The interaction of wood nanocellulose dressings and the wound pathogen P. aeruginosa

Impact of defibrillation technique on the rheological, thermo-mechanical, and nutritional properties of nanosuspensions produced from multiple fractions of pinhão seed (Araucaria angustifolia (Bertol.) Kuntze)

This work aimed to evaluate the influence of the mechanical defibrillation technique on the pinhão nanosuspensions production obtained from the whole pinhão, its coat, and almond. The nanosuspensions were characterized concerning their composition, morphology, thermal stability, rheological behavior, compound profiling, and cytotoxicity. The results revealed a significant fiber content in pinhão coat nanosuspension (63.12 ± 0.52 %) and non-fiber carbohydrates in whole pinhão (59.00 ± 0.13 %) and almond (74.39 ± 0.23 %) nanosuspensions. The defibrillation process led to micro/nano-sized fibers in pinhão coat nanosuspensions and small-size starch granules in almond nanosuspensions. The nanosuspensions containing pinhão coat exhibited a gel-like behavior, while almond nanosuspensions displayed liquid-like characteristics. Pinhão coat nanosuspensions presented a significant content of flavonoids and phytosterols, whereas almond-based nanosuspensions contained substantial sugar amounts. No cytotoxicity was observed at the concentrations evaluated. These findings demonstrated that the defibrillation technique impacted the properties of pinhão constituents, allowing their application in new product development.

An overview to nanocellulose clinical application: Biocompatibility and opportunities in disease treatment

Recently, the demand for organ transplantation has promptly increased due to the enhanced incidence of body organ failure, the increasing efficiency of transplantation, and the improvement in post-transplant outcomes. However, due to a lack of suitable organs for transplantation to fulfill current demand, significant organ shortage problems have emerged. Developing efficient technologies in combination with tissue engineering (TE) has opened new ways of producing engineered tissue substitutes. The use of natural nanoparticles (NPs) such as nanocellulose (NC) and nano-lignin should be used as suitable candidates in TE due to their desirable properties. Many studies have used these components to form scaffolds and three-dimensional (3D) cultures of cells derived from different tissues for tissue repair. Interestingly, these natural NPs can afford scaffolds a degree of control over their characteristics, such as modifying their mechanical strength and distributing bioactive compounds in a controlled manner. These bionanomaterials are produced from various sources and are highly compatible with human-derived cells as they are derived from natural components. In this review, we discuss some new studies in this field. This review summarizes the scaffolds based on NC, counting nanocrystalline cellulose and nanofibrillated cellulose. Also, the efficient approaches that can extract cellulose with high purity and increased safety are discussed. We concentrate on the most recent research on the use of NC-based scaffolds for the restoration, enhancement, or replacement of injured organs and tissues, such as cartilage, skin, arteries, brain, and bone. Finally, we suggest the experiments and promises of NC-based TE scaffolds.

The emergence of hybrid cellulose nanomaterials as promising biomaterials

Cellulose nanomaterials (CNs) are promising green materials due to their unique properties as well as their environmental benefits. Among these materials, cellulose nanofibrils (CNFs) and nanocrystals (CNCs) are the most extensively researched types of CNs. While they share some fundamental properties like low density, biodegradability, biocompatibility, and low toxicity, they also possess unique differentiating characteristics such as morphology, rheology, aspect ratio, crystallinity, mechanical and optical properties. Therefore, numerous comparative studies have been conducted, and recently, various studies have reported the synergetic advantages resulting from combining CNF and CNC. In this review, we initiate by addressing the terminology used to describe combinations of these and other types of CNs, proposing "hybrid cellulose nanomaterials" (HCNs) as the standardized classifictation for these materials. Subsequently, we briefly cover aspects of properties-driven applications and the performance of CNs, from both an individual and comparative perspective. Next, we comprehensively examine the potential of HCN-based materials, highlighting their performance for various applications. In conclusion, HCNs have demonstraded remarkable success in diverse areas, such as food packaging, electronic devices, 3D printing, biomedical and other fields, resulting in materials with superior performance when compared to neat CNF or CNC. Therefore, HCNs exhibit great potential for the development of environmentally friendly materials with enhanced properties.

Carboxylated nanocellulose for wound healing applications - Increase of washing efficiency after chemical pre-treatment and stability of homogenized gels over 10 months

To commercialize a biomedical product as a medical device, reproducibility of production and time-stability are important parameters. Studies of reproducibility are lacking in the literature. Additionally, chemical pre-treatments of wood fibres to produce highly fibrillated cellulose nanofibrils (CNF) seem to be demanding in terms of production efficiency, being a bottleneck for industrial upscaling. In this study, we evaluated the effect of pH on the dewatering time and washing steps of 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO)-mediated oxidized wood fibres when applying 3.8 mmol NaClO/g cellulose. The results indicate that the method does not affect the carboxylation of the nanocelluloses, and levels of approximately 1390 μmol/g were obtained with good reproducibility. The washing time of a Low-pH sample was reduced to 1/5 of the time required for washing a Control sample. Additionally, the stability of the CNF samples was assessed over 10 months and changes were quantified, the most pronounced were the increase of potential residual fibre aggregates, reduction of viscosity and increase of carboxylic acid content. The cytotoxicity and skin irritation potential were not affected by the detected differences between the Control and Low-pH samples. Importantly, the antibacterial effect of the carboxylated CNFs against S. aureus and P. aeruginosa was confirmed.

