Heat shock protein 70 (HSP70) is an important health related biomarker, being implicated as an early stage cancer marker and as an indicator of cardiac health. It also has important implications in wildlife environmental monitoring, as its levels can be affected by food deprivation, elevated temperatures, and pollution. Therefore, the use of HSP70 as a biomarker is highly desirable, yet the current methods of quantifying HSP70 are time consuming, expensive, and require dedicated labs. In order to facilitate widespread use of the HSP70 biomarker, a quantification tool that can be used at the point-of-care is needed. This implies the development of a simple and inexpensive HSP70 biosensing technique that is highly sensitive and selective. Therefore, in this work a label-free HSP70 biosensor has been designed based on the optical properties of gold nanoparticles (NPs). Gold NPs exhibit a large absorbance peak in the visible spectrum due to localized surface plasmon resonance (LSPR). The peak position is dependent on the local refractive index, which can be employed as a biosensor by selectively capturing the target analyte to the NP surface. To design an LSPR HSP70 sensor, optical and fluidic simulations were developed to determine optimal NP geometries and microchannel dimensions. The results showed optimal response when using 100nmx5nm gold nanotriangles inside of a 100μmx100μm microchannel. Simulations of the sensor performance showed HSP70 detection from 0.92-4000ng/ml with a resolution of 1.1ng/ml, all of which satisfied the design requirements. An LSPR sensor was experimentally tested at the benchtop scale to prove the concept. Gold NPs were fabricated by electron beam lithography and enclosed in a polymer flow cell. For initial testing of the LSPR sensor, the NPs were functionalized with biotin for selective capture of streptavidin. Streptavidin was detected in real time over the range 55-500,000ng/ml. The use of bovine serum albumin (BSA) was shown to be necessary to block non-specific binding sites to ensure a streptavidin-specific response. The LSPR sensor was then demonstrated to detect salmon HSP70 at 4600ng/ml using its synthetic antibody. Overall, these results demonstrate that LSPR can be used to realize an HSP70 biosensor suitable for point-of-care applications.

This thesis describes the synthesis and assembly of metal and semiconductor nanoparticles (NPs). The two research topics include i) hetero-assembly of metal and semiconductor NPs, ii) effect of ionic strength on homo-assembly of gold nanorods (GNRs). First, we present hetero-assembly of GNRs and semiconductor quantum dots (QDs) in a chain using biotin-streptavidin interaction. We synthesized alloyed CdTeSe QDs and modified them with mercaptoundecanoic acid to render them water-soluble and to attach streptavidin. We synthesized GNRs by a seed-mediated method and selectively modified the ends with biotin. Hetero-assembly of QDs and GNRs depended on the size, ligands, and ratio of QDs and GNRs. Second, we controlled the rate of homo-assembly of GNRs by varying the ionic strength of the DMF/water solution. The solubility of polystyrene on the ends of GNRs depended on the ionic strength of the solution, which correlated with the rate of assembly of GNRs into chains.

This thesis describes the synthesis and assembly of metal and semiconductor nanoparticles (NPs). The two research topics include i) hetero-assembly of metal and semiconductor NPs, ii) effect of ionic strength on homo-assembly of gold nanorods (GNRs). First, we present hetero-assembly of GNRs and semiconductor quantum dots (QDs) in a chain using biotin-streptavidin interaction. We synthesized alloyed CdTeSe QDs and modified them with mercaptoundecanoic acid to render them water-soluble and to attach streptavidin. We synthesized GNRs by a seed-mediated method and selectively modified the ends with biotin. Hetero-assembly of QDs and GNRs depended on the size, ligands, and ratio of QDs and GNRs. Second, we controlled the rate of homo-assembly of GNRs by varying the ionic strength of the DMF/water solution. The solubility of polystyrene on the ends of GNRs depended on the ionic strength of the solution, which correlated with the rate of assembly of GNRs into chains.

