In contrast to most teleost fish that are ammoniotelic, the gulf toadfish (Opsanus beta) is both facultatively ureogenic and ureotelic. In vivo pharmacological manipulations were used to show that lowering circulating cortisol levels or blocking glucocorticoid receptors (GR) enhanced both urea excretion and urea pulse size. These findings demonstrated that changes in pulsatile urea excretion in the toadfish are mediated by the permissive action of cortisol through GRs. Measurement of urea transport across isolated basolateral gill membranes revealed a cortisol-sensitive carrier mechanism. Cortisol infusion in vivo significantly reduced urea transport capacity, suggesting that cortisol inhibits the recruitment of urea transport proteins (UT) to the basolateral membrane to ultimately decrease the size of the urea pulse in toadfish. A 1.2 kb fragment of the upstream transcription start site for the toadfish urea transporter (tUT) gene was isolated and in silico analysis revealed the presence of several putative glucocorticoid response element (GRE) half sites. Toadfish provided with this regulatory sequence in a reporter gene construct showed increased reporter gene transcription driven by cortisol. The data indicated that cortisol-mediated upregulation of tUT mRNA by GREs may be necessary to maintain tUT activity. Four Rhesus (Rh) glycoproteins (Rhag, Rhbg, Rhcg1, Rhcg2) were isolated from toadfish; these sequences grouped with those of other vertebrates coding for membrane channels that transport ammonia. In vivo increases in circulating cortisol reduced branchial Rh glycoprotein expression and decreased ammonia excretion. These changes were accompanied by cortisol-induced increases in glutamine synthetase activity, an enzyme that captures ammonia for urea synthesis. Taken together, the data indicated that cortisol reduces the loss by branchial excretion of ammonia, instead favouring biochemical pathways that convert ammonia to urea. This thesis confirms that nitrogen excretion in toadfish is controlled and regulated in fashions unlike those in other teleosts. The results demonstrate the importance of the GR signaling pathway in mediating changes in both urea and ammonia transport through molecular mechanisms. As a whole, the data provide a new understanding of branchial nitrogen excretion in the gulf toadfish and enhance our evolutionary perspective of the integrated biological systems involved in nitrogen excretion in fish.

<p>Urea has been widely used as a crop fertilizer to increase crop yield. The low nutrient use efficiency (NUE) of urea, however, is a challenge. Coated fertilizers are considered a solution not only for enhancing the NUE but also for alleviating soil and water pollution. In this paper, the physical properties of coated fertilizers were analyzed, including their particle size distribution, fracture force, thermal behavior, envelope density, and apparent density (regular fertilizer: pure urea and the Anderson 12-6-6; slow release fertilizer: Osmocote 14-14-14, the Anderson 18-6-12; controlled release fertilizer: Environmentally smart nitrogen (ESN), Florikan 14-14-14, Everris 17-3-6). The granules’ closed and open pore number, pore volume, and total porosity were analyzed using X-ray micro-tomography (XRCT). The results demonstrated that pure urea and Florikan have a similar median particle size, around 4 mm, while ESN and Osmocote have a similar median particle size of around 3 mm. Finally, Everris, the Andersons 18-6-12, and the Andersons 12-6-6, have a similar median particle size of roughly 2.5 mm. The fracture pressure of ESN (4.58±0.98 MPa) and the NPK combination fertilizers (Florikan: 9.40±1.46 MPa and Osmocote: 8.94±2.09 MPa) were higher than pure urea. The envelope and apparent density of pure urea (envelope: 