Lignin-Based Nanoparticles as Both Structural and Active Elements in Self-Assembling and Self-Healing Multifunctional Hydrogels for Chronic Wound Management

Adverse Outcome Pathways (AOPs) Oriented Approach to Assess In Vitro Hazard of Silica and Lignin Nanomaterials Derived from Biomass Residues

Bio-based nanomaterials (B-NMs), such as silica oxide (SiO2)- and lignin (Lig)- based nanoparticles (NPs) derived from biomass waste, have gained attention in the last few years in the view of promoting the sustainability principles in several applications. However, scarce data are available about their safety. Thus, a hazard-testing strategy was designed considering as a reference the safe-and-sustainable-by-design (SSbD) framework for chemicals and materials, prioritizing the use of new approach methodologies (NAMs), such as in vitro and adverse outcome pathways (AOPs) approaches, for generating data about the potential hazard of B-NMs. Literature research was performed to identify the adverse outcomes (AOs) related to the selected B-NMs. All the AOPs investigated shared at least oxidative stress, inflammation and cytotoxicity as key events (KEs) that were investigated in lung and immune cells. The tested B-NMs resulted either non-toxic or moderately toxic towards human cells, validating their biocompatibility when compared to reference NMs of similar composition, but not of bio-origin. However, attention should be given to possible AOs deriving after specific functionalization of the B-NMs. Considering the lack of knowledge in this field, the studies performed represent a step forward in the state of the art of the safety assessment of B-NMs.

On-demand Opto-Laser activatable nanoSilver ThermoGel for treatment of full-thickness diabetic wound in a mouse model

Patients suffering from diabetes mellitus are prone to develop diabetic wounds that are non-treatable with conventional therapies. Hence, there is an urgent need of hour to develop the therapy that will overcome the lacunas of conventional therapies. This investigation reports the Quality by Design-guided one-pot green synthesis of unique Opto-Laser activatable nanoSilver ThermoGel (OL→nSil-ThermoGel) for hyperthermia-assisted treatment of full-thickness diabetic wounds in mice models. The characterization findings confirmed the formation of spherical-shaped nanometric Opto-Laser activatable nanoSilver (30.75 ± 2.7 nm; ∆T: 37 ± 0.2 °C → 66.2 ± 0.1 °C; at 1.8 W/cm2 NIR laser density). The findings indicated acceptable in vitro cytocompatibility and significant keratinocyte migration (95.04 ± 0.07 %) activity of OL→nSil towards HaCaT cells. The rheological data of OL→nSil hybridized in situ thermoresponsive gel (OL→nSil-ThermoGel) showed the gelling temperature at 32 ± 2 °C. In vivo studies on full-thickness diabetic wounds in a Mouse model showed OL→nSil-ThermoGel accelerated wound closure (94.42 ± 1.03 %) and increased collagen synthesis, angiogenesis, and decreased inflammatory markers. Similarly, immunohistochemistry study showed significant angiogenesis and faster phenotypic switching of fibroblasts to myofibroblasts in OL→nSil-ThermoGel treated diabetic wounds. Histological evaluation revealed a marked rise in keratinocyte migration, organized collagen deposition, and early regeneration of the epithelial layer compared to the diabetic wound control. In conclusion, the OL→nSil-ThermoGel modulates the cytokines, re-epithelialization, protein expression, and growth factors, thereby improving the repair and regeneration of diabetic wounds in mice.

A review of lignin application in hydrogel dressing

Lignin is the most abundant natural aromatic polymer in the world. Currently, researchers have developed a number of lignin-based composite materials that are widely used in various fields, including industry, agriculture and medicine. Especially in recent years, lignin has attracted great interest as a high-value product for biomedical applications. Due to its antioxidant, antibacterial, adhesive and other properties, lignin is a promising candidate for the development of hydrogel dressings. However, there is no comprehensive overview of the application of lignin-based hydrogel dressings. In this review, lignin-based hydrogel skin dressings were first presented, and the preparation methods of physical and chemical crosslinking in lignin-based hydrogel dressings were discussed. In addition, various functional and environmentally responsive lignin-based hydrogel dressings were primarily reviewed. Finally, the prospects for the development of novel multifunctional lignin-based hydrogel dressings in the future were presented. In conclusion, this review provided a timely and comprehensive summary of the latest advances in the use of lignin as a biomaterial for hydrogel dressings, which would provide valuable guidance for the further development of lignin-based hydrogels.

