Design, Synthesis And Application Of Novel Cell Microenvironment Detection Fluorescent Probes

Based on hemicyanine dye and carbon dots,we have designed and synthesized three sensitive fluorescence probe.Through mechanism of ratiometric changes of ICT,endocytosis and targeting unit,we could realize qualitative and quantitative analysis of targets in vitro and microenvironment in living cells.(1)As traditional p H meters cannot work well for minute regions(such as subcellular organelles)and in harsh media,molecular p H-sensitive devices for monitoring p H changes in diverse local heterogeneous environments are urgently needed.We report a new dual-modal colorimetric/fluorescence merocyanine-based molecular probe(CPH)for ratiometric sensing of p H.The suitable p Ka value(6.44)allows CPH to presumably accumulate in lysosomes and become a lysosome-target fluorescent probe.By using CPH,the intralysosomal p H fluctuation stimulated by antimalaria drug chloroquine was successfully tracked in live cells through the ratiometric fluorescence images.Additionally,CPH could be immobilized on test papers,which exhibited a rapid and reversible colorimetric response to a cid/base vapor through the naked-eye colorimetric analysis.This proof-of-concept study presents the potential application of CPH as the molecular tool for monitoring intralysosomal p H fluctuation in live cells,as well as paving a way for developing the economic,re-usable,and fast-response optical p H meters for colorimetric sensing acid/base vapor with direct naked-eye observation(2)Lysosomes are membranous acidic vesicles,which contain numerous enzymes and proteins exhibiting a variety of activities and functions at acidic p H(4.5–5.5).Thus,development of suitable fluorescent probe for the specific labeling and imaging of lysosomes through the direct visual fluorescent signal is extremely important for understanding the dysfunction of lysosomes which might induce various pathologies,including neurodegenerative diseases,cancer,and Alzheimer's disease.A new carbon dot based fluorescent probe(CDs-PEI-ML)was designed and synthesized for highly selective imaging of lysosomes in live cells.The probe shows excellent water solubility and high photostability.We speculate the mechanism for selective staining of lysosomes with CDs-PEI-ML is presumably based on the endocytosis of CDs-PEI-ML into He La cells.CDs-PEI-ML was initially taken up by lysosomes through the endocytic pathway and then accumulated in acidic lysosomes.(3)On the basis of semicyanine skeleton,we have developed the ratiometric fluorescent probe,CPY,for lysosomal p H measurements.The probe shows excellent lysosome-targeting ability.More importantly,using probe CPY the change of lysosomal p H with temperature is investigated,revealing the rising of the lysosomal p H during heat shock and the inreversibility of this process.