Furfuryl‐ and Maleimido Polysaccharides: Synthetic Strategies Toward Functional Biomaterials

Promising superabsorbent hydrogel based on carboxymethyl cellulose and polyacrylic acid: synthesis, characterization, and applications in fertilizer engineering

The combination of hydrogel and fertilizer as slow release fertilizer hydrogel (SRFH) has become one of the most promising materials to overcome the shortcomings of conventional fertilizer by decreasing fertilizer loss rate, supplying nutrients sustainably, and lowering the frequency of irrigation. The hydrogel based on carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) (CMC/PAA) was synthesized. All materials, Vinasse, hydrogel (CMC/PAA) and (Vinasse/CMC-PAA) were characterized by FTIR, XRD, and SEM. The formed hydrogel was applied to control the salinity of Vinasse to use it as a cheap and economical fertilizer. The results showed that using the prepared hydrogel with Vinasse (V/CMC-PAA) as a slow-release organic fertilizer decreased the EC value through the first six hours from 1.77 to 0.35 mmohs/cm. Also, using V/CMC-PAA can control and keep the potassium as fertilizer for 50 days. The productivity per feddan from the sugar cane crop increased by about 15%, and the number of irrigations decreased from 5 to 4 times.

Efficient synthesis of fully renewable, furfural-derived building blocks via formal Diels-Alder cycloaddition of atypical addends

Diels-Alder (DA) cycloaddition of furanics is emerging as a key transformation in circular chemistry, providing access to highly versatile, biobased platform molecules. Further development of this technology into viable industrial applications faces major challenges, a notorious one being the lack of reactivity of the most readily available furans, i.e. the furfural derivatives. Herein we describe the remarkably-facile intramolecular DA reaction of allyl acetals of different furfurals to efficiently afford formal DA adducts with the atypical, unreactive dienophile allyl alcohol. Our methodology gives access to unprecedented oxanorbornene derivatives in high chemo-, regio- and stereoselectivity, which can be readily diversified into valuable products. This offers the potential of scalable production of renewable chemical building blocks from cheap, bioderived platform molecules.

Understanding the reactivity and selectivity of Diels-Alder reactions involving furans

The reactivity and endo/exo selectivity of the Diels-Alder cycloaddition reactions involving furan and substituted furans as dienes have been computationally explored. In comparison to cyclopentadiene, it is found that furan is comparatively less reactive and also less endo-selective in the reaction with maleic anhydride as the dienophile. Despite that, both the reactivity and the selectivity can be successfully modified by the presence of substituents at either 2- or 3-positions of the heterocycle. In this sense, it is found that the presence of strong electron-donor groups significantly increases the reactivity of the system while the opposite is found in the presence of electron-withdrawing groups. The observed trends in both the reactivity and selectivity are analyzed quantitatively in detail by means of the activation strain model of reactivity in combination with the energy decomposition analysis methods.

Dextran thioparaconate - Evaluation of the multifunctional thiolactone linker for easily adaptable polysaccharide modification

For the preparation of tailored polymers based on polysaccharides, an easy adaptable modification method was developed by introduction of a multifunctional linker into the polymer backbone. Dextran was functionalized with a thiolactone compound that can be further treated with amine resulting in ring opening and formation of a thiol. The functional thiol group emerging can be used for crosslinking or introduction of a further functional compound by disulfide formation. Here, the efficient esterification of thioparaconic acid after in-situ activation and studies about reactivity of the dextran thioparaconate obtained are discussed. The derivative was converted by aminolysis with model compound hexylamin and the thiol generated therefrom was subsequently converted with an activated functional thiol to the corresponding disulfide. The thiolactone, which protects the thiol, enables efficient esterification without side reactions and allows storage of the polysaccharide derivative at ambient conditions for years. Not only the multifunctional reactivity of the derivative but also the end product with a balanced ratio of hydrophobic and cationic moiety is appealing for biomedical application.

Recent advancements in design of nucleic acid nanocarriers for controlled drug delivery

Research of nanoscale nucleic acid carriers has garnered attention in recent years due to their distinctive and controllable properties. However, current knowledge is limited in how we can efficiently utilize these systems for clinical applications. Several researchers have pioneered new and innovative nanocarrier drug delivery systems, but understanding physiochemical properties and behavior in vivo is vital to implementing them as clinical drug delivery platforms. In this review, we outline the most significant innovations in the synthesis, physical properties, and utilization of nucleic acid nanocarriers in the past 5 years, addressing the crucial properties which improve nanocarrier characteristics, delivery, and drug release. The challenges of controlling the transport of nucleic acid nanocarriers and therapeutic release for biological applications are outlined. Barriers which inhibit effective transport into tissue are discussed with emphasis on the modifications needed to overcome such obstacles. The novel strategies discussed in this work summarize the pivotal features of modern nucleic nanocarriers and postulate where future developments could revolutionize the translation of these tools into a clinical setting.

