Novel NAC-loaded poly(lactide-co-glycolide acid) nanoparticles for cataract treatment: preparation, characterization, evaluation of structure, cytotoxicity, and molecular docking studies

Abstract

Background: N-acetylcarnosine (NAC), a dipeptide with powerful antioxidant properties that is extensively used as a pharmaceutical prodrug for the treatment of cataract and acute gastric disease, was investigated by molecular dynamics with the GROMACS program in order to understand the solvent effect on peptide conformation of the peptide molecule used as a component of a drug and which presents substantial information on where drug molecules bind and how they exert their effects. Besides, molecular docking simulation was performed by using the AutoDock Vina program which identify the kind of interaction between the drug and proteins. A delivery system based on poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with NAC (NAC-PLGA-NPs) for the treatment of cataract was prepared for the first time in this study in order to enhance drug bioavailability and biocompatibility. The objective of this work was to prepare and evaluate the structural formulation, characterization, and cytotoxicity studies of NAC-loaded NPs based on PLGA for cataract treatment.

Methods: PLGA and NAC-loaded PLGA NPs were prepared using the double emulsion (w/o/w) method, and characterizations of the NPs were carried out with UV-Vis spectrometer to determine drug concentration, the Zeta-sizer system to analyze size and zeta potential, FTIR spectrometer to determine the incorporation of drug and PLGA, and TEM analysis for morphological evaluation.

Results: NAC-loaded PLGA NPs were successfully obtained according to UV-Vis and FTIR spectroscopy, Zeta-sizer system. And it was clearly observed from the TEM analysis that the peptide-loaded NPs had spherical and non-aggregated morphology. Also, the NPs had low toxicity at lower concentrations, and toxicity was augmented by increasing the concentration of the drug.

Discussion: The NAC molecule, which has been investigated as a drug molecule due to its antioxidant and oxidative stress-reducing properties, especially in cataract treatment, was encapsulated with a PLGA polymer in order to increase drug bioavailability. This study may contribute to the design of drugs for cataract treatment with better reactivity and stability.

Keywords: FTIR; GROMACS; Molecular docking; Molecular dynamic; NAC; Nanoparticle; PLGA; TEM; Zeta-sizer.

Figure 1. Initial conformation of N-acetylcarnosine molecule (A), in a cubic box solvated with four Na⁺ and four CL⁻ ions (B), in a cubic box solvated with 2,317 water molecules and eight ions (C).

Figure 2. Radius of gyration (Rg) of system.

Figure 3. Enthalpy of system solvated with 2,317 water molecules and eight ions.

Figure 4. Calculated UV–Vis absorption spectra of NAC peptide (A) in water, (B) in methanol.

Figure 5. Experimentally recorded UV–Vis absorption spectra of NAC peptide: (A) water, (B) methanol.

Figure 6. Patterns of principle frontier molecular orbitals of NAC obtained with TD-DFT/B3LYP/6-311++G (d,p) (A) in water, (B) in methanol.

Figure 7. MEP maps of NAC obtained with (A) water solution and (B) methanol solution.

Figure 8. Schematic for docked conformation of active site of title compound.

Figure 9. Schematic for docked conformation of ASP-16, VAL-17, and LYS-18 in active site within protein.

Figure 10. Schematic hydrogen bonding (yellow) for docked conformation of active site of title compound with (A) ASP-16, (B) VAL-17, and (C) LYS-18.

Figure 11. ATR spectra of NAC, NAC-PLGA-NPs, and PLGA-NPs.

Figure 12. Standard calibration curve of NAC at 220 nm.

Figure 13. Size distribution graph of blank PLGA-NPs.

Figure 14. Zeta potential graph of blank PLGA-NPs.

Figure 15. Size distribution graph of NAC-PLGA-NPs.

Figure 16. Zeta potential graph of NAC-PLGA-NPs.

Figure 17. TEM images of NAC-PLGA-NPs.

Figure 18. EDS analysis of NAC-PLGA-NPs.

Figure 19. Toxicity of NAC molecule on L929 cells.

Figure 20. Toxicity of NAC-PLGA-NPs on L929 cells.