Biopolymer-polyphenol conjugates: Novel multifunctional materials for active packaging

The development of natural active packaging materials and coatings presents a promising alternative to petroleum-based packaging solutions. These materials are engineered by incorporating functional ingredients with preservative capabilities. Concurrently, research has highlighted the diverse physicochemical, functional, and health-promoting properties of protein-polyphenol, polysaccharide-polyphenol, and protein-polysaccharide-polyphenol conjugates within various food formulations. However, a critical gap exists regarding the exploration of these biopolymers as active packaging materials. In contrast to conventional approaches for developing active packaging materials, this review presents a novel perspective by focusing on biopolymer-polyphenol conjugates. In this work, we delve into the realm of active packaging materials and coatings constructed from these conjugates, highlighting their potential as multifunctional active components in food packaging and preservation. This review comprehensively investigates the physicochemical properties, functionalities, and health-promoting activities associated with biopolymer-polyphenol conjugates. Their emulsification, antioxidant, and antimicrobial activities, coupled with enhancements in mechanical strength and permeability properties, contribute to their multifunctional nature. Furthermore, we explore the potential advantages and limitations of utilizing these conjugates in active packaging applications. Finally, the review concludes by proposing crucial research avenues for further exploration of biopolymer-polyphenol conjugates within the domain of active food packaging.

Preparation, characterization and application of antioxidant packaging films based on chitosan-epicatechin gallate conjugates with different substitution degrees

In this study, chitosan (CS) was conjugated with epicatechin gallate (ECG) to prepare CS-ECG conjugates with different substitution degrees (5.18 %, 6.36 % and 7.74 %). Then, antioxidant packaging films were fabricated by blending CS and CS-ECG conjugates. The impact of CS-ECG conjugates' substitution degree on the functionality of CS/CS-ECG films was determined. CS-ECG conjugates showed UV absorption at 275 nm, proton signal at 6.85 ppm and infrared absorption at 1533 cm-1, assigning to the conjugated ECG. As compared with CS, CS-ECG conjugates exhibited less crystalline state but higher antioxidant activity. The structural characterization of CS/CS-ECG films showed CS and CS-ECG conjugates formed hydrogen bonds. CS/CS-ECG films displayed 26.35 %-29.23 % water solubility, 85.61°-86.96° water contact angle, 3.11-3.41 × 10-11 g m-1 s-1 Pa-1 water vapor permeability, 0.29-0.34 cm3 mm m-2 day-1 atm-1 oxygen permeability, 31.54-36.20 MPa tensile strength, 50.12 %-56.40 % elongation at break, as well as potent antioxidant activity and oil oxidation inhibitory ability. Notably, the film containing CS-ECG conjugate with 7.74 % substitution degree had the strongest barrier ability, mechanical property, antioxidant activity and oil oxidation inhibitory ability. Results suggested the substitution degree of CS-ECG conjugates was positively correlated with the barrier, mechanical and antioxidant properties of CS/CS-ECG films.

Tea polyphenol carrier-enhanced dexamethasone nanomedicines for inflammation-targeted treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease characterized by synovial inflammation, cartilage damage and bone erosion. In the progression of RA, the inflammatory mediators including ROS, NO, TNF-α, and IL-6 play important roles in the aggravation of inflammation. Hence, reducing the generation and release of inflammatory mediators is of great importance. However, the high dose and frequent administration of clinical anti-inflammatory drugs such as glucocorticoids (GCs) usually lead to severe side effects. The development of nanotechnology provides a promising strategy to overcome these issues. Here, polyphenol-based nanoparticles with inherent anti-oxidative and anti-inflammatory activities were developed and used as a kind of nanocarrier to deliver dexamethasone (Dex). The in vitro experiments confirmed that the nanoparticles and drugs could act synergistically for suppressing inflammatory mediators in the LPS/INF-γ-induced inflammatory cell model. After intravenous administration, the Dex-loaded nanoparticles with good biosafety showed effective accumulation in inflamed joints and improved therapeutic efficacy by inducing anesis of synovial inflammation and cartilage destruction over free Dex in a collagen-induced arthritis (CIA) mouse model. The results demonstrated that polyphenol-based nanoparticles with therapeutic functions may serve as an innovative platform to synergize with chemotherapeutic agents for enhanced treatment of inflammatory diseases.

