Hemostatic Cryogels Based on Oxidized Pullulan/Dopamine with Potential Use as Wound Dressings

The impetus for research into hydrogels based on selectively oxidized polysaccharides has been stimulated by the diversity of potential biomedical applications. Towards the development of a hemostatic wound dressing in this study, we creatively combined the (hemi)acetal and Schiff base bonds to prepare a series of multifunctional cryogels based on dialdehyde pullulan and dopamine. The designed structures were verified by NMR and FTIR spectroscopy. Network parameters and dynamic sorption studies were correlated with environmental scanning microscopy results, thus confirming the successful integration of the two components and the opportunities for finely tuning the structure–properties balance. The viscoelastic parameters (storage and loss moduli, complex and apparent viscosities, zero shear viscosity, yield stress) and the structural recovery capacity after applying a large deformation were determined and discussed. The mechanical stability and hemostatic activity suggest that the optimal combination of selectively oxidized pullulan and dopamine can be a promising toolkit for wound management

N-Hydroxyphthalimide Anchored on Diamond Nanoparticles as a Selective Heterogeneous Metal-free Oxidation Catalyst of Benzylic Hydrocarbons and Cyclic Alkenes by Molecular O2

This is the peer reviewed version of the following article: Blandez, Juan F., Navalón Oltra, Sergio, Alvaro Rodríguez, Maria Mercedes, García Gómez, Hermenegildo. (2018). N-Hydroxyphthalimide Anchored on Diamond Nanoparticles as a Selective Heterogeneous Metal-free Oxidation Catalyst of Benzylic Hydrocarbons and Cyclic Alkenes by Molecular O2.ChemCatChem, 10, 1, 198-205. DOI: 10.1002/cctc.201700886 , which has been published in final form at http://doi.org/10.1002/cctc.201700886. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] N-hydroxyphthalimide (NHPI) derived from trimellitic anhydride has been covalently anchored (4wt%) through ester bonds to the surface of commercial diamond nanoparticles previously functionalized by chemical and thermal treatments (DH). IR spectroscopy of the NHPI/DH solid shows the presence of a characteristic peak at 1735cm(-1) attributable to the ester bond, while solid-state MAS (CNMR)-C-13 spectroscopy shows two broad bands corresponding to carbon atoms of carbonyl groups (167ppm) and aromatic carbons (127ppm). NHPI/DH promotes autoxidation of isobutylbenzene involving superoxide (O-2(.-)) and hydroperoxide (HOO) radicals; NHPI/DH can be reused at least three times and reach a minimum turnover number as high as 20600, which is probably due to the inertness of the diamond surface, allowing free diffusion of reactive oxygen species. Analogous materials in which NHPI was anchored on activated carbon and multiwall carbon nanotubes were inefficient as autoxidation catalysts. NHPI/DH is able to promote also selective aerobic oxidation of other benzylic hydrocarbons and cycloalkenes.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2015-69153-CO2-R1 and CTQ2014-53292-R and Generalitat Valenciana (Prometeo 2013/14) and is grateful acknowledged. S.N. is thankful for financial support by Fundacion Ramon Areces (XVIII Concurso Nacional, Ciencias de la Vida y de la Materia, Energia renovable: materiales y procesos 2016).Blandez, JF.; Navalón Oltra, S.; Alvaro Rodríguez, MM.; García Gómez, H. (2018). N-Hydroxyphthalimide Anchored on Diamond Nanoparticles as a Selective Heterogeneous Metal-free Oxidation Catalyst of Benzylic Hydrocarbons and Cyclic Alkenes by Molecular O2. ChemCatChem. 10(1):198-205. https://doi.org/10.1002/cctc.201700886S19820510

Chitosan Schiff-Base Hydrogels—A Critical Perspective Review

Chitosan is quite a unique polysaccharide due to the presence of the amine groups naturally occurring in its structure. This feature renders it into a polycation which makes it appealing for preparing polyelectrolyte complexes or imine bonds gels. Therefore, the vast majority of hydrogels prepared using Schiff base chemistry have chitosan as one component. Usually, the counterpart is a low molecular weight aldehyde or a macromolecular periodate-oxidized polysaccharide, i.e., cellulose, pullulan, starch, alginate, hyaluronic acid, etc. Indisputable advantages of hydrogels include their quick gelation, no need for crosslinking agents, and self-healing and injectability properties. This gives grounds for further research, both fundamental in materials science and applicative in various domains. This article is a critical assessment of the most relevant aspects of this topic. It also provides a short review of some of the most interesting research reported in the literature supporting the main observations of this perspective

Mechanisms of reaction of aminoxyl (nitroxide), iminoxyl, and imidoxyl radicals with alkenes and evidence that in the presence of lead tetraacetate, N-hydroxyphthalimide reacts with alkenes by both radical and nonradical mechanisms

1,2-Dideuterio-cyclohexene, 1,2-dideuterio-cyclooctene, and trans-3,4-dideuterio-hex-3-ene were reacted with three >NO. radicals: 4-hydroxyTempo, di-tert-butyliminoxyl, both used as the actual radicals, and phthalimide-N-oxyl (PINO) generated from N-hydroxyphthalimide (NHPI) by its reaction with tert-alkoxyl radicals (t-RO.) and with lead tetraacetate. In all cases, except the NHPI/Pb(OAc)4 system, only mono >NO.-substituted alkenes were produced. The 2H NMR spectra imply that 88-92% of monoadducts were formed by the initial abstraction of an allylic H-atom, followed by capture of the allylic radical by a second >NO., while the remaining 12-8% appear to be formed by an initial addition of >NO. to the double bond followed by H-atom abstraction by a second >NO.. A substantial and sometimes the major product formed with the NHPI/Pb(OAc)4 system has two PINO moieties added across the double bond. Since such diadducts are not formed with the NHPI/t-RO. system, a heterolytic mechanism is proposed, analogous to that known for the Pb(OAc)4-induced acetoxylation of alkenes. A detailed analysis of the NHPI/Pb(OAc) 4/alkene products indicates that monosubstitution occurs by both homolytic and heterolytic processes. \ua9 2005 American Chemical Society.Peer reviewed: YesNRC publication: Ye

Distinguishing between abstraction and addition as the first step in the reaction of a nitroxyl radical with cyclohexene

An unambiguous method for distinguishing between abstraction-addition and addition-abstraction mechanisms (and mixtures thereof) in the reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl with a specifically deuterated cyclohexene, 1,2-dideuteriocyclohexene, is demonstrated.Peer reviewed: YesNRC publication: Ye