title: Using fluorescence lifetime imaging microscopy to monitor theranostic nanoparticle uptake and intracellular doxorubicin release.
abstract: We describe the synthesis of iron oxide nanoparticles (IONPs) with excellent colloidal stability in both water and serum, imparted by carefully designed grafted polymer shells. The polymer shells were built with attached aldehyde functionality to enable the reversible attachment of doxorubicin (DOX) via imine bonds, providing a controlled release mechanism for DOX in acidic environments. The IONPs were shown to be readily taken up by cell lines (MCF-7 breast cancer cells and H1299 lung cancer cells), and intracellular release of DOX was proven using in vitro fluorescence lifetime imaging microscopy (FLIM) measurements. Using the fluorescence lifetime difference exhibited by native DOX (~1 ns) compared to conjugated DOX (~4.6 ns), the intracellular release of conjugated DOX was in situ monitored in H1299 and was estimated using phasor plot representation, showing a clear increase of native DOX with time. The results obtained from FLIM were corroborated using confocal microscopy, clearly showing DOX accumulation in the nuclei. The IONPs were also assessed as MRI negative contrast agents. We observed a significant change in the transverse relaxivity properties of the IONPs, going from 220 to 390 mM(-1) s(-1), in the presence or absence of conjugated DOX. This dependence of MRI signal on IONP-DOX/water interactions may be exploited in future theranostic applications. The in vitro studies were then extended to monitor cell uptake of the DOX loaded IONPs (IONP@P(HBA)-b-P(OEGA) + DOX) into two 3D multicellular tumor spheroids (MCS) grown from two independent cell lines (MCF-7 and H1299) using multiphoton excitation microscopy.
authors.affiliation: Australian Centre for Nanomedicine, University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: Johan S
authors.initials: JS
authors.lastname: Basuki
authors.forename: Hien T T
authors.initials: HT
authors.lastname: Duong
authors.forename: Alexander
authors.initials: A
authors.lastname: Macmillan
authors.forename: Rafael B
authors.initials: RB
authors.lastname: Erlich
authors.forename: Lars
authors.initials: L
authors.lastname: Esser
authors.forename: Mia C
authors.initials: MC
authors.lastname: Akerfeldt
authors.forename: Renee Megan
authors.initials: RM
authors.lastname: Whan
authors.forename: Maria
authors.initials: M
authors.lastname: Kavallaris
authors.forename: Cyrille
authors.initials: C
authors.lastname: Boyer
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Davis
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003102:Colloids / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry; D004317:Doxorubicin / Q000008:administration & dosage*; D004337:Drug Carriers; D005290:Ferric Compounds / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D018613:Microscopy, Confocal; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D011108:Polymers / Q000737:chemistry; D018874:Spheroids, Cellular; D013818:Thermogravimetry; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D003102:Colloids; D003287:Contrast Media; D004337:Drug Carriers; D005290:Ferric Compounds; D011108:Polymers; C000499:ferric oxide; D004317:Doxorubicin