Spray-dried nanofibrillar cellulose microparticles for sustained drug release

Toward a greener multifunctional pharmaceutical excipient: in vivo safety evaluation of nanofibrillated cellulose from tobacco stalk

Tobacco stalk is a cellulose-rich material and a sustainable alternative to be applied as a plant-based nanofibrillated cellulose (NFC) source. NFC use has garnered attention in the development of oral pharmaceutical forms, despite concerns about its safety due to the adverse effects of nicotine on health. Therefore, we aimed at establishing the safety of NFC derived from tobacco stalk for its potential use as a novel pharmaceutical excipient, exploring its potential functions for tablet production. We conducted acute and subchronic oral toxicity tests in adult female Wistar rats. Initially, individual animals received sequential doses (175-5,000 mg·kg-1) for 24 hours followed by a careful observation of any toxic effects. Subsequently, 20 rats were divided into four groups for a subchronic assay, evaluating toxicity signs, body weight changes, hematological, biochemical, and histopathological parameters. No deaths or other clinical toxicity signs were observed in either the acute or the subchronic assays. We noticed a significant reduction in body weight gain (p < 0.05) after 14 days. We found statistical differences for hematological and biochemical parameters, unrelated to dosage. There were no observed toxic effects, and tobacco stalk ingestion did not adversely affect organ morphology in the histopathological evaluation. The oral administration of NFC at 5,000 mg·kg-1 per day for 28 days was well-tolerated by treated rats, with no reported deaths. In conclusion, NFC derived from tobacco stalk has shown to be a sustainable and safe alternative for use as an excipient at experimental doses, demonstrating compatibility with its proposed applications.

Nanocellulose, the Green Biopolymer Trending in Pharmaceuticals: A Patent Review

The use of nanocellulose in pharmaceutics is a trend that has emerged in recent years. Its inherently good mechanical properties, compared to different materials, such as its high tensile strength, high elastic modulus and high porosity, as well as its renewability and biodegradability are driving nanocellulose's industrial use and innovations. In this sense, this study aims to conduct a search of patents from 2011 to 2023, involving applications of nanocellulose in pharmaceuticals. A patent search was carried out, employing three different patent databases: Patentscope from World Intellectual Property Organization (WIPO); Espacenet; and LENS.ORG. Patents were separated into two main groups, (i) nanocellulose (NC) comprising all its variations and (ii) bacterial nanocellulose (BNC), and classified into five major areas, according to their application. A total of 215 documents was retrieved, of which 179 were referred to the NC group and 36 to the BNC group. The NC group depicted 49.7%, 15.6%, 16.2%, 8.9% and 9.5% of patents as belonging to design and manufacturing, cell culture systems, drug delivery, wound healing and tissue engineering clusters, respectively. The BNC group classified 44.5% of patents as design and manufacturing and 30.6% as drug delivery, as well as 5.6% and 19.4% of patents as wound healing and tissue engineering, respectively. In conclusion, this work compiled and classified patents addressing exclusively the use of nanocellulose in pharmaceuticals, providing information on its current status and trending advancements, considering environmental responsibility and sustainability in materials and products development for a greener upcoming future.

Health and toxicological effects of nanocellulose when used as a food ingredient: A review

The use of nanocellulose (NC) has increased significantly in the food industry, as subtypes such as cellulose nanofibrils (CNF) or bacterial cellulose (BC) have been demonstrated to be a source of insoluble fiber with important benefits for human health. Despite these advantages, and due to its nanoscale size, NC must be assessed from a safety perspective that considers its exposure, fate, and biological effects in order to help more accurately estimate its potential hazards. The exposure routes of humans to NC include (i) ingestion during consumption of foods that contain cellulose as a food ingredient or (ii) contact of food with cellulose-containing materials, such as its packaging. That is why it is important to understand the potentially toxic effects that nanomaterials can have on human health, understanding that the different types of NC behave differently in terms of their ingestion, absorption, distribution, metabolism, and excretion. By analysing both in vitro and in vivo studies, the purpose of this paper is to present the most recent findings on the different types of NC and their safety when used in food. In addition, it provides an overview of relevant studies into NC and its health benefits when used as a food additive.

Biological Potential and Bioaccessibility of Encapsulated Curcumin into Cetyltrimethylammonium Bromide Modified Cellulose Nanocrystals

Curcumin is a natural phenolic compound with important biological functions. Despite its demonstrated efficacy in vitro, curcumin biological activities in vivo are dependent on its bioaccessibility and bioavailability, which have been highlighted as a crucial challenge. Cetyltrimethylammonium bromide-modified cellulose nanocrystals (CNC-CTAB) have been shown to be effective in curcumin encapsulation, as they have the potential to enhance biological outcomes. This study evaluated the biological effects of curcumin encapsulated within CNC-CTAB structures, namely its antioxidant, anti-inflammatory and antimicrobial properties, as well as the release profile under digestion conditions and intestinal permeability. Encapsulated curcumin demonstrated antioxidant and anti-inflammatory properties, effectively reducing reactive oxygen species and cytokine production by intestinal cells. The delivery system exhibited antimicrobial properties against Campylobacter jejuni bacteria, further suggesting its potential in mitigating intestinal inflammation. The system showed the ability to protect curcumin from degradation and facilitate its interaction with the intestinal epithelium, highlighting the potential of CNC-CTAB as carrier to enhance curcumin intestinal biological functions.

