Multifunctional chitosan nanoparticles: Zn ²⁺ adsorption, antimicrobial activity, and promotion of aquatic health

Chitosan nanoparticles (CSNPs) are one of the versatile materials that has potential applications in multidomains. However, these diverse applications are not seen in CSNPs produced from a single source. Owing to the above, in this study, we synthesized CSNPs using the ionotropic gelation method and characterized them with UV–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques for multi-application investigations. SEM and TEM analyses confirmed the spherical shape of the produced CSNPs with their size ranging from 10 to 40 nm. CSNPs were utilized for Zn 2+ ion adsorption from aqueous solutions, optimized using response surface methodology. Optimal reaction conditions were pH 7, 60 min of contact time, and 100 mg/L initial concentration, and a loading capacity of 156.2 mg/g was achieved. The model was significant with p -value <0.0001 and lack-of-fit >0.1. CSNPs exhibited antimicrobial activity with zones of inhibition of 25 mm for Escherichia coli and 24 mm for Staphylococcus aureus . Feeding trials with CSNP-supplemented diets in tilapia showed enhanced growth, reduced mortality, and improved red blood cell and white blood cell counts. These findings demonstrate the multi-functional potential of CSNPs prepared from one source, highlighting their applicability in sustainable practice.