Synthesis, Characterization and In-vivo Testing of Photoactivatable Insulin Depots for Continuously Variable and Minimally Invasive Insulin Delivery
Abstract
Proteins are macromolecules involved in a diverse array of functions. Mutations or
abnormal levels of proteins are indicated in several diseases. Despite showing early
promise, the translation of protein therapeutics into the clinics has been challenging. The
stability of these macromolecules, their delivery, and penetration inside the cells have been
the main hurdles limiting their true potential. In the dissertation, various strategies to
overcome such protein delivery challenges are discussed.
Insulin is a lifesaving peptide for millions of diabetics around the world. Despite
significant progress in insulin therapies, the quality of life in diabetics is constrained by the
burden of multiple daily injections, invasive nature of therapy and inability to control the
blood glucose tightly. To address these concerns, we constructed a photoactivatable insulin
depot (PAD). In the approach, an insoluble depot of modified insulin was created by
linking insulin covalently to photolabile caging moieties. Transcutaneous irradiation
breaks the bond to release insulin from the depot into the systemic circulation. Chapter 3
describes the first successful testing on our PAD technology in diabetic animal models. In
Chapters 2 and 4, I describe second-generation materials incorporating more efficient
photolabile groups utilizing visible light wavelengths and PAD material with greater
insulin loading. These changes improved the overall performance by several folds when
tested in-vivo.
Chapter 5 discusses the strategies addressed to deliver siRNA inside cells for
effective light-activated RNA interference (LARI). LARI can be used for studying biology
and cellular processes.
Once administered, proteins are prone to degradation by ubiquitous proteases,
limiting their circulation time and therapeutic effect significantly. Chapter 6 discusses
prodrug strategies to temporarily modify proteins to shield them against proteases. We
envisioned cross-linking amino acid residues on the surface via small crosslinkers. The
tight bridges would hinder proteases from binding to proteins and unwinding the helices
preventing their proteolysis. We also attempted integration of this approach to achieve
intracellular protein delivery which is another obstacle in protein delivery. Here, the cross
linking was performed via disulfide linkages. The disulfide groups would be reduced once
inside the cells, yielding native proteins.
Table of Contents
Introduction: photoactivatable insulin depot -- Synthesis of insulin macro polymer -- In-vivo testing of first-generation pad material -- Synthesis and testing of advanced second-generation material -- Light activated SiRNA nanoparticles -- Intracellular protein delivery using protein prodrugs
Degree
Ph. D. (Doctor of Philosophy)