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Localized surface plasmon resonance (LSPR) describes the collective oscillation of conductive electrons in noble metal nanostructures, such as gold, silver and copper; or in selected doped semiconductor nanocrystals. Nanoplasmonics is emerging as a useful and versatile platform that combines the intense and highly tunable optical responses derived from LSPR with the intriguing materials properties at the nanoscale, including high specific surface areas, surface and chemical reactivity, binding affinity, and rigidity. LSPRs in plasmonic nanoparticles (NPs) can provide large optical cross-sections, and can lead to a wide variety of subsequent photophysical responses, such as localization of electric (E-)fields, production of plasmonic hot charge carriers, photothermal heating, etc. Plasmonic NPs can also be combined with other molecular or nanoscale systems into plasmonic heterostructures to further harvest the resonant E-field enhancement or to prolong the lifetime of plasmonic charge carriers. In this dissertation, we study the photophysical properties of plasmonic Ag and Au NPs, particularly E-field localization and hot charge carrier production performances; and illustrate how they can be optimized towards plasmonic photocatalysis, development of nano-antimicrobials, and surface-enhanced Raman spectroscopy (SERS) sensing. We demonstrate that with a lipid-coated noble metal nanoparticle (L-NP) model, the E-field localization properties could be optimized through positioning molecular photosensitizers or photocatalysts within a plasmonic “sweet spot”. This factor renders the plasmonic metal NPs efficient nanoantenna for resonant enhancement of the intramolecular transitions as well as the photocatalytic properties of the molecular photocatalysts. The enhanced photoreactivity have been applied to facilitate fuel cell half reactions for the enhancement of light energy conversion efficiencies; as well as to facilitate the release of broad-band bactericidal compounds that enables plasmonic nano-antimicrobials. Localized E-fields in L-NPs also enhance the inelastic scattering from molecules through SERS. This is utilized to obtain molecular-level information on the configuration of sterol-based, alkyne-containing Raman tags in hybrid lipid membranes, which enables spectroscopic sensing and targeted imaging of biomarker-overexpressing cancer cells at the single-cell level. In contrast to the localized E-field, plasmonic charge carrier generation mechanism relies on non-radiative decay pathways of the excited plasmons that lead to production of ballistic charge carriers. The plasmonic hot charge carriers directly participate in chemical redox processes with degrees of controllability over the nature of the charge carrier produced and direction of their transfers. The implementation and optimization of these mechanisms are explored, and the significances of some relevant applications are discussed.

Tesis por compendio / This thesis explores new analytical advances using compact disk biosensing technologies, and comprises six scientific publications distributed along four chapters. Special attention is herein payed to Thermochromic Etching Disks (TED) technology (Chapter 1), rational design of disk-based biorecognition assays (Chapter 2), and label-free detection systems for point-of-need analysis (Chapters 3 and 4). First, insights into a novel light-mediated signal developing system for biorecognition assays (based on TED disks and drives) are provided together with an overview of the state-of-the art and future trends in photo- and thermochromic biosensing. This signal developing approach exploits photo- and thermochromism for biosensing in an original manner and represents a potential strategy to simplify signaling processes in bioanalytical systems. Then, how to transform TED technology into lab-on-a-disk systems is addressed. TED has proven to be a very versatile tool to perform sensitive analysis of biorecognition assays, using platforms and scanners easily obtained from regular disks and drives, respectively. Biologically relevant assays of different nature (microarray, cell culture, immunofiltration, turbidimetry, etc.) have been arrayed in a single disk and sensitively analyzed by imaging. Regarding rational design, a theoretical-experimental method (INSEL) based on kinetics and mass-transport modelling for optimizing biorecognition assays and exploring their behavior is presented. INSEL has been implemented as an in silico tool that enables to characterize biointeractions with minimal experimentation, to perform optimizations directed towards custom objectives defined by the user, and to easily compute the effect of critical variables without further experiments. In another study included in this thesis, polycarbonate grooved structures obtained from standard recordable disks (CD-R and DVD-R) were coated with silver and tailored to become SERS-active. This strategy represents a cost-effective and industrially scalable alternative to the SERS substrates typically used for bioanalysis. These disk-based materials have presented tunable plasmonic responses, significant Raman enhancement, and have allowed complex biological targets (such as