Haemocompatibility and ion exchange capability of nanocellulose polypyrrole membranes intended for blood purification

Sulfonic acid functionalized cellulose-derived (nano)materials: Synthesis and application

The preparation/application of heterogeneous (nano)materials from natural resources has currently become increasingly fascinating for researchers. Cellulose is the most abundant renewable polysaccharide on earth. The unique physicochemical, structural, biological, and environmental properties of this natural biopolymer have led to its increased application in many fields. The more desirable features of cellulose-based (nano)materials such as biodegradability, renewability, biocompatibility, cost-effectiveness, simplicity of preparation, environmentally friendly nature, and widespread range of applications have converted them into promising compounds in medicine, catalysis, biofuel cells, and water/wastewater treatment processes. Functionalized cellulose-based (nano)materials containing sulfonic acid groups may prove to be one of the most promising sustainable bio(nano)materials of modern times in the field of cellulose science and (nano)technology owing to their intrinsic features, high crystallinity, high specific surface area, abundance, reactivity, and recyclability. In this review, the developments in the application of sulfonated cellulose-based (nano)materials containing sulfonic acid (-SO3H) groups in catalysis, water purification, biological/biomedical, environmental, and fuel cell applications have been reported. This review provides an overview of the methods used to chemically modify cellulose and/or cellulose derivatives in different forms, including nanocrystals, hydrogels, films/membranes, and (nano)composites/blends by introducing sulfonate groups on the cellulose backbone, focusing on diverse sulfonating agents utilized and substitution regioselectivity, and highlights their potential applications in different industries for the generation of alternative energies and products.

Preparation of Cellulose Nanocrystals from Jujube Cores by Fractional Purification

Jujube cores are fiber-rich industrial waste. Dewaxing, alkali treatment, bleaching, and sulfuric acid hydrolysis were used to generate cellulose nanocrystals (CNCs) from the jujube cores in this study. The morphological, structural, crystallinity, and thermal properties of the fibers were investigated using FE-SEM, TEM, AFM, FT-IR, XRD, and TGA under various processes. CNCs’ zeta (ζ) potential and water contact angle (WAC) were also investigated. The findings demonstrate that non-fibrous components were effectively removed, and the fiber particles shrunk over time because of many activities. CNCs had a rod-like shape, with a length of 205.7 ± 52.4 nm and a 20.5 aspect ratio. The crystal structure of cellulose Iβ was preserved by the CNCs, and the crystallinity was 72.36%. The temperature of the fibers’ thermal degradation lowered during the operations, although CNCs still had outstanding thermal stability (>200 °C). Aside from the CNCs, the aqueous suspension of CNCs was slightly agglomerated; thus, the zeta (ζ) potential of the CNCs’ suspension was −23.72 ± 1.7 mV, and the powder had high hydrophilicity. This research will be valuable to individuals who want to explore the possibility for CNCs made of jujube cores.

Role of nanocellulose in industrial and pharmaceutical sectors - A review

Lignocellulosic biomass from agricultural residues serves as the critical component to replace synthetic polymeric materials in the coming future. Agricultural residues can be used to obtain cellulose by delignification followed by bleaching. Further, cellulose is converted into nanocellulose by various methods. Nanocellulose is used in multiple pharmaceutical applications as a polymer in hydrogels, transdermal drug delivery systems, aerogels, wound healing dressing materials, as superdisintegrants in fast dissolving tablets, emulgel, microparticles, gels, foams, thickening agents, stabilizers, cosmetics, medical implants, tissue engineering, liposomes, food and composites, etc. This review provides detailed knowledge about the nature of nanocellulose regarding its high surface area, high polymerization, loading, and binding capacity of hydrophilic and hydrophobic active pharmaceutical ingredients and significance of various applications of nanocellulose. Biocompatible and non-toxic, it makes it an ideal material for applications in the biomedical field. A significant advantage is a biocompatibility, which is non-toxic for many biomedical applications.

