Green-fabricated MgO nanoparticles: A potent antimicrobial and anticancer agent

2.1 Green synthesis of MgO nanoparticles by garlic extract

Garlic cloves acquired locally were peeled, washed in deionized water, chopped, and air dried. A grinder pulverizes whole cloves into a powder. The maceration procedure was used for the extraction. Garlic powder (15 g) was steeped in 300 ml of deionized water for 24 h with continuous stirring. Finally, filter paper with a pore size of 0.2 m was used to remove any remaining solids from the extract before it was kept at 4 °C for later use.

A solution was produced by adding 1 g of magnesium nitrate (Mg(NO₃)₂·6H₂O) (Sigma-Aldrich, St. Louis, MO, USA) with 20 ml of garlic extract, followed by stirring for 30 min at room temperature. Following this, a 5 ml of sodium hydroxide solution (0.2 M) was slowly added to the amalgam until a visible precipitate was formed. The precipitate was then subjected to multiple washes with deionized water and subsequently dried at a temperature of 60 °C for overnight. Following this, the sample was subjected to a calcination procedure at a temperature of 500 °C for a period of 2 h to get fine powder of MgO nanoparticles. Fig. 1 illustrates the green process of synthesizing MgO nanoparticles using garlic extract.

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Fig. 1

Illustration of green process MgO nanoparticles synthesis using garlic extract.

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2.2 Characterization

The structural properties of the as-prepared MgO nanoparticles were analyzed by X-ray diffraction (XRD) (PanAlytical X'pert Pro, Malvern Instruments) employing CuK radiation (λ = 1.5406). Field emission scanning electron microscopy (FESEM) (JSM-7600F, JEOL, Tokyo, Japan), transmission electron microscopy (FETEM) (JEM-2100, JEOL), and energy dispersive X-ray spectroscopy (EDX) were used to further investigate the structural characteristics, particle size, and elemental composition of MgO nanoparticles.

2.3 Antimicrobial assay

The antibacterial activity of as-synthesized nanoparticles was evaluated using Staphylococcus epidermidis (ATCC-14990, gram-positive bacteria), Escherichia coli (ATCC-BAA-2471, gram-negative bacteria), and Candida albicans (ATCC-10231, fungal pathogen). Slants of nutritional agar broth were inoculated with 0.5 McFarland (1 × 10⁸ CFU/ml) of bacteria and incubated for 18 h at 37 °C (Zheng et al., 2020). Sabouraud dextrose broth slants were used to cultivate the fungi for 24 h at 30 °C with an inoculum of 2 × 10⁶ PFU/mL. The disc-diffusion assay was used to measure the antimicrobial activity (Azam et al., 2012). Each well was filled with a 50 µl (50 µg) solution of MgO nanoparticles. Streptomycin was used to treat bacteria, while nystatin was used to treat fungus as a positive control (PC). The minimum inhibitory concentrations (MICs) of as-prepared MgO nanoparticles against bacterial and fungal pathogens were determined using the micro-broth dilution technique.

2.4 Cell lines and anticancer assay

The HepG2 and A549 cell lines of human hepatocellular carcinoma and lung carcinoma, respectively, were bought from American Type Cell Culture Collection (ATCC, Manassas, Virginia, USA). Both types of cell lines were cultured in Dulbecco's Modified Eagle Medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 100 U/ml penicillin, and 100 μg/ml streptomycin. The cell culture was sustained within an incubation chamber at a temperature of 37 ^◦C, with a 5% concentration of CO₂. Cells were treated to MgO nanoparticles for 24 h at concentrations ranging from 1 to 200 µg/ml. The MTT test, with appropriate changes, was used to investigate anticancer activity (Ahamed et al., 2021). The 2′ −7′ -dichlorodihydrofluorescein diacetate (H2DCFDA) was used to measure the intracellular concentration of ROS (Ahamed et al., 2021).

2.5 Statistical analysis

The data was analyzed with one-way analysis of variance (ANOVA) and then Dennett's multiple comparison tests. The significance level was set at p < 0.05. Three separate experiments (n = 3) provided the quantitative results displayed as mean ± SD.

3.1 Electron microscopy study

Fig. 2 shows the FESEM characterization of environmental-friendly produced MgO nanoparticles. The typical SEM micrographs of MgO nanoparticles are shown in Fig. 2A and B at varying magnifications. These SEM images reveal that the MgO nanoparticles are about 60 nm in size. The elemental composition was determined using SEM-EDX analysis, and the results showed a stoichiometric amount of Mg (52.36 wt%) and O (47.64 wt%) (Fig. 2C and D). The present research's FESEM characterization data aligns with previously published work (Su et al., 2023; Yousefi et al., 2017).

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Fig. 2

FESEM micrographs of MgO nanoparticles of different magnifications (A and B). SEM-EDX spectra (C) and elemental composition (D) of MgO nanoparticles.

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Green-manufactured MgO nanoparticles were further characterized by FETEM and shown in Fig. 3. The findings presented in Fig. 3A indicate that the MgO nanoparticles exhibited an irregular shape and possessed an average diameter of 58 nm, which is consistent with the results obtained from the SEM analysis. The appearance of lattice fringes in the high-resolution TEM image confirmed that MgO had a cubic structure (Chen et al., 2020). As can be seen in Fig. 3B, the MgO cubic structure has a (2 0 0) diffraction plane with a corresponding lattice inter-planar distance of 0.235 nm. TEM-EDX analysis of MgO nanoparticles' elemental composition confirmed the pure presence of the Mg and O. The utilization of a carbon-coated copper grid in TEM resulted in the production of peaks corresponding to carbon and copper, as depicted in Fig. 4.