proteins and exosomes) to be analyzed by SERS without using labeled reagents as tracers. In addition to introduce inexpensive and large-scale SERS substrates for biosensing, this study also suggests the development of prospective Raman scanners based on disk drives. Another approach herein presented addresses the implementation of diffraction-based sensing (DBS) in TED technology in order to conceive disk-based label-free biosensors based on standard disks and drives. At first, a comprehensive experimental assessment of the analytical possibilities offered by DBS is presented. Then, the fabrication of arrays of diffractive protein networks on TED disks is investigated, with which sensitive analysis of antibodies in label-free conditions has been demonstrated, using adapted drives as scanners. This investigation provides important insights into cost-effective and industrially scalable functional materials and detection setups that exploit consumer electronics for label-free biosensing. / Esta tesis explora nuevos avances en química analítica usando tecnologías de biosensado basadas en sistemas de disco compacto y comprende seis publicaciones científicas distribuidas a lo largo de cuatro capítulos. Los estudios se han centrado en la tecnología Thermochromic Etching Disks (TED) (Capítulo 1), el diseño racional de ensayos de bioreconocimiento en discos compactos (Capítulo 2), y la detección sin marcaje para realizar análisis in situ (Capítulos 3 y 4). Primero, enmarcado en una discusión del estado del arte y futuras tendencias en biosensado foto y termocrómico, se presenta un nuevo sistema (basado en discos y lectores TED) mediado por luz para el desarrollo de señales en ensayos de bioreconocimiento. Ésta constituye una estrategia novedosa para aprovechar el foto y termocromismo en biosensado, y presenta un gran potencial para simplificar los procesos de desarrollo de señal en sistemas bioanalíticos. A continuación, se aborda cómo transformar la tecnología TED en sistemas analíticos integrados basados en discos compactos. TED ha demostrado ser una herramienta muy versátil para analizar, de forma sensible, ensayos de bioreconocimiento usando plataformas y escáneres fácilmente obtenidos a partir de discos y lectores convencionales, respectivamente. Un único disco ha mostrado poder albergar varios ensayos biológicos importantes y de distinta naturaleza (micromatriz, cultivos celulares, inmunofiltración, turbidimetría, etc.), para ser analizados de forma sensible a través de imágenes En cuanto al diseño racional, se presenta un método teórico-experimental (INSEL), basado en modelos cinéticos y de transporte de masa, para optimizar ensayos de bioreconocimiento y explorar su comportamiento. INSEL se ha implementado como una herramienta in silico que permite caracterizar biointeracciones mediante mínima experimentación, realizar optimizaciones dirigidas a objetivos particulares definidos por el usuario, y computar el efecto de variables críticas de forma sencilla y sin experimentos adicionales. En otro estudio incluido en esta tesis, nanoestructuras en forma de surco obtenidas a partir de discos regrabables convencionales (CD-R y DVD-R) fueron recubiertas con plata y adaptadas para ser activas en SERS. Esta estrategia supone una alternativa, económicamente efectiva e industrialmente escalable, a los sustratos SERS típicamente usados en bioanálisis. Estos materiales han mostrado respuestas plasmónicas sintonizables, una amplificación Raman significativa, y han permitido analizar muestras biológicas complejas (como proteínas y exosomas) mediante SERS sin usar marcadores. Además de introducir sustratos SERS grandes y baratos, este trabajo también sugiere el desarrollo de escáneres Raman basados en lectores de disco. Otra aproximación presentada en esta tesis aborda la implementación de DBS (diffraction-based sensing) en tecnologías TED, con el fin de desarrollar biosensores para detección sin marcaje basados en discos y lectores convencionales. Primero, se presenta una amplia evaluación experimental de las posibilidades analíticas ofrecidas por DBS. A continuación, se investiga la fabricación de multitud de redes difractivas de proteínas sobre discos TED, con las que se ha demostrado la determinación sensible y sin marcaje de anticuerpos, usando lectores adaptados como escáneres analíticos. Esta investigación introduce avances importantes que apuntan al desarrollo de materiales funcionales y sistemas de detección, baratos e industrialmente escalables, que aprovechen las tecnologías de consumo para realizar biosensado sin marcaje. / Aquesta tesi explora nous avanços en la química analítica usant tecnologies de biosensat basades en sistemes de disc compacte, i comprèn sis publicacions científiques distribuïdes en quatre capítols. Els estudis s'han centrat en la tecnologia Thermochromic Etching Disks (TED) (Capítol 1), el disseny racional d'assajos de bioreconeixement en discos compactes (Capítol 2), i la detecció sense marcatge per realitzar anàlisi in situ (Capítols 3 i 4). Primer, dins del marc d'una discussió de l'estat de l'art i tendències futures en biosensat foto i termocròmic, es presenta un nou sistema (basat en discos i lectors TED) per al desenvolupament de senyals mitjançant llum, en assajos de