Background and aim: Bimetallic silver/gold nanosystems are expected to significantly improve therapeutic efficacy compared to their monometallic counterparts by maintaining the general biocompatibility of gold nanoparticles (AuNPs) while, at the same time, decreasing the relatively high toxicity of silver nanoparticles (AgNPs) toward healthy human cells. Thus, the aim of this research was to establish a highly reproducible one-pot green synthesis of colloidal AuNPs and bimetallic Ag/Au alloy nanoparticles (NPs; Ag/AuNPs) using starch as reducing and capping agent. Methods: The optical properties, high reproducibility, stability and particle size distribution of the colloidal NPs were analyzed by ultraviolet (UV)-visible spectroscopy, dynamic light scattering (DLS) and ζ-potential. The presence of starch as capping agent was determined by Fourier transform infrared (FT-IR) spectroscopy. The structural properties were studied by X-ray diffraction (XRD). Transmission electron microscopy (TEM) imaging was done to determine the morphology and size of the nanostructures. The chemical composition of the nanomaterials was determined by energy-dispersive X-ray spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. To further study the biomedical applications of the synthesized nanostructures, antibacterial studies against multidrug-resistant (MDR) Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) were conducted. In addition, the NPs were added to the growth media of human dermal fibroblast (HDF) and human melanoma cells to show their cytocompatibility and cytotoxicity, respectively, over a 3-day experiment. Results: UV-visible spectroscopy confirmed the highly reproducible green synthesis of colloidal AuNPs and Ag/AuNPs. The NPs showed a face-centered cubic crystal structure and an icosahedral shape with mean particle sizes of 28.5 and 9.7 nm for AuNPs and Ag/AuNPs, respectively. The antibacterial studies of the NPs against antibiotic-resistant bacterial strains presented a dose-dependent antimicrobial behavior. Furthermore, the NPs showed cytocompatibility towards HDF, but a dose-dependent anticancer effect was found when human melanoma cells were grown in presence of different NP concentrations for 72 hours. Conclusion: In this study, mono-and bimetallic NPs were synthesized for the first time using a highly reproducible, environmentally friendly, cost-effective and quick method and were successfully characterized and tested for several anti-infection and anticancer biomedical applications.

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Bimetallic nanoparticles, or BMNPs, are nanosized structures that are of growing interest in biomedical applications. Although their production shares aspects with physicochemical approaches for the synthesis of their monometallic counterparts, they can show a large variety of new properties and applications as a consequence of the synergetic effect between the two components. These applications can be as diverse as antibacterial treatments or anticancer or biological imaging approaches, as well as drug delivery. Nevertheless, the utilization of BMNPs in such fields has received limited attention because of the severe lack of knowledge and concerns regarding the use of other nanomaterials, such as stability and biodegradability over time, tendency to form clusters, chemical reactivity, and biocompatibility. In this review, a close look at bimetallic systems is presented, focusing on their biomedical applications as antibacterial, anticancer, drug delivery and imaging agents, showing significant enhancement of their features compared to their monometallic counterparts and other current used nanomaterials for biomedical applications. Index1. Nanotechnology for biomedical applications. 1.1. Nanotechnology and nanomedicine. The born of a new era. 1.2. The use of metallic nanoparticles in nanomedicine. 2. Bimetallic nanoparticles. A step further. 2.1. Synthesis of bimetallic nanoparticles 2.1.1. Physicochemical approaches 2.1.2. Green chemistry approaches 2.2. Bimetallic nanoparticles as biomedical tools 2.2.1.