Enlargement of adipocytes in obesity leads to alteration in adipokine production and these changes are linked to the development of obesity-related cardiovascular diseases. Adipokines specifically associated with obesity-related hypertension include angiotensinogen and adiponectin. Conjugated linoleic acid (CLA) has been reported to reduce blood pressure in obese insulin-resistant rats, but its mechanism of action has not been identified. The objective of this study was to determine whether CLA’s ability to improve obesity-related hypertension involves reducing adipocyte size and altering adipokine production. Fa/fa Zucker rats (6 or 16 week old) were fed diets containing CLA isomers for 8 weeks. The trans(t)10,cis(c)12-CLA isomer reduced adipocyte size in both younger and older rats. Despite beneficial changes in cell size of rats fed the t10,c12-CLA isomer, there were no changes in the renin-angiotensin system or pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 or the anti-inflammatory cytokine IL-10. In contrast, the t10,c12-CLA isomer increased adiponectin levels both in the circulation and in adipose tissue. This was associated with increased phosphorylation of endothelial nitric oxide synthase (eNOS) in adipose tissue and aorta. Direct treatment of CLA isomers in cultured endothelial cells did not increase eNOS phosphorylation but increases were observed with adiponectin treatment. In vivo, infusion with adiponectin increased eNOS phosphorylation in adipose of fa/fa Zucker rats in parallel with improvements in blood pressure. Similarly, when circulating levels of adiponectin increased in rats fed the t10,c12-CLA isomer diet, blood pressure was also attenuated. In younger rats, both the t10-c12 and c9,t11-CLA isomers were significantly different from the control group at week 8, however, only the t10,c12-CLA isomer was comparable to the commonly used anti-hypertensive medication captopril. In conclusion, the beneficial effects of the t10,c12-CLA isomer on blood pressure may in part be due to its ability to reduce the number of large adipocytes in vivo, thus increasing the production of adiponectin which subsequently activates vascular eNOS.

Diabetic cardiomyopathy is defined as changes in the structure and function of the myocardium that occur in diabetic patients in the absence of other cardiovascular risk factors. Our laboratory has shown that conjugated linoleic acid (CLA - a naturally-occurring polyunsaturated fatty acid with multiple health benefits) prevents endothelin-1-induced myocyte hypertrophy in vitro, as well as cardiac hypertrophy in vivo using a rodent model of spontaneously hypertensive heart failure. These cardioprotective effects of CLA were mediated through activation of peroxisome proliferator activated receptors (PPAR isomers α and γ) and stimulation of diacylglycerol kinase ζ (DGKζ). Thus, the aims of this study were to (i) determine the effect of CLA on hyperglycemia-induced structural and functional abnormalities of cardiomyocytes, and (ii) assess the role of PPAR-γ and DGK. High glucose treatment induced hypertrophy of primary adult cardiomyocytes, as indicated by augmented cell size and protein synthesis compared to untreated cardiomyocytes. The hyperglycemia-induced hypertrophy was attenuated by pretreatment with CLA (30 µM). The ability of CLA to prevent hyperglycemia-induced hypertrophy was suppressed by GW9662 (1 µM) and R59022 (10 μM), pharmacological inhibitors of PPAR-γ and DGK, respectively. In addition to structural abnormalities, high glucose impaired contractile function of adult cardiomyocytes as measured by maximal velocity of shortening, maximal velocity of relengthening, and peak shortening. Hyperglycemia-induced contractile dysfunction was likewise prevented by pretreatment with CLA (30 µM). Collectively, these findings support the idea that hyperglycemia is an independent risk factor for the development of diabetic cardiomyopathy. Hypertrophy and contractile dysfunction elicited by high glucose were prevented by CLA. The antihypertrophic actions of CLA are mediated, at least in part, by activation of PPAR-γ and DGK.