Impacts of high kinetic energy massive gold clusters (~ 500 keV Au400+4) exhibit significantly enhanced secondary ion yields relative to traditional atomic or polyatomic primary ions (e.g. Au3 and C60). The one-of-a-kind instrument used to generate these hypervelocity nanoparticles (~2 nm diameter, ~30 km/s) and monitor emissions from their impacts (SIMS) is described in detail for the first time. The projectile range of 520 keV Au400+4 is measured to be ~20 nm in amorphous carbon and projectile disintegration is observed at the exit of carbon foils as thin as 5 nm. These experiments were performed by monitoring carbon cluster ions emitted from both sides of a foil impacted by the projectile. Surprisingly, clusters emitted in the forward direction are larger than those emitted backward. The composition of the mass spectra is shown to depend on both the thickness of the foil and the size of the projectile. Secondary ion yields for a variety of materials including peptides, lipids, drugs, polymers, inorganic salts, and various small molecules have been measured and molecular ion yields for many of these species exceed unity. Multiplicity measurements show that up to seven molecular ions of leucine-enkephalin (YGGFL) can be detected from the impact of a single projectile. SI yields measured with ~500 keV Au400+4 are generally one to two orders of magnitude greater than those obtained with 130 keV Au3+ and 50 keV C60+ projectiles. The high molecular ion yields observed suggest the internal energies of ions emitted from massive cluster impacts are relatively low. In order to address this hypothesis, a novel method for measuring secondary ion internal energies was developed using a series of benzylpyridinium salts. Using this method, the internal energies were measured to be ~0.19 eV/atom, which is a factor of five less than that seen in atomic-SIMS. Sample metallization is shown to be ineffective for further increasing secondary ion yields with Au400, despite observations from previous molecular dynamic simulations. Coincidence mass spectrometry is applied to nanometric chemical segregations found on samples coated with thin layers of gold and silver. It is possible to measure the surface coverages of the metallic and underlying organic layers using mass spectrometry in a non-imaging mode.

There is an increased interest in understanding the toxicity and rational design of gold nanoparticles (GNPs) for biomedical applications in recent years. Such efforts warrant reliable, viable, and biofriendly synthetic methodology for GNPs with homogeneous sizes and shapes, particularly sizes above 30 nm, which is currently challenging. In the present study, an environmentally benign, biofriendly, singlestep/ single-phase synthetic method using dextrose as a reducing and capping agent in a buffered aqueous solution at moderate temperature is introduced. The resulting GNPs are near-spherical, stable, catalytically active, place exchangeable, and water-soluble within the size range of 10-120 nm. The added advantage of the biologically friendly reaction medium employed in this new synthetic approach provides a method for the direct embedment/integration of GNPs into biological systems such as the E. coli bacterium without additional capping ligand or surface modification processes.

