Examining the Anti-Tumor Activity of Dp44mT-Loaded Nanoparticles In Vitro.

We have recently reported encapsulating an antitumor iron chelator, Dp44mT (Di-2-pyridylketone-4,4dimethyl-3-thiosemicarbazone), in nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA). In this paper, we examine the effectiveness of this nano-formulation, referred to as Dp44mT-NPs, against several cancer cell lines in vitro; specifically, we evaluate the cytotoxicity of this formulation in glioma (U87, U251), breast (MCF7), and colorectal (HT29) cancer cell lines. Cell viability results from treatment of glioma cells with Dp44mT-NPs for 24-72 hrs revealed that these NPs were highly toxic towards these malignant cells with very low IC50 values (<100 nM). Although addition of a PEG (poly(ethylene glycol)) layer to the surface of NPs reduced their toxicity in glioma cells, they remained highly toxic towards these cells (IC50 of 135-210 nM). Dp44mT-NPs were also toxic towards breast MCF7 and colorectal HT29 cells, but at higher dosages (IC50 >1 µM) compared to glioma cells. Addition of PEG to these NPs, again lowered their toxicity in these cells. Varying the percentage of PEG on NPs resulted in changes in their cytotoxicity, highlighting the necessity of further optimization of this parameter. This study, overall, demonstrates the therapeutic potential of Dp44mT-NPs against different malignant cells, with particularly promising results in highly-aggressive glioma tumor cells.

Fabrication and Optimization of Dp44mT-Loaded Nanoparticles.

This paper describes the modulation of polymeric nanoparticle (NP) preparation to produce an optimal nanocarrier for delivery of the potent anti-tumor iron chelator, Di2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) towards application in cancer therapy. We have previously shown the potential of poly (lactic-co-glycolic acid) (PLGA) NPs as a nano-carrier for delivery of Dp44mT to malignant cells. The focus of this study is to alter the fabrication parameters to improve the characteristics of these NPs as a delivery vehicle for Dp44mT. To this end, PLGA NPs encapsulating Dp44mT are fabricated using the nanoprecipitation method with systematic variations in (i) the amount of surfactant poly (vinyl alcohol) (PVA) in aqueous phase, and (ii) the drug to polymer ratio in organic phase. The resultant NPs are characterized for size, surface potential, encapsulation efficiency, and drug release profile. Results of this study showed that increasing the PVA % (within the examined range of 0.5-4% w/v) and decreasing the Dp44mT to PLGA ratio (within the tested range of 0.0375-0.3: 1 mg/mL) both led to an increase in drug encapsulation efficiency. Focusing on the optimal PVA percentage, we found that the changes in drug to polymer ratio did not have a significant impact on the size distribution and surface potential of Dp44mT-NPs and these NPs remained in the desirable range of 80-120 nm. Lastly, the release of Dp44mT from NPs differed for different Dp44mT: PLGA ratios, providing a means to further optimize the NP formulation for future cancer treatment applications.