Pro- and Anti-oxidant Properties of Redox-Active Catechol-Chitosan Films

Exploring the mechanism underlying the antifungal activity of chitosan-based ZnO, CuO, and SiO2 nanocomposites as nanopesticides against Fusarium solani and Alternaria solani

Chitosan-based nanocomposites (CS NCs) are gaining considerable attention as multifaceted antifungal agents. This study investigated the antifungal activity of NCs against two phytopathogenic strains: Fusarium solani (F. solani) and Alternaria solani (A. solani). Moreover, it sheds light on their underlying mechanisms of action. The NCs, CS-ZnO, CS-CuO, and CS-SiO2, were characterized using advanced methods. Dynamic and electrophoretic light scattering techniques revealed their size range (60-170 nm) and cationic nature, as indicated by the positive zeta potential values (from +16 to +22 mV). Transmission electron microscopy revealed the morphology of the NCs as agglomerates formed between the chitosan and oxide components. X-ray diffraction patterns confirmed crystalline structures with specific peaks indicating their constituents. Antifungal assessments using the agar diffusion technique demonstrated significant inhibitory effects of the NCs on both fungal strains (1.5 to 4-fold), surpassing the performance of the positive control, nystatin. Notably, the NCs exhibited superior antifungal potency, with CS-ZnO NCs being the most effective. A. solani was the most sensitive strain to the studied agents. Furthermore, the tested NCs induced oxidative stress in fungal cells, which elevated stress biomarker levels, such as superoxide dismutase (SOD) activity and protein carbonyl content (PCC), 2.5 and 6-fold for the most active CS-CuO in F. solani respectively. Additionally, they triggered membrane lipid peroxidation up to 3-fold higher compared to control, a process that potentially compromises membrane integrity. Laurdan fluorescence spectroscopy highlighted alterations in the molecular organization of fungal cell membranes induced by the NCs. CS-CuO NCs induced a membrane rigidifying effect, while CS-SiO2 and CS-ZnO could rigidify membranes in A. solani and fluidize them in F. solani. In summary, this study provides an in-depth understanding of the interactions of CS-based NCs with two fungal strains, showing their antifungal activity and offering insights into their mechanisms of action. These findings emphasize the potential of these NCs as effective and versatile antifungal agents.

Adhesive, Flexible, and Fast Degradable 3D-Printed Wound Dressings with a Simple Composition

3D printing technology has revolutionized the field of wound dressings, offering tailored solutions with mechanical support to facilitate wound closure. In addition to personalization, the intricate nature of the wound healing process requires wound dressing materials with diverse properties, such as moisturization, flexibility, adhesion, anti-oxidation and degradability. Unfortunately, current materials used in digital light processing (DLP) 3D printing have been inadequate in meeting these crucial criteria. This study introduces a novel DLP resin that is biocompatible and consists of only three commonly employed non-toxic compounds in biomaterials, that is, dopamine, poly(ethylene glycol) diacrylate, and N-vinylpyrrolidone. Simple as it is, this material system fulfills all essential functions for effective wound healing. Unlike most DLP resins that are non-degradable and rigid, this material exhibits tunable and rapid degradation kinetics, allowing for complete hydrolysis within a few hours. Furthermore, the high flexibility enables conformal application of complex dressings in challenging areas such as finger joints. Using a difficult-to-heal wound model, the manifold positive effects on wound healing in vivo, including granulation tissue formation, inflammation regulation, and vascularization are substantiated. The simplicity and versatility of this material make it a promising option for personalized wound care, holding significant potential for future translation.