An introductory review on advanced multifunctional materials

This review summarizes the applications of some of the advanced materials. It included the synthesis of several nanoparticles such as metal oxide nanoparticles (e.g., Fe₃O₄, ZnO, ZrOSO₄, MoO_3-x, CuO, AgFeO₂, Co₃O₄, CeO₂, SiO₂, and CuFeO₂); metal hydroxide nanosheets (e.g., Zn₅(OH)₈(NO₃)₂·2H₂O, Zn(OH)(NO₃)·H₂O, and Zn₅(OH)₈(NO₃)₂); metallic nanoparticles (Ag, Au, Pd, and Pt); carbon-based nanomaterials (graphene, graphene oxide (GO), graphitic carbon nitride (g-C₃N₄), and carbon dots (CDs)); biopolymers (cellulose, nanocellulose, TEMPO-oxidized cellulose nanofibers (TOCNFs), and chitosan); organic polymers (e.g. covalent-organic frameworks (COFs)); and hybrid materials (e.g. metal-organic frameworks (MOFs)). Most of these materials were applied in several fields such as environmental-based technologies (e.g., water remediation, air purification, gas storage), energy (production of hydrogen, dimethyl ether, solar cells, and supercapacitors), and biomedical sectors (sensing, biosensing, cancer therapy, and drug delivery). They can be used as efficient adsorbents and catalysts to remove emerging contaminants e.g., inorganic (i.e., heavy metals) and organic (e.g., dyes, antibiotics, pesticides, and oils in water via adsorption. They can be also used as catalysts for catalytic degradation reactions such as redox reactions of pollutants. They can be used as filters for air purification by capturing carbon dioxide (CO₂) and volatile organic compounds (VOCs). They can be used for hydrogen production via water splitting, alcohol oxidation, and hydrolysis of NaBH₄. Nanomedicine for some of these materials was also included being an effective agent as an antibacterial, nanocarrier for drug delivery, and probe for biosensing.

A quaternized chitosan and carboxylated cellulose nanofiber-based sponge with a microchannel structure for rapid hemostasis and wound healing

A hemostatic sponge should perform rapid hemostasis and exhibit antibacterial properties, whilst being non-toxic, breathable, and degradable. This study prepared a hemostatic sponge (CQTC) with microchannels, specifically a microchannel structure based on quaternized chitosan (QCS) and carboxylated cellulose nanofibers (CCNF) obtained by using tannic acid and Cu²⁺ complex (crosslinking agent). The sponge had low density and high porosity, while being degradable. The combination of microchannels and three-dimensional porous structure of CQTC leads to excellent liquid absorption and hemostasis ability, based on a liquid absorption rate test and in vitro hemostasis experiment. In addition, CQTC exhibited excellent antibacterial activity against both gram-negative and gram-positive bacteria, and it promoted wound healing. In conclusion, this porous and microchannel hemostatic sponge has broad application prospects as a clinical wound hemostatic material.

Gene-Expression Analysis of Human Fibroblasts Affected by 3D-Printed Carboxylated Nanocellulose Constructs

Three-dimensional (3D) printing has emerged as a highly valuable tool to manufacture porous constructs. This has major advantages in, for example, tissue engineering, in which 3D scaffolds provide a microenvironment with adequate porosity for cell growth and migration as a simulation of tissue regeneration. In this study, we assessed the suitability of three cellulose nanofibrils (CNF) that were obtained through 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO)-mediated oxidation. The CNFs were obtained by applying three levels of carboxylation, i.e., 2.5, 3.8, and 6.0 mmol sodium hypochlorite (NaClO) per gram of cellulose. The CNFs exhibited different nanofibrillation levels, affecting the corresponding viscosity and 3D printability of the CNF gels (0.6 wt%). The scaffolds were manufactured by micro-extrusion and the nanomechanical properties were assessed with nanoindentation. Importantly, fibroblasts were grown on the scaffolds and the expression levels of the marker genes, which are relevant for wound healing and proliferation, were assessed in order to reveal the effect of the 3D-scaffold microenvironment of the cells.

Neem extract-blended nanocellulose derived from jackfruit peel for antibacterial packagings

The use of jackfruit peel as a source for natural and fully biodegradable "nanocellulose" (NC) for the production of bioplastics with Azadirachta indica (A. indica) extracts and polyethylene glycol (PEG) for the antibacterial properties is investigated. The characterization of the biocomposite using FT-IR and WXRD was reported. The physicochemical properties including thickness, moisture content, water holding capacity, swelling, porosity, and biodegradability in soil were investigated. The incorporation of A. indica extract revealed an increased shelf life due to the strong antibacterial activity, and these biocomposites were degraded in soil within 60 days after the end use without any harm to the environment. Jackfruit-derived nanocellulose film blended with A. indica extract exhibited strong antibacterial activity against gram-positive and gram-negative food spoilage bacteria. Disc diffusion assay, live/dead assay, and CFU analysis confirmed the antibacterial property of the synthesized film. Moreover, the films clearly prevented the biofilm formation in bacteria. Thus, the developed bioplastics can be utilized as appropriate substitutes to food packaging materials and also for biomedical applications such as wound dressings.

