Scale and structure dependent solute diffusivity within microporous tissue engineering scaffolds

Giovanni S Offeddu,Ruth E Cameron,Lakshana Mohee

doi:10.1007/s10856-020-06381-x

Giovanni S Offeddu, Ruth E Cameron + Show 1 more

Open Access

https://doi.org/10.1007/s10856-020-06381-x

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Abstract

Diffusion of nutrients to cells cultured within three-dimensional scaffolds is fundamental for cell survival during development of the tissue construct, when no vasculature is present to aid transport. Significant efforts have been made to characterize the effect of structure on solute diffusivity in nanoporous hydrogels, yet a similar thorough characterization has not been attempted for microporous scaffolds. Here, we make use of freeze-dried collagen scaffolds, possessing pore sizes in the range 150–250 μm and isotropic or aligned morphology, to study the diffusivity of fluorescent dextran molecules. Fluorescence recovery after photobleaching is used to measure the self diffusivity of the solutes within single pores, while Fickian diffusion over scales larger than the pore size is studied by assessing the solute concentration profile within the materials over time. We show that, not only do the morphological parameters of the scaffolds significantly affect the diffusivity of the solutes, but also that the assessment of such diffusivity depends on the length scale of diffusion of the molecules under investigation, with the resulting diffusion coefficients being differently affected by the scaffold structure. The results provided can guide the design of scaffolds with tailored diffusivity and nutrient concentration profiles.

Highlights

Supplementary information The online version of this article contains supplementary material, which is available to authorized users.Tissue engineering scaffolds have evolved in the last two decades to recapitulate the cellular microenvironment found in a variety of tissues
Collagen, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), n-hydroxysuccinimide (NHS), rhodamine B, and fluorescein isothiocyanate (FITC)-conjugated dextrans of molecular weight 4, 20, 250, and 2000 kDa, were all purchased from Sigma Aldrich UK and used without further purification
Both translational (Fig. 4b) and self (Fig. 4c) diffusion coefficients decreased with dextran molecular weight, with the average always larger for the isotropic structures in the case of translational diffusion (p < 0.05), but comparable for the two structures for self diffusion (p > 0.05)

Summary

Introduction

Tissue engineering scaffolds have evolved in the last two decades to recapitulate the cellular microenvironment found in a variety of tissues. The design variables available for scaffolds are numerous, even after satisfaction of fundamental requirements such as the use of non-cytotoxic materials and porous, hydrated morphologies [1]. Cell substrates can be made to be nanoporous to encapsulate cells in a rich biomimetic extra-cellular matrix (ECM) environment, as in the case of most hydrogels [2], or 46 Page 2 of 11. Accurate assessment of scaffold transport properties is, necessary to ensure successful translation to clinical settings

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