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. 2018 Apr 25;8:6508. doi: 10.1038/s41598-018-23862-w

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© The Author(s) 2018

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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βAir device and system to measure oxygen profile within slabs. (A) Islet compartment with islets embedded in a 500–600 μm thick alginate slab reinforced on each side with a stainless steel grid, outer face overlain with alginate-filled PTFE membrane, which interfaces with host tissue, interior face covered by oxygen-permeable silicone rubber-PTFE membrane. (B) PEEK housing contained gas chamber and two ports connected to subcutaneously-implanted access ports. (C) Top view of βAir device with about 2,400 IEQ. Islet density was varied by varying diameter of islet chamber. (D) Top surface of devices with different islet densities, islets visible beneath top metal grid. Volume fraction of slab occupied by islets with about 2,400, 3,600, and 4,800 IEQ/cm² was 8.5, 12.7, and 17.0%, respectively, at slab thickness of 500 μm. (E) Oxygen profiles in islet compartment measured with modified βAir device (lacking alginate-filled membrane and top metal grid) placed in chamber, 37 °C, pO₂ 40 mmHg to simulate microvasculature). Device was immersed with very thin layer of medium over slab, gas chamber purged with mixtures at various pO₂ (outlet port not shown). pO₂ microelectrode under control of micromanipulator inserted into slab, traversed in stepwise increments. (F) Typical oxygen profile within slab. About 2,400 IEQ with OCR of 3.5 pmol/IEQ/min immobilized in a 600-μm alginate slab at a density of 4,800 IEQ/cm². pO₂ electrode was inserted at immobilized islet slab-medium interface and moved sequentially at increments of 100 μm down to the gas permeable membrane. Left Panel: Raw data. Right Panel: pO₂ profile calculated from steady-state data in left panel.