<p>The prevalence of cancer has increasingly become a significant threat to human health and as such, there exists a strong need for developing novel methods for early detection and effective therapy. Nanotheranostics, a combination of diagnostic and therapeutic functions into a single nanoplatform, has great potential to be used for cancer management by allowing detection, real-time tracking, image-guided therapy and therapeutic response monitoring. Gold nanostars (GNS) with tip-enhanced plasmonics have become one of the most promising platforms for cancer nanotheranostics. This work is aimed at addressing the challenges of sensitive cancer detection, metastasis treatment and recurrence prevention by combining state-of-the-art nanotechnology, molecular imaging and immunotherapy. A multifunctional GNS nanoprobe is developed with capabilities ranging from non-invasive, multi-modality cancer detection using positron emission tomography (PET), magnetic resonance imaging (MRI) and X-ray computed tomography (CT), to intraoperative tumor margin delineation with surface enhanced Raman spectroscopy (SERS) and high-resolution nanoprobe tracking with two-photon photoluminescence (TPL), as well as cancer treatment with photoimmunotherapy. The GNS nanoprobe with PET scans is particularly exceptional in detecting brain malignancies as small as 0.5 mm. To the best of our knowledge, the developed GNS nanoprobe for PET imaging provides the most sensitive means of brain tumor detection reported so far. In addition, the GNS nanoprobe exhibits superior performance as photon-to-heat transducer and can be used for specific photothermal therapy (PTT). More importantly, GNS-mediated PTT combined with checkpoint inhibitor immunotherapy has been found to trigger a memorized immunoresponse to treat cancer metastasis and prevent recurrence in mouse model studies. Furthermore, a 6-month in vivo toxicity study including body weight monitoring, blood chemistry test and histopathology examination demonstrate GNS nanoparticles’ biocompatibility. Therefore, the multifunctional GNS nanoprobe exhibits superior cancer detection and treatment capabilities and has great promise for future clinical translation in cancer management.</p> / Dissertation

The overarching objective of the investigations discussed herein is the development of a model experimental system for surface-enhanced infrared absorption (SEIRA) spectroscopy, with potential applicability in higher order infrared spectroscopic techniques, specifically, surface-enhanced two-dimensional infrared (SE-2D IR) spectroscopy. Theoretical predictions that accurately predict the stability of functionalized nanoparticles enable guided design of their properties but are often limited by the accuracy of the parameters used as model inputs. Hence, first, such parameterization limitations for the extended DLVO (xDLVO) theory are overcome using a size-dependent Hamaker constant for gold, interfacial surface potentials, and tilt angles of self-assembled monolayers (SAMs), which collectively improves the predictive power of xDLVO theory for modeling nanoparticle stability. Measurements of electrical properties of functionalized gold nanoparticles validate the predictions of xDLVO theory using these new parameterizations illustrating the potential for this approach to improve the design and control of the properties of functionalized gold nanoparticles in various applications. Next, a series of experiments were conducted to elucidate the behavior of various infrared active molecules in the presence of spherical gold nanoparticles of average diameter ∼20 nm. Here, the spectroscopic anomalies, specifically the shifted vibrational frequency and the dispersive lineshape observed in the infrared spectra for SCN- in the presence of gold nanoparticles provide direct evidence of SIERA. Nevertheless, it was evidenced that nanomaterial with plasmonic properties that extends into the infrared wavelengths are imperative in observing efficient infrared enhancements. Hence, nanomaterial indicating plasmonic properties extending into the infrared wavelengths were synthesized via a straightforward, seedless, one-pot synthesis. The gold nanostars prepared here indicated plasmonic behavior clearly extending into the near infrared, with simple plasmonic tunability via changing the buffer concentration used during synthesis. The systematic understanding achieved here in terms of theoretical prediction of nanoparticle stability, origin of infrared spectral anomalies in the presence of nanomaterials, and the preparation of infrared plasmonic material, collectively provides a resilient framework for the further investigation of surface-enhanced infrared spectroscopic techniques including SEIRA and SE-2D IR spectroscopies.