Polysaccharide-based nanoassemblies: From synthesis methodologies and industrial applications to future prospects

Polysaccharides, due to their remarkable features, have gained significant prominence in the sustainable production of nanoparticles (NPs). High market demand and minimal production cost, compared to the chemically synthesised NPs, demonstrate a drive towards polysaccharide-based nanoparticles (PSNPs) benign to environment. Various approaches are used for the synthesis of PSNPs including cross-linking, polyelectrolyte complexation, and self-assembly. PSNPs have the potential to replace a wide diversity of chemical-based agents within the food, health, medical and pharmacy sectors. Nevertheless, the considerable challenges associated with optimising the characteristics of PSNPs to meet specific targeting applications are of utmost importance. This review provides a detailed compilation of recent accomplishments in the synthesis of PSNPs, the fundamental principles and critical factors that govern their rational fabrication, as well as various characterisation techniques. Noteworthy, the multiple use of PSNPs in different disciplines such as biomedical, cosmetics agrochemicals, energy storage, water detoxification, and food-related realms, is accounted in detail. Insights into the toxicological impacts of the PSNPs and their possible risks to human health are addressed, and efforts made in terms of PSNPs development and optimising strategies that allow for enhanced delivery are highlighted. Finally, limitations, potential drawbacks, market diffusion, economic viability and future possibilities for PSNPs to achieve widespread commercial use are also discussed.

Development and Characterization of Microparticles with Actinidia arguta Leaves Extract by Spray-Drying: A New Mind-Set Regarding Healthy Compounds for Oral Mucositis

Actinidia arguta leaves have gained notoriety over the past years due to their rich bioactive composition with human pro-healthy effects, particularly in relation to antioxidants. Nevertheless, antioxidants are well known for their chemical instability, making it necessary to develop suitable delivery systems, such as microparticles, to provide protection and ensure a controlled release. The aim of this work was to produce polymeric particles of A. arguta leaves extract by spray-drying that may improve the oral mucositis condition. Microparticles were characterized by size, shape, antioxidant/antiradical activities, swelling capacity, moisture content, and effect on oral cells (TR146 and HSC-3) viability, with the aim to assess their potential application in this oral condition. The results attested the microparticles' spherical morphology and production yields of 41.43% and 36.40%, respectively, for empty and A. arguta leaves extract microparticles. The A. arguta leaves extract microparticles obtained the highest phenolic content (19.29 mg GAE/g) and antioxidant/antiradical activities (FRAP = 81.72 µmol FSE/g; DPPH = 4.90 mg TE/g), being perceived as an increase in moisture content and swelling capacity. No differences were observed between empty and loaded microparticles through FTIR analysis. Furthermore, the exposure to HSC-3 and TR146 did not lead to a viability decrease, attesting their safety for oral administration. Overall, these results highlight the significant potential of A. arguta leaves extract microparticles for applications in the pharmaceutical and nutraceutical industries.

Design of Innovative Biocompatible Cellulose Nanostructures for the Delivery and Sustained Release of Curcumin

Poor aqueous solubility, stability and bioavailability of interesting bioactive compounds is a challenge in the development of bioactive formulations. Cellulose nanostructures are promising and sustainable carriers with unique features that may be used in enabling delivery strategies. In this work, cellulose nanocrystals (CNC) and cellulose nanofibers were investigated as carriers for the delivery of curcumin, a model liposoluble compound. Nanocellulose modification with the surfactant cetyltrimethylammonium bromide (CTAB), tannic acid and decylamine (TADA), and by TEMPO-mediated oxidation were also tested and compared. The carrier materials were characterized in terms of structural properties and surface charge, while the delivery systems were evaluated for their encapsulation and release properties. The release profile was assessed in conditions that mimic the gastric and intestinal fluids, and cytotoxicity studies were performed in intestinal cells to confirm safe application. Modification with CTAB and TADA resulted in high curcumin encapsulation efficiencies of 90 and 99%, respectively. While no curcumin was released from TADA-modified nanocellulose in simulated gastrointestinal conditions, CNC-CTAB allowed for a curcumin-sustained release of ca. 50% over 8 h. Furthermore, the CNC-CTAB delivery system showed no cytotoxic effects on Caco-2 intestinal cells up to 0.125 g/L, meaning that up to this concentration the system is safe to use. Overall, the use of the delivery systems allowed for the reduction in the cytotoxicity associated with higher curcumin concentrations, highlighting the potential of nanocellulose encapsulation systems.