Nanocellulose for Sustainable Water Purification

Nanocelluloses (NC) are nature-based sustainable biomaterials, which not only possess cellulosic properties but also have the important hallmarks of nanomaterials, such as large surface area, versatile reactive sites or functionalities, and scaffolding stability to host inorganic nanoparticles. This class of nanomaterials offers new opportunities for a broad spectrum of applications for clean water production that were once thought impractical. This Review covers substantial discussions based on evaluative judgments of the recent literature and technical advancements in the fields of coagulation/flocculation, adsorption, photocatalysis, and membrane filtration for water decontamination through proper understanding of fundamental knowledge of NC, such as purity, crystallinity, surface chemistry and charge, suspension rheology, morphology, mechanical properties, and film stability. To supplement these, discussions on low-cost and scalable NC extraction, new characterizations including solution small-angle X-ray scattering evaluation, and structure-property relationships of NC are also reviewed. Identifying knowledge gaps and drawing perspectives could generate guidance to overcome uncertainties associated with the adaptation of NC-enabled water purification technologies. Furthermore, the topics of simultaneous removal of multipollutants disposal and proper handling of post/spent NC are discussed. We believe NC-enabled remediation nanomaterials can be integrated into a broad range of water treatments, greatly improving the cost-effectiveness and sustainability of water purification.

Fabrication of Hollow Nanocones Membrane with an Extraordinary Surface Area as CO2 Sucker

Recently, more and more attention has been paid to the development of eco-friendly solid sorbents that are cost-effective, noncorrosive, have a high gas capacity, and have low renewable energy for CO₂ capture. Here, we claimed the fabrication of a three-dimensional (3D) film of hollow nanocones with a large surface area (949.5 m²/g), a large contact angle of 136.3°, and high surface energy. The synthetic technique is based on an electrochemical polymerization process followed by a novel and simple strategy for pulling off the formed layers as a membrane. Although the polymer-coated substrates were reported previously, the membrane formation has not been reported elsewhere. The detachable capability of the manufactured layer as a membrane braked the previous boundaries and allows the membrane’s uses in a wide range of applications. This 3D hollow nanocones membrane offer advantages over conventional ones in that they combine a π-electron-rich (aromatic ring), hydrophobicity, a large surface area, multiple amino groups, and a large pore volume. These substantial features are vital for CO₂ capturing and storage. Furthermore, the hydrophobicity characteristic and application of the formed polymer as a CO₂ sucker were investigated. These results demonstrated the potential of the synthesized 3D hollow polymer to be used for CO₂ capturing with a gas capacity of about 68 mg/g and regeneration ability without the need for heat up.

Recent Advances in the Synthesis of Nanocellulose Functionalized–Hybrid Membranes and Application in Water Quality Improvement

The increasing discharge of voluminous non or partially treated wastewaters characterized by complex contaminants poses significant ecological and health risks. Particularly, this practice impacts negatively on socio-economic, technological, industrial, and agricultural development. Therefore, effective control of water pollution is imperative. Over the past decade, membrane filtration has been established as an effective and commercially attractive technology for the separation and purification of water. The performance of membrane-based technologies relies on the intrinsic properties of the membrane barrier itself. As a result, the development of innovative techniques for the preparation of highly efficient membranes has received remarkable attention. Moreover, growing concerns related to cost-effective and greener technologies have induced the need for eco-friendly, renewable, biodegradable, and sustainable source materials for membrane fabrication. Recently, advances in nanotechnology have led to the development of new high-tech nanomaterials from natural polymers (e.g., cellulose) for the preparation of environmentally benign nanocomposite membranes. The synthesis of nanocomposite membranes using nanocelluloses (NCs) has become a prominent research field. This is attributed to the exceptional characteristics of these nanomaterials (NMs) namely; excellent and tuneable surface chemistry, high mechanical strength, low-cost, biodegradability, biocompatibility, and renewability. For this purpose, the current paper opens with a comprehensive yet concise description of the various types of NCs and their most broadly utilized production techniques. This is closely followed by a critical review of how NC substrates and their surface-modified versions affect the performance of the fabricated NC-based membranes in various filtration processes. Finally, the most recent processing technologies for the preparation of functionalized NCs-based composite membranes are discussed in detail and their hybrid characteristics relevant to membrane filtration processes are highlighted.

