The same trends were observed – The Capto family showed the highest resistance to deformation (Capto Adhere- 2.7, Capto Q- 1.92 1/%min-1) through to Sepharose CL-6B, Sepharose 4 Fast Flow and Sepharose CL-4B which exhibited the lowest slurry resistances (0.59, 0.4, 0.3 1/%min-1 respectively). The technique was applied to the nine studied resins and correlated with the results obtained using the pressure-flow technique. Dynamic mechanical analysis (DMA) was therefore developed as a novel technique in this field to address these limitations and allowed for further mechanical characterisation based on the viscoelastic properties using 1ml of resin. There were practical limitations in using the pressure-flow technique alone to for mechanical characterisation, including the large quantity of chromatography resin and buffers and the stringent criteria required to pack a column. The results showed that the Capto family had the highest critical velocities (Capto Adhere- 492, Capto Q- 477 cm/hr), whilst Sepharose CL-6B, Sepharose 4 Fast Flow and Sepharose CL-4B had the lowest critical velocity values (283, 204, 149 cm/hr respectively). Scanning electron microscopy (SEM) was used to image the structural properties of nine widely used agarose-based chromatography resins before use while pressure-flow analysis was used to characterise the mechanical properties of the same fresh resins. By understanding this, there is significant potential for facilitating timely and improved decisions in large-scale chromatographic operations, maximising resin lifetime whist maintaining acceptable column performance.
This thesis, completed in collaboration with Eli Lilly & Co., aims to understand and assess the structural and mechanical changes that occur as agarose-based chromatography resins are exposed to different bioprocessing conditions in an attempt to explore the mechanisms by which different resins age.
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