Oxidative Stress in Xenograft Mouse Model Exposed to Dendrimers Decorated Polydopamine Nanoparticles and Targeted Chemo- and Photothermal Therapy

Polydopamine (PDA)-based nanostructures are used for biomedical purposes. A hybrid drug nanocarrier based on a PDA decorated with polyamidoamine (PAMAM) dendrimers G 3.0 (DG3) followed by a connection with glycol (PEG) moieties, folic acid (FA), and drug doxorubicin (DOX) was used for combined chemo- and photothermal therapy (CT-PTT) of liver cancer. Oxidative stress plays a crucial role in the development of cancer, and PDA seems to have the ability to both donate and accept electrons. We investigated oxidative stress in organs by evaluating oxidative stress markers in vivo. In the liver, the level of reduced glutathione (GSH) was lower and the level of Trolox equivalent antioxidant capacity (TEAC) was higher in the group receiving doxorubicin encapsulated in PDA nanoparticles with phototherapy (PDA@DG3@PEG@FA@DOX + PTT) compared to the control group. The concentration of thiobarbituric acid reactive substances (TBARS) in livers, was higher in the group receiving PDA coated with PAMAM dendrimers and functionalized with PEG and FA (PDA@DG3@PEG@FA) than in other groups. Markers in the brain also showed lower levels of GSH in the PDA@DG3@PEG@FA group than in the control group. Markers of oxidative stress indicated changes in the organs of animals receiving PDA nanoparticles with PAMAM dendrimers functionalized with FA in CT-PTT of liver cancer under in vivo conditions. Our work will provide insights into oxidative stress, which can be an indicator of the toxic potential of PDA nanoparticles and provide new strategies to improve existing therapies.

Antibacterial and antioxidant properties of phenolic acid grafted chitosan and its application in food preservation: A review

Chitosan is a bio-renewable natural polymeric material. The antibacterial and antioxidant activity of chitosan can be enhanced by grafting with phenolic acids to further expand its application in food. Therefore, this paper focuses on reviewing the structure, antimicrobial and antioxidant activities and their mechanisms with phenolic acid-g-CS, evaluating its cytotoxicity, and describing its application in various food preservation. In general, different reaction mechanisms of phenolic acid-g-CS synthesis lead to different product structures. Compared to chitosan, phenolic acid-g-chitosan exhibited enhanced antibacterial and antioxidant activities. The toxicity assessment showed that phenolic acid-g-CS is not cytotoxic. Moreover, phenolic acid-g-CS has been applied to a variety of food products such as fruits, vegetables and meat with good results. Overall, this review provides a certain reference for subsequent researchers to design phenolic acid-g-CS more rationally and for the subsequent development of phenolic acid-g-CS in food preservation.

Chitosan and chito-oligosaccharide: a versatile biopolymer with endless grafting possibilities for multifarious applications

Chito-oligosaccharides (COS), derived from chitosan (CH), are attracting increasing attention as drug delivery carriers due to their biocompatibility, biodegradability, and mucoadhesive properties. Grafting, the process of chemically modifying CH/COS by adding side chains, has been used to improve their drug delivery performance by enhancing their stability, targeted delivery, and controlled release. In this review, we aim to provide an in-depth study on the recent advances in the grafting of CH/COS for multifarious applications. Moreover, the various strategies and techniques used for grafting, including chemical modification, enzymatic modification, and physical modification, are elaborated. The properties of grafted CH/COS, such as stability, solubility, and biocompatibility, were reported. Additionally, the review detailed the various applications of grafted CH/COS in drug delivery, including the delivery of small drug molecule, proteins, and RNA interference therapeutics. Furthermore, the effectiveness of grafted CH/COS in improving the pharmacokinetics and pharmacodynamics of drugs was included. Finally, the challenges and limitations associated with the use of grafted CH/COS for drug delivery and outline directions for future research are addressed. The insights provided in this review will be valuable for researchers and drug development professionals interested in the application of grafted CH/COS for multifarious applications.

Electro-Biofabrication. Coupling Electrochemical and Biomolecular Methods to Create Functional Bio-Based Hydrogels

