#Viscosity chemistry series#

From a practical point of view, FMR with high extinction coefficients, long (NIR) excitation wavelength, and potentially high brightness would be desirable ( Ning et al., 2017 Hou et al., 2018).

Recently, FMRs have been widely used to measure viscosity of local environment using their changes in fluorescence intensity and lifetime ( Kuimova, 2012). Therefore, the physical mechanism of viscosity dependence of fluorescence quantum yield and lifetime is caused by the steric hindrance of intramolecular rotation. However, in a high viscosity medium, rotation through the C-C bond is constrained, and the excitation energy is released as emission with enhanced fluorescence intensity and lifetime ( Uzhinov et al., 2011 Lee et al., 2018). In a low viscosity medium, the rotor rotates freely, and the energy of excitation is dissipated with non-radiative energy. One moiety with a large moment of inertia is considered to be fixed, called the stator, and the other moiety with a smaller moment of inertia is called the rotor ( Figure 1A). A common feature of FMR is that it consists of two moieties, which are connected by a single bond.

Fluorescent molecular rotors (FMRs) are established as tools for monitoring cellular and subcellular viscosity changes because of their high sensitivity, fast-response and non-invasive testing of targets in biological systems. Thus, the development of suitable imaging tools to monitor and detect cellular microviscosity is important to study cellular function in both health and disease.

#Viscosity chemistry series#

Abnormal changes of intracellular microviscosity are associated with a series of pathologies and diseases ( Nadiv et al., 1994). The viscosity of cells is an important parameter of the cellular microenvironment, which influences the interaction and transport of biological molecules and signals in living cells ( Minton, 2001).