A Combinatorial Peptoid-Based Platform for the Development of Selective Metal Binding Materials
Ligands with the ability to selectively chelate individual metals can be applied in heavy metal remediation, recycling, and metal separations, yet such ligands are currently rare and those processes are avoided or expensive due to the use of nonspecific methods. In order to identify compounds that will selectively chelate metal ions, we designed and synthesized a peptoid library and several screening methods to identify motifs capable of chelating low concentrations of various metal ions in complex sample media. Peptoids, or N-substituted glycine oligomers, are a recently developed class of peptidomimetics that have a variety of new structures and applications. The first target application was the remediation of water contaminated with toxic Cr(VI). Identified structures outperformed commercially available resins and demonstrated the ability to reduce the amount of Cr(VI) to levels within the range of the EPA guidelines. A new library generation was developed for the selective coordination of individual ions in a biological context. One target of this library was lethal Cd(II), and peptoid-based ligands were capable of reducing the concentrations of Cd(II) in human serum to 0.5 μM, comparable to the reported threshold for acute toxicity. After demonstrating the success of this screening platform, the platform has been adapted for many applications with a variety of metal ions described within. Towards the development of inexpensive functional materials, a biorthogonal bioconjugation reaction has been applied to immobilize peptoid sequences after synthesis. This work begins to illuminate the diverse array of applications of selective ligands for individual metal ions and demonstrates the potential for peptoids in highly functional materials.