Rat-tail tendon fiber SAXS high-order diffraction peaks recovered by a superbright laboratory source and a novel restoration algorithm

Angular super-resolution retrieval in small-angle X-ray scattering

Small-angle X-ray scattering (SAXS) techniques enable convenient nanoscopic characterization for various systems and conditions. Unlike synchrotron-based setups, lab-based SAXS systems intrinsically suffer from lower X-ray flux and limited angular resolution. Here, we develop a two-step retrieval methodology to enhance the angular resolution for given experimental conditions. Using minute hardware additions, we show that translating the X-ray detector in subpixel steps and modifying the incoming beam shape results in a set of 2D scattering images, which is sufficient for super-resolution SAXS retrieval. The technique is verified experimentally to show superior resolution. Such advantages have a direct impact on the ability to resolve finer nanoscopic structures and can be implemented in most existing SAXS apparatuses both using synchrotron- and laboratory-based sources.

Interfibrillar packing of bovine cornea by table-top and synchrotron scanning SAXS microscopy

Bovine cornea was studied with scanning small-angle X-ray scattering (SAXS) microscopy, by using both synchrotron radiation and a microfocus laboratory source. A combination of statistical (adaptive binning and canonical correlation analysis) and crystallographic (pair distribution function analysis) approaches allowed inspection of the collagen lateral packing of the supramolecular structure. Results reveal (i) a decrease of the interfibrillar distance and of the shell thickness around the fibrils from the periphery to the center of the cornea, (ii) a uniform fibril diameter across the explored area, and (iii) a distorted quasi-hexagonal arrangement of the collagen fibrils. The results are in agreement with existing literature. The overlap between laboratory and synchrotron-radiation data opens new perspectives for further studies on collagen-based/engineered tissues by the SAXS microscopy technique at laboratory-scale facilities.

SUNBIM: a package for X-ray imaging of nano- and biomaterials using SAXS, WAXS, GISAXS and GIWAXS techniques

SUNBIM(supramolecular and submolecular nano- and biomaterials X-ray imaging) is a suite of integrated programs which, through a user-friendly graphical user interface, are optimized to perform the following: (i)q-scale calibration and two-dimensional → one-dimensional folding on small- and wide-angle X-ray scattering (SAXS/WAXS) and grazing-incidence SAXS/WAXS (GISAXS/GIWAXS) data, also including possible eccentricity corrections for WAXS/GIWAXS data; (ii) background evaluation and subtraction, denoising, and deconvolution of the primary beam angular divergence on SAXS/GISAXS profiles; (iii) indexing of two-dimensional GISAXS frames and extraction of one-dimensional GISAXS profiles along specific cuts; (iv) scanning microscopy in absorption and SAXS contrast. The latter includes collection of transmission and SAXS data, respectively, in a mesh across a mm2area, organization of the as-collected data into a single composite image of transmission values or two-dimensional SAXS frames, analysis of the composed data to derive the absorption map and/or the spatial distribution, and orientation of nanoscale structures over the scanned area.

An optimized table-top small-angle X-ray scattering set-up for the nanoscale structural analysis of soft matter

The paper shows how a table top superbright microfocus laboratory X-ray source and an innovative restoring-data algorithm, used in combination, allow to analyze the super molecular structure of soft matter by means of Small Angle X-ray Scattering ex-situ experiments. The proposed theoretical approach is aimed to restore diffraction features from SAXS profiles collected from low scattering biomaterials or soft tissues, and therefore to deal with extremely noisy diffraction SAXS profiles/maps. As biological test cases we inspected: i) residues of exosomes' drops from healthy epithelial colon cell line and colorectal cancer cells; ii) collagen/human elastin artificial scaffolds developed for vascular tissue engineering applications; iii) apoferritin protein in solution. Our results show how this combination can provide morphological/structural nanoscale information to characterize new artificial biomaterials and/or to get insight into the transition between healthy and pathological tissues during the progression of a disease, or to morphologically characterize nanoscale proteins, based on SAXS data collected in a room-sized laboratory.

Coherent x-ray imaging of collagen fibril distributions within intact tendons

The characterization of the structure of highly hierarchical biosamples such as collagen-based tissues at the scale of tens of nanometers is essential to correlate the tissue structure with its growth processes. Coherent x-ray Bragg ptychography is an innovative imaging technique that gives high resolution images of the ordered parts of such samples. Herein, we report how we used this method to image the collagen fibrillar ultrastructure of intact rat tail tendons. The images show ordered fibrils extending over 10-20 μm in length, with a quantifiable D-banding spacing variation of 0.2%. Occasional defects in the fibrils distribution have also been observed, likely indicating fibrillar fusion events.

Performance of polycapillary X-ray optics for confocal energy-dispersive small-angle X-ray scattering

A confocal energy-dispersive small-angle X-ray scattering (EDSAXS) setup based on polycapillary optics was designed. In this confocal EDSAXS setup, a polycapillary slightly focusing X-ray lens (PSFXRL) and a polycapillary parallel X-ray lens (PPXRL) with a long input focal distance were placed confocally in the excitation channel and detection channel, respectively. This confocal configuration was helpful in improving the signal-to-noise ratio of the EDSAXS. The high gain in power density of the PSFXRL and PPXRL decreased the power requirement of the X-ray source for EDSAXS. The confocal EDSAXS technology could be used to perform nondestructive andin situanalysis of samples such as milk powder in its packaging.