a b s t r a c tOne possible approach to overcome solubility complications and enhance the biological activity of drugs is their incorporation into drug delivery systems. Within this scope, several nanosphere and nanocapsule formulations of a new inhibitor of p53-MDM2 interaction (xanthone 1) were developed and their physicochemical properties analyzed. Through the investigation of the effect of several empty nanoparticles on the growth of MCF-7 cells, it was possible to observe that four out of five formulations were cytotoxic and that some correlations between the toxic potential of these polymeric nanoparticles and their properties/composition could be extrapolated. One empty formulation of nanocapsules developed by emulsification/solvent evaporation and containing PLGA, PVA and Mygliol ® 812 was found to be noncytotoxic to this cell line. The corresponding compound 1-loaded nanocapsules showed an incorporation efficiency of 77% and revealed to be more potent than the free drug against cell growth inhibition, which may be related to the enhancement in its intracellular delivery. In an integrative study, the intracellular uptake of nanocapsules was confirmed using fluorescent 6-coumarin and well as compound 1 release from nanocapsules. Overall, it was possible to enhance the effect of the hit inhibitor of p53-MDM2 interaction through the development of suitable noncytotoxic polymeric nanoparticles.

Protein farnesyltransferase (FTase) is an important target in many research fields, more markedly so in cancer investigation since several proteins known to be involved in human cancer development are thought to serve as substrates for FTase and to require farnesylation for proper biological activity. Several FTase inhibitors (FTIs) have advanced into clinical testing. Nevertheless, despite the progress in the field several functional and mechanistic doubts on the FTase catalytic activity have persisted. This work provides some crucial information on this important enzyme by describing the application of molecular dynamics simulations using specifically designed molecular mechanical parameters for a variety of 22 CaaX peptides known to work as natural substrates or inhibitors for this enzyme. The study involves a comparative analysis of several important molecular aspects, at the mechanistic level, of the behavior of substrates and inhibitors at the dynamic level, including the behavior of the enzyme and peptides, as well as their interaction, together with the effect of the solvent. Properties evaluated include the radial distribution function of the water molecules around the catalytically important zinc metal atom and cysteine sulfur of CaaX, the conformations of the substrate and inhibitor and the corresponding RMSF values, critical hydrogen bonds, and several catalytically relevant distances. These results are discussed in light of recent experimental and computational evidence that provides new insights into the activity of this enzyme.