Enlargement of adipocytes in obesity leads to alteration in adipokine production and these changes are linked to the development of obesity-related cardiovascular diseases. Adipokines specifically associated with obesity-related hypertension include angiotensinogen and adiponectin. Conjugated linoleic acid (CLA) has been reported to reduce blood pressure in obese insulin-resistant rats, but its mechanism of action has not been identified. The objective of this study was to determine whether CLA’s ability to improve obesity-related hypertension involves reducing adipocyte size and altering adipokine production. Fa/fa Zucker rats (6 or 16 week old) were fed diets containing CLA isomers for 8 weeks. The trans(t)10,cis(c)12-CLA isomer reduced adipocyte size in both younger and older rats. Despite beneficial changes in cell size of rats fed the t10,c12-CLA isomer, there were no changes in the renin-angiotensin system or pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 or the anti-inflammatory cytokine IL-10. In contrast, the t10,c12-CLA isomer increased adiponectin levels both in the circulation and in adipose tissue. This was associated with increased phosphorylation of endothelial nitric oxide synthase (eNOS) in adipose tissue and aorta. Direct treatment of CLA isomers in cultured endothelial cells did not increase eNOS phosphorylation but increases were observed with adiponectin treatment. In vivo, infusion with adiponectin increased eNOS phosphorylation in adipose of fa/fa Zucker rats in parallel with improvements in blood pressure. Similarly, when circulating levels of adiponectin increased in rats fed the t10,c12-CLA isomer diet, blood pressure was also attenuated. In younger rats, both the t10-c12 and c9,t11-CLA isomers were significantly different from the control group at week 8, however, only the t10,c12-CLA isomer was comparable to the commonly used anti-hypertensive medication captopril. In conclusion, the beneficial effects of the t10,c12-CLA isomer on blood pressure may in part be due to its ability to reduce the number of large adipocytes in vivo, thus increasing the production of adiponectin which subsequently activates vascular eNOS.

The completion of the color palette has yielded a family of electrochromic polymers (ECPs) each able to absorb in unique regions across the visible spectrum. Synthetically, by varying the electronic content of phenylene type moieties coupled with the donor 3,4-propylenedioxythiophene (ProDOT), high band gaps can be achieved absorbing short wavelength light, yielding a family of yellow-to-transmissive electrochromic polymers. Using the synthetic approach to tune specific absorptions in a discrete region of the visible spectrum, a family of electrochromic polymers that possess sharpened or broadened absorption spectra relative to electrochromic materials previously produced has been developed. By varying the steric hindrance of dioxythiophenes along a conjugated backbone, new hues of magenta and blue have been achieved. Through progressively adding more steric hindrance and twisting the polymer backbone, the absorbance of a polymer can be pushed towards shorter wavelengths, allowing more red light and less blue light to pass through a film. This unequal passing of long and short wavelengths reduces the overall purple color that is normally exhibited by a previous magenta ECP, thereby giving brighter, truer magenta colored materials. By reducing steric hindrance and relaxing the polymer backbone, the opposite can be achieved: pushing the absorbance of a polymer to longer wavelengths allows more blue and less red light to transmit. These polymers also exhibit highly transmissive oxidized states that are attainable at low potentials. In the quest to achieve black (or dark as defined by low L*) to transmissive ECPs with suitable contrast for window or eyewear applications, a relaxed donor-acceptor architecture has been explored. These materials give broad neutral state absorptions with a %Tint (380-780 nm) > 50 %, bringing these materials closer to realization.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / "[pi]" appears in the title as a symbol. Includes bibliographical references. Also available in electronic version.

