Cationic Poly(2-aminoethylmethacrylate) and Poly(N-(2-aminoethylmethacrylamide) Modified Cellulose Nanocrystals: Synthesis, Characterization, and Cytotoxicity

Direct and Indirect Cationization of Cellulose Nanocrystals: Structure-Properties Relationship and Virus Capture Activity

Due to increasing public concern over hygiene, there have been many studies investigating antimicrobial and antiviral agents recently. With the aim of developing biobased virucidal/virus capture agents, we report a chemical modification of the cellulose nanocrystals (CNCs) surface with poly(2-dimethylamino) ethyl acrylate) methyl chloride quaternary salt (Q-PDMAEA) to introduce the positively charged functional groups. The surface of CNCs was modified through direct and indirect graft polymerization. Subsequently, the direct and indirect cationization effect on the degree of functionalization, thermal stability, crystallinity, and antiviral activity of CNCs was investigated. Indirect cationization produced the highest degree of polymer grafting, increasing particle size and thermal stability. Further, the modified CNCs were tested for their ability to capture nonenveloped bacteriophages PhiX174 (ΦX174) and MS2. We observed a significant (>4.19 log10) reduction in total viral load by specific functionalized CNCs. However, the activity depended on the structure of functional groups, surface charge density, and the type of virus under study. Overall, the direct and indirect cationization of CNC leads to biobased agents with immobilized cationic charge, with good virus capture activity. Such agents can be used for various applications including textiles, packaging, wastewater treatment, etc.

Copolymer-Functionalized Cellulose Nanocrystals as a pH- and NIR-Triggered Drug Carrier for Simultaneous Photothermal Therapy and Chemotherapy of Cancer Cells

As a class of biocompatible and biodegradable naturally derived nanomaterials, cellulose nanocrystals (CNCs) with diverse surface functionalization have aroused considerable attention for a range of biomedical applications in drug or gene delivery, as a fluorescent nanoprobe, in cancer targeting, and in photothermal cancer therapy, among others. Herein, we construct the copolymer-functionalized CNCs as a pH- and near-infrared (NIR)-triggered drug carrier for simultaneous photothermal therapy and chemotherapy of cancer cells. Poly(ε-caprolactone)-b-poly(2-(dimethylamino)ethyl methacrylate) (PCL-b-PDMAEMA) was conjugated onto the surface of CNCs through ring-opening polymerization, followed by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The resultant CNC-based drug carrier can encapsulate doxorubicin (DOX) as a therapeutic agent and indocyanine green (ICG) as an NIR dye in the PCL core and the PDMAEMA shell, respectively, via hydrophobic and electrostatic interactions. In addition to the intrinsic pH response, the release profile of DOX can also be controlled by the duration of laser irradiation due to collapse of the crystal structure of the PCL domain with the increase of temperature induced by photothermal conversion. The drug carrier can exhibit enhanced cytotoxicity toward HepG2, human hepatocyte carcinoma, cells upon laser irradiation, which can be attributed to the synergistic effect arising from NIR-triggered burst release of DOX and photothermal heating. The rod-like morphology of the CNC-based drug carrier may help accelerate the endocytosis in cell membranes compared with its common spherical counterpart. Based on the abovementioned advantages, copolymer-functionalized CNCs can serve as a promising candidate for effective cancer treatment.

Cellulose Nanocrystals/Chitosan-Based Nanosystems: Synthesis, Characterization, and Cellular Uptake on Breast Cancer Cells

