A bioinspired scaffold for rapid oxygenation of cell encapsulation systems

Inadequate oxygenation is a major challenge in cell encapsulation, a therapy which holds potential to treat many diseases including type I diabetes. In such systems, cellular oxygen (O2) delivery is limited to slow passive diffusion from transplantation sites through the poorly O2-soluble encapsulating matrix, usually a hydrogel. This constrains the maximum permitted distance between the encapsulated cells and host site to within a few hundred micrometers to ensure cellular function. Inspired by the natural gas-phase tracheal O2 delivery system of insects, we present herein the design of a biomimetic scaffold featuring internal continuous air channels endowed with 10,000-fold higher O2 diffusivity than hydrogels. We incorporate the scaffold into a bulk hydrogel containing cells, which facilitates rapid O2 transport through the whole system to cells several millimeters away from the device-host boundary. A computational model, validated by in vitro analysis, predicts that cells and islets maintain high viability even in a thick (6.6 mm) device. Finally, the therapeutic potential of the device is demonstrated through the correction of diabetes in immunocompetent mice using rat islets for over 6 months.

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Software and code
Policy information about availability of computer code Data collection Microscopy images were taken by a digital inverted microscope (EVOS FL) using EVOS AMF4300 imaging system. Confocal images were taken by a Zeiss710 using Zeiss Zen 2012 software. H&E staining images were taken by an Aperio Scanscope (CS2) using ISCapture 3.9 software. Stereo microscope images were taken by a stereomicroscope (Olympus SZ61) using ISCapture 3.9 software. Data analysis OriginPro 8.5.1 software and GraphPad Prism 8 software were used for data plotting. R 4.1.1 software was used for statistical analyses. COMSOL Multiphysics 5.4 software and MATLAB 2019a software were used for computational modeling. MATLAB 2019a software was used for EPR image processing. ImageJ 1.52p software was used for confocal image processing. Avizo 8.1.1 software was used for Nano-CT image processing.
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April 2020
Data Policy information about availability of data All manuscripts must include a data availability statement. This statement should provide the following information, where applicable: -Accession codes, unique identifiers, or web links for publicly available datasets -A list of figures that have associated raw data -A description of any restrictions on data availability All data supporting the findings of this study are available within the article and the supplementary information files and from the corresponding author upon reasonable request.

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Life sciences study design
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Sample size
The chosen sample sizes in this study were similar to those generally employed and accepted in this field (see Data exclusions No data was excluded.

Replication
All experiments were performed at least twice, but more often more than three times. Details about the replication of experiments are indicated in the figure legends where applicable.
Randomization For in vitro studies, the same cells/alginate suspension was used for the control group and SONIC group, then some samples from each group were randomly chosen for following staining and imaging. For in vivo studies, mice were randomly allocated by body weight and level of diabetic state (blood glucose level after diabetes induction) to the different experimental groups. For ex vivo studies, samples were randomly chosen for following staining and imaging.

Blinding
No formal blinding was used. For the in vitro and ex vivo characterizations, the SONIC devices can be easily identified by the visual observation of the inner incorporated scaffold. For the in vivo characterizations, it's easy to recognize the control device groups by the wet cages from frequent urination of uncorrected diabetic mice. However, the blood glucose monitoring was performed by different individuals and the GSIS ELISA measurement was performed in a blinding way.

Reporting for specific materials, systems and methods
We require information from authors about some types of materials, experimental systems and methods used in many studies. Here, indicate whether each material, system or method listed is relevant to your study. If you are not sure if a list item applies to your research, read the appropriate section before selecting a response. Antibodies used mouse anti-rat glucagon (Abcam, ab10988, clone K79bB10, 1:200) Alexa Fluor 594-conjugated goat anti-rabbit IgG (Thermofisher, A11037, 1:400) Alexa Fluor 488-conjgated donkey anti-mouse IgG (Thermofisher, A21202, 1:400)

Authentication
The vendor had performed cell authentication.

Mycoplasma contamination
Cells tested negative for mycoplasma contamination.
Commonly misidentified lines (See ICLAC register) No commonly misidentified lines were used in this study.

Animals and other organisms
Policy information about studies involving animals; ARRIVE guidelines recommended for reporting animal research Laboratory animals 8-week-old male C57BL/6J mice (Stock No: 000664) were purchased from the Jackson Laboratory (Bar Harbor, ME). The mice were maintained at a temperature of 70-72°F with 30-70% humidity under a 14-hour light/10-hour dark cycle. 8-week-old male Sprague-Dawley rats (Strain Code 400, weight ~300 g) were purchased from Charles River Laboratories (Wilmington, MA). The rat were maintained at a temperature of 70-72°F with 30-70% humidity under a 12-hour dark/12-hour light cycle. The mealworm beetles (Tenebrio molitor) were purchased from PetSmart (Ithaca, NY).

Wild animals
Studies did not involve wild animals Field-collected samples No studies involved samples collected from the field.

Ethics oversight
The Cornell Institutional Animal Care and Use Committee approved all animal procedures.
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