The effect of size control of Gold Nanoparticles Stabilized with -cyclodextrin and -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. alpha-cyclodextrin (alpha-CDs) and beta-cyclodextrin (beta-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 a-cyclodextrin (AuNPs-alpha CDs) were at pH 11 and Au3+ concentration of 180 ppm, while AuNPs with beta-cyclodextrin (AuNPs-beta CDs) were at pH 6 and Au3+ concentration of 180 ppm. The results of the dynamic light scattering (DLS) analysis showed that AuNPs-alpha CDs and AuNPs-beta CDs 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-alpha CDs had a smaller size, higher crystallinity, and better stability than AuNPs-beta CDs. AuNPs-alpha CDs performed better as gram-negative antibacterial (Escherichia coli and Pseudomonas aeruginosa) than AuNPs-beta-CDs.