Dextran-Based Injectable Hydrogel Composites for Bone Regeneration

Currently, bone infections caused by diseases or injuries are a major health issue. In addition, the conventional therapeutic approaches used to treat bone diseases or injuries present several drawbacks. In the area of tissue engineering, researchers have been developing new alternative therapeutic approaches, such as scaffolds, to promote the regeneration of injured tissues. Despite the advantages of these materials, most of them require an invasive surgical procedure. To overcome these problems, the main focus of this work was to develop scaffolds for bone regeneration, which can be applied using injectable hydrogels that circumvent the use of invasive procedures, while allowing for bone regeneration. Throughout this work, injectable hydrogels were developed based on a natural polymer, dextran, along with the use of two inorganic compounds, calcium β-triphosphate and nanohydroxyapatite, that aimed to reinforce the mechanical properties of the 3D mesh. The materials were chemically characterized considering the requirements for the intended application: the swelling capacity was evaluated, the degradation rate in a simulated physiological environment was assessed, and compression tests were performed. Furthermore, vancomycin was incorporated into the polymeric matrices to obtain scaffolds with antibacterial performance, and their drug release profile was assessed. The cytotoxic profile of the hydrogels was assessed by an MTS assay, using osteoblasts as model cells. The data obtained demonstrated that dextran-based hydrogels were successfully synthesized, with a drug release profile with an initial burst between 50 and 80% of the drug. The hydrogels possess fair biocompatibility. The swelling capacity showed that the stability of the samples and their degradation profile is compatible with the average time period required for bone regeneration (usually about one month) and have a favorable Young's modulus (200-300 kPa). The obtained hydrogels are well-suited for bone regeneration applications such as infections that occur during implantation or bone graft substitutes with antibiotics.

Rationally designed multifunctional nanoparticles as GSH-responsive anticancer drug delivery systems based on host-guest polymers derived from dextran and β-cyclodextrin

Tumor proliferation and metastasis rely on energy provided by mitochondria. The hexokinase inhibitor lonidamine (LND) could suppress the activities in mitochondria, being a potential antitumor drug. However, limited water-solubility of LND may hinder its biomedical applications. Besides, the cancer-killing effect of LND is compromised by the high level of glutathione (GSH) in cancer cells. Therefore, it is urgent to find a proper method to simultaneously deliver LND and deplete GSH as well as monitor GSH level in cancer cells. Herein, a host polymer β-cyclodextrin-polyethylenimine (β-CD-PEI) and a guest polymer dextran-5-dithio-(2-nitrobenzoic acid) (Dextran-SS-TNB) were synthesized and allowed to form LND-loaded GSH-responsive nanoparticles through host-guest inclusion complexation between β-CD and TNB as host and guest molecular moieties, respectively, which functioned as a system for simultaneous delivery of LND and -SS-TNB species into cancer cells. As a result, the delivery system could deplete GSH and elevate reactive oxygen species (ROS) level in cancer cells, further induce LND-based mitochondrial dysfunction and ROS-based immunogenic cell death (ICD), leading to a synergistic and efficient anticancer effect. In addition, -SS-TNB reacted with GSH to release TNB2-, which could be a probe with visible light absorption at 410 nm for monitoring the GSH level in the cells.

Biocompatible, bacteria-targeting resveratrol nanoparticles fabricated by Mannich molecular condensation for accelerating infected wound healing

Excessive reactive oxygen species (ROS) and long-term inflammation can delay wound healing and cause tissue damage, while bacterial infection aggravates the wound environment further. It is impossible to resolve all these thorny problems simultaneously with a wound dressing that has only one function. The antioxidative and anti-inflammatory properties of resveratrol (Res) have been proven. However, the effect of Res is non-selective, and high levels of Res can inhibit cell growth and promote oxidation. Res is also difficult to dissolve and possesses insufficient antibacterial properties, so its role is limited. In this study, Res was assembled via Mannich reaction into nanoparticles and functionalized by phenylboric acid, giving rise to targeting bacteria and solving the water-insoluble dilemma of Res. In comparison with Trolox, the assembled Res NPs performed better at scavenging ABTS and DPPH free radicals. Furthermore, Res NPs that targeted bacteria also showed high biocompatibility at concentrations five times higher than pure Res. The activities of Res NPs were comparable to free Res in downregulating the expression of inflammatory cytokines, and reducing intracellular excessive ROS. The gel embedded with Res NPs accelerated the formation of granulation tissue, collagen deposition, and re-epithelialization, facilitating wound healing. The present study suggests that functionalized polyphenol-based materials are preferably suited to the development of tissue engineering biomaterials.

