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Porous silicon based cell microarrays: optimizing human endothelial cell-material surface interactions and bioactive release Adel Dalilottojari, Bahman Delalat, Frances J. Harding, Michaelia P. Cockshell, Claudine S. Bonder, and Nicolas H. Voelcker Biomacromolecules, Just Accepted Manuscript • DOI: 10.1021/acs.biomac.6b01248 • Publication Date (Web): 15 Oct 2016 Downloaded from http://pubs.acs.org on October 22, 2016
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Biomacromolecules
Porous silicon based cell microarrays: optimizing human endothelial cell-material surface interactions and bioactive release Adel Dalilottojari,† Bahman Delalat,† Frances J. Harding,† Michaelia P. Cockshell,‡ Claudine S. Bonder‡ and Nicolas H. Voelcker*, † †ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, Future Industries Institute, University of South Australia, GPO Box 2471, Adelaide SA 5001, Australia. ‡Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia. KEYWORDS: Porous silicon (pSi), cell microarray, human endothelial cells, immobilized protein, releasing growth factors, microenvironment.
ABSTRACT: Porous silicon (pSi) substrates are a promising platform for cell expansion, since pore size and chemistry can be tuned to control cell behavior. In addition, a variety of bioactives can be loaded into the pores and subsequently released to act on cells adherent to the substrate. Here we construct a cell microarray on plasma polymer coated pSi substrates that enables the simultaneous culture of human endothelial cells on printed immobilized protein factors while a second soluble growth factor is released from the same substrate. This allows three elements of
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candidate pSi scaffold materials - topography, surface functionalization and controlled factor release - to be assessed simultaneously in high throughput. We show that protein conjugation within printed microarray spots is more uniform on the pSi substrate than on flat glass or silicon surfaces. Active growth factors are released from the pSi surface over a period of several days. Using an endothelial progenitor cell line, we investigate changes in cell behavior in response to the microenvironment. This platform facilitates the design of advanced functional biomaterials, including scaffolds and carriers for regenerative medicine and cell therapy.
Introduction Cell microarrays are a high throughput lab-on-chip platform that allows the screening of cellmaterial surface interaction.1-8 Biomolecules or polymers are printed as microscale spots onto a glass or silicon substrates, while the rest of the substrate is passivated to resist non-specific cell and protein attachment.9-11 Due to their spatial separation, every printed spot is considered an independent experimental replicate.12-16 This analytical plat-form allows a large number of candidate proteins or polymers from a library to be screened in parallel.10, 14, 17 The microarray format requires only minute amounts of molecules, cells and reagents in comparison to the conventional bioanalytical methods. These attributes have contributed to this technique becoming into focus for bio-materials design such the development of bacteria-resistant polymers and surfaces for stem cell expansion, presenting combinations of extracellular matrix (ECM) components and growth factors (GFs).18 However, to date, the platform has been confined to biomolecules immobilized on the array substrate. Using a porous substrate material, the microarray format could be extended to the simultaneous investigation of the role of soluble factors being released from the substrate.
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Porous silicon (pSi) is widely considered a promising nanostructured biomaterial due to several unique properties: high biocompatibility and resorbability,19-22 very high surface to weight ratio (up to 800 m2 g-1)23 and tunable porosity. pSi is fabricated by means of anodization of monocrystalline silicon wafers and degrades into orthosilicic acid when in contact with an aqueous environment. Silicic acid is the bioavailable form of silicon.20,
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The structural
tunability of pSi allows a range of pore sizes ranging from microporous (
