Analysis of Pyomelanins: Biologically derived conjugated polymers

Abstract

Melanins are an important class of biopolymers that are widespread in nature and have diverse origins, chemical compositions and functions in nature. Their physicochemical properties make them interesting for application in materials science for a range of medical and technical applications. Phenolic monomers are common building blocks of melanins (observed in allomelanin, eumelanin, neuromelanin, pheomelanin and pyomelanin), and are known to play important roles in intermolecular/material interactions which underpin their biological roles and potential technical/medical applications. Alkaptonuria is a rare metabolic disorder that results in the accumulation of homogentisic acid (HGA) in the body which results in dark urine and/or blue/black discoloration of bodily tissues due to the formation of pyomelanin (a complex polymer mostly constituted of polymerised HGA). Alkaptonuria is relatively understudied and the focus of this thesis was to investigate pyomelanin formation/deposition using a variety of analytical techniques which may enhance our understanding of the deposition of pyomelanin in vivo. The thesis includes data from microscopic, spectroscopic and other techniques to offer insights into the physicochemical properties of pyomelanin and variants thereof, observing interesting correlations between the functional groups on the monomers constituting the polymers and their properties (e.g., pendant groups acting as dopants for their electrical properties).