Sterilizing-grade Filters Research Articles

Adsorption Behavior of a Surfactant and a Monoclonal Antibody to Sterilizing-Grade Filters

Formulations of therapeutic proteins usually contain a surfactant such as polysorbate 80 to protect them against interfacial stresses. Since surfactants may interact with surfaces, the aim of the present work was to study the adsorption behavior of low concentrations of polysorbate 80 and of a monoclonal antibody during sterile filtration. Lab-scale tests were performed to study the adsorption behavior of a monoclonal antibody to different filter materials (PVDF, PES, CA, and Nylon) from different suppliers. Subsequently, protein and polysorbate 80 adsorption were tested in manufacturing scale experiments. It was found that the extent of protein adsorption differed with filter materials, but also with different suppliers. Prominently, Nylon filters showed the highest degree of protein adsorption. In manufacturing-scale filtration experiments, significant adsorption of polysorbate 80 to sterilizing-grade filters was found. Thus, the adsorption of both protein and polysorbate to filters should be taken into consideration in the formulation and manufacturing process and assessed on a case-by-case basis depending on the manufacturing process set-up.

Filter preconditioning enables representative scaled-down modelling of filter capacity and viral clearance by mitigating the impact of virus spike impurities.

Endogenous and adventitious virus removal by size-exclusion membrane filtration is a critical dedicated step in an overall viral clearance strategy employed by biologics manufacturers as required by industry regulators. However, the addition of impurities from virus spike preparations used in validation studies can significantly reduce filter capacity, resulting in an oversized and suboptimal virus filtration step. The hydraulic filter performance and virus retention observed in conventional scaled-downed validation models may not necessarily represent performance observed during process development, nor be predictive of manufacturing performance. Using filter flow decay as a relevant processing endpoint, an alternative and more comprehensive approach to virus filter validation has been developed to overcome the limitations imposed by virus spike impurities. With a model feedstream, we have demonstrated comparable virus removal using the conventional virus spiking approach and a complementary preconditioned virus challenge. Similar to a currently accepted method used in the validation of sterilizing-grade filters, this method entails processing non-spiked feed to a volumetric throughput target, followed by processing virus-spiked feed to a final flow decay endpoint to determine viral clearance. This comprehensive approach yields predictive virus retention data under protein-dominant fouling conditions that better model the hydraulic performance of the manufacturing-scale virus filtration operation.

Behaviour of Polysorbate 20 During Dialysis, Concentration and Filtration Using Membrane Separation Techniques

During formulation development of a therapeutic protein, combinations of buffers, pH and excipients need to be tested. As the protein bulk solution used for formulation development usually contains a buffer component at a defined pH and potentially one or more excipients already, this bulk requires to be processed. In case low concentrations of non-ionic surfactants, for example polysorbate 20, are already present in the bulk, the surfactant needs to be removed in lab-scale for further development use. The scope of the work was to study the behaviour of low concentrations of polysorbate 20 during membrane separation processes. The first part focuses on evaluating the behaviour of polysorbate 20 during a dialysis process, whereas the second part analyses concentration changes of polysorbate during a membrane concentration process using a stirred cell. The third part analyses potential membrane absorption of polysorbate at sterilizing-grade filters. In conclusion, it was found that polysorbate could not be significantly reduced during a dialysis process and accumulated during a membrane concentration process in unreproducable manner. During sterile filtration, no significant influence on the concentration of polysorbate was measurable. In any case, it is recommendable to quantify the concentration of polysorbate during critical membrane process steps in pharmaceutical industry.

Effects of sterilizing-grade filters on the physico-chemical properties of onion-like vesicles

Spherulites™ are new promising multilamellar vesicles that we study in a drug delivery context. The sterilization of spherulites™ suspensions is a necessary step before biological tests and later, before pharmaceutical applications (for example, parenteral or local injections). Among all sterilizing operations, the filtration through 0.22 μm sterilizing-grade filters (of the type Millex ® (Ø 4 mm) by Millipore) is easy and rapid, and we decided to study it as a mean to obtain sterile suspensions. The spherulites™ diameter is usually comprised between 0.2 and 0.5 μm but bigger vesicles occur and reach Ø 1 μm. The effects of such filters on vesicles’ size and lipids’ concentration were then compromised. After examination of this challenging operation, results proved that the sterilizing filtration had no effect on these two parameters whatever the formulation chosen. Then, the possible release of amaranth, an encapsulated hydrophilic dye was followed. With the formulations and in spite of a filter diameter inferior to that of the vesicles, the encapsulation yields were not significantly different before and after the filtration and no leakage could be detected. Finally, the spherulites™’ functionality after sterilizing filtration was studied under the chemical angle: vesicles containing an amphiphilic reactive anchor (CholE 3ONH 2) were still able to bind covalently a peptidic molecular recognition pattern. The ligation was quantified by fluorimetry as high as for non-filtrated suspensions. Thus, though spherulites™ can present a diameter superior to that of the sterilizing filters, their passage through them do not alter the physico-chemical properties of these vesicles.

Sterilizing grade filters for bioscience market

Millipore Corp has launched two new sterilizing grade filters for application in the bioscience sector. The Multilayer Durapore 0.45 μm/0.22 μm cartridge filter and the Express SHF hydrophilic 0.2 μm filter can both be used in a wide range of biopharmaceutical applications. This is a short news story only. Visit www.filtsep.com for the latest filtration industry news.

Adsorption of Benzalkonium Chloride by Filter Membranes: Mechanisms and Effect of Formulation and Processing Parameters

The purpose of this study was to elucidate the mechanism(s) of adsorption of benzalkonium chloride (BAK) by filter membranes and to determine the effect of formulation and processing parameters on the adsorption of BAK. Six different sterilizing grade filter membranes were used in this study. Adsorption was monitored by passing an aqueous solution of BAK at pH 6 through a 47-mm (14.2 cm2 effective filter area) disk filter membrane and measuring the UV absorption of the filtrate with a UV micro flow cell. Hydrophobic and/or electrostatic forces were chiefly responsible for adsorption. The adsorption properties of each filter membrane could be related to its composition. Membranes that were hydrophilic and nonionic or hydrophilic and cationic adsorbed little BAK. However, membranes that were hydrophobic or anionic exhibited significant BAK adsorption. Adsorption followed the Langmuir equation and adsorptive capacities ranged from 116 to 429 μg/47 mm membrane (8.17–30.23 μg/cm2). Formulation factors studied included the concentration of BAK, the presence of a tonicity-modifying agent (sodium chloride, mannitol, glycerin), and the presence of a chelating agent (edetate disodium). The greatest increase in adsorption of BAK occurred when sodium chloride or edetate disodium was used with membranes that contained cationic sites. The effects of flow rate, temperature, autoclaving, interrupting the flow, and presaturating the filter membrane were the processing parameters studied. The rate of adsorption was inversely related to flow rate and the extent of adsorption was inversely related to temperature. Presaturation of the filter membrane with BAK was an effective method to reduce the adsorption of BAK during filtration.