A fundamental understanding of the nanoscale details of the environment is essential for designing biomaterials that mimic the natural cellular milieu. Many features of the local environment have profound influences on cell adhesion, proliferation, maturation, and differentiation. As such, small differences in nanostructure can have macroscale impacts on tissue function. In this review, we highlight the importance of nanostructure of cellulose-based biomaterials to allow cellular adhesion, the contribution of nanostructure to macroscale mechanical properties, and several key applications of these materials for fundamental scientific research and biomedical engineering. Cellulose is a diverse material with tunable properties and can be applied to systems with vastly different biochemical and biophysical environments. Cellulose-based biomaterials offer some important advantages over conventional synthetic materials and show great promise to advance the frontier of scientific knowledge. Here we provide an up-to-date summary of the status of the field of cellulose-based biomaterials in the context of bottom-up approaches for tissue engineering. We anticipate that cellulose-based material research will continue to expand because of the diversity and versatility of biochemical and biophysical characteristics highlighted in this review.

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Cellulose Biomaterials for Tissue Engineering.

A critically important process in catalysis is the formation of an active catalyst from the combination of a metal precursor and a ligand, as the efficacy of this reaction governs the amount of active catalyst. This Review is a comprehensive overview of reactions catalyzed by nickel and an added bidentate phosphine, focusing on the steps transforming the combination of precatalyst and ligand into an active catalyst and the potential effects of this transformation on nickel catalysis. Reactions covered include common cross-coupling reactions, such as Suzuki, Heck, Kumada, and Negishi couplings, addition reactions, cycloadditions, C-H functionalizations, polymerizations, hydrogenations, and reductive couplings, among others. Overall, the most widely used nickel precatalyst with free bidentate phosphines is Ni(cod)2, which accounts for ∼50% of the reports surveyed, distantly followed by Ni(acac)2 and Ni(OAc)2, which account for ∼10% each. By compiling the reports of these reactions, we have calculated statistics of the usage and efficacy of each ligand with Ni(cod)2 and other nickel sources. The most common bidentate phosphines are simple, relatively inexpensive ligands, such as DPPE, DCPE, DPPP, and DPPB, along with others with more complex backbones, such as DPPF and Xantphos. The use of expensive chiral phosphines is more scattered, but the most common ligands include BINAP, Me-Duphos, Josiphos, and related analogs.

Trends in the Usage of Bidentate Phosphines as Ligands in Nickel Catalysis.

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed.

Chitosan Derivatives: Introducing New Functionalities with a Controlled Molecular Architecture for Innovative Materials

The use of chitosan-based metal catalysts in organic transformations

The deacetylated derivative of chitin i.e. chitosan is an advantageous and interesting bioactive polymer. Despite its biodegradability, it consists of many reactive primary and secondary hydroxyl (...

Functionalization of chitosan polymer and their applications

The review provides the first generalized and systematized information on the use of click reactions in chitosan chemistry for the preparation of novel polymers with attractive physicochemical and biological properties The reactions of copper-catalyzed azide—alkyne cycloaddition and the click reactions of chitosan derivatives occurring in the absence of salts or metal complexes are discussed in detail The data on the pre-click modification of chito-san (ie, the introduction of azide function, alkyne fragment, highly dipolarophilic moieties, and thiol group into the polymer) are reviewed Special attention is given to the application of new chitosan derivatives obtained by click modification

Click reactions in chitosan chemistry

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan–hyaluronic acid, chitosan–alginic acid, and chitosan–carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

Preparation and analysis of multilayer composites based on polyelectrolyte complexes

This review presents the main advances in the design of antitumor platinum complexes over the last five years. Particular attention is paid to unconventional antitumor platinum compounds (complexes in the trans configuration, Pt(IV) complexes with S and P donor ligands, multinuclear complexes).

Design and Antitumor Activity of Platinum Complexes

N-(2-Azidoethyl)chitosan was synthesized from low-molecular-weight chitosan (molecular weight 37 000 and degree of deacetylation 0.74) in three steps: (1) reaction of chitosan with chloroacetaldehyde to form a Schiffbase, (2) reduction of the Schiffbase with sodium borohydride, and (3) treatment of the reduction product with sodium azide. The course of the formation of the Schiffbase (this step is determining for the degree of substitution of the final product) was affected by the molar ratio of the reagents, the reaction time, and, primarily, the pH value of the medium. This method for selective to an amino group, does not require harsh conditions, and can be proposed for the azide pre-click modification of chitosan.

Azide pre-click modification of chitosan: N-(2-azidoethyl)chitosan

N-Succinylchitosan (SC) with degree of substitution 0.86 was prepared by reacting chitosan with succinic anhydride. The otoprotective potential of a single i.v. injection of a solution (0.3%) of the sodium salt of SC in 60 rats (males, Wistar, 220 – 250 g) was studied. A solution of meglumine sodium succinate (MSS) at an equivalent concentration was used as a reference. The drugs were administered 2 h or 5 min prior to induction of acute injury of the auditory analyzer by acoustic stimulation (AS). The condition of hearing was estimated by studying optoacoustic emission (OAE) at the frequency of distortion product 1 h, 24 h, and 7 d after the AS. SC showed a more pronounced protective effect with early preventive administration (p < 0.02; ANOVA with Bonferroni correction). Conversely, MSS exhibited its protective properties only with immediate administration. A comparison of the two drug administration modes showed that the OAE amplitude was depressed more after MSS administration than after SC injection (p < 0.05; Tukey’s test). It was concluded that conjugation to chitosan prolonged the elimination half-life of succinate and improved its access to cochlear back-barrier tissues.

Yu. A. Skorik

Papers

Click reactions in chitosan chemistry

Preparation and analysis of multilayer composites based on polyelectrolyte complexes

Design and Antitumor Activity of Platinum Complexes

Azide pre-click modification of chitosan: N-(2-azidoethyl)chitosan

Conjugation of Succinate to Chitosan Increases the Cochlear Cytoprotective Effect