Micro-Raman Spectroscopy for Detection of Label-Free and Oil Red O Labeled PEGylated Nanoliposomes in hCmec/D3 Cell Internalization Studies

Rapid development of nanomedicines necessitates advancement in internalization techniques which can accurately distinguish between the complex environments of cells and nanocarriers. Internalization (or endocytosis) studies of oil red O labeled and label-free PEGylated-lecithin/cholesterol nanoliposomes was performed using micro-Raman spectroscopy. The C.O stretching vibrations and CCH scissoring bendings of naphthalene ring around 1225 cm(-1) as well as the N=N stretching vibrations at 1377 cm(-1) are prominent peaks absent from the label-free spectra which can be used for detection of internalized oil red O labeled nanoliposomes. Suitability of oil red O as a liposome marker was confirmed by stability studies of the incorporated dye and automated fluorescence cell counting. The C.C stretching region with a prominent wide band centered at 1080 cm(-1) indicative of larger gauche conformer content typical for the lecithin-cholesterol nanoliposomes and the strong maximum at 980 cm(-1) associated with O-C-C-N+ stretching vibrations of the liposome polar head groups are important for studying label-free nanoliposome cell internalization.