Triplet–Triplet Annihilation Upconversion by Polymeric Sensitizers

Keshav Kumar JhaAmrutha Prabhakaran, Christopher S. Burke, Marcus Schulze, Ulrich S. Schubert, Tia E. Keyes, Michael Jäger, and Benjamin Dietzek Ivanšić

Journal of Physical Chemistry C 2022

https://doi.org/10.1021/acs.jpcc.1c09897

This contribution studies the effect of integrating Ru(dqp)2-inspired molecular sensitizers into the side chains of a PMMA polymer, which─as a macromolecular photosensitizer─is codissolved with 9,10-diphenylanthracene as an annihilator. We study the effect of confining the sensitizers into a comparably small volume on the triplet–triplet annihilation upconversion (TTAUC) process and compare the results to those of an upconversion system using various concentrations of a monomeric annihilator. We show that our approach of using a macromolecular photosensitizer allows for upconversion at extremely low excitation power densities. Furthermore, the onset of a strong annihilation regime, that is, a regime in which the intensity of the upconverted light scales linearly with the increase of the excitation power, is significantly reduced using the polymeric sensitizer; however, the upconversion intensity sits below those of the monomeric counterparts.





Shorter Alkyl Chains Enhance Molecular Diffusion and Electron Transfer Kinetics between Photosensitisers and Catalysts in CO2-Reducing Photocatalytic Liposomes

David M. Klein, Dr. Santiago Rodríguez-Jiménez, Marlene E. Hoefnagel, Dr. Andrea Pannwitz, Amrutha Prabhakaran, Dr. Maxime A. Siegler, Prof. Tia E. Keyes, Prof. Erwin Reisner, Prof. Albert M. Brouwer, Prof. Sylvestre Bonnet

Chemistry – A European Journal 2021

https://doi.org/10.1002/chem.202102989

A series of Ru photosensitisers (RuCn) and Re catalysts (ReCn) covalently functionalised with alkyl chains of different lengths (n=9, 12, 15, 17, and 19) were immobilised on liposomes to perform photocatalytic CO2 reduction using ascorbate (HAsc) as electron donor. A higher turnover number for CO production (TONCO) was found for systems with shorter alkyl tails, which was due to the higher mobility of the molecules on the lipid bilayer, leading to faster electron transfer between RuCn and ReCn.





Radiative lifetime of a BODIPY dye as calculated by TDDFT and EOM-CCSD methods: solvent and vibronic effects

Rengel Cane E. Sia, Ruben Arturo Arellano-Reyes, Tia E. Keyes and Julien Guthmuller

Physical Chemistry Chemical Physics 2021

https://doi.org/10.1039/D1CP03775G

The radiative emission lifetime and associated S1 excited state properties of a BODIPY dye are investigated with TDDFT and EOM-CCSD calculations. The effects of a solvent are described with the polarizable continuum model using the linear response (LR) approach as well as state-specific methods. The Franck–Condon (FC), Herzberg–Teller (HT) and Duschinsky vibronic effects are evaluated for the absorption and emission spectra, and for the radiative lifetime. The transition energies, spectra shapes and radiative lifetime are assessed with respect to experimental results. It is found that the TDDFT transition energies are overestimated by about 0.4–0.5 eV, whereas EOM-CCSD improves the vertical emission energy by about 0.1 eV in comparison to TDDFT. The solvatochromic and Stokes shifts are better reproduced by the state-specific solvation methods, which show that these methods are more suited than the LR model to describe the solvent effects on the BODIPY dye. The vibronic effects lead to an increase of the radiative lifetime of about 0.4 to 1.0 ns depending on the theoretical approach, which highlights the importance of such effects. Moreover, the HT effects are negligible on both the spectra and lifetime, which demonstrates that the FC approximation is accurate for the BODIPY dye. Finally, the comparison with experimental data shows that the radiative lifetimes predicted by EOM-CCSD and TDDFT have comparable accuracy.





Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

Maximilian L. Hupfer, Beata Koszarna, Soumik Ghosh, Daniel T. Gryko, and Martin Presselt

Langmuir 2021

https://doi.org/10.1021/acs.langmuir.1c01113

In this work, we present the formation of H- and J-aggregates of amphiphilic centrosymmetric diketopyrrolopyrroles containing aliphatic or aromatic amino groups. The inherent amphiphilicity of these dyes predestines their assembly at interfaces to form ordered supramolecular structures. We employed the Langmuir–Blodgett (LB) technique to generate, manipulate, and deposit such supramolecular structures. The aforementioned amines provide an additional means to control the formation of the supramolecular assemblies. In the resulting LB films, both H- and J-aggregates of the dyes can be realized, leading to very broad absorption spectra. In contrast to many reports on H- and J-aggregates, the interactions between the symmetric diketopyrrolopyrroles are controlled via interface assembly and π-stacking and not by dipolar interactions.





