EXPLORING SERUM ALBUMIN AS A VERSATILE TOOL: FROM A CARRIER FOR BIOTHERAPEUTICS TO A MOLECULAR TRAP FOR TOXIC COMPOUNDS AND BEYOND

This thesis aims to present an overview of human serum albumin (hSA), highlighting the unique features that make it an appealing candidate for a broad range of biotechnological and biomedical applications. The first chapter introduces the state of the art on hSA, focusing on its recycling mechanism mediated by the human neonatal Fc receptor (hFcRn), which is responsible for hSA’s long half-life (i.e., up to 21 days). The second part of Chapter I summarizes the hSA-based strategies to improve the pharmacokinetic properties of drugs, supporting the importance of the research conducted during my PhD. The second chapter presents my first-author paper published in Protein Science, in 2024. This study describes the crystal structure of a megabody (MgbAlb1c7HopQ) in complex with wild-type (wt) hSA, offering novel insights into the key residues engaged in the interaction. Subsequently, Chapter III presents the structural and functional characterization of 3 human serum albumin variants, engineered in silico by the group of Prof. Sarel J. Fleishman (Weizmann Institute of Science) to be hyper-soluble, stable and expressible in Escherichia coli with high yields. In conclusion, Chapter IV focuses on the structural characterization of mouse serum albumin (mSA) recycling mechanism by Cryo-electron microscopy (Cryo-EM). This investigation seeks to disclose the differences between the recycling mechanism of hSA and mSA.