Collagen fiber with surface-grafted polyphenol as a novel support for Pd(0) nanoparticles: Synthesis, characterization and catalytic application

Collagen processing with mesoscale aggregates as templates and building blocks

Collagen presents a well-organized hierarchical multilevel structure. Microfibers, fibers, and fiber bundles are the aggregates of natural collagen; which achieve an ideal balance of mechanical strength and toughness at the mesoscopic scale for biological tissue. These mesostructured aggregates of collagen isolated from biological tissues retain these inherent organizational features to enable their use as building blocks for constructing new collagen materials with ideal mechanical performance, thermal and dimensional stability. This strategy is distinct from the more common bottom-up or molecular-level design and assembly approach to generating collagen materials. The present review introduces the hierarchical structure of biological collagen with a focus on mesostructural features. Isolation strategies for these collagen aggregates (CAs) are summarized. Recent progress in the use of these mesostructural components for the construction of new collagen materials with emerging applications is reviewed, including in catalysis, environmental applications, biomedicine, food packaging, electrical energy storage, and flexible sensors. Finally, challenges and prospects are assessed for controllable production of CAs as well as material designs.

Collagen and Silk Fibroin as Promising Candidates for Constructing Catalysts

A catalyst determines the mechanism of an organic chemical reaction, thus enabling the commercially viable formation of desired material products. Biopolymers offer new opportunities for the construction of catalysts by virtue of their biocompatibility, environmental benignity, and sustainability, as well as their low cost. Biopolymers are especially useful as carriers and precursors in catalysis application. The employment of biocompatible and biosustainable collagen and silk fibroin materials will revolutionize state-of-the-art electronic devices and systems that currently rely on conventional technologies. In this review, we first consider the ordered hierarchical structure, origin, and processing methods of collagen and silk fibroin. Then, the unique advantages and applicability of collagen and silk fibroin for constructing catalysts are summarized. Moreover, a summary of the state-of-the-art design, fabrication, and application of collagen- and silk fibroin-based catalysts, as well as the application of collagen- and silk-based catalysts, is presented by focusing on their roles as carriers and precursors, respectively. Finally, challenges and prospects are assessed for the construction and development of collagen and silk fibroin-based catalysts.

Hierarchical collagen fibers complexed with tannic acid and Fe3+ as a heterogeneous catalyst for enhancing sulfate radical-based advanced oxidation process

Efficient sulfate radical-based advanced oxidation processes (SR-AOPs) are important for treating organic contaminants of industrial wastewater. To achieve this goal, tannic acid (TA)-modified skin collagen fibers (CFs) were prepared for the enhanced immobilization of Fe³⁺ based on multiple complexation interactions, resulting in a heterogeneous catalyst with more catalytic sites (defined as TA-Fe-CFs) for activating peroxymonosulfate (PMS). During the removal of an organic dye (rhodamine B, RhB) from water, the hierarchical TA-Fe-CFs exhibited excellent adsorption capacity at the early stage before the introduction of PMS, which can be ascribed to the π-π interaction between TA and aromatic RhB. Such improved mass transfer of target contaminants into the catalytic support was proved to be beneficial for improving the utilization efficiency of sulfate radicals in subsequent SR-AOPs. After introducing PMS, the reductive TA moieties of the heterogeneous catalyst were able to accelerate the redox cycle of Fe³⁺/Fe²⁺ in Fenton reactions, facilitating the activation of PMS to generate sulfate radicals for the degradation of organic RhB.

Recent advances in skin collagen: functionality and non-medical applications

Abstract

During nature evolution process, living organisms have gradually adapted to the environment and been adept in synthesizing high performance structural materials at mild conditions by using fairly simple building elements. The skin, as the largest organ of animals, is such a representative example. Conferred by its intricate organization where collagen fibers are arranged in a randomly interwoven network, skin collagen (SC), defined as a biomass derived from skin by removing non-collagen components displays remarkable performance with combinations of mechanical properties, chemical-reactivity and biocompatibility, which far surpasses those of synthetic materials. At present, the application of SC in medical field has been largely studied, and there have been many reviews summarizing these efforts. However, the generalized view on the aspects of SC as smart materials in non-medical fields is still lacking, although SC has shown great potential in terms of its intrinsic properties and functionality. Hence, this review will provide a comprehensive summary that integrated the recent advances in SC, including its preparation method, structure, reactivity, and functionality, as well as applications, particularly in the promising area of smart materials.

