Citrate-capped AuNPs-induced redox reprogramming modulates the TP53-BAX/BCL2-CASP3 Axis, reinforcing antioxidant defense and promoting apoptotic signaling in liver Cancer.

[BACKGROUND] Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality worldwide, characterized by limited therapeutic options and poor prognosis. Nanomedicine offers promising approaches to overcome conventional treatment limitations through enhanced targeting capabilities. Gold nanoparticles (AuNPs) have garnered attention due to their exceptional physicochemical properties and biocompatibility. This study investigated the selective anti-cancer activity of citrate-capped AuNPs against HepG2 liver cancer cells compared to normal human fibroblasts (WI-38), focusing on molecular mechanisms underlying differential cytotoxicity.

[METHODS] Citrate-capped AuNPs were synthesized using a modified citrate reduction technique and characterized through complementary analytical methods (FTIR, TEM, XRD, zeta potential, UV-vis spectroscopy). Cytotoxicity was assessed via MTT assay and phase-contrast microscopy. Gene expression analysis using qRT-PCR examined key apoptosis-related markers (TP53, BAX, BCL2, CASP3). Mitochondrial membrane potential was evaluated using Rhodamine-123 fluorescence. Oxidative stress parameters and antioxidant enzyme activities were comprehensively analyzed to elucidate redox modulation.

[RESULTS] Synthesized AuNPs exhibited spherical morphology (32.6 nm), high crystallinity, and strong negative surface charge (-35 mV). AuNPs demonstrated selective cytotoxicity toward HepG2 cells (IC₅₀: 28.48 μg/mL) compared to WI-38 cells (IC₅₀: 464 μg/mL). Treatment upregulated TP53 and BCL2 expression while downregulating BAX and CASP3, creating a complex apoptotic signaling pattern. AuNPs induced significant mitochondrial membrane potential collapse (82 % reduction at 50 μg/mL). Remarkably, treatment enhanced antioxidant enzyme activities (SOD: +30 %, CAT: +22.4 %, GPx: +15 %) while reducing oxidative stress markers (ROS: -38.3 %, MDA: -30.3 %), suggesting redox reprogramming rather than oxidative damage.

[CONCLUSION] Citrate-capped AuNPs selectively induce cytotoxicity in HepG2 cells through TP53 activation, mitochondrial dysfunction, and redox reprogramming. Despite upregulated antioxidant defenses, cancer cells ultimately succumb to AuNPs-induced mitochondrial damage. The differential sensitivity between cancer and normal cells suggests a promising therapeutic potential, leveraging cancer cells' unique metabolic vulnerabilities while minimizing damage to healthy tissues.