We have successfully encapsulated two proteins, bovine serum albumin (BSA) and p53, in chitosan-tripolyphosphate (TPP) nanoparticles at various pH values from 5.5 to 6.5 and delivered the particles to human melanoma cells. The particles have diameters ranging from 180 nm to 280 nm and a zeta potential of +15 to + 40 mV. Cellular uptake of the particles by human skin melanoma cells was evaluated by: (i) fluorescence microscopy and (ii) gel electrophoresis showing that FITC-labeled BSA and p53 could be recovered in the soluble cell fraction after lysis of the cells. Our data also show that the highest cellular uptake takes place at the lowest pH as the particles have the highest positive charge under these conditions. The method we describe appears to be a general method for delivery of proteins to cells using chitosan-TPP nanoparticles as a drug delivery system, since structurally unrelated proteins such as BSA and p53 with different isoelectrical points can be encapsulated in the chitosan-TPP nanoparticles and be effectively internalized by the cells.
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