The Use of Corn Stover-Derived Nanocellulose as a Stabilizer of Oil-in-Water Emulsion

Agricultural byproducts such as corn stover are widely available sources for preparation of nanocellulose, which is an emerging green chemical with versatile applications. In this study, corn stover-derived nanocellulose was prepared via bleaching, alkaline treatment, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) oxidation, and ultrasonication. The as-prepared TEMPO-oxidized cellulose nanofibril (TEMPO-CNF) was characterized by transmission electron microscopy, UV-Vis spectrophotometry, rheometry, and zeta potential measurement. Droplet size, phase behavior, and thermodynamic stability of TEMPO-CNF stabilized oil-in-water emulsions were investigated. Results show that TEMPO-CNF with a width of 4 nm, length of 353 nm, and surface charge of 1.48 mmol/g COO^- can be prepared from corn stover. In addition, TEMPO-CNF can be used as an emulsion stabilizer for lemongrass essential oil loaded oil-in-water emulsion. This study is among the first to report that TEMPO-CNF improved the freeze-thaw stability of oil-in-water emulsions stabilized by small molecular weight surfactants (e.g., Tween 80).

Nanocellulose incorporated oleogel matrix for controlled-release of active ingredients in the lower gastrointestinal tract

Controlled release is often preferred for orally administrated bioactive compounds and drugs. In this study, a nanocellulose (NC) incorporated oleogel encapsulation system was developed for controlled release of active agents. 5-Aminosalicylic acid (5-ASA), an anti-inflammatory drug to treat inflammatory bowel diseases, was used as an example core ingredient for demonstrating the efficacy of the system. Oleogels with/without NC incorporation encapsulating 5-ASA were prepared and tested by in vitro digestion study, and 5-ASA released from the matrix was quantified by a novel UV-Vis spectrometric method developed in this study. The oleogel encapsulation system was characterized by assessing the encapsulation efficiency, oxidative stability, gel hardness, microstructure, and thermal stability. Results showed that sorbitan tristearate-induced oleogel system successfully protected 5-ASA during GI digestion. The incorporation of NC solutions with different NC types, concentrations and volumes further modified the release rate. Specifically, the release of 5-ASA in NC incorporated matrix was <6 % in the gastric phase, and ranged between 17.42 % - 38.28 % in the small intestine depending on the added NC type and concentration. Additionally, the incorporation of NC improved physicochemical stability of the gel matrix. The new 5-ASA quantification method developed in this study is simpler and faster compared with currently available methods.

Evaluation of the Effects of Genistein In Vitro as a Chemopreventive Agent for Colorectal Cancer—Strategy to Improve Its Efficiency When Administered Orally

Colorectal Cancer (CRC) ranks third in terms of incidence and second in terms of mortality and prevalence worldwide. In relation to chemotherapy treatment, the most used drug is 5-fluorouracil (5-FU); however, the use of this drug generates various toxic effects at the systemic level. For this reason, new therapeutic strategies are currently being sought that can be used as neoadjuvant or adjuvant treatments. Recent research has shown that natural compounds, such as genistein, have chemotherapeutic and anticancer effects, but the mechanisms of action of genistein and its molecular targets in human colon cells have not been fully elucidated. The results reported in relation to non-malignant cell lines are also unclear, which does not allow evidence of the selectivity that this compound may have. Therefore, in this work, genistein was evaluated in vitro in both cancer cell lines SW480 and SW620 and in the non-malignant cell line HaCaT. The results obtained show that genistein has selectivity for the SW480 and SW620 cell lines. In addition, it inhibits cell viability and has an antiproliferative effect in a dose-dependent manner. Increased production of reactive oxygen species (ROS) was also found, suggesting an association with the cell death process through various mechanisms. Finally, the encapsulation strategy that was proposed made it possible to demonstrate that bacterial nanocellulose (BNC) is capable of protecting genistein from the acidic conditions of gastric fluid and also allows the release of the compound in the colonic fluid. This would allow genistein to act locally in the mucosa of the colon where the first stages of CRC occur.

Pintado M, Fernandes JC, Ramos ÓL. Novel Micro- and Nanocellulose-Based Delivery Systems for Liposoluble Compounds

Poor aqueous solubility of bioactive compounds is becoming a pronounced challenge in the development of bioactive formulations. Numerous liposoluble compounds have very interesting biological activities, but their low water solubility, stability, and bioavailability restrict their applications. To overcome these limitations there is a need to use enabling delivering strategies, which often demand new carrier materials. Cellulose and its micro- and nanostructures are promising carriers with unique features. In this context, this review describes the fast-growing field of micro- and nanocellulose based delivery systems with a focus on the release of liposoluble bioactive compounds. The state of research on this field is reviewed in this article, which also covers the chemistry, preparation, properties, and applications of micro- and nanocellulose based delivery systems. Although there are promising perspectives for introducing these materials into various fields, aspects of safety and toxicity must be revealed and are discussed in this review. The impact of gastrointestinal conditions on the systems and on the bioavailability of the bioactive compounds are also addressed in this review. This article helps to unveil the whole panorama of micro- and nanocellulose as delivery systems for liposoluble compounds, showing that these represent a great promise in a wide range of applications.

