Metal colloids in 2 propanol using nanoparticles (NPs) of copper, nickel and cobalt were prepared by Chemical Liquid Deposition (CLD) method. The resulting colloidal dispersions were characterized by Transmission Electron Microscopy (TEM). The colloids were supported in chitosan. Then, microbiological assays were performed using E. coli and S. aureus in order to determine the bactericide/bacteriostatic activity of nanoparticles (NPs) trapped or chelated with chitosan. Finally, the toxicity of the metal colloids Cu, Ni and Co was tested. Bio-assays were conducted in three different animal species. First of all on earth warms (Eisenia foetida) to evaluate the toxicity and the biocompatibility of chitosan in lactic acid (1% and 0.5%). Secondly bio-assay done in fishes (rainbow trout), the liver toxicity of NPs in vivo was evaluated. Finally, a bio-assay was conducted in Sprange-Dawley rats of 100g weight, which were injected intraperitoneally with different solutions of chitosan metal colloids. Then, the minimum and maximum concentration were determined for copper, nickel and cobalt. The purpose of the use of chitosan was acting as a carrier for some magnetic NPs, which toxicity would allow to obtain new polymeric materials with potential applications as magnet future drugs carrier.

Lactic acid bacteria (LAB), obtained from rainbow trout (Oncorhynchus mykiss) intestine, were cultured in MRS medium and probiotic candidates. Concurrently, producers of elemental selenium nanoparticles (Se⁰Nps) were selected. Probiotic candidates were subjected to morphological characterization and the following tests: antibacterial activity, antibiotic susceptibility, hemolytic activity, catalase, hydrophobicity, viability at low pH, and tolerance to bile salts. Two LAB strains (S4 and S14) satisfied the characteristics of potential probiotics, but only strain S14 reduced selenite to biosynthesize Se⁰Nps. S14 strain was identified, by 16S rDNA analysis, as Lactiplantibacillus plantarum. Electron microscopy showed Se⁰Nps on the surface of S14 cells. Rainbow trout diet was supplemented (10⁸ CFU g⁻¹ feed) with Se⁰Nps-enriched L. plantarum S14 (LABS14-Se⁰Nps) or L. plantarum S14 alone (LABS14) for 30 days. At days 0, 15, and 30, samples (blood, liver, and dorsal muscle) were obtained from both groups, plus controls lacking diet supplementation. Fish receiving LABS14-Se⁰Nps for 30 days improved respiratory burst and plasmatic lysozyme, (innate immune response) and glutathione peroxidase (GPX) (oxidative status) activities and productive parameters when compared to controls. The same parameters also improved when compared to fish receiving LABS14, but significant only for plasmatic and muscle GPX. Therefore, Se⁰Nps-enriched L. plantarum S14 may be a promising alternative for rainbow trout nutritional supplementation.