Structure, stability and antioxidant activity of dialdehyde starch grafted with epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate

BACKGROUND

Catechins, a member of the flavonoids, exist widely in teas, and have health benefits. However, catechins have poor stability, which greatly limits their application. In order to improve the stability of catechins, different catechins including (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) were conjugated onto dialdehyde starch by acid-mediated coupling method. The structure, stability and antioxidant activity of dialdehyde starch-catechin conjugates were determined.

RESULTS

Thin-layer chromatography and ultraviolet-visible spectroscopy, fluorescence, nuclear magnetic resonance and infrared spectra revealed that catechins were successfully conjugated onto dialdehyde starch, coupling between 6-H/8-H of catechins' A ring and dialdehyde starch's aldehyde groups. The conjugates presented an amorphous structure and sheet-like and/or blocky morphologies. As compared to dialdehyde starch, the conjugates showed enhanced thermal stability. Furthermore, the stability of catechins in pH 7.4 phosphate-buffered saline was improved after conjugating onto dialdehyde starch. The conjugates exhibited significantly higher antioxidant activities than dialdehyde starch, decreasing in the following order: dialdehyde starch-ECG, dialdehyde starch-EGCG, dialdehyde starch-EC, dialdehyde starch-EGC and dialdehyde starch.

CONCLUSION

Dialdehyde starch-catechin conjugates have great potential as stable antioxidant agents. © 2022 Society of Chemical Industry.

Biocompatible, Antioxidant Nanoparticles Prepared from Natural Renewable Tea Polyphenols and Human Hair Keratins for Cell Protection and Anti-inflammation

Excessive reactive oxygen species (ROS) can cause oxidative stress of tissues and adversely influence homeostasis of the body. Epigallocatechin gallate (EGCG) with an antioxidative effect can effectively eliminate the ROS, but an evident weakness associated with it is the relatively poor cytocompatibility. Combining with other biomacromolecules such as human hair keratin (KE) and using nanotechnology to prepare nanoparticles can improve this situation. By covalent bonding, we assembled KE and EGCG into KE-EGCG nanoparticles (NANO) with size of about 50 nm and characterized them by DLS, UV, FTIR, NMR, and XPS. Free radical scavenging experiments show that antioxidant properties of the obtained NANO are superior to that of vitamin C. Cell culture experiments also show that the NANO can effectively protect the proliferation of L929 cells and HUVEC cells. In addition, we also used RAW264.7 cells to establish a H₂O₂-induced cell injury model and an lipopolysaccharide-induced cellular inflammatory model to evaluate the antioxidant and anti-inflammatory properties of NANO. The results show that the NANO can effectively prevent cells from oxidative damage and reduce inflammatory expression of the cells, indicating that the NANO have a good antioxidative and anti-inflammatory effect on cells which can be applied to many diseases related to oxidative stress.

Highly efficient synthesis and characterization of starch aldehyde-catechin conjugate with potent antioxidant activity

In this study, cassava starch aldehyde was functionalized with catechin through acid catalyzed condensation reaction. The structural characterization, stability and antioxidant activity of starch aldehyde-catechin conjugates were investigated. Thin layer chromatography revealed the conjugates did not contain free catechin. UV-vis spectra of the conjugates exhibited an absorption band at 280 nm, attributing to the B-ring of catechin moiety. Fourier-transform infrared and proton nuclear magnetic resonance spectroscopy demonstrated the conjugation occurred between the H-6/H-8 of catechin A-ring and the aldehyde groups of starch aldehyde. X-ray diffraction pattern indicated that the conjugates had an amorphous structure. Scanning electron microscopy showed the conjugates were fragmentary slices with rough surfaces. Notably, the conjugates were more stable than catechin in phosphate buffered saline (pH 7.4). In addition, the conjugates could not be digested in simulated saliva, gastric and small intestinal juices. The reducing power and free radical scavenging activity of starch aldehyde were remarkably elevated by conjugating with catechin. Meanwhile, the conjugates were non-cytotoxic to RAW264.7 mouse macrophage cells and possessed higher resistant starch contents than starch. Our results suggest starch aldehyde-catechin conjugates can be used as antioxidants in food industry.

