Synthesis, Characterization and In-vivo Testing of Photoactivatable Insulin Depots for Continuously Variable and Minimally Invasive Insulin Delivery

Title from PDF of title page viewed May 15, 2020Dissertation advisor: Simon H. FriedmanVitaIncludes bibliographical references (pages 275-290)Thesis (Ph.D.)--School of Pharmacy and Department of Chemistry. University of Missouri--Kansas City, 2019Proteins 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.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 prodrug

Local Atomic Structure of Martensitic Ni2+x_{2+x}Mn1−x_{1-x}Ga: An EXAFS Study

The local atomic structure of Ni$_{2+x}$Mn$_{1-x}$Ga with 0 $\le$ $x$ $\le$ 0.16 alloys was explored using Mn and Ga K-edge Extended X-ray Absorption Fine Structure (EXAFS) measurement. Inorder to study the atomic re-arrangements that occur upon martensitic transformation, room temperature and low temperature EXAFS were recorded. The changes occurring in the L2$_1$ unit cell and the bond lengths obtained from the analysis enables us to determine the modulation amplitudes over which the constituent atoms move giving rise to shuffling of the atomic planes in the modulated structure. The EXAFS analysis also suggests the changes in hybridization of Ga-$p$ and Ni-$d$ orbitals associated with the local symmetry breaking upon undergoing martensitic transition.Comment: Accepted for publication in Physical Review

Local atomic arrangement and martensitic transformation in Ni50_{50}Mn35_{35}In15_{15}: An EXAFS Study

Heusler alloys that undergo martensitic transformation in ferromagnetic state are of increasing scientific and technological interest. These alloys show large magnetic field induced strains upon martensitic phase change thus making it a potential candidate for magneto-mechanical actuation. The crystal structure of martensite is an important factor that affects both the magnetic anisotropy and mechanical properties of such materials. Moreover, the local chemical arrangement of constituent atoms is vital in determining the overall physical properties. Ni$_{50}$Mn$_{35}$In$_{15}$ is one such ferromagnetic shape memory alloy that displays exotic properties like large magnetoresistance at moderate field values. In this work, we present the extended x-ray absorption fine-structure measurements (EXAFS) on the bulk Ni$_{50}$Mn$_{35}$In$_{15}$ which reveal the local structural change that occurs upon phase transformation. The change in the bond lengths between different atomic species helps in understanding the type of hybridization which is an important factor in driving such Ni-Mn based systems towards martensitic transformation

Effect of Oxygen Content on Magnetic Properties of Layered Cobaltites PrBaCo2O5+\delta

The effect of oxygen content on the magnetic properties of the layered perovskites has been investigated. The samples, PrBaCo$_{2}$O$_{5+\delta}$ (0.35 $\leq \delta \leq$ 0.80) were prepared by sol-gel method and characterized by X-ray diffraction and DC magnetization. A detailed magnetic phase diagram for PrBaCo$_{2}$O$_{5+\delta}$ is presented. It is found that unlike in the case of heavier rare-earths, ferromagnetic interactions are present at all temperatures below Tc and even in the antiferromagnetically ordered phase. Moreover, in compounds with lower oxygen content, short range ferromagnetic interactions are present even above Tc. This dependence of magnetic properties on oxygen content in these layered perovskites has been linked to the changes in polyhedra around the Co ions.Comment: 20 pages, 10 figures; J. Appl. Phys. vol. 110 issue 5 (2011