Biology subjects

Rieth, M. D.

Publications and source records attributed to Rieth, M. D..

3 recordsLinked to original sources

bioRxiv2019

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.

biophysics↗

bioRxiv2019

Preparation of DPPC liposomes using probe-tip sonication: investigating intrinsic factors affecting temperature phase transitions

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.

biophysics↗

bioRxiv2018

A novel lipid-polymer system with unique properties has potential in drug delivery and biotechnology applications

Bicelles have been demonstrated to be a valuable tool for studying membrane protein interactions and structure in vitro. They are distinguished by a distinct lipid bilayer that mimics the plasma membrane of cells making it more native-like than its detergent micelle counter-part. Bicelles are typically comprised of a long-chain phospholipid such as dimyristoylphosphatidylcholine (DMPC) and a short-chain phospholipid such as dihexanoylphosphatidylcholine (DHPC). When mixed together in solution DMPC-DHPC bicelles assume a discoidal structure comprised of a heterogeneous arrangement where the short-chain lipids gather around the rim of the disk and the long-chain lipids form the flat, planar, bilayer region. In this study, the nonionic surfactant, C8E5, was used to prepare mixtures with DMPC to determine if it adopts properties similar to bicelles with a q [≥] 0.5. At q [≥] 0.5, DMPC-DHPC bicelles are bilayered and DMPC is sequestered from the detergent micelle-like DHPC. Mixtures of DMPC and C8E5 were prepared at various q values, a parameter used to describe the mole ratio of DMPC to DHPC in the preparation of bicelles. Employing biophysical methods like dynamic light scattering, 31P-NMR and analytical ultracentrifugation, properties of these lipid-detergent complexes are described. Interestingly they adopted a spherical-shaped micellar structure morphology and did not assume a discoidal shape typical of bicelles at q [≥] 0.5. However, they appear to retain bilayer-like properties that may prove beneficial for in vitro biophysical studies of membrane proteins.

biophysics↗