Synergistic Effects of Green Nanoparticles on Antitumor Drug Efficacy in Hepatocellular Cancer

Background/Objectives: Cancer remains one of the leading causes of mortality worldwide. Despite significant advancements in treatment strategies and drug development, survival rates remain low and the adverse effects of conventional therapies severely impact patients’ quality of life. This study evaluates the therapeutic potential of plant-derived extracts in hepatocellular carcinoma treatment, with a focus on minimizing side effects while enhancing efficacy. Methods: This research investigates the in vitro synergistic effect of silver bio-nanoparticles synthesized from Clematis vitalba, Melissa officinalis, and Taraxacum officinale extracts (Clematis vitalbae extractum—CVE, Melissae extractum—ME, Taraxaci extractum—TE) in combination with liver cancer drugs, sunitinib (SNTB) and imatinib (IMTB), on HepG2 (human hepatocellular carcinoma) and HUVEC (human umbilical vein endothelial) cell lines. The silver nanoparticles (AgNPs) were characterized using UV-Vis spectroscopy, dynamic light scattering (DLS), zeta potential analysis, and scanning electron microscopy (SEM). The antitumor effects were evaluated through cell viability assays after 24 and 48 h of exposure, with additional cytotoxicity tests on HUVEC cells. Results: Results indicated that Melissa officinalis-derived silver nanoparticles (ME AgNPs) and Clematis vitalba extract with silver nanoparticles (CVE AgNPs) significantly reduced HepG2 cell viability. Their efficacy improved when combined with conventional therapies (SNTB + ME AgNPs 1:1 vs. SNTB: 20.01% vs. 25.73%, p = 0.002; IMTB + ME AgNPs 1:1 vs. IMTB: 17.80% vs. 18.08%, p = 0.036; SNTB + CVE AgNPs 1:1 vs. SNTB: 18.73% vs. 25.73%, p = 0.000; SNTB + CVE AgNPs 1:2 vs. SNTB: 26.62% vs. 41.00%, p = 0.018; IMTB + CVE AgNPs 1:1 vs. IMTB: 12.99% vs. 18.08%, p = 0.001). Taraxacum extract exhibited similar cytotoxicity to its nanoparticle formulation but did not exceed the efficacy of the extract alone at 24 h. Selectivity index assessments confirmed that AgNPs-based formulations significantly improve cytotoxicity and selectivity to HepG2 cells. Among the tested extracts, CVE demonstrated the strongest antitumor effect, enhancing the efficacy of synthetic drugs (CI < 1). SNTB + TE AgNPs (5% EtOH) also demonstrated consistent synergy at high doses, while SNTB + CVE AgNPs provided broad-range synergy, making it suitable for dose-escalation strategies. Conclusions: These findings underscore the potential of nanoparticle-based formulations in combination therapies with targeted kinase inhibitors such as sunitinib and imatinib. Future research should focus on in vivo validation and clinical trials to confirm these findings.