Cellulose Nanofibers Improve the Performance of Retrograded Starch/Pectin Microparticles for Colon-Specific Delivery of 5-ASA

Cellulose nanofibers (CNF) were employed as the nanoreinforcement of a retrograded starch/pectin (RS/P) excipient to optimize its colon-specific properties. Although starch retrogradation ranged from 32 to 73%, CNF addition discretely disfavored the RS yield. This result agrees with the finding that in situ CNF reduces the presence of the RS crystallinity pattern. A thermal analysis revealed that the contribution of pectin improves the thermal stability of the RS/CNF mixture. Through a complete factorial design, it was possible to optimize the spray-drying conditions to obtain powders with high yield (57%) and low moisture content (1.2%). The powders observed by Field Emission Gum Scanning Electron Microscopy (FEG-SEM) had 1–10 µm and a circular shape. The developed methodology allowed us to obtain 5-aminosalicilic acid-loaded microparticles with high encapsulation efficiency (16–98%) and drug loading (1.97–26.63%). The presence of CNF in RS/P samples was responsible for decreasing the burst effect of release in simulated gastric and duodenal media, allowing the greatest mass of drug to be targeted to the colon. Considering that spray-drying is a scalable process, widely used by the pharmaceutical industry, the results obtained indicate the potential of these microparticles as raw material for obtaining other dosage forms to deliver 5-ASA to the distal parts of gastrointestinal tract, affected by inflammatory bowel disease.

Development of Bioinspired Functional Chitosan/Cellulose Nanofiber 3D Hydrogel Constructs by 3D Printing for Application in the Engineering of Mechanically Demanding Tissues

Soft tissues are commonly fiber-reinforced hydrogel composite structures, distinguishable from hard tissues by their low mineral and high water content. In this work, we proposed the development of 3D printed hydrogel constructs of the biopolymers chitosan (CHI) and cellulose nanofibers (CNFs), both without any chemical modification, which processing did not incorporate any chemical crosslinking. The unique mechanical properties of native cellulose nanofibers offer new strategies for the design of environmentally friendly high mechanical performance composites. In the here proposed 3D printed bioinspired CNF-filled CHI hydrogel biomaterials, the chitosan serves as a biocompatible matrix promoting cell growth with balanced hydrophilic properties, while the CNFs provide mechanical reinforcement to the CHI-based hydrogel. By means of extrusion-based printing (EBB), the design and development of 3D functional hydrogel scaffolds was achieved by using low concentrations of chitosan (2.0-3.0% (w/v)) and cellulose nanofibers (0.2-0.4% (w/v)). CHI/CNF printed hydrogels with good mechanical performance (Young's modulus 3.0 MPa, stress at break 1.5 MPa, and strain at break 75%), anisotropic microstructure and suitable biological response, were achieved. The CHI/CNF composition and processing parameters were optimized in terms of 3D printability, resolution, and quality of the constructs (microstructure and mechanical properties), resulting in good cell viability. This work allows expanding the library of the so far used biopolymer compositions for 3D printing of mechanically performant hydrogel constructs, purely based in the natural polymers chitosan and cellulose, offering new perspectives in the engineering of mechanically demanding hydrogel tissues like intervertebral disc (IVD), cartilage, meniscus, among others.

Cellulose-based polymers

The presented chapter deals with structure, morphology, and properties aspects concerning cellulose-based polymers in both research and industrial production, such as cellulose fibers, cellulose membranes, cellulose nanocrystals, and bacterial cellulose, etc. The idea was to highlight the main cellulose-based polymers and cellulose derivatives, as well as the dissolution technologies in processing cellulose-based products. The structure and properties of cellulose are introduced briefly. The main attention has been paid to swelling and dissolution of cellulose in order to yield various kinds of cellulose derivatives through polymerization. The main mechanisms and methods are also presented. Finally, the environmental friendly and green cellulose-based polymers will be evaluated as one of the multifunctional and smart materials with significant progress.

MFC/NFC-Based Foam/Aerogel for Production of Porous Materials: Preparation, Properties and Applications

Nanofibrillated cellulose and microfibrillated cellulose are potential raw materials separated from plant fibers with a high aspect ratio and excellent mechanical properties, which can be applied in various fields (packaging, medicine, etc.). They have unique advantages in the preparation of aerogels and foams, and have attracted widespread attention in recent years. Cellulose-based porous materials have good biodegradability and biocompatibility, while high porosity and high specific surface area endow them with strong mechanical properties and liquid retention performance, which can be used in wall construction, sewage treatment and other fields. At present, the preparation method of this material has been widely reported, however, due to various process problems, the actual production has not been realized. In this paper, we summarize the existing technical problems and main solutions; in the meantime, two stable systems and several drying processes are described, and the application potential of cellulose-based porous materials in the future is described, which provides a reference for subsequent research.

