The colony formation assay (CFA) is the gold standard for measuring cytotoxic effects on cells. To increase efficiency, the CFA was converted to a 96-well format using an automated colony counting algorithm. The 96-well CFA was validated using ionizing radiation (IR) on the FaDu and A549 cancer cell lines. Its ability to evaluate combination therapies was investigated using cisplatin and IR. The 96-well CFA was transferred to a robotic platform for evaluation as a high-throughput screen (HTS) readout for the discovery of novel anti-cancer compounds, and radiosensitizers. Screening yielded eight putative anti-cancer hits, and five putative radiosensitizing hits. Secondary screening confirmed 6/8 anti-cancer compounds, and 0/5 radiosensitizing compounds. Thus, the 96-well CFA can be adopted as an alternative assay to the 6-well CFA in the evaluation of cytotoxicity in vitro, providing a possible readout to be utilized in HTS for discovering anti-cancer compounds, but with limited applicability in discovering radiosensitizers.

Zugl.: Hamburg, Techn. Univ., Diss., 2008

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 210-232).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Darmstadt, Techn. Univ., Diss., 2005. / Dateien im PDF-Format

Universiẗat, Diss., 1999--Tübingen.

Techn. Universiẗat, Diss., 2004--Berlin.

Universiẗat, Diss., 2005--Jena.

Many pathogenic microorganisms are believed to stochastically switch into low metabolic states that display resistance to supra-lethal levels of antibiotics. These so-called “persister” cells have been associated with recurrent infections and the development of antibiotic resistance. Whilst a compound that eliminates Staphylococcus aureus persister cells has been described, it is not active against Gram-negative bacteria. The aim of my PhD project was to develop a high-throughput assay for compounds that eradicate persister cells in the -proteobacterium Burkholderia thailandensis. Further to this, I aimed to develop “hit” compounds from screening into lead series through investigation of structure activity relationships and, use a chemical genetics approach to elucidate potential mechanisms of action. I developed a phenotypic assay to identify compounds that eradicate persister cells. The assay was based on the reduction of the resazurin based dye PrestoBlue. Optimization of the assay gave a Z’ prime of 0.41 when screened in high throughput at the DDU. Screening of the library of 61,250 compounds identified 2,127 compounds that gave a statistically significant reduction in persister cell numbers. Follow-up assays highlighted 29 compounds with a pIC50 greater than five. Detailed investigation allowed me to down select to six “best in class” compounds, which included the licensed drug chloroxine. A time dependent killing assay showed that chloroxine reduced levels of persister cells by three orders of magnitude over 72 hours (P = 0.01). Hit expansion around chloroxine using commercially available compounds did not identify any more potent compounds, but did highlight key features of the molecule for activity. Assay protocols were provided to collaborators at DSTL who were able to iv show that chloroxine is also active against persister cells formed by the tropical pathogen and Tier 1 biological agent Burkholderia pseudomallei. Investigations into the mechanism of action of chloroxine used Next Generation Sequencing of an over expression library, identifying two putative genes involved in inhibition of persister cells by chloroxine. My findings demonstrate a phenotypic assay against persister cells in Gram-negative bacteria, which has the power to identify potent anti-persister agents to assist in chemotherapy. Structural activity relationship and mechanism of action investigations have indicated lead series and genetic starting points for future development of this research. My PhD project has concluded with sufficient data for continuation of research following a number of leads and is at an ideal stage for instigation of a medicinal chemistry program for development of chloroxine as a clinical option for treatment of persistent melioidosis.

Orientador: Anita Jocelyne Marsaioli / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-10T04:53:28Z (GMT). No. of bitstreams: 1 Mantovani_SimoneMoraes_M.pdf: 1495773 bytes, checksum: 493a0576675a8aad3c2879147aa7745f (MD5) Previous issue date: 2007 / Resumo: Nas últimas décadas as reações utilizando biocatalisadores tem sido amplamante aplicadas na síntese orgânica, como componentes chave de muitos processos químicos industriais, levando ao aumento na demanda por novas enzimas. A maneira mais rápida e simples de detectar enzimas é através de metodologias de triagem de alto desempenho (HTS) que permitam identificação rápida da atividade enzimática, como por exemplo, os ensaios utilizando compostos fluorogênicos e cromogênicos. Nesse trabalho nós aplicamos HTS baseado em substratos fluorogênicos para detecção de epóxido-hidrolases e esterases em microrganismos brasileiros. Inicialmente foram selecionados cinco microrganismos com alta atividade epóxido-hidrolase, e 18 pela a presença de esterases. Inspirados nesse principio nós adaptamos a metodolgia conhecida como "Quick E" para a avaliação rápida das enantiosseletividades de epóxido-hidrolases em células íntegras através de medidas das velocidades iniciais de substratos fluorogênicos quirais avaliados separadamente com adição de um competidor. Os ensaios de enantiosseletividade mostraram que os experimentos com competidor apresentaram valores de enatiosseletividade muito próximos dos valores de E determinados via biocatálise convencional. Além disso, alguns microrganismos selecionados por HTS foram testados para reações de biotransformação frente a substratos de interesse sintético, o que permitiu, além da confirmação das atividades enzimáticas e seletividades observadas, detectar a capacidade do microrganismo C. albícans CCT 0776 de desracemizar álcoois secundários por estereoinversão, fornecendo o (S)-1,2-octanodiol com 100 % de rendimento teórico e ee > 99 %, e o (S)-4-fenilmetoxi-1,2-butanodiol com ee 45 % / Abstract: Since the past decades the biocatalysts have been applied in organic chemistry, as key components of many industrial chemical processes, thus increasing the demand for novel enzymes. High-Throughput Screening (HTS), using fluorogenic probes are among the best assays to discovery new enzymes, easily adapted to whole cells format. In this work, have been applied fluorogenic probes to screen epoxide hydrolases and esterases in Brazilian Collection Cultures of microorganisms, which allowed to detect epoxide hydrolases in five microorganisms, and esterases in 18 microrganisms. Additionally, were used chiral probes to implement a Quick E assay, for a fast valuation of epoxide hydrolases enantioselectivity by measuring initial rates of pure enantiomers. Optimization of the methodology revealed that almost true E were obtained by competitive experiments of each enantiomer and a substrate of similar reactivity. The quick E assay was validated by determining conversion and ee using GC/MS and NMR (using mandelic acid derivatives) and is now a new method to determine the enantiomeric ratio for epoxide hidrolases. Finally, the outstanding HTS results were better investigated by conventional catalysis detecting a stereoinversion process performed by C. albicans CCT 0776, which furnished (S)-1 ,2-octanodiol in 100 % theoretical yield and ee of 100%, and (S)-4-fenilmetoxi-1,2-butanodiol in ee of 45% / Mestrado / Quimica Organica / Mestre em Química