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Advances in Nanotheranostics with Plasmonic and Magnetic Nanoparticles
Published in Carla Vitorino, Andreia Jorge, Alberto Pais, Nanoparticles for Brain Drug Delivery, 2021
Sérgio R. S. Veloso, Paula M. T. Ferreira, J. A. Martins, Paulo J. G. Coutinho, Elisabete M. S. Castanheira
Moreover, the SPR is dependent on both particle size and environment (particularly on the dielectric constant), which can be explored in the development of sensors where the bonding of molecules or their proximity to the nanoparticle surface will modify the SPR frequency [37]. Apart from the environment, the plasmon band is sensible to the type of ligand (donor or withdrawing ligand), core charge, temperature, shape and aggregation, the latter inducing effects such as bathochromic shift and bandwidth widening owing to the interparticle plasmonic coupling [37]. The nanoparticles can also induce fluorescence quenching due to Förster resonance energy transfer or modulated photoinduced electron transfer [37]. Hereby, plasmonic nanoparticles, mainly the gold-based ones, have found application in different technological areas such as biosensors, clinic chemistry methods, immunologic assays, photothermolysis of tumour cells, detection and control of microorganisms, transport of drugs and monitorisation of biological cells [35, 39–41].
Molecular Imaging of Viable Cancer Cells
Published in Shoogo Ueno, Bioimaging, 2020
Another mechanism available for developing small-molecule-based probes is photoinduced electron transfer (PeT). PeT is an electron transfer from the PeT donor to the excited fluorophore, thereby diminishing the fluorescence of the fluorophore. The rate of PeT can be determined from the Marcus equation, and its major determinant ΔGPeT can be calculated from the Rehm–Weller equation: ΔGPeT = Eox – Ered - ΔE00 – wp, where Eox and Ered are the oxidation and reduction potentials of the electron donor and acceptor, ΔE00 is the singlet excited energy, and wp is the work term for the charge separation state.
Targeting macrophages: a novel avenue for cancer drug discovery
Published in Expert Opinion on Drug Discovery, 2020
Sahana Kumar, Anujan Ramesh, Ashish Kulkarni
Our increasing knowledge on the development of fluorescent probes and compounds which will emit fluorescence (ON/OFF states) only in the presence of activating signals has opened the gates to a wide variety of probes to visualize macrophages. Macrophages generate reactive oxygen and nitrogen species (ROS/RNS) in response to phagocytosis during inflammation. Hydrogen Peroxide (H2O2) is an important ROS generated in macrophages and fluorophores having H2O2-reactive groups at specific positions such that fluorescence is only elicited upon cleavage with H2O2 [118–120]. Macrophages during inflammation also produce nitric oxide synthase which produced nitric oxide (NO). Smart fluorophores that image NO in macrophages have been developed and shown promise. Nagano and colleagues described a fluorophore which is regulated by donor-excited photoinduced electron transfer (d-PeT). Their method depends upon the formation of N2O3 from NO which reacts with o-diamine which is an intramolecular PeT quencher and thereby produces fluorescent triazoles [121]. Lin et al. synthesized a small molecule, a coumarin-rhodamine hybrid, capable of ratiometric fluorescent imaging of endogenous NO produced inside macrophages [122]. Other probes sensitive to Hypochlorous acid (HOCl) and superoxide (O2˙−) have been successfully developed for in vitro and in vivo imaging of macrophage activity [123–126]. The characteristic feature of macrophages is its ability to perform phagocytosis. Vazquez-Romero et al. developed a smart synthetic fluorophore via multicomponent reactions to image phagocytic activity of macrophages. The low-pH sensing fluorescent probe containing PhagoGreen helped in imaging the acidification of the phagosome in macrophages [127]. Macrophages are also key players in wound healing and tissue modeling and studies targeting Matrix metalloproteinases (MMPs) and cathepsins have been studied for macrophage imaging. Lohela et al. used a commercial probe MMPSense 680 to monitor the TAMs in 4T1 breast cancer models real time [128]. Smart activity-based probes (APBs) that emit fluorescence only after they are recognized by active cathepsins have been used to image TAMs [129,130]. Table 2 summarizes the fluorescent-based diagnostic platforms involved in macrophage imaging.