Defibrillation Process Research Articles

Nanocellulose as Sustainable Eco-friendly Nanomaterials: Production, Characterization, and Applications

Nanocellulose is a biodegradable nanomaterial derived from lignocellulosic biomass through mechanical, chemical, or enzymatic defibrillation processes to convert wood fibers into nanofibrils. This material consists of a network of cellulosic fibrils with a wide range of diameters, offering unique properties suitable for various functional applications. Nanocellulose can act as a substrate or coating, serving as an eco-friendly alternative to synthetic plastics. Despite having good barrier properties and strong mechanical strength, nanocellulose films are still not as effective as synthetic plastics. They are used in creating barrier materials, flexible electronics, and coatings for paper products.

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

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

Catalytic valorisation of the effluents generated during the defibrillation process of cellulose from almond hulls: A holistic zero-waste biorefinery approach

The acid-free hydrothermal microwave–assisted selective scissoring (Hymass concept) of cellulosic substrates is gaining keen interest in the field of materials science. Besides, implementing catalytic methodologies to upgrade side streams produced during this process could contribute to better, holistic utilisation of the starting feedstock. This work depicts a zero-waste biorefinery concept based on cellulose defibrillation from almond hulls using various hydrotreatment technologies (hydrogenation and hydrodeoxygenation) for downstream processing on a ruthenium catalyst. Therein, the hemicellulose separated from the biomass preconditioning step was converted into sugar alcohols and/or marketable polyols with a relatively high yield (47.4%) by hydrolytic hydrogenation (437 K, 3h, 5.0 MPa H2). Meanwhile, a family of bioactive compounds (3-hydroxypyridines) could be directly extracted from the hydrolysate stream derived from microwave digestion, along with an energy carrier that was chemically stabilised (503 K, 60 min, 4.0 MPa H2) to obtain fuel additives (diethyl succinic acid, DES) and/or fuel intermediates.

A feruloyl esterase/cellulase integrated biological system for high-efficiency and toxic-chemical free isolation of tobacco based cellulose nanofibers

Tobacco based cellulose nanofiber (TCNF) is a novel nanocellulose that has recently been used to replace undesirable wood pulp fibers in the preparation of reconstructed tobacco sheets (RTS). However, given the strict requirements for controlling toxic chemical content in tobacco products, there is a global interest in developing a green, efficient, and toxic-chemical free approach to isolate TCNF from tobacco stem as a bioresource. In this study, we propose a creative and environmentally friendly method to efficiently and safely isolate TCNF from tobacco stem pulp, which involves integrated biological pretreatment followed by a facile mechanical defibrillation process. Feruloyl esterase is used to pretreat the stem pulp by disrupting the ether and ester bonds between lignin and polysaccharide carbohydrates within the fiber wall, which effectively facilitates cellulase hydrolysis and swelling of the stem pulp fiber, as well as the following mechanical shearing treatment for TCNF isolation. The results demonstrate that TCNF obtained by the comprehensive feruloyl esterase/cellulase/mechanical process exhibit uniform and well-dispersed nanofiber morphology, higher crystallinity, and stronger mechanical properties than those of the control. The addition of 0.5 % TCNF can replace wood pulp by 18 wt% ~ 25 wt% in the production of RTS samples while maintaining their reasonable strength properties.

Characterization of Gels and Films Produced from Pinhão Seed Coat Nanocellulose as a Potential Use for Wound Healing Dressings and Screening of Its Compounds towards Antitumour Effects.

The reuse of agro-industrial waste assumes great importance today. Pinhão is the seed of Araucaria angustifolia, which is native to the mountains of southern Brazil, Paraguay, and Argentina. The coat is a by-product of this seed and is rich in phenolic compounds. The present study aimed to use the residue as a precursor material for the production of nanocellulose through the mechanical defibrillation process and perform the characterization of the films and the gel to investigate the effect on the physical and regenerative properties when incorporated with polyvinyl alcohol (PVA). The modulus of elasticity was higher when the MFC of pinhão was added to the PVA. Film and gel had their cytotoxicity tested by MTT assay using 3T3 fibroblast and Schwann cancer cells, and a migration assay was also performed using the scratch test on HaCat keratinocyte cells. For the scratch test, film and gel samples with low concentration presented a complete scratch closure in 72 h. Molecular docking was performed and quercetin had the ideal interaction score values, so it was used with the PACAP protein which presented a slightly moderate interaction with the protein synthesis of Schwann cells, presenting compactness of the compound after 14 ns.

