Biology subjects

Villanova, J.

Publications and source records attributed to Villanova, J..

4 recordsLinked to original sources

bioRxiv2025

3D X-ray microscopy lights up nanoparticles in plants

The discovery of novel plant fertilization strategies heavily relies on our capabilities to probe physiological processes in living plants with sub-cellular precision. State-of-the-art microscopy techniques are in general limited to surface investigation or they require elaborated tissue preparation and often destruction. X-ray microscopy has the potential to resolve some of these limitations by generating micro-to nanometer-scale 3D images deep into the tissue. We introduce experimental designs and the quantitative analysis methodologies, pioneering nanoscale ({approx}150 nm resolution) in-vivo 3D microscopy of plant tissue. We show the first direct in-vivo visualization of foliar-applied untagged nanoparticulate fertilizers deep under the leaf surface, not accessible by other microscopy methods. Ultimately, our approach provides the means for a direct observation of nanoparticle transport and dissolution in living plant tissue, a step critical for developing sustainable plant fertilization approaches.

plant biology↗

bioRxiv2024

Revealing the Auxetic Behavior of Biomimetic Multi-material and Region-specific Nanofibrous Scaffolds via Synchrotron Multiscale Digital Volume Correlation: Innovative Building Blocks for the Enthesis Regeneration

Enthesis lesions are one of the prevalent causes of injuries in the tendon tissue. The gradient of mineralization, extracellular matrix organization and auxetic mechanical properties, make enthesis regeneration challenging. Innovative electrospun fascicle-inspired nanofibrous poly(L-lactic)acid/collagen type I blend scaffolds were developed. Specifically, a mineralized fibrocartilage-inspired region (with/without nano-mineralization with hydroxyapatite), where random and aligned nanofibers coexist, is connected to a tendon-like region made of aligned nanofibers, through a conical non-mineralized fibrocartilage-inspired junction. Scanning electron microscopy and synchrotron nano-tomography show the morphological biomimicry of scaffolds with the natural tendon fascicles. Human mesenchymal stromal cells spheroids cultures confirm a balanced expression of both tendon, cartilage and bone markers on the non-mineralized scaffolds compared with the mineralized ones. Mechanical tests, at different physiological strain-rates, reveal a biomimetic mechanical behavior of scaffolds and the ability of junctions to tune the mechanics of their surrounding sites. Multiscale synchrotron in situ tensile tests, coupled with Digital Volume Correlation, elucidate the full-field strain distribution of scaffolds from the structural down to the nanofiber level, highlighting the auxetic mechanical behavior of junctions typical of the natural enthesis. The findings and cutting-edge investigations of our study suggest the suitability of these enthesis-inspired fascicles as innovative scaffolds for enhanced enthesis regeneration.

bioengineering↗

bioRxiv2020

Incredible internal strains within a biogenic single crystal viewed by X-ray diffraction tomography

The dorsal arm plates (DAPs) of the Ophiocoma Wendtii brittle star are highly functional single crystalline biominerals whose optimized structure and nanostructure enable them to fullfill mechanical and optical functions in the organism. Here, a large DAP bulk piece is characterized by means of synchrotron X-ray Diffraction Tomography (XRDT). This non-destructive crystallographic characterization revealed an astounding feature: the presence of very high compressive strains which relax when the mineral is cracked or grinded into a powder. Thus, previous destructive characterization techniques did not allow their detection. We attribute the compressive strains to the previously identified high-Mg calcite particles, which are coherently included and thereby compress the low-Mg calcite matrix. The measured slice contained both the bulk DAP sample as well as DAP powder. The data generated by the bulk piece could be separated from those by the powder, and the latter was used to calibrate and interprete the former. This study reveals yet another awe-inspiring feature of a biogenic structure, highlights the importance of non-destructive crystallographic characterization for biominerals, and exemplifies the potential of XRDT use in studying a single crystalline material, as well as the advantage of complementary measurement of bulk and powder for data calibration and interpretation.

bioengineering↗

bioRxiv2019

Medicago truncatula Ferroportin2 mediates iron import into nodule symbiosomes

Iron is an essential cofactor for symbiotic nitrogen fixation. It is required by many of the enzymes facilitating the conversion of N2 into NH4+ by endosymbiotic bacteria living within root nodule cells, including signal transduction proteins, O2 homeostasis systems, and nitrogenase itself. Consequently, host plants have developed a transport network to deliver essential iron to nitrogen-fixing nodule cells. Model legume Medicago truncatula Ferroportin2 (MtFPN2) is a nodule-specific gene that encodes an iron-efflux protein. MtFPN2 is located in intracellular membranes in the nodule vasculature, and in the symbiosome membranes that contain the nitrogen-fixing bacteria in the differentiation and early-fixation zones of the nodules. Loss-of-function of MtFPN2 leads to altered iron distribution and speciation in nodules, which causes a reduction in nitrogenase activity and in biomass production. Using promoters with different tissular activity to drive MtFPN2 expression in MtFPN2 mutants, we determined that MtFPN2-facilitated iron delivery across symbiosomes is essential for symbiotic nitrogen fixation, while its presence in the vasculature does not seem to play a major role in in the conditions tested.

plant biology↗