Mini-review on lignin-based self-healing polymer

Lignin, a biopolymer derived from plant biomass, is recognized as a highly promising substance for developing self-healing polymers owing to its dynamic linkages and functional groups. This paper provides a thorough review of lignin-based self-healing polymer, from the process of extracting lignin, chemical modification, synthesis techniques such as via reversible addition-fragmentation chain transfer (RAFT) polymerization, crosslinking with polymers like polyvinyl alcohol (PVA) and chitosan, and reactions with isocyanates to create lignin-based networks with reversible interactions. This work also summarizes the optimization of self-healing ability, such as including dynamic copolymers, encapsulating healing agents like dicyclopentadiene and polycaprolactone (PCL), and chain extenders with disulfide or Diels-Alder (DA) moieties. The material's characterization focuses on its capacity to recover via hydrogen bonding and dynamic re-associations, improved mechanical properties from lignin's rigid structure, and enhanced temperature resistance. Primary obstacles involve the optimization of lignin extraction, enhancement of polymer compatibility, and the establishment of efficient procedures for synthesis and characterization. Overall, lignin shows great potential as a renewable component of self-healing polymers, with plenty of opportunities for further development.

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.

Lignin - A green material for antibacterial application - A review

Lignin's antibacterial properties have become increasingly relevant due to the rise of microbial infectious diseases and antibiotic resistance. Lignin is capable of interacting electrostatically with bacteria and contains polyphenols that cause damage to their cell walls. These features make lignin a desirable material to exhibit antibacterial behavior. Therefore, lignin in antibacterial applications offers a novel approach to address the growing need for sustainable and effective antibacterial materials. Recent research has explored the incorporation of lignin in various biomedical applications, such as wound dressings, implants, and drug delivery systems, highlighting their potential as a sustainable alternative to synthetic antibacterial agents. Furthermore, the development of lignin-based nanomaterials with enhanced antimicrobial activity is an active area of research that holds great promise for the future. In this review, we have provided a summary of how lignin can be incorporated into different forms, such as composite and non-composite synthesis of antibacterial agents and their performances. The challenges and future considerations are also discussed in this review article.

Hydrogels based on lignin extracted from cashew apple bagasse and its application in antimicrobial wound dressings

Hydrogels are versatile materials with a three-dimensional network structure that can retain water and release bioactive compounds. They have found applications in various fields, including agriculture, biomaterial synthesis, and pharmaceuticals. Incorporating natural antimicrobial compounds into hydrogels is a promising approach to developing non-toxic biomedical materials, particularly for wound healing dressings. It was evaluated the extraction and use of cashew apple bagasse lignin (CAB-Lig) due to its healing, anti-inflammatory, and antimicrobial properties for producing a hydrogel-based bandage. The extraction process involved acid and alkali treatments followed by precipitation. The antimicrobial potential of CAB-Lig was evaluated at different concentrations for formulating hydrogels. Hydrogels containing 0.1 % and 3 % lignin showed high swelling and liquid retention abilities. The 3 % lignin hydrogel exhibited effectiveness against Escherichia coli and Staphylococcus aureus. Incorporating CAB-Lig into the hydrogel structure improved its mechanical properties, making it more suitable for application as a bandage. Moreover, the extracted lignin showed low toxicity, indicating its safe use. A bandage was formulated by combining the CAB-Lig-based hydrogel with polyester, which possessed antimicrobial properties and demonstrated biocompatibility (L929 and HaCat cells). The results confirmed the potential of CAB-Lig for synthesizing hydrogels and dressings with antimicrobial properties, offering a sustainable solution for utilizing lignocellulosic biomass.

Lignin derivatives-based hydrogels for biomedical applications

Recently, numerous studies have been conducted on renewable polymers derived from different natural sources, exploring their suitability for diverse biomedical applications. Lignin as one of the main components of lignocellulosic has garnered significant attention as a promising alternative to petroleum-based polymers. This interest is primarily due to its cost-effectiveness, biocompatibility, eco-friendly nature, as well as its antioxidant and antimicrobial properties. These characteristics could be more beneficial when incorporating lignin into the formulation of value-added products. Although lignin has a chemical structure that is suitable for various applications, these characteristics require modifications to guarantee that the resultant materials display the desired biological, chemical, and physical properties when applied in the creation of biodegradable hydrogels, particularly for biomedical purposes. This study delineates the recent modification approaches that have been employed in the creation of lignin-based hydrogels. These strategies encompass both chemical and physical interactions with other polymers. Additionally, this review encompasses an examination of the current applications of lignin hydrogels, spanning their use as scaffolds for tissue engineering, carriers for pharmaceuticals, materials for wound dressings and biosensors, and elements in flexible and wearable electronics. Finally, we delve into the challenges and constraints associated with these materials, discuss the necessary steps required to attain the appropriate properties for the development of innovative lignin-based hydrogels, and derive conclusions based on the presented findings.