1.22±0.02 kg/m³ and apparent: 1.27±0.01 kg/m³) and ESN (envelope: 1.26±0.03 kg/m³ and apparent: 1.27±0.00 kg/m³) are similar, while all NPK fertilizers have a significantly higher density (envelope: 1.68–1.87 kg/m³ and apparent: 1.83–2.09 kg/m³). ESN had higher internal pore space and a higher total pore volume than pure urea, while NPK combination fertilizer showed lesser pores and significantly smaller pore volumes. The physical properties were also significantly different when comparing urea and NPK compound fertilizers, mainly because of the differences in their nutrient coatings and manufacturing methods. The coating of the urea increases the granule strength but does not alter the thermal properties; however, the overall porosity of the granules is influenced by the coating. In this thesis core, different binders were used to alter the internal structure of the urea granule to control the dissolution behavior and to make it a slow-release fertilizer. The layered agglomeration technique was used to manufacture the granules. The core of the granule was made by granulating technical urea powder in a drum granulator, with corn starch as the binder. A second layer of urea was added to the core by drum granulation in order to obtain a nutrient release pattern that matches with the crop demand. Corn starch, PEG 4000, and corn starch hydrogel were used as binders for the second layer. The density, thermal properties, strength, and internal porosity were measured to compare with market urea and coated slow-release fertilizer granules. All the dissolution rates of the double layer granules were slower than for market urea. Among these granule types, the dissolution rate curve of the granule with starch hydrogel in the second layer better matched the crop demand curve than those of the other two types of granules. Moreover, the strength of the double layer granules with hydrogel was the greatest of the three double layer granules. So, overall, the double layer granule manufactured with corn starch in the core and starch hydrogel in the second layer performed the best. Although the pattern of dissolution of the double layer granule was similar to the crop nitrate demand curve, a soil-based study is needed to verify the nitrate release characteristics.<br></p><ul> </ul>

More sustainable and efficient degumming methods are required to extract finner bast fibres, especially from agro-industrial waste streams such as stalks from hemp for food purposes. For this reason, in this study, two urea-based treatments were evaluated as degumming alternatives for unretted hemp fibres from residual streams, one at cold and alkaline conditions (CUA) and the other in combination with microwave radiation (MWU). Both approaches reduced fiber bundles diameter, decreasing 61% at -7°C 5 minutes, 12%Urea-5%NaOH, and 44% for microwave-30%urea for 30 minutes. Although both methods resulted in considerable fibre bundle diameter reduction, they resulted in a lower reduction than the 74% obtained for a traditional alkali (TA) degumming. Shorter fibres were obtained after the treatments. CUA and TA treatments obtained similar fibre lengths, while MWU resulted in longer than the other treatments. The chemical and thermal analysis showed that the highest removal of no cellulosic components was achieved by the TA treatment, followed by CUA and MWU. The treatments were applied to nonwovens produced by needle punching, showing no significant differences in tenacity and flexural rigidity compared to non-treated nonwovens. An increase of mass per unit area was identified for the CUA-treated fabrics, attributed to crimp generated in the treatment. Both urea-based treatments showed potential as more sustainable alternatives for degumming unretted hemp fibre bundles extracted from agro-waste.

