Polymer stabilized, phenytoin-loaded nanomicelles as promising nanocarriers: In silico and in vitro evaluations

Abstract

Many drugs currently used in clinics to treat different diseases show low solubilities in aqueous solutions and must be then administered with the aid of organic solvents within the designed formulations leading to harmful health effects. For such reason, drug delivery using nanocarriers appears as an excellent alternative since it improves the solubilization and controlled release of many different pharmaceuticals, favoring the decrease of the overall administered therapeutic doses and by diminishing the risk of potential associated adverse side effects. Among the different types of nanocarriers, those based on polymeric micelles are an excellent option since the polymer structure and composition may be tuned in order to regulate the characteristics and properties of the resulting nanoassemblies to maximize drug solubilization and release profiles. For this reason, in this paper a drug delivery nanosystem based on oil-in-water polymeric-based microemulsion used to load the anti-epileptic phenytoin drug (PHT) was developed in the oily phase. Two different biocompatible polymers were evaluated to form the nanomicelles and maximize encapsulation efficiencies and colloidal stability: The amphiphilic triblock copolymer Pluronic F127, which poses the ability to cross the blood brain barrier (BBB), and the natural lipophilic lignin, which bears antipathogenic properties. Density functional theory (DFT) calculations were performed with the 6-31G(d) basis set to elucidate the interactions of PHT with F127 and lignin monomers. Simulation data showed that hydrogen bonding (HB) interactions between PHT, F127 and lignin are the predominant force to allow for drug solubilization and stability. Atoms in molecules (AIM) and natural bond orbital (NBO) analyses were performed to evaluate the strength of such HB. and their drug encapsulation efficiency, release profiles, and antibacterial susceptibility were determined. Moreover, the cytotoxicity of the developed nanoformulations together with a morphological examination of PC12 and NIH cells after drug-loaded nanocarrier administration and subsequent uptake were also investigated. In this manner, the obtained nanocarriers were also characterized by dynamic light scattering (DLS) and zeta potential, showing a nanometer size (between ca. 16 and 22 nm) and surface negative charge. PHT loading into F127 and lignin nanomicelles were ca. 96.7 ± 1.5% and 68.2 ± 3.5%, respectively, and the drug release profile kinetics of F127/PHT-loaded nanomicelles was rather slower compared to that of lignin/PHT-loaded ones. On the other hand, in vitro cytotoxicity data confirmed the lack of any significant cytotoxicity of PHT-loaded nanomicelles in both NIH/3T3 and PC12 cell lines, but a slightly higher cell viability and well-preserved cell morphology was observed for PC12 cells compared to NIH/3T3 ones. After culturing in chocolate blood agar medium inoculated with F127/PHT-loaded and lignin/ PHT-loaded nanomicelles, pathogenic bacteria did not grow despite confirming certain antimicrobial character of the encapsulated drug. Hence, thanks to their excellent encapsulation and biocompatibility properties, these nanocarriers appear as an excellent option to configure new drug delivery nanocarriers of hydrophobic drugs.