Graduation Year

2018

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Chemical Engineering

Major Professor

Piyush Koria, Ph.D.

Committee Member

Bob Frisina, Jr., Ph.D.

Committee Member

Nathan Gallant, Ph.D.

Committee Member

Martin Muschol, Ph.D.

Committee Member

Christopher Passaglia, Ph.D.

Keywords

Neurotrophin, Urea, Inclusion Body, Disulfide-Shuffling, Self-Assembly

Abstract

Elastin-like peptide (ELP) fusions promote therapeutic delivery and efficacy. Recombinant proteins, like neurotrophins, lack bioavailability, have short in vivo half-lives, and require high manufacturing costs. Fusing recombinant proteins with genetically encodable ELPs will increase bioavailability, enhance in vivo solubilization, as well as provide a cost-effective method for purification without the need for chromatography. During expression of neurotrophin-ELP (N-ELP) fusions, dense water-insoluble aggregates known as inclusion bodies (IBs) are formed. Inclusion bodies are partially and misfolded proteins that usually require denaturants like Urea for solubilization. Strong denaturants arrest ELPs stimuli-responsive property and increase unwanted aggregation, making purification difficult, yet possible. The current field of study exhibit issues with protein recovery due to solubility issues and aggregation. This study examines the solubility challenges of inclusion body proteins and the role ELP fusion tags play on IBs solubility. Elastin-like peptides are a class of stimuli-responsive biopolymers whose biocompatibility and limited toxicity are attractive for biological applications. ELPs are tunable polymers, which consist of peptide repeat units (VPGXG), where X is any amino acid except Proline while the guest residue or length of the sequence can be chosen. ELPs have uniquely tunable phase transitioning properties that allow the protein to undergo molecular self-assemblies into different nanostructures in response to the changes in their environment (e.g. pH or temperature). Optimizing the purification process via suppressing aggregation during the refolding process has increased protein recovery slightly however, more work is needed to attain 90 percent recovery. Usage of ELPs has increased the solubility of N-ELP fusions, specifically for brain-derived neurotrophic factor ELP fusions.

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