Biology subjects

Scarpa, F.

Publications and source records attributed to Scarpa, F..

6 recordsLinked to original sources

bioRxiv2026

Damping nonlinearity in agarose hydrogels under relative humidity: balancing network stiffness and energy dissipation

Sustainable, biodegradable elastomers are needed to replace fossil-based alternatives and reduce the environmental impact of traditional vibration damping materials. We investigate agarose-based hydrogels as eco-friendly vibration absorbers, examining the combined effects of polymer concentration (1-7 wt%), relative humidity (55-98%), and mechanical pre-stress on their dynamic mechanical properties. Frequency-dependent viscoelastic and vibration transmissibility tests, supported by Gaussian Process Regression (GPR), reveal that increasing agarose concentration enhances the storage modulus (E') by over an order of magnitude, reaching[~] 5 MPa depending on humidity and applied prestress. Remarkably, the damping efficiency--characterised by the loss factor (tan(d))--exhibits a highly non-monotonic trend. Maximum energy dissipation is observed at intermediate network densities, with tan(d) up to 0.21 and a loss modulus of[~] 515 kPa at 5 w% and 75% relative humidity, comparable to synthetic elastomers. GPR analysis shows that prestress controls nonlinear stiffening and transmissibility resonance behavior, while shifting peak damping from 5 wt% to 1 wt% agarose as prestress increases. These findings underscore the mechanical tunability and sustainability of agarose hydrogels, providing potential design guidance for biodegradable vibration mitigation materials.

bioengineering↗

bioRxiv2025

Tunable porosity in a hydrogel with extreme vibration damping properties

We have developed hydrogel systems with tunable porosity through dialysis casting by varying alginate and poloxamer compositions from 0% to 10%. These gels feature diverse porosity topologies, yielding loss factors between 16% and 29% in the 50 Hz to 300 Hz frequency range. The dynamic modulus shows a remarkable increase of over an order of magnitude, reaching approximately 3 MPa compared to the static modulus. Vibration transmissibility tests and dynamic mechanical analysis reveal that the poroelastic and pneumatic-like effects from the tunable porous structures contribute significantly to this damping effect. Furthermore, these hydrogels are biosourced and biodegradable, providing a sustainable alternative to conventional fossil-based damping materials.

bioengineering↗

bioRxiv2024

Coagulative Granular Hydrogels with an Enzyme Catalyzed Fibrin Network for Endogenous Tissue Regeneration

Granular hydrogels, composed of densely packed microgels, are an emerging class of injectable microporous scaffolds that provide interstitial porosity for endogenous cell recruitment and tissue repair. However, weak bonding interactions between constituent microgels compromises the mechanical integrity of these biomaterials, limiting their scope and effectiveness for in vivo application where structural support is required. To address this challenge, we introduce a new bioinspired stabilization method and a novel class of regenerative biomaterial: coagulative granular hydrogels, assembled from thrombin-functionalized gelatin methacryloyl microgels. The surface-bound thrombin is enzymatically active and catalyzes the conversion of fibrinogen into a fibrin hydrogel that extends throughout the interstitial voids of the granular hydrogel. This secondary network acts as a biological glue to stabilize the granular hydrogel, yielding shear and compressive properties comparable to bulk hydrogel controls. Furthermore, the interstitial fibrin network provides a favorable microenvironment for the adhesion, proliferation, and invasion of endothelial cells, highlighting the potential of the biomaterial to support endogenous tissue repair. This innovative stabilization mechanism provides a responsive biomaterial system, and future studies will seek to explore how the biomaterial is annealed in vivo by the presence of blood plasma fibrinogen.

bioengineering↗

bioRxiv2022

Genome-based comparison between the recombinant SARS-CoV-2 XBB and its parental lineages

