Cellular Uptake of a Fluid-Phase Marker by Human Neutrophils from Solutions and Liposomes

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Abstract
In assessing the feasibility of utilizing the phagocytic activity of polymorphonuclear leukocytes (PMNs) for a more efficient drug delivery to the cell, the uptake of the fluid-phase marker lucifer yellow CH (LY) at 37°C by human PMNs from LY-containing liposomes was compared with that from solutions. In the presence of 10% autologous serum, the LY uptake at 37°C via phagocytosis of LY-containing liposomes was generally two orders of magnitude greater than that via pinocytosis for a given PMN source when the concentrations of PMN, LY, and total lipid were in the range of 107 cells/ml, 0.5 mg/ml, and 50 µmol/ml, respectively. As expected, the LY uptake via phagocytosis was critically dependent upon the LY entrapment efficiency in the liposome preparation. Interestingly, little LY uptake was found when the serum was heat inactivated (56°C × 30 min). The serum effect was upon liposome vesicles rather than upon the cells. The present study demonstrates that the use of particular drug carriers for targeted drug delivery to PMNs and possibly to an extravascular site mediated by the cell infiltration is a viable approach.