The aftertreatment techniques introduced to follow the emission legislations require a constant improvement process to comply with the gradually more stringent demands. SCR is the system used nowadays to deal with NOx emissions in most heavy-duty vehicles. An aqueous-urea solution, AdBlue, is sprayed into the evaporation unit, where urea should decompose to ammonia, the reducing agent. This is a critical step because the NH3 amount available heavily affects the final nitrous oxides reduction to nitrogen. Moreover the urea decomposition’s sides reactions are likely to occur, forming deposits that increase the pressure drop and in a certain time period could even foul the system. The evaporation module used in the silencer for Scania trucks equipped with V8 engines consists of a pipe in pipe configuration made in stainless steel 1.4509, where the exhaust gases flow heating up the inner pipe finned on its outer surface. The AdBlue is sprayed on the inner pipe’s inner surface, creating a wall film and cooling down the tube. The production of the evaporation pipe however involves a costly manufacturing process, being made of 144 flanges laser welded on a 0.355 m length, for a total of more than 52 m of welding. The goal of this thesis is to analyse the heat transfer from the exhaust gases to the pipe and how to improve it, in order to achieve a lower temperature drop on the pipe due to the AdBlue dosing, reducing at the same time the risk of building up deposits. The application of different materials for the evaporation unit is also considered. Furthermore many manufacturing processes are evaluated as a cost-effective alternative to the current one. Although the operating points have a wide range of variation, the analysis is focused on the worst conditions for urea evaporation which are low mass flow and low flow temperature. Stainless steel is the best trade-off between cost, thermal conductivity and corrosion resistance but the much higher conductivity of copper alloys would justify the investigation of a copper evaporation pipe coated with stainless steel. Different designs of the heat flanges are assessed, first with correlations and FEA and then through a CFD analysis, where 62 different solutions are compared. The fins height results to be the most influencing parameter, requiring an increment from 7.5 mm to 11 mm to improve the heat transfer performances of the evaporation unit. The gap between each fin is also important, leading to a flanges quantity reduction suggestion. With the current fin design and half of the number of flanges, 11 mm high, the performances would improve by almost 40% (at 800 kg/h and 300℃). Furthermore both the Abstract pipe thickness and thermal conductivity are affecting the temperature drop, with different weight depending on the design and the operating point. It is however always advantageous to use a thicker wall and a material with a higher thermal conductivity. Lastly the tests performed on the specifically developed test rig show a good accordance with the simulations in comparing different materials but are not suitable to compare finned designs. / Avgasefterbehandlingssystem har utvecklats för att reducera utsläppen ifrån lastbilar, och det är ett lagkrav att en lastbil ska ha ett efterbehandlingssystem. Lagkraven för avgasemissioner skärps gradvis, vilket resulterar i att efterbehandlingssystemet ständigt måste förbättras och utvecklas för att möta de nya lagkraven. I de flesta heavy-duty-lastbilar som säljs på Euro 6 marknader är ett SCR-system installerat ihop med ljuddämparen för att hantera NOx-utsläppen. En vätska kallad AdBlue, det vill säga Urea, sprayas in i efterbehandlingssystemet där det förångas. Urea är en vätska baserad på bl.a. urinämne som utsöndras till ammoniak, vilket sedan fungerar som reduceringsmedel. Ett viktigt steg i reduktionsprocessen av kväveoxiden är när ammoniak reagerar med NOx och omvandlas till kväve och vatten. Det är mängden ammoniak som bestämmer det slutliga resultatet av kväveoxidreduktionen. Om urean inte är tillräckligt uppblandad med avgaserna bildas avlagringar utmed flödeskanalen. Detta ökar tryckfallet, vilket i sin tur leder till ökad bränsleförbrukning, avlagringarna kan över tid även skada efterbehandlingssystemet. Förångningsmodulen som används i Scanias ljuddämpare (kallad large), utvecklad för V8-motorer, består av en rör-i-rör konfiguration. Rören tillverkas i rostfritt stål 1.4509 och när AdBlue sprayas på insidan av innerröret bildas en film av urea som förångas när den möter rörets varma väggyta. För att uppnå en varm förångningsyta leds en delmängd av avgaserna om på utsidan av innerröret för att bibehålla hög temperatur på röret och undvika nedkylning av urean. Förångningsrörets nuvarande