RESUMO
AIEgens have emerged as a promising alternative to molecular rotors in bioimaging applications. However, transferring the concept of aggregation-induced emission (AIE) from solution to living systems remains a challenge. Given the highly heterogeneous nature and the compartmentalization of the cell, different approaches are needed to control the self-assembly within the crowded intricate cellular environment. Herein, we report for the first time the self-assembly mechanism of an anthracene-guanidine derivative (AG) forming the rare and highly emissive T-shaped dimer in breast cancer cell lines as a proof of concept. This process is highly sensitive to the local environment in terms of polarity, viscosity, and/or water quantity that should enable the use of the AG as a fluorescence lifetime imaging biosensor for intracellular imaging of cellular structures and the monitoring of intracellular state parameters. Different populations of the monomer and T-shaped and π-π dimers were observed in the cell membrane, cytoplasm, and nucleoplasm, related to the local viscosity and presence of water. The T-shaped dimer is formed preferentially in the nucleus because of the higher density and viscosity compared to the cytoplasm. The present results should serve as a precursor for the development of new design strategies for molecular systems for a wide range of applications such as cell viscosity, density, or temperature sensing and imaging.
Assuntos
Antracenos , Imagem Óptica , Citoplasma , Membrana Celular , Polímeros , ÁguaRESUMO
The use of two nanoparticles for quantitative pH measurements in live cells by means of fluorescence lifetime imaging microscopy (FLIM) is investigated here. These nanoparticles are based on CdSe/ZnS quantum dots (QDs), functionalized with N-acetylcysteine (CdSe/ZnS-A) and with a small peptide containing D-penicillamine and histidine (CdSe/ZnS-PH). CdSe/ZnS-A has tendency to aggregate and nonlinear pH sensitivity in a complex medium containing salts and macromolecules. On the contrary, CdSe/ZnS-PH shows chemical stability, low toxicity, efficient uptake in C3H10T1/2 cells, and good performance as an FLIM probe. CdSe/ZnS-PH also has key advantages over a recently reported probe based on a CdSe/ZnS QD functionalized with D-penicillamine (longer lifetimes and higher pH-sensitivity). A pH(±2σ) of 6.97 ± 0.14 was determined for C3H10T1/2 cells by FLIM employing this nanoprobe. In addition, the fluorescence lifetime signal remains nearly constant for C3H10T1/2 cells treated with CdSe/ZnS-PH for 24 h. These results show the promising applications of this nanoprobe to monitor the intracellular pH and cell state employing the FLIM technique.