Hardystonite-based (HT) bioceramic foams were easily obtained via thermal treatment of silicone resins and reactive oxide fillers in air. By using a commercial silicone, incorporating strontium oxide and magnesium oxide precursors (as well as CaO and ZnO), and treating it at 1100 °C, a complex solid solution (Ca1.4Sr0.6Zn0.85Mg0.15Si2O7) that has superior biocompatibility and bioactivity properties compared to pure hardystonite (Ca2ZnSi2O7) can be obtained. Proteolytic-resistant adhesive peptide mapped on vitronectin (D2HVP), was selectively grafted to Sr/Mg-doped HT foams using two different strategies. Unfortunately, the first method (via protected peptide) was unsuitable for acid-sensitive materials such as Sr/Mg-doped HT, resulting in the release of cytotoxic levels of Zinc over time, with consequent negative cellular response. To overcome this unexpected result, a novel functionalization strategy requiring aqueous solution and mild conditions was designed. Sr/Mg-doped HT functionalized with this second strategy (via aldehyde peptide) showed a dramatic increase in human osteoblast proliferation at 6 days compared to only silanized or non-functionalized samples. Furthermore, we demonstrated that the functionalization treatment does not induce any cytotoxicity. Functionalized foams enhanced mRNA-specific transcript levels coding IBSP, VTN, RUNX2, and SPP1 at 2 days post-seeding. In conclusion, the second functionalization strategy proved to be appropriate for this specific biomaterial and was effective at enhancing the material’s bioactivity.
Two nanomicas of similar composition, containing muscovite and quartz, but with different particle size distributions, have been used to prepare transparent epoxy nanocomposites. Their homogeneous dispersion, due to the nano-size, was achieved even without being organically modified, and no aggregation of the nanoparticles was observed, thus maximizing the specific interface between matrix and nanofiller. No exfoliation or intercalation has been observed by XRD, despite the significant dispersion of the filler in the matrix which produced nanocomposites with a loss in transparency in the visible domain of less than 10% in the presence of 1% wt and 3% wt of mica fillers. The presence of micas does not affect the thermal behavior of the nanocomposites, which remains similar to that of the neat epoxy resin. The mechanical characterization of the epoxy resin composites revealed an increased Young’s modulus, whereas tensile strength was reduced. A peridynamics-based representative volume element approach has been implemented to estimate the effective Young’s modulus of the nanomodified materials. The results obtained through this homogenization procedure have been used as input for the analysis of the nanocomposite fracture toughness, which has been carried out by a classical continuum mechanics–peridynamics coupling approach. Comparison with the experimental data confirms the capability of the peridynamics-based strategies to properly model the effective Young’s modulus and fracture toughness of epoxy-resin nanocomposites. Finally, the new mica-based composites exhibit high values of volume resistivity, thus being excellent candidates as insulating materials.
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the etiological agent responsible for the worldwide pandemic and has now claimed millions of lives. The virus combines several unusual characteristics and an extraordinary ability to spread among humans. In particular, the dependence of the maturation of the envelope glycoprotein S from Furin enables the invasion and replication of the virus virtually within the entire body, since this cellular protease is ubiquitously expressed. Here, we analyzed the naturally occurring variation of the amino acids sequence around the cleavage site of S. We found that the virus grossly mutates preferentially at P positions, resulting in single residue replacements that associate with gain-of-function phenotypes in specific conditions. Interestingly, some combinations of amino acids are absent, despite the evidence supporting some cleavability of the respective synthetic surrogates. In any case, the polybasic signature is maintained and, as a consequence, Furin dependence is preserved. Thus, no escape variants to Furin are observed in the population. Overall, the SARS-CoV-2 system per se represents an outstanding example of the evolution of substrate–enzyme interaction, demonstrating a fast-tracked optimization of a protein stretch towards the Furin catalytic pocket. Ultimately, these data disclose important information for the development of drugs targeting Furin and Furin-dependent pathogens.
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