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Issue 18, 2019
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Photo-responsive liposomes composed of spiropyran-containing triazole-phosphatidylcholine: investigation of merocyanine-stacking effects on liposome–fiber assembly-transition

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Abstract

A spiropyran-containing triazole-phosphatidylcholine (SPTPC) was synthesized through a copper-catalyzed azide alkyne cyclo-addition (CuAAC) reaction. In water, SPTPCs self-assembled and a spontaneous spiropyran-to-merocyanine (SP-to-MC) isomerization occurred, resulting in coexistence of liposomes and fibers, and switching from the spiropyran (SP) to the merocyanine (MC) isomeric structure induced a reversible transition between these molecular assemblies. Study of the self-assembly of SPTPCs and photo-induced liposome–fiber assembly-transition revealed that the presence of MC enabled additional inter-membrane interaction during self-assembly and that the MC-stacking effect was the driving force for the assembly-transition. Exposure to UV light induced switching from SP to MC, where the planar structure of MC and the confinement of MC led to enhanced MC-stacking. The effect of MC-stacking was both advantageous and disadvantageous: MC-stacking perturbed the hydrophobic phase in the bilayer membrane and facilitated the liposome-to-fiber transition, otherwise the MC-stacking retarded switching of MC to SP, and caused an incomplete recovery of MC to SP during fiber-to-liposome recovery, thus a fatigue of SP was induced by MC-stacking during the liposome-to-fiber transition cycle. To decrease the intermolecular interactions and suppress MC-stacking, photo-inert triazole-phosphatidylcholine (TPC) was incorporated to prepare two-component TPC/SPTPC-liposomes, which exhibited better recovery kinetics. The photo-adaptive behavior of TPC/SPTPC-liposomes confirmed the disturbance of bilayer membranes by inter-membrane MC-stacking and the formation of MCTPC-enriched phases in the bilayer membrane.

Graphical abstract: Photo-responsive liposomes composed of spiropyran-containing triazole-phosphatidylcholine: investigation of merocyanine-stacking effects on liposome–fiber assembly-transition

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Publication details

The article was received on 26 Oct 2018, accepted on 12 Apr 2019 and first published on 17 Apr 2019


Article type: Paper
DOI: 10.1039/C8SM02181C
Soft Matter, 2019,15, 3740-3750

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    Photo-responsive liposomes composed of spiropyran-containing triazole-phosphatidylcholine: investigation of merocyanine-stacking effects on liposome–fiber assembly-transition

    D. Zhang, P. K. Shah, H. R. Culver, S. N. David, J. W. Stansbury, X. Yin and C. N. Bowman, Soft Matter, 2019, 15, 3740
    DOI: 10.1039/C8SM02181C

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