Acute kidney injury (AKI) is defined as an abrupt fall in kidney function. Even with advanced technology, there is no single pharmaceutical treatment for AKI. The main mechanism behind the pathophysiology of AKI seems to be oxidative stress, although treatment with antioxidants does not provide complete amelioration of AKI. Liposomes are lipid vesicles consisting of a liquid core surrounded with one or more phospholipid bilayer. Polymeric nanoparticles on the other hand, are solid colloidal nanoparticles consisting mainly of macromolecules. Both are within the nano-sized range and it is possible to encapsulate both hydrophobic and hydrophilic drugs within them to suit targeted delivery options. The objective of the current study was to encapsulate antioxidants with different pharmacokinetic properties (α-tocopherol, curcumin, resveratrol, sinapic acid, ferulic acid and epicatechin) in liposomes and in polylactic acid (PLA)nanoparticles for the purpose of preventing or treating AKI. Liposomes were produced by the hydration of a lipid film to prepare large multilamellar vesicles, followed by membrane extrusion to form smaller unilamellar vesicles. Polymeric nanoparticles were prepared by double emulsification solvent diffusion method using PLA as the polymer. They were then characterized for their particle size, zeta-potential, surface morphology, drug loading, thermal properties, antioxidant activity, as well as for any toxicity and protection against oxidant injury caused by paraquat in renal NRK-52E cells. The liposomes were found to have a particle size of 194-260 nm and a zeta-potential of -12 to -6 mV. PLA nanoparticles were slightly larger in size ranging from 314-557 nm with a more negative charge on the surface (-37 to -23 mV). Loading efficiency varied between different antioxidants. HPLC results showed 76.1 ± 1.4%, 52.9 ± 11.1%, 12 ± 1.2%, 55.0 ± 6.5%, 20.8 ±3.5% & 10.23 ± 1.5% encapsulation for α-tocopherol, curcumin, resveratrol, sinapic acid, ferulic acid and, epicatechin liposomes, respectively. The loading efficiency for PLA nanoparticles was 67.6 ± 7.1%, 52.4 ± 22.7%, 40.8 ± 3%, 9.5 ±4.8%, 15.4 ± 4.7% & 5.4 ± 3.4% for the same order on encapsulated antioxidants. Images from scanning electron microscopy and light microscope showed nanoparticles to be spherical in shape. Fourier Transform-infrared spectroscopy and thermal analysis revealed that PLA nanoparticles resemble PLA structure and properties more than the antioxidants encapsulated within them. All encapsulated liposomes found to have some antioxidant activity measured using inhibition of peroxynitrite dependent tyrosine nitration test and ABTS assay with negligible activity for blank liposomes. There was no major reduction in cell viability after 24 hours exposure to antioxidant-loaded liposomes or PLA nanoparticles, which may indicate safety of these nanoparticles. However, there was arguable significant reduction using high doses of curcumin-loaded nanoparticles. All antioxidants encapsulated within liposomes and PLA nanoparticles showed some variableprotection against paraquat toxicity in NRK-52E cells. From these results, it can be concluded that liposomes and PLA nanoparticles developed in this study can provide some protective activity against oxidation in renal cells and have the potential after further investigation to be used to prevent or treat AKI.
Development of novel therapies using liposomes and poly-lactic acid nanoparticles encapsulated with dietary antioxidants for the treatment of acute kidney injury
Layas, K. (Author). Apr 2022
Student thesis: Doctoral Thesis