Gallic acid conjugated with gold nanoparticles: antibacterial activity and mechanism of action on foodborne pathogens

Abstract

Foodborne pathogens, including Plesiomonas shigelloides and Shigella flexneri B, are the major cause of diarrheal endemics worldwide. Antibiotic drug resistance is increasing. Therefore, bioactive compounds with antibacterial activity, such as gallic acid (GA), are needed. Gold nanoparticles (AuNPs) are used as drug delivery agents. This study aimed to conjugate and characterize AuNP–GA and to evaluate the antibacterial activity. AuNP was conjugated with GA, and the core–shell structures were characterized by small-angle X-ray scattering and transmission electron microscopy. Antibacterial activity of AuNP–GA against P. shigelloides and S. flexneri B was evaluated by well diffusion method. AuNP–GA bactericidal mechanism was elucidated by Fourier transform infrared microspectroscopic analysis. The results of small-angle X-ray scattering showed that AuNP–GA conjugation was successful. Antibacterial activity of GA against both bacteria was improved by conjugation with AuNP because the minimum inhibitory concentration value of AuNP–GA was significantly decreased (P<0.0001) compared to that of GA. Fourier transform infrared analysis revealed that AuNP–GA resulted in alterations of lipids, proteins, and nucleic acids at the bacterial cell membrane. Our findings show that AuNP–GA has potential for further application in biomedical sciences.

Keywords:

• gold nanoparticles
• gallic acid
• antibacterial activity
• foodborne bacteria
• small-angle X-ray scattering (SAXS)

Acknowledgments

This work was supported by the Higher Education Research Promotion and National Research University Project of Thailand; Office of the Higher Education Commission, through the Health Cluster (SHeP-GMS), Khon Kaen University; and the Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, Khon Kaen University. The authors would like to thank Doctor Alisa Sandee, Doctor Sakda Daduang, Doctor Ratree Tavichakorntrakool, and Mr Seksit Sungkeeree for their assistance. This work was supported by a research grant from Khon Kaen University (grant number PhD 54208).

Disclosure

The authors report no conflicts of interest in this work.