Graphical abstract

Palladium nanoparticles dispersed on functionalized macadamia nutshell biomass for formic acid-mediated removal of chromium(VI) from aqueous solution

Driven by the need for sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)). Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction analysis confirmed the formation of Pd on the modified MNS surface and suggested an estimated crystallite size of 5.0 nm. The supported nanoparticles exhibited catalytic activity in formic acid-mediated Cr(VI) reduction and showed promising stability with consecutive reuse. These findings set the stage for advanced studies into performance optimization.

Repositioning Natural Antioxidants for Therapeutic Applications in Tissue Engineering

Although a large panel of natural antioxidants demonstrate a protective effect in preventing cellular oxidative stress, their low bioavailability limits therapeutic activity at the targeted injury site. The importance to deliver drug or cells into oxidative microenvironments can be realized with the development of biocompatible redox-modulating materials. The incorporation of antioxidant compounds within implanted biomaterials should be able to retain the antioxidant activity, while also allowing graft survival and tissue recovery. This review summarizes the recent literature reporting the combined role of natural antioxidants with biomaterials. Our review highlights how such functionalization is a promising strategy in tissue engineering to improve the engraftment and promote tissue healing or regeneration.

Recent advances in phenolic-protein conjugates: synthesis, characterization, biological activities and potential applications

Proteins and phenolic compounds are two types of food ingredients with distinct functionalities. In the past decade, many attempts have been made to conjugate phenolic compounds with proteins through covalent linkages. Four types of conjugation reactions including alkaline, free radical mediated grafting, enzyme catalyzed grafting and chemical coupling methods are frequently used to synthesize phenolic-protein conjugates. The synthesized phenolic-protein conjugates can be well characterized by several different instrumental methods, such as UV spectroscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy, circular dichroism, mass spectroscopy, sodium dodecyl sulfate polyacrylamide gel electrophoresis and differential scanning calorimetry. Importantly, phenolic-protein conjugates exhibit improved biological properties (e.g. antioxidant, anticancer and antimicrobial activities) as compared with native proteins. Moreover, the applications of native proteins can be greatly widened by conjugation with phenolic compounds. Phenolic-protein conjugates have been developed as antioxidant emulsions for nutraceutical delivery, edible films for food packaging, stabilizers for metal nanoparticles, and hydrogels and nanoparticles for controlled drug release. In this review, recent advances in the synthesis, characterization, biological properties and potential applications of phenolic-protein conjugates were summarized.

Supramolecular design and applications of polyphenol-based architecture: A review

Polyphenol-based materials are of wide-spread interest because of the unique properties of the polyphenol itself. Tannic acid, contains high level of galloyl groups, could be coordinated to a range of metal ions to generate robust mental ion-TA films on substrate or even forming hollow capsules. These films or capsules can be used in the field of sensing, separation and catalysis, most importantly in drug/nutraceutical delivery, allowing for the high loading efficiency, high mechanical and thermal stability, pH-responsive disassembly and fluorescence behavior. Additionally, such coating could also provide protection of the sensitive molecules and cells. With the numerous carbonyl and phenolic functional groups, TA has also been demonstrated to form strong hydrogen bonded multilayers with various non-ionic polymers. The properties of the hydrogen-bonded system were highly influenced by the chemical structure of the polymers, which will change the behavior of pH-, temperature- or ionic strength-responsive release of the loading molecules. Additionally, the ionization of galloyl phenol group was attributed to the interaction between TA and other ionic polymers by electrostatic interaction. The electrostatic interaction/hydrogen bonding derived TA/polyme$$%r complexes could deposit on glass slides, microcores or even forming hollow capsules, promising in their applicability to nutraceutical encapsulation, delivery and depot. Notably, polyphenols self-polymerizing could also deposit coatings on different substrates without any exogenous additives, while the comprehensive undertanding about the self-polymerizing mechenism remains unclear. This review provides a promising prospect for utilizing polyphenol-based materials to design versatile architecture in different system, used in the field of chemistry and materials science.

