Synthesis of lignin-based hydrogels and their applications in agriculture: A review

Lignin-based hydrogels for application in agriculture: A review

Agriculture is an important sector for maintaining environmental sustainability and ensuring global food security. However, the sector faces significant challenges caused by soil degradation, water scarcity, and resource limitations. To overcome the challenges, several studies have shown that innovative materials, including hydrogels, have the ability to improve agricultural practices. Lignin, the sole polyaromatic biopolymer, and the second most abundant biopolymer, has been extensively explored for a wide range of applications. For example, lignin valorization represents a significant issue for lignocellulosic biorefineries as well as the pulp and paper industry. This has led to an increase in interest over the past decade in its utilization to create innovative, advanced smart materials. Therefore, this study aims to discuss the applications, advantages, and possibilities of lignin-based hydrogels in addressing the primary difficulties of contemporary agriculture to increase sustainability. The initial section of the study discussed the introduction of lignin and its isolation methods, followed by an in-depth examination of polymeric hydrogels, encompassing their composition and applications in agriculture. The third section focused on lignin-based hydrogels, detailing preparation procedures for their primary application in agriculture. This study also analyzed the progress in lignin-based hydrogels over the past decade and provided a relevant assessment of the promising material.

A comprehensive review of sustainable hydrogels from lignin for advanced wastewater solutions

Throughout the recent years, water bodies have been significantly contaminated via various industrial and pollution wastes posing threats to the living. To tackle the situation, Lignin-Based Hydrogels have appeared as a material with great potential for wastewater treatment. Biomass-derived polymers for wastewater treatment present a sustainable replacement to plastics based on petroleum owing to its biocompatibility, affordability, eco-friendliness and biodegradability. After cellulose the lignin is the second highest polyaromatic bio-polymer in plants. And serves as the Earth's primary renewable source for aromatic materials. Structurally, it is a cross-linked polymer enriched with hydrophilic functional groups like hydroxyls, methoxyls, carbonyls that makes it a promising precursor towards hydrogel development. This review focuses on hydrogels based on lignin, highlighting their synthesis, traits and potential functions in water treatment. It also examines various methods for extracting lignin from different raw materials. Challenges and limitations associated with real-world applications of LBHs are addressed and along with prospects for future research. Ultimately, this review provides valuable insights into developing sustainable hydrogels based on lignin for efficient elimination of aquatic contaminants.

Lignin-Based Functional Materials in Agricultural Application: A Review

The demand for biodegradable, sustainable, and eco-friendly alternatives is growing in crop production and protection, which forces an urgent need for society to shift toward more sustainable agricultural development. In recent years, the development and research of lignin-based functional materials have gained increasing attention and impetus, and their use has become more widespread in sustainable agriculture. This review covers the latest research on the potential applications of lignin-based functional materials in plant protectants, sensors for pollutant detection, toxic element removal in soil and water, enzyme immobilization, plant growth regulators/biostimulants, hydrogels, and mulching films. Finally, future challenges and perspectives of lignin-based functional materials are discussed to provide a new strategy for the promotion of sustainable agriculture.

Exploiting lignin-based nanomaterials for enhanced anticancer therapy: A comprehensive review and future direction

Lignin, a renewable and abundant natural polymer, has emerged as a promising candidate for anticancer therapy due to its unique properties and biocompatibility. This review provides a comprehensive overview of recent advancements in the utilization of lignin-based nanomaterials for enhancing anticancer drug delivery and therapeutic outcomes. A detailed examination of the literature reveals several synthesis methods, including nanoprecipitation, microemulsion, and solvent exchange, which produce lignin nanoparticles with improved drug solubility and bioavailability. The anticancer mechanisms of lignin nanoparticles, such as the generation of reactive oxygen species (ROS), induction of apoptosis, and enhanced cellular uptake, are also explored. Lignin nanoparticles loaded with drugs like curcumin, doxorubicin, camptothecin, and resveratrol have demonstrated the ability to improve drug efficacy, selectively target cancer cells, overcome multidrug resistance, and minimize toxicity in both in vitro and in vivo studies. These nanoparticles have shown significant potential in suppressing tumor growth, inducing cell death through apoptotic pathways, and enhancing the synergistic effects of combination therapies, such as chemo-phototherapy. Future research directions include optimizing lignin nanoparticle formulations for clinical applications, refining targeted delivery mechanisms to cancer cells, and conducting thorough biocompatibility and toxicity assessments. Overall, this review highlights the significant progress made in utilizing lignin-based nanomaterials for cancer therapy and outlines promising areas for further exploration in this rapidly evolving field.

