Designing Architected Materials to Mimic Native Tissue Mechanics and Improve Cartilage-Regenerative Implants

Many cartilage tissues in the body fail to heal after injury. Two of these tissues are growth plate cartilage and articular cartilage. Tissue engineering is a promising strategy for treating injuries to these tissues by replacing damaged cartilage with a material that acts as a scaffold to support living cells. Ensuring cells produce the desired type of tissue, however, remains challenging. Controlling cell behavior is, in part, a mechanical problem. Cells respond uniquely to mechanical stimulus. Implanted scaffolds must therefore provide the right mechanical environment to direct cell behavior to regenerate cartilage. Too stiff of an environment may encourage bone growth; too soft of an environment may encourage inferior fibrocartilage formation or even lead to cell death from excess strains during physiological loading. Additionally, the scaffold must bear native physiological loads. Failure to mechanically support joint forces in the knee, for example, can leave surrounding native cartilage vulnerable to excessive stress that propagates damage.In this dissertation, I aim to improve upon established cartilage-regenerative scaffolds by incorporating stiff 3D printed structures into the material. I optimize the stiffness of these structures by tuning their geometry and prescribe regional gradients in stiffness to mimic native tissue mechanical environments. To inform the design of these structures for use in regenerating growth plate cartilage, I characterized the mechanical properties of growth plate cartilage. I found local variations in stiffness where new bone forms in the growth plate; these variations in mechanical environment may be important to directing cell behavior. Finally, I tested if a scaffold reinforced by a 3D printed structure preserved adjacent native cartilage when implanted in a pig. I found that the reinforced 3D printed composite scaffold may have effectively prevented degradation of surrounding cartilage. I also found that the different mechanical environments of the scaffold featured distinctly different regions of bone and fibrocartilage formation. My findings in this dissertation indicate that 3D printed architected material-based scaffolds can control mechanical environment and may improve upon existing regenerative scaffolds for treating articular cartilage and growth plate injuries.</p

Multifunctional energy storage and piezoelectric properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films on stainless-steel substrates

AbstractThe miniaturization of electronic devices and power systems requires the fabrication of functional components in the form of micrometer-sized thick films. A major challenge is the integration of functional ceramics with metals, which are considered incompatible with high-temperature ceramic processing. To overcome the integration barrier, an aerosol deposition (AD) spray-coating method based on room temperature deposition can be used. By employing the AD method, we were able to deposit relaxor-ferroelectric 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 ceramic thick films on low-cost stainless-steel substrates. The as-deposited films were dense, with ∼97% of the theoretical density. Moreover, the post-deposition annealing at 500 °C did not result in any microstructural changes. Compared to the as-deposited films, the annealed films exhibit improved energy storage and electromechanical properties. The annealed thick films achieve a recoverable energy density of 15.1 J⋅cm−3 at an electric field of 1350 kV⋅cm−1 and an electric-field cycling stability of 5 million cycles. A piezoelectric response was detected through the entire film thickness by piezoelectric force microscopy. Macroscopic displacement measurements revealed a maximum relative strain of 0.38% at 1000 kV⋅cm−1, corresponding to inverse effective piezoelectric coefficient of ∼40 pm⋅V−1. In this study, we overcame the integration challenges and demonstrated the multifunctionalization of future ceramic-metal structures, as the deposited thick films on stainless steel exhibit energy storage capability and piezoelectric properties

Pure Profit for Russia: Benefits of Responsible Finance

The purpose of this report is to serve as a post financial crisis handbook that will help both financiers and environmentalists in Russia to cooperate in establishing a ‘greener’ and less risky financial system in a similar manner to which this process is underway in other emerging markets such as China, Brazil and South Africa. The report provides an overview of the evolution of international mechanisms of environmental and social responsibility in the global financial sector, quantifies the scope of exposure of foreign and Russian financial institutions to environment-intensive sectors of the Russian economy, and concludes with recommendations regarding actions that might be implemented by both the Russian government and domestic financial institutions. The report has been prepared within the framework of the project ‘Integration of Environmental and Social Safeguards, Standards and Processes and the Climate Change Agenda in the Russian Finance Sector’ implemented by WWF-Russia and WWF-Germany with the financial assistance of the Federal Agency for the Environment (Umweltbundesamt/UBA) under the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), and with the support of the Russian Ministry of Natural Resources and Ecology, European Bank for Reconstruction and Development (EBRD), in collaboration with the Equator Principles Outreach Group for Russia

Pure Profit for Russia: Benefits of Responsible Finance

The purpose of this report is to serve as a post financial crisis handbook that will help both financiers and environmentalists in Russia to cooperate in establishing a ‘greener’ and less risky financial system in a similar manner to which this process is underway in other emerging markets such as China, Brazil and South Africa. The report provides an overview of the evolution of international mechanisms of environmental and social responsibility in the global financial sector, quantifies the scope of exposure of foreign and Russian financial institutions to environment-intensive sectors of the Russian economy, and concludes with recommendations regarding actions that might be implemented by both the Russian government and domestic financial institutions. The report has been prepared within the framework of the project ‘Integration of Environmental and Social Safeguards, Standards and Processes and the Climate Change Agenda in the Russian Finance Sector’ implemented by WWF-Russia and WWF-Germany with the financial assistance of the Federal Agency for the Environment (Umweltbundesamt/UBA) under the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU), and with the support of the Russian Ministry of Natural Resources and Ecology, European Bank for Reconstruction and Development (EBRD), in collaboration with the Equator Principles Outreach Group for Russia