Nanocelluloses - Nanotoxicology, Safety Aspects and 3D Bioprinting

Nanocelluloses have good rheological properties that facilitate the extrusion of nanocellulose gels in micro-extrusion systems. It is considered a highly relevant characteristic that makes it possible to use nanocellulose as an ink component for 3D bioprinting purposes. The nanocelluloses assessed in this book chapter include wood nanocellulose (WNC), bacterial nanocellulose (BNC), and tunicate nanocellulose (TNC), which are often assumed to be non-toxic. Depending on various chemical and mechanical processes, both cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) can be obtained from the three mentioned nanocelluloses (WNC, BNC, and TNC). Pre/post-treatment processes (chemical and mechanical) cause modifications regarding surface chemistry and nano-morphology. Hence, it is essential to understand whether physicochemical properties may affect the toxicological profile of nanocelluloses. In this book chapter, we provide an overview of nanotoxicology and safety aspects associated with nanocelluloses. Relevant regulatory requirements are considered. We also discuss hazard assessment strategies based on tiered approaches for safety testing, which can be applied in the early stages of the innovation process. Ensuring the safe development of nanocellulose-based 3D bioprinting products will enable full market use of these sustainable resources throughout their life cycle.

Cellulose-Based Nanomaterials Advance Biomedicine: A Review

There are various biomaterials, but none fulfills all requirements. Cellulose biopolymers have advanced biomedicine to satisfy high market demand and circumvent many ecological concerns. This review aims to present an overview of cellulose knowledge and technical biomedical applications such as antibacterial agents, antifouling, wound healing, drug delivery, tissue engineering, and bone regeneration. It includes an extensive bibliography of recent research findings from fundamental and applied investigations. Cellulose-based materials are tailorable to obtain suitable chemical, mechanical, and physical properties required for biomedical applications. The chemical structure of cellulose allows modifications and simple conjugation with several materials, including nanoparticles, without tedious efforts. They render the applications cheap, biocompatible, biodegradable, and easy to shape and process.

Genotoxicity of Three Micro/Nanocelluloses with Different Physicochemical Characteristics in MG-63 and V79 Cells

(1) Background: Nanocellulose is an innovative engineered nanomaterial with an enormous potential for use in a wide array of industrial and biomedical applications and with fast growing economic value. The expanding production of nanocellulose is leading to an increased human exposure, raising concerns about their potential health effects. This study was aimed at assessing the potential toxic and genotoxic effects of different nanocelluloses in two mammalian cell lines; (2) Methods: Two micro/nanocelluloses, produced with a TEMPO oxidation pre-treatment (CNFs) and an enzymatic pre-treatment (CMFs), and cellulose nanocrystals (CNCs) were tested in osteoblastic-like human cells (MG-63) and Chinese hamster lung fibroblasts (V79) using the MTT and clonogenic assays to analyse cytotoxicity, and the micronucleus assay to test genotoxicity; (3) Results: cytotoxicity was observed by the clonogenic assay in V79 cells, particularly for CNCs, but not by the MTT assay; CNF induced micronuclei in both cell lines and nucleoplasmic bridges in MG-63 cells; CMF and CNC induced micronuclei and nucleoplasmic bridges in MG-63 cells, but not in V79 cells; (4) Conclusions: All nanocelluloses revealed cytotoxicity and genotoxicity, although at different concentrations, that may be related to their physicochemical differences and availability for cell uptake, and to differences in the DNA damage response of the cell model.

Detection of Human Neutrophil Elastase by Fluorescent Peptide Sensors Conjugated to TEMPO-Oxidized Nanofibrillated Cellulose

Peptide–cellulose conjugates designed for use as optical protease sensors have gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with chronic illnesses, necessitating optimal biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Here, we examine a tripeptide, fluorogenic elastase biosensor attached to TEMPO-oxidized nanofibrillated cellulose via a polyethylene glycol linker. The synthetic conjugate was found to be active in the presence of human neutrophil elastase at levels comparable to other cellulose-based biosensors. Computational models examined the relationship of the sensor molecule to the transducer surface. The results illustrate differences in two crystallite transducer surfaces ((110) vs. (1−10)) and reveal preferred orientations of the sensor. Finally, a determination of the relative (110) vs. (1−10) orientations of crystals extracted from cotton demonstrates a preference for the (1−10) conformer. This model study potentiates the HNE sensor results for enhanced sensor activity design.

