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ORIGINAL ARTICLE

Combined Porogen Leaching and Emulsion Templating

to produce Bone Tissue Engineering Scaffolds

Robert Owen 1,2,3 , Colin Sherborne , Richard Evans , Gwendolen C. Reilly , Frederik Claeyssens *
4
1,2
1,2
2
1 Department of Materials Science and Engineering, INSIGNEO Institute for in silico Medicine, University of Sheffield, UK
2 Department of Materials Science and Engineering, The Kroto Research Institute, University of Sheffield, UK
3 Regenerative Medicine and Cellular Therapies, School of Pharmacy, University of Nottingham Biodiscovery Institute,
University Park, UK
4 Bioengineering, Interdisciplinary Programmes Engineering, University of Sheffield, UK

Abstract: Bone has a hierarchy of porosity that is often overlooked when creating tissue engineering scaffolds where pore sizes
are typically confined to a single order of magnitude. High internal phase emulsion (HIPE) templating produces polymerized
HIPEs (polyHIPEs): highly interconnected porous polymers which have two length scales of porosity covering the 1–100 µm
range. However, additional larger scales of porosity cannot be introduced in the standard emulsion formulation. Researchers
have previously overcome this by additively manufacturing emulsions; fabricating highly microporous struts into complex
macroporous geometries. This is time consuming and expensive; therefore, here we assessed the feasibility of combining
porogen leaching with emulsion templating to introduce additional macroporosity. Alginate beads between 275 and 780 µm were
incorporated into the emulsion at 0, 50, and 100 wt%. Once polymerized, alginate was dissolved leaving highly porous polyHIPE
scaffolds with added macroporosity. The compressive modulus of the scaffolds decreased as alginate porogen content increased.
Cellular performance was assessed using MLO-A5 post-osteoblasts. Seeding efficiency was significantly higher and mineralized
matrix deposition was more uniformly deposited throughout porogen leached scaffolds compared to plain polyHIPEs. Deep cell
infiltration only occurred in porogen leached scaffolds as detected by histology and lightsheet microscopy. This study reveals a
quick, low cost and simple method of producing multiscale porosity scaffolds for tissue engineering.
Keywords: Polymerized high internal phase emulsions, Emulsion templating, Alginate, Multiscale porosity, Bone tissue engineering

*Corresponding Author: Frederik Claeyssens, Department of Materials Science and Engineering, The Kroto Research Institute, University of
Sheffield, UK; f.claeyssens@sheffield.ac.uk
Received: March 06, 2020; Accepted: April 01, 2020; Published Online: April 30, 2020
Citation: Owen R, Sherborne C, Evans R, et al., 2020, Combined Porogen Leaching and Emulsion Templating of Bone Tissue
Engineering Scaffolds, Int J Bioprint, 6(2):265. DOI: org/10.18063/ijb.v6i2.265

1 Introduction size pores promote different functions. Smaller,
well interconnected cell-scale porosities promote
Native bone has a hierarchical structure with cell proliferation, migration, and nutrient
a range of pore sizes that span multiple length
scales . Inclusion of this multiscale porosity diffusion, while pore sizes of at least 50 μm but
[1]
when producing bone tissue engineering scaffolds ideally >300 μm have been reported as beneficial
is often overlooked with pore sizes typically for osseous tissue deposition [5-7] .
confined to a single order of magnitude. However, Polymerized high internal phase emulsions
it has been demonstrated that a multiscale porosity (polyHIPEs) are highly porous materials well
enhances in vitro and in vivo performance of suited for three-dimensional (3D) cell culture and
scaffolds [2-4] . The reason for this is that different tissue engineering, and classically have porosity at

© 2020 Owen, et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International
License (http://creativecommons.org/licenses/by-nc/4.0/), permitting all non-commercial use, distribution, and reproduction in any medium, provided the
original work is properly cited.
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