Peptidic Luminescent AuNCs for Biosensing

Gold nanoclusters (AuNCs) appear as a recent class of non-toxic fluorophores. Their brightness, their ultrasmall size (&lt; 2 nm) and large window of fluorescence lifetime (1ns – 1ms) and their good biocompatibility make them an attractive alternative as fluorescent probes for biological labeling and bioimaging.<br/>We demonstrated their in vivo targeting ability because of specific peptidic recognition groups (R. Cheichio et al. ACS Nano materials <b>2023</b>)<br/>Here we present the direct synthesis of original ultrasmall luminescent peptidic gold nanoclusters sensitive to pH. The versatility of small peptides permits to adjust the emission wavelength and the sensitivity of the emission intensity as well as the luminescent lifetime.<br/><br/>In addition due to their ultra-small size, we demonstrated that these probes are easily internalized into Arabidopsis plant from the roots and the leafs by adjusting the surface charge of the ligands. Their biodistribution in this model plant was evidenced by confocal microscopy. This chemical plateform provides AuNC dual nanoprobes with potential sensitivity to the environment for biosensing applications. Such nanostructures offer promising candidates for fluorescent in vivo biosensing and biolabeling.<br/>We also investigated the interaction of AuNC with Extracellular vesicles (EVs) which are well-known membrane-limited particles that are secreted by healthy and cancerous cells. EVs are heterogeneous in size and three subtypes are described depending on the location of secretion: microvesicles, myelinosomes and exosomes. EVs are identified in human follicular fluid as a mode of communication in the ovarian follicle (Neyroud A. S. et al. Int. J. Molecular Sci. <b>2022</b>). In addition EVs involved in cell-cell communication are considered as biomarkers for early cancer diagnosis. The analysis of their content thanks to AuNCs nanoprobes could provide informations about the origin and the biological function of the EVs. The EVs labeling with easily detectable nanoparticles could enable the development of a powerful tool for the early diagnosis of specific diseases.