Preparation of a Conductive Cellulose Nanofiber-reinforced PVA Composite Film with Silver Nanowires Loading

We report herein a flexible, light and electrically conductive composite film based on polyvinyl alcohol (PVA) matrices. Cellulose nanofibers (CNFs) were used as reinforcement to improve the mechanical properties of the PVA. Addition of silver nanowires (AgNWs) was crucial in enhancing the thermal stability and conductivity of the resulting PVA/CNF-AgNWs composite. The CNFs were obtained through a mechanical defibrillation process and the AgNWs were synthesized via a solvothermal method. A simple casting method combined with a drop cast process was chosen for producing AgNW film on the surface of the composite. The PVA/CNF-AgNWs composite film obtained was superior to the PVA/CNF composite film in terms of thermal stability, tensile strength (up to 38.12 ± 0.53 N/mm 2) and conductivity (8.92 × 10−2 vs 9.46 × 10−12 S/m). These results highlight the potential application of the PVA/CNF-AgNWs composite as a candidate film for the production of flexible electronics.

Enzymatic coupled mechanical defibrillation process for the production of corn (Zea mays) cob nanofibrillated cellulose: preparation, characterization and evaluation as Pickering emulsifier for oil-in-water emulsion

Enzymatic coupled mechanical defibrillation process for the production of corn (Zea mays) cob nanofibrillated cellulose: preparation, characterization and evaluation as Pickering emulsifier for oil-in-water emulsion

Production and Characterization of Cellulose Nanofiber Slurries and Sheets for Biomedical Applications

Cellulose nanomaterials are produced employing a multitude of methodologies including electrospinning, bacterial generation, acid digestion, and a variety of mechanical defibrillation techniques; the morphology of the nanomaterial produced is specific to the production process. Feedstocks range from various forms of woody biomass, to fungi, and have a great impact on the resulting product. The mechanical defibrillation technique, such as that employed in the present work, continuously breaks down cellulose fibers suspended in water via segmentation and defibrillation through grinding and refining. The process is typically operated until a desired level of fines is achieved in the resultant slurry of cellulose nanofiber (CNF), alternatively known as cellulose nanofibril. Mechanical defibrillation processes can be built to produce several liters in a small batch system or up to tons per day in a continuous pilot scale refiner system. In the present work a continuous system was developed with the capacity to produce 14 L of cellulose nanofiber slurry with consistent specifications and in a manner compliant with GMP/GLP protocols in order to be amenable to biomedical applications. The system was constructed within an ISO class 7 cleanroom and refining was performed on bleached softwood pulp suspension in purified water. This manuscript details the continuous grinding system, the processes employed to produce cellulose nanofiber, and characterizes the resultant cellulose nanofiber slurry and sheets formed from the slurry.

Abstract 10508: Variation in Community and Emergency Medical Systems Processes for Out-of-Hospital Cardiac Arrest During the COVID-19 Pandemic: A Systematic Review and Meta-Analysis

Introduction: Bystander cardiopulmonary resuscitation (B-CPR) with early defibrillation and immediate emergency medical services (EMS) care significantly increases a victim's chance of survival from out-of-hospital sudden cardiac arrest (OHCA). Few studies have assessed the overall effect of the COVID-19 pandemic on the prehospital chain of survival. Objectives: We sought to quantify the effect of the COVID-19 pandemic on prehospital processes including B-CPR, bystander defibrillation, community characteristics, and EMS process measures. We hypothesized that B-CPR rates would decrease and OHCA occurring in the home would increase during the pandemic. Methods: We conducted a systematic review and meta-analysis of studies identified through 05/03/2021. We examined 5 bibliographic databases and searched terms including cardiac arrest, OHCA, and COVID-19. Data were abstracted and independently coded. Subgroup analysis and meta-regression analysis were performed. Our primary outcome was B-CPR; our secondary outcomes were community processes and EMS characteristics. Results: The original search yielded 966 articles; 20 articles were included in our analysis. Studies originated from 10 different countries and were retrospective in study design. There was no difference in B-CPR rates during COVID-19 compared to Pre-COVID-19 (OR: 0.94 (0.80-1.11), p=0.46). Patients had a 1.38 (1.11-1.71) higher likelihood of having an OHCA at home during COVID-19 compared to Pre-COVID-19 (p=0.01). Receipt of bystander defibrillation was significantly lower during COVID-19 compared to Pre-COVID-19 (OR: 0.65 (0.48-0.88), p=0.01). There was a significant increase in EMS call to arrival time during COVID-19 compared to Pre-COVID-19 (Mean difference in minutes= 0.27 (0.13-0.40), p<0.01). Statistical heterogeneity was moderate-to-high; findings were robust to sensitivity analyses with no publication bias detected. Conclusion: B-CPR rates remained unchanged during the pandemic, while OHCA in the home increased. Bystander defibrillation decreased, while EMS response time increased during the pandemic. These findings may inform future public programing, particularly to consider interventions to improve the prehospital chain of survival.

Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

The characteristics of cellulose nanofibers (CNFs) depend on many factors such as the raw material, type and intensity of the pre-treatment, and type and severity of the mechanical defibrillation process. The relationship among factors is complex but crucial in determining the final, fit-for-use CNF properties. This study aims to find the relationship between the CNF properties morphology, aspect ratio, nanofibrillation yield, transmittance and cationic demand, and the production process using bleached Aspen thermomechanical pulp as the raw material. Five different types of pretreatments were carried out and five different defibrillation intensities of high-pressure homogenization were evaluated. Pretreatments were: PFI refining at 20,000 revolutions, enzymatic hydrolysis with 80 and 240 g of enzyme per ton of dry pulp and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)–mediated oxidation with 5 and 15 mmol of NaClO per gram of dry pulp. From the twenty-five different procedures evaluated, results show that both the pretreatment and the severity of the high-pressure homogenization determined both the fibrillation yield and the CNF morphology. Moreover, the main properties of CNFs (cationic demand, yield, transmittance and aspect ratio) can be estimated from the carboxylic content of the pretreated pulp, which would facilitate the control of the CNF production and their tuning according to the production needs.

Funnel control for the monodomain equations with the FitzHugh-Nagumo model

We consider a nonlinear reaction diffusion system of parabolic type known as the monodomain equations, which model the interaction of the electric current in a cell. Together with the FitzHugh-Nagumo model for the nonlinearity they represent defibrillation processes of the human heart. We study a fairly general type with co-located inputs and outputs describing both boundary and distributed control and observation. The control objective is output trajectory tracking with prescribed performance. To achieve this we employ the funnel controller, which is model-free and of low complexity. The controller introduces a nonlinear and time-varying term in the closed-loop system, for which we prove existence and uniqueness of solutions. Additionally, exploiting the parabolic nature of the problem, we obtain Hölder continuity of the state, inputs and outputs. We illustrate our results by a simulation of a standard test example for the termination of reentry waves.

Role of Surface Chemistry in the In Vitro Lung Response to Nanofibrillated Cellulose.

Wood-derived nanofibrillated cellulose (NFC) has emerged as a sustainable material with a wide range of applications and increasing presence in the market. Surface charges are introduced during the preparation of NFC to facilitate the defibrillation process, which may also alter the toxicological properties of NFC. In the present study, we examined the in vitro toxicity of NFCs with five surface chemistries: nonfunctionalized, carboxymethylated, phosphorylated, sulfoethylated, and hydroxypropyltrimethylammonium-substituted. The NFC samples were characterized for surface functional group density, surface charge, and fiber morphology. Fibril aggregates predominated in the nonfunctionalized NFC, while individual nanofibrils were observed in the functionalized NFCs. Differences in surface group density among the functionalized NFCs were reflected in the fiber thickness of these samples. In human bronchial epithelial (BEAS-2B) cells, all NFCs showed low cytotoxicity (CellTiter-GloVR luminescent cell viability assay) which never exceeded 10% at any exposure time. None of the NFCs induced genotoxic effects, as evaluated by the alkaline comet assay and the cytokinesis-block micronucleus assay. The nonfunctionalized and carboxymethylated NFCs were able to increase intracellular reactive oxygen species (ROS) formation (chloromethyl derivative of 2′,7′-dichlorodihydrofluorescein diacetate assay). However, ROS induction did not result in increased DNA or chromosome damage.

Effects of Phosphorylation Duration on the Jute Extracted Cellulose Nanofibrils Using Ultra‐sonication

AbstractThe pretreatment process for the extraction of cellulose nanofibrils (CNFs) has been attracting the awareness of researchers. However, toxicity, complicated multistep procedures, and the use of costly chemicals are still some problems for chemical modification of cellulose fibers during the CNFs production. In this work, the phosphorylation reaction is introduced to pretreat jute fibers to extract CNFs with tiny diameter, and then the physicochemical properties of the obtained CNFs are analyzed. Experimental results exhibit that the phosphorylation process can affect the overall defibrillation process and the structure as well as properties of the involved products. This study also reports that the phosphorylation efficiency can be influenced by the existence of water, absence of urea, high temperature, and reaction duration. Even at a low degree of substitution, the phosphorylated CNFs exhibit better thermal stability and higher residual char compared to raw jute at 700 °C.

