Development of In vitro Multi-Species Biofilms to Explore Strategies to Prevent Biofilm-Associated Oral Diseases

More than 80% of infectious diseases are caused by microbial biofilms. In the oral cavity, biofilms are composed of hundreds of distinct bacteria. The accumulation of oral biofilms can lead to caries and periodontal disease. From a public health standpoint, the cost of treatment for oral diseases remain high, at over $100 billion dollars per year in US alone. The primary aim of this project was to evaluate new anti-biofilm agents using novel in vitro biofilm model systems. In addition, the biology of oral biofilms and their relationship to oral diseases are discussed in the context of their development in laboratory biofilm model systems. Nisin is a unique bacteriocin generated by a group of Lactococcus and Streptococcus species. The objective of the first part of the work was to determine if nisin exhibited broad-spectrum antimicrobial effects against oral bacteria. In addition, the presented work showed that nisin inhibited the growth and maintenance of saliva derived biofilms developed in static and controlled-flow biofilm model systems. Even at higher concentrations, nisin did not exhibit cytotoxic effects on human oral cells. L-arginine is an amino acid that is present in low levels in the oral cavity. At lower concentrations, L-arginine is a nutrient source for arginolytic bacteria. The objective of the second part of the work was to explore the short-term effects of high concentrations of L-arginine on oral biofilms. A modified Swinnex model system was used to develop the multi-species oral biofilms and the FlowCam® was used to monitor the biofilm dispersion. In a dose-dependent manner, L-arginine treatment resulted in biofilm destabilization through enhanced biofilm dispersion. Based on community analyses of the biofilms and the dispersed cells, L-arginine did not result a significant shift in the community compared to the water-treated controls. In summary, the work presented in this thesis demonstrated that complex biofilms, that contain species present in the human oral cavity, can be developed using three different in vitro biofilm model systems. In addition, we showed that nisin and L-arginine has high potential to disrupt the in vitro developed multi-species biofilms and these compounds have potential as novel anti-biofilm agents.PHDOral Health SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138465/1/jaemshin_1.pd

Microencapsulation of imidazole curing agent by solvent evaporation method using W/O/W emulsion

The epoxy–imidazole resin system is used to form the anisotropic conducting film. The latent character of the system is very significant. In this study, imidazole (Im) or 2‐methylimidazole (2MI) was encapsulated for the latent curing system to use in the reaction of epoxy resin. Polycaprolactone was used as a wall material, and the solvent evaporation method was used to form the microcapsule using W/O/W emulsion. The shelf life of the microcapsules was studied for the epoxy resin, and the curing behavior of the microcapsules for epoxy resin was examined using a differential scanning calorimeter. The curing times at 150 and 180°C were estimated using an indentation method. The microcapsules of Im or 2MI exhibited a long shelf life for epoxy resin. When comparing the results of the previous methods with the results of this study using the W/O/W emulsion, finer microcapsules were formed and the microcapsule has longer shelf life. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98341/1/38767_ftp.pd

PDB-Ligand: a ligand database based on PDB for the automated and customized classification of ligand-binding structures

PDB-Ligand (http://www.idrtech.com/PDB-Ligand/) is a three-dimensional structure database of small molecular ligands that are bound to larger biomolecules deposited in the Protein Data Bank (PDB). It is also a database tool that allows one to browse, classify, superimpose and visualize these structures. As of May 2004, there are about 4870 types of small molecular ligands, experimentally determined as a complex with protein or DNA in the PDB. The proteins that a given ligand binds are often homologous and present the same binding structure to the ligand. However, there are also many instances wherein a given ligand binds to two or more unrelated proteins, or to the same or homologous protein in different binding environments. PDB-Ligand serves as an interactive structural analysis and clustering tool for all the ligand-binding structures in the PDB. PDB-Ligand also provides an easier way to obtain a number of different structure alignments of many related ligand-binding structures based on a simple and flexible ligand clustering method. PDB-Ligand will be a good resource for both a better interpretation of ligand-binding structures and the development of better scoring functions to be used in many drug discovery applications

Delayed presentation of cerebellar and spinal cord infarction as a complication of computed tomography-guided transthoracic lung biopsy: a case report

INTRODUCTION: Computed tomography-guided transthoracic needle biopsy is a common diagnostic procedure that is associated with various complications including pneumothorax, parenchymal hemorrhage, and hemoptysis. A systemic air embolism is a very rare (0.06 to 0.21%) but potentially fatal complication. CASE PRESENTATION: A 70-year-old Korean male was admitted to our hospital for evaluation of a solitary pulmonary nodule located adjacent to the right inferior pulmonary vein in the medial basal segment of the right lower lobe. A computed tomography-guided needle biopsy was performed by a radiologist using a coaxial needle. A computed tomography image obtained immediately after the biopsy showed intraluminal free air in the proximal ascending aorta. He complained of a mild electrical current sensation in both lower extremities. After three hours he complained of neurological deficit in both lower extremities as well as voiding difficulty. The brain and spine magnetic resonance images showed a right cerebellar and spinal cord infarction at the T8-10 levels. CONCLUSIONS: We report a case of air embolism to the cerebellum and spinal cord causing infarction presenting with an initial symptom of mild electrical current sensation in both lower extremities during the transthoracic needle biopsy. For this potentially fatal complication, early recognition, followed by prompt therapy is critical to reducing morbidity and mortality

Micro-nano hybrid structures with manipulated wettability using a two-step silicon etching on a large area

Nanoscale surface manipulation technique to control the surface roughness and the wettability is a challenging field for performance enhancement in boiling heat transfer. In this study, micro-nano hybrid structures (MNHS) with hierarchical geometries that lead to maximizing of surface area, roughness, and wettability are developed for the boiling applications. MNHS structures consist of micropillars or microcavities along with nanowires having the length to diameter ratio of about 100:1. MNHS is fabricated by a two-step silicon etching process, which are dry etching for micropattern and electroless silicon wet etching for nanowire synthesis. The fabrication process is readily capable of producing MNHS covering a wafer-scale area. By controlling the removal of polymeric passivation layers deposited during silicon dry etching (Bosch process), we can control the geometries for the hierarchical structure with or without the thin hydrophobic barriers that affect surface wettability. MNHS without sidewalls exhibit superhydrophilic behavior with a contact angle under 10°, whereas those with sidewalls preserved by the passivation layer display more hydrophobic characteristics with a contact angle near 60°