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Int J Pharm. 2012 Oct 15;436(1-2):786-97. doi: 10.1016/j.ijpharm.2012.07.059. Epub 2012 Aug 2.

Poly(styrene-co-maleic acid)-based pH-sensitive liposomes mediate cytosolic delivery of drugs for enhanced cancer chemotherapy.

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  • 1School of Medical Science and Technology, Indian Institute of Technology, Kharagpur 721302, India.


pH-responsive polymers render liposomes pH-sensitive and facilitate the intracellular release of encapsulated payload by fusing with endovascular membranes under mildly acidic conditions found inside cellular endosomes. The present study reports the use of high-molecular weight poly(styrene-co-maleic acid) (SMA), which exhibits conformational transition from a charged extended structure to an uncharged globule below its pK(1) value, to confer pH-sensitive property to liposomes. The changes in the co-polymer chain conformation resulted in destabilization of the liposomes at mildly acidic pH due to vesicle fusion and/or channel formation within the membrane bilayer, and ultimately led to the release of the encapsulated cargo. The vesicles preserved their pH-sensitivity and stability in serum unlike other polymer-based liposomes and exhibited no hemolytic activity at physiological pH. The lysis of RBCs at endosomal pH due to SMA-based liposome-induced alterations in the bilayer organization leading to spherocyte formation indicated the potential of these vesicles to mediate cytosolic delivery of bio-active molecules through endosome destabilization. The SMA-loaded liposomes exhibiting excellent cytocompatibility, efficiently delivered chemotherapeutic agent 5-Fluorouracil (5-FU) within colon cancer cells HT-29 in comparison to neat liposomes. This caused increased cellular-availability of the drug, which resulted in enhanced apoptosis and highlighted the clinical potential of SMA-based vesicles.

Copyright © 2012 Elsevier B.V. All rights reserved.

[PubMed - indexed for MEDLINE]
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