The Interplay between Kinetics and Thermodynamics in Furan Diels-Alder Chemistry for Sustainable Chemicals Production

Biomass-derived furanic platform molecules have emerged as promising building blocks for renewable chemicals and functional materials. To this aim, the Diels-Alder (DA) cycloaddition stands out as a versatile strategy to convert these renewable resources in highly atom-efficient ways. Despite nearly a century worth of examples of furan DA chemistry, clear structure-reactivity-stability relationships are still to be established. Detailed understanding of the intricate interplay between kinetics and thermodynamics in these very particular [4+2] cycloadditions is essential to push further development and truly expand the scope beyond the ubiquitous addend combinations of electron-rich furans and electron-deficient olefins. Herein, we provide pertinent examples of DA chemistry, taken from various fields, to highlight trends, establish correlations and answer open questions in the field with the aim to support future efforts in the sustainable chemicals and materials production.

Diels–Alder Cycloadditions of Bio-Derived Furans with Maleimides as a Sustainable «Click» Approach towards Molecular, Macromolecular and Hybrid Systems

This mini-review highlights the recent research trends in designing organic or organic-inorganic hybrid molecular, biomolecular and macromolecular systems employing intermolecular Diels–Alder cycloadditions of biobased, furan-containing substrates and maleimide dienophiles. The furan/maleimide Diels–Alder reaction is a well-known process that may proceed with high efficiency under non-catalytic and solvent-free conditions. Due to the simplicity, 100% atom economy and biobased nature of many furanic substrates, this type of [4+2]-cycloaddition may be recognized as a sustainable “click” approach with high potential for application in many fields, such as fine organic synthesis, bioorganic chemistry, material sciences and smart polymers development.

Click-functionalized hydrogel design for mechanobiology investigations

The advancement of click-functionalized hydrogels in recent years has coincided with rapid growth in the fields of mechanobiology, tissue engineering, and regenerative medicine. Click chemistries represent a group of reactions that possess high reactivity and specificity, are cytocompatible, and generally proceed under physiologic conditions. Most notably, the high level of tunability afforded by these reactions enables the design of user-controlled and tissue-mimicking hydrogels in which the influence of important physical and biochemical cues on normal and aberrant cellular behaviors can be independently assessed. Several critical tissue properties, including stiffness, viscoelasticity, and biomolecule presentation, are known to regulate cell mechanobiology in the context of development, wound repair, and disease. However, many questions still remain about how the individual and combined effects of these instructive properties regulate the cellular and molecular mechanisms governing physiologic and pathologic processes. In this review, we discuss several click chemistries that have been adopted to design dynamic and instructive hydrogels for mechanobiology investigations. We also chart a path forward for how click hydrogels can help reveal important insights about complex tissue microenvironments.

Grafting Diels-Alder moieties on cellulose nanocrystals through carbamation

The Diels-Alder reaction is a promising click chemistry for the design of advanced materials from cellulose nanocrystals (CNCs). Transferring such chemistry to cellulose nanocrystals requires the precise grafting of reactive Diels-Alder moeities under heterogeneous conditions without compromising the nanocrystals morphology. In this study toluene diisocyanate is used as a spacer to graft Diels-Alder moieties viz the furyl and protected maleimido moieties onto cellulose nanocrystals. A factorial experimental design reveals that reaction time and reactant molar ratio positively affect the grafting efficiency, as evidenced by FTIR and CHNS elemental analysis. The surface degree of substitution was analyzed via CHNS elemental analysis and XPS and found to range between 0.05 to 0.30, with a good agreement between the two techniques. ¹³C CP/MAS NMR confirmed that the grafted moieties and CNCs are intact after reaction. Side reactions were also observed and their impact on performing controllable click chemistry between cellulose nanocrystals is discussed.

Solvent-Free Synthesis of Amidated Carboxymethyl Cellulose Derivatives: Effect on the Thermal Properties

The present work explores the possibility of chemically modifying carboxymethyl cellulose (CMC), a widely diffused commercial cellulose ether, by grafting of hydrophobic moieties. Amidation of CMC, at high temperature and in heterogeneous conditions, was selected as synthetic tool for grafting on CMC a panel of commercially available amines (bearing long aliphatic chains, alkyl aromatic and heteroaromatic groups, more or less spaced from the cellulose backbone). The reaction was successfully carried out in absence of solvents, catalysts and coupling agents, providing a promising and more sustainable alternative to conventional amidation procedures. Relationships between the chemical structure of the obtained CMC derivatives and their thermal properties were carefully studied, with a particular attention to the thermal behavior. Grafting of aromatic and heteroaromatic alkyl amines, presenting a linear alkyl chain between CMC backbone and a terminal bulky moiety, allowed for efficiently separating the polysaccharide chains, improving their mobility and resulting in a consequent lowering of the glass transition temperature (T_g). The T_g values obtained (90-147 °C) were found to be closely dependent on both the size of the aliphatic spacer, the structure of the aromatic ring and the extent of amidation.