Cellulose nanocrystals (CNCs) are elongated biobased nanostructures with unique characteristics that can be explored as nanosystems in cancer treatment. Herein, the synthesis, characterization, and cellular uptake on folate receptor (FR)-positive breast cancer cells of nanosystems based on CNCs and a chitosan (CS) derivative are investigated. The physical adsorption of the CS derivative, containing a targeting ligand (folic acid, FA) and an imaging agent (fluorescein isothiocyanate, FITC), on the surface of the CNCs was studied as an eco-friendly methodology to functionalize CNCs. The fluorescent CNCs/FA-CS-FITC nanosystems with a rod-like morphology showed good stability in simulated physiological and non-physiological conditions and non-cytotoxicity towards MDA-MB-231 breast cancer cells. These functionalized CNCs presented a concentration-dependent cellular internalization with a 5-fold increase in the fluorescence intensity for the nanosystem with the higher FA content. Furthermore, the exometabolic profile of the MDA-MB-231 cells exposed to the CNCs/FA-CS-FITC nanosystems disclosed a moderate impact on the cells’ metabolic activity, limited to decreased choline uptake and increased acetate release, which implies an anti-proliferative effect. The overall results demonstrate that the CNCs/FA-CS-FITC nanosystems, prepared by an eco-friendly approach, have a high affinity towards FR-positive cancer cells and thus might be applied as nanocarriers with imaging properties for active targeted therapy.

State-of-art review on preparation, surface functionalization and biomedical applications of cellulose nanocrystals-based materials

Cellulose nanocrystals (CNCs) are a class of sustainable nanomaterials that are obtained from plants and microorganisms. These naturally derived nanomaterials are of abundant hydroxyl groups, well biocompatibility, low cost and biodegradable potential, making them suitable and promising candidates for various applications, especially in biomedical fields. In this review, the recent advances and development on the preparation, surface functionalization and biomedical applications of CNCs-based materials have been summarized and outlined. The main context of this paper could be divided into the following three parts. In the first part, the preparation strategies based on physical, chemical, enzymatic and combination techniques for preparation of CNCs have been summarized. The surface functionalization methods for synthesis CNCs-based materials with designed properties and functions were outlined in the following section. Finally, the current state about applications of CNCs-based materials for tissue engineering, medical hydrogels, biosensors, fluorescent imaging and intracellular delivery of biological agents have been highlighted. Moreover, current issues and future directions about the above aspects have also pointed out and discussed. We believe this review will attract great research attention of scientists from materials, chemistry, biomedicine and other disciplines. It will also provide some important insights on the future development of CNCs-based materials especially in biomedical fields.

Effect of Reaction Media on Grafting Hydrophobic Polymers from Cellulose Nanocrystals via Surface-Initiated Atom-Transfer Radical Polymerization

Hydrophobic polymer-grafted cellulose nanocrystals (CNCs) were produced via surface-initiated atom-transfer radical polymerization (SI-ATRP) in two different solvents to examine the role of reaction media on the extent of surface modification. Poly(butyl acrylate)-grafted CNCs were synthesized in either dimethylformamide (DMF) (D-PBA-g-CNCs) or toluene (T-PBA-g-CNCs) alongside a free polymer from a sacrificial initiator. The colloidal stability of unmodified CNCs, initiator-modified CNCs, and PBA-g-CNCs in water, DMF, and toluene was evaluated by optical transmittance. The enhanced colloidal stability of initiator-modified CNCs in DMF led to improved accessibility to initiator groups during polymer grafting; D-PBA-g-CNCs had 30 times more grafted chains than T-PBA-g-CNCs, determined by thermogravimetric and elemental analysis. D-PBA-g-CNCs dispersed well in toluene and were hydrophobic with a water contact angle of 124° (for polymer grafts > 13 kDa) compared to 25° for T-PBA-g-CNCs. The cellulose crystal structure was preserved, and individual nanoparticles were retained when grafting was carried out in either solvent. This work highlights that optimizing CNC colloidal stability prior to grafting is more crucial than solvent-polymer compatibility to obtain high graft densities and highly hydrophobic CNCs via SI-ATRP.

Recent Progress on Cellulose-Based Ionic Compounds for Biomaterials

Glycans play important roles in all major kingdoms of organisms, such as archea, bacteria, fungi, plants, and animals. Cellulose, the most abundant polysaccharide on the Earth, plays a predominant role for mechanical stability in plants, and finds a plethora of applications by humans. Beyond traditional use, biomedical application of cellulose becomes feasible with advances of soluble cellulose derivatives with diverse functional moieties along the backbone and modified nanocellulose with versatile functional groups on the surface due to the native features of cellulose as both cellulose chains and supramolecular ordered domains as extractable nanocellulose. With the focus on ionic cellulose-based compounds involving both these groups primarily for biomedical applications, a brief introduction about glycoscience and especially native biologically active glycosaminoglycans with specific biomedical application areas on humans is given, which inspires further development of bioactive compounds from glycans. Then, both polymeric cellulose derivatives and nanocellulose-based compounds synthesized as versatile biomaterials for a large variety of biomedical applications, such as for wound dressings, controlled release, encapsulation of cells and enzymes, and tissue engineering, are separately described, regarding the diverse routes of synthesis and the established and suggested applications for these highly interesting materials.

