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

Narintorn Rattanata,1 Sompong Klaynongsruang,1 Chanvit Leelayuwat,2 Temduang Limpaiboon,2 Aroonlug Lulitanond,2 Patcharee Boonsiri,3 Sirinart Chio-Srichan,4 Siriwat Soontaranon,4 Supagorn Rugmai,4 Jureerut Daduang2 1Department of Biochemistry, Faculty of Science, 2Centre for Research and Development of Medical Diagnostic Laboratories, Faculty of Associated Medical Sciences, 3Department of Biochemistry, Faculty of Medicine, Khon Kaen University, Khon Kaen, 4Synchrotron Light Research Institute (Public Organization), Nakhon Ratchasima, Thailand 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)&nbsp

Nanotechnology Applications to Improve Solubility of Bioactive Constituents of Foods for Health-Promoting Purposes

Foods-derived multifunctional compounds, such as carotenoids, vitamins, phytosterols, polyunsaturated lipids, curcuminoids, flavonoids and polyphenols, in addition to the basic nutritional value, own extra health benefits and are considered \u201cpharmaceutical-grade nutrients\u201d better known as \u201dnutraceuticals\u201d. Similarly, phytochemicals from plants, characterized by analogous chemical structures, can be considered \u201cpharmaceutical-grade molecules\u201d. They could provide both diseases preventive actions and remarkable therapeutic benefits but, the efforts for identifying their mode of action and for applying them into food industry with health-promoting purposes, are often unsuccessful. Solubility is essential for a good absorption in the gastrointestinal tract and to achieve the systemic concentration necessary for an effective therapeutic activity, but the majority of these compounds are water-insoluble. Consequently, when ingested, they encounter many difficulties in crossing the diverse barriers to reach the bloodstream and to distribute to cells and tissues. Their absorption at gastric or intestinal level is troubled and in addition, they suffer from early degradation or fast metabolism, so rarely they manage to reach the site of action in therapeutically effective concentration and their clinical applications result strongly limited. Toxic excipients and harmful solubilizing agents were and are extensively used for solubilizing and delivering non-soluble bioactive chemicals (BACs) despite the resulting unpleasant side effects complained of by patients. During last decades, several new techniques, often resorting to nanotechnology, aiming at enhancing BACs solubility, at solving their pharmacokinetics drawbacks, at avoiding their early inactivation or fast metabolism, have been developed. On this background, the following chapter provides an overview concerning nanotechnology contribute and its technological advancements in \u201cmanufacturing\u201d nutraceuticals and phytochemicals in more bioavailable nanoparticles. In addition, it is reviewed the involvement of nanoscience in developing and enhancing food-grade solid nanosized materials to be used as BACs \u201ccontainers\u201d and \u201cvehicles\u201d either for their safe and effective oral administration, in the frame of medical treatments, or for achieving smart food ingredients to improve the quality and shelf life of nourishments