Monitoring excited-state relaxation in a molecular marker in live cells–a case study on astaxanthin

Tingxiang Yang,  Avinash Chettri,  Basseem Radwan,  Ewelina Matuszyk, Malgorzata Baranska  and Benjamin Dietzek

Chemical Communications 2021

https://doi.org/10.1039/D1CC01907D

Small molecules are frequently used as dyes, labels and markers to visualize and probe biophysical processes within cells. However, very little is generally known about the light-driven excited-state reactivity of such systems when placed in cells. Here an experimental approach to study ps time-resolved excited state dynamics of a benchmark molecular marker, astaxanthin (AXT), in live human cells is introduced. The photoinduced dynamics in AXT recorded in cellulo appears to be unchanged compared to the dynamics recorded in solution. Aside from indicating the absence of AXT aggregation in the cells, this points to the fact that structural distortion of the AXT molecules, which has been suggested based on shifts of the resonance Raman active C=C vibration, do not alter the transient absorption data recorded during the in cellulo experiments. Finally, in a methodological context we show that our approach to in cellulo transient absorption spectroscopy offers a valuable path to study the impact of local environments on the photoinduced dynamics in stains, markers and beyond this in light-activated drugs, e.g. for photodynamic therapy, and interactions between phototherapy agents and live cells





Toward Raman Subcellular Imaging of Endothelial Dysfunction

Adriana Adamczyk, Ewelina Matuszyk, Basseem Radwan, Stefano Rocchetti, Stefan Chlopicki, and Malgorzata Baranska

Journal of Medicinal Chemistry 2021

https://doi.org/10.1021/acs.jmedchem.1c00051

Multiple diseases are at some point associated with altered endothelial function, and endothelial dysfunction (ED) contributes to their pathophysiology. Biochemical changes of the dysfunctional endothelium are linked to various cellular organelles, including the mitochondria, endoplasmic reticulum, and nucleus, so organelle-specific insight is needed for better understanding of endothelial pathobiology. Raman imaging, which combines chemical specificity with microscopic resolution, has proved to be useful in detecting biochemical changes in ED at the cellular level. However, the detection of spectroscopic markers associated with specific cell organelles, while desirable, cannot easily be achieved by Raman imaging without labeling. This critical review summarizes the current advances in Raman-based analysis of ED, with a focus on a new approach involving molecular Raman reporters that could facilitate the study of biochemical changes in cellular organelles. Finally, imaging techniques based on both conventional spontaneous Raman scattering and the emerging technique of stimulated Raman scattering are discussed.


Multiplex Raman imaging of organelles in endothelial cells

Ewelina Matuszy, Adriana Adamczyk, Basseem Radwan, Anna Pieczara, Piotr Szcześniak, Jacek Mlynarski, Katarzyna Kamińska, Malgorzata Baranska 

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2021

https://doi.org/10.1007/s00018-020-03718-1

The aim of this work is to visualize the main cell organelles in endothelial cells (HMEC-1) using established reporters (EdU and MitoBADY), but also to test a new Raman reporter, namely falcarinol, which exhibits lipophilic properties. Moreover, we tested the possibility to use Raman reporters as a probe to detect changes in distribution of certain organelles after induced endothelial dysfunction (ED) in in vitro models. In both cases, induced ED is characterized by the formation of lipid droplets in the cells, which is why a good tool for the detection of lipid-rich organelles is so important in these studies.





Astaxanthin as a new Raman probe for biosensing of specific subcellular lipidic structures: can we detect lipids in cells under resonance conditions?

Krzysztof Czamara, Adriana Adamczyk, Marta Stojak, Basseem Radwan, Malgorzata Baranska 

Cellular and Molecular Life Sciences 2020

https://doi.org/10.1007/s00018-020-03718-1

Here we report a new Raman probe for cellular studies on lipids detection and distribution. It is (3S, 3’S)-astaxanthin (AXT), a natural xanthophyll of hydrophobic properties and high solubility in lipids. We showed that AXT accumulates in lipidic structures of endothelial cells in time-dependent manner that provides possibility to visualize e.g. endoplasmic reticulum, as well as nuclear envelope. As a non-toxic reporter, it has a potential in the future studies on e.g. nucleus membranes damage in live cells in a very short measuring time.


Labeled vs. Label-Free Raman Imaging of Lipids in Endothelial Cells of Various Origins

Basseem Radwan, Adriana Adamczyk, Szymon Tott, Krzysztof Czamara, Katarzyna Kaminska, Ewelina Matuszyk, Malgorzata Baranska

Molecules 2020

https://doi.org/10.3390/molecules25235752

Endothelial dysfunction has been recognized as a primary or secondary cause of many diseases and it manifests itself, among others, by increased lipid content or a change in the lipid composition in the EC. Therefore, the analysis of cellular lipids is crucial to understand the mechanisms of disease development. Tumor necrosis factor alpha (TNF-α)-induced inflammation of EC alters the lipid content of cells, which can be detected by Raman spectroscopy. We consider (3S,3′S)-astaxanthin (AXT), a natural dye with a characteristic resonance spectrum, as a new Raman probe for the detection of lipids in the EC of various vascular beds, i.e., the aorta, brain and heart. AXT colocalizes with lipids in cells, enabling imaging of lipid-rich cellular components in a time-dependent manner using laser power 10 times lower than that commonly used to measure biological samples.


Interaction of Miltefosine with Microcavity Supported Lipid Membrane: Biophysical Insights from Electrochemical Impedance Spectroscopy

Nirod Kumar Sarangi, Amrutha Prabhakaran, Tia E. Keyes

Electroanalysis 2020

https://doi.org/10.1002/elan.202060424

Miltefosine an alkylphosphocholine analogue, is the only drug taken orally for the treatment of leishmaniasis‐a parasitic disease caused by sandflies. Although it is believed that Miltefosine exerts its activity by acting at the lipid membrane, detailed understanding of the interaction of this drug with eukaryotic membranes is still lacking. Herein, we exploit microcavity pore suspended lipid bilayers (MSLBs) as a biomimetic platform in combination with a highly sensitive label‐free electrochemical impedance spectroscopy (EIS) technique to gain biophysical insight into the interaction of Miltefosine with host cell membrane as a function of lipid membranes composition.