Complications during the healing process of skin wounds often arise due to infection by pathogenic bacteria. Bacterial hydrolytic enzymes degrade the host tissue while biofilms can shield the bacterial cells from the host's immune response. Wound dressings with bacteriostatic or bactericidal properties are a promising solution. This study investigated the potential of surface acetylated bacterial cellulose as a novel antibacterial wound dressing. Hydroxyl groups on the surface of bacterial cellulose were substituted with acetyl groups using acetic anhydride in a citric acid-catalyzed reaction. The resulting ester linkages between the acetyl groups and bacterial cellulose surface were hypothesized to be cleaved by bacterial esterases or other hydrolytic enzymes such that acetic acid, a well-known antibacterial compound, will be produced leading to the death of the bacterial cells. Surface acetylation was confirmed via FTIR and its effect on the morphology of bacterial cellulose was analyzed with FESEM and XRD while the degree of substitution was determined by HPLC-UV. Indirect contact human cell cytotoxicity assays using extracts from surface acetylated bacterial cellulose showed no cytotoxic effect on human umbilical vein endothelial cells. Two types of antibacterial assays were performed in which surface acetylated bacterial cellulose was exposed to Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa which were selected as model bacteria for Gram-positive, Gram-negative, and pathogenic bacterial species, respectively. Neither assay showed a reduction of bacterial cell viability. Further research is needed to determine if the acetyl ester linkages on the surface of bacterial cellulose are susceptible to cleavage by bacterial esterase enzymes. / Master of Science / The healing of skin wounds is frequently complicated by infection of the wound with harmful bacteria. A potential remedy could be wound dressings that kill such bacteria. Bacterial cellulose is a naturally occurring biomaterial with multiple properties that make it an ideal material for wound dressings. Pure bacterial cellulose has no inherent antibacterial properties but can be chemically modified with a separate substance that is antibacterial such as acetic acid. This study investigates the potential of chemically modified bacterial cellulose in antibacterial wound dressing applications. The material may release acetic acid in the presence of bacteria and cause cell death. A series of human cell and antibacterial assays were carried out to test the ability of the modified bacterial cellulose to inhibit bacterial growth as well as any potential harmful effect on human cells. While it showed no adverse effects on human cells, the modified bacterial cellulose did not reduce bacterial cell viability.

Triclosan is a widely used antibacterial agent found in many personal hygiene products. While it has been established that pure triclosan and free chlorine readily react, interactions between triclosan-containing products and free chlorine have not previously been analyzed. Sixteen double-blinded solutions including both triclosan-containing (1.14-3.12 mg triclosan/g product) and triclosan-free products were contacted with free chlorine. Products detected included (chlorophenoxy)phenols, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and chloroform. The daughter product yields were found to be highly variable and were dependent on the antimicrobial product investigated, the free chlorine to triclosan ratio, and the temperature at which the study was conducted. Lowering the temperature from 40 to 30 oC resulted in a decreased yield from 0.50 to 0.37 moles chloroform/mole triclosan after 1 minute of reaction time with [HOCl]initial = 4.0 mg/L as Cl2. Chloroform molar yields decreased to 0.29 when the initial chlorine concentration was reduced to 2.0 mg/L for a constant temperature of 40 oC. Field experiments, in which Atlanta and Danville tap waters were augmented with various soap products, exhibited differential results from the laboratory experiments in that different product yields were observed. These differences are attributed to the chlorine demand of constituents in the tap water. Higher chlorine to triclosan ratios tend to produce high levels of chloroform, while lower chlorine to triclosan ratios tend to form higher amounts of chlorophenols and (chlorophenoxy)phenol intermediates. The results from this study suggest that the chloroform produced by these reactions can be substantial under some conditions. / Master of Science

