1H NMR detection of mobile lipids as a marker for apoptosis: the case of anticancer drug-loaded liposomes and polymeric micelles.

Cultured cancer cells undergoing apoptosis show an increase in the NMR signal at a chemical shift of 1.3 ppm (-CH2-) corresponding to the so-called "mobile lipids" (ML) originating from the mobile acyl chains in triacylglycerides. A single NMR spectrum can provide an overview of the cellular metabolic changes caused by anticancer drugs providing qualitative and quantitative information on cellular metabolites. With this in mind, we studied the appearance of ML resonance in BT-20 and MCF-7 human breast cancer cells after their exposure to paclitaxel-loaded liposomes and polymeric micelles as a method to follow the apoptotic activity initiated by drug-loaded pharmaceutical nanocarriers. BT-20 and MCF-7 cells were incubated with 1.5 microg/mL paclitaxel-loaded liposomes or micelles for 24, 48, and 72 h in DMEM medium. Empty liposomes and micelles and untreated cells were used as controls. The progression of apoptosis induced in cancer cells by drug-loaded nanocarriers was readily detectable by NMR with a markedly increased area of the ML peak at 1.3 ppm. The presence of liposome- and micelle-forming materials did not induce or interfere with the increase in ML signals. Thus, the use of NMR for the detection of ML as a marker of apoptosis can be successfully applied to the study of pharmacological effects of anticancer drugs loaded into pharmaceutical nanocarriers.