## 4 Conclusions  
In summary, the synthesis of small-dimension GNPs was successfully performed via the colloidal chemical reduction process. The formed nanoparticles were well characterized in terms of their morphology and crystalline character, analyzed via TEM equipped with high resolution (HR-TEM) to validate high crystallinity and good structural morphology in the obtained products. TEM revealed that the diameter size of GNPs ranged from 10-15 nm for GNPs-1 to 20-30 nm for GNPs-2 to 45 nm for GNPs-3, with spherical shapes. The different-sized GNPs were applied against HepG2 cancer cells, with results that indicated that cytotoxicity in cancer cells is dose-dependent, from very low concentrations (1 \(\mathrm{\SIUnitSymbolMicro g}\)/mL) to high concentrations (100 \(\mathrm{\SIUnitSymbolMicro g}\)/mL). In all three different sizes of GNPs, minimal effect was observed initially from 1 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, 2 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, and 5 \(\mathrm{\SIUnitSymbolMicro g}\)/mL concentrations, but as the concentrations were increased to 10 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, 25 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, and 50 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, and 100 \(\mathrm{\SIUnitSymbolMicro g}\)/mL, respectively, the growth of cancer cells was significantly affected. In this study, cell viability was significantly affected by small-sized NPs, as compared with the effect of other-sized NPs. This result may be due to the high surface area of small-sized NPs, as compared to other types; in addition, NPs that are very small in size exhibit low density, as compared with other NPs. In the current study, we found that of the three different-sized nanoparticles GNPs-1, GNPs-2, and GNPs-3, small-sized nanoparticles (GNPs-1, 10-15 nm) is most effective in controlling cancer cells. The small size facilitates easy entry into cells and reaction with cell organelles. NPs can possibly be used as anticancer nanodrugs for cancer treatment. This study indicates that different-sized gold nanoparticles induce cytotoxicity and apoptosis through different genes (i.e., the p53, Bax, and caspase pathways) in cancer cells, and mediate via ROS generation. At present, the annihilation of cancer cells is controlled by various surgical and therapeutic means, as well as by a number of organic drugs. These methods, including, chemotherapy, radiotherapy, immunotherapy, and radiosurgery, involve the use of complex drugs that are costly and fail to provide complete satisfaction. The aim of this study is to achieve a more fruitful option at a very low cost. Nanotechnology provides an excellent platform and a good alternative in forming a number of inorganic or colloidal nanoparticle-based drugs to diminish the growth of cancer cells much more effectively. Nano-based drugs are very cost-effective and affordable for economically-deprived persons. Due to their very small size, they exhibit high surfaces and sufficient volume ratio to allow for entry directly into cancer cells. Based on the obtained results, gold nanoparticles show great efficiency and effectiveness in controlling the growth of cancer cells, compared to other organic or more complex molecules or drugs. This study demonstrates that the use of colloidal-based nanostructured materials can possibly reduce the costs of available drugs for the eradication of cancer cells, and that these small nanoparticles can reduce anxieties and medical costs for underprivileged patients. Conceptualization, A.A.A.-K.; methodology, A.A.A.-K.; software, R.W. ; validation, R.W. ; formal analysis, R.W. ; investigation, R.W. ; resources, A.A.A.-K.; data curation, R.W. ; writing--original draft preparation, A.A.A.-K.; writing--review and editing, A.A.A.-K.; visualization, A.A.A.-K.; supervision, A.A.A.-K.; project administration, A.A.A.-K.; funding acquisition, A.A.A.-K. All authors have read and agreed to the published version of the manuscript.