Ebrahimi Orimi, H. | bioRxiv Science

bioRxiv2026

Extended perfused culture of cm-scale endocrine pancreatic tissues created through sacrificial embedded printing into alginate

Pluripotent stem cells represent a potentially unlimited cell source for the fabrication of human bioartificial tissues to study and treat degenerative conditions such as type 1 diabetes. Alginate is widely used for mammalian cell immobilization and the primary hydrogel studied for pancreatic islet encapsulation. Rheological properties of alginate solutions or fully gelled forms are unsuitable as support matrix for embedded 3D printing. We describe partially gelled self-healing alginate formulations tuned for embedded 3D printing. Perfusable multi-plane hierarchical networks branching into 10 parallel channels, obtained by 3D printing of Pluronic F127 into the alginate support, show high fidelity to computer-assisted models. Therapeutic {beta}-cell doses (40x106 cells/mL) within centimeter-thick perfusable constructs remained viable for at least 1 week of culture under flow, with rapid insulin secretion detected upon glucose challenges. Stem cell-derived islet clusters cultured in 5-channel contructs for 25 days differentiated towards functional insulin-expressing cells. We describe a novel approach to generate cm-scale perfusable endocrine pancreatic constructs using sacrificial embedded 3D printing into alginate. This approach offers an adaptable platform to engineer perfusable cm-scale functional endocrine pancreatic tissues and potentially other vascularized bioartificial tissues.

bioengineering↗

bioRxiv2024

An accessible platform to quantify oxygen diffusion in cell-laden hydrogels and its application to alginate-immobilized pancreatic beta cells

Hydrogels are commonly used to immobilize mammalian cells, serving various purposes such as providing mechanical cues in three-dimensional cultures and acting as barriers for immunoprotection in transplantation. For instance, islet encapsulation holds promise in delivering insulin-producing cells for diabetes cellular therapy. Cell immobilization, by creating a barrier to bulk fluid motion, leads to diffusion-limited molecular transport and concentration gradients of nutrients such as oxygen being consumed by the immobilized cells. Oxygen mass transport models aid in designing immobilization strategies but rely on input parameters like oxygen diffusivity, often assumed rather than experimentally measured due to limited resources or expertise. We propose an accessible, cost-effective, and easy to operate system to experimentally determine the diffusion coefficient of cell-laden hydrogels, with application tested to alginate-immobilized pancreatic beta cell (MIN6). As compared to water, the oxygen diffusion coefficient was significantly reduced in alginate gels. The oxygen diffusion coefficient was inversely correlated with the dynamic loss modulus for gels with similar chemical composition, and significantly reduced when the alginate concentration was increased from 2% to 5%. The viability of immobilized MIN6 cells was highly dependent both on gel concentration and cell density, as predicted by Thiele modulus and effectiveness factor values calculated from measured oxygen diffusion coefficients. The proposed platform, combining a simple experimental setup and the use of dimensionless numbers, offers a straightforward means to predict maximal diffusion distances in cell immobilization strategies. This platform can be implemented in the rational design of cell encapsulation, immobilized cell culture, and tissue engineering strategies.

bioengineering↗