Thesis
Coaxial extrusion of fine diameter tissue filaments
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2023
- Thesis identifier
- T16487
- Person Identifier (Local)
- 201692009
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Coaxial extrusion is a promising technology, which employs a coaxial nozzle composed of two concentrically aligned nozzles (an inner core nozzle and an outer shell nozzle) to fabricate transplantable and autologous tissue filaments contained within robust, porous hydrogel scaffolds. These extruded scaffolds are capable of restoring function to various fibrous tissues within the body, such as peripheral nerve and muscle, which have lost the ability to naturally regenerate through irreversible disease or trauma. The overall aim of this work was to develop a coaxial bio-extrusion platform to create fine diameter extruded stem cell-laden tissue filaments with the capability to retain long-term viability in culture. Further objectives were to develop a hydrogel scaffold material capable of resisting degradation by culture media to maintain tissue filament integrity. It was also desirable to demonstrate extrusion with multiple cell types and to present an initial assessment of the viability of the coaxial extrusion platform for use in drug testing applications, providing the benefit of a more natural in vivo-like environment to study drug-cell interactions in comparison to traditional two-dimensional methods. By embedding cells within an extracellular matrix material, such as collagen, an extrudable bioink is created, which may be placed within the inner core of a concentrically aligned coaxial nozzle. By simultaneously extruding using alginate within the outer shell nozzle into a crosslinking bath containing divalent cations such as Ca2+, hollow tubular alginate scaffolds containing cell-laden collagen filaments may be produced. By manipulating key extrusion parameters such as flow rate magnitude, core/shell flow rate and collagen concentration, filament diameters were successfully reduced from > 400 μm to sub-20 μm, consequently aiding nutrient diffusion and long-term cell survival in culture. Small diameter (sub-20 μm) adipose-derived stem cell-laden collagen filaments have been extruded and matured with high viability (> 90%) over a 21-day period, achieved by modification of the core/shell flow rate ratio and collagen concentration. Combined calcium and barium cross-linking was employed in order to maintain scaffold integrity by tuning alginate cross-linking concentration, time and ion type. The coaxial extrusion platform was also used to extrude and culture human hepatoma HepaRG cells within small diameter filaments (sub-25 μm), which sustained viability for 14 days, thus demonstrating extrusion using multiple cell types. The preliminary viability of the coaxial extruder to be utilised in drug testing applications has been assessed by performing hepatotoxicity tests of HepaRG cells and obtaining LC50 values similar to published data for three compounds. An additional assay of CYP450 enzyme activity further validated this platform by demonstrating strong CYP3A4 activity on induction with rifampicin, a known CYP3A4 inducer. To conclude, a coaxial extrusion platform was created, wherein fine diameter (sub-20 μm) collagen filaments containing adipose-derived stem cells were fabricated and cultured, retaining high viability (> 90%) over multiple days (> 21 days). This achievement was aided by the tuning of material flow rates, alginate shell cross-linking parameters and collagen concentration. Finally, fine diameter collagen filaments containing human hepatoma HepaRG cells (sub-25 μm) were also extruded and cultured at high viability for 14 days. These HepaRG-containing filaments were also exposed to different hepatotoxic compounds at varying concentrations to obtain LC50 values comparable to literature, thus providing preliminary validation of the coaxial extrusion system to be used as a drug testing platform.
- Advisor / supervisor
- Shu, Will
- Resource Type
- DOI
- Date Created
- 2022
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PDF of thesis T16487 | 2023-02-28 | Public | Download |