Research
Our group is interested in the design, synthesis and application of novel luminescent materials. Especially the influence of aggregation on the photophysical properties drives our research. In this context we are investigating three independent phenomena, namely AIE (aggregation-induced emission), ACQ (aggregation-caused quenching) and SSSE (solution and solid state emission). We believe that each of these effects has its applications and we are aiming to find corresponding ones.
Lately we were able to synthesize a library of aromatic thioethers that are able to show aggregation-induced emission properties, whose emission can easily be tuned by numerous structural variations such as substitution pattern, functional groups, number of rotors or chalcogen variation.[1] Bridging these ethers led to emitters in solution and the solid state.[2] Besides fluorescence emission we are especially interested in phosphorescence which was obtained using substituted dibenzofurans.[3]
These compounds were fabricated to be used as core structures in luminescent hydro- and organogels.[4] These unique compounds exhibit pH sensitivity and can be selectively switched from sol to gel.
Future perspectives involve the application of our novel luminophores in emissive polymers, sensors as well solar cell concentrators and OLEDs.
[1] A) Chem. Eur. J., 2017, 23, 13660–13668, B) Chem. Select, 2018, 3, 985–991, C) ChemPhotoChem, 2020, 4, 1–10.
[2] Chem. Asian J., 2021, 16, 2307–2313.
[3] Angew. Chem. Int. Ed., 2022, 61, e202111805.
[4] A) Soft Matter, 2019, 15, 7117–7121, B) Soft Matter, 2018, 14, 6166–6170.
The luminophores designed in our group find application in numerous systems – especially for imaging and tracking purposes in biomedical samples. Here we aim to track transfection processes – the transport of genetic material into a cell – using tailor made transfection vectors with luminescence properties.
Here hybrid compounds were successfully used to follow the cellular uptake into a cell followed by transfection of HeLa cells, which was tracked by expression of a red fluorescent protein.[1] Besides that, specific recognition of proteins within the framework of the CRC 1093 (Supramolecular Chemistry on Proteins) plays a pivotal role in our group. Here we already facilitated already the recognition of small cationic or anionic compounds using aggregation-induced emission.[2] Furthermore ultrasmall gold or calciumphosphate nanoparticles were successfully equipped and used as versatile shuttle to transport luminophores into cells.[3] Our ultimate goal is the modulation or inhibition of specific cancer relevant proteins, including a readout of these processes using an emission “on” signal based on aggregation-induced emission.
[1] A) RSC Adv., 2020, 10, 19643–19647, B) ChemBioChem, 2021, 22, 1563–1567.
[2] A) Isr. J. Chem., 2018, 58, 927–931, B) Chem. Commun. 2021, 57, 3091–3094.
[3] A) ChemNanoMat, 2019, 5, 436–446, B) Molecules 2022, 27, 1788.
The treatment of cancer or infections with multi-resistant bacteria remains one of the most challenging disciplines in modern biomedical chemistry. Here the so-called photodynamic therapy (PDT) is one of the possible methods to address these issues.[1] Photosensitizers such as porphyrins, phthalocyanines and subphthalocyanines are able to generate reactive oxygen species that are able to harm specific biological targets, when irradiated with long-waved light. In this regard we aim to overcome classic drawbacks of PDT such as low water solubility and aggregation effects.
To this end we follow two approaches: A) inducing a steric separation of the single photosensitizers by using supramolecular host guest complexation and B) using charged photosensitizers leading to an electrostatic repulsion.
Lately we were able to use 1:1 complexes between substituted subphtalocyanines and β-cyclodextrin, which were used to efficiently penetrate HeLa cells and hence revealed striking phototoxicity upon irradiation with red light.[2] An improved version containing up to eight positive charges was also able to kill gram positive and gram negative bacteria.[3]
Future optimisations will involve the specific targeting of biomedical targets using a supramolecular approach.
[1] Int. J. Pharm., 2020, 586, 119595.
[2] Chem. Commun., 2020, 56, 7653–7656.
[3] Chem. Eur. J., 2021, 27, 14672–14680.