Versatile Types of Polysaccharide-Based Drug Delivery Systems: From Strategic Design to Cancer Therapy

Chemotherapy is still the most direct and effective means of cancer therapy nowadays. The proposal of drug delivery systems (DDSs) has effectively improved many shortcomings of traditional chemotherapy drugs. The technical support of DDSs lies in their excellent material properties. Polysaccharides include a series of natural polymers, such as chitosan, hyaluronic acid, and alginic acid. These polysaccharides have good biocompatibility and degradability, and they are easily chemical modified. Therefore, polysaccharides are ideal candidate materials to construct DDSs, and their clinical application prospects have been favored by researchers. On the basis of versatile types of polysaccharides, this review elaborates their applications from strategic design to cancer therapy. The construction and modification methods of polysaccharide-based DDSs are specifically explained, and the latest research progress of polysaccharide-based DDSs in cancer therapy are also summarized. The purpose of this review is to provide a reference for the design and preparation of polysaccharide-based DDSs with excellent performance.

Aqueous Polymer Modification of Cellulose Nanofibrils by Grafting-Through a Reactive Methacrylate Group

Modifying the surface of cellulose nanofibrils (CNFs) produced by mechanical refinement with a variety of polymer functional groups in an entirely water-based system is challenging because only surface hydroxyl groups are accessible. To address this limitation, an entirely water-based, polymer modification scheme is developed. CNFs are functionalized with a reactive methacrylate functional group followed by subsequent grafting-through polymerization. This modification worked with a variety of water-soluble and water-insoluble (meth)acrylates and (meth)acrylamides, grafting up to 45 wt% polymer on to the CNFs. The reaction conditions introducing the methacrylate functional group are adjusted to vary the degree of functionality. Soxhlet extraction of modified samples demonstrates that the reactive methacrylate group is necessary to facilitate polymer grafting. The degree of functionalization of the polymers is studied via quantitative transmission IR spectroscopy and the morphology of the resulting cellulose nanofibrils is studied via a combination of optical, scanning electron, and atomic force microscopy. High levels of polymer modification do not significantly affect the micrometer-scale fibril morphology.

Eco-friendly nanocellulose and its biomedical applications: current status and future prospect

Cellulose is the earth's leading natural polymer. It is known for its properties like biocompatibility, high mechanical strength, cost-effectiveness and lightweight. Nanocellulose displays better properties as compared to the native cellulose fibre. The nanocellulose is very remunerative in the arenas of routine application especially in health care, food industry, sanitary products and many more. In the biomedical area, cellulose-based products are utilized in applications like wound healing, dental applications, drug delivery, antimicrobial material, etc. Nanocellulose biomaterials have been commercialised, representing the material of new generation. With the objective to comprehend the contribution of nanocellulose in the current status and future development in biomedical utilisations, the review is focused on cellulose, nanocellulose, types and sources of nanocellulose, its preparation, characteristics, constraints related to its composites through the analysis of certain scientific reports.

Spray-dried bacterial cellulose nanofibers: A new generation of pharmaceutical excipient intended for intestinal drug delivery

Defibrillation of bacterial cellulose by ultra-refining was efficient to release nanofibers (BCNF) which were spray dried with the matrices formers mannitol (MN), maltodextrin or hydroxypropylmethylcellulose. The best microsystem comprised the association of BCNF and MN, so the selected microparticles were loaded with diclofenac sodium or caffeine. Depending on the proportion of BCNF, the nanofibers collapse promoted by spray drying can occur onto surface or into microparticles core, leading to different release behaviors. Samples showed pH-dependent drug release, so the microsystem developed with the lowest BCNF concentration showed important trend to gastroresistance. Caffeine was spray dried as a free drug and for this reason it was devoid of any control over release rates. The set of results showed BCNF can be considered an interesting and potential pharmaceutical excipient for lipophilic drugs. Beyond that, BCNF association with MN can lead to novel enteric drug delivery systems based on natural polymers.

Nanocellulose: From an agricultural waste to a valuable pharmaceutical ingredient

Cellulose was and still is the most abundant biopolymer generated from all plant fibers including agricultural wastes. Using this waste as a starting material in the production of new products is a field of great interest. The demand for renewable and available resources in combination with advanced technologies is a necessity to develop new generations of advanced nanomaterials. This review aims to present integrated details on the extraction techniques and structure of nanofibrillated cellulose as well as cellulose nanocrystals derived from agricultural wastes besides the different treatment methods used to be suitable for several pharmaceutical applications. Different pharmaceutical applications are described, including controlled, sustained or rapid drug delivery, stabilizing agent, and its use as safe and sustained environment for cell culture allowing its use in tissue engineering field.

