Self-assembly of kraft lignin-acrylamide polymers

Recent advance in preparation of lignin nanoparticles and their medical applications: A review

BACKGROUND

Lignin has attracted a lot of attention because it is non-toxic, renewable and biodegradable. Lignin nanoparticles (LNPs) have high specific surface area and specific surface charges. It provides LNPs with good antibacterial and antioxidant properties. LNPs preparation has become clear, however, the application remains in the early stages.

PURPOSE

A review centric research has been conducted, reviewing existing literature to accomplish a basic understanding of the medical applications of LNPs.

METHODS

Initially, we extensively counseled the heterogeneity of lignin from various sources. The size and morphology of LNPs from different preparation process were then discussed. Subsequently, we focused on the potential medical applications of LNPs, including drug delivery, wound healing, tissue engineering, and antibacterial agents. Lastly, we explained the significance of LNPs in terms of antibacterial, antioxidant and biocompatibility, especially highlighting the need for an integrated framework to understand a diverse range of medical applications of LNPs.

RESULTS

We outlined the chemical structure of different type of lignin, and highlighted the advanced methods for lignin nanoparticles preparation. Moreover, we provided an in-depth review of the potential applications of lignin nanoparticles in various medical fields, especially in drug carriers, wound dressings, tissue engineering components, and antimicrobial agents.

CONCLUSION

This review provides a detailed overview on the current state and progression of lignin nanoparticles for medical applications.

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.

Lignin grafted hydroxyapatite entrapped in polyacrylamide: Characterization and adsorptive features for Th4+ and bovine serum albumin

Water-soluble sulfolignin (SL) was grafted onto hydroxyapatite (Hap) by using epichlorohydrin. SLgHap was then entrapped in cross-linked polyacrylamide by in situ polymerizations of acrylamide and N, N'-methylenebisacrylamide to obtain the composite of PSLgHap. The composite was characterized by FT-IR, BET- porosity, XRD, EDXRF, SEM-EDX, TGA-DTG, PZC, CEC, and swelling tests. The adsorptive features of PSLgHAP were investigated for Th⁴⁺ and BSA in view of its dependence on pH, ionic intensity, concentration, temperature, and time. The results of characterization tests confirmed the formation of PSLgHap. The grafting efficiency concerning sulfur contents of PSLgHap was 96% by EDXRF. The isotherms were best represented by the Sips model, Langmuir adsorption capacities were 369 and 390 mg g_SLgHap^-1 for BSA and Th⁴⁺. The enthalpy and entropy changes were positive whilst Gibbs energy was negative by entropy controlled. The adsorption kinetics of both species was obeyed to pseudo second-order model, whereas it was first-order for BSA and hybrid-order for Th⁴⁺ of Langmuir model.

Facile fabrication and characterization of kraft lignin@Fe3O4 nanocomposites using pH driven precipitation: Effects on increasing lignin content

This work offers a facile fabrication method for lignin nanocomposites through the assembly of kraft lignin onto magnetic nanoparticles (Fe3O4) based on pH-driven precipitation, without needing organic solvents or lignin functionalization. Kraft lignin@Fe3O4 multicore nanocomposites fabrication proceeded using a simple, pH-driven precipitation technique. An alkaline solution for kraft lignin (pH 12) was rapidly injected into an aqueous-based Fe3O4 nanoparticle colloidal suspension (pH 7) under constant mixing conditions, allowing the fabrication of lignin magnetic nanocomposites. The effects of increasing lignin to initial Fe3O4 mass content (g/g), increasing in ratio from 1:1 to 20:1, are discussed with a complete chemical, structural, and morphological characterization. Results showed that nanocomposites fabricated above 5:1 lignin:Fe3O4 had the highest lignin coverage and content (>20%), possessed superparamagnetic properties (Ms ≈ 45,000 A·m2/kg2); had a negative surface charge (-30 mV), and formed multicore nanostructures (DH ≈ 150 nm). The multicore lignin@Fe3O4 nanocomposites allowed rapid magnetically induced separations from suspension. After 5 min exposure to a rare-earth neodymium magnet (1.27 mm × 1.27 mm × 5.08 mm), lignin@Fe3O4 nanocomposites exhibited a maximum methylene blue removal efficiency of 74.1% ± 7.1%. These nanocomposites have potential in magnetically induced separations to remove organic dyes, heavy metals, or other lignin adsorbates.

Production and Application of Triblock Hydrolysis Lignin-Based Anionic Copolymers in Aqueous Systems

Although lignin is currently an under-utilized biopolymer, it has the potential to be valorized through different modification pathways to yield alternative products to petroleum-based ones. In this work, hydrolysis lignin (HL) was copolymerized with acrylamide (AM) and acrylic acid (AA) under acidic conditions to generate the lignin/AM polymer (HM), lignin/AA polymer (HA), and lignin/AM/AA copolymer (HAM) with different negative charge densities and molecular weights. Lignin-based polymers characterized by advanced tools, such as proton nuclear magnetic resonance (1H NMR), gel permission chromatography (GPC), and elemental analysis confirmed the successful polymerization of HL with AM, AA, or AM/AA monomers. The adsorption analysis using a quartz crystal microbalance (QCM) revealed that compared to diblock HM and HA, the triblock copolymers of HAM adsorbed more on the Al2O3 surface and generated a bulkier adsorbed layer, which is important for lignin-based coating formulation. HAM1 with a lower charge density yielded a higher surface excess density, while HAM2 with a larger R h occupied more space (153.7 Å2) at the interface of water and Al2O3. In suspension systems, because of the higher M w, R h, and adsorption affinity, the bridging performance of HAM2 was more remarkable than that of the other lignin derivatives for Al2O3 particles via forming stronger flocs (with a deflocculation parameter, T df, of 80.6 s). However, the diblock lignin-AA (HA1) polymer showed the fastest floc regrowth capability after reducing the shear forces (with a reflocculation parameter, T rf, of 62.5 s). The high thermal stability, T g, and rheological characteristics of the HAM copolymer proved that it can be an excellent material for coating formulations and flocculants for wastewater treatment systems.

Lignin-Graft-Poly(lactic-co-glycolic) Acid Biopolymers for Polymeric Nanoparticle Synthesis

A lignin-graft-poly(lactic-co-glycolic) acid (PLGA) biopolymer was synthesized with two types of lignin (LGN), alkaline lignin (ALGN) and sodium lignosulfonate (SLGN), at different (A/S)LGN/PLGA ratios (1:2, 1:4, and 1:6 w/w). 1H NMR and Fourier-transform infrared spectroscopy (FT-IR) confirmed the conjugation of PLGA to LGN. The (A/S)LGN-graft-PLGA biopolymers were used to form nanodelivery systems suitable for entrapment and delivery of drugs for disease treatment. The LGN-graft-PLGA NPs were generally small (100-200 nm), increased in size with the amount of PLGA added, monodisperse, and negatively charged (-48 to -60 mV). Small-angle scattering data showed that particles feature a relatively smooth surface and a compact spherical structure with a distinct core and a shell. The core size and shell thickness varied with the LGN/PLGA ratio, and at a 1:6 ratio, the particles deviated from the core-shell structure to a complex internal structure. The newly developed (A/S)LGN-graft-PLGA NPs are proposed as a potential delivery system for applications in biopharmaceutical, food, and agricultural sectors.