John E. López Calero - University of Puerto Rico, Mayagüez, PR
Co-Author(s): Ashley M. Cardona Rodríguez, Yesenia Rodríguez Cedeño, Amanda Quintero Garcia, Yamalis López Massa, and Oscar Marcelo Suarez, University of Puerto Rico, Mayagüez, PR
Water has become a precious resource, therefore access to fresh and clean water is critical at a global scale. Nowadays, innovating methods offer clean, fresh, and purified water. In this context, chitosan and titanium dioxide (TiO2) biocomposites could be an alternative appealing solution to this problem, by removing oils, heavy metals, and pathogen colonies while also being an economically viable option. Chitosan is a polysaccharide compose of 1-4 linked d-glucosamine and N-acetyl-d-glucosamine capable of forming gel with antibacterial and flocculent properties. Moreover, titanium dioxide is a photocatalyst excited by ultraviolet (UV) light, able to form active oxygen species that disrupt bacterial cell membranes resulting in cell death. However, bacterial diversity makes antibacterial ineffective when dealing with different bacterial families. It is known that one of the main divisions in the bacterial kingdom is the gram positive and gram negative, the difference is that the first one has only one cell membrane and the latter, two membranes. Our biocomposite should be able to target effectively both types of bacteria with chitosan attacking gram positive and titanium dioxide attacking gram negative. The biocomposites were characterized under a scanning electron microscopy (SEM) and analyzed in a Fourier transform infrared spectroscopy (FTIR). In the present research, we synthesized our biocomposite by mixing chitosan, deionized water, and TiO2. Using a sonicator and magnetic agitators we obtained a fine mix, which we then treated at 55°C for 48 hours. At the same time, an Escherichia coli population was incubated with different cell concentrations. Preliminary results showed a reduction in the number of E.coli colonies, for cell concentrations ranging from 103 to 106 with mixed results for 109. The survival rate was found to by ca. 3.23% for 106 and ca. 0.0002% for 103 while for 109 the biocomposite was not effective. We attributed this outcome to the fact that E. coli is a gram negative bacteria with a strong bilayer membrane which has a high molecular weight acting as buffer against foreign molecules. E. coli also has the ability to form colonies extremely populated as biofilms. In a future work we will test different concentrations of TiO2 and chitosan while extending this research to encompass Staphylococcus aureus as a gram positive bacteria in order to gather additional data in this area.
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Funder Acknowledgement(s): We are grateful to the UPRM Nanotechnology Center technical staff: Boris Rentería and Carlos Rivera. The authors would also like to thank O. M. Suárez’s research group for their support in the project, and Matias Cafaro and Magaly Zapata along with the Biology department for the access of their facilities. Biology graduate students Yoana Guzman and Veronica Figueroa were also of great help to this project. This material is based upon work supported by the National Science Foundation under grants No. 0851449 and 131456 (CREST Program).
Faculty Advisor: Oscar Marcelo Suarez, firstname.lastname@example.org
Role: To reach the objective of this research project I had to seek information from many different data bases to find and design the accurate method for this investigation. When I started to work in this project I developed a method that instantly provided us with positive results. This method consists in synthetizing biocomposite films and testing the bacterial growth in their presence. The bacteria are grown in a solid environment and are then exposed to the films. This procedure requires an extense amount of time for which I have mostly been part of, with the help of the undergraduate students.