Plasmonics is an important branch of nanophotonics and is the study of the interaction of electromagnetic fields with the free electrons in a metal at metallic/dielectric interfaces or in small metallic nanostructures. The electric component of an exciting electromagnetic field can induce collective electron oscillations known as surface plasmons. Such oscillations lead to the localization of the fields that can be at sub-wavelength scale and to its significant enhancement relative to the excitation fields. These two characteristics of localization and enhancement are the main components that allow for the guiding and manipulation of light beyond the diffraction limit. This thesis focuses on developing plasmonic devices for near and far-field applications. In the first part of the thesis, we demonstrate the detection of single point mutation in peptides from multicomponent mixtures for early breast cancer detection using selfsimilar chain (SCC) plasmonic devices that show high field enhancement and localization. In the second part of this work, we investigate the anomalous reflection of light for TM polarization for normal and oblique incidence in the visible regime. We propose gradient phase gap surface plasmon (GSP) metasurfaces that exhibit high conversion efficiency (up to ∼97% of total reflected light) to the anomalous reflection angle for blue, green and red wavelengths at normal and oblique incidence. In the third part of the thesis, we present a theoretical approach to narrow the plasmon linewidth and enhance the near-field intensity at a plasmonic dimer gap (hot spot) through coupling the electric localized surface plasmon (LSP) resonance of a silver hemispherical dimer with the resonant modes of a Fabry-Perot (FP) cavity. In the fourth part of this work, we demonstrate numerically bright color pixels that are highly polarized and broadly tuned using periodic arrays of metal nanosphere dimers on a glass substrate. In the fifth and final part of the thesis, we propose numerically an approach to narrow the plasmon linewidth and enhance the magnetic near field intensity at a magnetic hot spot in a hybridized metal-insulator-metal (MIM) structure. The computational method used throughout the thesis is the finite-difference time-domain method (FDTD).

Raman spectroscopy is a noninvasive technique that can provide complex information on the vibrational state of the molecules. It defines the unique fingerprint that allow the identification of the various chemical components within a given sample. The aim of the following thesis work is to analyze Raman maps related to three pairs of different cells, highlighting differences and similarities through multivariate algorithms. The first pair of analyzed cells are human embryonic stem cells (hESCs), while the other two pairs are induced pluripotent stem cells (iPSCs) derived from T lymphocytes and keratinocytes, respectively. Although two different multivariate techniques were employed, ie Principal Component Analysis and Cluster Analysis, the same results were achieved: the iPSCs derived from T-lymphocytes show a higher content of genetic material both compared with the iPSCs derived from keratinocytes and the hESCs . On the other side, equally evident, was that iPS cells derived from keratinocytes assume a molecular distribution very similar to hESCs.

In this work a Raman flow cytometer is presented. It is a whole new microfluidic device that takes advantage of basic principles of Raman spectroscopy and fluorescent flow cytometry mixed together in a system of particularly shaped channels. These are indeed composed by specific shape and sizes – thanks to which cells can flow one-by-one – and a trap by means of which cells are trapped in order to perform Raman analysis on single ones in a constant and passive way. In this sense the microfluidic device promotes a fast method to look for single cells in a whole multicellular sample. It is a label-free analysis and this means that, on the contrary of what happens with fluorescent flow cytometry, the sample does not need to undergo any particular time-consuming pretreatment before being analyzed. Moreover it gives a complete information about the biochemical content of the sample thanks to the involvement of Raman spectroscopy as method of analysis. Many thought about a device like this, but eventually it is the first one being designed, fabricated and tested. The materials involved in the production of the Raman flow cytometer are chosen wisely. In particular the chip – the most important component of the device – is multilayered, being composed by a slide of calcium fluoride (which gives a negligible signal in Raman analyses), a photosensitive resist containing a pattern with channels and another slide of calcium fluoride in order for the channels to be sealed on both sides. The chip is, in turn, connected to gaskets and external frames. Several fabrication processes are followed to ultimately get the complete Raman flow cytometer and experiments on red blood cells demonstrate its validity in this field.

