One-Step Generation of Aqueous-Droplet-Filled Hydrogel Fibers as Organoid Carriers Using an All-in-Water Microfluidic System

Abstract

Hydrogel fibers are promising carriers for biological applications due to their flexible mechanical properties, well-defined spatial distribution, and excellent biocompatibility. In particular, the droplet-filled hydrogel fibers with the controllable dimension and location of droplets display great advantages to enhance the loading capacity of multiple components and biofunctions. In this work, we proposed a new all-in-water microfluidic system that allows for one-step fabrication of aqueous-droplet-filled hydrogel fibers (ADHFs) with unique morphology and tunable configurations. In the system, the aqueous droplets with equidistance are successfully arranged within the alginate calcium fibers, relying on the design of the pump valve cycle and the select of two immiscible liquids with a stable aqueous interface. The architecture of the ADHF can be flexibly controlled by adjusting the three phase flow rates and the valve switch cycle. The produced ADHFs exhibit high controllability, uniformity, biocompatibility, and stability. The established system enabled the formation of functional human islet organoids in situ through encapsulating pancreatic endocrine progenitor cells within microfibers. The generated islet organoids within droplets exhibit high cell viability and islet-specific function of insulin secretion. The proposed approach provides a new way to fabricate multifunctional hydrogel fibers for materials sciences, tissue engineering, and regenerative medicine.

Making human pancreatic islet organoids: Progresses on the cell origins, biomaterials and three-dimensional technologies

“…Apart from high biocompatibility for cell survival, alginate could protect islet cells from inflammatory response after transplantation due to its negative charge 92 . Alginate has also been used for human islet organoids generation by encapsulating pancreatic endocrine progenitor cells derived from PSCs, because of the fast cross-linking of sodium alginate with calcium/barium chloride, and promotion to maturation of islet organoids by integrin 52 , 58 . However, alginate, which possesses low cell adhesion and cell interaction ability, fails to provide the cell anchorage required for cell survival 93 .…”

Multicompartment Hydrogels

“…In a similar way, Qin and co‐workers fabricated hydrogel fibers loaded with aqueous droplets ( Figure ). [ 199 ] Therefore, the dextran/PEG ATPS was employed to form dextran‐based droplets in a PEG continuous phase via microfluidics. The outer PEG phase was crosslinked via two streams of PEG solution containing alginate and Ca 2+ , respectively.…”

“…b) CLSM images and the bright-field image of aqueous-droplet-filled hydrogel fiber (dextran phase red and PEG phase green; scale bars: 100 μm),and c) SEM images of freeze-dried aqueous-droplet-filled hydrogel fibers (scale bars: 50 μm). Reproduced with permission [199]. Copyright 2021, American Chemical Society.…”

Understanding immune-driven brain aging by human brain organoid microphysiological analysis platform

“…[19][20][21][22][23][24][25][26][27][28] For example, microfluidic droplets have been used to encapsulate cells into water-in-oil droplets or microgels for high throughput generation of uniformed human brain organoids and tumor spheroids. [29][30][31] Based on our development of acoustofluidics, [32][33][34][35][36] our group has adapted this technology to assemble cells for the massive and scaffold-free generation of standardized 3D cell cultures and assembloids. [37][38][39][40] The microfabricated perfusion devices have been developed to perfuse oxygen, nutrients, and/or chemicals into organoids or 3D in vitro cultures to improve the generation, development, and maturation/vascularization of kidney organoids and brain organoids.…”