Lignin-Based Hollow Nanoparticles for Controlled Drug Delivery: Grafting Preparation Using β-Cyclodextrin/Enzymatic-Hydrolysis Lignin

Lignins as Promising Renewable Biopolymers and Bioactive Compounds for High-Performance Materials

The recycling of biomass into high-value-added materials requires important developments in research and technology to create a sustainable circular economy. Lignin, as a component of biomass, is a multipurpose aromatic polymer with a significant potential to be used as a renewable bioresource in many fields in which it acts both as promising biopolymer and bioactive compound. This comprehensive review gives brief insights into the recent research and technological trends on the potential of lignin development and utilization. It is divided into ten main sections, starting with an outlook on its diversity; main properties and possibilities to be used as a raw material for fuels, aromatic chemicals, plastics, or thermoset substitutes; and new developments in the use of lignin as a bioactive compound and in nanoparticles, hydrogels, 3D-printing-based lignin biomaterials, new sustainable biomaterials, and energy production and storage. In each section are presented recent developments in the preparation of lignin-based biomaterials, especially the green approaches to obtaining nanoparticles, hydrogels, and multifunctional materials as blends and bio(nano)composites; most suitable lignin type for each category of the envisaged products; main properties of the obtained lignin-based materials, etc. Different application categories of lignin within various sectors, which could provide completely sustainable energy conversion, such as in agriculture and environment protection, food packaging, biomedicine, and cosmetics, are also described. The medical and therapeutic potential of lignin-derived materials is evidenced in applications such as antimicrobial, antiviral, and antitumor agents; carriers for drug delivery systems with controlled/targeting drug release; tissue engineering and wound healing; and coatings, natural sunscreen, and surfactants. Lignin is mainly used for fuel, and, recently, studies highlighted more sustainable bioenergy production technologies, such as the supercapacitor electrode, photocatalysts, and photovoltaics.

Self-assembled/composited lignin colloids utilizing for therapy, cosmetics and emulsification

Lignin, the most abundant source of renewable aromatic compounds on the planet, is attracting more scholarly attention due to its possibility of replacing petroleum-based chemicals and products. However, it remains underutilized because of the heterogeneity of its multi-level structure that prevents homogenization and standardization of derived products. The key to solving these problems lies in finding a general preparation method to achieve the integrated utilization of lignin molecules at all levels. The assembly-mediated granulation methods provide a significant means for the integrated value-added utilization of lignin, and for biomass productization applications, it is significant to understand the molecular mechanisms of lignin nano-colloids (LNCs) formation thus accurately guiding their functionalization. Therefore, a thorough understanding of the assembly morphology and behavior of lignin in different solutions towards colloids is of great scientific importance. In this minireview, we focus on the assembly behavior of lignin in different solvents, specifically in mono-solvent and multi-solvent, and in particular, we review various methods for preparing lignin composite colloids and concentrate on the applications in therapy, cosmetics and emulsification, which are important for guiding the preparation and efficient utilization of LNCs.

Advances in Antitumor Nano-Drug Delivery Systems of 10-Hydroxycamptothecin

10-Hydroxycamptothecin (HCPT) is a natural plant alkaloid from Camptotheca that shows potent antitumor activity by targeting intracellular topoisomerase I. However, factors such as instability of the lactone ring and insolubility in water have limited the clinical application of this drug. In recent years, unprecedented advances in biomedical nanotechnology have facilitated the development of nano drug delivery systems. It has been found that nanomedicine can significantly improve the stability and water solubility of HCPT. NanoMedicines with different diagnostic and therapeutic functions have been developed to significantly improve the anticancer effect of HCPT. In this paper, we collected reports on HCPT nanomedicines against tumors in the past decade. Based on current research advances, we dissected the current status and limitations of HCPT nanomedicines development and looked forward to future research directions.