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Fig. 3

Low-resolution (A) and high-resolution (B) FETEM micrographs of MgO nanoparticles.

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Fig. 4

TEM-EDX spectra of MgO nanoparticles.

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3.2 XRD study

The XRD technique was employed, utilizing CuKα radiation, to investigate the phase-purity and crystallinity of the synthesized MgO nanoparticles. Fig. 5 displays the X-ray diffraction spectra of MgO nanoparticles. The observed peaks at angles 37.23°, 43.13°, 62.50°, 74.94°, and 78.86° correspond to the (1 1 1), (2 0 0), (2 2 0), (3 1 1), and (2 2 2) planes (JCPDS No. 87–0653), indicating the presence of a polycrystalline cubic structure of MgO. The absence of any additional impurity phase in the XRD pattern corroborates the findings of the EDX data. The XRD spectra indicate a high degree of crystallinity in the MgO nanoparticles synthesized through the green method, as evidenced by the presence of intense peaks. The determination of crystal size in the synthesized samples was carried out by utilizing Scherrer's formula (Ahamed et al., 2017) and applying the most prominent peak (2 0 0). Results reveals that the crystal dimensions of MgO nanoparticles were estimated to be approximately 55 nm, which is consistent with the size determined through the utilization of TEM and SEM.

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Fig. 5

XRD pattern of MgO nanoparticles.

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3.3 Antimicrobial study

Green-manufactured MgO nanoparticles have been the subject of increasing research into their antibacterial properties (Abinaya and Kavitha, 2023; Rotti et al., 2023). In this research, MgO nanoparticles created using garlic extract were highly effective against both bacterial and fungal pathogens. Staphylococcus epidermidis (29.6 µg/ml), Escherichia coli (26.8 µg/ml), and the fungal pathogen Candida albicans (17.7 µg/ml) all showed zone of inhibition formation in Fig. 6A. Fig. 6B shows the minimal inhibitory concentration (MIC) of MgO nanoparticles against specific microorganisms. The S. epidermidis, E. coli, and C. albicans all had MICs of 19.3 µg/ml, 22.7 µg/ml, and 27.4 µg/ml, respectively. These findings imply that the MgO nanoparticles produced in a sustainable manner have potent antimicrobial and bacteriostatic properties. Rotti et al. demonstrated similar antibacterial activity in plant extract mediated manufactured MgO nanoparticles against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, supporting the current findings (Rotti et al., 2023). The bactericidal and fungicidal activities of MgO nanoparticles against a variety of common pathogenic bacteria and yeasts were also reported by Nguyen and co-workers (Nguyen et al., 2018).

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Fig. 6

Antimicrobial effects of MgO nanoparticles. Zone of inhibition (A) and minimum inhibitory concentration. SE: Staphylococcus epidermidis, EC: Escherichia coli, CA: Candida albicans, PC: positive control.

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3.4 Anticancer study

Research on the effectiveness of MgO nanoparticles as an anticancer agent is gaining interest (Akhtar et al., 2018; Krishnamoorthy et al., 2012b). Human liver (HeG2) and lung (A549) cancer cells were used to test the anticancer effect of MgO nanoparticles generated in an eco-friendly manner. Anticancer activity was measured using the MTT test after cancer cells were exposed to MgO nanoparticles at concentrations ranging from 1 to 100 µg/ml for 24 h. In both HepG2 and A549 cancer cells, MgO nanoparticles exhibited dose-dependent cytotoxicity, as shown in Fig. 7. MgO nanoparticles had IC₅₀ values of 18.6 g/ml and 20.3 g/ml against HepG2 and A549 cancer cells, respectively. Potent anticancer activity of MgO nanoparticles may have been facilitated by garlic phytochemicals during the synthesis. Previous research has shown that the phytochemicals in garlic have strong anticancer effects on several different types of cancer, including those of the lung, liver, breast, and skin (Mondal et al., 2022). Nanocomposite ZnO/RGO produced from garlic extract showed anticancer action in human colon cancer HC116 and breast cancer MCF7 cells, as we reported in our prior study (Ahamed et al., 2022b). The ability of MgO nanoparticles to fight cancer has been reported in earlier research. For example, human breast cancer (MCF-7) cells were found to be sensitive to MgO nanoparticles exposure (Amina et al., 2020). Ali et al. recently observed the anticancer effects of Abrus precatorius bark extract manufactured MgO nanoparticles in human melanoma cancer (A375) (Su et al., 2023).

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Fig. 7

Anticancer effects of MgO nanoparticles in human liver (HepG2) and lung (A549) cancer cells. *p < 0.05 vs. control.

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It has been claimed that oxidative stress may play a part in the treatment of cancer. Due to the use of numerous medications, ROS-mediated oxidative stress is a frequent occurrence in cancer treatment. The ROS-generating ability of MgO nanoparticles has been also observed in earlier research. Previous studies have shown that the depletion of antioxidants can lead to the damage of tumor cells, especially when used in conjunction with treatments that induce the generation of ROS. This study aimed to investigate the impact of MgO nanoparticles on the oxidative stress response in cancer cells (HepG2 and A549 cells). The cells were exposed to varying concentrations (1–100 µg/ml) of MgO nanoparticles for 24 h. The oxidative stress response (ROS level) was then measured. The results of Fig. 8 indicate that there is a positive correlation between the concentration of MgO nanoparticles and the level of ROS in cancer cells. A recent study conducted by Pugazhendhi et al. also revealed that the induction of apoptosis in A549 cells was observed upon exposure to MgO nanoparticles, which was attributed to the accumulation of intracellular ROS (Pugazhendhi et al., 2019).

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Fig. 8

ROS generation of MgO nanoparticles in human liver (HepG2) and lung (A549) cancer cells. *p < 0.05 vs. control.

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