A pragmatic approach to combat lipotoxicity in HepG2 cells: Engineering of curcumin loaded polydopamine coated Zn-MOF

Abstract

Non-alcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid accumulation, oxidative stress, and inflammation, but therapeutic options are limited due to the poor bioavailability of compounds such as curcumin. To address this limitation, we developed polydopamine-coated, curcumin-loaded zinc metal-organic framework (Curcumin-Np) and evaluated their physicochemical properties, sustained-release behavior, and biological activity in an in vitro lipotoxicity model. Curcumin was encapsulated within resorcinol-diacetic acid-based zinc MOFs (encapsulation efficiency ∼75%), and a polydopamine coating was applied to improve stability and regulate release. Dynamic light scattering, scanning electron microscopy, and FTIR spectroscopy were employed to determine particle size, zeta potential, morphology, and surface functional groups, respectively. Release profiles were studied at pH 6.8 over 48 h. HepG2 cells exposed to free fatty acids served as an in vitro model of lipotoxicity. The CCK-8 assay was employed to ascertain cell viability, and a fluorescence-based ROS assay was used to measure intracellular ROS generation. Lipid accumulation was evaluated by Nile Red staining, intracellular triglycerides were quantified colorimetrically, and prolyl endopeptidase (PREP) inhibition kinetics were assessed using a cell-free enzyme assay. Furthermore, qPCR was used to assess lipid metabolism- and stress-related gene expression. Polydopamine coating increased the particle size from 84 to 220 nm and improved the zeta potential to -48 mV, indicating better colloidal stability. Curcumin-Np showed controlled curcumin release, with about 73% release over 48 h, in comparison to 25% release from free curcumin. In the FFA-induced HepG2 lipotoxicity model, Curcumin-Np improved cell viability compared with the FFA-treated group, reduced intracellular ROS generation (1.8-1.2-fold of the control level), decreased Nile Red-positive lipid droplet accumulation, and reduced intracellular triglyceride levels from about 2700-2800 to 2100-2200 pg/mg protein. qPCR analysis showed recovery of AMPKα and NRF2 expression and reduction of FFA-induced SREBP-1c, PREP, and p53 expression following Curcumin-Np treatment. In the cell-free PREP assay, curcumin demonstrated non-competitive inhibition, with an IC50 and Ki of approximately 35 and 45.7 µM, respectively. Curcumin-Np improved curcumin activity in an in vitro HepG2 lipotoxicity model by reducing oxidative stress and lipid accumulation while supporting PREP inhibition and favorable gene expression changes. These findings suggest that PDA-coated Zn-MOF-based curcumin delivery is a promising approach for further investigation of NAFLD/NASH.