Process intensification by frontal chromatography: Performance comparison of resin and membrane adsorber for monovalent antibody aggregate removal.

Aggregates are amongst the most important product-related impurities to be removed during the downstream processing of antibodies due to their potential immunogenicity. Traditional operations use cation-exchange resins in bind-elute mode for their separation. However, frontal analysis is emerging as an alternative. In this study, a three-step process development for a membrane adsorber and a resin material is carried out, allowing the comparison between the stationary phases. Based on a screening study, optimal loading conditions are determined, which show that weak binding is favored on the membrane and strong binding on the resin. Transfer of these findings to breakthrough experiments shows that at 99% pool purity the yield is higher for the membrane, while the resin can be loaded twice as high, exceeding yields of 85%. For the investigated antibody and based on a given regeneration protocol, the productivity of the two phases is similar, ranging around 200 g/(L·h). Due to the higher loading, the resin requires about one-third less buffer than the membrane. Furthermore, the implementation of a wash step after loading allows to further increase yield by about 5%. In comparison to a generic bind-elute process, productivity and buffer consumption are improved by an order of magnitude.

Impact of retrograde graft preservation in Perfadex-based experimental lung transplantation.

OBJECTIVE: Optimal preservation of postischemic organ function is a continuing challenge in clinical lung transplantation. Retrograde instillation of preservation solutions has theoretical advantages to achieve a homogeneous distribution in the lung due to perfusion of both the pulmonary and the bronchial circulation. Thus far, no systematic screening studies followed by in vivo large animal reevaluation including stereological analysis of intrapulmonary edema exist concerning the influence of retrograde preservation on postischemic lung function after preservation with low potassium dextran (LPD) solution (Perfadex). MATERIALS AND METHODS: For initial screening in an extracorporeal rat model eight lungs, each, were preserved for 4 h using antegrade or retrograde preservation with LPD solution (Perfadex; PER(ant)/PER(ret)). Respiratory and hemodynamic results after reperfusion were compared to low-potassium Euro-Collins (LPEC). For systematic reevaluation, five pig lungs, each, were preserved correspondingly for 27 h, and results were compared to sham-operated control lungs. In both models, edema formation was quantified stereologically. Statistics comprised different ANOVA models. RESULTS: In both models, use of PER(ret) resulted in significantly higher oxygenation capacity, lower inspiratory pressures, and lower amounts of intraalveolar edema as compared to PER(ant). Results of PER(ret) were not different from sham controls in the in vivo model; furthermore, a continuous retrograde elimination of blood clots from pulmonary microcirculation was noticed. CONCLUSIONS: Retrograde application of LPD solution (Perfadex) results in significant functional and histological improvement as compared to antegrade perfusion. This innovative technique can be applied very easily in clinical practice and might be an ideal adjunct to further optimize the results after lung transplantation with LPD-based graft protection.