Effect of hydrophilic groups on the bioactivity of antimicrobial polymers

Antimicrobial polymers have recently been investigated as potential treatments to combat multidrug-resistant pathogens.

Engineering Supramolecular Polymer Conformation for Efficient Carbon Nanotube Sorting

Supramolecular polymer sorting is a promising approach to separating single-walled carbon nanotubes (CNTs) by electronic type. Unlike conjugated polymers, they can be easily removed from the CNTs after sorting by breaking the supramolecular bonds, allowing for isolation of electronically pristine CNTs as well as facile recycling of the sorting polymer. However, little is understood about how supramolecular polymer properties affect CNT sorting. Herein, chain stoppers are used to engineer the conformation of a supramolecular sorting polymer, thereby elucidating the relationship between sorting efficacy and polymer conformation. Through NMR and UV-vis spectroscopy, small-angle X-ray scattering (SAXS), and thermodynamic modeling, it is shown that this supramolecular polymer exhibits ring-chain equilibrium, and that this equilibrium can be skewed toward chains by the addition of chain stoppers. Furthermore, by controlling the stopper-monomer ratio, the sorting yield can be doubled from 7% to 14% without compromising the semiconducting purity (>99%) or properties of sorted CNTs.

Evaluation and Exploitation of Bioactive Compounds of Walnut, Juglans regia

In the last few years, great importance has been given to natural materials (such as walnuts, peanuts, chestnuts) due to their medicinal and pharmaceutical uses induced by the presence of natural agents, including polyphenols. Juglans regia is a traditional plant that has been used since ancient times in traditional medicine for the treatment of various diseases like microbial infections, stomach ache, thyroid dysfunctions, cancer, heart diseases and sinusitis. Recently, scientific attention for the phytochemical profile of walnut by-products is increasing due to their valuable active constituents. Natural polyphenols are important compounds present in walnut with valuable properties that have been studied for the treatment of inflammation, cancer or anti-ageing effect. The use of nanocarriers as a drug delivery system is now a promising strategy to get more stable products and is easier to apply in a medical, therapeutic and pharmaceutical environment. The aim of this work was to review the latest information provided by scientific investigators regarding the nutritional value, bioactive compounds, antioxidant and antitumor activity of walnut by-product extracts. Moreover, this review provides comprehensive information on the nanoencapsulation of bioactive constituents for application in clinical medicine, particularly in cancer research.

Gallic Acid-Dextran Conjugate: Green Synthesis of a Novel Antioxidant Molecule

A novel derivative of dextran, dextran–gallic acid (Dex–Gal), obtained from simple conjugation with gallic acid, was synthesized by an efficient free radical-mediated method. To verify the synthesis of Dex–Gal, 1H-nuclear magnetic resonance (1H-NMR), Fourier transform infrared (FTIR) spectrometry, and high-performance size-exclusion chromatography (HPSEC) were employed. The results revealed the conjugation of gallic acid with the 15.5 kDa dextran from Leuconostoc mesenteroides. Dex–Gal had a molecular weight of 11.2 kDa, indicating that the conjugation reaction was accompanied by a minor degradation of Dex–Gal. In addition, Dex–Gal contained 36.8 ± 1.4 mg gallic acid per gram dextran. These molecules were also evaluated as antioxidants using total antioxidant capacity (TAC), reducing power, ferric chelation, and superoxide radical-scavenging assays. Both polysaccharides had no ferric chelation activity. In addition, Dex–Gal was more efficient as an antioxidant agent in TAC (13 times) and was more efficient than dextran in superoxide radical-scavenging (60 times) and reducing power (90 times) assays. These data demonstrate that Dex–Gal is a natural-compound-based antioxidant with potential applications in the pharmaceutical, cosmetic, and food industries.