Auto Analysis of Defibrillation Process Based on Wavelet Transform

Sudden cardiac arrest is a situation in which the heart stop pumping the blood. Ventricular fibrillation and ventricular tachycardia are the major causes that lead to cardiac arrest. To treat sudden cardiac, a defibrillator device is used to return the heart to its normal sinus rhythm. There are several types of defibrillator, such as the manual type, which has many disadvantages since it requires the physician‘s instruction to determine the patient state and the amount of joule required; therefore, it is preferable to use auto defibrillator. In this paper propose to design a flyback converter which is the basic part of the defibrillator with a controller in feedback which can make a comparison between normal and abnormal ECG signals and give appropriate decision to defibrillator, simultaneously, the source of ECG signals will be taken from Physio bank database, then processed in Matlab for removing different types of noise and get a peak of signal, heart rate, in order to determine the patient state and required level of the shock. This design has accuracy 95 % with an error detection rate 5%.

Improving cellulose nanofibrillation of non-wood fiber using alkaline and bleaching pre-treatments

This study aimed to investigate the effect of alkaline and bleaching pre-treatments on nanofibrillation of jute fibers and on mechanical performance of the ensuing cellulose films. Fibers were submitted to mild or strong alkaline pre-treatments. Then, only after mild alkaline pre-treatment, the fibers were pre-treated with two different bleaching pathways. Succeeding, cellulose nanofibrils were produced by mechanical defibrillation of the pre-treated fibers, while cellulose films were obtained by dewatering (suction) of the cellulose suspensions. Commercial bleached wood (Eucalyptus and Pinus) pulps were used as reference sources of cellulose fibers. Transmission electron microscopy (TEM) was used to investigate the morphology of the obtained cellulose nanofibrils. Cellulose films were compared by their Tensile properties. Defibrillation process was highly influenced by chemical pre-treatments. By the morphological analyses, the most effective nanofibrillation was observed for fibers pre-treated with tetraacetylethylenediamine (TAED), leading to nanofibrils with average diameter of around 20 nm. The crystalline index (CI) was higher for nanofibrils from pre-treated fibers (CI > 80%) when compared to the raw fibers (CI = 61%). Jute fibers pre-treated with TAED bleaching led to higher nanofibrillation, resulting on films with higher Tensile strength and Young's modulus, which were similar to mechanical properties of those from commercial wood pulp.

Functionalized gold and silver nanoparticles modulate amyloid fibrillation, defibrillation and cytotoxicity of lysozyme via altering protein surface character

Although small size and tunable surface properties of metal nanoparticles such as gold and silver (AuNP, AgNP) have been explored in many biomedical applications, their effect on protein amyloid fibrillation and defibrillation has partly been investigated. Here, we synthesized starch and polyethylene glycol (PEG) functionalized AuNP and AgNP and explored their effect on amyloid fibrillation, defibrillation and cytotoxicity of hen egg white lysozyme (HEWL) as a model protein. Our experimental results revealed that lower concentration of PEGylated NPs (0.1–1 μM) exhibited higher anti-amyloid activity than starch capped NPs while higher concentration (5–20 μM), however showed nearly equal effect for both. Such inhibiting properties were attributed to the modulation of surface charge, surface hydrophobicity and capping agent of NPs. We further observed NP-mediated profound inhibition of fibril formation only during nucleation phase of amyloid growth. Defibrillation study of HEWL amyloid further revealed that starch functionalized NPs can defibrillate more efficiently than PEGylated NPs. When cytotoxicity of amyloid was assessed in mice neural (N2a) and human keratinocytes cells (HaCaT), amyloid samples prepared with NPs showed much reduced cytotoxicity compared to the untreated sample. Experimental results further showed that the reduction of cytotoxicity by NPs was mediated via preventing free radical generation. Overall, we concluded that appropriate selection of core material, surface modification and administration time of NP might be the key in inhibiting amyloid fibrillation and triggering defibrillation process of HEWL effectively.

