Poster V18 - Detection of Metal Ion Concentrations in Fluids Using Identifying Absorbance Spectra

Introduction: Free metal ions can cause adverse effects within the body, leading to foreign immune responses. Current methods to check ion levels over time require expensive laboratory equipment, which is not easily accessible. Metal ions can come from numerous sources, such as metal implants or water sources. Metal implants can include hip or knee replacements, which, according to Harvard Health, approximately 1 million Americans receive yearly. While such replacements can help relieve mobility issues and pain, releasing metal ions into the body can cause problems such as extreme weight loss, cardiac damage, thyroid damage, and harm to neurological function. Furthermore, tracking of global surface water, seawater, wastewater and groundwater for twelve different heavy metals across 25 years indicated an increased concentration of metal ions in these sources. In fact, the U.S. Environmental Protection Agency (USEPA) and World Health Organization (WHO) set threshold value standards, which ten of these metallic ions were found to exceed. Metal concentrations have also increased significantly in developing regions, namely Africa, South America, and Asia, and for many of these areas, lake and river water are common drinking water sources. There is a need to develop an easily accessible and rapid method capable of detecting metal ion concentration within urine and drinking water in the field. We hypothesize the development of a device that utilizes optic fibers as a waveguide to detect low concentrations of metal ions in fluids will provide this tool.

Materials and

Methods: Using a polymethylmethacrylate (PMMA) fiber as a waveguide, leveraging the evanescent wave principle, we will detect low concentrations of metal ions in fluids. Our device shines a light down the waveguide. As photons travel down the fiber, they eventually encounter the waveguide's internal surfaces. The light can either leave the fiber or be internally reflected and continue to propagate. Assuming conditions necessary for total internal reflection are met, no light escapes the fiber. When photons interact with the surface of a material, an evanescent wave will form at the interaction surface. The distance at which the field protrudes is known as the penetration depth of the wave, and it typically ranges from 30 nm to 300 nm. Using a chelating agent to bind the metal to the surface of the fiber, the metal ions that are adhered will influence the behavior of the light propagating down the waveguide. This is due to the absorption wavelengths of the metal. These metal ions will absorb light at specific wavelengths, attenuating light as it travels through the waveguide. Our device has a detector positioned at the end of the waveguide to measure the decrease in the intensity of these wavelengths, allowing us to correlate the loss in intensity to the concentration of specific metal ions in the fluid.

Results, Conclusions, and Discussions: Preliminary data (Figure 1) for this device shows distinct changes to the optical spectra that allow for clear detection of cobalt ions in urine using a chelating agent (DTTPA). The peak at the 510 nm wavelength is where we see the largest peak in both urine and DI water, hence the wavelength of interest. It is encouraging that the system could detect cobalt in both DI water and urine; while the background signal from urine did affect the spectra it did not obscure the 510nm peak relevant for cobalt detection. Unfortunately, as the concentration of the metal ions decreased, our current spectrophotometric system design was not able to detect the higher end of the clinically relevant concentrations of cobalt ions. We are currently improving our system design to increase the limit of detection for the optical fiber, but the preliminary data shows that spectrophotometry is a promising route.
Future work will investigate different attractive agents on the surface of the waveguide and test for different kinds of metals beyond Cobalt. These optical fibers will attract metal ions to their surface and accurately determine their concentrations in various fluids, offering a versatile tool for environmental and health-related applications.
Concerns about free metal ion concentrations in drinking water are rapidly escalating due to their adverse effects and the rapid progression of this issue. Developing a quick and accurate method to detect metal ions in drinking water is crucial for public safety. This technology would improve compliance with industry and government regulations, enhance environmental monitoring, ensure effective water treatment processes, and boost public confidence. Additionally, joint replacements and related health complications affect millions annually in the U.S. alone. This device has significant potential to improve patient outcomes by enabling healthcare providers to monitor implant conditions consistently, non-invasively, and ideally at home.

Acknowledgements (Optional): I would like to thank the non-presenting members of my team: Sam Leach, Azrin Jamison, Diego Nigoa
I would like to thank my committee members: Dr. Lucas Schmidt, Dr. Bruce Gao, Dr. Melinda Harman and Dr. Delphine Dean
Funding was provided by NIH R01 MH111366. I would also like to acknowledge the Clemson Creative Inquiry Office.
Finally, I would like to thank Adam Hill for being vital in my pursuit of my research and the late Dr. Melissa “Awesome” McCullough, who, without her time and commitment, none of this work would have been possible.