title: Monitoring the Collapse of pH-Sensitive Liposomal Nanocarriers and Environmental pH Simultaneously: A Fluorescence-Based Approach.
abstract: Nowadays, the encapsulation of therapeutic compounds in so-called carrier systems is a very smart method to achieve protection as well as an improvement of their temporal and spatial distribution. After the successful transport to the point of care, the delivery has to be released under controlled conditions. To monitor the triggered release from the carrier, we investigated different fluorescent probes regarding their response to the pH-induced collapse of pH-sensitive liposomes (pHSLip), which occurs when the environmental pH falls below a critical value. Depending on the probe, the fluorescence decay time as well as fluorescence anisotropy can be used equally as key parameters for monitoring the collapse. Especially the application of a fluorescein labeled fatty acid (fPA) enabled the monitoring of the pHSLips collapse and the pH of its microenvironment simultaneously without interference. Varying the pH in the range of 3 < pH < 9, anisotropy data revealed the critical pH value at which the collapse of the pHSLips occurs. Complementary methods, e.g., fluorescence correlation spectroscopy and dynamic light scattering, supported the analysis based on the decay time and anisotropy. Additional experiments with varying incubation times yielded information on the kinetics of the liposomal collapse.
authors.affiliation: Physical Chemistry, Institute of Chemistry, University of Potsdam , Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Sören
authors.initials: S
authors.lastname: Draffehn
authors.affiliation: Physical Chemistry, Institute of Chemistry, University of Potsdam , Karl-Liebknecht-Str. 24-25, 14476 Potsdam-Golm, Germany.
authors.forename: Michael U
authors.initials: MU
authors.lastname: Kumke
mesh_terms: D004337:Drug Carriers / Q000737:chemistry*; D016503:Drug Delivery Systems / Q000379:methods; D005227:Fatty Acids / Q000737:chemistry; D005452:Fluoresceins / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D004337:Drug Carriers; D005227:Fatty Acids; D005452:Fluoresceins; D005456:Fluorescent Dyes; D008081:Liposomes
keywords: drug carrier system; fluorescence anisotropy; fluorescence correlation spectroscopy; intracellular pH indicator; pH-sensitive liposome; selective drug release; time-resolved fluorescence spectroscopy