Photochemical transformations of multicomponent aggregates containing photolabile small molecules, heavy metal ions, and/or nanoparticles in biological environments - Abstract Every day, light transforms hundreds of millions of tattoos. Despite the fact that laser tattoo removal is a multi-billion dollar per year industry, we understand surprisingly little about tattoo photodegradation, the hazards of the photoproducts, and the subsequent health risks to people with tattoos. Tattoo inks themselves may contain high levels of toxic heavy metals, cytotoxic nanomaterials, and potentially carcinogenic molecular pigments. What is specifically unclear is how photodegradation transforms and/or releases harmful materials into the body. Of the handful of studies that purport to investigate tattoo photochemistry, most have little biological relevance (e.g., studies conducted in deoxygenated organic solvents), explore materials not used in tattoos, or simply do not even consider tattoos at all. Understanding tattoo photodegradation and the attendant risks requires a strategy that couples analytical chemistry and photochemistry with materials physics and cellular biology. This proposal details a transdisciplinary approach designed around meaningful, authentic research experiences for undergraduate students. We plan to pursue three complementary, yet distinct, specific aims. 1) Students will use analytical methods to identify the photodecomposition products of tattoo inks. Under illumination, molecular pigments can breakdown into carcinogenic products (benzene, primary amines, halogenated aromatics) though the identities of these products are often unknown. Also unexplored is the impact of semiconductor particles usually present in inks. 2) Using a combination of time-resolved spectroscopies, students will explore how embedded tattoo inks break down under illumination. We understand little about how light causes tattoo inks to leave the dermal layer and, in fact, the assumed mechanism of particle fragmentation has never actually been demonstrated experimentally. We will directly observe tattoo inks undergoing laser-illumination using nanosecond shadowgraphy and couple that with photoacoustic spectroscopy and luminescent thermometry to understand what conditions the ink particles experience under illumination and when they start to fragment. 3) We will use human dermal fibroblasts as a model for the human dermis to understand the potential effects of tattoos inks and photodecomposition products on cell viability. Students will assess the potential toxicity of the tattoo inks themselves, as well as the photoproducts, through a variety of assays to build a detailed picture of the cytotoxicity of photodegraded tattoos. Successful completion of this project will yield a significantly deeper understanding of the risks faced by millions of Americans with tattoos as well as offer a unique and meaningful training experience for undergraduate students.
