High-contrast-resolution single nanoparticle spectroscopy with MEMS-scanning mirrors based polarization-interferometric laser microscope

Modern nanoparticle synthesis techniques have enable the development of nanoscale materials with unique optical properties for a wide range of applications, including cancer therapeutics and biomolecule detection.... [ view full abstract ]

Modern nanoparticle synthesis techniques have enable the development of nanoscale materials with unique optical properties for a wide range of applications, including cancer therapeutics and biomolecule detection. Particularly, nanoparticulate drug delivery systems (DDS) have attracted a lot of attention because of their size- and dopant-dependent characteristics. Nano formulations can be tailored to meet a wide range of product requirements dictated by disease condition, route of administration and considerations of cost, product stability, toxicity and efficacy. In addition, surface area to volume ratio in nanoparticles have a significant effect on the nanoparticles properties. Nanoparticles have a relative larger surface area when compared to the same volume of the material. Nanoparticles have a much greater surface area per unit volume compared with the larger particles. It leads to nanoparticles more chemically reactive. Single particle characterization is particularly important for the application of cancer therapeutics.

   We have been focusing on spectroscopic analysis of a single polymer DDS nanoparticle with a polarization-interferometric nonlinear confocal microscope to analyze the nanoparticle at high CTF (Contrast Transfer Function) and high spatial resolution. The polarization-interferometric confocal microscopy is a label-free imaging technique allowing visualization of transparent single nanoparticle with CW (Continuous Wave) oscillators and simple optical elements. MEMS (Micro Electro Mechanical Systems) components included facilitate the control of the laser beam that is necessary to scan the sample in nanometer scale. We have demonstrated the nano region spectroscopy of a single 200-nm nanoparticle by vectorial polarization-interferometric technique that performs the electric field subtraction of the scattered light from tens-of-nanometer-scale target and the reference light. We have succeeded in evaluating surface condition of the DDS nanoparticle and dopant distribution in it. Also, polarization analysis estimated the molecular density, molecular orientation and refractive index difference between major and minor axes.