• Design of Protein-based Block Copolymer to Reduce Topological Defects in Polymer Networks

      Kim, Minkyu; Szczublewski, Haley Lynn; Won, Youngwook; Uhlmann, Donald (The University of Arizona., 2019)
      Biological components and complex structures allow natural tissues and cells to have remarkable properties and functions. When studied individually, proteins have been found to have intriguing and unique mechanical properties at the nanoscale. Interest has increased to create synthetic materials that accurately mimic protein nanomechanics at a macroscopic level, but this poses a challenge because protein-incorporated synthetic materials often do not perform as expected. We hypothesize that decreased performance is due to topological defects in polymer networks. Herein, we designed protein-based block copolymers that are capable of self-association to construct polymer networks. By engineering the mid-block with flexible and rigid protein blocks, we were able to find the optimal ratio between the flexible and rigid blocks, that provide greater network strength, caused by increased effective crosslinking density. Specifically, a mid-block ratio where the contour length of the flexible domain is similar to the length of the tertiary structure of the rigid domain increases the gel strength from about 2.5 kPa when presenting an only flexible mid-block to about 7 kPa, meaning network defects were reduced. This platform for reducing network defects creates a foundation for improving polymer network designs and may allow for increased accuracy in translating protein nanomechanics in synthetic materials.
    • Electroless Deposition of Cobalt by Coordination and Reduction of Palladium Catalyst by Surface Amines Groups

      Muscat, Anthony J.; Ng, Amy Sum-Yee; Raghavan, Srini; Uhlmann, Donald (The University of Arizona., 2018)
      Solution-deposited palladium on amine-terminated self-assembled monolayers (SAMs) is a well-characterized catalyst and adhesion layer combination for electroless metallization of dielectric films. A reducing agent is typically added to the deposition bath or a sensitizer such as tin is co-deposited producing relatively thick Pd layers. Thinner Pd deposits would enable barrier seed layers for filling < 10 nm wide gaps in patterned dielectric films with metal. In this work, we eliminated the reducing agent from the deposition bath and worked at pH < 2 to deposit monomeric Pd(2+) species and show that the amine groups terminating the SAM reduce Pd(2+) to Pd(0). The amount of Pd deposited depended on the coverage of the two types of amines on the SAM. The adsorption of PdCl42- ions in solution on protonated amine groups (–NH3+) is well known. Our data suggest that the nonprotonated amine groups (–NH2), which coexist with –NH3+, chemically reduce the Pd(2+) ion to Pd metal by oxidizing to the amine radical cation (–NH2•+). Pd bonds to and covers the –NH2•+ groups in the process depositing around a monolayer of Pd from solution on the SAM-covered silicon oxide surface. The Pd layer served as a catalyst for solution deposition of cobalt films on the surface using a reducing agent under oxygen-free conditions. The cobalt deposited initially as islands that grew together into a closed film with good adhesion.
    • Reverse Engineering the Physical Chemistry of Making Egyptian Faience through Compositional Analysis of the Cementation Process

      Vandiver, Pamela; Pina, Magnum Leo; Vandiver, Pamela; Uhlmann, Donald; Potter, Barrett G. (The University of Arizona., 2016)
      The cementation process of making Egyptian faience, reported by Hans Wulfffrom a workshop in Qom, Iran, has not been easy to replicate and various views have been set forth to understand the transport of materials from the glazing powder to the surfaces of the crushed quartz beads. Replications of the process fired to 950° C and under-fired to 850° C were characterized by electron beam microprobe analysis (EPMA), petrographic thin section analysis, and scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDS). Chemical variations were modeled using thermal data, phase diagrams, and copper vaporization experiments. These replications were compared to 52 examples from various collections, including 20th century ethnographic collections of beads, glazing powder and plant ash, 12th century CE beads and glazing powder from Fustat (Old Cairo), Egypt, and to an earlier example from Abydos, Egypt in the New Kingdom and to an ash example from the Smithsonian Institution National Museum of Natural History.
    • Solution-Deposited Gold Nanoparticles on a Sulfur-Terminated Self-Assembled Monolayer

