Liquid-core nanocellulose-shell capsules with tunable oxygen permeability

Oxidative stability and oxygen permeability of oil-loaded capsules produced by spray-drying or electrospraying measured by electron spin resonance

The oxidative stability and the oxygen permeability of oil-loaded capsules were investigated by Electron Spin Resonance (ESR). The capsules were produced by spray-drying or electrospraying in the monoaxial or coaxial configuration using glucose syrup as the encapsulating agent. ESR-spin trapping results showed that electrosprayed capsules oxidized faster and during the early stages of incubation, irrespective of the emitter configuration (monoaxial or coaxial), when compared to those produced by spray-drying. Furthermore, ESR oximetry showed that oxygen inside the spray-dried capsules reached equilibrium with the surrounding atmosphere significantly slower than the monoaxially electrosprayed capsules (i.e., ∼2h and ∼10 min, respectively). These findings have been attributed to the larger particle size of the spray-dried capsules influencing the oxygen diffusion area (i.e., lower surface-to-volume ratio) and diffusion path (i.e., thicker encapsulating wall for a fixed oil load). Together, the lower oxygen uptake reported for the spray-dried capsules correlated well with their higher oxidative stability.

Understanding Nanocellulose-Water Interactions: Turning a Detriment into an Asset

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose-water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

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.

A temperature-responsive release cellulose-based microcapsule loaded with chlorpyrifos for sustainable pest control

Controlled pesticide release in response to environmental stimuli by encapsulating pesticide in carrier is a feasible approach to improve the effective utilization rate. Here, a temperature-responsive release microcapsule loaded with chlorpyrifos (CPF@CM) was prepared from n-hexadecane-in-water emulsions via interfacial polymerization. The microcapsule was consisted of nanofibrillated cellulose (NFC) as the shell wall material and isophorone diisocyanate (IPDI) as the crosslinker. The prepared CPF@CM had pesticide-loading efficiency (33.1 wt%) and favorable adhesion on the surface of cucumber and peanut foliage compared with conventional formulation. Additionally, CPF@CM could protect chlorpyrifos against photodegradation effectively. The in vitro release test showed that microcapsule had adjustable controlled-release characteristics with the change in temperature based on phase transition of the n-hexadecane core. Bioassay studies showed that control efficacy of CPF@CM microcapsule against P. xylostella was positively correlated with temperature because of temperature-induced changes in release rate. The acute toxicity of CPF@CM to zebrafish was reduced more than 5-fold compared with that of CPF technical. These results indicated that the microcapsule release system has great potential in the development of an effective and environmentally friendly pesticide formulation.

Lignocellulosic Biomass for the Synthesis of Nanocellulose and Its Eco-Friendly Advanced Applications

Nanocellulose is a unique and natural compound extracted from native cellulose using different extraction techniques. Nanocellulose is currently attracting attention due to its excellent properties such as special surface chemistry, exceptional physical and chemical strength, and rich hydroxyl groups for modification. In addition, its significant biological properties, like biodegradability, biocompatibility, and non-toxicity, accompanied by being environmentally friendly, are added advantages. The current review is focused on the lignocellulosic biomass processing methods for nanocellulose production and their usage for eco-friendly and environmental sustainability. We have also described insights into different techniques by which cellulosic materials can be changed into cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs). Lastly, we further discussed how nano-cellulosic materials are being used in a variety of industries such as the food sector, biomedical hygiene products, health care, water purification, and sensors. In the review, the unique uses of nanocelluloses in the production of nanocomposite materials, like flexible supercapacitor and polymer matrix, toward minimizing the utilization of global fossil energy and environmental pollution are envisaged. Finally, the significant application of nanomaterials in the areas of packaging industries, health and hygienic sector, cosmetics, and other important sectors are discussed. In the aspect of techno-economically feasibility, nano-cellulose-based materials may prove to be outstanding, environment friendly, and mitigate effluent load.

Recent Advances in Food Emulsions and Engineering Foodstuffs Using Plant-Based Nanocelluloses

In this article, the application of nanocelluloses, especially cellulose nanofibrils and cellulose nanocrystals, as functional ingredients in foods is reviewed. These ingredients offer a sustainable and economic source of natural plant-based nanoparticles. Nanocelluloses are particularly suitable for altering the physicochemical, sensory, and nutritional properties of foods because of their ability to create novel structures. For instance, they can adsorb to air-water or oil-water interfaces and stabilize foams or emulsions, self-assemble in aqueous solutions to form gel networks, and act as fillers or fat replacers. The functionality of nanocelluloses can be extended by chemical functionalization of their surfaces or by using them in combination with other natural food ingredients, such as biosurfactants or biopolymers. As a result, it is possible to create stimuli-responsive, tailorable, and/or active functional biomaterials suitable for a range of foodapplications. In this article, we describe the chemistry, structure, and physicochemical properties of cellulose as well as their relevance for the application of nanocelluloses as functional ingredients in foods. Special emphasis is given to their use as particle stabilizers in Pickering emulsions, but we also discuss their potential application for creating innovative biomaterials with novel functional attributes, such as edible films and packaging. Finally, some of the challenges associated with using nanocelluloses in foods are critically evaluated, including their potential safety and consumer acceptance.

