Investigation of cyanine dyes for in vivo optical imaging of altered mitochondrial membrane potential in tumors

Abstract

Mitochondrial membrane potential (Δψm) alteration is an important target for cancer diagnosis. In this study, we designed a series of near-infrared fluorescent cationic cyanine dyes with varying alkyl chain lengths (IC7-1 derivatives) to provide diverse lipophilicities and serum albumin-binding rates, and we evaluated the usefulness of these derivatives for in vivo Δψm imaging. IC7-1 derivatives with side chains from methyl to hexyl (IC7-1-Me to IC7-1-He) were synthesized, and their optical properties were measured. Cellular uptake and intracellular distribution were investigated with depolarized HeLa cells from carbonyl cyanine m-chlorophenylhydrazone (CCCP) treatment using a spectrofluorometer and a fluorescence microscope. Serum albumin-binding rates were evaluated using albumin-binding inhibitors. In vivo optical imaging was performed with HeLa cell xenograft mice following intravenous administration of IC7-1 derivatives with or without warfarin and CCCP as in vivo blocking agents. IC7-1 derivatives showing maximum excitation and emission wavelengths at 823 nm and ∼845 nm, respectively, were synthesized. IC7-1-Me to -Bu showed fluorescence in mitochondria that decreased with CCCP treatment in a concentration-dependent manner, which showed that IC7-1-Me to -Bu successfully indicated Δψm. Tumors were clearly visualized after IC7-1-Bu administration. Treatment with warfarin or CCCP significantly decreased IC7-1-Bu fluorescence in the tumor region. In summary, IC7-1-Bu exhibited fluorescence localized to mitochondria dependent on Δψm, which enabled clear in vivo tumor imaging via serum albumin as a drug carrier for effective tumor targeting. Our data suggest that IC7-1-Bu is a promising NIR probe for in vivo imaging of the altered Δψm of tumor cells.

Discerning the Chemistry in Individual Organelles with Small‐Molecule Fluorescent Probes

“…[39] Therefore,c ations with strong lipophilicity tend to move across the phospholipid bilayer of the inner membrane and accumulate inside the mitochondrial matrix at ar atio of more than 10:1 compared to other organelles,d riven by the potential gradient of the membrane. [31,41] Such fluorophores have been optimized and commercialized to adapt to chemical biology studies.F or example,t he MitoTracker series (1 and 2,S cheme 1A), [42] which possess overall positive charge across the lipophilic scaffolds,c an be easily taken up by the mitochondria of live cells.They possess ab road range of options regarding emission wavelength, while showing minimum staining of other organelles. [31,41] Such fluorophores have been optimized and commercialized to adapt to chemical biology studies.F or example,t he MitoTracker series (1 and 2,S cheme 1A), [42] which possess overall positive charge across the lipophilic scaffolds,c an be easily taken up by the mitochondria of live cells.They possess ab road range of options regarding emission wavelength, while showing minimum staining of other organelles.…”

Mitochondria-Targeted Triphenylphosphonium-Based Compounds: Syntheses, Mechanisms of Action, and Therapeutic and Diagnostic Applications

“…65–71 Rhodamine- and cyanine-based cationic fluorophores have been extensively used as research tools as mitochondrial stains and for monitoring mitochondrial membrane potential, as discussed below, based on the extent of their total cellular uptake or the ratio of mitochondrial to cytosolic concentration of the cationic probe. 72–81 Small molecule heterocyclic cations were also used as vehicles to deliver other compounds to mitochondria. 82–92 The heterocyclic cations have been conjugated with quinone, spin traps, or thiol-reactive moieties to specifically localize those compounds in cell mitochondria.…”

Squaraine Dyes: Interaction with Bovine Serum Albumin to Investigate Supramolecular Adducts with Aggregation‐Induced Emission (AIE) Properties

“…Moreover, it has been reported that drugs with preferential affinity towards binding site II show efficient photodynamic therapeutic applications . In order to use albumin as a tumor targeting carrier, a moderate binding between the protein and the drug is required . Then, along with the potency of drug‐target binding interactions measured by the K d , binding kinetics is undoubtedly an essential issue in drug discovery.…”

“…[2] In order to use albumin as at umor targeting carrier, am oderate binding between the protein and the drug is required. [3] Then, along with the potencyo fd rug-target binding interactions measured by the K d ,b inding kinetics is undoubtedly an essential issue in drug discovery.B oth residence time and association rate constant are important parameters for in vivo efficacy and safety of drugss ince they can help in understanding their mechanismso fa ction and structure-activity relationships. [4] Ag reat number of studies involving protein-dye interactions have been published so far [5] since the interesti nd eveloping new probes that can noncovalently bind proteins for their detection and sensingi sc onstantly growing.…”