Twenty years ago, this journal published a review entitled "Biofabrication with Chitosan" based on the observations that (i) chitosan could be electrodeposited using low voltage electrical inputs (typically less than 5 V) and (ii) the enzyme tyrosinase could be used to graft proteins (via accessible tyrosine residues) to chitosan. Here, we provide a progress report on the coupling of electronic inputs with advanced biological methods for the fabrication of biopolymer-based hydrogel films. In many cases, the initial observations of chitosan's electrodeposition have been extended and generalized: mechanisms have been established for the electrodeposition of various other biological polymers (proteins and polysaccharides), and electrodeposition has been shown to allow the precise control of the hydrogel's emergent microstructure. In addition, the use of biotechnological methods to confer function has been extended from tyrosinase conjugation to the use of protein engineering to create genetically fused assembly tags (short sequences of accessible amino acid residues) that facilitate the attachment of function-conferring proteins to electrodeposited films using alternative enzymes (e.g., transglutaminase), metal chelation, and electrochemically induced oxidative mechanisms. Over these 20 years, the contributions from numerous groups have also identified exciting opportunities. First, electrochemistry provides unique capabilities to impose chemical and electrical cues that can induce assembly while controlling the emergent microstructure. Second, it is clear that the detailed mechanisms of biopolymer self-assembly (i.e., chitosan gel formation) are far more complex than anticipated, and this provides a rich opportunity both for fundamental inquiry and for the creation of high performance and sustainable material systems. Third, the mild conditions used for electrodeposition allow cells to be co-deposited for the fabrication of living materials. Finally, the applications have been expanded from biosensing and lab-on-a-chip systems to bioelectronic and medical materials. We suggest that electro-biofabrication is poised to emerge as an enabling additive manufacturing method especially suited for life science applications and to bridge communication between our biological and technological worlds.

Chitin and Chitosan as Polymers of the Future-Obtaining, Modification, Life Cycle Assessment and Main Directions of Application

Natural polymers are very widespread in the world, which is why it is so important to know about the possibilities of their use. Chitin is the second most abundant reproducible natural polymer in nature; however, it is insoluble in water and basic solvents. Chitin is an unused waste of the food industry, for which there are possibilities of secondary management. The research led to obtaining a soluble, environmentally friendly form of chitin, which has found potential applications in the many fields, e.g., medicine, cosmetics, food and textile industries, agriculture, etc. The deacetylated form of chitin, which is chitosan, has a number of beneficial properties and wide possibilities of modification. Modification possibilities mean that we can obtain chitosan with the desired functional properties, facilitating, for example, the processing of this polymer and expanding the possibilities of its application, also as biomimetic materials. The review contains a rich description of the possibilities of modifying chitin and chitosan and the main directions of their application, and life cycle assessment (LCA)-from the source of the polymer through production materials to various applications with the reduction of waste.

Green Synthesis of Thiazolidine-2,4-dione Derivatives and Their Lipoxygenase Inhibition Activity With QSAR and Molecular Docking Studies

Thiazolidinediones are five-membered, heterocyclic compounds that possess a number of pharmacological activities such as antihyperglycemic, antitumor, antiarthritic, anti-inflammatory, and antimicrobial. Conventional methods for their synthesis are often environmentally unacceptable due to the utilization of various catalysts and organic solvents. In this study, deep eutectic solvents were used in the synthesis of thiazolidinedione derivatives that acted as both solvents and catalysts. Initially, a screening of 20 choline chloride-based deep eutectic solvents for thiazolidinedione synthesis, via Knoevenagel condensation, was performed in order to find the most suitable solvent. Deep eutectic solvent, choline chloride, N-methylurea, was proven to be the best for further synthesis of 19 thiazolidinedione derivatives. Synthesized thiazolidinediones are obtained in yields from 21.49% to 90.90%. The synthesized compounds were tested for the inhibition of lipid peroxidation as well as for the inhibition of soy lipoxygenase enzyme activity. The antioxidant activity of the compounds was also determined by the ABTS and DPPH methods. Compounds showed lipoxygenase inhibition in the range from 7.7% to 76.3%. Quantitative structure–activity relationship model (R2 = 0.88; Q2loo = 0.77; F = 33.69) for the inhibition of soybean lipoxygenase was obtained with descriptors Mor29m, G2u, and MAXDP. The molecular docking confirms experimentally obtained results, finding the binding affinity and interactions with the active sites of soybean LOX-3.

