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.

The rise of nanotechnology has brought to the world a new potential and broader perspective of what humanity can achieve through material manipulation at the nanoscale. As a consequence, the use of different nanomaterials has revolutionized both the industrial and biomedical worlds. Metallic and metal-oxide nanostructures have shown great potential due to their high surface to volume ratio and high reactivity. Among them, zinc oxide (ZnO) has revealed wider applicability, including in nanomedicine, where ZnO nanomaterials have shown great potential leading to effective interactions with biological membranes and exhibiting antibacterial and/or anticancer behaviors. However, consistent with several other nanostructures, the synthesis of ZnO nanomaterials is not devoid of drawbacks, such as the production of harmful and toxic byproducts, the use of toxic reagents, the employment of expensive instruments, and the lack of biocompatibility, all of which need to be overcome before extensive use. As a solution, green nanotechnology has allowed the production of ZnO nanostructures using environmentally friendly and cost-effective methods, which are based on the use of living organisms, natural biomolecules and waste materials. Once produced, green-synthesized ZnO nanoparticles have shown enhancements in terms of their cytocompatibility and biomedical properties compared to their traditionally produced counterparts, becoming excellent antibacterial or anticancer agents. These ZnO nanoparticles have also proven to be valuable materials in combination with wound healing processes and biosensing elements in order to trace small amounts of biomarkers associated with different diseases. As a consequence, there is a synergy between green nanotechnology and ZnO nanomaterials, which is leading to an exciting flourishment in the field, presenting a wide variety of biomedical applications for these nanostructures. This review compares and contrasts recent approaches and examples of the use of green-synthesized ZnO nanomaterials with traditionally synthesized structures, demonstrating a remarkable potential for their use as a powerful biomedical agent.

Bacterial infections and cancer are two of the most significant concerns that the current healthcare system should tackle nowadays. Green nanotechnology is presented as a feasible solution that is able to produce materials with significant anticancer and antibacterial activity, while overcoming the main limitations of traditional synthesis. In the present work, orange, lemon and lime extracts were used as both reducing and capping agents for the green synthesis of tellurium nanoparticles (TeNPs) using a microwave-assisted reaction. TeNPs showed a uniform size distribution, and rod- and cubic-shapes, and were extensively characterized in terms of morphology, structure and composition using TEM, SEM, XPS, XRD, FTIR and EDX analysis. TeNPs showed an important antibacterial activity against both Gram-negative and -positive bacteria in a range concentrations from 5 to 50 μg mL⁻¹ over a 24-hour time period. Besides, nanoparticles showed an anticancer effect towards human melanoma cells over 48 hours at concentrations up to 50 μg mL⁻¹. Moreover, the Te nanostructures showed no significant cytotoxic effect towards human dermal fibroblast at concentrations up to 50 μg mL⁻¹. Therefore, we present an environmentally-friendly and cost-effective synthesis of TeNPs using only fruit juices and showing enhanced and desirable biomedical properties towards both infectious diseases and cancer.

The rise of antimicrobial resistance to antibiotics (AMR) as a healthcare crisis has led to a tremendous social and economic impact, whose damage poses a significant threat to future generations. Current treatments either are less effective or result in further acquired resistance. At the same time, several new antimicrobial discovery approaches are expensive, slow, and relatively poorly equipped for translation into the clinical world. Therefore, the use of nanomaterials is presented as a suitable solution. In particular, this review discusses selenium nanoparticles (SeNPs) as one of the most promising therapeutic agents based in the nanoscale to treat infections effectively. This work summarizes the latest advances in the synthesis of SeNPs and their progress as antimicrobial agents using traditional and biogenic approaches. While physiochemical methods produce consistent nanostructures, along with shortened processing procedures and potential for functionalization of designs, green or biogenic synthesis represents a quick, inexpensive, efficient, and eco-friendly approach with more promise for tunability and versatility. In the end, the clinical translation of SeNPs faces various obstacles, including uncertain in vivo safety profiles and mechanisms of action and unclear regulatory frameworks. Nonetheless, the promise possessed by these metalloid nanostructures, along with other nanoparticles in treating bacterial infections and slowing down the AMR crisis, are worth exploring.