design består av 144 utvändiga värmeflänsar (med längden 0,355 m) som lasersvetsas fast på röret. Designen medför en dyr och komplicerad tillverkningsprocess. Den totala längden svets uppgår till 52 m. Syftet med examensarbetet är att analysera och förbättra värmeöverföringen från avgaserna till röret för largeljuddämparen. En förbättrad värmeöverföring skulle leda till att temperaturfallet som uppkommer på grund av AdBlue-doseringen blir lägre. Ett lägre temperaturfall skulle då leda till en minskad risk för avlagringar. I studien undersöks olika material och tillverkningsmetoder för att eventuellt reducera tillverkningskostnaden av förångningsenheten med bibehållen eller förbättrad prestanda. Driftfallen har ett brett spektrum där mängden energi (överförd värme) varierar och studien är inriktad på de värsta förhållandena för urea-utsöndring, dvs. ett lågt massflöde och låga flödestemperaturer. Rostfritt stål har bra korrosionsbeständighet och tämligen bra värmeledningsförmåga i kombination med ett rimligt pris. Kopparlegeringar har en mycket högre värmeledningsförmåga än rostfritt stål, vilket motiverar en undersökning av förångringsrör tillverkade i kopparlegering belagda med rostfritt stål. I studien undersöks olika utformning av värmeflänsar, både genom FEA och CFD-analyser, där 62 olika utformningar har tagits fram och jämförs. Flänsarnas höjd visade sig vara den parametern som påverkar temperaturfallet mest. En ökning från 7,5 mm till 11 mm av flänstoppens höjd gav en kraftig förbättring av förångningsenhetens värmeöverföringsförmåga. En annan viktig faktor visade sig vara avståndet mellan flänsarna. Med dagens flänsutformning, men med en utökad höjd till 11 mm, skulle man uppnå en förbättrad prestanda med nästan 40 % (vid 300℃ och 800 kg/h) om man dessutom minskade antalet flänsar med hälften. Beroende på design och driftspunkt är rörtjockleken och materialets värmeledningsförmåga andra faktorer som påverkar temperaturfallet. Det är dock oftast fördelaktigt med en tjockare rörvägg och ett material med högre värmeledningsförmåga. Flera prototyper med olika utformning har testats fysiskt i en specialtillverkad testrigg. Slutresultatet påvisade en bra korrelation med simuleringarna vid jämförelse av olika materialval, men det fysiska testet hade svårare att hantera geometrisk utformning på flänsarna.

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Utsläppskontroll, reglerad av allt strängare lagstiftning, ställer höga krav på utvecklingen av noggranna efterbehandlingssystem för avgaser. När det gäller utsläpp från dieselmotorer utgör NOx-minskning en av de största utmaningarna. För tunga fordon tacklas denna utmaning ofta genom ett SCR-system. SCR-systemet kan omvandla upp till 95% av NOx-utsläppen till kväve och syre, genom utnyttjande av ett selektivt reduktionsmedel över en katalysatoryta. Ammoniak är ett sådant reduktionsmedel men är inte i sig ett lämpligt val för mobila tillämpningar på grund av de miljö-, hälso- och säkerhetsproblem som är förknippade med denna förening. Istället används en ofarlig vattenlösning med urea, kallad AdBlue, som vid injektion i varm avgas sönderdelas till tillräckliga mängder ammoniak som behövs vid SCR-katalysatorn för att minska den NOx som produceras relativt motorns belastningspunkt.  AdBlue-injektion i avgasströmmen kan emellertid komplicera ett redan komplext system ur ett materialvalsperspektiv. Även om urea inte anses vara ett särskilt korrosivt ämne råder en viss osäkerhet kring biprodukterna som kan bildas vid ofullständig nedbrytning av urea. I avgassystem nämns ofta dessa ureaderivat i samband med ett fenomen då smält urea skapar en flytande film på avgassystemets ytor som då genererar fasta biproduktavslagringar vid filmens yttre kanter.  Denna studie syftar till att identifiera några av riskerna kopplade till AdBlue-injektion på ytor av rostfritt stål. Därav undersöks nedbrytningsbeteendet hos de austenitiska rostfria stålen 1.4828 och 1.4835 efter vätning med AdBlue-spray under statiska förhållanden i avgaser, 350 ℃ och 700 kg/h. Testbänksproceduren ger ett kostnadseffektivt sätt att sålla ut potentiella rostfria stål i en realistisk avgasmiljö innan komponenttestning. Testet av 1.4828 inkluderar även ett dragprov, för att undersöka betydelsen av plastiska deformationer. Därtill undersöks en martensitisk stålkomponent, som tidigare använts i en avgasmiljö under AdBlue-injektion, för att ytterligare bilda en uppfattning om de risker som ett material under dessa förhållanden måste uthärda.  Rostfria stål undersöktes efter exponering med konfokalmikroskopi och SEM/EDS. Avlagringar som hittades på 1.4835 studerades med FTIR.  