Facet- and structure-dependent catalytic activity of cuprous oxide/polypyrrole particles towards the efficient reduction of carbon dioxide to methanol

The preparation of cost-effective, stable catalysts for the selective reduction of carbon dioxide (CO2) to C1 products such as methanol is extremely important because methanol can be used directly as a fuel or it can be converted into other value-added products. However, the catalysts currently used for the reduction of CO2 to methanol exhibit poor selectivity, poor stability and very low faradaic efficiency. Herein, we used low-cost, stable cuprous oxide/polypyrrole (Cu2O/Ppy) particles having structures of octahedra and icosahedra (microflowers) that were prepared on linen texture (LT) papers for the selective reduction of CO2 to form a value-added single C1 product, methanol. The Cu2O/Ppy particles possessing both octahedral and microflower shapes with exposed low-index (111) facets and high-index (311) and (211) facets are denoted as Cu2O(OL-MH)/Ppy particles. The as-prepared Cu2O(OL-MH)/Ppy particles exhibited high catalytic activity and selectivity towards the electrochemical reduction of CO2 at -0.85 V vs. RHE to form methanol, with a faradaic efficiency of 93 ± 1.2% and an average methanol formation rate of 1.61 ± 0.02 μmol m-2 s-1. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the pyrrolic nitrogen atoms present in the Ppy shell played a dominant role as active sites for CO2 molecules. The Raman bands of Ppy and Cu2O did not shift even after being subjected to electrolysis for several hours, suggesting superior stability of the Cu2O(OL-MH)/Ppy particles. The high resolution microscopic, spectroscopic, diffraction and electrochemical analysis results clearly revealed that the Ppy shell protected the Cu2O particles and avoided corrosion, dissolution, and structural and crystal facet changes, leading to greater stability. The low-cost, durable, flexible, and catalytically active Cu2O(OL-MH)/Ppy LT paper holds great potential for catalytic, photocatalytic and energy storage applications.

Cytosolic Uptake of Large Monofunctionalized Dextrans

Dextrans are a versatile class of polysaccharides with applications that span medicine, cell biology, food science, and consumer goods. Here, we report on a new type of large monofunctionalized dextran that exhibits unusual properties: efficient cytosolic and nuclear uptake. This dextran permeates various human cell types without the use of transfection agents, electroporation, or membrane perturbation. Cellular uptake occurs primarily through active transport via receptor-mediated processes. These monofunctionalized dextrans could serve as intracellular delivery platforms for drugs or other cargos.

Recent advances in flavonoid-grafted polysaccharides: Synthesis, structural characterization, bioactivities and potential applications

Plant derived flavonoids have been demonstrated to possess many valuable biological functions. In recent years, flavonoids have been successfully conjugated with polysaccharides through different graft copolymerization methods including chemical coupling, enzyme catalysis, free radical mediated grafting, and acid catalyzed condensation reactions. The successful grafting of flavonoids onto polysaccharides can be confirmed by several instrumental methods. The conjugation of flavonoids can significantly improve the antioxidant, antimicrobial, antitumor, hepatoprotective and enzyme inhibition properties of polysaccharides. Moreover, the applications of polysaccharides in food and pharmaceutical industries can be greatly broadened by grafting with flavonoids. Flavonoid-grafted polysaccharides can be developed as films for active packaging, hydrogels for controlled drug release, micelles for oral drug delivery, and emulsions for nutraceutical delivery. In general, the bioactivities and applications of conjugates are closely related to the type of flavonoid grafted, the grafting method used as well as the grafting efficiency. Recent advances in the synthesis, structural characterization, bioactivities and potential applications of flavonoid-grafted polysaccharides are summarized in this review.