Biodegradation of Crystalline Cellulose Nanofibers by Means of Enzyme Immobilized-Alginate Beads and Microparticles

Recent advances in nanocellulose technology have revealed the potential of crystalline cellulose nanofibers to reinforce materials which are useful for tissue engineering, among other functions. However, the low biodegradability of nanocellulose can possess some problems in biomedical applications. In this work, alginate particles with encapsulated enzyme cellulase extracted from Trichoderma reesei were prepared for the biodegradation of crystalline cellulose nanofibers, which carrier system could be incorporated in tissue engineering biomaterials to degrade the crystalline cellulose nanoreinforcement in situ and on-demand during tissue regeneration. Both alginate beads and microparticles were processed by extrusion-dropping and inkjet-based methods, respectively. Processing parameters like the alginate concentration, concentration of ionic crosslinker Ca2+, hardening time, and ionic strength of the medium were varied. The hydrolytic activity of the free and encapsulated enzyme was evaluated for unmodified (CNFs) and TEMPO-oxidized cellulose nanofibers (TOCNFs) in suspension (heterogeneous conditions); in comparison to solubilized cellulose derivatives (homogeneous conditions). The enzymatic activity was evaluated for temperatures between 25-75 °C, pH range from 3.5 to 8.0 and incubation times until 21 d. Encapsulated cellulase in general displayed higher activity compared to the free enzyme over wider temperature and pH ranges and for longer incubation times. A statistical design allowed optimizing the processing parameters for the preparation of enzyme-encapsulated alginate particles presenting the highest enzymatic activity and sphericity. The statistical analysis yielded the optimum particles characteristics and properties by using a formulation of 2% (w/v) alginate, a coagulation bath of 0.2 M CaCl2 and a hardening time of 1 h. In homogeneous conditions the highest catalytic activity was obtained at 55 °C and pH 4.8. These temperature and pH values were considered to study the biodegradation of the crystalline cellulose nanofibers in suspension. The encapsulated cellulase preserved its activity for several weeks over that of the free enzyme, which latter considerably decreased and practically showed deactivation after just 10 d. The alginate microparticles with their high surface area-to-volume ratio effectively allowed the controlled release of the encapsulated enzyme and thereby the sustained hydrolysis of the cellulose nanofibers. The relative activity of cellulase encapsulated in the microparticles leveled-off at around 60% after one day and practically remained at that value for three weeks.

Electrospun Nanocomposites Containing Cellulose and Its Derivatives Modified with Specialized Biomolecules for an Enhanced Wound Healing

Wound healing requires careful, directed, and effective therapies to prevent infections and accelerate tissue regeneration. In light of these demands, active biomolecules with antibacterial properties and/or healing capacities have been functionalized onto nanostructured polymeric dressings and their synergistic effect examined. In this work, various antibiotics, nanoparticles, and natural extract-derived products that were used in association with electrospun nanocomposites containing cellulose, cellulose acetate and different types of nanocellulose (cellulose nanocrystals, cellulose nanofibrils, and bacterial cellulose) have been reviewed. Renewable, natural-origin compounds are gaining more relevance each day as potential alternatives to synthetic materials, since the former undesirable footprints in biomedicine, the environment, and the ecosystems are reaching concerning levels. Therefore, cellulose and its derivatives have been the object of numerous biomedical studies, in which their biocompatibility, biodegradability, and, most importantly, sustainability and abundance, have been determinant. A complete overview of the recently produced cellulose-containing nanofibrous meshes for wound healing applications was provided. Moreover, the current challenges that are faced by cellulose acetate- and nanocellulose-containing wound dressing formulations, processed by electrospinning, were also enumerated.

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.

Fabrication of ultrathin nanocellulose shells on tough microparticles via an emulsion-templated colloidal assembly: towards versatile carrier materials

Here, we develop a robust approach to forming an ∼8 nm thick cellulose nanofiber (CNF) shell on polymer microparticles through an emulsion-templated assembly. The median diameter of the CNF-shelled microparticles was 3.0 μm. The microparticles showed good dispersibility in water with a ζ-potential of -46.7 ± 0.5 mV and had good mechanical resistance. The surface CNF shells showed pH-sensitive drug loading/releasing properties, which suggest potential for a range of therapeutic and biomedical applications.

Nanocellulose applications in sustainable electrochemical and piezoelectric systems: A review

Recent studies advocate the use of cellulose nanomaterials (CNs) as a sustainable carbohydrate polymer in numerous innovative electronics for their quintessential features such as flexibility, low thermal expansion and self-/directed assembly within multiphase matrices. Herein, we review the contemporary advances in CN-built electrochemical systems and highlight the constructive effects of these nanoscopic entities once engineered in conductive composites, proton exchange membranes (PEMs), electrochromics, energy storage devices and piezoelectric sensors. The adopted strategies and designs are discussed in view of CN roles as copolymer, electrolyte reservoir, binder and separator. Finally, physiochemical attributes and durability of resulting architectures are compared to conventional materials and the possible challenges/solutions are delineated to realize the promising capabilities. The volume of the up-to-present literature in the field indeed implies to nanocellulose overriding importance and the presented angles perhaps shed more lights on prospect of the biosphere's most dominant biomaterial in the energy-related arena that deserve attention.

