Biogenic nanoparticles: Synthesis, stability and biocompatibility mediated by proteins of Pseudomonas aeruginosa

The development of environmental friendly new procedures for the synthesis of metallic nanoparticles is one of the main objectives of nanotechnology. Plants, algae, fungi and bacteria for the production of nanomaterials are viable alternatives due to their low cost, the absence of toxic waste production and their highly energy efficiency. It is also known that biosynthesized silver nanoparticles (AgNPs) show higher biocompatibility compared to the chemically-synthesized ones. In previous results, biosynthesized AgNPs were obtained from the supernatant of Pseudomonas aeruginosa, and they showed a bigger antimicrobial activity against different bacterial species compared to the chemically-synthesized ones. The aim of this work was to analyze the capping of biosynthesized AgNPs using techniques such as transmission electron microscopy (TEM), infrared spectroscopy (IR), and protein identification through mass spectrometry (MS) in order to identify the compounds responsible for their formation, stability and biocompatibility. The TEM images showed that AgNPs were surrounded by an irregular coverage. The IR spectrum showed that this coverage was composed of carbohydrates and/or proteins. Different proteins were identified in the capping associated to biosynthesized AgNPs. Some proteins seem to be important for their formation (Alkyl hydroperoxide reductase and Azurin) and stabilization (Outer membrane protein OprG and Glycine zipper 2 T M domain-containing protein). The proteins identified with the capability to interact with some biomolecules can be responsible for the biocompatibility and may be responsible for the bigger antimicrobial activity than AgNPs have previously shown. These results are pioneers in the identification of proteins in the capping of biosynthesized AgNPs.