Thesis (Ph.D.) - University of St Andrews, April 2007.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2006. / Tolbert, Laren, Committee Member ; Perahia, Dorva, Committee Member ; Perry, Joseph, Committee Member ; Collard, David, Committee Member ; Bunz, Uwe, Committee Chair.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

J E. coli On-Off &ldquo, &rdquo, °, &ndash The specific objectives of the work presented in this dissertation are to design novel molecular sensors based on fluorescence resonance energy transfer (FRET) between fluorophore (donor) and polydiacetylene (PDA, acceptor) for selective detection of biomolecules in solution. The work described in this dissertation is divided into three sections. In the first section, we report here two novel systems where the rate of energy transfer is based on changes in the spectral overlap between the emission of the donor and the absorption of the acceptor (J) as well as changes in the quantum yield of the acceptor. In the second section, we discuss modified these high sensitive molecular sensors based on FRET by using different receptors for selective detection of biomolecules such as proteins or bacteria in solution. The third section develops reversibility studies on FRET based sensors in solution or solid state. In the Chapters two and three, conjugated polydiacetylene (PDA) possessing stimuli-responsive properties have been intensively investigated for developing efficient sensors. Sensors based on FRET between conjugated polymers and fluorophores can be more sensitive than colorimetric based sensors. We use the fluorophore dansyl as the donor and polydiacetylene (PDA) as the acceptor to demonstrate the modulation of FRET efficiency through conformationally induced changes in the PDA absorption spectrum following thermal treatment that converts the PDA backbone of the liposome from the blue form to the red form. We have used steady-state electronic absorption, emission and fluorescence anisotropy (FA) analysis to characterize the thermal-induced FRET between dansyl fluorophores (donor) and PDA (acceptor). Energy transfer was found to be significantly more efficient from dansyl to the red-form PDA. This is due to large increase in the J values between dansyl emission and absorption red-form of PDA. We also have found that the monomer ratio of acceptor to donor (Rad) and length of linkers (functional part that connects dansyl fluorophores to the diacetylene group in the monomer) strongly affected FRET. A decrease in Rad resulted in diminished acceptor emission amplification. This was primarily attributed to lower FRET efficiency between donors and acceptors and a higher background signal. Increase in Rad led to increase probability of FRET from donor to acceptor as larger number of acceptors are present around a given donor. The competition between donor for energy transfer increases with decrease in Rad that contributed to lower FRET efficiency between donors and acceptors. We also found that the FRET amplification of PDA emissions after heating the solution was much higher when dansyl was linked to diacetylene through longer and flexible linkers than through shorter linkers. We attributed this to the insertion of dansyl in the bilayer of the liposomes which led to an increased dansyl quantum yield and a higher interaction of multiple acceptors with limited available donors. This was not the case for shorter and more rigid linkers where PDA amplification was much smaller. Much larger emission amplification for FRET was observed as compared to direct-excitation of PDA. The present studies aim at enhancing our understanding of FRET between fluorophores and PDA-based conjugated liposomes. These findings support the basis of a new sensing platform that utilizes J-modulated FRET as an actuating mechanism. A FRET based protein sensor by using sulforhodamine 101 as donor and PDA as acceptors was developed. This novel FRET based system primarily utilizes changes in J values (the spectral overlap between the emission of the donor and absorption of the acceptor) for the modulation of FRET efficiency between donors and acceptors. These FRET based sensors can be modified by tagged receptors (for proteins, viruses, and bactria) onto PDA liposomes which can interact with ligands present on proteins or bacteria. The biotin-streptavidin interactions were used as a sensing model system to test our FRET sensor response. In chapter 4, four different biotin-tagged lipids were used as receptors to investigate the effect of interactions between ligand-receptors on the FRET efficiency. The biotin was covalently linked to the liposome surface when using biotin-tagged diacetylene; whereas the biotin-tagged lipids with hydrophobic chains but without diacetylene functionalities provided non-covalently inserted lipids in liposomes. These studies were used to elucidate the effect of molecular interactions on FRET sensor response. The conjugated polymerized liposomes consisted of sulforhodamine-tagged-diacetylene and receptors linked lipids in different molar ratios. The characterization of the liposomes and sensing mechanism was investigated using UV-Vis and steady-state emission spectroscopy. The liposome solution yielded a weak donor emission (sulforhodamine 101) from after photo-polymerization of diacetylene monomers. This is due to energy transfer from the donor to PDA backbone chains (acceptors). The addition of streptavidin which interacted with biotin receptors resulted in increase in the sulforhodamine 101 emissions. The stress, due to interactions between biotin and streptavidin, induced the chromatic shift in the absorption spectrum of PDA which led to a decrease in the spectral overlap (J) between the emission spectra of donor and the absorption spectra of acceptor, leading to a decrease in the FRET efficiency from sulforhodamine 101 