Resultaten visar riskerna med ett dåligt materialval och eventuell frånvaro av oxidfilm som kan relateras till termisk stress, ureanedbrytningsreaktioner med oxidförbrukande egenskaper eller mekaniskt avlägsnande, t.ex. erosion / Emission control, regulated by evermore strict legislation, put high demands on the development of meticulous exhaust gas aftertreatment systems. In diesel engine emissions, NOx reduction poses one of the major challenges. For heavy duty vehicles, this challenge is often tackled by the use of an SCR system, capable of converting up to 95 % of NOx emissions into nitrogen and oxygen, by use of a selective reductant over a catalyst surface. Ammonia is such a reductant but is not in itself an appropriate choice for mobile applications due to the environmental, health and safety concerns associated with this compound. Hence, an aqueous solution of urea, trademarked AdBlue, is used as a harmless reservoir that upon injection into hot exhaust gas decompose into sufficient amounts of ammonia needed at the SCR catalyst to reduce NOx produced, relative to the load point of the engine.  AdBlue injection into the exhaust gas stream can, however, complicate an already complicated system from a material choice perspective. Although, urea is not deemed a particularly corrosive compound, concerns have been raised towards its derivatives often mentioned in relation to a melted urea wall film phenomenon, on exhaust surfaces, generating, solid by-product deposits at the peripheral areas of the film.  This work aims to identify some of the risks coupled with AdBlue injection on stainless steel surfaces. Hence, degradation behaviour of austenitic stainless steel grades 1.4828 and 1.4835, is studied after wetting with AdBlue spray in static exhaust gas conditions, 350 ℃ and 700 kg/h. The test bench procedure, provide a cost-effective way of screening potential stainless steels in a realistic exhaust gas environment before component testing. The test of 1.4828 includes a comparison of the grade with and without plastic deformation. Additionally, a martensitic steel component, used in an exhaust gas environment under AdBlue injection, was added to this work to further portray the risks that a material under these conditions must endure.  Stainless steels are examined post exposure using confocal microscopy and SEM/EDS. Deposits found on 1.4835 were studied with FTIR.  The results portray the risks of a poor material choice and possible absence of oxide film that could be related to thermal stress, decomposition reactions involving oxide consuming properties, or mechanical removal e.g. erosion.

The objective of this study was to investigate the effects of melamine and ether contents on the curing and performance properties of UF resins as binders for wood composites. Various UF and UMF resins were synthesized with three different synthesis procedures. These resins were examined by 13C NMR, rheometer, and other methods and evaluated as particleboard binders. Three-layer particleboards were prepared with the resins catalyzed with various catalysts and levels, applied in face and core layers. The board test results were compared. Only about half of added melamine had reacted with formaldehyde. UMF resins were found to be catalyzed with stronger catalysts at suitable levels depending on melamine levels and on which layer of particleboard the UMF resins are to be applied. Even catalyzed with a stronger catalyst, the curing rates of UMF resins were still slower, and storage stabilities were shorter than UF resins, but the pot lives were longer, and internal bond strength and water resistance were higher. Moreover, resins synthesized with procedures 2 and 3 showed obviously longer storage times, longer pot lives, and longer gel times, and the particleboards bonded with these resins showed significant improvements in internal bond strength and water absorption values but the formaldehyde contents increased. The increased formaldehyde content test values indicated that linear methylene-ether groups in UF resins decompose in the hot-pressing of boards to emit formaldehyde, most of which is not captured back into the UF resin matrix. Uron-type methylene-ether groups decompose in the hot-pressing of boards to participate in the curing process and enhance the bonding of boards, but it could also emit extra formaldehyde which may not be effectively captured by UF resins but more effectively by UMF resins if the amount of melamine is high enough because of the increased reactive capacities of melamine. The results of this research offered a new hypothesis that the linear methyleneether bonds in UF resins might be a major contributor of the high free formaldehyde contents of particleboards. Decreasing the linear methylene-ether groups contents might effectively bring down the formaldehyde content of boards.

