"ENGINEERING HIGH DENSITY CAPILLARY-LIKE NETWORKS USING MICROPOROUS ANNEALED PARTICLE TISSUES
M.R. Schot1, C.A. Paggi1, M.L. Becker1, J. Leijten1
Presenting author: Maik Schot, firstname.lastname@example.org
1Department of Developmental BioEngineering, TechMed Centre, University of Twente, the Netherlands
INTRODUCTION: The vascular tree is essential for the function and survival of tissues. However, engineering vascular trees within 3D tissues has remained challenging. Current methods to produce channel-like structures in engineered tissues such as 3D printing are able to mimic large vessels, but struggle to produce highly dense capillary networks at high speeds, limiting their translation to clinically sized constructs.1 Microporous annealed particles (MAP) offer an interesting alternative due to their microporous nature, essentially offering an inherent dense microporous network of channels without having to create it.2 Here, we aim to use our recently developed in-air microfluidics (IAMF) technique to produce cell-laden microgels at ultra-high throughput production rates to create microporous annealed particle (MAP) tissues, allowing for the bottom up development of engineered tissues with inherent highly dense capillary sized pore networks.3
METHODOLOGY: Alginate-Tyramine (ATA) was produced by functionalizing alginate with tyramine groups using DMTMM-based coupling. Using IAMF, hepatic cell laden ATA microgels were prepared via ionic crosslinking under oil-free and surfactant-free conditions. ATA microgel slurries were photocrosslinked into MAPs using ruthenium, sodium persulfate and visible light. MAPs were analyzed on viability, micropore size distribution, pore interconnectivity, hydraulic conductivity, perfusability and mechanical properties.
RESULTS: Cell-laden microgels were successfully produced at varying cell concentrations, maintaining viability after MAP formation through visible light crosslinking. Moreover, MAPs were kept in culture for a period of 7 days and encapsulated cells proliferated within MAP constructs. Confocal analysis confirmed a highly dense, porous network within MAPs with the majority of pores having diameters below 40μm. Pores were shown to lead to increased construct perfusability as compared to nanoporous gels and an interconnected porous network was shown by perfusing 1μm fluorescent particles as well as using microCT analysis. Moreover, small molecules are able to easily perfuse in and out of the MAP as compared to traditional nanoporous gels that are hindered by the diffusion limitation.
CONCLUSION: The combined use of IAMF and ATA allows for ultra-high throughput production of cell laden microgels that can be assembled into MAP tissues containing an inherent, highly dense, interconnected capillary-like network. We thus present a novel and highly scalable production platform for the creation of large engineered tissues with inherent capillary-like networks.
1. Kolesky, David B., et al., Proc. Nat. Acad. Sciences, 113.12, 3179-3184 (2016).
2. Annamalai, R. T. et al., Ann. Biomed. Eng. 47, 1223–1236 (2019).
3. Visser, C. W. et al, Science Advances, 4.1, 1–9 (2018)."