No

Smart nanomaterials can selectively respond to a stimulus and consequently be activated in specific conditions, as a result of their interaction with electromagnetic radiation, biomolecules, pH change, etc. These nanomaterials can be produced through distinct routes and be used in artificial skin, drug delivery, and other biomedical applications. In this thesis, two smart nanosystems were developed, viz., i) nanocapsules formed by aniline (A) and chitosan (CS) (A-CS) containing silver nanoparticles (AgNPs), with an average size of 78 ± 19 nm, and ii) polycaprolactone (PCL) nanofibers, fabricated by the electrospinning technique containing AgNP into their bulk, with a diameter of 417 ± 14 nm. A novel system, based on the incorporation of the as-prepared nanocapsules onto the surface of PCL nanofibers containing AgNps (antibacterial mats), was also developed. The methodology employed avoids the direct contact of silver nanoparticles with the host and optimizes its release to the surrounding environment. The AgNPs release was triggered by exposing the nanocapsules to light at 405 nm. Consequently, the electronic energy vibration resulting from the interaction of the irradiation with the surface plasmon band (SPR) of AgNps, breaking the hydrogen bonds of the nanocapsules and releasing of AgNPs at a time of 150 s. To understand the perturbation of AgNps-Nanocapsules against bacteria, membrane models using Langmuir technique with the phospholipids 1,2-dipalmitoyl-sn-glycero-3-phospho-(1\'-rac-glycerol) (DPPG) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) were employed, which are the main components of cell membrane of Escherichia coli (E. coli). The results suggest that DPPG has more influence on the incorporation of the nanoparticles on the cell membrane. The antibacterial properties of the nanofibers/nanomaterials mats towards E. coli and Staphylococcus aureus (S. aureus) were investigated using the Agar diffusion test for 8 samples. The experiments revealed that the samples based on nanofibers/nanocapsules and irradiation presented a radius of inhibition of 2.58 ± 0.28 mm for S. aureus and 1.78 ± 0.49 mm for E. coli. This nanosystem showed to be highly interesting for biomedical applications. / Nanomateriais inteligentes podem responder seletivamente a um estímulo e consequentemente ser ativados em condições específicas, como resultado da sua interação com a radiação eletromagnética, mudança do pH, campo magnético, etc. Esses materiais podem ser produzidos através de distintas rotas e utilizados em aplicações como pele artificial, liberação de fármacos, e outras aplicações biomédicas. Nessa tese, dois nanossistemas inteligentes foram desenvolvidos, a saber: i) nanocápsulas formadas por anilina (A) e quitosana (CS) (A-CS) contendo nanopartículas de prata (AgNps), com um tamanho médio de 78 ± 19 nm, e ii) nanofibras de policaprolactona (PCL), fabricadas pela técnica de eletrofiação contendo AgNps em seu interior, com diâmetro de 417 ± 14 nm. Um terceiro sistema foi desenvolvido, baseado na incorporação das nanocápsulas na superfície das nanofibras de PCL contendo AgNps (manta antibacteriana). A metodologia utilizada evita o contato direto das nanopartículas de prata com o hospedeiro e otimiza sua liberação no meio ambiente. As AgNps liberadas foram acionadas pela exposição das nanocápsulas à um fonte de luz em 405 nm. Consequentemente, a vibração da energia eletrônica resultante da interação da irradiação com a banda plasmônica de superfície (SPR) das AgNps, quebra as ligações de hidrogênio da nanocápsula e libera as AgNps no meio em um tempo de 150 s. Para entender a perturbação das AgNps-nanocapsulas contra as bactérias, modelos de membrana foram usados através da técnica de Langmuir com os fosfolipídios 1,2-dipalmitoil-sn-glicero-3- fosfo-(1\'-rac-glicerol) (DPPG) and 1,2-dimiristoil-sn-glicero-3-fosfoetanolamina (DMPE), que são os principais componentes da membrana celular de Escherichia coli (E. coli). Os resultados sugerem que DPPG tem mais influência na incorporação das nanopartículas na membrana celular. As propriedades antibacterianas das mantas de nanofibras/nanomateriais contra E. coli e Staphylococus aureus (S. aureus) foram investigadas usando o teste de difusão Agar em 8 grupos, o qual revelou que o grupo contendo a nanofibra/nanocapsula e irradiação apresentou um raio de inibição de 2.58 ± 0.28 mm para S. aureus e 1.78 ± 0.49 mm para E. coli. Este nanossistema mostrou ser altamente interessante para aplicações biomédicas.