Cellulose nanocrystals in cancer diagnostics and treatment

Cancer is currently a major threat to public health, being among the principal causes of death to the global population. With carcinogenesis mechanisms, cancer invasion, and metastasis remaining blurred, cancer diagnosis and novel drug delivery approaches should be developed urgently to enable management and treatment. A dream break-through would be a non-invasive instantaneous monitoring of cancer initiation and progression to fast-track diagnosis for timely specialist treatment decisions. These innovations would enhance the established treatment protocols, unlimited by evasive biological complexities during tumorigenesis. It is therefore contingent that emerging and future scientific technologies be equally biased towards such innovations by exploiting the apparent properties of new developments and materials especially nanomaterials. CNCs as nanomaterials have undisputable physical and excellent biological properties that enhanced their interest as biomedical materials. This article therefore highlights CNCs utility in cancer diagnosis and therapy. Their extraction, properties, modification, in-vivo/in-vitro medical applications, biocompatibility, challenges and future perspectives are precisely discussed.

Nucleophilic Displacement Reaction on Tosyl Cellulose by L-Methionine to the Synthesis of Novel Water-Soluble Cellulose Derivative and Its Antibacterial Activity

A novel ampholytic cellulose derivative, cellulose-L-methionine, has been synthesized by means of an esterification reaction of microcrystalline cellulose with tosyl chloride (p-TsCl) in DMAc/LiCl (8%) at 8°C that was followed by nucleophilic displacement (SN) of the tosyl group by the L-methionine amino acid. The resulting structure of cellulose-L-methionine has been characterized by elemental analysis (CHNSO), Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), and scanning electron microscopy (SEM). The antibacterial activity of the synthesized product was screened against Gram-positive and Gram-negative microbial strains such as Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, by the agar well diffusion method, and compared with commercial antibiotics such as ampicillin and chloramphenicol. It was found that antibacterial experiment revealed excellent antibacterial activity of the cellulose-methionine with respect to a minimal inhibitory concentration (MIC) reference.

Nanocellulose in Drug Delivery and Antimicrobially Active Materials

In recent years, nanocellulose (NC) has also attracted a great deal of attention in drug delivery systems due to its unique physical properties, specific surface area, low risk of cytotoxicity, and excellent biological properties. This review is focused on nanocellulose based systems acting as carriers to be used in drug or antimicrobial delivery by providing different but controlled and sustained release of drugs or antimicrobial agents, respectively, thus showing potential for different routes of applications and administration. Microorganisms are increasingly resistant to antibiotics, and because, generally, the used metal or metal oxide nanoparticles at some concentration have toxic effects, more research has focused on finding biocompatible antimicrobial agents that have been obtained from natural sources. Our review contains the latest research from the last five years that tested nanocellulose-based materials in the field of drug delivery and antimicrobial activity.

Surface Modification of Cellulose Nanocrystals via RAFT Polymerization of CO2-Responsive Monomer-Tuning Hydrophobicity

Cellulose nanocrystals (CNCs) were converted into a CO₂-responsive composite nanomaterial by grafting poly(dimethylaminoethyl methacrylate) (PDMAEMA), poly(diethylaminoethyl methacrylate) (PDEAEMA), and poly(diisopropylaminoethyl methacrylate) (PDPAEMA) onto its surface using both grafting-to and grafting-from approaches. The zeta potential (ζ) of the graft-modified CNC could be reversibly switched by protonation/deprotonation of the tertiary amine groups simply by sparging with CO₂ and N₂, respectively. Depending on the grafting density and the molecular weight of the polymer grafts, CNC can form stable aqueous dispersions at either mildly acidic pH (under CO₂) or mildly basic (under N₂) conditions. Moreover, it was also determined that the CNC hydrophobicity, assessed using phase-shuttling experiments at different pH values, was also dependent on both the grafting density and molecular weight of the polymer grafts, thereby making it possible to easily tune CNC dispersibility and/or hydrophobicity.

