Formulation of Gold (Au) Nanoparticles Serum Containing Sunflower (Helianthus annuus L.) seed extract from Indonesia as an antibacterial: in vitro and skin irritation assessments

Serum is a cosmetic preparation containing active ingredients and is widely used to maintain skin health. Sunflower (Helianthus annuus L.) seed extract contains flavonoid compounds that can reduce and stabilize gold ions into nanoparticles, offering a green synthesis approach with potential antibacterial applications. This study aimed to formulate a gold nanoparticle serum synthesized using sunflower seed extract and to evaluate its physicochemical characteristics and antibacterial activity. Sunflower Seed Extract (SFSE) was obtained through maceration using 96% ethanol. Gold nanoparticles derived from the SFSE were synthesized by combining 70% ethanolic SFSE with 1400 μL of chloroauric acid (HAuCl₄) and 50 μL of polyvinyl alcohol, following a modified standard protocol. Three serum formulations (F1, F2, and F3) were then produced by incorporating SFSE at varying concentrations: 1,525% for F1, 1,650% for F2, and 1,775% for F3 into a serum base consisting of carbopol, triethylamine, propylene glycol, propylparaben, Na benzoate, glycerin, and EDTA. Each formulation was assessed for organoleptic characteristics, pH, viscosity, spreadability, homogeneity, and irritation. Antibacterial activity was examined against Staphylococcus aureus ATCC 25923 using the disc diffusion technique. The characterization of the gold nanoparticles showed absorbance values of 0.948, 1.049, and 1.422 at wavelengths of 493, 521, and 559 nm, respectively. The particle sizes obtained for each formulation were 276.2 nm, 661.1 nm, and 897.2 nm. The finalized preparations showed distinct appearances: F1 was purple, F2 was light purple, and F3 was light purple. All exhibited slight viscosity, uniform texture, and pH values ranging from 5.54 to 5.77. All formulations demonstrated inhibitory activity against Staphylococcus aureus, with F3 producing the strongest response, as reflected by an inhibition zone measuring 12.6 mm. The results indicated that the gold nanoparticles serum exhibits excellent stability, significant antibacterial activity, and is safe for topical application, with no irritant effects observed during skin irritation assessments.