size as a function of sodium alginate concentration (a) and typical micrographs of the generated microcapsules with 2% (w/v) (b) and 1.5% (w/v) (c) alginate solutions in the absence of living cells: Spray voltage and flow rate are 2.0 kV and 5 ml/h, respectively. The error bar represents standard deviation. Scale bar: 100 μm.

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Figure 3

Microcapsule size as a function of spray voltage (a) and typical micrographs of the generated microcapsules with 1.4 kV (b) and 1.6 kV (c) spray voltages in the absence of living cells: Alginate concentration and flow rate are 1.9% (w/v) and 5 ml/h, respectively. The error bar represents standard deviation. Scale bar: 100 μm.

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Figure 4

Microcapsule size as a function of spray flow rate (a) and typical micrographs of the generated microcapsules with 1.5 ml/h (b) and 2.5 ml/h (c) flow rates in the absence of living cells: Alginate concentration and spray voltage are 1.9% (w/v) and 1.8 kV, respectively. The error bar represents standard deviation. Scale bar: 100 μm.

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Figure 5

Microcapsules prepared under various conditions showing the effect of cell density in alginate solution on cell encapsulation efficiency: (a) 1×106cells/ml cell density, 2% (w/v) alginate solution, 1.6 kV spray voltage, and 1.5 ml/h flow rate; and (b) 3×106cells/ml cell density, 2% (w/v) alginate solution, 1.6 kV spray voltage, and 2 ml/h flow rate. Scale bar: 100 μm.

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Figure 6

Typical images of microencapsulated cells (a) and calcein AM (green)/ethidium homodimer (EthD-1, red) staining of the cells in microcapsules (green for live cells and red for dead cells, visible in the online version only) (b). Scale bars: 100 μm.

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Figure 7

Proliferation of cells collected post microencapsulation and liquefaction in 3 days together with typical micrographs (insets) of the cells cultured in a Petri dish in three different days

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