Synthesis, Characterization and Cytotoxicity Studies of Aminated Microcrystalline Cellulose Derivatives against Melanoma and Breast Cancer Cell Lines

Cellulose based materials are emerging in the commercial fields and high-end applications, especially in biomedicines. Aminated cellulose derivatives have been extensively used for various applications but limited data are available regarding its cytotoxicity studies for biomedical application. The aim of this study is to synthesize different 6-deoxy-amino-cellulose derivatives from Microcrystalline cellulose (MCC) via tosylation and explore their cytotoxic potential against normal fibroblasts, melanoma and breast cancer. 6-deoxy-6-hydrazide Cellulose (Cell Hyd) 6-deoxy-6-diethylamide Cellulose (Cell DEA) and 6-deoxy-6-diethyltriamine Cellulose (Cell DETA) were prepared and characterized by various technologies like Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), nuclear magnetic resonance spectroscopy (NMR), X-ray diffractogram (XRD), Scanning Electron microscopy (SEM), Elemental Analysis and Zeta potential measurements. Cytotoxicity was evaluated against normal fibroblasts (NIH3T3), mouse skin melanoma (B16F10), human epithelial adenocarcinoma (MDA-MB-231) and human breast adenocarcinoma (MCF-7) cell lines. IC₅₀ values obtained from cytotoxicity assay and live/dead assay images analysis showed MCC was non cytotoxic while Cell Hyd, Cell DEA and Cell DETA exhibited noncytotoxic activity up to 200 μg/mL to normal fibroblast cells NIH3T3, suggesting its safe use in medical fields. The mouse skin melanoma (B16F10) are the most sensitive cells to the cytotoxic effects of Cell Hyd, Cell DEA and Cell DETA, followed by human breast adenocarcinoma (MCF-7). Based on our study, it is suggested that aminated cellulose derivatives could be promising candidates for tissue engineering applications and in cancer inhibiting studies in future.

Synthesis and Cytotoxicity Studies of Wood-Based Cationic Cellulose Nanocrystals as Potential Immunomodulators

Polysaccharides have been shown to have immunomodulatory properties. Modulation of the immune system plays a crucial role in physiological processes as well as in the treatment and/or prevention of autoimmune and infectious diseases. Cellulose nanocrystals (CNCs) are derived from cellulose, the most abundant polysaccharide on the earth. CNCs are an emerging class of crystalline nanomaterials with exceptional physico-chemical properties for high-end applications and commercialization prospects. The aim of this study was to design, synthesize, and evaluate the cytotoxicity of a series of biocompatible, wood-based, cationic CNCs as potential immunomodulators. The anionic CNCs were rendered cationic by grafting with cationic polymers having pendant +NMe3 and +NH3 moieties. The success of the synthesis of the cationic CNCs was evidenced by Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, and elemental analysis. No modification in the nanocrystals rod-like shape was observed in transmission electron microscopy and atomic force microscopy analyses. Cytotoxicity studies using three different cell-based assays (MTT, Neutral Red, and LIVE/DEAD®) and three relevant mouse and human immune cells indicated very low cytotoxicity of the cationic CNCs in all tested experimental conditions. Overall, our results showed that cationic CNCs are suitable to be further investigated as immunomodulators and potential vaccine nanoadjuvants.