En una primera parte de esta tesis fue desarrollado un nuevo electrodo a base de pasta de grafito-epoxi composite (GECE) conteniendo nitrato de bismuto [Bi(NO3)3] como precursor de bismuto incorporado [Bi(NO3)3-GECE)], como una posible alternativa para el análisis electroquímico por redisolución de metales pesados en cantidades traza. Los resultados claramente muestran las ventajas del Bi(NO3)3-GECE en combinación con la técnica de voltamperometría de redisolución anódica de onda cuadrada (SWASV) para la detección de metales pesados. Se llevaron a cabo medidas individuales y simultáneas de Pb y Cd y los resultados mostraron claramente las ventajas del Bi(NO3)3-GECE en combinación con la técnica SWASV para la detección de metales pesados. Con el uso del Bi(NO3)3-GECE construido se pueden realizar análisis rápidos y eficaces de iones de metal en cantidades traza como Pb y Cd entre otros en muestras ambientales de suelo, aguas naturales y aguas residuales. La ventaja inherente de la no necesidad de mercurio elimina muchas de las objeciones para el uso de métodos electroquímicos en la detección de tales especies en estos medios. Comparando el Bi(NO3)3-GECE con el electrodo de película de mercurio comúnmente usado y electrodo de película de bismuto desarrollado antes por nuestro grupo, el nuevo electrodo propuesto ofrece un notable funcionamiento en el análisis de metales pesados en cantidades traza, que puede ser de gran ventaja en electroquímica, contribuyendo a una aplicabilidad más amplia de técnicas electroquímicas por redisolución relacionadas con electrodos "sin mercurio". Además de aplicaciones ambientales el electrodo desarrollado basado en bismuto tendría interés especial para la aplicación en la detección de puntos cuánticos (QDs) basados en metales pesados. Tales aplicaciones están actualmente en proceso de estudio en nuestro grupo de investigación para la detección de ADN.Las otras partes de la tesis se dedican al desarrollo de nuevos sensores de ADN y proteínas basados en la misma técnica electroquímica de redisolución y el uso de nanopartículas de oro como marcas. Actualmente la detección electroquímica de secuencias de ADN específicas vía el evento de hibridación es una cuestión importante por lo cual diversas estrategias han sido propuestas.Genosensores electroquímicos de afinidad basados en el marcaje con nanopartículas de oro (AuNPs) y el uso de partículas paramagnéticas (MB) como plataforma para la inmovilización de la sonda de ADN de captura también han sido desarrollados en esta tesis a fin de demostrar la inducción magnética eficaz de un nuevo electrodo de grafito-epoxi composite-magnético (M-GECE) el cual fue construido también con pasta de grafito-epoxi composite con un pequeño imán de neodimio integrado.Todos los ensayos para la detección electroquímica de la hibridación del ADN desarrollados en esta tesis fueron basados en la detección directa de las marcas de AuNPs por medio de la técnica de voltametría de pulso diferencial (DPV) usando el M-GECE donde la intensidad de la corriente de la señal generada es directamente proporcional a la cantidad de ADN en la muestra. Como también ha sido demostrado, con el sensor de ADN asistido magnéticamente, el ADN analito condujo a una muy bien definida señal mientras que esencialmente ninguna señal fue observada para el ADN no complementario.Un nuevo inmunoensayo electroquímico sensible ha sido desarrollado, también basado en AuNPs como marca y MB como plataforma. El método fue evaluado para un inmunoensayo heterogéneo no competitivo de una IgG humana como proteína modelo. La detección electroquímica fue llevada a cabo en la misma forma que lo fue para ADN.La detección electroquímica de marcas de AuNPs en biosensores de afinidad usando métodos de redisolución permite el estudio detallado de la hibridación de ADN así como también inmuno-reacciones con interés en aplicaciones relacionadas con genosensores o inmunosensores. Los métodos electroquímicos usados para la detección de AuNPs como marca pueden ser muy prometedores tomando en cuenta su sensibilidad alta, límite de detección bajo, selectividad, simplicidad, bajo coste, y disponibilidad de instrumentos portátiles.Como conclusión final, las estrategias de análisis electroquímico de ADN y proteínas fueron demostradas con éxito y debido a los resultados prometedores su uso en muestras reales es viable. Tales biosensores de ADN e inmunosensores dan lugar a un enorme potencial de aplicación principalmente para diagnóstico clínico y monitoreo ambiental entre otros campos. / In the first part of this thesis a new graphite-epoxy composite electrode containing bismuth nitrate [Bi(NO3)3-GECE)], as built-in bismuth precursor as a possible alternative for electrochemical stripping analysis of trace heavy metals has been developed. Individual and simultaneous measurements of Pb and Cd were carried out and the results clearly showed the advantages of the Bi(NO3)3-GECE in combination with square wave anodic stripping voltammetry (SWASV) technique for heavy metals detection. Fast and effective analyses of trace metal ions such as Pb and Cd among others in environmental samples of soil, natural waters and effluents can be carried out by using the new Bi(NO3)3-GECE constructed. The inherent advantage of no necessity of mercury removes many of the objections for the use of the developed sensor. When comparing the Bi(NO3)3-GECE with the commonly used mercury film electrode and previously developed bismuth film electrode, the newly proposed electrode offers a remarkable performance in analysis of trace heavy metals, which can be advantageous in electrochemical, hence contributing to the wider applicability of electrochemical stripping techniques in connection with "mercury-free" electrodes. Beside environmental applications the developed bismuth based electrode would have special interest for application to heavy metal based quantum dots. Such applications are currently in the studying process at our research group for DNA detection.The other parts of the thesis are dedicated to the application of electrochemical stripping analysis in connection to gold nanoparticles for DNA and protein detection. Currently the electrochemical detection of specific DNA sequences via hybridization event is an important issue by which diverse strategies have been proposed. Affinity electrochemical genosensors based on labelling with gold nanoparticles (AuNPs) and the use of paramagnetic beads (MB) as platform for the immobilization of capture DNA probe have been also developed in this thesis in order to demonstrate the effective magnetic triggering of a new magnetic-graphite epoxy composite electrode (M-GECE) which was constructed with graphite-epoxy composite paste, with a small neodymium magnet integrated.All the assays for the DNA hybridization electrochemical detection developed in this thesis were based on the direct detection of AuNPs labels (anchored onto the M-GECE) by means of differential pulse voltammetry (DPV). The intensity of the generated current is directly proportional to the amount of DNA at the sample. As also has been demonstrated, with this magnetically assisted DNA sensor, target DNA leaded to very well defined signal whereas essentially no signal was observed for non-complementary DNA. By the other side a novel, sensitive electrochemical immunoassay has been also developed based in AuNPs as label and MB as platform. The method was studied and evaluated for a noncompetitive heterogeneous immunoassay of a human IgG as a model protein. The electrochemical detection was carried out in the same way that as for DNA.The electrochemical detection of AuNPs labels in affinity biosensors using stripping methods allows the detailed study of DNA hybridization as well as immunoreactions with interest in genosensor or immunosensor applications. The developed detection methodologies may be very promising taking into account their high sensitivity, low detection limit, selectivity, simplicity, low cost, and availability of portable instruments.As final conclusion, the DNA and protein electrochemical analysis strategies were successfully demonstrated and according to the promising results obtained its use for real samples is viable. Such DNA biosensors and immunosensors hold an enormous application potential principally for clinical diagnostic and environmental monitoring among other fields.

