Phospholipid-Modified
Upconversion Nanoprobe for Ratiometric
Fluorescence Detection and Imaging of Phospholipase D in Cell Lysate
and in Living Cells
- Publication date
- Publisher
Abstract
Phospholipase D (PLD) is a critical
component of intracellular
signal transduction and has been implicated in many important biological
processes. It has been observed that there are abnormalities in PLD
expression in many human cancers, and PLD is thus recognized as a
potential diagnostic biomarker as well as a target for drug discovery.
We report for the first time a phospholipid-modified nanoprobe for
ratiometric upconversion fluorescence (UCF) sensing and bioimaging
of PLD activity. The nanoprobe can be synthesized by a facile one-step
self-assembly of a phospholipid monolayer composed of poly(ethylene
glycol) (PEG)ylated phospholipid and rhodamine B-labeled phospholipid
on the surface of upconversion nanoparticles (UCNPs) NaYF<sub>4</sub>: 20%Yb, 2%Er. The fluorescence resonance energy transfer (FRET)
process from the UCF emission at 540 nm of the UCNPs to the absorbance
of the rhodamine B occurs in the nanoprobe. The PLD-mediated hydrolysis
of the phosphodiester bond makes rhodamine B apart from the UCNP surface,
leading to the inhibition of FRET. Using the unaffected UCF emission
at 655 nm as an internal standard, the nanoprobe can be used for ratiometric
UCF detection of PLD activity with high sensitivity and selectivity.
The PLD activity in cell lysates is also determined by the nanoprobe,
confirming that PLD activity in a breast cancer cell is at least 7-fold
higher than in normal cell. Moreover, the nanoprobe has been successfully
applied to monitoring PLD activity in living cells by UCF bioimaging.
The results reveal that the nanoprobe provides a simple, sensitive,
and robust platform for point-of-care diagnostics and drug screening
in biomedical applications