In recent years, Endocrine Disrupting Chemicals (EDCs) have become a major focus in environmental chemistry, marine biochemistry and medicine. These substances derive from various industrial products, eg in agriculture and pharmaceuticals, and residues are not completely eliminated in the human body. They are often excreted only slightly transformed or even unchanged, and are detected in sewage and surface water samples at concerning levels. Compounding the problem is that they are not easily removed by water treatment. EDCs interfere with hormone action, block natural hormones from working or mimic them and are implicated in harmful biological trends, eg feminisation of fish, decreasing sperm counts in humans and cancer of the reproductive organs. For these hormonally-active compounds, conventional removal methods are questionable because very little is known about the ultimate degradation products. Progesterone is the most important and only naturally occurring hormone of the progestagens. It is secreted by the female reproductive system, is responsible for ovulation, prepares the uterus for the foetus and maintains pregnancy. The aim of this work is to investigate whether mineral surfaces can catalyse hormone decomposition under UV light. We are studying the interface between an aquatic pollutant, progesterone, and a mineral surface, via the adsorption kinetics and characteristics of the hormone and its reaction under UV light. In contrast to earlier progesterone studies, including chlorination and ozonolysis, this work is at the nanoscale and single molecule level. An Atomic Force Microscopy (AFM) liquid cell has been used, allowing surface-adsorbed molecules to be imaged and/or manipulated in-situ in physiological buffer solutions. This also allows dynamic biological processes to be imaged at the water-mineral interface as the imaging environment is altered by, for example, the addition of chemicals to the buffer solution. By imaging the surface in water, subsequently injecting a solution containing the hormone and the addition of a divalent cation the adsorption process can be followed from time zero. Hormone adsorption onto Au- and Cu-coated mica and glass was also studied with in-situ stress measurements based on a cantilever bending method and the Quartz Crystal Microbalance (QCM). For degradation experiments in air, a 254nm wavelength UV lamp was used to initiate changes on the progesterone covered mineral surface. Exposure was either constant, during scanning, or intermittent, between successive scans. Significant structural changes of the hormone on the mineral have been observed. For UV degradation of progesterone in liquid, optical fibres from a deuterium light source are applied in-situ onto a very constrained area of the sample. The main results from experiments performed in liquid and in air show that adsorption and degradation can be imaged in-situ and in real time, which provides a significant basis for further research.
|Translated title of the contribution||Adsorption and degradation of progesterone onto muscovite mica|
|Title of host publication||MRS Spring Meeting, San Francisco, USA|
|Publication status||Published - 13 Apr 2009|