Time-Resolved Fluorescence Spectroscopy and Fluorescence Lifetime Imaging Microscopy for Characterization of Dendritic Polymer Nanoparticles and Applications in Nanomedicine

Abstract

The emerging field of nanomedicine provides new approaches for the diagnosis and treatment of diseases, for symptom relief and for monitoring of disease progression. One route of realizing this approach is through carefully constructed nanoparticles. Due to the small size inherent to the nanoparticles a proper characterization is not trivial. This review highlights the application of time-resolved fluorescence spectroscopy and fluorescence lifetime imaging microscopy (FLIM) for the analysis of nanoparticles, covering aspects ranging from molecular properties to particle detection in tissue samples. The latter technique is particularly important as FLIM allows for distinguishing of target molecules from the autofluorescent background and, due to the environmental sensitivity of the fluorescence lifetime, also offers insights into the local environment of the nanoparticle or its interactions with other biomolecules. Thus, these techniques offer highly suitable tools in the fields of particle development, such as organic chemistry, and in the fields of particle application, such as in experimental dermatology or pharmaceutical research.

Pitfalls in using fluorescence tagging of nanomaterials: tecto‐dendrimers in skin tissue as investigated by Cluster‐FLIM

“…Time‐resolved fluorescence measurements were conducted in a homemade FLIM setup . The setup consists of an inverted Microscope (IX71, Olympus, Shinjuku, Japan), a tunable ps‐supercontinuum laser (SuperK Extreme EUV3, NKT Photonics, Blokken, Denmark), a confocal scanning unit (DCS120, B&H, Berlin, Germany), a hybrid PMT detector (HPM‐100‐40, B&H) and TCPSC electronics (SPC150, B&H).…”

“…Time-resolved fluorescence measurements were conducted in a homemade FLIM setup. 28 The setup consists of an inverted Microscope (IX71, Olympus, Shinjuku, Japan), a tunable ps-supercontinuum laser (SuperK Extreme EUV3, NKT Photonics, Blokken, Denmark), a confocal scanning unit (DCS120, B&H, Berlin, Germany), a hybrid PMT detector (HPM-100-40, B&H) and TCPSC electronics (SPC150, B&H). The FLIM images were recorded using a 40× Objective (Olympus) resulting in a total field of view side length of 450 m. FITC and MG-FITC fluorescence was excited at 488 nm and Alexa Fluor 594 fluorescence at 561 nm using an acousto-optical tunable filter (SELECT UV-VIS, NKT Photonics) at 19.5 MHz.…”

Current State of Laser-Induced Fluorescence Spectroscopy for Designing Biochemical Sensors

“…Using the fluorescence lifetime difference exhibited by native doxorubicin (∼1 ns) compared to conjugated doxorubicin (∼4.6 ns), the intracellular release of conjugated doxorubicin was in situ monitored in H1299 lung cancer cells with time [197]. Environmental sensitivity of the fluorescence lifetime offers insights into the local environment of a nanoparticle or its interaction with surrounding biomolecules [198]. Titania (TiO 2 ) and zirconia (ZrO 2 ) serve as useful models for metal-oxide nanoparticles due to their identical stoichiometry, comparable acid/base behavior (surface hydroxyl groups' point of zero zeta potential = 5.8 and 6.7) and similar refractive indices (2.5 and 2.2, compared with 1.7 for alumina Al 2 O 3 ).…”

Heteroacene-Based Amphiphile as a Molecular Scaffold for Bioimaging Probes

“…Fluorescent lifetime (τ) expresses the time allocated by a fluorophore in the excited state before relaxing to the ground state. Additionally, fluorescence lifetime measurements are highly sensitive to the surrounding environment (Boreham et al, 2016). TRPZ-PG in THF shows a signal exponential component of 5.3 ns and TRPZ-bisMPA NPs exhibits a lifetime of 6.3 ns.…”