to PDA. These sensors, thus, show an "On-Off" type optical mechanism based on FRET between fluorophores and PDA where the donor emission was highly quenched in the "Off" state but was turned "On" due to receptor-ligand interactions. Large electronic absorbance and emission intensity differences between covalently and non-covalently bound biotin liposome systems were observed which indicated that the molecular interactions between biotin and PDA backbone play a crucial role in the FRET sensor response. In Chapter 5, we also developed FRET sensor for the detection of E. coli in aqueous media. Two glucose-based receptors were used in this study: (1) glucose-tagged lipid which can be inserted non-covalently in the bilayer of liposome, and (2) glucose-tagged diacetylene monomer in which the receptors were covalently bound to the backbone of the PDA liposome. The steady-state UV/Vis absorbance and fluorescence emission spectroscopy, and the fluorescence microscopy analysis of the receptors-containing liposomes were investigated for the detection of E. coli. The blue shift in the absorption spectrum of the conjugated PDA backbone induced through the interactions between receptors and bacteria resulted in decrease in the spectral overlap between the emission of SR-101 (donor) and the absorption of PDA (acceptor). This, ultimately, led to change in FRET efficiency between SR-101 and PDA after glucose - E. coli binding and caused increase in the emission intensity of SR-101. Polydiacetylenes have been exploited because of their sensitivity to external stimuli, such as temperature, pH, ions, and ligands. Unfortunately, the majorities of the sensors developed are not reversible but used as a one-time use. Here we report our preliminary results of a benzoic acid monomer of polydiacetylene (PDA-mBzA) to investigate reversible FRET characteristics between fluorophore and PDA. The LS films containing dansyl-tagged-diacetylene monomers and m-aminobenzoic acid derivatized- diacetylene monomers in different molar ratios were self-assembled and polymerized. The UV/Vis and steady-state fluorescence emission analysis of these LS films were investigated. These systems have shown partial reversible FRET over many "on-off" cycles. We believe that this incomplete FRET reversibility is due to liposomes preparation conditions used for liposomes which decreased PDA-mBzA amount in liposomes. We also reported reversible FRET studies on the liposome solutions, made from the monomer of m-aminobenzoic acid derivatized-10,12-pentacosadiynoic acid (PDA-mBzA) monomers and 11-((5-dimethylaminonaphthalene-1-sulfonyl)amino)undecanoic acid (DAUDA) or dansyl-tagged diacetylene. After photo-polymerization, the solution appeared blue in color at room temperature. Heating and cooling cycles (between 25 ºC and 95 ºC temperature range), illustrated a visible color change from blue to red and a complete return to blue over many thermal cycles. Our preliminary reversible absorption and emission measurements showed that there exist opportunities for reversibility in FRET response. We are now performing more experiments to increase the FRET reversibility in these experiments. Although our system does not display full reversibility, the preliminary absorption and emission measurements strongly suggest that there exist opportunities for fully reversible selective and sensitive FRET-based sensors after further optimization of the system.

Phenylene-based conjugated polymers are of interest for their fascinating electronic and optical properties. The introduction of bound ions into these materials adds great versatility because it can affect solubility, aggregation properties, doping chemistry, luminescence, and response to electrical stimuli. Despite ionic density being a central materials parameter in ionically functionalized conjugated polymers (IFCPs), it has been explored only in limited ranges. The primary advance reported in this dissertation is the development of three complementary synthetic routes to anionic and cationic poly(fluorene)s where the density of ionic functional groups was systematically varied between 0.05 and 0.5 per phenylene unit. There have been very few reports of IFCPs in this range. The three routes all use the Suzuki polycondensation reaction (SPR) to form poly[(R-fluorene)-co-alt-(R'-fluorene)] (PFF) IFCPs, and they differ from one another in when ionic functionality is introduced to the polymer. The development of these approaches grew out of studies on the SPR as it applies to ionically functionalized monomers, specifically, complications created by the two-phase nature of typical Suzuki couplings. In the first route, ions are added to the monomer and directly polymerized into the polymer using a single-phase SPR made possible by using oligoether functionality and a judiciously chosen solvent system. This route was used in the synthesis of a family of sulfonate and oligoether containing PFFs. In the second and third routes, ionic functionality is added after the polymer is formed either in solution or in solid films, respectively. The use of all nonionic monomers during the SPR avoided the complications encountered with two-phase reactions involving ionic monomers. The precursor polymers synthesized for these routes included a family of hexyl and bromohexyl containing PFFs and a family of oligoether and bromohexyl containing PFFs. The former were used to demonstrate post-polymerization quaternization to form cationic PFFs in solid films, and the later were quaternized in solution to yield soluble cationic PFFs. All of the polymers had very similar optical properties with the wavelengths of maximum absorption and emission in the range of 370-385 and 416-425 nm, respectively, and molecular weights greater than 10kDa and exhibited both positive and negative solvatofluorchromism due to aggregation phenomena.