Bioreactor perfusion via single-use centrifugation has fewer product quality implications than tangential flow filtration

During development of a perfusion cell culture process for the production of a therapeutic protein, tangential flow filtration (TFF) technology was evaluated for cell retention in addition to Shire’s platform single-use centrifugation technology. Unlike centrifugation TFF is based on a microfiltration membrane and thus has the potential to partially retain many biological compounds, especially when exposed to extracellular matrix proteins and antifoam emulsions (Routledge, 2012; Wu et al., 2011). Retention increases the mean residence time of product at process temperature. In the case of heat-labile molecules longer exposure to bioreactor culture temperature may correlate with changes in quality attributes. Therapeutic protein was generated from bioreactors equipped with single-use centrifuge and TFF technology for cell retention. Peak viable cell density was slightly higher using TFF, due to the moderate cell loss of centrifugation, but viability by trypan blue exclusion was slightly lower. Metabolic profiles (glucose, lactate, ammonium, glutamate) were not affected by the choice of cell retention technology. Cell specific productivity was similar for both cell retention devices; however, TFF membranes had to be changed periodically to reduce protein retention and thereby achieve the volumetric productivity of the single-use centrifuge. All measured product quality attributes, for both intermediates and drug substance (DS), were comparable between TFF and single-use centrifugation. Nevertheless, drug substance generated from bioreactors equipped with TFF had significantly decreased room-temperature stability compared to DS generated from bioreactors equipped with single-use centrifuges. DS instability of TFF lots, indicated by an increased propensity to generate low molecular weight species (LMW), was more pronounced in later harvests compared to early harvests. Analysis (HPLC-MS & peptide mapping) of degraded drug substance found molecular fragments that corresponded to the subunits of the therapeutic protein. Cleavage occurred at several sites close to the linkage molecules bridging the protein subunits. A literature search for compounds that target the cleavage sites identified metalloproteases and serine proteases as likely agonists for the observed cleavages and serine proteases were detected in a proteomics analysis of both TFF and single-use centrifuge material. While DS lot stability suffered with TFF the stability of process intermediates was found to be similar between TFF and centrifuge lots. If proteases are responsible for the observed LMW generation said proteases might have greater activity when concentrated and/or when inhibitory compounds are removed during purification. It is plausible that TFF may have contributed to either LMW generation in the cell culture or retention of a protectant moiety. Additional study is necessary to confidently posit a root cause

Ion conduction and phase morphology in sulfonate copolymer ionomers based on ionic liquid–sodium cation mixtures

A series of sulfonate based copolymer ionomers based on a combination of ionic liquid and sodium cations have been prepared in different ratios. This system was designed to improve the ionic conductivity of ionomers by partially replacing sodium cations with bulky cations that are less associated with anion centres on the polymer backbone. This provides more conduction sites for sodium to ‘hop’ to in the ionomers. Characterization showed the glass transition and 15N chemical shift of the ionomers did not vary significantly as the amount of Na+ varied, while the ionic conductivity increased with decreasing Na+ content, indicating conductivity is increasingly decoupled from Tg. Optical microscope images showed phase separation in all compositions, which indicated the samples were inhomogeneous. The introduction of low molecular weight plasticizer (PEG) reduced the Tg and increased the ionic conductivity significantly. The inclusion of PEG also led to a more homogeneous material

Mixed phase solid-state plastic crystal electrolytes based on a phosphonium cation for sodium devices

Na batteries are seen as a feasible alternative technology to lithium ion batteries due to the greater abundance of sodium and potentially similar electrochemical behavior. In this work, mixed phase electrolyte materials based on solid-state compositions of a trimethylisobutylphosphonium (P111i4) bis(trifluromethanesulphonyl)amide (NTf2) organic ionic plastic crystal (OIPC) and high concentration of NaNTf2 that support safe, sodium metal electrochemistry are demonstrated. A Na symmetric cell can be cycled efficiently, even in the solid state (at 50 °C and 60 °C), for a 25 mol% (P111i4NTf2)–75 mol% NaNTf2 composition at 0.1 mA cm−2 for 100 cycles. Thus, these mixed phase materials can be potentially used in Na-based devices under moderate temperature conditions. It is also investigated that the phase behavior, conductivity, and electrochemical properties of mixtures of NaNTf2 with this OIPC. It is observed that these mixtures have complex phase behavior. For high compositions of the Na salt, the materials are solid at room temperature and retain a soft solid consistency even at 50 °C with remarkably high conductivity, approaching that of the pure ionic liquid at 50 °C, i.e., 10−3–10−2 S cm−1

Investigating discharge performance and Mg interphase properties of an Ionic Liquid electrolyte based Mg-air battery

The performance of a primary Mg-air cell was evaluated at room temperature using a 72 mol% ethylene glycol/trihexyl(tetradecyl) phosphonium chloride ([P-6,P-6,P-6,P-14][Cl]) ionic liquid (IL) electrolyte. The cell was cycling in ambient air as well as in the presence of pure oxygen, and interestingly the cell presented much higher discharge capacity in air than in oxygen, which was attributed to the effect of water in the ambient air. When operated in ambient air, the cell showed promising discharge behaviour with a maximum rate of 0.2 mA cm(-2) and a discharge capacity of around 4.8 mAh cm(-2). When operated at a low rate 0.0075 mA cm(-2), the cell lasted for over 260 h, 10 days, at a potential above 1.3 V. Thus, the main focus of this study is the analysis of the mechanism of discharge capacity loss in this electrolyte, which revealed that, both the polarization due to the presence of a resistive Mg interphase on the anode surface and, concentration polarization due to the quick accumulation of Mg2+ ions in the IL based electrolyte are responsible. In-depth surface characterization suggested the discharge products accumulated on the Mg surface with a proposed formula [P6,6,6,14].Cl.Mg(OH)(2).9[Mg(OCH2CH2OH)Cl]. 40H(2)O most likely had a highly-crosslinked chemical structure, which were responsible for the limited ionic conductivity of the Mg interphase