title: pH-sensitive stearoyl-PEG-poly(methacryloyl sulfadimethoxine) decorated liposomes for the delivery of gemcitabine to cancer cells.
abstract: Novel, acid-sensitive liposomes that respond to physiopathological pH for tumour targeting applications were obtained by surface decoration with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)] (mPEG-DSPE) and stearoyl-poly(ethylene glycol)-poly(methacryloyl sulfadimethoxine) copolymer (stearoyl-PEG-polySDM). The pH-sensitive stearoyl-PEG-polySDM copolymer contained an average of seven methacryloyl sulfadimethoxines per molecule and was found to possess an apparent pKa of 7.2. Preliminary cloud point studies showed that the hydrophilic/hydrophobic copolymer conversion occurred at pH 7.0. The copolymer was soluble above pH 7.0 and underwent aggregation at lower pH. Liposome formulations were prepared with 0.2:0.6:100, 0.5:1.5:100 and 1:3:100 mPEG-DSPE/stearoyl-PEG-polySDM/lipids molar ratios. All of the liposome formulations were stable at pH 7.4, even in the presence of foetal bovine serum, but they underwent rapid size increase at pH 6.5. TEM analysis showed that, at pH 6.5, the formulations coated with a stearoyl-PEG-polySDM/lipids molar ratio greater than 1:100 underwent aggregation. At pH 7.4, the liposomes showed negative zeta potential that significantly decreased after incubation at pH 6.5. Cell-culture studies indicated that the liposomes were not toxic up to 10mg/mL. Fluorescence spectroscopy, cytofluorimetry and confocal microscopy showed that at pH 6.5, the incubation of MCF-7 tumour cells with fluorescein-labelled 1:3:100 mPEG-DSPE/stearoyl-PEG-polySDM/lipids molar ratio liposomes resulted in time-dependent cell association, while at pH 7.4 the cell interaction was significantly lower. The same pH-responsive liposome formulation loaded with gemcitabine (98.2±4.7nmol gemcitabine/lipid μmol loading capacity) was stable at pH 7.4 for several hours, while at pH 6.5 it rapidly aggregated. At pH 6.5, these liposomes displayed higher cytotoxicity than at pH 7.4 or compared to non-responsive control liposomes at both incubation pH. Notably, treatment with free gemcitabine did not yield cytotoxic effects, indicating that the carrier can efficiently deliver the anticancer drug to the cytosolic compartment.
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Bersani
authors.affiliation: Department of Biology, University of Padova, Padova, Italy.
authors.forename: Marian
authors.initials: M
authors.lastname: Vila-Caballer
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Brazzale
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Barattin
authors.affiliation: Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy. Electronic address: stefano.salmaso@unipd.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Salmaso
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage* / Q000494:pharmacology; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004337:Drug Carriers / Q000138:chemical synthesis / Q000737:chemistry*; D004355:Drug Stability; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008081:Liposomes; D061986:MCF-7 Cells; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D010316:Particle Size; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000138:chemical synthesis / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013449:Sulfonamides / Q000138:chemical synthesis / Q000737:chemistry*; D013499:Surface Properties; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D004337:Drug Carriers; D008081:Liposomes; D011109:Polymethacrylic Acids; D013449:Sulfonamides; C000599415:stearoyl-poly(ethylene glycol)-poly(methacryloyl sulfadimethoxine) copolymer; D003841:Deoxycytidine; D011092:Polyethylene Glycols; D000093542:Gemcitabine
keywords: Active drug delivery; Anticancer drug delivery; Gemcitabine; Selective drug targeting; Tumour targeting; pH-responsive liposomes