TY - JOUR
T1 - Triggerable plasmalogen liposomes
T2 - Improvement of system efficiency
AU - Thompson, David H.
AU - Gerasimov, Oleg V.
AU - Wheeler, Jefferey J.
AU - Rui, Yuanjin
AU - Anderson, Valerie C.
N1 - Funding Information:
This work was supported by grants from the Whitaker Foundation and the Purdue Research Foundation (D.H.T.) and by a grant from the National Research Council as part of the Cooperation in Applied Science and Technology Visiting Scientist Program (D.H.T./O.V.G.). The helpful discussions and kind hospitality provided by Pieter Cullis of the University of British Columbia during a sabbatical leave (D.H.T.) are gratefully acknowledged. The authors also thank Barbara L.-S. Mui and Kim Wong for assistance with preliminary electron microscopy experiments and Donald Eagle, Steven Funk, and Yuanjin Rui for sensitizer and plasmenylcholine syntheses.
PY - 1996/2/21
Y1 - 1996/2/21
N2 - A photoactivated liposome release system that is generally applicable for triggered release of encapsulated hydrophilic materials is described. This approach to phototriggered release, derived from the known effects of plasmalogen photooxidation on membrane permeability in whole cells and model membrane systems, relies on producing a lamellar phase change or increase in permeability upon cleaving its constitutive lipids to single-chain surfactants using 630-820 nm light to sensitize the photooxidation of the plasmalogen vinyl ether linkage. Semi-synthetic plasmenylcholine liposomes containing encapsulated calcein and a membrane-bound sensitizer, such as zinc phthalocyanine, tin octabutoxyphthalocyanine, or bacteriochlorophyll a, were prepared by extrusion. Irradiation of air-saturated liposome solutions enhanced membrane permeability toward calcein and Mn2+ and promoted membrane fusion processes compared to non-irradiated or anaerobic controls. Bacteriochlorophyll a sensitization produced the fastest observed photoinitiated release rate from these liposomes (100% calcein release in less than 20 min; 800 nm irradiation at 300 mW); the observed release rate was two orders of magnitude slower for egg lecithin liposomes prepared and irradiated under identical experimental conditions. Liposome aggregation, interlipidic particle formation, and membrane fusion between adjoining liposomes was observed by 31P-NMR, freeze-fracture/freeze-etch TEM, and cryo-TEM as a function of irradiation time. The use of near-infrared sensitizers and the capacity of photolyzed plasmenylcholine liposomes to undergo membrane fusion processes make photodynamic therapy with these liposome-borne sensitizers an attractive adjunct to biochemical targeting methods.
AB - A photoactivated liposome release system that is generally applicable for triggered release of encapsulated hydrophilic materials is described. This approach to phototriggered release, derived from the known effects of plasmalogen photooxidation on membrane permeability in whole cells and model membrane systems, relies on producing a lamellar phase change or increase in permeability upon cleaving its constitutive lipids to single-chain surfactants using 630-820 nm light to sensitize the photooxidation of the plasmalogen vinyl ether linkage. Semi-synthetic plasmenylcholine liposomes containing encapsulated calcein and a membrane-bound sensitizer, such as zinc phthalocyanine, tin octabutoxyphthalocyanine, or bacteriochlorophyll a, were prepared by extrusion. Irradiation of air-saturated liposome solutions enhanced membrane permeability toward calcein and Mn2+ and promoted membrane fusion processes compared to non-irradiated or anaerobic controls. Bacteriochlorophyll a sensitization produced the fastest observed photoinitiated release rate from these liposomes (100% calcein release in less than 20 min; 800 nm irradiation at 300 mW); the observed release rate was two orders of magnitude slower for egg lecithin liposomes prepared and irradiated under identical experimental conditions. Liposome aggregation, interlipidic particle formation, and membrane fusion between adjoining liposomes was observed by 31P-NMR, freeze-fracture/freeze-etch TEM, and cryo-TEM as a function of irradiation time. The use of near-infrared sensitizers and the capacity of photolyzed plasmenylcholine liposomes to undergo membrane fusion processes make photodynamic therapy with these liposome-borne sensitizers an attractive adjunct to biochemical targeting methods.
KW - Controlled release
KW - Drug delivery
KW - Electron microscopy
KW - Interlipidic particle
KW - Light-triggerable liposome
KW - Liposome
KW - Photodynamic therapy
KW - Photooxidation
KW - Plasmalogen
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U2 - 10.1016/0005-2736(95)00210-3
DO - 10.1016/0005-2736(95)00210-3
M3 - Article
C2 - 8624357
AN - SCOPUS:0030025010
SN - 0005-2736
VL - 1279
SP - 25
EP - 34
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 1
ER -