Development of functional co-cultures of islets of Langerhans and photosynthetically active microalgae

Ph.D. Finn Dani

AutorIn

Ph.D. Finn Dani

Titel

Development of functional co-cultures of islets of Langerhans and photosynthetically active microalgae

Zitierfähige Url:

https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-1048417

Übersetzter Titel (DE)

Entwicklung von funktionellen Ko-Kulturen aus Langerhans-Inseln und photosynthetisch aktiven Mikroalgen

Erstveröffentlichung

2026

Datum der Einreichung

13.03.2026

Datum der Verteidigung

11.05.2026

Abstract (EN)

BACKGROUND: The transplantation of insulin-producing islets of Langerhans is an established treatment for Type 1 Diabetes. Encapsulation of the islets in alginate-based hydrogels offers protection from the immune system, enhancing their longevity. However, this encapsulation blocks blood flow to the islets, leading to oxygen deprivation, hypoxia-related loss of function, and eventual cell death. An alternative approach to address this oxygenation issue is the co-cultivation of islets with photosynthetically active microalgae. Microalgae can provide a blood-independent oxygen supply through photosynthesis, thus supporting the survival and functionality of the islets. To maximize the interaction between the two cell types, bioprinting was used for their spatially defined embedding in a single construct. RESEARCH QUESTIONS: Transitioning from short-term co-immobilization to long-term co-cultivation required the development of suitable cultivation parameters. Two critical factors were identified: (1) maintaining a cultivation temperature of 37 °C, essential for islet survival, and (2) providing illumination to sustain photosynthesis in microalgae. The primary challenges included selecting a compatible microalgae strain, establishing a suitable light source that supports photosynthesis without harming the mammalian cells, and developing a co-culture medium that meets the nutritional requirements of both cell types. The study aimed to develop a co-culture system capable of maintaining both cell types and to demonstrate its viability through a proof-of-concept experiment. The ultimate goal was to show that oxygen generated by microalgae could sustain the viability and insulin secretion of islets under hypoxic conditions. MATERIALS & METHODS Islets of Langerhans were isolated from 10-week-old wild-type female Wistar rats. Using a 3D bioprinter (Bioscaffolder 3.1, GeSiM), islets and microalgae were embedded in an alginate-methylcellulose ink and printed into constructs containing macropores to ensure short diffusion distances. Four main analytical methods were employed to evaluate the viability and functionality of the co-culture system. For pancreatic islets, cell viability was determined using dual fluorometric staining, and glucose-stimulated insulin response was used to evaluate beta-cell functionality by measuring insulin secretion in response to varying glucose concentrations. For microalgae, viability was assessed using fluorescence microscopy and pulse-amplitude modulated (PAM) fluorometry measured photosynthetic efficiency. To assess photosynthetic oxygen production, dissolved oxygen measurement was performed using optical sensor probes. RESULTS: The thermophilic microalgae strain Scenedesmus sp. was identified as a suitable oxygen generator, as it tolerated 37 °C and bioprinting without a reduction in growth rate, viability, or photosynthetic activity. Preliminary studies using the INS-1 model cell line confirmed that red light illumination had no detrimental effects on cell viability, function, or growth. These findings were validated with bioprinted pancreatic islets and Scenedesmus sp., which demonstrated high photosynthetic activity under red light. To meet the nutritional demands of both cell types, the co-culture medium was adapted by substituting ¼ of the islet medium with microalgae medium. This formulation preserved glucose and FCS concentrations for the islets while maintaining the trace element concentration for the microalgae. Both islets and Scenedesmus sp. showed high viability and functionality in this medium. In the proof-of-concept experiment, co-cultured islets and microalgae were bioprinted and cultivated at 37 °C under red light in a hypoxic environment (1% oxygen). The dissolved oxygen measure-ments confirmed that Scenedesmus sp. successfully prevented hypoxic conditions by producing oxygen through photosynthesis. After four days, the co-cultured islets demonstrated a higher viability compared to hypoxic monocultures, an absence of necrotic cores, and significantly greater glucose-stimulated insulin secretion compared to hypoxic monocultures. CONCLUSION: This study successfully developed a co-culture system that supports the survival and func-tionality of both pancreatic islets and photosynthetically active microalgae. Unlike previous co-culture systems that primarily focused on mammalian cells, this was the first to investi-gate both cell partners in-depth, paving the way for long-term co-cultivation. The developed system presents two key future directions: The co-culture system can be tested towards an in vivo investigation in diabetic rat models to evaluate its feasibility, bring-ing it closer to clinical application. Furthermore, the protocols developed for selecting and optimizing co-culture components (e.g., illumination, co-culture medium, and measurement systems) can be adapted for large-scale tissue engineering applications, such as volumetric tissue models or cultured meat, which require reliable oxygen delivery.

Verweis

Publikation im Rahmen der kummulativen Dissertation
Link: https://www.sciencedirect.com/science/article/pii/S073497502200026X?via%3Dihub
Think outside the box: 3D bioprinting concepts for biotechnological applications – recent developments and future perspectives
DOI: 10.1016/j.biotechadv.2022.107930

Selection of a suitable photosynthetically active microalgae strain for the co-cultivation with mammalian cells
Publikation im Rahmen der kummulativen Dissertation
Link: https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.994134/full
DOI: 10.3389/fbioe.2022.994134

The effect of continuous long-term illumination with visible light in different spectral ranges on mammalian cells
Publikation im Rahmen der kummulativen Dissertation
Link: https://www.nature.com/articles/s41598-024-60014-9
DOI: 10.1038/s41598-024-60014-9

Homogeneous and Reproducible Mixing of Highly Viscous Biomaterial Inks and Cell Suspensions to Create Bioinks
Publikation im Rahmen der kummulativen Dissertation
DOI: 10.3390/gels7040227
Link: https://www.mdpi.com/2310-2861/7/4/227

Oxygen Supply of Islets of Langerhans by Photosynthetically Active Microalgae in Bioprinted Co-Cultures Maintains Their Function in a Hypoxic Environment
Publikation im Rahmen der kummulativen Dissertation
DOI: 10.1002/adhm.202505927
Link: https://www.sciencedirect.com/science/article/pii/S073497502200026X?via%3Dihub

Freie Schlagwörter (DE)