The Influence of Silver (I) Carboxylate Ligand Structure on Pseudomonas aeruginosa

Name: Kylie E Keller
Majors: Biochemistry and Molecular Biology
Advisors: Dr. Marie Southerland (advisor) and Dr. Sara Martin (second reader)

The bacterial lung infections occurring in Cystic Fibrosis (CF) patients contain various multi-drug resistant (MDR) bacterial strains, which are derived from the misuse of antibiotics and ultimately make the resulting infection difficult to treat. To address the rise of these MDR bacteria, like Pseudomonas aeruginosa, the objective of this research is to study a collection of silver (I) carboxylate complexes that have antimicrobial activity and evaluate their antimicrobial efficiency. Silver (I) carboxylate derivatives were synthesized and investigated through the application of infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (¹H NMR), and antimicrobial assays using PA01. ¹H NMR characterized each newly synthesized silver (I) carboxylate by the presence of aromatic protons between 6.5 to 8.0 ppm and the absence of carboxylic acid protons typically found between 10 to 13 ppm for all silver (I) carboxylate products. IR further confirmed synthesis of silver (I) 3-bromobenzoate and silver (I) 4-bromobenzoate by the loss of broad carboxylic proton peaks and lowered peak intensities of carbonyl groups in the 1700 cm^-1 region corresponding to the structure of carboxylates. Zone of inhibition by Kirby-Bauer disk diffusion assays further determined the silver (I) ion association with each silver (I) carboxylate as silver (I) benzoate and its brominated derivatives have various levels of antimicrobial activity against PA01 when compared to negative controls. Silver (I) 4-bromobenzoate showed the highest level of antimicrobial activity against PA01 with an average zone of inhibition measurement of 13 millimeters (SD = 1.41 mm). Biological assays also defined the structure-activity relationship (SAR) of bromine substituent placement on silver (I) ion coordinated carboxylates: the electronegative bromine placements para to the carboxylate group allow for greater antimicrobial effect against PA01. With further investigation, these complexes offer the possibility in providing an alternative medicinal treatment to combat bacterial MDR strains.

Posted in Comments Enabled, Independent Study, Symposium 2022 on April 26, 2022.

2 responses to “The Influence of Silver (I) Carboxylate Ligand Structure on Pseudomonas aeruginosa”

1. Nancy keller says:

   April 28, 2022 at 6:53 pm

   Awesome work Kylie! So glad to see you doing research on cures for health issues! May your passion continue for the years to come!

2. David Rauth says:

   April 28, 2022 at 10:14 pm

   I am glad to see the results of your work encourages further investigation that the caboxylate complexes to improve medical treatments to combat the material MDR strains.

   Good work, Kylie. Nice that you’ve obtain a positive outcome that might help obtain a better treatment procedure to fight the bacterial strains.