Agriculture 4.0: Polymer Hydrogels as Delivery Agents of Active Ingredients

The evolution from conventional to modern agricultural practices, characterized by Agriculture 4.0 principles such as the application of innovative materials, smart water, and nutrition management, addresses the present-day challenges of food supply. In this context, polymer hydrogels have become a promising material for enhancing agricultural productivity due to their ability to retain and then release water, which can help alleviate the need for frequent irrigation in dryland environments. Furthermore, the controlled release of fertilizers by the hydrogels decreases chemical overdosing risks and the environmental impact associated with the use of agrochemicals. The potential of polymer hydrogels in sustainable agriculture and farming and their impact on soil quality is revealed by their ability to deliver nutritional and protective active ingredients. Thus, the impact of hydrogels on plant growth, development, and yield was discussed. The question of which hydrogels are more suitable for agriculture-natural or synthetic-is debatable, as both have their merits and drawbacks. An analysis of polymer hydrogel life cycles in terms of their initial material has shown the advantage of bio-based hydrogels, such as cellulose, lignin, starch, alginate, chitosan, and their derivatives and hybrids, aligning with sustainable practices and reducing dependence on non-renewable resources.

Synthesis of xylan and lignin based hydrogels and their use as growth media for rice (Oryza sativa)

Different hydrogels were synthesised using lignin and xylan (extracted from rice straw) as the raw material, PVA as matrix template, citric acid, and succinic acid as crosslinkers and were structurally characterised by FT-IR and SEM analysis. Citric acid cross-linked hydrogels caused loose bonding between polymers and resulted in formation of large pores whereas succinic acid cross-linked hydrogels were observed to have less porosity and tight bonding network. The swelling ratio and reswelling capacity of hydrogels revealed that lignin hydrogels outperformed all other hydrogels. All the synthesised hydrogels were tested for their use as soil culture media ingredient for the germination of rice seedlings. All the hydrogels performed well in stress conditions as compared to normal conditions. Xylan/lignin hydrogel and lignin hydrogels performed best under stress conditions. These hydrogels could be used effectively as an ingredient of soil culture media owing to their tendency to absorb and retain water properly.

Sustainable Biomass Lignin-Based Hydrogels: A Review on Properties, Formulation, and Biomedical Applications

Different techniques have been developed to overcome the recalcitrant nature of lignocellulosic biomass and extract lignin biopolymer. Lignin has gained considerable interest owing to its attractive properties. These properties may be more beneficial when including lignin in the preparation of highly desired value-added products, including hydrogels. Lignin biopolymer, as one of the three major components of lignocellulosic biomaterials, has attracted significant interest in the biomedical field due to its biocompatibility, biodegradability, and antioxidant and antimicrobial activities. Its valorization by developing new hydrogels has increased in recent years. Furthermore, lignin-based hydrogels have shown great potential for various biomedical applications, and their copolymerization with other polymers and biopolymers further expands their possibilities. In this regard, lignin-based hydrogels can be synthesized by a variety of methods, including but not limited to interpenetrating polymer networks and polymerization, crosslinking copolymerization, crosslinking grafted lignin and monomers, atom transfer radical polymerization, and reversible addition-fragmentation transfer polymerization. As an example, the crosslinking mechanism of lignin-chitosan-poly(vinyl alcohol) (PVA) hydrogel involves active groups of lignin such as hydroxyl, carboxyl, and sulfonic groups that can form hydrogen bonds (with groups in the chemical structures of chitosan and/or PVA) and ionic bonds (with groups in the chemical structures of chitosan and/or PVA). The aim of this review paper is to provide a comprehensive overview of lignin-based hydrogels and their applications, focusing on the preparation and properties of lignin-based hydrogels and the biomedical applications of these hydrogels. In addition, we explore their potential in wound healing, drug delivery systems, and 3D bioprinting, showcasing the unique properties of lignin-based hydrogels that enable their successful utilization in these areas. Finally, we discuss future trends in the field and draw conclusions based on the findings presented.

