Preparation and Characterization of Starch Nanoparticles for Delivery of Histone Deacetylase Inhibitor CG-1521 in Breast Cancer Treatment

Abstract

Starch nanoparticles offer many possibilities in drug delivery systems due to their biocompatibility and appropriate physicochemical properties. Sufficient systems have not yet been designed to deliver histone deacetylase inhibitors due to their poor solubility. These inhibitors are the novel therapeutic agents used for the treatment of several cancer’s types including breast cancer. The low solubility of the histone deacetylase inhibitors significantly reduces their bioavailability and therapeutic indices. In this study, biocompatible starch nanoparticles have been synthesized to improve the sub-optimal therapeutic index of the CG-1521. Physicochemical properties of nanoparticles (size, zeta potential, morphology, drug loading, and release) were optimized. The fabricated nanoparticles possess the required optimal average size (180 nm) and polydispersity index (0.138) for enhanced permeability and retention for tumor targeting. Slightly negative zeta potential (-16.2 mV) of nanoparticles provides electro-kinetics stability and minimum aggregation. The scanning electron and atomic force microscopies analyses indicates that nanoparticles had spherical topographies and homogeneous distribution which is important for the fate of nanoparticles for cellular uptake. The spherical shape of nanoparticles provides faster internalization rates results in higher uptake. The physical characterization of nanoparticles followed by substantially high encapsulation efficiency (~69%) of drug. The encapsulation process reduces the rate of release of drug resulted in extended exposure to the drug. The faster drug release of encapsulated drug in acidic environment promotes more accumulation of drug in tumor site. In this study, the release of drug from nanoparticles in acidic environment exhibited additional release (16%) of encapsulated drug. The cytotoxic and apoptotic capacities of nanoparticles were investigated using MCF-7 breast cancer cells. The cytotoxic studies results demonstrated that at the equivalent concentration the encapsulated drug was more effective at inducing cell death. The apoptosis results confirmed that the encapsulated drug show significant apoptotic effect (60.45% apoptotic cells) in comparison free drug (28.45%) The cell cycles analysis demonstrated that treatment with the same concentration of encapsulaed drug significantly increase the cell proportion at the G1 phase (53.0%) compare to G1 population (49.5%) treated with free drug. G1/S arrest is most likely due the stabilization of acetylated isoform of p53 gene. To evalute the targeting potential of nanoparticles, the cytotoxic effects of Folic Acid–modified nanoparticles on MCF-7 and MDA-MB-231 breast cancer cell lines were investigated. The results showed that the response of triple negative cell line MDA-MB-231 was more sensitive to modified formulation than MCF-7 cell line. The higher sensitivity is due the more aggressiveness of MDA-MB-231 cells and higher expression level of folate receptors compared to MCF-7 cells. The biological mechanism of drug-loaded nanoparticles at the molecular level has been evaluated using real-time quantitative PCR. The transcripts level of several genes involves in cell death, apoptosis, cell cycle and spindle formation were measured after treatments with free and encapsulated for 48 hours. The expression levels of majority of the transcripts used in the study showed a similar trend of upregulation or downregulation after interaction with the same dose of free and encapsulated drug. These results confirmed that the molecular activity of drug did not alter with the encapsulation process of drug. Within the scope of this study, the nanoencapsulation of CG-1521 significantly reduces the release of drug over time and increases its cytotoxic activity relative to the free drug at the same concentration. Moreover, CG-1521 encapsulated nanoparticles significantly induce cell cycle arrest and apoptosis in MCF-7 cells. This study demonstrates that starch nanoparticles may be a suitable and potential drug carrier candidate for histone deacetylase inhibitors in breast cancer treatment without interfering with the inhibitor’s molecular activity.