###### Abstract
Another important property of this type of bimetallic nanomaterials is their ability for facilitated clearance from the body. [PERSON] et al. have shown self-degradation of AuFe BMNPs over time and a significant reduction of their long-term accumulation in vivo compared to monometallic gold and iron oxide NPs, thus proving their utility as safe multifunctional nanomedicines [12]. In addition, iron oxide nanoparticles have been shown to possess intrinsic catalytic activity by mimicking natural innate peroxididases [16]. Such activity contributes and expands their biomedical application and could even supplement the properties and therapeutic application of bimetallic nanosystems that contain them. Furthermore, the facilitated functionalization of AuFe BMNPs was reported by different research groups [15; 17]. These findings were recently supplemented with studies showing the use of Au-iron oxide magnetic NPs for the development of self-assembly systems that serve as nanoplatforms for biologically active molecules, such as oxytocin and insulin, that are paving the way for new sustainable green methods for BMNP functionalization by improving their further application as drug carriers [18]. The structure and electronic state of AuFe nanoparticles vary significantly depending on the methods used for their synthesis [19; 20], which makes it possible to control the properties of the synthesized systems. This stimulates the development of new methods for the synthesis of AuFe systems and a comprehensive study of their physicochemical properties. A potential candidate for being an efficient method of the production of BMNPs is metal-vapor synthesis (MVS). It enables the formation of bimetallic nanocomplexes \"in situ\" under a vacuum or an inert atmosphere in the presence of a stabilizing organic solvent, even for highly reactive systems such as iron NPs, to obtain bimetallic materials whose synthesis is impossible or difficult to implement using traditional methods, due to the multistep process and the high cost of metal complex precursors [21]. This method can be carried out in a technologically closed cycle and is environmentally friendly. Classical chemotherapeutics are associated with detrimental influences on normal tissues, resulting in various side effects. Other common disadvantages limiting the effectiveness of some chemotherapeutic agents are low solubility and a short half-life. A typical example is methotrexate (MTX)--an antitumor and anti-inflammatory drug applied in the treatment of certain tumors, rheumatoid arthritis and other inflammatory disorders. Renal excretion of administered MTX has been shown to account for up to 90% of the drug dose [22]. Therefore, the conjugation of BMNPs with MTX has been suggested to reduce minimum effective dosages, allow specific drug targeting to eliminate adverse effects, improve the drug bioavailability and half-life and avoid the need for repetitive treatment. The efficacy of gold-iron alloy nanoparticles in hyperthermia-controlled MTX release has been demonstrated [23], as well as the potential of gold-iron oxide magnetic nanoparticles for specific targeting of doxorubicin to cancer cells and hyperthermia treatment [24], including the application of theranostics in oral cancer [15]. In this study, for the first time, bimetallic AuFe nanoparticles and their conjugates with MTX were effectively obtained with an environmentally safe metal-vapor synthesis method, and their potential for biomedical applications was proven. Our experiments included detailed physicochemical evaluations of the obtained bimetallic drug nanocarriers and multilateral analyses of BMNP-MTX biological activities encompassing antitumor, antibacterial and immunological properties.