No abstract

Liposomes are an important tool and have gained much attention for their promise as an effective means of delivering small therapeutic compounds to targeted sites. In an effort to establish an effective method to produce liposomes from the lipid, dipalmitoyl-phosphatidylcholine or DPPC, we have found important aspects that must be taken into consideration. Here, we used probe-tip sonication to prepare liposomes on a batch scale. During this process we uncovered interesting steps in their preparation that altered the thermodynamic properties and phase transitions of the resulting liposome mixtures. Using differential scanning calorimetry to assess this we found that increasing the sonication time had the most dramatic effect on our sample, producing almost an entirely separate phase transition relative to the main phase transition. This result is consistent with reports from the current literature. We also highlight a smaller transition, which we attribute to traces of unincorporated lipid that seems to gradually disappear as the total lipid concentration decreases. Overall, sonication is an effective means of producing liposomes, but we cannot assert this method is optimal in producing them with precise physical properties. Here we highlight the physical effects at play during this process.

Polychlorinated biphenyls (PCBs) are a class of man‐made persistent organic pollutants that saw wide‐spread use in commercial and industrial infrastructure as both an insulator and coolant in electrical transformers and capacitors. 2,2’,3,3′,4,4’‐hexachlorobiphenyl (HCBP) was one of the most widely produced PCBs. As these mechanical structures failed or are discarded, PCBs are released into the soil, migrate to the water table, and eventually spread to nearby ecosystems by rain and wind. The remarkable chemical stability of PCBs leave few options for environmental waste and water removal, yet they are becoming increasingly concerning as they pose potential health risks to individuals who become exposed to them. Conventionally, liposomes have been used for their promising drug delivery capabilities. Here, we investigated their potential for the entrapment and removal of HCBP. Liposomes are small, nonpolar lipid bi‐layered aggregates capable of capturing a wide variety of both polar and nonpolar compounds. Dipalmitoylphosphatidylcholine (DPPC) is a well‐characterized lipid that can be derived from natural sources. It is a phospholipid typically found as a major component of pulmonary surfactant mixtures. To assess the utility of liposomes prepared with pure DPPC in capturing PCBs, they were prepared using probe‐tip sonication for both direct and passive incorporation of HCBP. Incorporation was assessed using a combination of differential scanning calorimetry and UV‐Vis spectroscopy. For direct incorporation liposome stability generally decreased compared to pure DPPC liposomes based on a corresponding decrease in the phase transition temperature, Tm, from 40.8 °C to 37.4 °C. An analysis of passive incorporation using UV‐Vis spectroscopy showed an increase in the incorporation of HCBP proportionate to the length of exposure time up to 24 hours. Together our calorimetry and spectroscopic measurements are indicative of HCBP incorporation into liposomes and shows promising potential for use in sustainable environmental cleanup and water treatment technologies. Future studies aim to further explore their technological capabilities by optimizing their thermal and mechanical stability.

32Persistent organic pollutants (POPs) are a class of organic compounds that can accumulate in biological 33 and ecological environments due to their resistive nature to chemical, thermal and photo degradation. 34Polychlorinated biphenyls (PCBs) are a class of man-made POPs that saw wide-spread use in commercial 35 and industrial infrastructure as both an insulator and coolant in electrical transformers and capacitors. 36 2,2',3,3',4,4'-hexachlorobiphenyl (HCBP) was one of the most widely produced PCBs. As these 37 mechanical structures fail or are decommissioned, PCBs are released into the soil, migrate to the water 38 table, and eventually spread to nearby ecosystems by rain and wind. The stability of POPs and specifically 39 PCBs leave few options for environmental waste removal. Conventionally, liposomes have been used for 40 their drug delivery capabilities, but here we have chosen to investigate their capability in removing this 41 class of emerging environmental pollutants. Liposomes are small, nonpolar lipid bi-layered aggregates 42 capable of capturing a wide variety of both polar and nonpolar compounds. 43 Dipalmitoylphosphatidylcholine (DPPC) is a well-characterized lipid that can be derived from natural 44 sources. It is a phospholipid typically found as a major component of pulmonary surfactant mixtures. 45Liposomes were prepared using probe-tip sonication for both direct and passive incorporation of the HCBP 46 compound. Assimilation was assessed using both differential scanning calorimetry and UV-Vis 47 spectroscopy. After direct incorporation of HCBP the phase transition temperature, Tm, decreased from 48 40.8 °C to 37.4 °C. A subsequent UV-Vis analysis of HCBP by both direct and passive incorporation 49 showed an increase in HCBP incorporation proportionate to the length of exposure time up to 24 hours and 50 relative to the initial quantity present during the direct incorporation. Together the decrease in Tm and 51 increase in absorbance are indicative of HCBP incorporation and further demonstrate the potential for their 52 use as a method of sustainable environmental cleanup. 53 54 55 56 57 according to the calculated ratios of HCBP:DPPC and summarized in Table 1. The dried lipid films were 131 stored long-term at -20 °C. 132

splitting of a membrane compartment, is a central theme in biology that manifests during cell division, organelle biogenesis and vesicular transport. Fission involves the local application of forces to bend and constrict or thin down a membrane tube. Since bending requires the bilayer to deviate from its preferred planar configuration, fission is energetically unfavorable. Using reconstitution approaches that involve biochemical screens, we have discovered novel proteins that catalyze fission and have elucidated their mechanism and cellular functions. My talk will describe these recent developments.