Non-covalent intermolecular interactions play a large role in determining the properties of a given system, from segmented copolymers to interactions of functionalized polymers with non-viral nucleic acids delivery vehicles. The ability to control the intermolecular interactions of a given system allow for tailoring of that system to yield a desired outcome, whether it is a copolymers mechanical properties or the colloidal stability of a pDNA-delivery vector complex. Each chemical system relies on one or more types of intermolecular interaction such as hydrogen bonding, cooperative À-À stacking, electrostatic interactions, van der waals forces, metal-ligand coordination, or hydrophobic/solvophobic effects. The following research describes the tailoring of specific intermolecular interactions aimed at altering the physical properties of segmented copolymers and non-viral gene delivery vectors. Amide containing segmented copolymers relies heavily on hydrogen bonding intermolecular interactions for physical crosslinking to impart the necessary microphase separated morphology responsible for a copolymers physical properties. Amide containing hard segments are composed of various chemical structures from crystalline aramids to amorphous alkyl amides with each structure possessing unique intermolecular interactions. Variations to either of the copolymer segments alters the copolymers physical properties allowing for tuning of a copolymers properties for a particular application. The synthetic strategies, structure-property relationships, and physical properties of amide containing segmented copolymers are thoroughly reported in the literature. Each class of segmented copolymer that contain amide hydrogen bonding groups exhibits a wide range of tunable properties desirable for many applications. The segmented copolymers discussed here include poly(ether-block-amide)s, poly(ether ester amide)s, poly(ester amide)s, poly(oxamide)s, PDMS polyamides, and polyamides containing urethane, urea, or imide groups. The structure-property relationships (SPR) of poly(oxamide) segmented copolymers is not well understood with only one report currently found in literature. The effects of oxamide spacing in the hard segment and molecular weight of the soft segments in PDMS poly(oxamide) segmented copolymers demonstrated the changes in physical properties associated with minor structural variations. The optically clear PDMS poly(oxamide) copolymers possessed good mechanical properties after bulk polymerization of ethyl oxalate terminated PDMS oligomers with alkyl diamines or varied length. FTIR spectroscopy experiments revealed an ordered hydrogen bonding carbonyl stretching band for each copolymer and as the spacing between oxamide groups increased, the temperature at which the hard segment order was disrupted decreased. The increased spacing between oxamide groups also led to a decrease in the flow temperature observed with dynamic mechanical analysis. Copolymer tensile properties decrease with increased oxamide spacing as well as the hysteresis. The structure-property investigations of PDMS poly(oxamide) segmented copolymers showed that the shortest oxamide spacing resulted in materials with optimal mechanical properties. A new class of non-chain extended segmented copolymers that contained both urea and oxamide hydrogen bonding groups in the hard segment were synthesized. PDMS poly(urea oxamide) (PDMS-UOx) copolymers displayed thermoplastic elastomer behavior with enhanced physical properties compared to PDMS polyurea (PDMS-U) controls. Synthesis of a difunctional oxamic hydrazide terminated PDMS oligomer through a two-step end capping procedure with diethyl oxalate and hydrazine proved highly efficient. Solution polymerization of the oxamic hydrazide PDMS oligomers with HMDI afforded the desired PDMS-UOx segmented copolymer, which yielded optically clear, tough elastomeric films. Dynamic mechanical analysis showed a large temperature insensitive rubbery plateau that extended up to 186 ÚC for PDMS-UOx copolymers and demonstrated increased rubbery plateau ranges of up to 120 ÚC when compared to the respective PDMS-U control. The increase in thermomechanical properties with the presence of oxamide groups in the