Confining functional materials in protein-based assemblies

The design and engineering of biological building blocks that self-assemble into highly ordered, well-defined structures is of growing interest for applications in nanotechnology. For applications in biomedicine and drug delivery, the design of biomolecular cargo carriers has largely focused on either lipid-based assemblies (vesicles and micelles) or protein-based assemblies (cage-like proteins and virus- based assemblies). Owing to their reversible assembly, stability, monodispersity and biocompatibility, viruses are highly attractive candidates and have consequently received much attention. The outer shell of viruses is composed of multiple copies of identical virus coat proteins that can be modified by chemical or genetic means for enhanced functionality or molecular targeting, and their self-assembly can be controlled by tuning the pH or ionic conditions. Based on virus coat proteins, the term “virus-like particle” has been used to describe protein-based entities that resemble the size and morphology of native viruses but lack their natural genomic cargo. Viruses and virus-like particles have since been used for the encapsulation of a broad range of functional materials. Yet, there is still a lack in knowledge in the factors which drive the self-assembly process to occur. The aim of this thesis was to investigate and understand the interplay between the molecular template and the virus coat protein of Cowpea Chlorotic Mottle Virus (CCMV), in particular, how to control and direct the self-assembly of viruses. The central theme of this thesis is based on the template-directed self-assembly of viruses, with a particular emphasis on the topics described in Chapter 2 in relation to viruses and functional cargo. The first two experimental Chapters, 3 and 4 described the controlled assembly of highly monodisperse virus-like particles (using light-absorbing phthalocyanines and DNA-enzyme hybrids), Chapters 5 deals with template induced clustering of CCMV resulting (using a conjugated polyelectrolyte) and Chapter 6 described structural changes in the CCMV shell upon cargo release in the absent of Mg2+ ions (using a photo-responsive self- immolative polymer) and finally in Chapter 7 the tunable morphology of CCMV from spherical to rod-like assemblies (using two different platinum(II) complexes) is investigated. The results presented in this thesis provide a detailed, systematic study of the role of the molecular template in directing virus self-assembly and sheds new insights towards the design of the next generation of functional hybrid materials