Design, synthesis and biological evaluation of phosphopeptides as Polo-like kinase 1 Polo-box domain inhibitors.

Polo-like kinase 1 (Plk1) is an anti-cancer target due to its critical role in mitotic progression. A growing body of evidence has documented that Peptide-Plk1 inhibitors showed high Plk1 binding affinity. However, phosphopeptides-Plk1 inhibitors showed poor cell membranes permeability, which limits their clinical applications. In current study, nine candidate phosphopeptides consisting of non-natural amino acids were rationally designed and then successfully synthesized using an Fmoc-solid phase peptide synthesis (SPPS) strategy. Moreover, the binding affinities and selectivity were evaluated via fluorescence polarization (FP) assay. The results confirmed that the most promising phosphopeptide 6 bound to Plk1 PBD with the IC50 of 38.99 nM, which was approximately 600-fold selectivity over Plk3 PBD (IC50 = 25.44 µM) and nearly no binding to Plk2 PBD. Furthermore the intracellular activities and the cell membrane permeability of phosphopeptide 6 were evalutated. Phosphopeptide 6 demonstrated appropriate cell membrane permeability and arrested HeLa cells cycle in G2/M phase by regulating CyclinB1-CDK1. Further, phosphopeptide 6 showed typical apoptotic morphology and induced caspase-dependent apoptosis. In conclusion, we expect our discovery can provide new insights into the further optimization of Plk1 PBD inhibitors.

Folic acid-modified nonionic surfactant vesicles for gambogenic acid targeting: Preparation, characterization, and in vitro and in vivo evaluation.

The aim of present study was to develop folic acid (FA)-modified nonionic surfactant vesicles (NISVs, niosomes) as carrier systems for targeted delivery of gambogenic acid (GNA). The FA-GNA-NISVs exhibited a mean particle size of 180.77 ± 2.41 nm with a narrow poly dispersion index of 0.147 ± 0.08 determined by dynamic light scattering. Transmission electron microscopy also revealed that the FA-GNA-NISVs were spherical with double-layer structure. Entrapment efficiency (EE%) and zeta potential of the optimal FA-GNA-NISVs were 87.84 ± 1.06% and -37.33 ± 0.33 mV, respectively. Differential scanning calorimetry demonstrated that the GNA was in a molecular or amorphous state inside the FA-NISVs in vitro release profiles suggested that FA-GNA-NISVs could release GNA at a sustained manner, and less than 60% of GNA was released from the FA-NISVs within 12 hours of dialysis. in vivo pharmacokinetic results illustrated that FA-GNA-NISVs had considerably higher Cmax , area under curve (AUC0 - t ) and accumulation in lung. The cell proliferation study shown that the FA-GNA-NISVs significantly enhanced the in vitro cytotoxicity against A549 cells. Flow cytometry and fluorescence microscopy further demonstrated that the FA-GNA-NISVs increased apoptosis compared with nonmodified GNA-NISVs and free GNA. Moreover, FA-GNA-NISVs induced A549 cell apoptosis in a dose-dependent manner. In addition, cellular uptake assays showed a higher uptake of FA-GNA-NISVs than GNA-NISVs as well as free GNA. Taken together, it could be concluded that FA-GNA-NISVs were proposed as a novel targeting carriers for efficient delivering of GNA to cancers cells.

A novel drug delivery system of mixed micelles based on poly(ethylene glycol)-poly(lactide) and poly(ethylene glycol)-poly(ɛ-caprolactone) for gambogenic acid.

In this study, a novel mixed polymeric micelles formed from biocompatible polymers, poly(ethylene glycol)-poly(lactide) (mPEG-PLA) and poly(ethylene glycol)-poly(ɛ-caprolactone) (mPEG-PCL), used as a novel nanocarrier to encapsulate gambogenic acid (GNA). GNA-loaded mixed polymeric micelles (GNA-MMs) was prepared by cosolvent evaporation method. The mean average size of GNA-MMs was (83.23 ± 1.06) nm (n = 3) and entrapment efficiency (EE%) of GNA-MMs was (90.18 ± 2.59) % (n = 3) as well as (12.36 ± 0.64) % (n = 3) for drug loading (DL%). Transmission electron microscopy revealed that the GNA-MMs were spherical with "core-shell" structures. Compared with free GNA solution, in vitro release of GNA from GNA-MMs showed a two-phase sustained release profile: an initial relatively fast phase and followed by a slower release phase. Pharmacokinetic results also indicated that the GNA-MMs have longer systemic circulation time and slower plasma elimination rate than free GNA solution. Moreover, the in vitro cytotoxicity assay showed that the IC50 values on HepG2 cells for GNA-MMs and free GNA were (5.67 ± 0.02) µM and (9.02 ± 0.03) µM, respectively. In addition, GNA-MMs significantly increased the HepG2 cellular apoptosis in a concentration-dependent manner. In conclusion, the results showed that mPEG-PLA/mPEG-PCL mixed micelles may serve as an ideal drug delivery system for GNA to prolong drug circulation time in body, enhance bioavailability and retained its potent antitumor effect.