Synthesis and Applications of Hybrid Polymer Networks Based on Renewable Natural Macromolecules

Macromolecules obtained from renewable natural sources are gaining increasing attention as components for a vast variety of sustainable polymer-based materials. Natural raw materials can facilitate continuous-flow production due to their year-round availability and short replenishment period. They also open new opportunities for chemists and biologists to design and create "bioreplacement" and "bioadvantaged" polymers, where complex structures produced by nature are being modified, upgraded, and utilized to create novel materials. Bio-based macromonomers are expected not only to compete with but to replace some petroleum-based analogs, as well. The development of novel sustainable materials is an ongoing and very dynamic process. There are multiple strategies for transforming natural macromolecules into sophisticated value-added products. Some methods include chemical modification of macromolecules, while others include blending several components into one new system. One of the most promising approaches for incorporating renewable macromolecules into new products is the synthesis of hybrid networks based on one or more natural components. Each one has unique characteristics, so its incorporation into a network brings new sustainable materials with properties that can be tuned according to their end-use. This article reviews the current state-of-the-art and future potential of renewable natural macromolecules as sustainable building blocks for the synthesis and use of hybrid polymer networks. The most recent advancements and applications that involve polymers, such as cellulose, chitin, alginic acid, gellan gum, lignin, and their derivatives, are discussed.

Current roles of lignin for the agroindustry: Applications, challenges, and opportunities

Lignin has the potential to be used as an additive, coating agent, fertilizer, plant growth stimulator, and packaging material in the agroindustry due to its functional aromatic structure. The quantitative measurement of functional groups is a significant element of the research for lignin structure since they directly impact their optical, dispersion, and chemical properties. These physical and chemical properties of lignin strongly depend on its type and source and its isolation procedure. Thus, lignin provides numerous opportunities for the circular economy in the agroindustry; however, studying and resolving the challenges associated with its separation, purification, and modification is required. This review discusses the most recent findings on lignin use in agroindustry and historical facts about lignin. The properties of lignin and its roles as coating agents, pesticide carriers, plant growth stimulators, and soil-improving agents have been summarized. The emerging challenges in the field of lignin-based agroindustry are considered, and potential future steps to overcome these challenges are discussed.

Preparation of PVA-CS/SA-Ca2+ Hydrogel with Core-Shell Structure

Hydrogels are highly hydrophilic polymers that have been used in a wide range of applications. In this study, we prepared PVA-CS/SA-Ca2+ core-shell hydrogels with bilayer space by cross-linking PVA and CS to form a core structure and chelating SA and Ca2+ to form a shell structure to achieve multiple substance loading and multifunctional expression. The morphology and structure of core-shell hydrogels were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The factors affecting the swelling properties of the hydrogel were studied. The results show that the PVA-CS/SA-Ca2+ hydrogel has obvious core and shell structures. The SA concentration and SA/Ca2+ cross-linking time show a positive correlation with the thickness of the shell structure; the PVA/CS mass ratio affects the structural characteristics of the core structure; and a higher CS content indicates the more obvious three-dimensional network structure of the hydrogel. The optimal experimental conditions for the swelling degree of the core-shell hydrogel were an SA concentration of 5%; an SA/Ca2+ cross-linking time of 90 min; a PVA/CS mass ratio of 1:0.7; and a maximum swelling degree of 50 g/g.