Preparation of cellulose nanofibers by TEMPO-oxidation of bleached chemi-thermomechanical pulp for cement applications

Hardwood bleached chemi-thermomechanical pulp (BCTMP) was converted to cellulose nanofibers by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) catalyzed oxidization along with mechanical defibrillation process. The TEMPO reaction was evaluated based on the delignification, carboxylate content of cellulose and the yield of the insoluble component. Cellulose nanofibers were characterized by conductometry, Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA) as well as X-ray diffraction (XRD) techniques. Minimum 10 mmol/g NaClO addition was needed to obtain meaningful carboxylate content and easy defibrillation by using high shear mixing. TEMPO-catalyzed oxidization process removed 74% of pentosans and 80% of lignin from bleached chemi-thermomechanical hardwood pulp while 13% of cellulose was also lost. CNF with 1.44 mmol/g carboxylate content resulted high level of water retention (13.4 g/g fiber) Cellulose nanofibers were used in cementitious mixtures. CNF with carboxyl groups resulted in better flow control in wet cement paste and reduced the crack growth in concrete.

Effects of residual lignin on mechanical defibrillation process of cellulosic fiber for producing lignocellulose nanofibrils

High (14.9%), medium (2.4%) and low (0.1%) lignin-containing cellulosic fibers were processed through a micro-grinding method to mechanically produce lignocellulose nanofibrils (LCNFs). Effects of residual lignin on the mechanical defibrillation process were investigated in terms of the nanofibrils yields, the diameters of resultant LCNFs and the micro-grinding energy consumption. The results showed that the residual lignin delayed the initial defibrillation of cellulosic fibers due to its physical barrier. However, the residual lignin eventually facilitated the defibrillation and improved the maximum nanofibrils yields by 17.9–30.8%, and greatly reduced the diameters of the resultant LCNFs from 32.9 ± 7.7 to 9.2 ± 3.3 nm. The effects of lignin on counteracting the recombination reactions between the highly reactive cellulose radicals and hindering the aggregation of defibrillated fibrils through reducing the inter-fibrillar hydrogen bonding presumably resulted in the better eventual defibrillation of cellulosic fibrils.

How the surface wettability and modulus of elasticity of the Amazonian paricá nanofibrils films are affected by the chemical changes of the natural fibers

The use of natural resources for the production of nanostructured cellulosic films of high quality could reduce pollution and raw material costs for cellulose industry. This work provides innovative information about the use of Amazonian species not explored in studies involving the production of nanostructured films, as well as the evaluation of important characteristics that may be decisive for the destination of the product. The aim of this study was to modify Schizolobium parahyba var. amazonicum (parica) waste fibers through alkaline (NaOH) and bleaching (NaClO2) treatments for cellulose nanofibrils (CNFs) production and evaluate the characteristics of the nanofibrils and the surface as well as the mechanical resistance of the films obtained. The alkaline treatment was carried out with sodium hydroxide (5% NaOH solution (w/v); 2 h), while the bleaching was performed using sodium chlorite and glacial acetic acid (1.5 g NaClO2; 10 drops of glacial acetic acid; 1 h). The treatments were performed in sequence, producing nanofibrils after alkaline treatment and after bleaching. Lignin content did not change with the alkaline treatment, but it significantly decreased with bleaching (from 26.1 to 6.8%). Hemicelluloses content decreased with the sequence of treatments. FTIR results showed that the mechanical defibrillation caused disruption of the fiber bonds. The temperature of thermal degradation observed in DTG analysis increased from the natural fibers (243 °C) to alkaline + bleached fibers (255 °C). The defibrillation process led to higher thermal stability of the alkaline + bleached nanofibrils in comparison to fibers. Moreover, films were prepared from the obtained CNFs and evaluated by the mechanical properties and surface contact angle. The mechanical properties showed values of 6.93 ± 0.18 GPa for modulus of elasticity (MOE) for the films produced from material which was submitted to the bleaching treatment. The results highlighted a more hydrophobic surface of the film produced with the CNFs generated from the bleached fibers. The results of mechanical properties showed the superiority of the films produced from the alkaline + bleached fibers.

The Isolation of Nanofibre Cellulose from Oil Palm Empty Fruit Bunch Via Steam Explosion and Hydrolysis with HCl 10%

Cellulose nanofibrils were obtained from oil palm empty fruit bunch using steam explosion and hydrolized with 10% solution of HCl. Steam explosion coupled with acid hydrolysis pretreatment on the oil palm empty fruit bunch was very effective in the depolymerization and defibrillation process of the fibre to produce fibers in nanodimension. Structural analysis of steam exploded fibers was determined by Fourier Transform Infrared (FT-IR) spectroscopy. Thermal stability of cellulose measured using image analysis software image J. Characterization of the fibers by TEM and SEM displayed that fiber diameter decreases with mechanical-chemical treatment and final nanofibril size was 20-30 nm. FT-IR and TGA data confirmed the removal of hemicellulose and lignin during the chemical treatment process.