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

Persistent organic pollutants (POPs) are a class of organic compounds that can accumulate in biological and ecological environments due to their resistive nature to chemical, thermal and photo degradation. Polychlorinated biphenyls (PCBs) are a class of man-made POPs 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 fail or are decommissioned, PCBs are released into the soil, migrate to the water table, and eventually spread to nearby ecosystems by rain and wind. The stability of POPs and specifically PCBs leave few options for environmental waste removal. Conventionally, liposomes have been used for their drug delivery capabilities, but here we have chosen to investigate their capability in removing this class of emerging environmental pollutants. 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. Liposomes were prepared using probe-tip sonication for both direct and passive incorporation of the HCBP compound. Assimilation was assessed using both differential scanning calorimetry and UV-Vis spectroscopy. After direct incorporation of HCBP the phase transition temperature, Tm, decreased from 40.8 {degrees}C to 37.4 {degrees}C. A subsequent UV-Vis analysis of HCBP by both direct and passive incorporation showed an increase in HCBP incorporation proportionate to the length of exposure time up to 24 hours and relative to the initial quantity present during the direct incorporation. Together the decrease in Tm and increase in absorbance are indicative of HCBP incorporation and further demonstrate the potential for their use as a method of sustainable environmental cleanup.