<p>There is an urgent need to develop practical and effective systems to detect diseases, such as cancer, infectious diseases and cardiovascular diseases.</p><p>Nanotechnology is a new, maturing field that employs specialized techniques to detect and diagnose infectious diseases. To this end, there have been a wealth of techniques that have shown promising results, with fluorescence and surface-enhanced Raman scattering being two important optical modalities that are utilized extensively. The progress in this specialized niche is staggering and many research groups in academia, as well as governmental and corporate organizations, are avidly pursuing leads which have demonstrated optimistic results.</p><p>Although much fundamental science is still in the pipeline under the guise of both ex-vivo and in-vivo testing, it is ultimately necessary to develop diagnostic devices that are able to impact the greatest number of people possible, in a given population. Such systems make state-of-the-art technology platforms accessible to a large population pool. The development of such technologies provide opportunities for better screening of at-risk patients, more efficient monitoring of disease treatment and tighter surveillance of recurrence. These technologies are also intrinsically low cost, facilitating the large scale screening for disease prevention.</p><p>Fluorescence has long been established as the optical transduction method of choice, because of its wealth of available dyes, simple optical system, and long heritage from pathology. The intrinsic limitations of this technique, however, have given rise to a complementary, and more recent, modality: surface-enhanced Raman scattering (SERS). There has been an explosive interest in this technique for the wealth of information it provides without compromising its narrow spectral width.</p><p>A number of novel studies and advances are successively presented throughout this study, which culminate to an advanced SERS-based platform in the last chapter.</p><p>The finite element method algorithm is critically evaluated against analytical solutions as a potential tool for the numerical modeling of complex, three-dimensional nanostructured geometries. When compared to both the multipole expansion for plane wave excitation, and the Mie-theory with dipole excitation, this algorithm proves to provide more spatially and spectrally accurate results than its alternative, the finite-difference time domain algorithm.</p><p>Extensive studies, both experimental and numerical, on the gold nanostar and Nanowave substrate for determining their potential as SERS substrates, constituted the second part of this thesis. The tuning of the gold nanostar geometry and plasmon band to optimize its SERS properties were demonstrated, and significant 3-D modeling was performed on this exotic shape to correlate its geometry to the solution's exhibited plasmon band peak position and large FWHM. The Nanowave substrate was experimentally revived and its periodic array of E-field hotspots, which was until recently only inferred, was finally demonstrated via complex modeling.</p><p>Novel gold- and silver- coated magnetic nanoparticles were synthesized after extensive tinkering of the experimental conditions. These plasmonics-active magnetic nanoparticles were small and displayed high stability, were easy to synthesize, exhibited a homogeneous distribution, and were easily functionalizable with Raman dye or thiolated molecules.</p><p>Finally, bowtie-shaped cobalt micromagnets were designed, modeled and fabricated to allow the controllable and reproducible concentrating of plasmonics-active magnetic nanoparticles. The external application of an oscillating magnetic field was accompanied by a cycling of the detected SERS signal as the nanoparticles were concentrated and re-dispersed in the laser focal spot. This constituted the first demonstration of magnetic-field modulated SERS; its simplicity of design, fabrication and operation opens doors for its integration into diagnostic devices, such as a digital microfluidic platform, which is another novel concept that is touched upon as the final section of this thesis.</p> / Dissertation

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.

Abstract This thesis reports on studies of plasmonic nanoparticles and particularly gold nanostars as signal enhancers and contrast agents for biophotonic applications including visualisation, treatment of living cells and chemical sensing. In this thesis, the optical properties of nanoparticles of different size and morphology and their silica composites were compared. Because they are the most suitable plasmonic nanostructures, gold nanostars were utilised for optical imaging modalities such as confocal microscopy and Doppler optical coherence tomography. The ability of gold nanoparticles to enhance the signal in surface-enhanced vibrational spectroscopy, including Raman and Fourier transform infrared spectroscopy was additionally studied. Finally, various gold nanoparticles were applied for cell optoporation to increase the penetration ability of exogeneous substances. In summary, significant advantages of nanostars such as their low-toxicity, high scattering and contrast abilities, in addition to a broad, tunable, plasmon resonance wavelength range, as well as the capability to enhance the signal of analyte molecules in vibrational spectroscopy were demonstrated in this thesis. The results of this study on the effectiveness of nanostars have a broad scope of utility and open a wide perspective for their utilisation in nanobiophotonics and biomedicine. / Tiivistelmä Tämä opinnäytetyö kertoo tutkimuksista, joissa plasmoninanopartikkeleita ja erityisesti kultananotähtiä on käytetty signaalinvahvistimina biofotoniikan sovelluksissa, kuten visualisointi, elävien solujen käsittely ja kemiallinen tunnistus. Tässä työssä verrattiin eri kokoisten ja muotoisten nanopartikkeleiden ja niiden piioksidikomposiittien optisia ominaisuuksia. Sopivimpina plasmoninanorakenteina kultananotähtiä käytettiin optisiin kuvantamismenetelmiin, kuten konfokaalimikroskopiaan ja Doppler-optiseen koherenssitomografiaan. Lisäksi kuvattiin myös kultananopartikkelien kykyä parantaa pinta-aktivoidun värähtelevän spektroskopian signaalia, mukaan lukien Raman- ja Fourier-muunnos-infrapuna-spektroskopia. Lopuksi, eri kultananopartikkeleita käytettiin soluoptoporaatioon eksogeenisten aineiden läpäisevyyden lisäämiseksi. Yhteenvetona, työssä osoitettiin nanotähtien merkittävät edut, kuten matala-myrkyllisyys, suuret sironta- ja kontrastiominaisuudet, laaja plasmoniresonanssin aallonpituusalue ja sen viritettävyys, sekä kyky parantaa analyyttimolekyylien signaalia värähtelyspektroskopiassa. Niinpä tutkimustulokset nanotähtien tehokkuudesta ovat laajasti käyttökelpoisia ja ne avaavat laajan näkökulman niiden hyödyntämiseen nanobiofotoniikassa ja biolääketieteessä.