Surface-immobilized adeno-associated virus nanoparticles for applications in controlled gene delivery and biosensing
McConnell, Kellie Irene
Doctor of Philosophy
Adeno-associated virus (AAV) is a 25 nm replication deficient DNA virus most commonly studied for human gene therapy applications. The work detailed in this thesis investigates the controlled delivery of AAV from surfaces for both transduction and biosensing applications. First, AAV was tested for compatibility with substrate-mediated gene delivery approaches. Two reverse transduction applications were investigated: (1) spatial localization of cells and virus vectors for tissue engineering applications and (2) live cell genetic microarrays. To drive the proper differentiation and assembly of cells within tissue engineering constructs, gene expression patterns may need to be tightly regulated. To localize adhesive proteins and AAV, polydimethylsiloxane stamps and protein adhesive alkanethiols were used. By adsorbing AAV onto adhesive proteins, including human fibronectin, laminin, collagen I, elastin and poly-l-lysine, both cell adhesion and gene delivery were localized to a defined pattern. Gene delivery was efficient on all protein surfaces, with higher expression observed on laminin surfaces. AAV was also patterned using a robotic spotter to create live cell genetic microarrays, creating localized cell islands expressing GFP. This potentially high-throughput technique could be extended to study complex genetic interactions within cells, such as stem cells or induced pluripotent stem cells. Additionally, AAV was explored as a biosensor by modifying virus output functionalities. Wild-type AAV2 externalizes an N-terminus region containing a phospholipase A2 (PLA2) domain during intracellular processing, allowing the virus to escape the endosomal pathway and deliver genetic cargo. This externalization can be replicated outside of cells through heat treatment. AAV2-ΔPLA2-His was created by replacing the PLA2 domain with a nickel binding hexahistidine tag. This replacement allows heat-treated mutant virus to bind a nickel affinity column. Finally, directed evolution was used to (1) improve the ability of AAV to deliver genes into target cells or (2) alter AAV biosensor inputs. Virus libraries were created using error-prone polymerase chain reaction (EP-PCR) to introduce random amino acid modifications into the protein capsid. The error rate for these libraries was estimated to be between 5-7 errors per cap gene. Combining surface immobilization with directed evolution could allow for precise control of AAV for gene delivery and biosensing.
Applied sciences; Adeno-associated virus; Gene delivery; Biosensing; Biomedical engineering