How preparation and modification parameters affect PB‐PEO polymersome properties in aqueous solution

The effect of formation and modification methods on the physical properties of polymersomes is critical for their use in applications relying on their ability to mimic functional properties of biological membranes. In this study, we compared two formation methods for polymersomes made from polybutadiene‐polyethylene oxide diblock copolymers: detergent‐mediated film rehydration (DFR) and solvent evaporation (SE). DFR‐prepared polymersomes showed a three times higher permeability compared to SE‐prepared polymersomes as revealed by stopped‐flow light scattering. SE‐prepared polymersomes broke down faster to structures <50 nm diameter when processed with extrusion, which was more pronounced at 5 mg mL^?1, compared to 10, 20, and 25 mg mL^?1. Our results indicate that the bilayer of SE‐prepared polymersomes has a lower apparent fluidity. We also investigated the role of n‐octyl‐β‐d ‐glucopyranoside (OG), a detergent typically used for reconstitution of membrane proteins into lipid bilayers. Specifically, we compared dialysis and biobeads for OG removal to investigate the influence of these methods on bilayer conformation and polymer rearrangement following detergent removal. There was no significant difference found between method, temperature, or time within each method. Our findings provide insight on how biocompatible polymersome production affects the physical properties of the resulting polymersomes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1581–1592     

How molecular internal‐geometric parameters affect PB‐PEO polymersome size in aqueous solution

Amphiphilic polybutadiene polyethylene oxide (PB‐PEO) is one of the best known chemistries to form stable vesicular morphologies, stated as polymersomes, in aqueous environment. Mimicking cell membranes, these structures self‐assemble in an “amphiphilic window” determined by 0.15 < f < 0.35 where f is the ratio between the hydrophilic block volume and the entire diblock volume. However the polymersome size distribution also depends on molecular weight (M_n) and in order to gain insight on how f and M_n together determine polymersome size, we prepared PB‐PEO diblock copolymers with different block lengths and analyzed vesicle morphology via Dynamic light scattering (DLS) and Freeze‐fracture transmission electron microscopy (FF‐TEM). We found three main regimes: high f / low M_n with polymersomes of mixed diameter, high f / high M_n with mainly large polymersomes and low f, with mainly small polymersomes. In the first region, the polymersomes are highly polydisperse. There is a tendency towards increased diameter with increasing f and M_n. Taken together our findings can help to identify how polymersome self‐assembly can be controlled to achieve size distribution specificity alleviating the need for subsequent tuning of size via extrusion. This can pave the way for cost‐effective upscaling of polymersome production for biomedical and biomimetic applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 699–708     

Development and application of a system for analysis of mixed cultures of microorganisms

Development and application of a system for real-time quantitative assessment of individual cell activities in a mixed culture system was investigated. This was based on a concept that the activities of individual cells in a mixed culture can be assessed if the cells are physically separated (in separate compartments) in a vessel while the culture conditions, including the broth components, are maintained the same in all the compartments during the cultivation. On this basis, three different apparatus (M-1, M-2, and M-3) were constructed using various types of membranes. In terms of mass transfer characteristics and membrane fouling, the M-3 apparatus was the most effective system for analysis of mixed cultures at high cell densities. With the M-3 apparatus, the interrelationships between two alcohol-producing strains (Saccharomyces cerevisiae and Zymomonas mobilis) under anaerobic and aerobic conditions were studied. Under anaerobic condition, except for possible competition for nutrients, there were no significant effects of the activities of one microorganism on the other. However, under aerobic condition, amensalism was observed because acetaldehyde that was produced by Z. mobilis inhibited the growth of S. cerevisiae.