Chemotherapy regimens, one of the most common cancer treatments, are often dictated by dose-limiting toxicities. Also, the largest hurdle for translating novel biological therapies such as siRNA into the clinic is lack of an efficient delivery mechanism to get the therapeutic into malignant cells. Both of these situations would benefit from a minimally-invasive controlled release system that only delivers a therapeutic to the site of malignant tissue. This thesis presents work towards the creation of such a delivery platform using two novel material components: a thermally responsive poly[N-isopropylacrylamide-co-acrylamide] (NIPAAm-co-AAm) hydrogel and gold-silica nanoshells. Thermally responsive hydrogels undergo a physical property transition at their lower critical solution temperature (LCST). When transitioning from below to above the LCST, the hydrogel material expels large amounts of water and absorbed molecules. This phase change can be optically triggered by embedded gold-silica nanoshells, which rapidly transfer near-infrared (NIR) light energy into heat energy due to the surface plasmon resonance phenomena. When this material is loaded with absorbed drug molecules, drug release can be externally triggered by exposure to an NIR laser. Initial characterization of this material was accomplished using bulk hydrogel-nanoshell composites. Poly(NIPAAm-co-AAm)-nanoshell composites were synthesized via free radical polymerization. The LCST of the poly(NIPAAm-co-AAm) hydrogels was determined to be from 39-45 deg C, or slightly above physiologic temperature. The material was swollen in a drug solution of either doxorubicin (a common chemotherapeutic) or a 21bp dsDNA olgio (a model molecule for siRNA). Composites were then exposed to an 808 nm laser, which was found to trigger release of the therapeutics from the composite material. Further work has been done in translating this composite material to nano-scale sized particles, such that it could be injected intravenously, passively accumulate in tumor tissue, and be externally triggered to release therapeutics by exposure to an NIR laser. Sub-micron composite particles were synthesized using dissolvable gelatin templates with 500 nm wells. Analysis by transmission electron microscopy (TEM) indicates that these particles consist of gold nanoshells surrounded by a hydrogel coating. Dynamic light scattering (DLS) measurements were used to show that these particles display the same thermal properties as seen in the bulk material: collapsing in response to increased temperatures or NIR light exposure. Ultimately, the work in this thesis advances the development of a minimally-invasive, optically-triggered drug delivery platform.