The improvement of blood cell sorting techniques in recent years have attracted the attention of many researchers due to the possible benefits that these methods can lead in biology, regenerative medicine, materials science and therapeutic area. In this work a cell sorting technique based on filtration is described. The separation occurs by means of a microfluidic device, suitably designed, manufactured and tested, that is connected to an external experimental set-up. The fabrication process can be divided in two parts: at first it is described the manufacturing process of a filtering membrane, with holes of specific size that allow the passage of only certain cell types. Following the microfluidic device is fabricated through the mechanical micromilling. The membrane and the microdevice are suitably bonded and tested by means of an external connection with syringe pumps that inject blood samples at specific flow rates. The device is designed to separate blood cells and tumor cells only by using differences in size and shape. In particular during the first experiments red blood cells and platelets are sorted from white blood cells; in the other experiments red blood cells and platelets are separated from white blood cells and tumor cells. The microdevice has proven to be very efficient, in fact a capture efficiency of 99% is achieved. For this reason it could be used in identification and isolation of circulating tumor cells, a very rare cancer cell type whose presence in the bloodstream could be symptom of future solid tumor formation. The various experiments have also demonstrated that tumor cells survive even after the separation treatment, and then the suffered stress during the sorting process does not harm the biological sample.

Raman spectroscopy is among the most widely employed methods to investigate the properties of materials in several fields of study. Evolution in materials science allowed us to fabricate suitable substrates, at the nanoscale, capable to enhance the electromagnetic field of the signals coming from the samples which at this range turn out to be in most cases singles or a few molecules. This particular variation of the classical technique is called SERS (Surface Enanched Raman Spectroscopy). In this work, the enhancement of the electromagnetic field is obtained by manipulation of the optical properties of metals with respect to their size. By using electroless deposition (bottom up technique), gold and silver nanoparticles were deposited in nanostructured patterns obtained on silicon wafers by means of electron beam lithography (top down technique). Rhodamine 6G in aqueous solution at extremely low concentration (10-8 M) was absorbed on the resultant dimers and the collection of the Raman spectra demonstrated the high efficiency of the substrates.

Tissue engineering is receiving tremendous attention due to the necessity to overcome the limitations related to injured or diseased tissues or organs. It is the perfect combination of cells and biomimetic-engineered materials. With the appropriate biochemical factors, it is possible to develop new effective bio-devices that are capable to improve or replace biological functions. Latest developments in microfabrication methods, employing mostly synthetic biomaterials, allow the production of three-dimensional (3D) scaffolds that are able to direct cell-to-cell interactions and specific cellular functions in order to drive tissue regeneration or cell transplantation. The presented work offers a rapid and efficient method of 3D scaffolds fabrication by using optical lithography and micro-molding techniques. Bioresorbable polymer poly-ε-caprolactone (PCL) was the material used thanks to its high biocompatibility and ability to naturally degrade in tissues. 3D PCL substrates show a particular combination in the designed length scale: cylindrical shaped pillars with 10μm diameter, 10μm height, arranged in a hexagonal lattice with spacing of 20μm were obtained. The sidewalls of the pillars were nanostructured by attributing a 3D architecture to the scaffold. The suitability of these devices as cell culture technology supports was evaluated by plating NIH/3T3 mouse embryonic fibroblasts and human Neural Stem Cells (hNSC) on them. Scanning Electron Microscopy (SEM) analysis was carried out in order to examine the micro- and nano-patterns on the surface of the supports. In addition, after seeding of cells, SEM and immunofluorescence characterization of the fabricated systems were performed to check adhesion, growth and proliferation. It was observed that cells grow and develop healthy on the bio-polymeric devices by giving rise to well-interconnected networks. 3D PCL nano-patterned pillared scaffold therefore may have considerable potential as effective tool for applications in tissue engineering.