Nanocellulose-Based Biomedical Scaffolds in Future Bioeconomy: A Techno-Legal Assessment of the State-of-the-Art

Nanocellulose is a broader term used for nano-scaled cellulosic crystal and/or fibrils of plant or animal origin. Where bacterial nanocellulose was immediately accepted in biomedicine due to its “cleaner” nature, the plant-based nanocellulose has seen several roadblocks. This manuscript assesses the technological aspects (chemistry of cellulose, nanocellulose producing methods, its purity, and biological properties including toxicity and suggested applications in final drug formulation) along with legal aspects in REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) regulation by the European Union, EMA (European Medicine Agency). The botanical biomass processing methods leading to the nanoscale impurity (lignin and others) on nanocellulose surface, along with surface modification with harsh acid treatments are found to be two major sources of “impurity” in botanical biomass derived nanocellulose. The status of nanocellulose under the light of REACH regulation along with EMA has been covered. The provided information can be directly used by material and biomedical scientists while developing new nanocellulose production strategies as well as formulation design for European markets.

Challenges and recent trends with the development of hydrogel fiber for biomedical applications

Hydrogel is the most emblematic soft material which possesses significantly tunable and programmable characteristics. Polymer hydrogels possess significant advantages including, biocompatible, simple, reliable and low cost. Therefore, research on the development of hydrogel for biomedical applications has been grown intensely. However, hydrogel development is challenging and required significant effort before the application at an industrial scale. Therefore, the current work focused on evaluating recent trends and issues with hydrogel development for biomedical applications. In addition, the hydrogel's development methodology, physicochemical properties, and biomedical applications are evaluated and benchmarked against the reported literature. Later, biomedical applications of the nano-cellulose-based hydrogel are considered and critically discussed. Based on a detailed review, it has been found that the surface energy, intermolecular interactions, and interactions of hydrogel adhesion forces are major challenges that contribute to the development of hydrogel. In addition, compared to other hydrogels, nanocellulose hydrogels demonstrated higher potential for drug delivery, 3D cell culture, diagnostics, tissue engineering, tissue therapies and gene therapies. Overall, nanocellulose hydrogel has the potential for commercialization for different biomedical applications.

3D-Printed Products for Topical Skin Applications: From Personalized Dressings to Drug Delivery

3D printing has been widely used for the personalization of therapies and on-demand production of complex pharmaceutical forms. Recently, 3D printing has been explored as a tool for the development of topical dosage forms and wound dressings. Thus, this review aims to present advances related to the use of 3D printing for the development of pharmaceutical and biomedical products for topical skin applications, covering plain dressing and products for the delivery of active ingredients to the skin. Based on the data acquired, the important growth in the number of publications over the last years confirms its interest. The semisolid extrusion technique has been the most reported one, probably because it allows the use of a broad range of polymers, creating the most diverse therapeutic approaches. 3D printing has been an excellent field for customizing dressings, according to individual needs. Studies discussed here imply the use of metals, nanoparticles, drugs, natural compounds and proteins and peptides for the treatment of wound healing, acne, pain relief, and anti-wrinkle, among others. The confluence of 3D printing and topical applications has undeniable advantages, and we would like to encourage the research groups to explore this field to improve the patient's life quality, adherence and treatment efficacy.

Antimicrobial and antihemolytic properties of a CNF/AgNP-chitosan film: A potential wound dressing material

Cellulose nanofibers (CNFs), chitosan, and silver nanoparticles (AgNPs) are widely used to enhance the active functions and antibacterial properties of wound dressings. This study was conducted to prepare CNF/AgNP-chitosan using a straight incorporation method and to assess its antimicrobial activity. CNFs were isolated from oil palm empty fruit bunches (OPEFBs) using the pulping method and acid hydrolysis. AgNPs were synthesized using a green synthesis method. The wound dressing was produced by mixing a 10% CNF solution in LiCl/DMAc and AgNP-chitosan in a glass plate with various ratios of CNF/AgNP-chitosan, i.e., 100:0, 80:20, 60:40, and 50:50. UV-visible and TEM analyses were conducted to confirm the formation of AgNPs and CNFs at the nanoscale. The results showed particles with an absorption wavelength of 435 nm and spherical shapes. Based on the calculation using ImageJ software, the diameters of CNFs were approximately 50 nm, and the lengths were several micrometers. FTIR was used to analyze the chemical bonding of AgNP-chitosan and the incorporated AgNP-chitosan in CNFs. Based on the XRD analysis, the presence of AgNPs did not affect the crystallinity of the CNFs. SEM images showed that the addition of AgNPs resulted in the stretching of CNF pores on the pads. Thermal degradation of the film increased with the addition of AgNP-chitosan by up to 40%. Antimicrobial tests and hemocompatibility tests showed that the formed CNF/AgNP-chitosan film successfully inhibited bacterial growth and was classified as a nonhemolytic material; thus, its potential as a wound dressing should be further studied.

