Dye-Loaded Quatsomes Exhibiting FRET as Nanoprobes for Bioimaging

Fluorescent organic nanoparticles (FONs) are emerging as an attractive alternative to the well-established fluorescent inorganic nanoparticles or small organic dyes. Their proper design allows one to obtain biocompatible probes with superior brightness and high photostability, although usually affected by low colloidal stability. Herein, we present a type of FONs with outstanding photophysical and physicochemical properties in-line with the stringent requirements for biomedical applications. These FONs are based on quatsome (QS) nanovesicles containing a pair of fluorescent carbocyanine molecules that give rise to Förster resonance energy transfer (FRET). Structural homogeneity, high brightness, photostability, and high FRET efficiency make these FONs a promising class of optical bioprobes. Loaded QSs have been used for in vitro bioimaging, demonstrating the nanovesicle membrane integrity after cell internalization, and the possibility to monitor the intracellular vesicle fate. Taken together, the proposed QSs loaded with a FRET pair constitute a promising platform for bioimaging and theranostics

Linear Photophysics, Two-Photon Absorption And Femtosecond Transient Absorption Spectroscopy Of Styryl Dye Bases

The steady-state and time-resolved linear spectral properties, two-photon absorption spectra and fast relaxation processes in the excited states of styryl base-type derivatives were investigated. The nature of linear absorption, fluorescence and excitation anisotropy spectra were analyzed in solvents of different polarity at room temperature and specific dependence of the solvatochromic behavior on the donor-acceptor strength of the terminal substituents was shown. Two-photon absorption (2PA) efficiency of styryl dye bases was determined in a broad spectral range using two-photon induced fluorescence technique, and cross-sections maxima of ~ 100 GM were found. The excited state absorption (ESA) and fast relaxation processes in the molecular structures were investigated by transient absorption femtosecond pump-probe methodology. The role of twisted intramolecular charge transfer (TICT) effect in the excited state of styryl dye base with dimethylamino substituent was shown. The experimental spectroscopic data were also verified by quantum chemical calculations at the Time Dependent Density Functional Theory level, combined with a polarizable continuum model

Ultrafast Spectroscopy, Superluminescence And Theoretical Modeling Of A Two-Photon Absorbing Fluorene Derivative

A comprehensive study of photophysical and photochemical properties of an unsymmetrical fluorene derivative is presented, including linear absorption, fluorescence excitation anisotropy, photochemical stability, steady-state fluorescence, and fluorescence lifetimes in organic solvents of different polarities. Nonlinear optical properties were investigated using Z-scan measurements of degenerate two-photon absorption and femtosecond pump-probe spectroscopy. The strongly fluorescent compound exhibited good photostability, positioning it for use in a number of applications. A dramatic increase in fluorescence intensity along with spectral narrowing was observed under femtosecond pumping, demonstrating amplified spontaneous emission. An extensive set of experimental data is rationalized based on essential state models

Ultrafast spectroscopy, superluminescence and theoretical modeling of a two-photon absorbing fluorene derivative

A comprehensive study of photophysical and photochemical properties of an unsymmetrical fluorene derivative is presented, including linear absorption, fluorescence excitation anisotropy, photochemical stability, steady-state fluorescence, and fluorescence lifetimes in organic solvents of different polarities. Nonlinear optical properties were investigated using Z-scan measurements of degenerate two-photon absorption and femtosecond pump-probe spectroscopy. The strongly fluorescent compound exhibited good photostability, positioning it for use in a number of applications. A dramatic increase in fluorescence intensity along with spectral narrowing was observed under femtosecond pumping, demonstrating amplified spontaneous emission. An extensive set of experimental data is rationalized based on essential state models