Ultrafast in cellulo photoinduced dynamics processes of the paradigm molecular light switch [Ru(bpy)2dppz]2+

Abstract

An in cellulo study of the ultrafast excited state processes in the paradigm molecular light switch [Ru(bpy)2dppz]2+ by localized pump-probe spectroscopy is reported for the first time. The localization of [Ru(bpy)2dppz]2+ in HepG2 cells is verified by emission microscopy and the characteristic photoinduced picosecond dynamics of the molecular light switch is observed in cellulo. The observation of the typical phosphorescence stemming from a 3MLCT state suggests that the [Ru(bpy)2dppz]2+ complex intercalates with the DNA in the nucleus. The results presented for this benchmark coordination compound reveal the necessity to study the photoinduced processes in coordination compounds for intracellular use, e.g. as sensors or as photodrugs, in the actual biological target environment in order to derive a detailed molecular mechanistic understanding of the excited-state properties of the systems in the actual biological target environment.

The development of ruthenium(ii) polypyridyl complexes and conjugates forin vitrocellular andin vivoapplications

“…Similarly, transient absorption signals (λpump = 430 nm and λprobe = 580 nm) from the complex were only detected from the nuclei of treated cells, with no signals originating from the cytoplasm, as shown in Fig 31b-d. 302 This work demonstrated for the first time that ultrafast photo-induced processes occurring in Ru(II) complexes can be investigated within cells. Moreover, such studies may enable researchers to gain a more detailed understanding of the interplay between the ultrafast dynamics within these complexes and their biological activities.…”

“…300,301 In an effort to enhance our understanding of the processes occurring within the excited states of Ru(II) complexes when internalised by cells, transient absorption microscopy. 302 Confocal microscopy studies showed the emission from the complex to originate from the nuclei of the fixed cells, as shown in Fig. 31a.…”

Photochemically active DNA-intercalating ruthenium and related complexes – insights by combining crystallography and transient spectroscopy

“…Laser transient spectroscopic absorption spectroscopic methods should be valuable in determining the photoprocesses which proceed in a biological cell and indeed a very recent report by Dietsek's group has just been carried out with [Ru(bpy) 2 dppz] 2+ in HepG2 cells. 75 Such studies will provide fundamental information to guide the studies of the rapidly emerging study of ruthenium polypyridyl complexes in biological cells, which should have potential applications such as imaging or photodynamic therapy. 76 …”

Making the Right Link to Theranostics: The Photophysical and Biological Properties of Dinuclear RuII–ReI dppz Complexes Depend on Their Tether

“…23,25,44,46 The resultant spectra are dominated by a broad short-lived transient absorption, in the range 500 -700 nm, which is consistent with the population of a metal®dppz(p*) 3 MLCT state. 54 The bands at ~470 nm and ~600 nm, indicative of dppz-radical anion coordinated to a metal center, are also present; 55 an absorbance at 475 nm has also been reported for a dppz-localised excited state. 56 In the absence of DNA, the transient spectra decay almost to the baseline within several nanoseconds, with the somewhat faster decay occurring for 2 3+ (t = 160 ps) than 1 3+ (t = 210 ps).…”