Wound healing strategies based on nanoparticles incorporated in hydrogel wound patches

The intricate, tightly controlled mechanism of wound healing that is a vital physiological mechanism is essential to maintaining the skin's natural barrier function. Numerous studies have focused on wound healing as it is a massive burden on the healthcare system. Wound repair is a complicated process with various cell types and microenvironment conditions. In wound healing studies, novel therapeutic approaches have been proposed to deliver an effective treatment. Nanoparticle-based materials are preferred due to their antibacterial activity, biocompatibility, and increased mechanical strength in wound healing. They can be divided into six main groups: metal NPs, ceramic NPs, polymer NPs, self-assembled NPs, composite NPs, and nanoparticle-loaded hydrogels. Each group shows several advantages and disadvantages, and which material will be used depends on the type, depth, and area of the wound. Better wound care/healing techniques are now possible, thanks to the development of wound healing strategies based on these materials, which mimic the extracellular matrix (ECM) microenvironment of the wound. Bearing this in mind, here we reviewed current studies on which NPs have been used in wound healing and how this strategy has become a key biotechnological procedure to treat skin infections and wounds.

Continuous sonochemical nanotransformation of lignin - Process design and control

As the most abundant renewable aromatic polymer on the planet, lignin is gaining growing interest in replacing petroleum-based chemicals and products. However, only <5 % of industrial lignin waste is revalorized in its macromolecular form as additives, stabilizing agents or dispersant and surfactants. Herein, revalorization of this biomass was achieved by implementing an environmentally-friendly continuous sonochemical nanotransformation to obtain highly concentrated lignin nanoparticles (LigNPs) dispersions for added-value material applications. With the aim to further model and control a large-scale ultrasound-assisted lignin nanotransformation, a two-level factorial design of experiment (DoE) was implemented varying the ultrasound (US) amplitude, flow rate, and lignin concentration. Size and polydispersity measurements together with the UV-Vis spectra of lignin recorded at different time intervals of sonication allowed to monitor and understand the sonochemical process on a molecular level. The light scattering profile of sonicated lignin dispersions showed a significant particle size reduction in the first 20 min, followed by moderate particle size decrease below 700 nm until the end of the 2 h process. The response surface analysis (RSA) of the particle size data revealed that the lignin concentration and sonication time were the most important factors to achieve smaller NPs. From a mechanistic point of view, a strong impact of the particle-particle collisions due to sonication seems to be responsible for the decrease in particle size and homogenization of the particle distribution. Unexpectedly, a strong interaction between the flow rate and US amplitude on the particle size and nanotransformation efficiency was observed, yielding smaller LigNPs at high amplitude and low flow rate or vice versa. The data derived from the DoE were used to model and predict the size and polydispersity of the sonicated lignin. Furthermore, the use of the NPs spectral process trajectories calculated from the UV-Vis spectra showed similar RSA model as the dynamic light scattering (DLS) data and will potentially allow the in-line monitoring of the nanotransformation process.

Lignin-Cobalt Nano-Enabled Poly(pseudo)rotaxane Supramolecular Hydrogel for Treating Chronic Wounds

Chronic wounds (CWs) are a growing issue for the health care system. Their treatment requires a synergic approach to reduce both inflammation and the bacterial burden. In this work, a promising system for treating CWs was developed, comprising cobalt-lignin nanoparticles (NPs) embedded in a supramolecular (SM) hydrogel. First, NPs were obtained through cobalt reduction with phenolated lignin, and their antibacterial properties were tested against both Gram-negative and Gram-positive strains. The anti-inflammatory capacity of the NPs was proven through their ability to inhibit myeloperoxidase (MPO) and matrix metalloproteases (MMPs), which are enzymes involved in the inflammatory process and wound chronicity. Then, the NPs were loaded in an SM hydrogel based on a blend of α-cyclodextrin and custom-made poly(ether urethane)s. The nano-enabled hydrogel showed injectability, self-healing properties, and linear release of the loaded cargo. Moreover, the SM hydrogel's characteristics were optimized to absorb proteins when in contact with liquid, suggesting its capacity to uptake harmful enzymes from the wound exudate. These results render the developed multifunctional SM material an interesting candidate for the management of CWs.