Oxygenated Nanocellulose-A Material Platform for Antibacterial Wound Dressing Devices

Both carboxylated cellulose nanofibrils (CNF) and dissolved oxygen (DO) have been reported to possess antibacterial properties. However, the combination for use as wound dressings against biofilm infections in chronic wounds is less known. The present study reports the development of oxygenated CNF dispersions that exhibit strong antibacterial effect. Carboxylated CNF dispersions with different oxidation levels were oxygenated by the OXY BIO System and tested for antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus. The results reveal that the higher oxidation level of the CNFs, the better antibacterial effect. Scanning electron microscopy of bacterial biofilms revealed that a potential mechanism of action of the CNFs is the formation of a network surrounding and entrapping the bacteria. This effect is further potentiated by the oxygenation process. A CNF sample (concentration 0.6 wt %) that was oxygenated to a DO level of 46.4 mg/L demonstrated a strong antibacterial effect against S. aureus in vivo using a mouse model of surgical site infection. The oxygenated CNF dispersion reduced the bacterial survival by 71%, after 24 h treatment. The potent antibacterial effect indicates that oxygenated nanocellulose is a promising material for antibacterial wound dressings.

Characterization and Antibacterial Properties of Autoclaved Carboxylated Wood Nanocellulose

Cellulose nanofibrils (CNFs) were obtained by applying a chemical pretreatment consisting of autoclaving the pulp fibers in sodium hydroxide, combined with 2,2,6,6-tetramethylpiperidinyl-1-oxyl-mediated oxidation. Three levels of sodium hypochlorite were applied (2.5, 3.8, and 6.0 mmol/g) to obtain CNF qualities (CNF_2.5, CNF_3.8, and CNF_6.0) with varying content of carboxyl groups, that is, 1036, 1285, and 1593 μmol/g cellulose. The cytotoxicity and skin irritation potential (indirect tests) of the CNFs were determined according to standardized in vitro testing for medical devices. We here demonstrate that autoclaving (121 °C, 20 min), which was used to sterilize the gels, caused a modification of the CNF characteristics. This was confirmed by a reduction in the viscosity of the gels, a morphological change of the nanofibrils, by an increase of the ultraviolet-visible absorbance maxima at 250 nm, reduction of the absolute zeta potential, and by an increase in aldehyde content and reducing sugars after autoclaving. Fourier-transform infrared spectroscopy and wide-angle X-ray scattering complemented an extensive characterization of the CNF gels, before and after autoclaving. The antibacterial properties of autoclaved carboxylated CNFs were demonstrated in vitro (bacterial survival and swimming assays) on Pseudomonas aeruginosa and Staphylococcus aureus. Importantly, a mouse in vivo surgical-site infection model on S. aureus revealed that CNF_3.8 showed pronounced antibacterial effect and performed as good as the antiseptic Prontosan wound gel.

The Insights of Microbes' Roles in Wound Healing: A Comprehensive Review

A diverse range of normal flora populates the human skin and numbers are relatively different between individuals and parts of the skin. Humans and normal flora have formed a symbiotic relationship over a period of time. With numerous disease processes, the interaction between the host and normal flora can be interrupted. Unlike normal wound healing, which is complex and crucial to sustaining the skin’s physical barrier, chronic wounds, especially in diabetes, are wounds that fail to heal in a timely manner. The conditions become favorable for microbes to colonize and establish infections within the skin. These include secretions of various kinds of molecules, substances or even trigger the immune system to attack other cells required for wound healing. Additionally, the healing process can be slowed down by prolonging the inflammatory phase and delaying the wound repair process, which causes further destruction to the tissue. Antibiotics and wound dressings become the targeted therapy to treat chronic wounds. Though healing rates are improved, prolonged usage of these treatments could become ineffective or microbes may become resistant to the treatments. Considering all these factors, more studies are needed to comprehensively elucidate the role of human skin normal flora at the cellular and molecular level in a chronic injury. This article will review wound healing physiology and discuss the role of normal flora in the skin and chronic wounds.

Bioaerogels: Promising Nanostructured Materials in Fluid Management, Healing and Regeneration of Wounds

Wounds affect one's quality of life and should be managed on a patient-specific approach, based on the particular healing phase and wound condition. During wound healing, exudate is produced as a natural response towards healing. However, excessive production can be detrimental, representing a challenge for wound management. The design and development of new healing devices and therapeutics with improved performance is a constant demand from the healthcare services. Aerogels can combine high porosity and low density with the adequate fluid interaction and drug loading capacity, to establish hemostasis and promote the healing and regeneration of exudative and chronic wounds. Bio-based aerogels, i.e., those produced from natural polymers, are particularly attractive since they encompass their intrinsic chemical properties and the physical features of their nanostructure. In this work, the emerging research on aerogels for wound treatment is reviewed for the first time. The current scenario and the opportunities provided by aerogels in the form of films, membranes and particles are identified to face current unmet demands in fluid managing and wound healing and regeneration.

