Tiziano Sanvito

Do protein crystals nucleate within dense liquid clusters

The evolution of protein-rich clusters and nucleating crystals were characterized by dynamic light scattering (DLS), confocal depolarized dynamic light scattering (cDDLS) and depolarized oblique illumination dark-field microscopy. Newly nucleated crystals within protein-rich clusters were detected directly. These observations indicate that the protein-rich clusters are locations for crystal nucleation.

Single particle optical extinction and scattering allows real time quantitative characterization of drug payload and degradation of polymeric nanoparticles

The behavior of nanoparticles in biological systems is determined by their dimensions, size distribution, shape, surface chemistry, density, drug loading and stability; the characterization of these parameters in realistic conditions and the possibility to follow their evolution in vitro and in vivo are, in most of the cases, far from the capabilities of the standard characterization technologies. Optical techniques such as dynamic light scattering (DLS) are, in principle, well suited for in line characterization of nanoparticle, however their fail in characterizing the evolution of nanoparticle in solution where change in particle dimension and density is present. Here we present an in-line optical technique based on single particle extinction and scattering (SPES) overcoming the limitations typical of DLS and allowing for the efficient characterization of nanoparticle polydispersity, index of refraction and degradation dynamics in solution. Using SPES, we characterized the evolution of PLGA nanoparticles with different structures and drug payloads in solution and we compared the results with DLS. Our results suggest that SPES could be used as a process analytical technology for pharmaceutical nanoparticle production.

Measuring the complex field scattered by single submicron particles

We describe a method for simultaneous measurements of the real and imaginary parts of the field scattered by single nanoparticles illuminated by a laser beam, exploiting a self-reference interferometric scheme relying on the fundamentals of the Optical Theorem. Results obtained with calibrated spheres of different materials are compared to the expected values obtained through a simplified analytical model without any free parameters, and the method is applied to a highly polydisperse water suspension of Poly(D,L-lactide-co-glycolide) nanoparticles. Advantages with respect to existing methods and possible applications are discussed.

Confocal zero-angle dynamic depolarized light scattering

We present a novel Dynamic Depolarized Scattering method based on a tight confocal, zero scattering angle, heterodyne scheme. The method is highly immune from parasitic multiple-scattering contributions, so that it can operate with non-index-matched samples presenting large turbidity. It provides measurements of both rotational and translational diffusion coefficients, the latter via number fluctuation spectroscopy. In addition, the amplitude ratio between the two baselines for the fast rotational mode and the slow translational mode can be used to determine the particles intrinsic birefringence.

Shape and size constraints on dust optical properties from the Dome C ice core, Antarctica

Mineral dust aerosol (dust) is widely recognized as a fundamental component of the climate system and is closely coupled with glacial-interglacial climate oscillations of the Quaternary period. However, the direct impact of dust on the energy balance of the Earth system remains poorly quantified, mainly because of uncertainties in dust radiative properties, which vary greatly over space and time. Here we provide the first direct measurements of the aerosol optical thickness of dust particles windblown to central East Antarctica (Dome C) during the last glacial maximum (LGM) and the Holocene. By applying the Single Particle Extinction and Scattering (SPES) technique and imposing preferential orientation to particles, we derive information on shape from samples of a few thousands of particles. These results highlight that clear shape variations occurring within a few years are hidden to routine measurement techniques. With this novel measurement method the optical properties of airborne dust can be directly measured from ice core samples, and can be used as input into climate model simulations. Based on simulations with an Earth System Model we suggest an effect of particle non-sphericity on dust aerosol optical depth (AOD) of about 30% compared to spheres, and differences in the order of ~10% when considering different combinations of particles shapes.

Single particle extinction and scattering optical method unveils in real time the influence of the blood components on polymeric nanoparticles

Here we report the quantitative in situ characterization of size distribution evolution of polymeric nanoparticles incubated in murine serum, filtered and unfiltered murine blood. We used an analytical optical approach, named Single Particle Extinction and Scattering (SPES), which relies on the measurements of two independent parameters of single particles. SPES is based on a robust self-reference interference optical scheme which allows a rejection of the spurious signals coming from the background caused by the medium. We employed polystyrene nanoparticles as reference system and polydisperse poly(lactic-co-glycolic acid) nanoparticles. Our results demonstrate that SPES can be used for carrying out ex vivo analysis of nanoparticles to evaluate the modifications that NPs undergo in vivo following different routes of entry. Conversely, Dynamic Light Scattering is not able to provide reliable results for these systems due to the presence of the biological components in solution.