Characterization of transient and progressive pulmonary fibrosis by spatially correlated phase contrast microCT, classical histopathology and atomic force microscopy.

Pulmonary fibrosis (PF) is a severe and progressive condition in which the lung becomes scarred over time resulting in pulmonary function impairment. Classical histopathology remains an important tool for micro-structural tissue assessment in the diagnosis of PF. A novel workflow based on spatial correlated propagation-based phase-contrast micro computed tomography (PBI-microCT), atomic force microscopy (AFM) and histopathology was developed and applied to two different preclinical mouse models of PF - the commonly used and well characterized Bleomycin-induced PF and a novel mouse model for progressive PF caused by conditional Nedd4-2 KO. The aim was to integrate structural and mechanical features from hallmarks of fibrotic lung tissue remodeling. PBI-microCT was used to assess structural alteration in whole fixed and paraffin embedded lungs, allowing for identification of fibrotic foci within the 3D context of the entire organ and facilitating targeted microtome sectioning of planes of interest for subsequent histopathology. Subsequently, these sections of interest were subjected to AFM to assess changes in the local tissue stiffness of previously identified structures of interest. 3D whole organ analysis showed clear morphological differences in 3D tissue porosity between transient and progressive PF and control lungs. By integrating the results obtained from targeted AFM analysis, it was possible to discriminate between the Bleomycin model and the novel conditional Nedd4-2 KO model using agglomerative cluster analysis. As our workflow for 3D spatial correlation of PBI, targeted histopathology and subsequent AFM is tailored around the standard procedure of formalin-fixed paraffin-embedded (FFPE) tissue specimens, it may be a powerful tool for the comprehensive tissue assessment beyond the scope of PF and preclinical research.

Novel setup for rapid phase contrast CT imaging of heavy and bulky specimens.

This work introduces a novel setup for computed tomography of heavy and bulky specimens at the SYRMEP beamline of the Italian synchrotron Elettra. All the key features of the setup are described and the first application to off-center computed tomography scanning of a human chest phantom (approximately 45 kg) as well as the first results for vertical helical acquisitions are discussed.

Mechanical characterization of miniaturized 3D-printed hydroxyapatite parts obtained through vat photopolymerization: an experimental study.

Hydroxyapatite is one of the materials of choice for tissue engineering bone scaffolds manufacturing. Vat photopolymerization (VPP) is a promising Additive Manufacturing (AM) technology capable of producing scaffolds with high resolution micro-architecture and complex shapes. However, mechanical reliability of ceramic scaffolds can be achieved if a high fidelity printing process is obtained and if knowledge of the intrinsic mechanical properties of the constituent material is available. As the hydroxyapatite (HAP) obtained from VPP is subjected to a sintering process, the mechanical properties of the material should be assessed with specific reference to the process parameters (e.g. sintering temperature) and to the specific characteristic size of the microscopic features in the scaffolds. In order to tackle this challenge the HAP solid matrix of the scaffold was mimicked in the form of miniaturized samples suitable for ad hoc mechanical characterization, which is an unprecedented approach. To this purpose small scale HAP samples, having a simple geometry and size similar to that of the scaffolds, were produced through VPP. The samples were subjected to geometric characterization and to mechanical laboratory tests. Confocal laser scanning and Computed micro-Tomography (micro-CT) were used for geometric characterization; while, micro-bending and nanoindentation were used for mechanical testing. Micro-CT analyses have shown a highly dense material with negligible intrinsic micro-porosity. The imaging process allowed quantifying the variation of geometry with respect to the nominal size showing high accuracy of the printing process and identifying printing defects on one specific sample type, depending on the printing direction. The mechanical tests have shown that the VPP produces HAP with an elastic modulus as high as approximately 100GPa and flexural strength of approximately 100MPa. The results of this study have shown that vat photopolymerization is a promising technology capable of producing high quality HAP with reliable geometric fidelity.

Polyvinylidene Fluoride Aerogels with Tailorable Crystalline Phase Composition.

In this work, polyvinylidene fluoride (PVDF) aerogels with a tailorable phase composition were prepared by following the crystallization-induced gelation principle. A series of PVDF wet gels (5 to 12 wt.%) were prepared from either PVDF−DMF solutions or a mixture of DMF and ethanol as non-solvent. The effects of the non-solvent concentration on the crystalline composition of the PVDF aerogels were thoroughly investigated. It was found that the nucleating role of ethanol can be adjusted to produce low-density PVDF aerogels, whereas the changes in composition by the addition of small amounts of water to the solution promote the stabilization of the valuable ß and γ phases. These phases of the aerogels were monitored by FTIR and Raman spectroscopies. Furthermore, the crystallization process was followed by in-time and in situ ATR−FTIR spectroscopy. The obtained aerogels displayed specific surface areas > 150 m2 g−1, with variable particle morphologies that are dependent on the non-solvent composition, as observed by using SEM and Synchrotron Radiation Computed micro-Tomography (SR-µCT).