Recent Progress on Nanocellulose Aerogels: Preparation, Modification, Composite Fabrication, Applications

The rapid development of modern industry and excessive consumption of petroleum-based polymers have triggered a double crisis presenting a shortage of nonrenewable resources and environmental pollution. However, this has provided an opportunity to stimulate researchers to harness native biobased materials for novel advanced materials and applications. Nanocellulose-based aerogels, using abundant and sustainable cellulose as raw material, present a third-generation of aerogels that combine traditional aerogels with high porosity and large specific surface area, as well as the excellent properties of cellulose itself. Currently, nanocellulose aerogels provide a highly attention-catching platform for a wide range of functional applications in various fields, e.g., adsorption, separation, energy storage, thermal insulation, electromagnetic interference shielding, and biomedical applications. Here, the preparation methods, modification strategies, composite fabrications, and further applications of nanocellulose aerogels are summarized, with additional discussions regarding the prospects and potential challenges in future development.

Cationic Cross-Linked Nanocellulose-Based Matrices for the Growth and Recovery of Intestinal Organoids

Highly carboxylated nanocellulose fibers can be functionalized with cell adhesive peptides and cationic cross-linked to form matrices for a three-dimensional (3D) cell culture. It is hypothesized that nanocellulose hydrogels cross-linked with divalent cations can provide the required biochemical and mechanical properties for intestinal organoid growth and recovery. Nanocellulose hydrogels are produced by TEMPO- and TEMPO-periodate-mediated oxidation and functionalized with RGD peptides. Mechanical properties are measured by rheology and optical properties quantified by UV-vis spectroscopy. Cellulosic matrices are cross-linked with Ca²⁺ and Mg²⁺ and intestinal organoids cultured for 4 days. The organoids are recovered for passaging and RNA extraction. TEMPO-periodate-oxidized nanocellulose fibers form functionalized hydrogels and support the growth of intestinal organoids. The highly transparent cellulosic matrix requires 4 times more Mg²⁺ than Ca²⁺ ions to reach the targeted stiffness. Organoids cultured in nanocellulose maintained a major living area for up to 4 days. Cell clusters recovered from magnesium-cross-linked hydrogels can be passaged, and their extracted RNA is intact. Cationic cross-linked nanocellulose hydrogels are promising alternative plant-based matrices for a 3D cell culture systems.

Clinical Translational Potential in Skin Wound Regeneration for Adipose-Derived, Blood-Derived, and Cellulose Materials: Cells, Exosomes, and Hydrogels

Acute and chronic skin wounds due to burns, pressure injuries, and trauma represent a substantial challenge to healthcare delivery with particular impacts on geriatric, paraplegic, and quadriplegic demographics worldwide. Nevertheless, the current standard of care relies extensively on preventive measures to mitigate pressure injury, surgical debridement, skin flap procedures, and negative pressure wound vacuum measures. This article highlights the potential of adipose-, blood-, and cellulose-derived products (cells, decellularized matrices and scaffolds, and exosome and secretome factors) as a means to address this unmet medical need. The current status of this research area is evaluated and discussed in the context of promising avenues for future discovery.

In Vitro Biological Impact of Nanocellulose Fibers on Human Gut Bacteria and Gastrointestinal Cells

Wood-derived nanofibrillated cellulose (NFC) has long been recognized as a valuable nanomaterial for food-related applications. However, the safety of NFC cannot be predicted just from the chemical nature of cellulose, and there is a need to establish the effect of the nanofibers on the gastrointestinal tract, to reassure the safe use of NFC in food-related products. The present work selected the intestinal cells Caco-2 and the gut bacteria Escherichia coli and Lactobacillus reuteri to evaluate the in vitro biological response to NFC. NFC materials with different surface modifications (carboxymethylation, hydroxypropyltrimethylammonium substitution, phosphorylation and sulfoethylation) and unmodified NFC were investigated. The materials were characterized in terms of surface functional group content, fiber morphology, zeta potential and degree of crystallinity. The Caco-2 cell response to the materials was evaluated by assessing metabolic activity and cell membrane integrity. The effects of the NFC materials on the model bacteria were evaluated by measuring bacterial growth (optical density at 600 nm) and by determining colony forming units counts after NFC exposure. Results showed no sign of cytotoxicity in Caco-2 cells exposed to the NFC materials, and NFC surface functionalization did not impact the cell response. Interestingly, a bacteriostatic effect on E. coli was observed while the materials did not affect the growth of L. reuteri. The present findings are foreseen to contribute to increase the knowledge about the potential oral toxicity of NFC and, in turn, add to the development of safe NFC-based food products.

Gelatin sponge functionalized with gold/silver clusters for antibacterial application

Pathogenic bacterial infection, especially in the wound, may threaten human health. Developing new antibacterial materials for wound healing is still urgent. Metal nanoclusters have been explored as a novel antibacterial agent. Herein, biomolecule gelatin was chosen as a substrate and functionalized with gold/silver clusters for bacterial killing. Through a simple amidation reaction, gold/silver clusters were successfully conjugated in a gelatin substrate to obtain a Au/Ag@gelatin sponge. The presence of gold/silver clusters modified the porous structure of the gelatin. Thus, the water absorption and water retention of the Au/Ag@gelatin sponge were enhanced. More importantly, the gold/silver clusters show aggregation-enhanced emission and strong reactive oxygen generation, that endow the Au/Ag@gelatin sponge with a good antibacterial property. The good physical performance and favorable bactericidal activity of the Au/Ag@gelatin sponge suggest its potential for application as a wound dressing.

