Investigation of DPPC liposomes reveals their capability to entrap Aroclor 1260, an emerging environmental pollutant

Abstract

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