(733e) Biogenic Metallic Nanoparticles. from Micro-Biofactories to a Nanometric Trojan Horse Approach

Antimicrobial resistance to antibiotics (AMR) and cancer and two of the main concerns that the healthcare system should face nowadays. Current drugs and antibiotic treatments are becoming ineffective or have plenty of drawbacks related to misuse and overuse. Therefore, new alternatives are needed, and nanotechnology is rising as a powerful solution over time. How the nanomaterials are created has plenty of influence in their features and applications. Traditional synthesis of nanomaterials, taking knowledge from both physics and chemistry, is subjected to several disadvantages, such as the production of toxic-by-products and harsh conditions, as well as biocompatibility issues. Green nanotechnology is presented as a suitable answer, allowing the generation of nanostructures in a cost-effective and environmentally-friendly approach employing living organisms, such as bacteria, and biomolecules.

In this research, pathogenic bacteria (both antibiotic-resistant and standard strains of Gram-negative -such as Escherichia coli- and Gram-positive -such as Staphylococcus aureus-) and human cells (both cancerous -such as human melanoma and glioblastoma cells, and healthy cell lines, such as astrocytes of fibroblasts-) were used for the synthesis of different metallic -gold (Au), palladium (Pd), platinum (Pt), gold-palladium (AuPd) and gold-platinum (AuPt)- and metalloid -selenium (Se)- nanoparticles with sizes between 5 and 120 nm surrounding by an organic-derived coating. Bacteria and human cells were cultured in the presence of metallic salts under standard conditions, allowing the generation of nanoparticles through natural detoxification processes in a synthetic protocol that is followed using microscopy and spectrophotometric techniques.

After generation, the entities are purified and extensively characterized in terms of composition, morphology and surface chemistry, through techniques such as Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-Ray Photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Raman spectroscopy, in order to elucidate the complex organic-derived coating surrounding the nanoparticles and the metallic/metalloid core. Nanoparticles were then used as antimicrobial and anticancer agents, with effects characterized through growth curve analysis, MTS experiments and colony counting growing assays, not showing significant cytotoxicity towards healthy human cells. In order to understand the mechanisms or action, Reactive Oxygen Species (ROS) analysis was accomplished as well.

The extensive characterization of the nanoparticles showed the presence of organic molecules -such as proteins and lipids- coming from the living organisms, with selenium nanoparticles with sized between 50 and 120 nm. Bacterial tests showed an unusual selective behavior in the antimicrobial effect of bacteria-mediated nanoparticles, showing a dose-dependent inhibition when a bacterial strain X was treated with nanoparticles made by the same bacteria, while poor inhibition was found when different bacteria were used as a target. The nanoparticles showed a robust anticancer effect towards human melanoma and glioblastoma cells while remaining biocompatible towards the healthy cell lines.

On the other hand, noble mono- and bimetallic nanoparticles synthesized by human cells, with sized between 5 and 20 nm, were able to inhibit the growth of cell lines in a similar way that nanoparticles made by bacteria showed, with a certain degree of selectivity, remaining biocompatible. Besides, the production of nanomaterials induced a transition of the cells into a named zombie stage'' or suspension toward the cells was not responding to chemical, physical or temporal degradation.

Therefore, we demonstrated that microbiological agents are successfully used as a synthetic machines for the generation of different metallic/metalloid nanoparticles of different compositions with biomedical properties. Therefore, they are presented as a suitable approach for the synthesis of nanomaterials in a green fashion, overcoming the limitations of traditional nanotechnology, and opening a new field for drug delivery and smart targeting of cancer and antibiotic-resistant infections.