Speaker
Description
Introduction
Cell carriers are being utilized in cell culture applications that demand efficiency and large volumes of cells, by utilizing the carriers high surface area in a relatively low volume [1]. Hydrogel microgels, which have been extensively utilized in tissue engineering could offer a platform to build tissue [2], but usually scalability of hydrogel microparticle production and a formulation that can be oil-free and cost efficient has been difficult to combine in one process. In this work we report the fabrication of magnetic hydrogel microparticles using in-air microfluidics [3], their post-processing into magnetic cell carriers and finally their assembly into a composite via magnetic actuation, where cells on the surface of the carriers bond the microgels into tissue composites, which we name Cellularly Annealed Tissue (CAT) Structures.
Methods
1% Alginate particles were produced using In-air microfluidics, briefly we jetted a monodisperse droplet train of of 1% Sodium Alginate in MiliQ polymer solution, supplemented with 5% w/v Fe powder and polymerized it with a 0.2mM CaCl jet, resulting in a monodisperse production 200μm magnetic alginate particles. The produced particles were coated with Gelatin Type A, and crosslinked using 2% v/v Glutaraldehyde in MiliQ, which resulted in a magnetic cell carrier particle suspension. Red Fluorescent Protein modified Mesenchymal Stem Cells (RFP-MSCs) were seeded on the magnetic carriers, and after 3 days of culture, a neodymium magnet was used below the culture plate to steer the particles into a jammed aggregated construct. After 1 day, the structure was annealed by the cells in the interstitial space, resulting in a CAT that could be steered as one body using magnetic steering.
Results
The coated magnetic particles functioned as cell carriers that a) allowed cell adhesion and b) could be steered using a neodymium magnet to the desired position when the magnet was placed for a short amount of time near the culture plate. Constant magnetic actuation (1 day) of the suspension allowed the cells on the magnetic carriers to be in contact with multiple particles and allowed a CAT structure to emerge.
Discussion
We demonstrate that by functionalizing the core of hydrogel particles with Fe powder and coating with Gelatin in order to enable cell adhesion, the controllable assembly of CAT structures can be achieved. By using in-air microfluidics, no extensive washing steps are necessary and the choice of Fe as the magnetic material, makes the magnetic cell carriers biocompatible. By using different cell types on the magnetic carriers and mixing them together, a novel bottom-up approach of magnetic tissue assembly can be envisioned where the carriers behave as the filler material and the cells as the interstitial phase.
Bibliography
[1] J Malda et al "Microcarriers in the engineering of cartilage and bone" Trends in Biotechnology, 2006.
[2] JP Newsom et al "Microgels: Modular, Tunable Constructs for Tissue Regeneration" acta biomaterialia, vol. 1, no. 88, 2019.
[3] T Kamperman et al "Ultrahigh-Throughput Production of Monodisperse and Multifunctional Janus Microparticles Using in-Air Microfluidics" ACS Applied Materials & Interfaces, vol. 10, no. 28 , 2018.
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