Network-Based Redox Communication Between Abiotic Interactive Materials

Recent observations that abiotic materials can engage in redox-based interactive communication motivates the search for new redox-active materials. Here we fabricated a hydrogel from a four-armed thiolated polyethylene glycol (PEG-SH) and the bacterial metabolite, pyocyanin (PYO). We show that: (i) the PYO-PEG hydrogel is reversibly redox-active; (ii) the molecular-switching and directed electron flow within this PYO-PEG hydrogel requires both a thermodynamic driving force (i.e., potential difference) and diffusible electron carriers that serve as nodes in a redox network; (iii) this redox-switching and electron flow is controlled by the redox network’s topology; and (iv) the ability of the PYO-PEG hydrogel to “transmit” electrons to a second insoluble redox-active material (i.e., a catechol-PEG hydrogel) is context-dependent (i.e., dependent on thermodynamic driving forces and appropriate redox shuttles). These studies provide an experimental demonstration of important features of redox-communication and also suggest technological opportunities for the fabrication of interactive materials.

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Thiol-pyocyanin reaction was used to create a redox-active and interactive hydrogel

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The electron flow and molecular switching requires diffusible mediators

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These mediators and pyocyanin hydrogel serve as “nodes” in a redox reaction network

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The networked flow of electrons between two separated hydrogels is reported

Disentangling the Puzzling Regiochemistry of Thiol Addition to o-Quinones

The addition of thiol compounds to o-quinones, as exemplified by the biologically relevant conjugation of cysteine to dopaquinone, displays an anomalous 1,6-type regiochemistry compared to the usual 1,4-nucleophilic addition, for example, by amines, which has so far eluded intensive investigations. By means of an integrated experimental and computational approach, herein, we provide evidence that the addition of glutathione, cysteine, or benzenethiol to 4-methyl-o-benzoquinone, modeling dopaquinone, proceeds by a free radical chain mechanism triggered by the addition of thiyl radicals to the o-quinone. In support of this conclusion, DFT calculations consistently predicted the correct regiochemistry only for the proposed thiyl radical-quinone addition pathway. These results would prompt a revision of the commonly accepted mechanisms for thiol-o-quinone conjugation and stimulate further work aimed at assessing the impact of the free radical processes in biologically relevant thiol–quinone interactions.

Research Progress of Chitosan-Based Biomimetic Materials

Chitosan is a linear polysaccharide produced by deacetylation of natural biopolymer chitin. Owing to its good biocompatibility and biodegradability, non-toxicity, and easy processing, it has been widely used in many fields. After billions of years of survival of the fittest, many organisms have already evolved a nearly perfect structure. This paper reviews the research status of biomimetic functional materials that use chitosan as a matrix material to mimic the biological characteristics of bivalves, biological cell matrices, desert beetles, and honeycomb structure of bees. In addition, the application of biomimetic materials in wound healing, hemostasis, drug delivery, and smart materials is briefly overviewed according to their characteristics of adhesion, hemostasis, release, and adsorption. It also discusses prospects for their application and provides a reference for further research and development.

Molecular Networking Discloses the Chemical Diversity of Flavonoids and Selaginellins in Selaginella convoluta

Selaginella convoluta is a desiccation tolerant plant native to the Brazilian semiarid region (Caatinga), endowed with an effective drought resistance mechanism. As part of our research efforts to understand the chemical diversity of S. convoluta, dehydrated (harvested in their natural habitat in the dry season) and hydrated (plant acclimated in a laboratory after rehydration) specimens were analyzed by HR-LC-ESI-MS/MS followed by a structural annotation on the Global Natural Products Social Molecular Networking Web platform. The molecular networking approach allowed for putative annotation of 39 metabolites, mainly selaginellins and flavonoids. Based on MS/MS data, three unprecedented selaginellins were annotated: 29-hydroxy selaginellin O, 29-hydroxy selaginellin A, and 4-{[2-(4-hydrophenyl)-6-[2-(4-hydroxyphenyl)ethynyl]phenyl](4-oxocyclohexa-2,5-dien-1-ylidene)methyl}benzaldehyde. Th results pointed out that valuable scientific knowledge can be obtained from studies conducted with plants in their natural habitat by allowing a more realistic profile of chemical diversity. The present study adds new information on specialized metabolites of S. convoluta, mainly flavonoids and selaginellins, and highlights the species as an untapped source of chemobiodiversity from Caatinga.