Ratiometric Fluorescent Mapping of pH and Glutathione Dictates Intracellular Transport Pathways of Micellar Nanoparticles

Visualization of intracellular transport pathways is crucial to investigate the internalization mechanism and understand the intracellular behavior of nanomaterials. Herein, we rationalized the design of micellar nanoparticles (NPs) for ratiometric fluorescent mapping of intracellular pH and glutathione (GSH), two essential parameters for maintaining normal cellular functions. Specifically, pH-sensitive naphthalimide-based probe (NPI) and pH-inert rhodamine B (RhB) were covalently labeled to double hydrophilic block copolymers (DHBCs) using the thiolactone chemistry, enabling the covalent attachment of NPI and RhB to one molecule with a redox-responsive disulfide linkage. The dually labeled DHBCs exhibited blue/orange dual emissions in acidic pH, which was further converted into green/orange dual emissions in neutral pH because of the deprotonation of NPI moieties and the sole green emission in the presence of GSH at neutral pH because of the decreased Förster resonance energy transfer efficiency between an NPI donor and an RhB acceptor as a result of GSH-mediated cleavage of disulfide bonds. These remarkable ratiometric fluorescence changes allowed for not only the simultaneous mapping of the intracellular pH and GSH but also the intracellular transport pathways of internalized NPs.

Graft modification of cold water-soluble starch via nitroxide-mediated polymerisation

Graft modification of cold water-soluble starch with synthetic polymer was conducted using nitroxide-mediated polymerisation.

Colloidal Behavior of Cellulose Nanocrystals Grafted with Poly(2-alkyl-2-oxazoline)s

Polymer grafting onto cellulose nanocrystals (CNCs) has been used as a tool to improve CNC dispersion in nonpolar solvents or polymeric matrixes. The grafting of flexible polymer chains onto rigid particle surfaces leads to significant modifications in colloidal behavior. Here, poly(2-alkyl-2-oxazoline)s of well-defined molar mass and narrow molar mass distribution were synthesized by cationic ring-opening polymerization and grafted onto CNC surfaces, where the coupling reaction was favored when partially hydrolyzed polymers were used (reaching 64% reaction yield). The particles grafted with polymer chains could be redispersed in water after freeze-drying, producing stable dispersions, and they were not cell-toxic up to 10 wt % aqueous dispersion. Colloidal stability, nanostructure organization, and rheological behavior of grafted CNC and CNC-grafted CNC mixtures were evaluated. The rheological behavior of grafted nanoparticles, meanwhile, showed new features when compared to original CNC dispersions. Aqueous CNC dispersions showed a liquid crystal nematic organization and rheological behavior characteristic of true gel (at 5 wt %) prior to drying. On the other hand, nanoparticle dispersions behaved as weak gels upon the addition of 10 wt % of CNC-g-(PEtOx95-s-Ei5) under the same conditions. Dispersions of CNC-g-P(PEtOx-s-Ei) particles obtained by redispersion of freeze-dried particles behaved as a fluid, without the presence of the nematic organization. Through oscillatory rheology and time-domain NMR results, it can be concluded that polymer-water interactions are dominant over CNC-water interactions, being responsible for CNC nematic phase disruption. By introducing polymer chains, the introduction of isotropic character modifies water organization, changing the flow behavior of CNC-grafted with poly(oxazoline)s.

Cellulose nanocrystal driven microphase separated nanocomposites: Enhanced mechanical performance and nanostructured morphology

The interest in the modification of cellulose nanocrystals (CNCs) lies in the potential to homogenously disperse CNCs in hydrophobic polymer matrices and to promote interfacial adhesion. In this work, poly(methyl methacrylate) (PMMA) and poly(butyl acrylate) (PBA) were grafted onto CNCs, thereby imparting their hydrophobic traits. The successful grafting modification led to the increased thermal stability of modified CNCs (MCNCs), and the hydrophobic surface modification was integrated with crystalline structure and morphology of CNCs. The nanocomposites with 7 wt% MCNCs/PBA-co-PMMA had an increase in Young's modulus of >25-fold and in tensile strength at about 3 times compared to these of neat PBA-co-PMMA copolymer. In addition, a micro-phase separated morphology (PBA soft domains, and PMMA and CNC hard domains) of MCNCs/PBA-co-PMMA nanocomposites was observed. The large increase in the storage moduli (glass transition temperatures) and organized morphology of MCNCs/PBA-co-PMMA nanocomposites also elucidated the relationship between mechanical properties and micro-phase separated morphology. Therefore, the MCNCs are effective reinforcing agents for the PBA-co-PMMA thermoplastic elastomers, opening up opportunities for their wide-spread applications in polymer composites.