From residue to resource: new insights into the synthesis of functionalized lignin micro/nanospheres by self-assembly technology for waste resource utilization

Among the most abundant biopolymers in the biosphere, lignin is a renewable aromatic compound that represents an untapped opportunity to create new biological products. However, the complex interlacing structures of cellulose, hemicellulose and lignin, as well as the unique properties of lignin, limit the utilization of value-added lignin. Lignin-based nanomaterials open the door for lignin applications in environmental pollutant remediation, biofuel production, biomedicine, and other fields. Herein, we present various factors influencing the formation of micro-nanospheres by self-assembly techniques through a review of previous literature, and emphasize the simple and green synthesis of lignin micro/nanospheres (LMNPs) under non-modified conditions. More importantly, we discuss the mechanism of the formation of nanospheres. Considering the heterogeneity of lignin and the polarity of different solvents, we propose that self-assembly techniques should focus more on the influence brought by lignin itself or the solvent, so that the external conditions can be controlled to prepare LMNPs, which can be used in specific fields. A brief overview of the contribution of lignin-based nanomaterials in various fields is also presented. This review could provide insight for the development of lignin-based nanomaterials.

Lignin-Based Porous Biomaterials for Medical and Pharmaceutical Applications

Over the past decade, lignin-based porous biomaterials have been found to have strong potential applications in the areas of drug delivery, tissue engineering, wound dressing, pharmaceutical excipients, biosensors, and medical devices. Lignin-based porous biomaterials have the addition of lignin obtained from lignocellulosic biomass. Lignin as an aromatic compound is likely to modify the materials’ mechanical properties, thermal properties, antioxidant, antibacterial property, biodegradability, and biocompatibility. The size, shape, and distribution of pores can determine the materials’ porous structure, porosity, surface areas, permeability, porosity, water solubility, and adsorption ability. These features could be suitable for medical applications, especially controlled drug delivery systems, wound dressing, and tissue engineering. In this review, we provide an overview of the current status and future potential of lignin-based porous materials for medical and pharmaceutical uses, focusing on material types, key properties, approaches and techniques of modification and fabrication, and promising medical applications.

How far is Lignin from being a biomedical material?

Lignin is a versatile biomass that possesses many different desirable properties such as antioxidant, antibacterial, anti-UV, and good biocompatibility. Natural lignin can be processed through several chemical processes. The processed lignin can be modified into functionalized lignin through chemical modifications to develop and enhance biomaterials. Thus, lignin is one of the prime candidate for various biomaterial applications such as drug and gene delivery, biosensors, bioimaging, 3D printing, tissue engineering, and dietary supplement additive. This review presents the potential of developing and utilizing lignin in the outlook of new and sustainable biomaterials. Thereafter, we also discuss on the challenges and outlook of utilizing lignin as a biomaterial.

Lignin Nanoparticles and Alginate Gel Beads: Preparation, Characterization and Removal of Methylene Blue

A novel and effective green system consisting of deep eutectic solvent (DES) was proposed to prepare lignin nanoparticles (LNPs) without any lignin modification. The LNPs are obtained through the dialysis of the kraft lignin-DES solution. The particle size distribution, Zeta potential and morphology of the LNPs are characterized by using dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average diameter of LNPs is in the range 123.6 to 140.7 nm, and the LNPs show good stability and dispersibility in water. The composite beads composed of LNPs and sodium alginate (SA) are highly efficient (97.1%) at removing methylene blue (MB) from the aqueous solution compared to 82.9% and 77.4% by the SA/bulk kraft lignin composite and pure SA, respectively. Overall, the LNPs-SA bio-nanocomposite with high adsorption capacity (258.5 mg/g) could be useful in improving water quality and other related applications.

Wood-Derived Functional Polymeric Materials

In recent years, tremendous efforts have been dedicated to developing wood-derived functional polymeric materials due to their distinctive properties, including environmental friendliness, renewability, and biodegradability. Thus, the uniqueness of the main components in wood (cellulose and lignin) has attracted enormous interest for both fundamental research and practical applications. Herein, the emerging field of wood-derived functional polymeric materials fabricated by means of macromolecular engineering is reviewed, covering the basic structures and properties of the main components, the design principle to utilize these main components, and the resulting wood-derived functional polymeric materials in terms of elastomers, hydrogels, aerogels, and nanoparticles. In detail, the natural features of wood components and their significant roles in the fabrication of materials are emphasized. Furthermore, the utilization of controlled/living polymerization, click chemistry, dynamic bonds chemistry, etc., for the modification is specifically discussed from the perspective of molecular design, together with their sequential assembly into different morphologies. The functionalities of wood-derived polymeric materials are mainly focused on self-healing and shape-memory abilities, adsorption, conduction, etc. Finally, the main challenges of wood-derived functional polymeric materials fabricated by macromolecular engineering are presented, as well as the potential solutions or directions to develop green and scalable wood-derived functional polymeric materials.