hard segment was due to the increased hydrogen bonding, which resulted in a higher degree of microphase separation. DMA, SAXS, and AFM confirmed better phase separation of the PDMS-UOx copolymers compared to PDMS-U controls and DSC and WAXD verified the amorphous character of PDMS-UOx. Oxamide incorporation showed a profound effect on the physical properties of PDMS-UOx copolymers compared to the controls and demonstrated promise for potential commercial applications. Two novel segmented copolymers based on a poly(propylene glycol) (PPG) that contained two or three oxamide groups in the hard segment were synthesized. Synthesis of non-chain extended PPG poly(trioxamide) (PPG-TriOx) and PPG poly(urea oxamide) (PPG-UOx) segmented copolymers utilized the two-step end-capping procedure with diethyl oxalate and hydrazine then subsequent polymerization with oxalyl chloride or HMDI, respectively. The physical properties of the PPG-TriOx and PPG-UOx copolymers were compared to those of PPG poly(urea) (PPG-U) and poly(oxamide) (PPG-Ox) copolymers. FTIR studies suggested the presence of an ordered hydrogen bonded hard segment for PGG-TriOx and PPG-Ox copolymers with PPG-TriOx possessing a lower energy ordered hydrogen bonding structure. PPG-UOx copolymers exhibited a larger rubbery plateau and higher moduli compared to PPG-U copolymers and also a dramatic increase in the tensile properties with the increased hydrogen bonding. The described copolymers provided a good example of the utility of this new step-growth polymerization chemistry for producing segmented copolymers with strong hydrogen bonding capabilities. Non-viral nucleic acid delivery has become a hot field in the past 15 years due to increased safety, compared to viral vectors, and ability to synthetically alter the material properties. Altering a synthetic non-viral delivery vector allows for custom tailoring of a delivery vector for various therapeutic applications depending on the target disease. The types of non-viral delivery vectors are diverse, however the lack of understanding of the endocytic mechanisms, endosomal escape, and nucleic acid trafficking is not well understood. This lack of understanding into these complex processes limits the effective design of non-viral nucleic acid delivery vehicles to take advantage of the cellular machinery, as in the case of viral vectors. Mechanisms for cellular internalization of polymer-nucleic acid complexes are important for the future design of nucleic acid delivery vehicles. It is well known that the mammalian cell surface is covered with glycosaminoglycans (GAG) that carry a negative charge. In an effort to probe the effect of GAG charge density on the affinity of cationic poly(glcoamidoamine) (PGAA)-pDNA complexes, quartz crystal microbalance was employed to measure the mass of GAGs that associated with a polyplex monolayer. Affinity of six different GAGs that varied in the charge density were measured for polyplexes formed with poly(galactaramidopentaethylenetetramine) (G4) cationic polymers and pDNA. Results showed that the affinity of GAGs for G4 polyplexes was not completely dependent on the electrostatic interactions indicating that other factors contribute to the GAG-polyplex interactions. The results provided some insight into the interactions of polyplexes with cell surface GAGs and the role they play in cellular internalization. Two adamantane terminated polymers were investigated to study the non-covalent inclusion complexation with click cluster non-viral nucleic acid delivery vehicles for passive targeting of the click cluster-pDNA complexes (polyplex). Incorporation of adamantyl terminated poly(ethylene glycol) (Ad-PEG) and poly(2-deoxy-2-methacrylamido glucopyranose) (Ad-pMAG) polymers into the polyplex formulation revealed increased colloidal stability under physiological salt concentrations. Ad-pMAG polyplexes resulted in lower cellular uptake for HeLa cells and not two glioblastoma cell lines indicating the pMAG corona imparts some cell line specificity to the polyplexes. Ad-pMAG provided favorable biological properties when incorporated into the polyplexes as well as increased polyplex physical properties. / Ph. D.

Call number: LD2668 .T4 1965 W531 / Master of Science