Advanced Materials through Assembly of Nanocelluloses

There is an emerging quest for lightweight materials with excellent mechanical properties and economic production, while still being sustainable and functionalizable. They could form the basis of the future bioeconomy for energy and material efficiency. Cellulose has long been recognized as an abundant polymer. Modified celluloses were, in fact, among the first polymers used in technical applications; however, they were later replaced by petroleum-based synthetic polymers. Currently, there is a resurgence of interest to utilize renewable resources, where cellulose is foreseen to make again a major impact, this time in the development of advanced materials. This is because of its availability and properties, as well as economic and sustainable production. Among cellulose-based structures, cellulose nanofibrils and nanocrystals display nanoscale lateral dimensions and lengths ranging from nanometers to micrometers. Their excellent mechanical properties are, in part, due to their crystalline assembly via hydrogen bonds. Owing to their abundant surface hydroxyl groups, they can be easily modified with nanoparticles, (bio)polymers, inorganics, or nanocarbons to form functional fibers, films, bulk matter, and porous aerogels and foams. Here, some of the recent progress in the development of advanced materials within this rapidly growing field is reviewed.

Effect of surface organic coatings of cellulose nanocrystals on the viability of mammalian cell lines

Cellulose nanocrystals (CNCs) have emerged as promising candidates for a number of bio-applications. Surface modification of CNCs continues to gain significant research interest as it imparts new properties to the surface of the nanocrystals for the design of multifunctional CNCs-based materials. A small chemical surface modification can potentially lead to drastic behavioral changes of cell-material interactions thereby affecting the intended bio-application. In this work, unmodified CNCs were covalently decorated with four different organic moieties such as a diaminobutane fragment, a cyclic oligosaccharide (β-cyclodextrin), a thermoresponsive polymer (poly[N-isopropylacrylamide]), and a cationic aminomethacrylamide-based polymer using different synthetic covalent methods. The effect of surface coatings of CNCs and the respective dose-response of the above organic moieties on the cell viability were evaluated on mammalian cell cultures (J774A.1 and MFC-7), using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphe-nyltetrazolium bromide and lactate dehydrogenase assays. Overall, the results indicated that cells exposed to surface-coated CNCs for 24 h did not display major changes in cell viability, membrane permeability as well as cell morphology. However, with longer exposure, all these parameters were somewhat affected, which appears not to be correlated with either anionic or cationic surface coatings of CNCs used in this study.

Polyphenol nanoformulations for cancer therapy: experimental evidence and clinical perspective

Cancer is defined as the abnormal cell growth that can cause life-threatening malignancies with high financial costs for patients as well as the health care system. Natural polyphenols have long been used for the prevention and treatment of several disorders due to their antioxidant, anti-inflammatory, cytotoxic, antineoplastic, and immunomodulatory effects discussed in the literature; thus, these phytochemicals are potentially able to act as chemopreventive and chemotherapeutic agents in different types of cancer. One of the problems regarding the use of polyphenolic compounds is their low bioavailability. Different types of formulations have been designed for the improvement of bioavailability of these compounds, nanonization being one of the most notable approaches among them. This study aimed to review current data on the nanoformulations of natural polyphenols as chemopreventive and chemotherapeutic agents and to discuss their molecular anticancer mechanisms of action. Nanoformulations of natural polyphenols as bioactive agents, including resveratrol, curcumin, quercetin, epigallocatechin-3-gallate, chrysin, baicalein, luteolin, honokiol, silibinin, and coumarin derivatives, in a dose-dependent manner, result in better efficacy for the prevention and treatment of cancer. The impact of nanoformulation methods for these natural agents on tumor cells has gained wider attention due to improvement in targeted therapy and bioavailability, as well as enhancement of stability. Today, several nanoformulations are designed for delivery of polyphenolic compounds, including nanosuspensions, solid lipid nanoparticles, liposomes, gold nanoparticles, and polymeric nanoparticles, which have resulted in better antineoplastic activity, higher intracellular concentration of polyphenols, slow and sustained release of the drugs, and improvement of proapoptotic activity against tumor cells. To conclude, natural polyphenols demonstrate remarkable anticancer potential in pharmacotherapy; however, the obstacles in terms of their bioavailability in and toxicity to normal cells, as well as targeted drug delivery to malignant cells, can be overcome using nanoformulation-based technologies, which optimize the bioefficacy of these natural drugs.

