title: Enzymatic action of phospholipase A₂ on liposomal drug delivery systems.
abstract: The overexpression of secretory phospholipase A2 (sPLA2) in tumors has opened new avenues for enzyme-triggered active unloading of liposomal antitumor drug carriers selectively at the target tumor. However, the effects of the liposome composition, drug encapsulation, and tumor microenvironment on the activity of sPLA2 are still not well understood. We carried out a physico-chemical study to characterize the sPLA2-assisted breakdown of liposomes using dye-release assays in the context of drug delivery and under physiologically relevant conditions. The influence of temperature, lipid concentration, enzyme concentration, and drug loading on the hydrolysis of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC, Tm=42°C) liposomes with snake venom sPLA2 was investigated. The sensitivity of human sPLA2 to the liposome composition was checked using binary lipid mixtures of phosphatidylcholine (PC) and phosphatidylglycerol (PG) phospholipids with C14 and C16 acyl chains. Increasing temperature (36-41°C) was found to mainly shorten the enzyme lag-time, whereas the effect on lipid hydrolysis rate was modest. The enzyme lag-time was also found to be inversely dependent on the lipid-to-enzyme ratio. Drug encapsulation can alter the hydrolysis profile of the carrier liposomes. The activity of human sPLA2 was highly sensitive to the phospholipid acyl-chain length and negative surface charge density of the liposomes. We believe our work will prove useful for the optimization of sPLA2-susceptible liposomal formulations as well as will provide a solid ground for predicting the hydrolysis profile of the liposomes in vivo at the target site.
authors.affiliation: MEMPHYS-Center for Biomembrane Physics, Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Odense, Denmark; The Lundbeck Foundation Nanomedicine Research Center for Cancer Stem Cell Targeting Therapeutics (NanoCAN), University of Southern Denmark, Odense, Denmark. Electronic address: andershh@sdu.dk.
authors.forename: Anders H
authors.initials: AH
authors.lastname: Hansen
authors.affiliation: MEMPHYS-Center for Biomembrane Physics, Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Odense, Denmark; The Lundbeck Foundation Nanomedicine Research Center for Cancer Stem Cell Targeting Therapeutics (NanoCAN), University of Southern Denmark, Odense, Denmark. Electronic address: ogm@memphys.sdu.dk.
authors.forename: Ole G
authors.initials: OG
authors.lastname: Mouritsen
authors.affiliation: MEMPHYS-Center for Biomembrane Physics, Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Odense, Denmark; The Lundbeck Foundation Nanomedicine Research Center for Cancer Stem Cell Targeting Therapeutics (NanoCAN), University of Southern Denmark, Odense, Denmark. Electronic address: arouri@memphys.sdu.dk.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Arouri
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry; D004337:Drug Carriers / Q000737:chemistry; D016503:Drug Delivery Systems / Q000379:methods; D006801:Humans; D006868:Hydrolysis; D008081:Liposomes / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D054467:Phospholipases A2 / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D013696:Temperature
chemical_list: D000970:Antineoplastic Agents; D004337:Drug Carriers; D008081:Liposomes; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D010743:Phospholipids; D054467:Phospholipases A2
keywords: Anticancer; Bio-responsive liposomes; Drug delivery system; Dye-release assay; Phospholipase A(2) enzyme; Triggered drug release