Quantum dot cluster (QDC)-loaded phospholipid micelles as a FRET probe for phospholipase A₂ detection

Abstract

A simple assay for phospholipase A2 (PLA2) enzyme was developed based on a fluorescence resonance energy transfer (FRET) probe using the quantum dot cluster (QDC)-loaded phospholipid micelles. The probe was prepared by encapsulating many small hydrophobic quantum dots (QDs) within the hydrophobic core of micelles that were formed from the coassembly of hydrogenated soy phosphatidylcholine phospholipids (HSPC) and fluorescent lipids (NBD-PC). QDCs formed within the micelle core served as the substrate for NBD fluorescence quenching through FRET. The QDC-loaded micelles showed very low background fluorescence. As the PLA2 enzyme selectively digested lipids, the NBD fluorescence was recovered from its quenched state, leading to the sensitive detection of PLA2. This assay provided a limit of detection (at a signal-to-noise ratio of 3) of 3 U/L for PLA2. In the presence of a PLA2 inhibitor, the fluorescent response of the sensor for PLA2 decreased, indicating that the assay could also be used for screening the PLA2 inhibitors.

4-Amino-TEMPO loaded liposomes as sensitive EPR and OMRI probes for the detection of phospholipase A2 activity

“…Among the currently available methods, those based on fluorescence detection are the most sensitive ones, showing Limit of Detections (LoD) < 10 U/L 17 . They rely either on the cleavage of fluorescent molecules from properly designed systems 20 , 21 and on the membrane permeabilization of lipid vesicles to remove fluorescence “quenching” effects 8 , 22 – 25 . The main disadvantages of the fluorescent based detection methods deal with the high background signal due to the autofluorescence of biological samples as well the poor penetration of the light into the opaque samples represented by cells and tissues extracts re-suspended in aqueous media.…”

Photostability of quantum dot micelles under ultraviolet irradiation

“…After modifying the QD surface, it is difficult to keep the earlier‐mentioned qualities of QDs. However, phospholipid micelles are active carriers of multiple QDs . The interaction of hydrophobic CdSe/ZnS QDs with amphiphilic phospholipid polyethylene glycol (PEG) results in micelles with tens of QDs in the core .…”