Las señales de los biosensores se pueden mejorar mediante el diseño de superficies transductoras. En este sentido, se han investigado diversos métodos para la nanoestructuración de superficies. El primero de ellos se basó en la formación inicial de monocapas autoensambladas (SAM) de alcanotioles sobre sustratos bimetálicos, seguida de la desorción reductiva selectiva (SRD) de las SAM de determinados metales. Se consiguió la SRD de 2-mercaptoetanol de dominios de paladio desde una superficie de platino-oro. El segundo método para preparar superficies nanoestructuradas que se investigó fue la nucleación electroquímica secuencial de las nanopartículas metálicas (oro y paladio) sobre electrodos de carbón vidrio para las SAM de alcanotiol y para aumentar la densidad de las nanopartículas sin permitir la formación de agregados. Con este método, las señales redox de las SAM alcanotiol ferrocenil eran seis y cincuenta veces mejores que los electrodos de oro y paladio, respectivamente. Finalmente, se demostró la nanoestructuración de las superficies de los electrodos para mejorar la señal de un biosensor de ADN. / Biosensor signals can be enhanced by specifically designing transducer surfaces. In this thesis, several surface nanostructuring approaches have been investigated. The first approach studied was based on the initial formation of self-assembled monolayers (SAM) of alkanethiols on bi-metallic substrates, followed by the selective reductive desorption (SRD) of the SAM from one of the metals. SRD of 2-mercaptoethanol from palladium domains of a palladium-gold surface was achieved. The second nanostructured surface preparation method investigated was the sequential electrochemical nucleation of metal nanoparticles (gold and palladium) on glassy carbon electrode and SAM formation on the NPs to prevent aggregation and by that increasing the number densities. With this method, a six-fold and a fifty fold enhancement in the ferrocenyl alkanethiol SAM redox signal was achieved in comparison to plain gold and palladium electrodes, respectively. Finally, electrode surface nanostructuring using sequentially nucleated gold nanoparticles for signal enhancement of DNA biosensor was demonstrated.

La coordinación selectiva del oro a los triples enlaces fue la chispa que desencadenó la fiebre del oro en la química organometálica. Una amplia gama de sustratos han sido empleados pero ha sido recientemente que los cicloheptatrienoshan sido sometidos a transformaciones químicas catalizadas por oro. Se ha determinado que la reacción de alquinilcicloheptatrienos catalizada por Au(I) y Au (III) produce indenos 2- y 1-substituidos, respectivamente. En el mecanismo de esta reacción interviene un intermediario catiónico de tipo barbaralilo, sin precedentes en este tipo de química. Asimismo se ha intentado desarrollar una metodología para la síntesis de acenos por medio de una ciclación catalizada por oro, así como la síntesis de buckybowls a partir de derivados alquinílicos de la truxentriona.

Abstract The search for nanoscale active electronic devices has been an important objective in nanoscience and nanotechnology. In this study, the electronic and transport properties of the benzene-1,4-dithiol-molecule (BDT) and Au-atom-S-benzene-ring-O-(SBO)-Au-atom junctions and the Au-AlN(0001)-Au polar semiconductor junction have been calculated using the first-principles calculation method and a new integrated piecewise thermal equilibrium approach for the current. The current-voltage (I-V) and conductance-voltage (C-V) characteristic curves obtained for the Au-BDT-Au molecular junction agreed reasonably well with experimental ones. The study of Au-BDT-Au identifies that treating Au 5d electrons as core electrons and letting the S end of BDT be bonded to the Au surface directly overestimated the current. Calculated I-V characteristic curve revealed that the asymmetric Au-SBO-Au molecular junction has a pulse-like I-V characteristic curve with dual differential conductance, which resembled well the one observed experimentally. The analysis of the electronic structures showed that this dual differential conductance transport property was due to a subtle charge transfer at the electrode-molecule contacts. The calculated J-V characteristic curve of the Au-Al(0001)-Au junction shows coexistence of ohmic, switching effect and negative differential conductance. The electronic structure calculations show the existence of an intrinsic band tilt due to the polar nature of the AlN(0001) film, which gives rise to an asymmetric transport property of the junction and the presence of hole states at the N-surface side and interface states at the Al-surface side of the AlN film. The bias induced changes of the hole states, interface states and the states of the Al and N ions in central layers in the vicinity of the local chemical potential give rise to the interesting transport property of the Au-AlN(0001)-Au junction.