Rigid and concave, 2,4-cis-substituted azetidine derivatives: A platform for asymmetric catalysis.

A series of single enantiomer, 2,4-cis-disubstituted amino azetidines were synthesised and used as ligands for copper-catalysed Henry reactions of aldehydes with nitromethane. Optimisation of ligand substituents and the reaction conditions was conducted. The enantiomeric excess of the formed products was highest when alkyl aldehydes were employed in the reaction (>99% e.e.). The absolute stereochemistry of one representative azetidine derivative salt was determined by analysis of the Flack parameter of an XRD single crystal structure. The origin of selectivity in catalysis was investigated computationally, revealing the importance of the amino-substituent in determining the stereochemical outcome. A racemic platinum complex of a cis-disubstituted azetidine is examined by XRD single crystal structure analysis with reference to its steric parameters, and analogies to the computationally determined copper complex catalyst are drawn. A preliminary example of the use of a cis-disubstituted azetidine scaffold in thiourea H-bonding catalyst is noted in the supporting information

Poly(Vinyl alcohol)/gelatin scaffolds allow regeneration of nasal tissues

Need for regeneration and repair of nasal tissues occurs as a consequence of several pathologies affecting the nose, including, but not limited to infective diseases, traumas and tumor resections. A platform for nasal tissue regeneration was set up using poly(vinyl alcohol)/gelatin sponges with 20%–30% (w/w) gelatin content to be used as scaffolds, for their intrinsic hydrophilic, cell adhesive and shape recovery properties. We propose mesodermal progenitor cells (MPCs) isolated from the bone marrow as a unique stem cell source for obtaining different connective tissues of the nose, including vascular tissue. Finally, epithelial cell immune response to these scaffolds was assessed in vitro in an environment containing inflammatory molecules. The results showed that mesenchymal stromal cells (MSCs) deriving from MPCs could be used to differentiate into cartilage and fibrous tissue; whereas, in combination with endothelial cells still deriving from MPCs, into pre-vascularized bone. Finally, the scaffold did not significantly alter the epithelial cell response to inflammatory insults derived from interaction with bacterial molecules

Property enhancement of healable supramolecular polyurethanes

Low molecular weight additives which can cooperatively self-assemble with supramolecular polyurethanes via complementary hydrogen bonding interactions offer an attractive route to enhancing the properties of addressable polymer networks. Here, we present the design, synthesis, characterisation and mechanical properties of a series of supramolecular polyurethanes with varied loadings of a low molecular weight bis-urea additive. These additives are able to self-assemble with analogous recognition motifs within the supramolecular polyurethanes to form polar ‘hard’ domains, promoting phase separation within the material and, crucially, increasing the strength of the polymer network. In addition, the bis-urea additive is a by-product within the polymerisation and thus can be synthesised in situ, without the need for complex purification or blending. The mechanical properties of these reinforced polymers were enhanced when compared to the pristine supramolecular polyurethane alone, as a result of higher degrees of order within the polymer matrix. Furthermore, a formulation comprising the small molecule blended with the supramolecular polyurethane was produced to examine the effect of material preparation and filler dispersion within the polymer matrix. Interestingly, the mechanical performance of a blended material was diminished as a result of modest dispersion and incorporation within the polymer matrix. These findings thus demonstrate a facile, one-pot, method that does not require purification to produce reinforced supramolecular polyurethanes. This methodology may find use in industrial applications in which enhancements to the physical and mechanical properties can be easily achieved through the in situ synthesis of low molecular weight additives within the polymerisation

Liposome-encapsulated superoxide dismutase mimetic: theranostic potential of an MR detectable and neuroprotective agent

Endogenous manganese based superoxide dismutase (Mn-SOD) provides the primary defense against excess production of potentially toxic superoxide anion (O2 (-) ). M40401 is a synthetic enzyme mimetic that has a catalytic activity rate exceeding that of the native SOD enzymes. The presence of a paramagnetic Mn(II) cation in M40401 suggests that the delivery and spatial distribution of this enzyme mimetic in vivo may be directly detectible using magnetic resonance imaging (MRI); however, the cardiotoxicity of Mn(II) severely limits the use of free M40401 in living systems. To deliver M40401 in vivo in amounts sufficient for MRI detection and to limit potential cardiotoxicity, we encapsulated M40401 into 170 nm liposomes composed of phosphatidylcholine and PEGylated phosphatidylethanolamine to achieve extended circulation in the bloodstream. The obtained liposomes efficiently catalyzed superoxide dismutation in vitro. Using 3 T MRI we investigated the biokinetics of liposome-encapsulated M40401 in mice and found that, in addition to catalyzing superoxide dismutation in vitro, M40401 caused differential and region-specific enhancement of mouse brain after systemic administration. Thus, liposome encapsulated M40401 is an ideal candidate for development as a theranostic compound useful for simultaneous MRI-mediated tracking of delivery as well as for neuroprotective treatment of ischemic brain

POLYVINYL ALCOHOL/GELATIN SPONGES FOR AURICULAR CARTILAGE ENGINEERING

Reconstructing auricle resulting from trauma, neoplasm, or congenital defects is one of the most challenging and diverse tasks in aesthetic and reconstructive surgery due to the highly complex three‐dimensional anatomy of the outer ear [1]. We aimed at providing alternatives to overcome the shortcomings of the standard surgical reconstructive procedures using tissue engineering. Emulsion and freeze‐drying were used to produce poly(vinyl alcohol)/gelatin (PVA/G) sponges at different weight ratios (100/0 ‐ 50/50 w/w%), which were cross‐linked by exposure to glutaraldehyde vapors. PVA/G sponges with highly round‐shaped interconnected pores, highly swelling capacity (> 200%), and an essentially elastic mechanical behaviour were obtained. Different culture conditions were applied to obtain elastic cartilage: , undifferentiated versus chondrogenic pre‐differentiated bone marrow derived human mesenchymal stromal cells (hMSCs), commercial versus hand‐made chondrogenic differentiation medium and static versus dynamic culture [i.e. ultrasound (US) or bioreactor stimulation] were used. After three weeks, the constructs were analyzed via immunohistochemistry (IHC). Intense glycosaminoglycan, glycoprotein and collagen syntheses by hMSCs were most frequently observed using the commercial medium, while round morphology was observed when pre‐differentiated hMSCs were seeded. The application of US stimulation during the culture on cell/scaffold constructs enhanced extracellular matrix deposition and led to 30% higher collagen type II expression at gene level. However, at protein level, collagen type II, aggrecan and elastin formation were observed via IHC only by using bioreactor culture. Results showed that 70/30 (w/w%) PVA/G sponge is a suitable scaffold for auricle reconstruction

A thermoreversible supramolecular polyurethane with excellent healing ability at 45 °C

We report the synthesis and characterization of a healable, elastomeric shape recovery supramolecular polyurethane whose properties result from self-complementary π−π stacking and hydrogen bonding interactions plus phase separation. ESEM analysis and photographic images have revealed that this material can heal at 45 °C in 15 min to recover the mechanical properties of the pristine material with healing efficiencies >99%. This supramolecular polyurethane is also able to recover an applied strain of 25% within 5 min of release of the load