La corrosión del concreto es uno de los principales problemas de deterioro y pérdida de funcionalidad que puede llevar al colapso parcial o total de una estructura. En los sistemas de alcantarillado existe un proceso denominado Corrosión Microbiana Inducida, el cual es causado por la acción del consorcio de bacterias presentes en las aguas residuales, las mismas que generan ácido sulfúrico como parte de su metabolismo. El trabajo experimental desarrollado comienza con la preparación y muestreo de un diseño de concreto patrón y tres de concreto antibacterial con diferente dosificación de Aditivo Antimicrobial, los cuales fueron evaluados por un ensayo microbiológico. En esta etapa se determinó la dosis de aditivo con la que se realizarán nuevos diseños. Como alternativa de solución frente al ataque de ácido sulfúrico se realizó en laboratorio la preparación y muestreo de seis diseños de concreto, para los cuales se establece algunas variables de estudio: relación agua/cemento y porcentaje de adición mineral Filler Calizo. Las propiedades del concreto se evaluaron mediante ensayos en estado endurecido. Asimismo, se determinó la resistencia del concreto frente a concentraciones de 3%, 5% y 7% de ácido sulfúrico; el rendimiento se evaluó mediante la pérdida de peso. Finalmente, se realizó una evaluación económica en base a un proyecto de Saneamiento, en el cual se determinó el presupuesto para la construcción de buzones considerando los costos del concreto patrón y antibacterial elegido. Para determinar la rentabilidad económica se consideró los costos por mantenimiento para un periodo de análisis de 20 años. / The experimental work developed begins with the preparation and sampling of a single concrete pattern design and three antibacterial concrete designs with different dosage of Antimicrobial Additive, which are evaluated through a microbiological test. This consists in the exposure of the concrete samples at the consortium of bacteria present in a wastewater treatment plant. The effectiveness of the additive under study was determined by a visual analysis of the coloration, pH variation and then compared to the results of the concrete pattern design. As an alternative solution for sulfuric acid attack, the preparation, sampling and control of six concrete designs was carried out in laboratory, for which some study variables were established: the water / cement ratio and the mineral addition percentage of Filler Limestone. The durability of the concrete was evaluated by hardened destructive and non-destructive tests. Likewise, the resistance of the concrete was determined against concentrations of 3%, 5% and 7% of sulfuric acid, for an exposure time of 4 and 8 weeks and analyzed by the weight loss. Finally, an economic evaluation was carried out based on a sanitary project, in which the budget for the construction of mailboxes was determined considering the costs of the standard and antibacterial concrete previously chosen. To determine the benefit, a schedule was established with the items of preventive and corrective maintenance according to the frequency and necessity of each design. The results were presented through a flow of expenditures for a period of analysis of 20 years. / Tesis

Publics are facing a great challenge of infections from pathogens. Polyethylene terephthalate (PET) is widely used in health-care settings. It is vital to develop effective and regenerable antimicrobial PET. In this study, effective antibacterial modification of PET was achieved by immobilizing N-halamine biocide poly (N-chloroacrylamide) (PCA) onto PET through the formation of a surface interpenetrating network. The successful and uniform immobilization was confirmed by FTIR and XPS. The immobilization is durable to a 72 hours soxhlet extraction. Surface morphology of the fabrics did not significantly change after modification with IP less than 20%. The modified fabric can bring 100% reduction of 10e6 CFU/ml of several clinical important bacteria in 15 min contact. The regenerability of N-halamine on PAM modified PET was studied by FTIR, titration and N analysis. After 30 regeneration cycles, the PAM-DVB network modified PET was still able to provide 100% reduction of HA-MRSA in 20 min contact.

Publics are facing a great challenge of infections from pathogens. Polyethylene terephthalate (PET) is widely used in health-care settings. It is vital to develop effective and regenerable antimicrobial PET. In this study, effective antibacterial modification of PET was achieved by immobilizing N-halamine biocide poly (N-chloroacrylamide) (PCA) onto PET through the formation of a surface interpenetrating network. The successful and uniform immobilization was confirmed by FTIR and XPS. The immobilization is durable to a 72 hours soxhlet extraction. Surface morphology of the fabrics did not significantly change after modification with IP less than 20%. The modified fabric can bring 100% reduction of 10e6 CFU/ml of several clinical important bacteria in 15 min contact. The regenerability of N-halamine on PAM modified PET was studied by FTIR, titration and N analysis. After 30 regeneration cycles, the PAM-DVB network modified PET was still able to provide 100% reduction of HA-MRSA in 20 min contact.

