FRET Phenomenon in Photoreversible Dual-Color Fluorescent Polymeric Nanoparticles Based on Azocarbazole/Spiropyran Derivatives

Abstract

Incorporation of chromophores into a polymer chain results in prominent photoreversibility and fatigue resistance, photostability over the long term, and restriction of the internal conversion (IC). Here, we report the copolymerization of two photoactive monomers with methyl methacrylate via emulsion polymerization in order to obtain photoswitchable dual-color fluorescent nanoparticles. For this purpose, azocarbazole ethyl acrylate (AzoCzEA) and spiropyran ethyl acrylate (SPEA) were synthesized and the fluorescence polymeric latex nanoparticles were prepared correspondingly. FT-IR and 1 HNMR spectra were used to confirm the structure of novel fluorescent AzoCzEA. UV−vis studies of the obtained nanoparticles displayed the spectral features of both AzoCzEA and SPEA under stimuli-irradiation and inclusion of these chromophores into the polymer particles. DSC analysis revealed an increase in T g of the prepared copolymer, indicating covalently incorporation of the photoactive monomers into the polymer chains. The optimum ratio of two chromophores to achieve complete quenching and highest energy transfer was determined by UV−vis spectroscopy. DLS and SEM results demonstrated particle size distribution of 40−80 nm with spherical morphology. Fluorescence spectra revealed remarkable fluorescence resonance energy transfer (FRET) from AzoCzEA to SPEA after UV irradiation at 365 nm and dual-color characteristic of the prepared nanoparticles. Besides, an enhancement in the photoreversibility, photostability, prevention of IC, dye leakage, and aggregation were studied elaborately. The obtained results were attributed to the involvement of such chromophores into the polymeric matrix via covalent bonding. Labeling and tracking of living cells and rewriteable patterning are potential applications for such dual-color fluorescent nanoparticles.

Chromophoric Dendrimer-Based Materials: An Overview of Holistic-Integrated Molecular Systems for Fluorescence Resonance Energy Transfer (FRET) Phenomenon

“…Thus, this phenomenon is highly sensitive to the spatial dimensions and specific orientation and the chemical nature of the environment surrounding the chromophore units. Thereby, FRET can be used as a reliable technique to characterize the dynamics, e.g.,the conformational changes of macromolecules, helping to establish the nature of intermolecular interactions in natural (e.g.,biological molecules) and artificial (e.g., micelles, dendrimers) nanosized systems having chromophores groups [78,[95][96][97]. A more detailed theoretical description of this mechanism consists of a donor entity reaching an excited state due to interaction with a photon.…”

Spiropyran-Based Drug Delivery Systems

“…As a result of the differences between the SP and MC forms, and the ability to switch between them repeatedly by application of an external stimulus, SP molecules have received widespread attention for their use in many various dynamic systems, including SP-functionalised polymers, biopolymers, inorganic nanoparticles, carbon nanomaterials and solid surfaces—many of which have potential biological applications ( Klajn, 2014 ; Cardano et al, 2019 ); notably, in cell tracking and labelling ( Keyvan Rad et al, 2015 ; Keyvan Rad et al, 2016 ; Cong et al, 2021 ), photothermal therapy ( Keyvan Rad et al, 2018 ) and cell sheet engineering ( Karimipour et al, 2021 ). These applications, however, may be restricted by the well-known tendency of the MC isomer to undergo hydrolytic decomposition in aqueous solution, resulting in the formation of salicylaldehyde and a Fischer’s base derivative ( Stafforst and Hilvert, 2008 ; Hammarson et al, 2013 ).…”

Rewritable Anticounterfeiting Polymer Inks Based on Functionalized Stimuli-Responsive Latex Particles Containing Spiropyran Photoswitches: Reversible Photopatterning and Security Marking

“…Such characteristics of spiropyran are significantly influenced by its interaction with the surrounding media, especially hydrogen boding and polar–polar interactions. ,, Therefore, protection of spiropyran from environmental degradations of such strong interactions is an important requirement for development of stimuli-chromic polymers. Chemical incorporation of spiropyran into the hydrophobic or less-polar polymer matrices such as polystyrene (PS) or poly­(methylmethacrylate) (PMMA) improves the efficiency of its stimuli-chromic properties, for instance, photostability, reversibility, and also sensitivity. ,,− On the other side, chemical attachment of the photochromic polymers to different matrices can result in decrease of environmental degradation effects. This is carried out by functionalization of the photochromic polymers by using functional monomers such as glycidyl methacrylate (GMA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA).…”

“…Also, spiroxazine-containing PS and CNC were incorporated on cellulose fibers by the weak physical interactions. Mahdavian’s group developed functionalized and nonfunctionalized polymer nanoparticles with different characteristics. ,,,, For instance, epoxy-functionalized photochromic polymer nanoparticles were prepared by using of acrylated spiropyran as a comonomer in the semicontinuous emulsion copolymerization of methyl methacrylate (MMA) and GMA . Because of the presence of epoxy functional groups at the surface of particles, the latex particles are capable of chemical attachment to different substrates by the ring-opening reaction of epoxy functionalities with appropriate nucleophiles.…”