High Throughput Preparation of UV-Protective Polymers from Essential Oil Extracts via the Biginelli Reaction

A high throughput (HTP) system has been developed to exploit new functional polymers. We synthesized 25 monomers in a mini-HTP manner through the tricomponent Biginelli reaction with high yields. The starting materials were five aldehydes extracted from essential oils. The 25 corresponding polymers were conveniently prepared via mini-HTP radical polymerization initially realizing the benefit of HTP methods to quickly fabricate sample libraries. The distinct radical scavenging ability of these Biginelli polymers was evaluated through a HTP measurement to choose the three best radical scavengers. This confirms the superiority of the HTP strategy to rapidly collect and analyze data. The selected polymers have been upgraded and screened according to different requirements for biomaterials and offer water-soluble and biocompatible copolymers that effectively protect cells from the fatal UV damage. This research is a straightforward way to establish new libraries of monomers with abundant diversity. It offers polymers with interesting functionalities. This suggests that a broader study of multicomponent reactions and HTP methods might be useful in many interdisciplinary fields. To the best of our knowledge, this is the first report of a HTP study of the Biginelli reaction to develop a promising polymeric biomaterial, which might have important implications for the organic chemistry and polymer communities.

Synthesis of chitin-glucan-aldehyde-quercetin conjugate and evaluation of anticancer and antioxidant activities

In the present study, we have synthesized chitin-glucan-aldehyde-quercetin (chi-glu-ald-que) conjugate via condensation reaction. Synthesis of chitin-glucan-aldehyde (chi-glu-ald) complex was facilitated by the oxidation of chitin-glucan (chi-glu) complex. Formation of conjugate was confirmed by Proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier-transform infrared spectroscopy (FT-IR). Morphological studies showed that after grafting of quercetin, several changes on surface were depicted and a more crystalline nature was observed. The chi-glu-ald-que conjugate displayed strong antioxidant activity. It showed 69% of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical, DPPH* scavenging activity at 1 mg/mL and 72% of 2, 2-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation, ABTS*⁺ scavenging activity at 1 mg/mL concentration, which are much higher than that of chi-glu complex. The anticancer activity of chi-glu-ald-que conjugate was performed in Macrophage cancer cell lines (J774) and biocompatibility was performed in Peripheral blood mononuclear cells (PBMCs). The chi-glu-ald-que conjugate showed excellent cytotoxicity against J774 cell lines but no cytotoxicity towards PBMCs.

Size-controlled, colloidally stable and functional nanoparticles based on the molecular assembly of green tea polyphenols and keratins for cancer therapy

Molecular assembly of green tea polyphenols and keratins into size-controlled, colloidally stable and functional nanoparticles for enhanced cancer therapy was achieved.

Enhancing the antimicrobial and antibiofilm effectiveness of silver nanoparticles prepared by green synthesis

Water soluble catechin oligomers produce small (8.5 nm) silver nanoparticles with high antimicrobial and antibiofilm efficacy.

Phenolic compounds based conjugates from dextran aldehyde and BSA: Preparation, characterization and evaluation of their anti-cancer efficacy for therapeutic applications

Here, we have synthesized phenolic compounds (pc) based on conjugates from dextran aldehyde (dex-ald) and bovine serum albumin (BSA) and screening their potential activity as therapeutic agents in cancer disease. The synthesized conjugates were analyzed by UV-vis, FT-IR, XRD and SEM analysis. UV-vis spectra of conjugates showed the shifting of spectral peak at UV to visible region revealed the enhanced conjugation due to formation of linkage. The XRD peaks of conjugates found broader and indicating the amorphous phase of conjugating materials in compared to free components. The SEM images showed that the conjugated materials having numerous pores on its surface, which proved its porous nature. The amount of phenolic compounds conjugated with (dex-ald-pc) and (BSA-pc) were found to be 65.4 and 73.91mg/g of conjugates, respectively. Cells viability was significantly decreased approximately 80-85% at concentration of 100μg conjugates whereas the free polymers or phenolics did not affect the viability of cancer cells. Generation of high quantity of reactive oxygen species (ROS) in cells treated with conjugate materials, which may caused cell apoptosis in cancer cell line. The results clearly showed that conjugation of phenolic compounds were an effective method to improve the functional properties for therapeutic applications.

Versatile oligomers and polymers from flavonoids – a new approach to synthesis

Antioxidant oligomers and polymers have been prepared from two flavonoids, catechin and quercetin, using a new facile technique.