Structural Characterization of Biomaterials by Means of Small Angle X-rays and Neutron Scattering (SAXS and SANS), and Light Scattering Experiments.

Scattering techniques represent non-invasive experimental approaches and powerful tools for the investigation of structure and conformation of biomaterial systems in a wide range of distances, ranging from the nanometric to micrometric scale. More specifically, small-angle X-rays and neutron scattering and light scattering techniques represent well-established experimental techniques for the investigation of the structural properties of biomaterials and, through the use of suitable models, they allow to study and mimic various biological systems under physiologically relevant conditions. They provide the ensemble averaged (and then statistically relevant) information under in situ and operando conditions, and represent useful tools complementary to the various traditional imaging techniques that, on the contrary, reveal more local structural information. Together with the classical structure characterization approaches, we introduce the basic concepts that make it possible to examine inter-particles interactions, and to study the growth processes and conformational changes in nanostructures, which have become increasingly relevant for an accurate understanding and prediction of various mechanisms in the fields of biotechnology and nanotechnology. The upgrade of the various scattering techniques, such as the contrast variation or time resolved experiments, offers unique opportunities to study the nano- and mesoscopic structure and their evolution with time in a way not accessible by other techniques. For this reason, highly performant instruments are installed at most of the facility research centers worldwide. These new insights allow to largely ameliorate the control of (chemico-physical and biologic) processes of complex (bio-)materials at the molecular length scales, and open a full potential for the development and engineering of a variety of nano-scale biomaterials for advanced applications.

Structural Characterization of Self-Assembling Hybrid Nanoparticles for Bisphosphonate Delivery in Tumors.

Hybrid self-assembling nanoparticles (hsaNPs) encapsulating bisphosphonates (BPs) recently showed very promising results in preclinic experiments for the treatment of brain tumor. However, the poor knowledge on the architecture of hybrid nanovectors is certainly one of the main reasons hampering further clinical and industrial development of these technologies. Here we propose to combine different techniques, that is, small angle neutron scattering (SANS) and X-ray Sscattering (SAXS), with cryo-electron transmission microscopy (cryo-TEM) to study the architecture of the final hsaNPs as well as of the four components before the assembling process. Data analysis based on SANS and SAXS experiments suggested a multiple compartment architecture of the final product, consisting of two bilayers sourrounding a core. Structures consisting of two shells surrounding an internal core were also observed in the cryo-TEM analysis. Such high resolution insight, also combined with size distribution and zeta potential of the NPs, provides exhaustive characterization of hsaNPs encapsulating BPs, and it is aimed at supporting further their clinical and industrial development.

Locating liquid and gas interfaces behind a steel hull: a neutron backscatter tool in action.

Monte Carlo simulations were performed to prove that a neutron backscatter tool can detect liquid (hydrocarbon or water) and gas levels behind steel casings, even when used under water. Consequently such a tool can be applied to the detection of fluid levels in wrecked vessels, which is important for environmentally safe retrieval of oil in these vessels. These simulations enable the efficient optimisation of the experimental conditions, without having to resort to expensive mock-ups.

Measuring the structure of thin soft matter films under confinement: a surface-force type apparatus for neutron reflection, based on a flexible membrane approach.

A unique surface force type apparatus that allows the investigation of a confined thin film using neutron reflection is described. The central feature of the setup consists of a solid substrate (silicon) and a flexible polymer membrane (Melinex(®)). We show that inflation of the membrane against the solid surface provides close and even contact between the interfaces over a large surface area. Both heavy water and air can be completely squeezed out from between the flexible film and the solid substrate, leaving them in molecular contact. The strength of confinement is controlled by the pressure used to inflate the membrane. Dust provides a small problem for this approach as it can get trapped between membrane and substrate to prevent a small part of the membrane from making good contact with the substrate. This results in the measured neutron reflectivity containing a small component of an unwanted reflection, between 10% and 20% at low confining pressures (1 bar) and between 1% and 5% at high confining pressures (5 bar). However, we show that this extra signal does not prevent good and clear information on the structure of thin films being extracted from the neutron reflectivity. The effects of confinement are illustrated with data from a poly(vinyl pyrollidone) gel layer in water, a polyelectrolyte multilayer in water, and with data from a stack of supported lipid-bilayers swollen with D(2)O vapor. The data demonstrates the potential of this apparatus to provide information on the structure of thin films under confinement for a known confining pressure.

A new neutron single-crystal diffractometer dedicated for biological macromolecules (BIX-4).

A new neutron single-crystal diffractometer (BIX-4) has been constructed at 1G-B port of JRR-3M in JAERI. Since at 1G-B port another diffractometer for biology, BIX-3, and a high-resolution powder diffractometer (HRPD) coexist, the monochromator house needed to be reconstructed. The main architecture of BIX-4 is based on that of BIX-3. BIX-4 uses an elastically-bent perfect-Si crystal monochromator and neutron imaging plates as BIX-3. In addition, several optimizations of the monochromator and modifications from previous BIX-3 are carried out. The final gain of the neutron intensity at the detector position is estimated to be 2.5 times larger than previous BIX-3. That higher performance increases the opportunities to apply neutron crystallography to biological macromolecules which give only weak reflections and/or small crystals.