Recombination is the main contributor to RNA virus evolution, and SARS-CoV-2 during the pandemic produced several recombinants. The most recent SARS-CoV-2 recombinant is the lineage labeled XBB, also known as Gryphon, which arose from BJ.1 and BM. 1.1.1. Here we performed a genome-based survey aimed to compare the new recombinant with its parental lineages that never became dominant. Genetic analyses indicated that the recombinant XBB and its first descendant XBB.1 show an evolutionary condition typical of an evolutionary blind background with no further epidemiologically relevant descendant. Genetic variability and expansion capabilities are slightly higher than parental lineages. Bayesian Skyline Plot indicates that XBB reached its plateau around October 6, 2022 and after an initial rapid growth the viral population size did not further expand, and around November 10, 2022 its levels of genetic variability decreased. Simultaneously with the reduction of the XBB population size, an increase of the genetic variability of its first sub-lineage XBB.1 occurred, that in turn reached the plateau around November 9, 2022 showing a kind of vicariance with its direct progenitors. Structure analysis indicates that the affinity for ACE2 surface in XBB/XBB.1 RBDs is weaker than for BA.2 RBD. In conclusion, nowadays XBB and XBB.1 do not show evidence about a particular danger or high expansion capability. Genome-based monitoring must continue uninterrupted in order to individuate if further mutations can make XBB more dangerous or generate new subvariants with different expansion capability.

genetics↗

bioRxiv2022

Genetic and structural data on the SARS-CoV-2 Omicron BQ.1 variant reveal its low potential for epidemiological expansion

The BQ.1 SARS-CoV-2 variant, also known as Cerberus, is one of the most recent Omicron descendant lineages. Compared to its direct progenitor BA.5, BQ.1 carries out some additional spike mutations in some key antigenic site which confer it further immune escape ability over other circulating lineage. In such a context, here we performed a genome-based survey aimed to obtain an as complete as possible nuance of this rapidly evolving Omicron subvariant. Genetic data suggests that BQ.1 represents an evolutionary blind background, lacking of the rapid diversification which is typical of a dangerous lineage. Indeed, the evolutionary rate of BQ.1 is very similar to that of BA.5 (7.6 x 10-4 and 7 x 10-4 subs/site/year, respectively), which is circulating by several months. Bayesian Skyline Plot reconstruction, indicates low level of genetic variability, suggesting that the peak has been reached around September 3, 2022. Structure analyses performed by comparing the properties of BQ.1 and BA.5 RBD indicated that the impact of the BQ.1 mutations on the affinity for ACE2 may be modest. Likewise, immunoinformatic analyses showed modest differences between the BQ.1 and the BA5 potential B-cells epitope. In conclusion, genetic and structural analysis on SARS-CoV-2 BQ.1 suggest that, it does not show evidence about its particular dangerous or high expansion capability. The monitoring genome-based must continue uninterrupted for a better understanding of its descendant and all other lineages.

molecular biology↗

bioRxiv2018

Electrospun Cellulose-Silk Composite Nanofibres Direct Mesenchymal Stem Cell Chondrogenesis in the Absence of Biological Stimulation

Smart biomaterials with an inherent stimulating capacity that elicit specific behaviours in lieu of biological prompts would prove advantageous for regenerative medicine applications. Specific blends of the natural polymers cellulose and silk cast as films can drive the chondrogenic differentiation of human bone marrow mesenchymal stem cells (hMSCs) upon in vitro culture. However, the true potential of such biomaterials for cartilage tissue engineering can be realised upon its three-dimensional fabrication. In this work we employ an electrospinning technique to model the in vivo nanofibrous extracellular matrix (ECM). Cellulose and silk polymers at a mass ratio of 75:25 were regenerated using a trifluoroacetic acid and acetic acid cosolvent system. This natural polymer composite was directly electrospun for the first time, into nanofibers without post-spun treatment. The presence and size of fibre beading was influenced by environmental humidity. The regenerated composite retained the key chemical functionalities of its respective components. Biocompatibility of the natural polymer composite with hMSCs was demonstrated and its inherent capacity to direct chondrogenic stem cell differentiation, in the absence of stimulating growth factors, was confirmed. This physical chondrogenic stimulation was countered biochemically using fibroblast growth factor-2 (FGF-2), a growth factor used to enhance the proliferation of hMSCs. The newly fabricated scaffold provides the foundation for designing a robust, self-inductive, and cost-effective biomimetic biomaterial for cartilage tissue engineering.

bioengineering↗