Engineered Multilayer Microcapsules Based on Polysaccharides Nanomaterials

The preparation of microcapsules composed by natural materials have received great attention, as they represent promising systems for the fabrication of micro-containers for controlled loading and release of active compounds, and for other applications. Using polysaccharides as the main materials is receiving increasing interest, as they constitute the main components of the plant cell wall, which represent an ideal platform to mimic for creating biocompatible systems with specific responsive properties. Several researchers have recently described methods for the preparation of microcapsules with various sizes and properties using cell wall polysaccharide nanomaterials. Researchers have focused mostly in using cellulose nanomaterials as structural components in a bio-mimetic approach, as cellulose constitutes the main structural component of the plant cell wall. In this review, we describe the microcapsules systems presented in the literature, focusing on the works where polysaccharide nanomaterials were used as the main structural components. We present the methods and the principles behind the preparation of these systems, and the interactions involved in stabilizing the structures. We show the specific and stimuli-responsive properties of the reported microcapsules, and we describe how these characteristics can be exploited for specific applications.

Bottom-up assembly of nanocellulose structures

Nanocelluloses, both cellulose nanofibrils and cellulose nanocrystals, are gaining research traction due to their viability as key components in commercial applications and industrial processes. Significant efforts have been made to understand both the potential of assembling nanocelluloses, and the limits and prospectives of the resulting structures. This Review focuses on bottom-up techniques used to prepare nanocellulose-only structures, and details the intermolecular and surface forces driving their assembly. Additionally, the interactions that contribute to their structural integrity are discussed along with alternate pathways and suggestions for improved properties. Six categories of nanocellulose structures are presented: (1) powders, beads, and droplets; (2) capsules; (3) continuous fibres; (4) films; (5) hydrogels; and (6) aerogels and dried foams. Although research on nanocellulose assembly often focuses on fundamental science, this Review also provides insight on the potential utilization of such structures in a wide array of applications.

Primary cell wall inspired micro containers as a step towards a synthetic plant cell

The structural integrity of living plant cells heavily relies on the plant cell wall containing a nanofibrous cellulose skeleton. Hence, if synthetic plant cells consist of such a cell wall, they would allow for manipulation into more complex synthetic plant structures. Herein, we have overcome the fundamental difficulties associated with assembling lipid vesicles with cellulosic nanofibers (CNFs). We prepare plantosomes with an outer shell of CNF and pectin, and beneath this, a thin layer of lipids (oleic acid and phospholipids) that surrounds a water core. By exploiting the phase behavior of the lipids, regulated by pH and Mg²⁺ ions, we form vesicle-crowded interiors that change the outer dimension of the plantosomes, mimicking the expansion in real plant cells during, e.g., growth. The internal pressure enables growth of lipid tubules through the plantosome cell wall, which paves the way to the development of hierarchical plant structures and advanced synthetic plant cell mimics.

Assembling synthetic plant cell is difficult due to the presence of primary cell wall. Here, the authors describe the assembly of lipid-containing bodies that can be coated with cellulose and pectin, and show how these so-called plantosomes can be manipulated by changing surrounding milieu.

Digital image colorimetric analysis for evaluating lipid oxidation in oils and its emulsion

Optical analytical images were captured by a digital camera, and lipid peroxidation was monitored using colorimetric determination. The Image-J method was shown to have comparable accuracy to the conventional titration (American Oil Chemists' Society) and UV-Vis spectroscopic methods. Over the PV range 3-14 meq.O₂/kg, a good correlation (R² = 0.9836) was found between the proposed method and UV-Vis method with an SD of ±0.0339 meq.O₂/kg. The range and accuracy of detection were determined from the changes in the Image-J intensity values. At equivalent PV, the limit of detection was 0.175 meq.O₂/kg and the limit of quantitation was 0.35 meq.O₂/kg. The proposed Image-J application can be used to develop fast and portable devices for monitoring peroxide values. These have potential applications in quality control for small-scale farmers and small and medium enterprises.

