We discuss the use of Brillouin Light Scattering Microspectroscopy (BLSM) on Liquid Biopsies for obtaining complementary information in the diagnosis of different diseases. The viscoelastic properties of blood are known to play an important role for many processes necessary for survival including tissue perfusion, oxygen delivery and general circulation. They are understood to be dominated by the dense red blood cell suspension, with the plasma often modelled as a Newtonian fluid serving as an extracellular matrix. Much effort has been devoted to studying the mechanical properties of red blood cells, variations of which have been linked to numerous hereditary and metabolic disorders. Recent studies have shown also a non-Newtonian viscoelastic behavior of plasma. Though the biochemical composition of plasma can change at the onset of diseases, it is unclear if and how the structural-mechanical properties are affected. Here we discuss the measurement of the high-frequency viscoelastic properties of plasma from diseased blood using BLSM. BLSM utilizes the inelastic scattering of light from inherent thermal density fluctuations (acoustic phonons) to derive mechanical parameters such as the Longitudinal Storage and Loss Moduli. Since BLSM probes very fast relaxation processes it can be sensitive to structural/conformational changes of macromolecules. By mapping the variation and scaling of the storage and loss parameters also as a function of dilution and temperature we observe subtle differences between plasma from healthy and diseased samples. We discuss possible origins of these differences, and their potential for complementing liquid biopsies.
The effect of a population of fluorophores coupling to weakly bound surface plasmons in dielectric/metal/dielectric
structures is investigated for the purpose of fluorescence enhancement near interfaces and live cell fluorescence
surface imaging. We show theoretically and experimentally that for sufficient fluorophore concentrations near such SPP supporting structures significant enhancements in the radiative emission intensity can be observed, with a spectral modification that can be correlated to the average separation of the fluorophores from the substrate. We will discuss the theory behind the effect and some experimental results on imaging labeled proteins in the focal adhesion sites of cells.
We have theoretically investigated the effects of temperature on the superlensing properties of single metal
and stacked metal-dielectric films. We find that decreasing the temperature usually has the effect of slightly
lowering the optimum operating frequency of the superlens. The imaging performance of various designs are
evaluated by analytic calculations and simulations. Accurate modeling of the temperature dependence on the
focusing/imaging properties of such structures is important for many potential applications and may in certain
suggested cases lead to direct applications as e.g. local temperature sensing.
Structures consisting of layered metallic films can be designed to have evanescent transmission and reflection
coefficients that oscillate as a function of transverse wavevector and frequency. When combined with an exit face
diffraction grating, a setup can be realized where for different frequencies one has different spatial components
of an incident field scattered into the dominant propagating order behind the grating. One is thereby able to
simultaneously gather information over a larger range of evanescent field components by combining measurements
at more than one frequency. For sources emitting over the relevant frequency ranges, it becomes possible
to reconstruct a higher ("super") resolution image in the far-field without the need for mechanical scanning or
consecutive measurements. We present calculations and simulations demonstrating the operation of the proposed
technique at visible frequencies along with some preliminary experimental results on the transmission properties
of the proposed metal/dielectric stacks.