In vitro investigation of the influence of nano-fibrillated cellulose on lipid digestion and absorption

Nanocellulose, including nano-fibrillated cellulose (NFC), has been a topic of significant interest and a number of studies have focused on using it for the fabrication of stable oil-in-water emulsions. However, limited studies have been performed to understand the potential influence of NFC on lipid digestion and absorption. In this study, a simulated digestion model, consisting of salivary, gastric and intestinal digestion phases, was used to investigate the effects of NFC on lipid digestion and absorption. To better understand the mechanisms behind, the effects of NFC on lipase activity, micellar solubility of cholesterol and bile acid diffusion were studied in addition to the cholesterol adsorption capacity of NFC, with conventional cellulose as a comparison. Results showed that NFC slightly reduced lipase activity, but NFC or cellulose at concentrations up to 1.1% (w/w) did not significantly influence lipid digestion under simulated intestinal conditions. Moreover, NFC showed greater bile acid retardation effect than cellulose, and slightly higher cholesterol adsorption capacity probably due to its larger specific surface area. Nonetheless, NFC did not significantly affect micellar solubility of cholesterol. These results suggest that NFC, when added into fat-rich foods, may have health benefits via its viscosity effect and retardation effect on bile acid absorption.

Amorphisation of Free Acid Ibuprofen and Other Profens in Mixtures with Nanocellulose: Dry Powder Formulation Strategy for Enhanced Solubility

The formulation of arylpropionic acid derivatives (profens), which are poorly soluble Biopharmaceutical Classification System (BCS) Type II drugs, has a strong impact on their therapeutic action. This article shows that heat-treated powder mixtures of free acid profens with high surface area Cladophora cellulose induces drug amorphization and results in enhanced solubility and bioavailability. Similar mixtures produced using conventional low surface area cellulose, i.e., microcrystalline cellulose, does not produce the same effect. The concept is thoroughly described and links the solid-state characterization data, such as differential scanning calorimetry, X-ray powder diffraction, and Fourier-transform infra-red spectroscopy, with in vitro dissolution in biorelevant media and in vivo pharmacokinetic analysis in rats. The concept is demonstrated for several substances from the profens group, including ibuprofen (main model drug), ketoprofen, flurbiprofen, and naproxen. The presented approach opens new ways to produce solid dosage forms of profen drugs in their free acidic form as alternatives to existing analogues, e.g., drug-salt conjugates or soft gel liquid capsules.

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.

Recent advances in nanoengineering cellulose for cargo delivery

The recent decade has witnessed a growing demand to substitute synthetic materials with naturally-derived platforms for minimizing their undesirable footprints in biomedicine, environment, and ecosystems. Among the natural materials, cellulose, the most abundant biopolymer in the world with key properties, such as biocompatibility, biorenewability, and sustainability has drawn significant attention. The hierarchical structure of cellulose fibers, one of the main constituents of plant cell walls, has been nanoengineered and broken down to nanoscale building blocks, providing an infrastructure for nanomedicine. Microorganisms, such as certain types of bacteria, are another source of nanocelluloses known as bacterial nanocellulose (BNC), which benefit from high purity and crystallinity. Chemical and mechanical treatments of cellulose fibrils made up of alternating crystalline and amorphous regions have yielded cellulose nanocrystals (CNC), hairy CNC (HCNC), and cellulose nanofibrils (CNF) with dimensions spanning from a few nanometers up to several microns. Cellulose nanocrystals and nanofibrils may readily bind drugs, proteins, and nanoparticles through physical interactions or be chemically modified to covalently accommodate cargos. Engineering surface properties, such as chemical functionality, charge, area, crystallinity, and hydrophilicity, plays a pivotal role in controlling the cargo loading/releasing capacity and rate, stability, toxicity, immunogenicity, and biodegradation of nanocellulose-based delivery platforms. This review provides insights into the recent advances in nanoengineering cellulose crystals and fibrils to develop vehicles, encompassing colloidal nanoparticles, hydrogels, aerogels, films, coatings, capsules, and membranes, for the delivery of a broad range of bioactive cargos, such as chemotherapeutic drugs, anti-inflammatory agents, antibacterial compounds, and probiotics. SYNOPSIS: Engineering certain types of microorganisms as well as the hierarchical structure of cellulose fibers, one of the main building blocks of plant cell walls, has yielded unique families of cellulose-based nanomaterials, which have leveraged the effective delivery of bioactive molecules.

Enhancement of hemostatic property of plant derived oxidized nanocellulose-silk fibroin based scaffolds by thrombin loading

To combat post-surgical and traumatic bleeding conditions effective hemostasis is of great importance. The study was designed to investigate the effect of thrombin (Th) loading on hemostatic performance of TEMPO-oxidized cellulose nanofiber (TOCN)-silk fibroin (SF) scaffolds. Addition of SF with TOCN significantly (***P < 0.001) increased blood absorption capacity and improved biocompatibility of TOCN. Thrombin loading potentiated platelet activation and hemostatic property of scaffolds (TOCN-SF-Th) compared to samples without thrombin (TOCN-SF). The hemostatic time of TOCN-SF5-Th in rabbit ear artery bleeding model was reduced (*** P < 0.001) to 114 s from 220 s of TOCN-SF5. Reduction in bleeding time and blood loss of TOCN-SF5-Th in rat tail amputation and liver avulsion model was comparable to commercial hemostat (Floseal). Surface morphology (SEM) of samples applied on bleeding site showed that RBCs and fibrin fiber could strongly interact with TOCN-SF and TOCN-SF-Th scaffolds. The result suggests that TOCN-SF-Th can be a promising candidate for designing hemostatic agents.

