Non-invasive label-free imaging of sub-cellular architecture and intracellular behavior of nano-drug-delivery carriers using Raman micro-spectroscopy.

摘要

Microscopic imaging of sub-cellular architecture provides crucial insight into the details of cellular biology. A widely used technique to image cellular processes is fluorescence microscopy. Although the technique is well established, there are certain difficulties encountered, such as low contrast and photo-bleaching. When utilized as a labelling method for a certain molecule of interest, fluorophores may potentially alter its biochemical properties, or leach out of the system of interest, if they are utilized to visualize a compartment.;Novel optical imaging methods, based on vibrational spectroscopy coupled with optical microscopy, such as Raman microspectroscopy, have been gaining recognition in their ability to obtain the distribution of biochemical components of a sample non-invasively. Raman spectroscopy provides a label-free method to assess and image cellular processes, without the use of extrinsic fluorescent dyes. The sub-micron resolution of the confocal Raman instrumentation, allows intracellular imaging cellular organelles on the scale of conventional microscopy.;We used the technique to image sub-cellular architecture, as well as monitor uptake, intracellular kinetics and dynamics of biocompatible nano-delivery systems. Four systems imaged were phospholipid-based liposomes and micelles, as well as two biodegradable polymer-based systems PCL and PLGA. We have also analyzed dissociation of a chemotherapeutic from the PCL nanocarriers. These processes were monitored via the dynamics of the molecule-characteristic peaks of the four drug-delivery systems. As the catabolic pathways proceed, shifts and variations in peak intensities and intensity ratios in the rendered Raman spectra unequivocally delineate their degradation patterns.