Development of a "Pro-Matrix" Advanced Cell Scaffold Biomaterial to Support Mesenchymal Stem Cell Therapy

Inverarity, Catriona (2021). Development of a "Pro-Matrix" Advanced Cell Scaffold Biomaterial to Support Mesenchymal Stem Cell Therapy. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0001278c

Abstract

Cell therapies are typically limited by the rapid dispersal of cells on delivery. Scaffolds offer an approach of enhancing therapeutic efficiency and efficacy as a delivery vehicle and implantable niche. This project aimed to combine the bio-intelligent properties of fibrin-based scaffolds with the potential of MSC cell therapies for activating healing in chronic wounds.

A highly porous fibrin-based biomaterial scaffold was developed using an optimised emulsion templating technique. Templating enables reproducible manufacture of materials with a regular, highly porous structure with a high degree of pore interconnectivity and consistent pore size distribution. The method was optimised to generate a range of pore diameters suitable for skin tissue engineering, but it could be adjusted for other purposes. What differentiates this method is that the emulsion is amenable to incorporation of protein monomers without causing any denaturation, which allows the creation of a native-like structure during fibrin formation. The initial structure is then stabilised by glutaraldehyde cross-linking. The resulting scaffold is suited to cell ingress and supporting angiogenesis and allows fluid and nutrient exchange between the scaffold and the wound environment.

The experimental work undertaken to design a suitable emulsion produced results which, to the authors’ knowledge, have not been reported elsewhere. The two distinct patterns of behaviour identified suggest specific surfactant traits that make certain kinds of surfactants extremely useful in supporting high internal phase emulsions. The reason(s) for this are unclear, but the overall trend has potential utility in emulsion formulation. ‘Oil carrying capacity’ (OCC) is proposed as an index for ranking surfactants by the oil fraction (in an oil-in-water emulsion) for which stability is greatest.

This project is divided into two main sections: emulsion formulation and using the optimised emulsion to template a scaffold that was then refined to produce a material with appropriate structural, mechanical, and biochemical properties for skin tissue engineering. Emulsion design encompassed degradation kinetics and achieving appropriate internal phase droplet size, packing and size distribution for cell and blood vessel ingress. Successful emulsions were then tested for protein compatibility and used to template various fibrin-based scaffolds. By iterative redesign, refined and reproducible scaffolds were produced that were characterised by various means to assess their suitability as skin tissue engineering scaffolds.

This work describes a novel biocompatible fibrin scaffold with optimised microstructure for cell ingress and angiogenesis, excellent handling capabilities in both freeze-dried and rehydrated forms and biocompatibility as demonstrated by in vitro assays.

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