In Vitro Imaging of Lycopene Delivery to Prostate Cancer Cells

The ability to monitor the uptake and distribution of food nutrients in in vitro cell culture models is key to understanding the efficacy of these nutraceuticals to treat and prevent disease. Lycopene is a carotenoid found in chloroplasts and chromoplasts of tomatoes, providing the familiar red color, and a bioactive that inhibits prostate carcinogenesis. We employed live-cell Raman microscopy to visualize lycopene delivery from tween 80 micelles into PC-3 prostate cancer cells. The tween 80 micelle provides a mimic of natural lipoprotein complexes that deliver lycopene in vivo, overcomes the low aqueous solubility of lycopene and challenges replicating physiological uptake to cells, and provides a stable signal to assess cellular uptake of the nutraceutical formulation. The Raman images indicate subcellular localization of the lycopene within the cells. The lycopene Raman signal is resonantly enhanced at an excitation wavelength of 532 nm, providing a convenient, sensitive, and label-free technique to detect and quantify lycopene uptake in living cells. Analysis of the acquired Raman spectra in the maps determines the concentration of lycopene at each point in the cell. In addition to the expected lycopene Raman signal, Raman scattering from the tween 80 vehicle is also mapped in the cells. The Raman data correlates with scattering features observed in darkfield microscopy images of the cells, which display the cell membrane and other features for reference. Overall, the Raman maps indicate lycopene likely accumulates in lipid membranes of cytoplasmic organelles.