TY - JOUR
T1 - Effects of titanium dioxide and zinc oxide nano-materials on lipid order in model membranes
AU - Sydor, Matthew J.
AU - Anderson, Donald S.
AU - Steele, Harmen B.B.
AU - Ross, J. B.Alexander
AU - Holian, Andrij
N1 - Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/9/1
Y1 - 2020/9/1
N2 - Engineered nano-materials (ENM) have been reported to affect lipid membrane permeability in cell models, but a mechanistic understanding of how these materials interact with biological membranes has not been described. To assess mechanisms of permeability, liposomes composed of DOPC, DOPS, or POPC, with or without cholesterol, were used as model membranes for measuring ENM-induced changes to lipid order to improve our understanding of ENM effects on membrane permeability. Liposomes were treated with either titanium dioxide (TiO2) or zinc oxide (ZnO) ENM, and changes to lipid order were measured by time-resolved fluorescence anisotropy of a lipophilic probe, Di-4-ANEPPDHQ. Both ENM increased lipid order in two lipid models differing in headgroup charge. TiO2 increased lipid order of POPC liposomes (neutral charge), while ZnO acted primarily on DOPS liposomes (negative charge). Addition of cholesterol to these models significantly increased lipid order while in some cases attenuated ENM-induced changes to lipid order. To assess the ability of ENM to induce membrane permeability, liposomes composed of the above lipids were assayed for membrane permeability by calcein leakage in response to ENM. Both ENM caused a dose-dependent increase in permeability in all liposome models tested, and the addition of cholesterol to the liposome models neither blocked nor reduced calcein leakage. Together, these experiments show that ENM increased permeability of small molecules (calcein) from model liposomes, and that the magnitude of the effect of ENM on lipid order depended on ENM surface charge, lipid head group charge and the presence of cholesterol in the membrane.
AB - Engineered nano-materials (ENM) have been reported to affect lipid membrane permeability in cell models, but a mechanistic understanding of how these materials interact with biological membranes has not been described. To assess mechanisms of permeability, liposomes composed of DOPC, DOPS, or POPC, with or without cholesterol, were used as model membranes for measuring ENM-induced changes to lipid order to improve our understanding of ENM effects on membrane permeability. Liposomes were treated with either titanium dioxide (TiO2) or zinc oxide (ZnO) ENM, and changes to lipid order were measured by time-resolved fluorescence anisotropy of a lipophilic probe, Di-4-ANEPPDHQ. Both ENM increased lipid order in two lipid models differing in headgroup charge. TiO2 increased lipid order of POPC liposomes (neutral charge), while ZnO acted primarily on DOPS liposomes (negative charge). Addition of cholesterol to these models significantly increased lipid order while in some cases attenuated ENM-induced changes to lipid order. To assess the ability of ENM to induce membrane permeability, liposomes composed of the above lipids were assayed for membrane permeability by calcein leakage in response to ENM. Both ENM caused a dose-dependent increase in permeability in all liposome models tested, and the addition of cholesterol to the liposome models neither blocked nor reduced calcein leakage. Together, these experiments show that ENM increased permeability of small molecules (calcein) from model liposomes, and that the magnitude of the effect of ENM on lipid order depended on ENM surface charge, lipid head group charge and the presence of cholesterol in the membrane.
KW - Anisotropy
KW - Liposome
KW - Model membrane
KW - Titanium dioxide
KW - Zinc oxide
UR - http://www.scopus.com/inward/record.url?scp=85083708172&partnerID=8YFLogxK
U2 - 10.1016/j.bbamem.2020.183313
DO - 10.1016/j.bbamem.2020.183313
M3 - Article
C2 - 32304756
AN - SCOPUS:85083708172
SN - 0005-2736
VL - 1862
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 9
M1 - 183313
ER -