Grafting of Gallic Acid onto a Bioactive Ti6Al4V Alloy: A Physico-Chemical Characterization

Despite increasing interest in the use of natural biomolecules for different applications, few attempts of coupling them to inorganic biomaterials are reported in literature. Functionalization of metal implants with natural biomolecules could allow a local action, overcoming the issue of low bioavailability through systemic administration. In the present work, gallic acid was grafted to a pre-treated Ti6Al4V in order to improve its biological response in bone contact applications. The grafting procedure was optimized by choosing the concentration of gallic acid (1 mg/mL) and the solvent of the solution, which was used as a source for functionalization, in order to maximize the amount of the grafted molecule on the titanium substrate. The functionalized surfaces were characterized. The results showed that functionalization with Simulated Body Fluid (SBF) as solvent medium was the most effective in terms of the amount and activity of the grafted biomolecule. A key role of calcium ions in the grafting mechanism is suggested, involving the formation of coordination compounds formed by way of gallic acid carboxylate and Ti–O− as oxygenated donor groups. Bioactive behavior and surface charge of the pre-treated Ti6Al4V surface were conserved after functionalization. The functionalized surface exposed a greater amount of OH groups and showed higher wettability.

Green synthesis of palladium nanoparticles via branched polymers: a bio-based nanocomposite for C–C coupling reactions

Renewable and sustainable CMH was the natural ligand for CMH–Pd(0) nanocomposite which was as an efficient and recyclable catalyst for Heck reaction.

Bio-inspired synthesis of metal nanomaterials and applications

This critical review focuses on recent advances in the bio-inspired synthesis of metal nanomaterials (MNMs) using microorganisms, viruses, plants, proteins and DNA molecules as well as their applications in various fields. Prospects in the design of bio-inspired MNMs for novel applications are also discussed.

Experimental and theoretical studies on Gallic acid assisted EDC/NHS initiated crosslinked collagen scaffolds

The effect of Gallic acid (GA) in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)/N-hydroxysuccinimide (NHS) on collagen scaffold is investigated. The thermal mechanical analyzer (TMA), differential scanning calorimetric (DSC), and thermogravimetric analysis (TGA) including tensile strength (TS, 180 ± 3 MPa), denaturation temperature (Td, 80.03°C), % elongation (% E, 180 ± 9) and weight loss (31.76%), indicate that the modification improves the structural integrity and stability of the collagen scaffold. The GA-EDC/NHS treatment inhibits the action of collagenase against collagen degradation compared to GA and EDC/NHS. It is concluded from docking studies that GA binds with collagen like peptide (CLP) and collagenase through multiple H-bonds and hydrophobic interactions leading to low binding energy -5.1 and -5.3 Kcal/mol, respectively. The hydrophobic core of the GA molecules, probably incorporates itself into the hydrophobic areas of the collagen groups, whereas OH and COOH moieties of GA establish multiple H-bonds with neighboring collagen molecules and carboxamide bond, thereby improving the swelling and water uptake properties, biocompatibility and cell adhesion properties. This results in improving stability of the scaffold, which prevents the free access of the collagenase to reactive sites in the triple helical collagen chains.

Constructing carbon-coated Fe₃O₄ microspheres as antiacid and magnetic support for palladium nanoparticles for catalytic applications

Fe₃O₄ microsphere is a good candidate as support for catalyst because of its unique magnetic property and large surface area. Coating Fe₃O₄ microspheres with other materials can protect them from being dissolved in acid solution or add functional groups on their surface to adsorb catalyst. In this paper, a carbon layer was coated onto Fe₃O₄ microspheres by hydrothermal treatment using polyethylene glycol as the connecting agents between glucose and Fe₃O₄ spheres. Through tuning the added amounts of reactants, the thickness of the carbon layer could be well-controlled. Because of the abundant reductive groups on the surface of carbon layer, noble metal ions could be easily adsorbed and in situ reduced to nanoparticles (6-12 nm). The prepared catalyst not only had unique antiacid and magnetic properties, but also exhibited a higher catalytic activity toward the reduction of methyl orange than commercially used Pd/C catalyst.