Smart nanomaterials can selectively respond to a stimulus and consequently be activated in specific conditions, as a result of their interaction with electromagnetic radiation, biomolecules, pH change, etc. These nanomaterials can be produced through distinct routes and be used in artificial skin, drug delivery, and other biomedical applications. In this thesis, two smart nanosystems were developed, viz., i) nanocapsules formed by aniline (A) and chitosan (CS) (A-CS) containing silver nanoparticles (AgNPs), with an average size of 78 ± 19 nm, and ii) polycaprolactone (PCL) nanofibers, fabricated by the electrospinning technique containing AgNP into their bulk, with a diameter of 417 ± 14 nm. A novel system, based on the incorporation of the as-prepared nanocapsules onto the surface of PCL nanofibers containing AgNps (antibacterial mats), was also developed. The methodology employed avoids the direct contact of silver nanoparticles with the host and optimizes its release to the surrounding environment. The AgNPs release was triggered by exposing the nanocapsules to light at 405 nm. Consequently, the electronic energy vibration resulting from the interaction of the irradiation with the surface plasmon band (SPR) of AgNps, breaking the hydrogen bonds of the nanocapsules and releasing of AgNPs at a time of 150 s. To understand the perturbation of AgNps-Nanocapsules against bacteria, membrane models using Langmuir technique with the phospholipids 1,2-dipalmitoyl-sn-glycero-3-phospho-(1\'-rac-glycerol) (DPPG) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) were employed, which are the main components of cell membrane of Escherichia coli (E. coli). The results suggest that DPPG has more influence on the incorporation of the nanoparticles on the cell membrane. The antibacterial properties of the nanofibers/nanomaterials mats towards E. coli and Staphylococcus aureus (S. aureus) were investigated using the Agar diffusion test for 8 samples. The experiments revealed that the samples based on nanofibers/nanocapsules and irradiation presented a radius of inhibition of 2.58 ± 0.28 mm for S. aureus and 1.78 ± 0.49 mm for E. coli. This nanosystem showed to be highly interesting for biomedical applications. / Nanomateriais inteligentes podem responder seletivamente a um estímulo e consequentemente ser ativados em condições específicas, como resultado da sua interação com a radiação eletromagnética, mudança do pH, campo magnético, etc. Esses materiais podem ser produzidos através de distintas rotas e utilizados em aplicações como pele artificial, liberação de fármacos, e outras aplicações biomédicas. Nessa tese, dois nanossistemas inteligentes foram desenvolvidos, a saber: i) nanocápsulas formadas por anilina (A) e quitosana (CS) (A-CS) contendo nanopartículas de prata (AgNps), com um tamanho médio de 78 ± 19 nm, e ii) nanofibras de policaprolactona (PCL), fabricadas pela técnica de eletrofiação contendo AgNps em seu interior, com diâmetro de 417 ± 14 nm. Um terceiro sistema foi desenvolvido, baseado na incorporação das nanocápsulas na superfície das nanofibras de PCL contendo AgNps (manta antibacteriana). A metodologia utilizada evita o contato direto das nanopartículas de prata com o hospedeiro e otimiza sua liberação no meio ambiente. As AgNps liberadas foram acionadas pela exposição das nanocápsulas à um fonte de luz em 405 nm. Consequentemente, a vibração da energia eletrônica resultante da interação da irradiação com a banda plasmônica de superfície (SPR) das AgNps, quebra as ligações de hidrogênio da nanocápsula e libera as AgNps no meio em um tempo de 150 s. Para entender a perturbação das AgNps-nanocapsulas contra as bactérias, modelos de membrana foram usados através da técnica de Langmuir com os fosfolipídios 1,2-dipalmitoil-sn-glicero-3- fosfo-(1\'-rac-glicerol) (DPPG) and 1,2-dimiristoil-sn-glicero-3-fosfoetanolamina (DMPE), que são os principais componentes da membrana celular de Escherichia coli (E. coli). Os resultados sugerem que DPPG tem mais influência na incorporação das nanopartículas na membrana celular. As propriedades antibacterianas das mantas de nanofibras/nanomateriais contra E. coli e Staphylococus aureus (S. aureus) foram investigadas usando o teste de difusão Agar em 8 grupos, o qual revelou que o grupo contendo a nanofibra/nanocapsula e irradiação apresentou um raio de inibição de 2.58 ± 0.28 mm para S. aureus e 1.78 ± 0.49 mm para E. coli. Este nanossistema mostrou ser altamente interessante para aplicações biomédicas.

