Stabilization of Lipid Membranes through Partitioning of the Blood Bag Plasticizer Di-2-ethylhexyl phthalate (DEHP)

Abstract

The safe storage of blood is of fundamental importance to health care systems all over the world. Currently, plastic bags are used for the collection and storage of donated blood and are typically made of poly­(vinyl chloride) (PVC) plasticized with di-2-ethylhexyl phthalate (DEHP). DEHP is known to migrate into packed red blood cells (RBC) and has been found to extend their shelf life. It has been speculated that DEHP incorporates itself into the RBC membrane and alters membrane properties, thereby reducing susceptibility to hemolysis and morphological deterioration. Here, we used high-resolution X-ray diffraction and molecular dynamics (MD) simulations to study the interaction between DEHP and model POPC lipid membranes at high (9 mol %) and low (1 mol %) concentrations of DEHP. At both concentrations, DEHP was found to spontaneously partition into the bilayer. At high concentrations, DEHP molecules were found to aggregate in the aqueous phase before inserting as clusters into the membrane. The presence of DEHP in the bilayers resulted in subtle, yet statistically significant, alterations in several membrane properties in both the X-ray diffraction experiments and MD simulations. DEHP led to (1) an increase of membrane width and (2) an increase in the area per lipid. It was also found to (3) increase the deuterium order parameter, however, (4) decrease membrane orientation, indicating the formation of thicker, stiffer membranes with increased local curvature. The observed effects of DEHP on lipid bilayers may help to better understand its effect on RBC membranes in increasing the longevity of stored blood by improving membrane stability.

Blood bank storage of red blood cells increases RBC cytoplasmic membrane order and bending rigidity

“…Even though the presence of DEHP could potentially explain the observed increased stiffness in our experiments, we could not find clear evidence for the presence of DEHP molecules in the electron density of RBC cm s in our X-ray diffraction results. The upper bound of experimentally reported DEHP concentrations in blood bags is � 600 μg/ml [68], which corresponds to molar concentrations of less than 0.2 mol%, significantly smaller than what was used in [70]. While we can not rule out that the effects of DEHP were too small to be detected in this study, we speculate that the changes in the membranes' structural parameters would be even smaller than the subtle effects reported by Bider et al…”

“…The partitioning of DEHP in RBC cm s has long been suspected to change membrane properties [68,69] and contribute to the changes observed during storage. A recent study in model lipid bilayers indeed reported that DEHP can increase membrane width and area per lipid, and the deuterium order parameter, however, decrease membrane orientation, indicating the formation of thicker, stiffer membranes with increased local curvature [70]. Concentrations of DEHP in this paper were elevated, of up to 10 mol% of the lipid concentration, to emphasize the potential effects of DEHP.…”

Erythro-VLPs: Anchoring SARS-CoV-2 spike proteins in erythrocyte liposomes

“…A total of 4 simulation systems were created. All-atom simulations can provide a detailed insight into membrane structure and dynamics but are limited to small systems due to the increased computation time [50][51][52]. Coarse grained models are thus used to study large-scale membrane and protein dynamics.…”

Investigating the Permeation Mechanism of Typical Phthalic Acid Esters (PAEs) and Membrane Response Using Molecular Dynamics Simulations

“…As reported by Sici ńska (2019) [18], PAEs have the potential to induce apoptotic in human peripheral blood mononuclear cells, and one of the important characters of apoptosis is the change of membrane permeability. Bider et al found that the presence of DEHP in the bilayers will alter membrane properties, like membrane thickness, width, order parameters, and acyl chain orientation [19]. Similar results were observed in some other small molecule-membrane systems, such as butanol [20], thymol [21], propofol, and fentanyl [22].…”