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Suhaili Shamsi,1 Ahmad Ashraful Hadi Abdul Ghafor,2 Nur Hazwani Norjoshukrudin,1 Ida May Jen Ng,1 Siti Nur Sharmila Abdullah,1 Seri Narti Edayu Sarchio,2 Faizah Md Yasin,3,4 Shafinaz Abd Gani,1 Mohd Nasir Mohd Desa2 1Laboratory of Animal Biochemistry and Biotechnology, Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor, 43400, Malaysia; 2Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Selangor, 43400, Malaysia; 3Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor, 43400, Malaysia; 4Institute of Nanoscience and Nanotechnology (ION2), Universiti Putra Malaysia, Serdang, Selangor, 43400, MalaysiaCorrespondence: Suhaili Shamsi, Laboratory of Animal Biochemistry and Biotechnology, Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor, 43400, Malaysia, Tel +603-9769 7964, Fax +603-9769 7590, Email sh_suhaili@upm.edu.myBackground: The impetuous usage of antibiotics has led to the perpetual rise of methicillin-resistant Staphylococcus aureus (MRSA), which has garnered the interest of potential drug alternatives, including nanomaterials.Purpose: The present study investigates the stability, toxicity, and antibacterial potential of gallic acid-loaded graphene oxide (GAGO) on several MRSA strains.Methods: The stability of a synthesized and characterized GAGO was monitored in different physiological media. The toxicity profile of GAGO was evaluated in 3T3 murine fibroblast cells and the embryonic zebrafish model. The antibacterial activity of GAGO against MRSA, methicillin-susceptible S. aureus (MSSA), and community-acquired MRSA; with or without Panton-valentine leucocidin gene (MRSA-pvl+ and MRSA-pvl-) was investigated through disk diffusion, CFU counting method, time-kill experiment, and high-resolution transmission electron microscopy (HRTEM) observation.Results: A stable GAGO nanocomposite has shown an improved toxicity profile in 3T3 murine fibroblast cells and zebrafish embryos, besides exhibiting normal ROS levels than graphene oxide (GO) and GA (gallic acid). The nanocomposite inhibited the growth of all bacterial strains employed. The effectiveness of the GAGO nanocomposite was comparable to cefoxitin (CFX), at ≥ 150 μg/mL in MRSA and MSSA. GAGO exhibited a significantly delayed response towards MRSA-pvl+ and MRSA-pvl-, with increased inhibition following 8 to 24 h of exposure, while comparable activity to native GA was only achieved at 24 h. Meanwhile, for MRSA and MSSA, GAGO had a comparable activity with native GA and GO as early as 2 h of exposure. HRTEM observation further reveals that GAGO-exposed cells were membrane compromised.Conclusion: In summary, the present study indicates the antibacterial potential of GAGO against MRSA strains, but further study is warranted to understand the mechanism of action of GAGO and its resistance in MRSA strains.Keywords: graphene oxide, gallic acid, nanomaterial, MRSA, toxicity, multidrug resistance

Macluraxanthone was previously reported to have many biological activities, including anti-cholinesterase, anti-oxidant, anti-cancer, anti-malarial and anti-inflammatory effects. The aim of the current study was to further characterise the effect of macluraxanthone on human macrophage, a type of immune cell that has been implicated in the development of various inflammatory diseases. The expression of surface markers and cytokine production by THP-1 human macrophages following treatment with macluraxanthone were investigated. Macluraxanthone was shown to promote polarisation of M1-like pro-inflammatory macrophages by increasing the percentage of macrophages expressing CD86, while decreasing their CD14, CD11b and CD80 expression. However, in the presence of the pro-inflammatory stimulus lipopolysaccharide, macluraxanthone significantly decreased TNF-α and IL-10 cytokine production.

Xanthones are well known for their significant biological activities and can be found in many herbal medicines. These compounds have the ability to regulate various inflammatory activities and signaling pathways in immune cells, especially macrophages. Macrophages are innate immune cells that can either fuel or dampen an inflammatory response depending on their activation states and play an active role in the development of inflammatory diseases such as atherosclerosis, arthritis, cancer, and diabetes. Many traditional medicines used as a remedy for these diseases contain xanthones, and their bioactivities may be partially attributed to their ability in regulating macrophage responses. In this review, we discuss the in vitro and in vivo findings on the effects of xanthones on different macrophage immune functions including nitric oxide and cytokine production, migration, polarization, and phagocytosis. Their specific modes of action are highlighted whenever known. We also discuss the potential and challenges in using xanthones as a therapeutic option in various inflammatory diseases. It is hoped that this review can pave the way for future research that focuses on developing xanthones as specific macrophage-targeted therapeutics.