Indiana University-Purdue University Indianapolis (IUPUI) / The furanone derivatives and their constructed polymers were synthesized, characterized and formulated into dental glass-ionomer cement (GIC) and resin composite for improved antibacterial properties. Compressive strength (CS) and S. mutans viability were used to evaluate the mechanical strength and antibacterial activity of the restoratives. Fuji II LC cement and P60 were used as control. The specimens were conditioned in distilled water at 37 oC for 24 h prior to testing. The effects of loading, saliva and aging on CS and S. mutans viability were investigated. The antibacterial effect of the furanone derivative on other bacteria was also studied. Chapter 2 describes how we studied and evaluated the formulated antibacterial glass-ionomer cement by incorporating the synthesized furanone derivative-containing polymer into the formulation. The results show that all the formulated furanone-containing cements showed a significant antibacterial activity, accompanying with an initial CS reduction. Increasing loading significantly enhanced antibacterial activity but reduced the initial CS of the formed cements. The derivative showed a broad antibacterial spectrum on bacteria including S. mutans, lactobacillus, S. aureus and S. epidermidis. Human saliva did not affect the antibacterial activity of the cement. The long-term aging study indicates that the cements may have a long-lasting antibacterial function. Chapter 3 describes how we studied and evaluated the formulated antibacterial resin composite by incorporating the synthesized furanone derivative into the basic resin formulations. The results show that the modified resin composites showed a significant antibacterial activity without substantially decreasing the mechanical strengths. With 5 to 30% addition of the furanone derivative, the composite kept its original CS unchanged but showed a significant antibacterial activity with a 16-68% reduction in the S. mutans viability. Further, the antibacterial function of the new composite was not affected by human saliva. The aging study indicates that the composite may have a long-lasting antibacterial function. In summary, we have developed a novel furanone-containing antibacterial system for dental restoratives. Both glass-ionomer cement and resin composite have demonstrated significant antibacterial activities. The modified experimental glass-ionomer cement is a promising system because the reduced strength of the cement with addition of the furanone-containing polymer is still above those demonstrated by original commercial cement Fuji II LC. The modified resin composite shows nearly no reduction in mechanical strength after incorporation of the antibacterial furanone derivative. It appears that both experimental cement and resin composite are clinically attractive dental restoratives that can be potentially used for long-lasting restorations due to their high mechanical strength and permanent antibacterial function.

Thiopeptides are posttranslationally-processed macrocyclic peptide metabolites, characterized by extensive backbone and side chain modifications that include a six-membered nitrogenous ring, thioazol(in)e/oxazol(in)e rings, and dehydrated amino acid residues. Thiostrepton A, produced by Streptomyces laurentii ATCC 31255, is one of the more structurally complex thiopeptides, containing a second macrocycle bearing a quinaldic acid. Thiostrepton A and other thiopeptides are of great interest due to their potent activities against emerging antibiotic-resistant Gram-positive pathogens, in addition to their antimalarial and anticancer properties. The ribosomal origins for thiopeptides have been established, however, few details are known concerning the posttranslational modification steps. Alteration to the primary amino acid sequence of the precursor peptide provides an avenue to probe the substrate specificity of the thiostrepton A posttranslational machinery. The information gathered from current studies can also be used to refine thiostrepton’s structure-activity relationship, providing insight into the key features of its scaffold that impart specificity toward each biological target. A fosmid-dependent biosynthetic engineering platform for thiostrepton A was developed and a series of thiostrepton analogs were successfully produced adapting this method. The seventh residue of thiostrepton A is predicted to be critical for the metabolite’s antibacterial activity. Our results were consistent this hypothesis and demonstrated that substitution of Thr7 in the thiostrepton A precursor peptide disrupts both biological activity and successful biosynthesis of the analogs. The thiostrepton biosynthetic machinery’s tolerances toward structural variation at the second and fourth positions of the TsrA core peptide were probed by the saturation mutagenesis of Ala2 and Ala4, respectively. Eight thiostrepton Ala2 variants were isolated with two analogs truncated at the N-terminus by one amino acid, bearing a shortened quinaldic acid-containing macrocycle. Our results suggested that the identity of the core peptide second residue influences the biosynthesis of a thiostrepton analog, however, not essential for the antibacterial and proteasome inhibitory activities of the full-length variants. Additionally, the quinaldic acid loop size affects thiostrepton’s antibacterial potency, but is not critical for the proteasome inhibitory activity. Sixteen thiostrepton analogs were isolated from Ala4 mutagenesis studies. We demonstrated that the identity of the amino acid residue at the fourth position in the thiostrepton scaffold is not critical to inhibit either the ribosome or the proteasome in vitro.