Hybrid hydrogels composed of chitosan (CS) have shown great potential in bone tissue engineering and regeneration. The introduction of polyhedral oligomeric silsesquioxanes (POSS) in the biopolymeric matrix has been demonstrated to improve the rheological and biological properties of the hybrid composites. In this work, we have integrated the favourable features of chitosan (CS) and POSS nanoparticles to design new nanocomposites for bone tissue regeneration, focusing our attention on the effect of POSS concentration within the CS matrix (0.5, 1, and 1.5 equivalents in weight of POSS with respect to CS) on the chemical, physical, rheological, and in vitro biological properties of the final composites. The drug release ability of the synthesized hydrogel scaffolds were also investigated using, as the model drug, ketoprofen, that was included in the scaffold during the gelling procedure, showing a more controlled release for the hybrids with respect to CS (86–91% of drug released after two weeks). The results of the in vitro biological tests performed on human fetal osteoblastic cells (hFOB 1.19) culture demonstrated the great biocompatibility of the hybrid materials. The hybrids, at the different POSS concentrations, showed values of cell mortality superimposable with control cells (11.1 vs. 9.8%), thus revealing the CS/POSS hydrogels as possible candidates for bone tissue engineering applications.

The present review contains a representative sampling of mechanistic studies, which have appeared in the literature in the last 5 years, on 1,3-dipolar cycloaddition reactions, using DFT calculations. Attention is focused on the mechanistic insights into 1,3-dipoles of propargyl/allenyl type and allyl type such as aza-ylides, nitrile oxides and azomethyne ylides and nitrones, respectively. The important role played by various metal–chiral–ligand complexes and the use of chiral eductors in promoting the site-, regio-, diastereo- and enatioselectivity of the reaction are also outlined.

A novel series of C-nucleosides, featuring the presence of a 1,2,3-triazole ring linked to an isoxazolidine system, has been designed as mimetics of the pyrimidine nucleobases. An antiproliferative effect was observed for compounds 17a and 17b: the growth inhibitory effect reaches the 50% in HepG2 and HT-29 cells and increases up to 56% in the SH-SY5Y cell line after 72 h of incubation at a 100 µM concentration.

Quantum chemical topology analyses provide a new way of understanding the synchronicity of organic reactions.