Resonance Raman Spectral Imaging of Intracellular Uptake of β-Carotene Loaded Poly(D,L-lactide-co-glycolide) Nanoparticles

The use of nanoparticles for drug delivery has been drawing considerable attention in pharmaceutical research. With increasing diversity and potential of various carrier systems, it is important to study the impact of nanocarriers on sub-cellular metabolic processes and organelles, since the delivery of a drug usually involves intra-cellular internalization. Here, we employ Raman microscopy as a non-invasive method for cellular and sub-cellular imaging, to monitor the uptake and translocation patterns of particles based on poly-(D,Llactide-co-glycolide) over time. As the technique relies on inherent signals from the molecules of interest, it does not rely on external labels or dyes, which is an advantage over fluorescence labeling. For this purpose, the particles were loaded with β-carotene. The conjugated π-system of the molecule has a large Raman scattering cross section and gives rise to resonance Raman effects, which can enhance the sensitivity by order of magnitudes. β-Carotene as a provitamin is not soluble in water and thus usually of low bioavailability, which is enhanced by encapsulation into nanoparticles.