Cellulose Nanofibers and Other Biopolymers for Biomedical Applications. A Review

Biopolymers are materials synthesised or derived from natural sources, such as plants, animals, microorganisms or any other living organism. The use of these polymers has grown significantly in recent years as industry shifts away from unsustainable fossil fuel resources and looks towards a softer and more sustainable environmental approach. This review article covers the main classes of biopolymers: Polysaccharides, proteins, microbial-derived and lignin. In addition, an overview of the leading biomedical applications of biopolymers is also provided, which includes tissue engineering, medical implants, wound dressings, and the delivery of bioactive molecules. The future clinical applications of biopolymers are vast, due to their inherent biocompatibility, biodegradability and low immunogenicity. All properties which their synthetic counterparts do not share.

Nanocellulose-Based Inks-Effect of Alginate Content on the Water Absorption of 3D Printed Constructs

2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) oxidized cellulose nanofibrils (CNF) were used as ink for three-dimensional (3D) printing of porous structures with potential as wound dressings. Alginate (10, 20, 30 and 40 wt%) was incorporated into the formulation to facilitate the ionic cross-linking with calcium chloride (CaCl2). The effect of two different concentrations of CaCl2 (50 and 100 mM) was studied. The 3D printed hydrogels were freeze-dried to produce aerogels which were tested for water absorption. Scanning Electronic Microscopy (SEM) pictures demonstrated that the higher the concentration of the cross-linker the higher the definition of the printed tracks. CNF-based aerogels showed a remarkable water absorption capability. Although the incorporation of alginate and the cross-linking with CaCl2 led to shrinkage of the 3D printed constructs, the approach yielded suitable porous structures for water and moisture absorption. It is concluded that the 3D printed biocomposite structures developed in this study have characteristics that are promising for wound dressings devices.

Cellulose Nanofibril Formulations Incorporating a Low-Molecular-Weight Alginate Oligosaccharide Modify Bacterial Biofilm Development

Cellulose nanofibrils (CNFs) from wood pulp are a renewable material possessing advantages for biomedical applications because of their customizable porosity, mechanical strength, translucency, and environmental biodegradability. Here, we investigated the growth of multispecies wound biofilms on CNF formulated as aerogels and films incorporating the low-molecular-weight alginate oligosaccharide OligoG CF-5/20 to evaluate their structural and antimicrobial properties. Overnight microbial cultures were adjusted to 2.8 × 10⁹ colony-forming units (cfu) mL^-1 in Mueller Hinton broth and growth rates of Pseudomonas aeruginosa PAO1 and Staphylococcus aureus 1061A monitored for 24 h in CNF dispersions sterilized by γ-irradiation. Two CNF formulations were prepared (20 g m^-2) with CNF as air-dried films or freeze-dried aerogels, with or without incorporation of an antimicrobial alginate oligosaccharide (OligoG CF-5/20) as a surface coating or bionanocomposite, respectively. The materials were structurally characterized by scanning electron microscopy (SEM) and laser profilometry (LP). The antimicrobial properties of the formulations were assessed using single- and mixed-species biofilms grown on the materials and analyzed using LIVE/DEAD staining with confocal laser scanning microscopy (CLSM) and COMSTAT software. OligoG-CNF suspensions significantly decreased the growth of both bacterial strains at OligoG concentrations >2.58% (P < 0.05). SEM showed that aerogel-OligoG bionanocomposite formulations had a more open three-dimensional structure, whereas LP showed that film formulations coated with OligoG were significantly smoother than untreated films or films incorporating PEG400 as a plasticizer (P < 0.05). CLSM of biofilms grown on films incorporating OligoG demonstrated altered biofilm architecture, with reduced biomass and decreased cell viability. The OligoG-CNF formulations as aerogels or films both inhibited pyocyanin production (P < 0.05). These novel CNF formulations or bionanocomposites were able to modify bacterial growth, biofilm development, and virulence factor production in vitro. These data support the potential of OligoG and CNF bionanocomposites for use in biomedical applications where prevention of infection or biofilm growth is required.

Modifications of microcrystalline cellulose (MCC), nanofibrillated cellulose (NFC), and nanocrystalline cellulose (NCC) for antimicrobial and wound healing applications

Recently, great attention has been paid to nano-composites of cellulose, due to their unique structure as a most abundant natural polymer with having exceptional properties such as renewable, biodegradable and high specific tensile strength, aspect ratio, and Young’s modulus. Prominent cellulose is naturally present in plant lignocellulosic biomass as a biocomposite made of cellulose, hemi-celluloses, lignin, etc. In addition, it can be extracted from other natural sources including bacteria, algae, and sea animals. Microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), and nanofibrillated cellulose (NFC) is an emerging renewable nanomaterial that has various applications, such as food, paper production, industrial and pharmaceutical biomaterials. The surface modification on NCC can improves its disperse ability in different solvents and its utilization in protein immobilization, tissue engineering, drug delivery, and inorganic reaction template. Therefore, based on recent studies, this review illustrated considerable progresses with addressing medicinal properties involving antimicrobial and biocompatibility of nano-cellulose (NC) in the case of wound healing.