Hybrid Tellurium-Lignin Nanoparticles with Enhanced Antibacterial Properties

The surge of antibiotic-resistant bacteria is leading to the loss of effectiveness of antibiotic treatment, resulting in prolonged infections and even death. Against this healthcare threat, antimicrobial nanoparticles that hamper the evolution of resistance mechanisms are promising alternatives to antibiotics. Herein, we used Kraft lignin, a poorly valorized polymer derived from plant biomass, to develop novel hybrid tellurium-lignin nanoparticles (TeLigNPs) as alternative antimicrobial agents. The sonochemically synthesized TeLigNPs are comprised of a lignin matrix with embedded Te clusters, revealing the role of lignin as both a reducing agent and a structural component. The hybrid NPs showed strong bactericidal effects against the Gram-negative Escherichia coli and Pseudomonas aeruginosa, achieving more than 5 log bacteria reduction, while they only slightly inhibited the growth of the Gram-positive Staphylococcus aureus. Exposure of TeLigNPs to human cells did not cause morphological changes or reduction in cell viability. Studies on the antimicrobial mechanism of action demonstrated that the novel TeLigNPs were able to disturb bacterial model membranes and generate reactive oxygen species (ROS) in Gram-negative bacteria.

Lignin Nanoparticles: A Promising Tool to Improve Maize Physiological, Biochemical, and Chemical Traits

Lignin, and its derivatives, are the subject of current research for the exciting properties shown by this biomass. Particularly attractive are lignin nanoparticles for their eco- and biocompatibility compared to other nanomaterials. In this context, the effect of nanostructured lignin microparticles (LNP), obtained from alkaline lignin by acid treatment, on maize plants was investigated. To this end, maize seeds were primed with LNP at five concentrations: 80 mg L-1 (T80), 312 mg L-1 (T312), 1250 mg L-1 (T1250), 5000 mg L-1 (T5000) and 20,000 mg L-1 (T20000). Concerning the dose applied, LNP prompted positive effects on the first stages of maize development (germination and radicle length). Furthermore, the study of plant growth, biochemical and chemical parameters on the developed plants indicated that concerning the dose applied. LNP stimulated beneficial effects on the seedlings (fresh weight and length of shoots and roots). Besides, specific treatments increased the content of chlorophyll (a and b), carotenoid, and anthocyanin. Finally, the soluble protein content showed a positive trend in response to specific dosages. These effects are significant, given the essential biological function performed by these biomolecules. In conclusion, this research indicates as the nanostructured lignin microparticles can be used, at appropriate dosages, to induce positive biological responses in maize. This beneficial action deserves attention as it candidates LNP for biostimulating a crop through seed priming.

One-pot fabrication of lignin-based aromatic porous polymers for efficient removal of bisphenol AF from water

To remove the bisphenol AF (BPAF) from aqueous solution, two different types of lignin-based aromatic porous polymers (LAPP-1 and LAPP-2) were fabricated via one-pot crosslinking of lignin with 1,4-dichloroxylene and 4,4'-bis(chloromethyl)-1,1'-biphenyl, respectively. The successful synthesis of LAPPs was confirmed by FTIR and XPS, SEM, TEM and N₂ adsorption-desorption analysis. Then, batch adsorption experiments were conducted to investigate adsorption properties toward BPAF. Based on the results, the adsorption processes were in accordance with the pseudo-second-order kinetic model and the Freundlich isotherm model, and the thermodynamic studies showed that the adsorption was a spontaneous and exothermic process. It is remarkable that LAPPs exhibited good adsorption performance in wide ranges of pH and ionic strength as well as in recycling process. Notably, compared to LAPP-1, LAPP-2 exhibited higher adsorption capacity for BPAF, which can be ascribed to its higher porosity and content of aromatic ring. Moreover, the comprehensive analysis of experimental and theoretical results indicated that the π-π interactions and pore adsorption may jointly drive the uptake process of BPAF. Considering the simple fabrication method employed and excellent BPAF adsorption performance, LAPPs provided new insights into the development of advanced lignin-based adsorbents for removal of BPAF from water.