Tailoring Polysaccharide-Silica Gel Monoliths as Biosensors for the Detection and Removal of Emerging Contaminants in Aquatic Ecosystems, through the Immobilization of Vibrio fischeri

D. García, Z. Mercado, N. Rosario, M. del Mar Tolentino, Z. Flores, L. Díaz
University of Puerto Rico, Río Piedras Campus,
United States

Keywords: silica-polysaccharide, sol-gel, V. fischeri, whole-cell imprinting, biosensors

Summary:

Throughout history, humankind has created countless substances for the improvement of their quality of life, such as personal care products and pharmaceuticals. However, only a fraction of these man-made substances are regulated, and most of them end up in bodies of water and affect aquatic as well as terrestrial organisms. It is very difficult for relevant agencies to keep up with the millions of compounds that have been found or created, and thus the development of methods for their detection and remediation is very important. This project aims to construct a biosensor for the detection of environmental pollution, through the synthesis of a whole cell imprinted polysaccharide-silica matrix. For this purpose, Ulvan (a polyanionic algal polysaccharide) was extracted from Ulva lactuca and purified. BCA protein assay showed that the protein content of the extract was approximately 3%. IR Spectrum of the polysaccharide showed the characteristic ulvan peaks. After the extraction, Ulvan -along with THEOS as the silica precursor- was used in the synthesis of a nanostructured material through the sol-gel method. Using the whole cell imprinting technique, the material was imprinted with V. fischeri cells, for their eventual immobilization and use as the biological component of the biosensor. Thermogravimetric Analysis (TGA) of the whole cell imprinted gels showed that the material was thermally stable up to 700C, losing only 14% of its initial weight with 10% being solvent loss. SEM micrographs reveal that the first attempt at immobilizing the bacteria was only partly successful, as they underwent cell lysis. For the next attempts, reaction conditions must be modified to avoid this. V. fischeri was chosen as the biological component because of its ability to grow and emit bioluminescence. The bacteria were grown in the presence of various emerging contaminants, which had no effect on its growth, except when the bacteria were exposed to known antibiotics. Conversely, bioluminescence did change significantly in presence of caffeine and amlodipine besylate, which would allow V. fischeri to be used for the detection of these contaminants in water. Future work includes the supercritical drying of the gel, metabolomics of the bacteria, and testing the bacteria against other contaminants for the eventual construction of the biosensor.