Indocyanine green-functionalized bottle brushes of poly(2-oxazoline) on cellulose nanocrystals for photothermal cancer therapy

Bottle brushes of poly(2-oxazoline) on CNCsviaUV-induced photopolymerization and living cationic ring-opening polymerization are demonstrated for efficient photothermal therapy.

Temperature-Responsive Nanofibrillar Hydrogels for Cell Encapsulation

Natural extracellular matrices often have a filamentous nature, however, only a limited number of artificial extracellular matrices have been designed from nanofibrillar building blocks. Here we report the preparation of temperature-responsive nanofibrillar hydrogels from rod-shaped cellulose nanocrystals (CNCs) functionalized with a copolymer of N-isopropylacrylamide and N,N'-dimethylaminoethyl methacrylate. The composition of the copolymer was tuned to achieve gelation of the suspension of copolymer-functionalized CNCs at 37 °C in cell culture medium and gel dissociation upon cooling it to room temperature. The mechanical properties and the structure of the hydrogel were controlled by changing copolymer composition and the CNC-to-copolymer mass ratio. The thermoreversible gels were used for the encapsulation and culture of fibroblasts and T cells and showed low cytotoxicity. Following cell culture, the cells were released from the gel by reducing the temperature, thus, enabling further cell characterization. These results pave the way for the generation of injectable temperature-responsive nanofibrillar hydrogels. The release of cells following their culture in the hydrogels would enable enhanced cell characterization and potential transfer in a different cell culture medium.

Cellulose nanocrystals: a versatile nanoplatform for emerging biomedical applications

INTRODUCTION

Cellulose nanocrystals (CNCs) are bio-based nanomaterials typically derived from the acid hydrolysis of the most abundant natural polymer, cellulose. These nanomaterials have garnered significant interest due to their unique properties, such as uniform rod-like shape, high surface area, high strength, liquid crystalline behavior, tailored surface chemistry, biocompatibility, biodegradability, sustainability and non-toxic carbohydrate-based nature.

AREAS COVERED

The recent developments in the use of unmodified and modified CNCs as versatile nanoplatforms for emerging biomedical applications such as drug delivery systems, enzyme/protein immobilization scaffolds, bioimaging, biosensing and tissue engineering are highlighted. A brief discussion of the biological and toxicity properties of CNCs is also presented.

EXPERT OPINION

While a number of recent studies have indicated that CNCs are promising nanomaterials for biomedical applications, there is a substantial amount of work that still remains to be done before realizing the full therapeutic potential of CNCs. Major effort should be focused on detailed in vitro and in vivo studies of modified CNCs constructs in order to better understand the integration of CNCs in the biological systems.

Nanocellulose, a tiny fiber with huge applications

Nanocellulose is of increasing interest for a range of applications relevant to the fields of material science and biomedical engineering due to its renewable nature, anisotropic shape, excellent mechanical properties, good biocompatibility, tailorable surface chemistry, and interesting optical properties. We discuss the main areas of nanocellulose research: photonics, films and foams, surface modifications, nanocomposites, and medical devices. These tiny nanocellulose fibers have huge potential in many applications, from flexible optoelectronics to scaffolds for tissue regeneration. We hope to impart the readers with some of the excitement that currently surrounds nanocellulose research, which arises from the green nature of the particles, their fascinating physical and chemical properties, and the diversity of applications that can be impacted by this material.

Graft modification of cellulose nanocrystals via nitroxide-mediated polymerisation

Cellulose nanocrystals were graft modfied with PMA and PMMA via nitroxide mediated polymerisation.

Direct functionalization of cellulose nanocrystals with polymer brushes via UV-induced polymerization: access to novel heterogeneous visible-light photocatalysts

An efficient and facile strategy for the preparation of polymer brushes on cellulose nanocrystals via photopolymerization is reported.