      Muscat, Anthony; Peebles, Jessica Lynn; Savagatrup, Suchol; Uhlmann, Donald (The University of Arizona., 2021)
      Methods to deposit nanoparticles on surfaces are needed for future manufacturing of electronic devices and coatings with applications in aerospace, biosensors, and solar cells. In this study, gold nanoparticles were deposited from solution on a silica substrate that was coated with an organosilane self-assembled monolayer. Gold nanoparticles with nominal diameters of 13 nm were synthesized in water as seed particles to grow into 50 nm diameter particles through citrate reduction. The silica substrate was hydroxylated and a layer of 3-mercatoptopropyltrimethoxysilane (MPTMS) was deposited providing a sulfur terminal group to adhere the nanoparticles to the surface. The substrate was dip coated in the aqueous gold nanoparticle solution. This study investigated a mixture of sulfuric acid and hydrogen peroxide and dilute nitric acid to hydroxylate the surface, an anneal prior to depositing the silane, and the time in the MPTMS deposition bath to form an adhesion layer on the surface. The layers and surface were characterized with ellipsometry, goniometry, UV-Vis, AFM, SEM, XPS, and EDS. A UV-vis peak at 527 nm confirmed that gold nanoparticles were present in the deposition solution. Ellipsometry and goniometry showed that the average MPTMS thickness was 6.9 ± 1.8 Å and the contact angle was 23°. Gold nanoparticles were visible on the surface in the AFM and SEM images and were about 40-50 nm in diameter. XPS and EDS did not detect gold nanoparticles on the surface due to contamination and low resolution. However, the XPS spectra survey did identify strong sulfur peaks at 226.4 eV and 162.0 eV and a carbon peak at 284.0 eV. These strong sulfur and carbon states reveal a multitude of ligands on the surface for bonding with gold nanoparticles. The results demonstrate that gold nanoparticles can be deposited on an insulating surface and has applications in selective deposition of thin conductive layers to form wires or electrodes for devices.
    • Translational Predictive Model for Heart Failure Recovery in LVAD Patients Receiving Stem Cell Therapy

      Khalpey, Zain I.; Mikail, Philemon; Slepian, Marvin; Secomb, Timothy; Uhlmann, Donald (The University of Arizona., 2016)
      Introduction: Heart failure remains a major public health problem, with recent estimates indicating that end-stage heart failure with two-year mortality rates of 70-80% affects over 60,000 patients in the US each year. Medical management can be used but success declines for patients with end stage heart failure. Although cardiac transplantation is optimal, less than 2500 cardiac transplants are performed annually due to the severely limited supply of donor organs. Mechanical circulatory support (MCS) devices are now routinely used to bridge patients with end-stage heart failure who become critically ill until a donor heart is available. The use of stem cell therapy to treat heart failure has been gaining significant ground in recent years, specifically due to its regenerative properties, and both animal and human models have shown significant improvements in ventricular mass, ejection fraction, vascularization, wall thickness, and infarct size reduction. Using the patients' HeartWare HVAD device diagnostics, we were able to acquire our response variable; pulsatility. Pulsatility is a variable measure of the differential between minimum and maximum flow and is dependent on device motor speed, power, current, and fluid viscosity. This measurement is important as it relates to the contractility of the heart and could potentially be used as an end point in determining when a patient is healthy enough to have their HVAD explanted. We set out to develop a low cost and effective predictive model to determine amniotic mesenchymal stem cell's ability to repair compromised cardiac tissue of patients using the Total Artificial Heart (TAH) and Donovan Mock Circulation Tank (DMC). Methods: Predictive modelling was performed using the TAH and DMC. The system was set to a range from critical heart failure to a normal operating conditions through the variation of preload, afterload, and ventricular drive pressures with the intent of comparing the results to our patient population. Patients (n=7, 3 dilated, 4 ischemic) received intravenous and intra-myocardial injections of a heterogeneous amniotic mesenchymal stem cells mixture and liquid matrix (MSCs+LM) at HVAD implant. Groups were analyzed based on treatment; control (HVAD only, n=7) versus stem cells (HVAD + MSCs+LM). HeartWare log files were acquired from patients' devices and analyzed in SAS and Matlab. Results from the patient study were compared to the predictive model to determine levels of stem cell response. Results: Pulsatility was found to increase with left drive pressure and afterload. Lower drive pressures resulted in a drop off in pulsatility at higher afterloads while higher drive pressures were able to compensate for any afterload. Pulsatility also increased with preload but lower drive pressures were unable to fully eject at the highest preloads, resulting in a reduced pulsatility. We observed the effects of the stem cell injections on pulsatility and found that patients receiving therapy demonstrated statistically significant increases in pulsatility at 15-20 (p=.0487), 25-30 (p=.0131), 35-40 (p=.0333), and 75-80 (p=0.0476) days post implant. At minimum, when comparing the patient results to the in vitro model, the therapy resulted in a progression from end stage HF conditions to medium cardiac function conditions. At maximum, the therapy resulted in a progression from end stage HF to normal healthy operating cardiac function. Conclusions: Stem cells demonstrated a significantly increased rate of change in pulsatility within the first 40 days and at 80 days post implant when compared to control. They also demonstrated progression from end stage HF to normal healthy cardiac function at two time periods (Days 40, 90). These results justify expansion of the study to encompass a larger patient population to verify the results of the in vitro model to predict cardiac regeneration with multiple functional status indicators.