Optical fiber-based fluorescent viscosity sensor

Abstract

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Molecular rotors as luminescence sensors of local viscosity and viscous flow in solutions and organized systems

“…However, a Attempts were made to immobilize molecular rotors on a solid surface. 50 Initially, this was done using the surface of optical fibre. The surface grafting was performed by covalent bonding via silane derivatives: 3-aminopropyltrimethoxysilane, N-(6-aminohexyl)aminopropyltrimethoxysilane, ureidopropyltrimethoxysilane.…”

A “Distorted‐BODIPY”‐Based Fluorescent Probe for Imaging of Cellular Viscosity in Live Cells

“…4, 5 Recently, significant efforts have been devoted to the development of different kinds of FMRs. However, typical molecular rotors, which are a special subgroup of twisted intramolecular charge transfer (TICT) fluorophores, are more or less sensitive to the solvent polarity;4b, 5a–h porphyrin‐based rotors are synthetically demanding and offer low sensitivity (the fluorescence quantum yield of porphyrins is less than 0.1) 1a. 4a In our previous work, we proved that the rotation of a CHO group at a meso ‐position of a pentamethine cyanine dye is highly sensitive to viscosity 5i.…”

Porphyrin‐Based Molecular Rotors as Fluorescent Probes of Nanoscale Environments

“…[2,17] Fluorescent molecular rotors (FMRs) describe a subset of molecular rotors in which some degree of internal rotation can occur within the excited-state lifetime of the species, to open or close an efficient nonradiative relaxation pathway. [18] The fluorescence quantum yield of an FMR is thus strongly dependent on any factor affecting the rate of internal rotation, that is, viscosity, local sheer stress or flow field, temperature, and membrane fluidity. FMRs are of wide interest as sensors for fluid dynamics in microenvironments in which mechanical viscometry is not practical.…”

“…They find application in the measurement of bioviscosity, liposome formation and lipid bilayer packing in vitro, in the food industry (e.g., gelation), and in mechanistic studies pertaining to polymerization and liquid crystallinity either in solution or as entities on solid supports such as glass, polymers, or optical fibers. [18][19][20][21][22][23] The most commonly studied FMRs to date are the cyanovinyl-substituted julolidines and dimethylaminobenzenes in which a twisted intramolecular charge transfer can occur between an arylamine donor and a cyano acceptor. [11,18,19,21] We are interested in developing supramolecular, porphyrin-based FMRs in which porphyrin fluorescence is modulated by electron transfer (ET) interactions with an attached ligand, and in which the efficiency of that ET is dependent upon the conformational dynamics of the ligand (Fig.…”