Development of curcumin-cyclodextrin/cellulose nanocrystals complexes: New anticancer drug delivery systems

The synthesis of curcumin-cyclodextrin/cellulose nanocrystals (CNCx) nano complexes was performed. CNCx were functionalized by ionic association with cationic β-cyclodextrin (CD) and CD/CNCx complexes were used to encapsulate curcumin. Preliminary in vitro results showed that the resulting curcumin-CD/CNCx complexes exerted antiproliferative effect on colorectal and prostatic cancer cell lines, with IC50s lower than that of curcumin alone.

Cellulose nanocrystal cationic derivative induces NLRP3 inflammasome-dependent IL-1β secretion associated with mitochondrial ROS production

Crystalline cellulose nanocrystals (CNCs) have emerged as novel materials for a wide variety of important applications such as nanofillers, nanocomposites, surface coatings, regenerative medicine and potential drug delivery. CNCs have a needle-like structure with sizes in the range of 100–200 nm long and 5–20 nm wide and a mean aspect ratio 10–100. Despite the great potential applicability of CNCs, very little is known about their potential immunogenicity. Needle-like materials have been known to evoke an immune response in particular to activate the (NOD-like receptor, pyrin domain-containing 3)-inflammasome/IL-1β (Interleukin 1β) pathway. In this study we evaluated the capacity of unmodified CNC and its cationic derivatives CNC-AEM (aminoethylmethacrylate)1, CNC-AEM2, CNC-AEMA(aminoethylmethacrylamide)1 and CNC-AEMA2 to stimulate NLRP3-inflammasome/IL-1β pathway and enhance the production of mitochondrial reactive oxygen species (ROS). Mouse macrophage cell line (J774A.1) was stimulated for 24 h with 50 µg/mL with unmodified CNC and its cationic derivatives. Alternatively, J774A1 or PBMCs (peripheral blood mononuclear cells) were stimulated with CNC-AEMA2 in presence or absence of LPS (lipopolysaccharide). IL-1β secretion was analyzed by ELISA, mitochondrial function by JC-1 staining and ATP content. Intracellular and mitochondrial reactive oxygen species (ROS) were assessed by DCF-DA (2′,7′-dichlorodihydrofluorescein diacetate) and MitoSOX, respectively. Mitochondrial ROS and extracellular ATP were significantly increased in cells treated with CNC-AEMA2, which correlates with the strongest effects on IL-1β secretion in non-primed cells. CNC-AEMA2 also induced IL-1βsecretion in LPS-primed and non-primed PBMCs. Our data suggest that the increases in mitochondrial ROS and ATP release induced by CNC-AEMA2 may be associated with its capability to evoke immune response. We demonstrate the first evidence that newly synthesized cationic cellulose nanocrystal derivative, CNC-AEMA2, has immunogenic properties, which may lead to the development of a potential non-toxic and safe nanomaterial to be used as a novel adjuvant for vaccines.

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Immunogenicity of CNC derivatives was studied on the NLRP3 inflammasome pathway.

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Only CNC-AEMA2 induced IL-1β secretion in non-primed and primed macrophages.

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IL-1β secretion caused by CNC-AEMA2 involves mitochondrial ROS and ATP release.

Thiolated hemicellulose as a versatile platform for one-pot click-type hydrogel synthesis

A one-pot synthetic methodology for the thiolation of O-acetyl-galactoglucomannan (AcGGM) was developed to merge hemicellulose chemistry with "click" chemistry. This was realized by the AcGGM-mediated nucleophilic ring-opening of γ-thiobutyrolactone via the activation of the polysaccharide pendant hydroxyl groups. The incorporation of thiol functionalities onto the hemicellulose backbone was visualized by (1)H and (13)C NMR spectroscopy and was assessed by an Ellman's reagent assay of the thiol groups. The versatility of the thiolated AcGGM was elaborated and demonstrated by conducting several postmodification reactions together with hydrogel formation utilizing thiol-ene and thiol-Michael addition "click" reactions. The one-pot synthesis of thiolated AcGGM is a straightforward approach that can expand the applications of hemicelluloses derived from biomass by employing "click" chemistry.