Oral Fluid Testing during 10 Years of Rubella Elimination, England and Wales

Surveillance of rubella in England and Wales has included immunoglobulin M testing of oral (crevicular) fluid from reported case-patients since 1994. The need for laboratory confirmation to monitor rubella elimination is emphasized by poor sensitivity (51%, 95% confidence interval 48.9%–54.0%) and specificity (55%, 95% confidence interval 53.7%–55.6%) of the clinical case definition. During 1999–2008, oral fluid from 11,709 (84%) of 13,952 reported case-patients was tested; 143 (1.0%) cases were confirmed and 11,566 (99%) were discarded (annual investigation and discard rate of clinically suspected rubella cases was 2,208/100,000 population). Incidence of confirmed rubella increased from 0.50 to 0.77/1 million population when oral fluid testing was included. Oral fluid tests confirmed that cases were more likely to be in older, unvaccinated men. Testing of oral fluid has improved ascertainment of confirmed rubella in children and men and provided additional information for assessing UK progress toward the World Health Organization elimination goal

Temperature‐ and stress‐dependent electromechanical properties of phase‐boundary‐engineered KNN‐based piezoceramics

Abstract The influence of stress on the small‐signal dielectric permittivity and piezoelectric coefficient of polycrystalline lead‐free perovskite 0.92(Na1/2K1/2)NbO3–(0.08 − x)Bi1/2Li1/2TiO3–xBaZrO3 (x = 0, 0.02, 0.04, 0.06, and 0.07) was characterized under different constant uniaxial stress up to −200 MPa within a temperature range of −150 to 450°C, revealing stress‐induced suppression of the electromechanical response as well as shifts in the phase boundaries. For all compositions, the interferroelectric and ferroelectric–paraelectric phase transitions were shifted to higher temperatures under the uniaxial compressive stress. Interestingly, the sensitivity to the applied stress was found to increase with increasing BZ/BLT ratio in the system. The origin of a different extent of stress‐sensitivity with BZ/BLT ratio is suggested to be related to the change in the crystal structure. Additionally, at temperatures below −50°C, the relative permittivity showed a significant increase under applied compressive stress

Mechanistic consequences of temperature on DNA polymerization catalyzed by a Y-family DNA polymerase

Our previous publication shows that Sulfolobus solfataricus Dpo4 utilizes an ‘induced-fit’ mechanism to select correct incoming nucleotides at 37°C. Here, we provide a comprehensive report elucidating the kinetic mechanism of a DNA polymerase at a reaction temperature higher than 37°C in an attempt to determine the effect of temperature on enzyme fidelity and mechanism. The fidelity of Dpo4 did not change considerably with a 30°C increase in reaction temperature, suggesting that the fidelity of Dpo4 at 80°C is similar to that determined here at 56°C. Amazingly, the incorporation rate for correct nucleotides increased by 18 900-fold from 2°C to 56°C, similar in magnitude to that observed for incorrect nucleotides, thus not perturbing fidelity. Three independent lines of kinetic evidence indicate that a protein conformational change limits correct nucleotide incorporations at 56°C. Furthermore, the activation energy for the incorporation of a correct nucleotide was determined to be 32.9 kcal/mol, a value considerably larger than those values estimated for a rate-limiting chemistry step, providing a fourth line of evidence to further substantiate this conclusion. These results herein provide evidence that Dpo4 utilizes the ‘induced-fit’ mechanism to select a correct nucleotide at all temperatures

Hairpin ribozyme-antisense RNA constructs can act as molecular lassos

We have developed a novel class of antisense agents, RNA Lassos, which are capable of binding to and circularizing around complementary target RNAs. The RNA Lasso consists of a fixed sequence derived from the hairpin ribozyme and an antisense segment whose size and sequence can be varied to base pair with accessible sites in the target RNA. The ribozyme catalyzes self-processing of the 5′- and 3′-ends of a transcribed Lasso precursor and ligates the processed ends to produce a circular RNA. The circular and linear forms of the self-processed Lasso coexist in an equilibrium that is dependent on both the Lasso sequence and the solution conditions. Lassos form strong, noncovalent complexes with linear target RNAs and form true topological linkages with circular targets. Lasso complexes with linear RNA targets were detected by denaturing gel electrophoresis and were found to be more stable than ordinary RNA duplexes. We show that expression of a fusion mRNA consisting of a sequence from the murine tumor necrosis factor-α (TNF-α) gene linked to luciferase reporter can be specifically and efficiently blocked by an anti-TNF Lasso. We also show in cell culture experiments that Lassos directed against Fas pre-mRNA were able to induce a change in alternative splicing patterns