Sensors, sunscreens, and shirts

Abstract

As the largest segment of the global skincare market, facial care products are designed and marketed as commodities that cleanse, protect, and moisturize skin. Over the past decade, these products have diversified into multi-functional formulations with claims to also renew, rejuvenate, and restore skin function. This trend has not only stimulated the creation of new biomaterials that provide both aesthetic and therapeutic benefits but has also prompted alternative platforms to evaluate their effects such as color, texture, and function. In alignment with these growing trends, this thesis describes the design of multifunctional biomimetic materials that can be used for future skincare products. Originally inspired by the adaptive coloration exhibited by marine animals like cephalopods, I describe the design of materials that absorb and dissipate solar radiation, enhance natural color, and offer a stimuli responsive color-changing platform. First, I discuss methods for characterizing the cephalopod-derived chromophore, Xanthommatin (Xa), from both natural and synthetic origins by employing a suite of chromatographic, spectrophotometric, and spectroscopic analytical techniques. Applications of these chromophores were then explored in two contexts: (1) biohybrid colorants and (2) alternative ultraviolet (UV)-filters. In the first, I describe the design and fabrication of colorants containing Xa encased within silica-based nanostructures. I employed a biomimetic approach to encapsulate Xa with amine-terminal polyamidoamine (PAMAM) dendrimer templates which helped stabilize the pigment. Depending on the concentration of Xa used in the reaction, the resultant biohybrid nanomaterials generated a range of neutral colors of differing hues. When applied as coatings, these colorants could be triggered to change color from yellow/gold to red in the presence of a chemical reducing agent. Altogether, these capabilities demonstrated the ability to process biochromes like Xa as nanomaterials that can be applied as coatings with a tunable, dynamic range. In the second context, I explored the utility of Xa as a sunscreening agent. This is important because commercially available suncare products, containing traditional chemical and physical UV-filters, have recently been reported to elicit systemic toxicities prompting a reevaluation of their safety for humans. As part of a collaborative effort, I demonstrated the application of Xa as an alternative chemical UV-filter with a tunable sun protection factor (SPF) range. The photoprotective properties and cytocompatibility of Xa-based materials were investigated in vitro, where we found over 95% cell viability when incubated directly with fibroblasts. An added, unexpected feature is that Xa behaves as a free radical scavenger, making it among one of the first UV-filters that can not only protect against solar irradiation but can also be used in preventative skin care. Altogether, our work supports the use of this cephalopod-inspired platform towards the development of next-generation consumer healthcare products.