bioreconeixement. Aquesta constitueix una nova estratègia per aprofitar el foto i termocromisme en biosensat, mentre que també presenta una gran potencial per simplificar els processos de desenvolupament de senyal en sistemes bioanalítics. Tot seguit, s'aborda com transformar la tecnologia TED en sistemes analítics integrats basats en discos compactes. TED ha demostrat ser una eina molt versàtil per analitzar, de forma sensible, assajos de bioreconeixement usant plataformes i escàners fàcilment obtinguts a partir de discos i lectors convencionals, respectivament. Un únic disc ha mostrat poder albergar diversos assajos biològicament importants i de distinta naturalesa (micromatrius, cultius cel·lulars, immunofiltració, turbidimetria, etc.), per a ser analitzats de forma sensible a través d'imatges. Pel que fa al disseny racional, es presenta un mètode teòric-experimental (INSEL), basat en models cinètics i de transport de massa, per optimitzar assajos de bioreconeixement i explorar el seu comportament. INSEL s'ha implementat com a una eina in silico que permet caracteritzar biointeraccions amb mínima experimentació, realitzar optimitzacions dirigides cap a objectius particulars definits per l'usuari, i computar l'efecte de variables crítiques de forma senzilla i sense experiments addicionals. En un altre estudi inclòs en aquesta tesi, nanoestructures en forma de solc obtingudes a partir de discos compactes regravables convencionals (CD-R i DVD-R) van ser recobertes amb plata i adaptades per a ser actives en SERS. Aquesta estratègia suposa una alternativa, econòmicament efectiva i industrialment escalable, als substrats SERS típicament usats en bioanàlisi. Aquests materials han mostrat respostes plasmòniques sintonitzables, una amplificació Raman significativa, i han permès analitzar mostres biològiques complexes (com proteïnes i exosomes) mitjançant SERS sense usar marcadors. A més d'introduir substrats SERS grans i barats, aquest treball també suggereix el desenvolupament d'escàners Raman basats en lectors de disc. Una altra aproximació presentada en aquesta tesi aborda la implementació de DBS (diffraction-based sensing) en tecnologies TED, per tal de desenvolupar biosensors basats en discos i lectors convencionals que permeten detecció sense marcatge. Primer, es presenta una amplia avaluació experimental de les possibilitats analítiques que ofereix aquesta tècnica. A continuació, s'investiga la fabricació de multitud de xarxes difractives de proteïnes sobre discos TED, amb les quals s'ha demostrat la determinació sensible i sense marcatge d'anticossos, usant lectors adaptats com a escàners analítics. Aquesta investigació introdueix avanços importants que apunten cap al desenvolupament de materials funcionals i sistemes de detecció, barats i industrialment escalables, que aprofiten les tecnologies de consum per dur a terme bioanàlisi sense marcatge. / Avellà Oliver, JM. (2017). Towards label-free biosensing in compact disk technologies f or point-of-need analysis [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86128 / Compendio

Anisotropic plasmonic noble metallic nanoparticles (APMNs) have received enormous attention due to their distinct geometric features and fascinating physicochemical properties. Owing in large part to their tailored localized surface plasmon resonance (LSPR) and the intensive electromagnetic field at the sharp corners and edges, APMNs are exceptionally well suited for biomedical applications such as biosensing, bioimaging, diagnostics and therapeutics. Although a rich variety of surfactant-assisted colloidal routes have been developed to prepare well-defined APMNs, biomedical applications necessitate tedious and rigorous purification processes for the complete removal of toxic surfactants. In this dissertation, we aim to develop generic bioenabled green synthetic methodologies towards APMNs. By applying a series of thermodynamic, kinetic and seed quality control, a series of APMNs with varied morphologies such as branched nanostars and triangular nanoprisms have been successfully prepared. We first presented the preparation of gold nanostars (Au NSTs) through a two-step approach utilizing a common Good's buffer, HEPES, as a weak reducing agent. Single crystalline Au NSTs with tunable branches up to 30 nm in length were produced and the halide ions rather than the ionic strength played a significant roles on the length of the branches of Au NSTs. Then consensus sequence tetratricopetide repeat (CTPR) proteins with increasing number of repeats were used as model proteins to probe the effects of concentration as well as the protein shape on the morphology and resulting physicochemical properties of plasmonic gold nanoparticles. Since the underlying growth mechanism for the biomimetic synthesis of APMNs remains elusive and controversial, the other objective is to elucidate the molecular interactions between inorganic species and biopolymers during the course of NP evolution. Fluorescent quenching and 2D NMR experiments have confirmed the moderate binding affinity of CTPR to the Au(0) and Au(III). We observed that the initial complexation step between gold ions and CTPR3 is ionic strength dependent. Furthermore, we also found that NPs preferentially interact with the