22 Aug 2015

Antibacterial Reactivity of Ag(I) Cyanoximate Complexes

Lab Experiment

Submitted by Kari Young, Centre College
Categories
Description: 

In this experiment, students will synthesize and characterize one of three Ag(I) cyanoximate complexes as potential antimicrobial agents for use in dental implants. This experiment combines simple ligand synthesis, metalation and characterization, and a biomedical application. The complexes are both air and light stable. Students apply the Kirby-Bauer disk diffusion test, a common microbiology assay, to determine the antibacterial properties of their complexes. Students will also perform a simple cost analysis as part of the evaluation of the complexes.  This experiment was designed during the June 2015 “Improving Inorganic Chemistry Pedagogy” workshop funded by the Associated Colleges of the South.

AttachmentSize
File Student Handout (updated 1-6-2020)169.86 KB
Learning Goals: 

A student should be able to:

  • Prepare one of a series of Ag(I) cyanoximate complexes and perform appropriate characterization of identity and purity
  • Measure antimicrobial activity in a semi-quantitative way using the Kirby-Bauer assay, including design and implementation of appropriate control experiments.
  • Evaluate a series of complexes as potential antimicrobials for dental applications based on the criteria of heat stability, water insolubility, and antibacterial activity.
  • Identify most cost effective complex.
Equipment needs: 

FT-IR spectrometer

NMR spectrometer

Melting point apparatus

Microbiology equipment

Implementation Notes: 

In this experiment, students connect organic synthesis, inorganic synthesis, and applications in microbiology in a multiweek experiment.

 

Students synthesize one of three possible derivatives of a cyanoxime ligand, coordinate Ag(I), and test the antimicrobial properties of their compound. The antimicrobial assay requires supplies not commonly found in a chemistry laboratory, and instructors are encouraged to collaborate with a colleage in microbiology.

 

This experiment has been tested several times since it was first developed in 2015. Additional notes were added in January 2020. We welcome others in the VIPEr community to help us test this experiment. If you do try it, please consider posting your comments or filling out our evalution survey:

 

Time Required: 
Four 3-hour lab sessions
Evaluation
Evaluation Methods: 

We assessed student learning using formal reports, informal reports, and oral presentations. 

Evaluation Results: 

In general, students are able to prepare and characterize the complexes.  IR spectroscopy is especially useful in this lab because 1H NMR spectroscopy is not very diagnostic. One difficulty is removing excess solvent from the ligand, and we recommend using a mechanical vacuum pump after rotovapping. 

Some students are uncomfortable managing the amount of data this project generates when students share data for more than one compound. This project is a good opportunity to discuss using tables effectively.

Additionally, evaluating the "best" complex requires students to weigh a variety of parameters including heat stability and cost in addition to the antimicrobial activity.

Some students are also uncomfortable sharing data with their classmates or using others' data. This project provides a good opportunity to talk about the ways in which scientists collaborate.

Some but not all students report that they really enjoy the microbiology/biomedicine application.  

Creative Commons License: 
Creative Commons Licence

Comments

I updated the handout and instructor notes for 2020! Over the years, I find that there are always students who fail to make the complex they intend. Last summer, I tried to make the ligands myself, and I had no trouble. I think the syntheses work, but they may be a challenge for your students.

My favorite part of this experiment is that students have to take a whole bunch of data and use it to draw a conclusion. To me, the end result is worth the complexity!

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