The effect of size control of Gold Nanoparticles Stabilized with α-cyclodextrin and β-cyclodextrin and their antibacterial activities

This research aims to control gold nanoparticles (AuNPs) size by monitoring the relationship between pH stabilizer and Au (III) concentration on the resulting AuNPs. α-cyclodextrin (α-CDs) and β-cyclodextrin (β-CDs) were used as stabilizers for AuNPs that had been reduced by ortho-hydroxybenzoic acid through the one-pot synthesis method. Based on the optimization of CDs pH and Au3+ concentration, the optimal condition for AuNPs with α-cyclodextrin (AuNPs-αCDs) were at pH 11 and Au3+ concentration of 180 ppm, while AuNPs with β-cyclodextrin (AuNPs-βCDs) were at pH 6 and Au3+ concentration of 180 ppm. The results of the dynamic light scattering (DLS) analysis showed that AuNPs-αCDs and AuNPs-βCDs had smaller sizes (12.89 and 13.10 nm, respectively) compared to those without CDs (AuNPs-ortho), which was 29.57 nm. The results of X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), Dynamic Light Scattering (DLS), zeta potential, and stability test results show that AuNPs-αCDs had a smaller size, higher crystallinity, and better stability than AuNPs-βCDs. AuNPs-αCDs performed better as gram-negative antibacterial (Escherichia coli and Pseudomonas aeruginosa) than AuNPs-β-CDs.