Polyion complex hydrogels from chemically modified cellulose nanofibrils: Structure-function relationship and potential for controlled and pH-responsive release of doxorubicin

Herein, we report the fabrication of a polyion complex hydrogel from two oppositely charged derivatives of cellulose nanofibrils (CNF). CNF was produced from dissolving pulp through subsequent periodate oxidation, chemical modification, and microfluidization. Three different durations for periodate oxidation (30 min, 120 min, and 180 min) resulted in three different aldehyde contents. Further, two types of chemical modifications were introduced to react with the resulting aldehydes: chlorite oxidation to yield anionic CNF with carboxylic acid groups (DCC) and imination with Girard's reagent T to yield cationic CNF containing quaternary ammonium groups (CDAC). Functional group contents were assessed using conductometric titration and elemental analysis, while nanofibril morphologies were assessed using atomic force microscopy (AFM). Longer durations of periodate oxidation did not yield different width profile but was found to decrease fibril length. The formation of self-standing hydrogel through mixing of DCC and CDAC dispersions was investigated. Oscillatory rheology was performed to assess the relative strengths of different gels. Self-standing hydrogels were obtained from mixture of DCC180 and CDAC180 dispersions in acetate buffer at pH 4 and 5 at a low concentration of 0.5% w/w that displayed approximately 10-fold increase in storage and loss moduli compared to those of the individual dispersions. Self-standing gels containing doxorubicin (an anticancer drug) displayed pH-responsive release profiles. At physiological pH 7.4, approximately 65% of doxorubicin was retained past a burst release regime, while complete release was observed within 5 days at pH 4. Biocompatibility of DCC180, CDAC180, and their mixture were investigated through quantification of the metabolic activity of NIH3T3 cells in vitro. No significant cytotoxicity was observed at concentrations up to 900 µg/mL. In short, the nanocellulose-based polyion complex hydrogels obtained in this study are promising nature-derived materials for biomedical applications.

STATEMENT OF SIGNIFICANCE

We demonstrate that polyion complex can be formed between two cellulose nanofibrils containing complementary charges. To the best of our knowledge, this is the first time that polyion complex formation between complementarily-modified cellulose nanofibrils has been reported, and the results may lead to new ideas on applications of the very promising nanocellulosic materials. The polyion complex helps form a self-standing network that is demonstrated to provide controlled and pH-responsive release of doxorubicin. Particularly, the report explores the connection between the physical properties of functionalizable nanocellulosic materials and their potential biomedical applications. Thus, the study encompasses several broad fields of materials science and engineering, chemistry, and biomedical science that we believe is in line with the readers' interests.

Entangled and colloidally stable microcrystalline cellulose matrices in controlled drug release

Drug release from a new type of matrix material consisting of partially fibrillated microcrystalline cellulose was investigated. A mechanical treatment of novel AaltoCell™ cellulose microcrystals caused partial opening of the nanofibrillary structure of the cellulose particles and entanglement of individual particles led into formation of an elastic network of microcrystalline cellulose. The rheological properties of the stable hydrogel-like materials were characterised by shear rheometry. Model compounds metronidazole and lysozyme were successfully employed in drug release experiments carried out by delignified (bleached) and lignin-containing matrices. The viscosity as well as the lignin-content played a role in the release dynamics of the drugs. Microcrystalline AaltoCell™ was proven as high-performing material for diffusion controlled release of the chosen model compounds and can be seen as a safe and economical alternative for novel matrix materials such as nanocellulose or cellulose derivatives.

Determination of lysine content based on an in situ pretreatment and headspace gas chromatographic measurement technique

This work reports on a simple method for the determination of lysine content by an in situ sample pretreatment and headspace gas chromatographic measurement (HS-GC) technique, based on carbon dioxide (CO₂) formation from the pretreatment reaction (between lysine and ninhydrin solution) in a closed vial. It was observed that complete lysine conversion to CO₂ could be achieved within 60 min at 60 °C in a phosphate buffer medium (pH = 4.0), with a minimum molar ratio of ninhydrin/lysine of 16. The results showed that the method had a good precision (RSD < 5.23%) and accuracy (within 6.80%), compared to the results measured by a reference method (ninhydrin spectroscopic method). Due to the feature of in situ sample pretreatment and headspace measurement, the present method becomes very simple and particularly suitable to be used for batch sample analysis in lysine-related research and applications. Graphical abstract The flow path of the reaction and HS-GC measurement for the lysine analysis.