Grant: Discovery Grants Program - Individual

There is undoubtedly a global need to develop sustainable approaches to chemistry in general, but to silicon chemistry in particular. Although linear silicone polymers have been shown to degrade into benign compounds in the environment, less is known about the impact of silicone rubbers. The 12 Principles of Green Chemistry, first proposed in 1998, illustrate guidelines for lessening the environmental impact of chemical processes. Biotechnology represents one route that can be utilized to develop green methodologies in silicon chemistry. We propose to continue our exploration of silicon biotechnology through the synthesis and study of silicon-based structured materials. Silicon biotechnology will be applied to the synthesis of two principle classes of compounds: (i) siloxane-containing phospholipids, and (ii) self-healing, recyclable silicone polymers. Our preliminary work has demonstrated that biocatalysis can be utilized in the synthesis of siloxane analogues of phospholipid structures. Whereas biologically relevant phospholipids typically require multiple extrusion cycles through a membrane in order to achieve ideal vesicles for applications such as vaccine delivery, siloxane phospholipids spontaneously form these structures. Biotechnology will be used to synthesize a library of silicon-containing lipid structures. This library of lipids will include modifications to the lipid tails and the head group, which will allow us to better understand how these molecules interact with each other and how they interact with living cells. Silicone polymers are ubiquitous in our world, found in applications such as lubricants, adhesives, insulators, personal care products, etc. However, one of the fundamental limitations of silicone elastomers used in such applications is that they are subject to mechanical damage, which can impinge upon the material's useful lifetime, and these materials are often difficult to recycle. In keeping with the Principles of Green Chemistry, we propose to apply silicon biotechnology to the synthesis of self-healing, recyclable silicones. Building upon our existing expertise, silicone polymers cross-linked using biologically inspired interactions, such as those found in DNA, will be explored. The capacity of these materials to heal from mechanical damage as well as their mechanical properties will be studied. One of the key challenges of silicone biotechnology is the propensity of enzymes to function best in aqueous environments, while silicones are often used as water repellants. In an effort to address this challenge we will be modifying enzymes with silicones to increase their solubility, and subsequent activity, in organic solvents, thereby opening new doors in enzyme-mediated silicon-based reactions. This programme will permit us to further develop our understanding of biocatalytic reactions in silicon chemistry, while concomitantly exploring interesting polymeric and biologically related silicon-containing materials.