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Ji-Hyung Choi

Luminescent Lanthanide-based bioprobes for zinc(II) detection for cellular imaging

Published on 11 February 2022
Thesis presented February 11, 2022

Abstract:
Deducing molecular mechanisms of biological functions in living cells requires non-invasive analytical tools that can monitor cell dynamics with high spatial and temporal resolution. In our laboratory, we aim to develop detection tools of various biomolécules such as copper(II), zinc(II) and DNA. Our bioprobes have a peptidic backbone that can recognize the target molecule with high specificity and have a lanthanide luminescent complexes suited for targeted biological imaging.
Lanthanides’ unique photophysical properties make them advantageous for biological imaging by allowing time-gated luminescence microscopy at millisecond-long scale . Time-gated microscopy overcomes common problems due to background noise from the short-lifetime autofluorescence of biological samples. In cellular imaging, the auto-fluorescence can be minimized by choosing the excitation and emission wavelength in the diagnostic window which starts from 650nm to 1300 nm.
Here, we present our strategy to develop a responsive bioprobe for zinc(II) in living cells by luminescence lifetime modulation based on energy exchange between the lanthanide complex and an aromatic compound taking the role of a quencher of luminescence.
To convert Lanthanide luminescent complexes into zinc(II) bioprobes, they have been conjugated to a peptidic sequence mimicking zinc fingers to offer high selectivity for zinc(II) with an affinity matching the physiological concentration. The zinc finger folds into a rigid structure when coordinating a zinc ion containing two beta sheets and one alpha helix. The conformational change will modulate the distance between the lanthanide complex and the quencher and thus, it will modulate the luminescence response. In particular, we focus on lifetime response.
Moreover, we design our lanthanide complexes to be compatible with two-photon (2P) absorption in order to get the excitation wavelength in the diagnostic window and reduce photo-damage to cells due to light excitation We will describe in this thesis the synthesis of conjugatable lanthanide complexes and the spectroscopic properties of several lanthanide luminescent bioprobes synthesized in our laboratory. We will also present our effort to develop a strategy involving several cell penetrating peptides to internalize 2P-lanthanide complexes into living cells.

Keywords:
luminescence, probe, zinc, imaging, lanthanide