Oxygen permeability and oxidative stability of fish oil-loaded electrosprayed capsules measured by Electron Spin Resonance: Effect of dextran and glucose syrup as main encapsulating materials

The oxygen permeability and oxidative stability of fish oil-loaded electrosprayed capsules were studied by Electron Spin Resonance (ESR). Electrosprayed capsules with dextran as main biopolymer showed a significantly faster broadening (ΔH_pp) of 16-doxyl-stearate ESR spectrum when compared to glucose syrup capsules. This finding indicates a higher oxygen permeability of dextran capsules than glucose syrup capsules, which is explained by a reduced average free volume in the glucose syrup matrix than in the dextran shell. Moreover, glucose syrup capsules showed a significantly lower increase in the peak-to-peak amplitude of N-tert-butyl-α-phenylnitrone (PBN) ESR spectrum during storage when compared to dextran capsules. This implies a higher oxidative stability of glucose syrup capsules than dextran capsules, which correlated well with the lower oxygen permeability of the former. These results indicated the importance of the oxygen barrier properties of the wall materials when encapsulating long chain omega-3 polyunsaturated fatty acids by electrospraying.

Floating solid cellulose nanofibre nanofoams for sustained release of the poorly soluble model drug furosemide

OBJECTIVES

This study aimed to prepare a furosemide-loaded sustained release cellulose nanofibre (CNF)-based nanofoams with buoyancy.

METHODS

Dry foams consisting of CNF and the model drug furosemide at concentrations of 21% and 50% (w/w) have been prepared by simply foaming a CNF-drug suspension followed by drying. The resulting foams were characterized towards their morphology, solid state properties and dissolution kinetics.

KEY FINDINGS

Solid state analysis of the resulting drug-loaded foams revealed that the drug was present as an amorphous sodium furosemide salt and in form of furosemide form I crystals embedded in the CNF foam cell walls. The foams could easily be shaped and were flexible, and during the drug release study, the foam pieces remained intact and were floating on the surface due to their positive buoyancy. Both foams showed a sustained furosemide release compared to a marketed tablet. It was found that the extent of sustained release from both foams was dependent on the drug loading, the dimension of the foam piece, as well as the solid state of the drug.

CONCLUSIONS

Furosemide-loaded CNF-based foams with sustained release and buoyancy have been successfully prepared in a simple casting and drying procedure.

Solid nanofoams based on cellulose nanofibers and indomethacin-the effect of processing parameters and drug content on material structure

The unique colloidal properties of cellulose nanofibers (CNF), makes CNF a very interesting new excipient in pharmaceutical formulations, as CNF in combination with some poorly-soluble drugs can create nanofoams with closed cells. Previous nanofoams, created with the model drug indomethacin, demonstrated a prolonged release compared to films, owing to the tortuous diffusion path that the drug needs to take around the intact air-bubbles. However, the nanofoam was only obtained at a relatively low drug content of 21wt% using fixed processing parameters. Herein, the effect of indomethacin content and processing parameters on the foaming properties was analysed. Results demonstrate that a certain amount of dissolved drug is needed to stabilize air-bubbles. At the same time, larger fractions of dissolved drug promote coarsening/collapse of the wet foam. The pendant drop/bubble profile tensiometry was used to verify the wet-foam stability at different pHs. The pH influenced the amount of solubilized drug and the processing-window was very narrow at high drug loadings. The results were compared to real foaming-experiments and solid state analysis of the final cellular solids. The parameters were assembled into a processing chart, highlighting the importance of the right combination of processing parameters (pH and time-point of pH adjustment) in order to successfully prepare cellular solid materials with up to 46 wt% drug loading.

Rhamnogalacturonan-I Based Microcapsules for Targeted Drug Release

Drug targeting to the colon via the oral administration route for local treatment of e.g. inflammatory bowel disease and colonic cancer has several advantages such as needle-free administration and low infection risk. A new source for delivery is plant-polysaccharide based delivery platforms such as Rhamnogalacturonan-I (RG-I). In the gastro-intestinal tract the RG-I is only degraded by the action of the colonic microflora. For assessment of potential drug delivery properties, RG-I based microcapsules (~1 μm in diameter) were prepared by an interfacial poly-addition reaction. The cross-linked capsules were loaded with a fluorescent dye (model drug). The capsules showed negligible and very little in vitro release when subjected to media simulating gastric and intestinal fluids, respectively. However, upon exposure to a cocktail of commercial RG-I cleaving enzymes, ~ 9 times higher release was observed, demonstrating that the capsules can be opened by enzymatic degradation. The combined results suggest a potential platform for targeted drug delivery in the terminal gastro-intestinal tract.