The emergence of multidrug-resistant (MDR) strains of bacteria and the lack of a novel class of antibiotics has become a global health concern. Pseudomonas aeruginosa is one common MDR bacteria responsible for nosocomial infections and related mortality worldwide. It has developed resistance against commonly available antibiotics and is in the WHO's priority list of bacteria for which new antibiotics are desperately needed. Currently there is a growing interest in developing metal and non-metal-based nanoparticles to target multidrug-resistant bacteria. The objective of this study is to evaluate the efficacy of a novel nanocomposite of two non-traditional antimicrobials: a metal (Ga-III) and a non-metal (chitosan nanoparticle) against P. aeruginosa. It was hypothesized that Gallium (III) nitrate in combination with hydrothermally-treated chitosan biopolymer, which has been widely studied for wound-healing applications, will exhibit synergistic antibacterial activity due to increased modes of action . The Ga(III) nitrate is an FDA approved drug that is used to lower blood levels of calcium in some cancer patients. The drug has been under clinical trials as an antimicrobial agent due to its Iron(III) mimicking property. The chitosan-gallium nanocomposite was synthesized using hydrothermal treatment in acidic conditions. Particle size, surface charge, optical properties, and chemical interactions between Ga (III) and chitosan were studied using Dynamic Light Scattering (DLS), FT-IR, UV-VIS and Fluorescence techniques. Microplate Alamar Blue Assay, Colony Forming Unit assay and Crystal Violet biofilm inhibition assay were conducted to study the antibacterial and antibiofilm properties of the nanocomposite in aqueous suspension (pH 5.7). UV-Visible and fluorescence spectra suggested the formation of optically-active chitosan-gallium nanocomposite, exhibiting broad absorption band (~290-325 nm) and emission at 422 nm. FTIR study confirmed the depolymerization of chitosan and gallium complexation through primary amine groups of chitosan. DLS analysis showed that primary particles have hydrodynamic diameter of 141 nm and average zeta potential of +46 mV at pH 5.7. Microplate alamar blue assay revealed the MIC of the composite to be 32 µg/ml while CFU assay determined the MBC to be 128 µg/ml against P.aeruginosa. Compared to the controls chitosan and gallium nitrate, the chitosan-gallium nanocomposite showed enhanced antibacterial efficacy. Furthermore, there was 21.5% inhibition of biofilm formation at 8 µg/ml of the composite. These preliminary findings suggest the potential of chitosan-gallium nanocomposite as an effective antibacterial agent against P.aeruginosa infections.


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Graduation Date





Santra, Swadeshmukul


Master of Science (M.S.)


College of Medicine


Burnett School of Biomedical Sciences

Degree Program





CFE0009098; DP0026431





Release Date

February 2023

Length of Campus-only Access

1 year

Access Status

Masters Thesis (Open Access)