A fluorescent nanoprobe based on cell-penetrating peptides and quantum dots for ratiometric monitoring of pH fluctuation in lysosomes.

A lysosome-targeting ratiometric fluorescent nanoprobe based on cell-penetrating peptides (CPPs) and quantum dots (QDs) has been developed for monitoring pH fluctuation in living cells. The as-prepared nanoprobe is constructed by Rhodamine B labeled R9RGD CPPs as H+ response unit and the red fluorescent QDs as reference unit to achieve ratiometric pH measurement. With the help of RhB-R9RGD CPPs, the nanoprobe efficiently stains lysosomes and enables discernment of lysosomal pH fluctuation in cells treated with different pH buffers and drug stimulation. The method of using dye labeled CPPs to realize functionalization of nanoparticle in one-step reported herein is expected to obtain wider applications in the detection of subcellular active substances by combining different small molecular probes and functional peptides.