One-pot green synthesis of magnesium oxide nanoparticles using Penicillium chrysogenum melanin pigment and gamma rays with antimicrobial activity against multidrug-resistant microbes.

Graphical abstract Highlights • The optimized fermentation medium was applied for melanin pigment biosynthesis. • MgONPs were synthesized using melanin under the influence of gamma rays. • MgONPs were characterized to evaluate its shape, size, and structure. • MgONPs were wide-range antimicrobial agents towards some pathogenic microbes. Abstract Melanin pigment is well-known as a common photo-protective polymer, insoluble in water. It drews considerable attention for many applications in nanotechnology, and medical fields. Penicillium chrysogenum was employed for the green synthesis of melanin after optimizing the media compositions. A method has been designed that included one-step synthesis of magnesium oxide nanoparticles (MgO NPs) by fungal melanin under the influence of different doses of gamma rays. Antimicrobial activity of MgO NPs was examined against some selected highly pathogenic microbes. The fungal melanin acted simultaneously as a photo-protector of the magnesium atom, and at the same time as a stabilizer towards the uncontrolled free radical attack resulting from gamma rays. Afterwards, gamma rays forced a condensation reaction to occur at room temperature. A proposed reaction mechanism for MgO NPs synthesis was discussed. MgO NPs were characterized and structurally identified by UV–Vis., XRD, DLS, TEM and FTIR. Results obtained from DLS and XRD with TEM images determined the mean diameter as 10.28 nm. In addition, MgO NPs were found to be promising antimicrobial agents against' Enterococcus faecalis, Candida albicans , and Klebsiella pneumoniae having activity of 22.0, 20.0, and 20.0 mm ZOI, respectively. Based on the capability of MgO NPs as effective antimicrobial agents, they possess a potential role – in different applications such as biomedicine, food control, pharmaceutics, and cosmetics. [ABSTRACT FROM AUTHOR]