Engineering nanocellulose hydrogels for biomedical applications

Nanocellulose hydrogels are highly hydrated porous cellulosic soft materials with good mechanical properties. These cellulose-based gels can be produced from bacterial or plant cellulose nanofibrils, which are hydrophilic, renewable, biodegradable and biocompatible. Nanocellulose, whether fibrils (CNF), crystals (CNC) or bacterial (BNC), has a high aspect ratio and surface area, and can be chemically modified with functional groups or by grafting biomolecules. Cellulose functionalization provides enhanced physical and chemical properties and control of biological interactions, tailoring its hydrogels for specific applications. Here, we critically review nanocellulose hydrogels for biomedical applications. Nanocellulose hydrogels have been demonstrated for 3D cell culture, mimicking the extracellular matrix (ECM) properties with low cytotoxicity. For wound dressing and cartilage repair, nanocellulose gels promote cell regeneration while providing the required mechanical properties for tissue engineering scaffolds. The encapsulation of therapeutics within nanocellulose allows the targeted delivery of drugs. Currently, cellulose crosslinking to peptides and proteins enables a new generation of low cost and renewable smart materials used in diagnostics. Last, the organized mesh of fibres contained in hydrogels drives applications in separation of biomolecules and cells. Nanocellulose hydrogels have emerged as a highly engineerable platform for multiple biomedical applications, providing renewable and performant solutions to life sciences.

Versatile Application of Nanocellulose: From Industry to Skin Tissue Engineering and Wound Healing

Nanocellulose is cellulose in the form of nanostructures, i.e., features not exceeding 100 nm at least in one dimension. These nanostructures include nanofibrils, found in bacterial cellulose; nanofibers, present particularly in electrospun matrices; and nanowhiskers, nanocrystals, nanorods, and nanoballs. These structures can be further assembled into bigger two-dimensional (2D) and three-dimensional (3D) nano-, micro-, and macro-structures, such as nanoplatelets, membranes, films, microparticles, and porous macroscopic matrices. There are four main sources of nanocellulose: bacteria (Gluconacetobacter), plants (trees, shrubs, herbs), algae (Cladophora), and animals (Tunicata). Nanocellulose has emerged for a wide range of industrial, technology, and biomedical applications, namely for adsorption, ultrafiltration, packaging, conservation of historical artifacts, thermal insulation and fire retardation, energy extraction and storage, acoustics, sensorics, controlled drug delivery, and particularly for tissue engineering. Nanocellulose is promising for use in scaffolds for engineering of blood vessels, neural tissue, bone, cartilage, liver, adipose tissue, urethra and dura mater, for repairing connective tissue and congenital heart defects, and for constructing contact lenses and protective barriers. This review is focused on applications of nanocellulose in skin tissue engineering and wound healing as a scaffold for cell growth, for delivering cells into wounds, and as a material for advanced wound dressings coupled with drug delivery, transparency and sensorics. Potential cytotoxicity and immunogenicity of nanocellulose are also discussed.

Synthesis and Characterization of Cellulose Nanofibril-Reinforced Polyurethane Foam

In this study, traditional polyol was partially replaced with green, environmentally friendly cellulose nanofibrils (CNF). The effects of CNF on the performance of CNF-reinforced polyurethane foam nanocomposites were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and a compression test. The results showed that the introduction of CNF into the polyurethane matrix not only created stronger urethane bonding between the hydroxyl groups in the cellulose chain and isocyanate groups in polymethylene polyphenylisocyanate, but also developed an additional filler⁻matrix interaction between CNF and polyurethane. With the increase of the CNF replacement ratio, a higher glass transition temperature was obtained, and a higher amount of char residue was generated. In addition, an increase of up to 18-fold in compressive strength was achieved for CNF-PUF (polyurethane foam) nanocomposites with a 40% CNF replacement ratio. CNF has proved to be a promising substitute for traditional polyols in the preparation of polyurethane foams. This study provides an interesting method to synthesize highly green bio-oriented polyurethane foams.

On importance of impurities, potential leachables and extractables in algal nanocellulose for biomedical use

Nanocellulose-based biomaterials for biomedical and pharmaceutical applications have been extensively explored. However, studies on different levels of impurities in the nanocellulose and their potential risks are lacking. This article is the most comprehensive to date survey of the importance and characterization of possible leachables and extractables in nanocellulose for biomedical use. In particular, the (1,3)-β-d-glucan interference in endotoxin detection in algal nanocellulose was addressed. Potential lipophilic and hydrophilic leachables, toxic heavy metals, and microbial contaminants are also monitored. As a model system, nanocellulose from Cladophora sp. algae is investigated. The leachable (1,3)-β-d-glucan and endotoxin, which possess strong immunogenic potential, from the cellulose were minimized to clinically insignificant levels of 4.7μg/g and 2.5EU/g, respectively. The levels of various impurities in the Cladophora cellulose are acceptable for future biomedical applications. The presented approach could be considered as a guideline for other types of nanocellulose.