negatively charged face of CTPR3 as observed in 2D NMR. Knowledge of binding behavior between biospecies and metal ions/NPs will facilitate rational deign of proteins for biomimetic synthesis of metallic NPs. A modified seed-mediated synthetic strategy was also developed for the growth of silver nanoprisms with low shape polydispersity, narrow size distribution and tailored plasmonic absorbance. During the seed nucleation step, CTPR proteins are utilized as potent stabilizers to facilitate the formation of planar-twinned Ag seeds. Ag nanoprisms were produced in high yield in a growth solution containing ascorbic acid and CTPR-stabilized Ag seeds. From the time-course UV-Vis and transmission electron microscopy (TEM) studies, we postulate that the growth mechanism is the combination of facet selective lateral growth and thermodynamically driven Ostwald ripening. By incorporation of seeded growth and biomimetic synthesis, gold nanotriangles (Au NTs) with tunable edge length were synthesized via a green chemical route in the presence of the designed CTPR protein, halide anions (Br⁻) and CTPR-stabilized Ag seeds. The well-defined morphologies, tailored plasmonic absorbance from visible-light to the near infrared (NIR) region, colloidal stability and biocompatibility are attributed to the synergistic action of CTPR, halide ions, and CTPR-stabilized Ag seeds. We also ascertained that a vast array of biosustainable materials including negatively charged lignin and cellulose derivatives can serve as both a potent stabilizers and an efficient nanocrystal modifiers to regulate the growth of well-defined Ag nanoprisms using a one-pot or seeded growth strategy. The influential effects of reactants and additives including the concentration of sodium lignosulfonate, H2O2 and NaBH4 were studied in great detail. It implies that appropriate physicochemical properties rather than the specific binding sequence of biomaterials are critical for the shaped-controlled growth of Ag NTs and new synthetic paradigms could be proposed based on these findings. Last but not the least, we have demonstrated the resulting APMNs, particularly, Au NSTs and Ag NTs exhibit remarkable colloidal stability, enhanced SERS performance, making them promising materials for biosensing and photothermal therapy. Since the Ag nanoprisms are susceptible to morphological deformation in the presence of strong oxidant, they also hold great potential for the colorimetric sensing of oxidative metal cation species such as Fe3+, Cr3+, etc. / Ph. D. / When a beam of light impinges on the surface of noble metallic nanoparticle (NP), particularly gold (Au) and silver (Ag), the conduction electrons are excited which induces a collective oscillatory motion, resulting in an intense localized surface plasmon resonance (LSPR) absorbance as well as the amplified localized electromagnetic filed. Owing in large part to the tailored LSPR and the intensive electromagnetic field at the sharp corners and edges, anisotropic plasmonic noble metallic nanoparticles (APMNs) can be utilized to span an array of applications such as biosensing, bioimaging, diagnostics and therapeutics. Although great advancement has been made to prepare well-defined APMNs through versatile surfactant-assisted colloidal methodologies, biomedical applications necessitate tedious and rigorous purification processes for the complete removal of toxic surfactants. To address this ubiquitous challenge, biomimetic and bioinspired green synthesis have been extensively explored to fabricate APMNs under mild and ambient conditions. In this dissertation, we aim to develop generic bioenabled synthetic strategies towards APMNs, particularly, Au nanostars and Au/Ag nanoprisms. Herein, protein mediated shape-selective synthesis of APMNs were presented, in which consensus sequence tetratricopetide repeat (CTPR) proteins and biological Good’s buffers were employed as nanocrystal growth modifiers and mild reducing agents, respectively. The dramatic implications of repeat proteins on the morphological and optical properties of the Au NPs were explicitly discussed. The other objective of this dissertation is to elucidate the molecular interactions between inorganic species and biopolymers to further unravel the underlying growth mechanism during the course of APMNs evolution. By incorporation of seeded growth and biomimetic synthesis, Ag/Au nanotriangles (Au NTs) with tunable edge length were synthesized in the presence of the designed CTPR protein, halide anions (Br⁻) and CTPR-stabilized Ag seeds. The well-defined morphologies, tailored plasmonic absorbance from visible-light to the near infrared (NIR) region, colloidal stability and biocompatibility are attributed to the synergistic action of each components in the synthetic system. Last but not the least, we have demonstrated the resulting NPs exhibit remarkable colloidal stability, mitigated cytotoxicity and surface enhanced Raman spectroscopy (SERS) performance, making them good candidates for biosensing and photothermal therapy. This work might shed light on the roles biomolecules play in green synthesis of APMNs, along with rationalizing the design of biomimetic systems to bridge the gap between the bioenabled technique and traditional colloidal synthesis.