Transcutaneous Ultrasound Loading of Piezoelectric-Driven Hernia Repair Mesh For Soft Tissue Healing

Annually in the United States, over one million hernia repairs surgeries occur. A hernia is a painful medical impediment where a portion of soft tissue protrudes through a damaged section of abdominal wall. The only real treatment for hernias is to repair and strengthen the injured abdominal lining. Hernias have a high recurrence rate which leads to surgeons utilizing surgical mesh to help strength the repair and reduce the recurrence rate. However, the use of synthetic mesh in hernia repairs can lead to recurrence rates due to rips or tears along the tissue and biomaterial interface, which leads to additional patient discomfort and difficulties. The recurrence rate for the first-time open hernia repair is 24% even with the use of a hernia repair mesh.1 Any patient can develop a hernia in their lifetime no matter age, physical condition, or demographic however, certain risk factors can increase a patient’s chances of a hernia occurrence such as obesity, tobacco use, and heavy lifting. Electrical stimulation (ES) for soft tissue repair and regeneration has shown promise in low voltage applications. However, for internal soft tissue regeneration, battery packs would be cumbersome and may require additional surgeries for removal. Low voltage can be made possible through piezoelectric discs that have the unique property of producing current through mechanical loading and thus does not need a battery pack. Therefore, a method of using ES as a conduit for soft tissue regeneration has been proposed. This novel biomedical product concept and the resulting viability will be explored in this thesis work. The piezoelectric-driven hernia repair mesh was assessed through biocompatibility and viability outcomes. Here, the hernia repair mesh was turned into an electrode through applying a thin layer of gold by sputter coating. The voltage source was a piezoelectric element that was activated through transcutaneous ultrasound loading to provide better healing prospects. The results from this study show viability of NIH 3T3 cells in vitro after 5-, 7-, and 14-days of stimulation. Overall viability results showed promise for the product concept after 5- and 7-days of stimulation. An unexpected complication in the electrode arose in the 14-day stimulation group. Limitations of the work and future work is discussed

Reverse engineering of fatty acid-tolerant Escherichia coli identifies design strategies for robust microbial cell factories

Adaptive laboratory evolution is often used to improve the performance of microbial cell factories. Reverse engineering of evolved strains enables learning and subsequent incorporation of novel design strategies via the design-build-test-learn cycle. Here, we reverse engineer a strain of Escherichia coli previously evolved for increased tolerance of octanoic acid (C8), an attractive biorenewable chemical, resulting in increased C8 production, increased butanol tolerance, and altered membrane properties. Here, evolution was determined to have occurred first through the restoration of WaaG activity, involved in the production of lipopolysaccharides, then an amino acid change in RpoC, a subunit of RNA polymerase, and finally mutation of the BasS-BasR two component system. All three mutations were required in order to reproduce the increased growth rate in the presence of 20 mM C8 and increased cell surface hydrophobicity; the WaaG and RpoC mutations both contributed to increased C8 titers, with the RpoC mutation appearing to be the major driver of this effect. Each of these mutations contributed to changes in the cell membrane. Increased membrane integrity and rigidity and decreased abundance of extracellular polymeric substances can be attributed to the restoration of WaaG. The increase in average lipid tail length can be attributed to the RpoCH419P mutation, which also confers tolerance to other industrially-relevant inhibitors, such as furfural, vanillin and n-butanol. The RpoCH419P mutation may impact binding or function of the stringent response alarmone ppGpp to RpoC site 1. Each of these mutations provides novel strategies for engineering microbial robustness, particularly at the level of the microbial cell membrane.This is a manuscript of an article published as Chen, Yingxi, Erin E. Boggess, Efrain Rodriguez Ocasio, Aric Warner, Lucas Kerns, Victoria Drapal, Chloe Gossling, Wilma Ross, Richard L. Gourse, Zengyi Shao, Julie Dickerson, Thomas J. Mansell, and Laura R. Jarboe. "Reverse engineering of fatty acid-tolerant Escherichia coli identifies design strategies for robust microbial cell factories." Metabolic Engineering (2020). DOI: 10.1016/j.ymben.2020.05.001. Posted with permission.</p