Micro computed tomography with and without contrast enhancement for the characterization of microcarriers in dry and wet state

Abstract

In the field of regenerative medicine, microcarriers are used as support matrix for the growth of adherent cells. They are increasingly recognised as promising biomaterials for large scale, cost-effective cell expansion bioreactor processes. However, their individual morphologies can be highly heterogeneous which increases bioprocesses’ variability. Additionally, only limited information is available on the microcarriers’ 3D morphology and how it affects cell proliferation. Most imaging modalities do not provide sufficient 3D information or have a too limited field of view to appropriately study the 3D morphology. While microfocus X-ray computed tomography (microCT) could be appropriate, many microcarriers are hydrated before in-vitro use. This wet state makes them swell, changing considerably their morphology and making them indistinguishable from the culture solution in regular microCT images due to their physical density close to water. The use of contrast-enhanced microCT (CE-CT) has been recently reported for 3D imaging of soft materials. In this study, we selected a range of commercially available microcarrier types and used a combination of microCT and CE-CT for full 3D morphological characterization of large numbers of microcarriers, both in their dry and wet state. With in-house developed image processing and analysis tools, morphometrics of individual microcarriers were collected. Also, the morphology in wet state was assessed and related to accessible attachment surface area as a function of cell size. The morphological information on all microcarriers was collected in a publicly available database. This work provides a quantitative basis for optimization and modelling of microcarrier based cell expansion processes.

Microcarrier Screening and Evaluation for Dynamic Expansion of Human Periosteum-Derived Progenitor Cells in a Xenogeneic Free Medium

“…Depending on the cell type, the morphological characteristics of the microcarriers could also increase the available surface area. For example, the Cultispher-S microcarriers are macro-porous and cells smaller than 10 μm could use the surface area inside the pores to adhere to de Bournonville et al (2021) . Another factor influencing the available surface area is the swelling factor of the microcarriers that require hydration, such as Cultispher-S, Cytodex-1 and Synthemax II dissolvable.…”

“…Commercial microcarriers differ in core material, coating material, ionic surface charge, porosity, swelling upon hydration and size resulting in different seeding, proliferating or harvesting efficiency for a specific cell type. Important research into the full 3D morphologic characterization of microcarriers using a combination of microfocus X-ray computed tomography (microCT) and contrast-enhanced microCT (CE-CT) is recently reported by our group ( de Bournonville et al, 2021 ).…”