In-Vitro Hemocompatibility of Polyaniline Functionalized by Bioactive Molecules

Hemocompatibility is an essential prerequisite for the application of materials in the field of biomedicine and biosensing. In addition, mixed ionic and electronic conductivity of conducting polymers is an advantageous property for these applications. Heparin-like materials containing sulfate, sulfamic, and carboxylic groups may have an anticoagulation effect. Therefore, sodium dodecylbenzenesulfonate, 2-aminoethane-1-sulfonic acid and N-(2-acetamido)-2-aminoethanesulfonic acid were used for modification of the representative of conducting polymers, polyaniline, and the resulting products were studied in the context of interactions with human blood. The anticoagulation activity was then correlated to surface energy and conductivity of the materials. Results show that anticoagulation activity is highly affected by the presence of suitable functional groups originating from the used heparin-like substances, and by the properties of polyaniline polymer itself.

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.

Current State and New Trends in the Use of Cellulose Nanomaterials for Wastewater Treatment

Nanotechnology has been identified as having great potential for improving the efficiency of water prevention and purification while reducing costs. In this field, two applications of nanocellulose have generated attention and have proven to be a sound strategy as an adsorbent and as a membrane for the removal of contaminants. This potential is attributed to its high aspect ratio, high specific surface area, high capacity retention, and environmental inertness. In addition to the aforementioned advantages, the presence of active sites allows the incorporation of chemical moieties that may enhance the binding efficiency of pollutants to the surface. This review paper intends to understand how nanocellulose affects the adsorption behavior of water pollutants, e.g., heavy metal ions, microbes, dyes, and organic molecules, and is divided in two parts. First, a general overview of the different strategies for the preparation of nanocellulose is described, and its specific properties are reported. The second section reports some of its application as adsorbent nanomaterial or separation membrane. It appears that the use of nanocellulose for these applications is very promising for wastewater treatment industries.

Blood Compatibility of Sulfonated Cladophora Nanocellulose Beads

Sulfonated cellulose beads were prepared by oxidation of Cladophora nanocellulose to 2,3-dialdehyde cellulose followed by sulfonation using bisulfite. The physicochemical properties of the sulfonated beads, i.e., high surface area, high degree of oxidation, spherical shape, and the possibility of tailoring the porosity, make them interesting candidates for the development of immunosorbent platforms, including their application in extracorporeal blood treatments. A desired property for materials used in such applications is blood compatibility; therefore in the present work, we investigate the hemocompatibility of the sulfonated cellulose beads using an in vitro whole blood model. Complement system activation (C3a and sC5b-9 levels), coagulation activation (thrombin-antithrombin (TAT) levels) and hemolysis were evaluated after whole blood contact with the sulfonated beads and the results were compared with the values obtained with the unmodified Cladophora nanocellulose. Results showed that neither of the cellulosic materials presented hemolytic activity. A marked decrease in TAT levels was observed after blood contact with the sulfonated beads, compared with Cladophora nanocellulose. However, the chemical modification did not promote an improvement in Cladophora nanocellulose hemocompatibility in terms of complement system activation. Even though the sulfonated beads presented a significant reduction in pro-coagulant activity compared with the unmodified material, further modification strategies need to be investigated to control the complement activation by the cellulosic materials.

Separation and characterization of cellulose nanocrystals by multi-detector asymmetrical-flow field-flow fractionation

Cellulose nanocrystals (CNCs) are renewable, naturally derived polymeric nanomaterials receiving substantial attention for a wide range of potential applications. The recent availability of high quality reference materials will facilitate the development and validation of measurement methods needed to advance the scientific and commercial use of CNCs. In the present study, we demonstrate an optimized method to fractionate CNCs with narrow size dispersion based on asymmetrical-flow field-flow fractionation (AF4) coupled with on-line multi-angle light scattering (MALS), dynamic light scattering (DLS), and differential refractometry (dRI). A stable suspension of CNC (Certified Reference Material CNCD-1, National Research Council-Canada) in deionized water was prepared using a dispersion method provided by NRC and adopted from a protocol originally developed at the National Institute of Standards and Technology. The as-prepared material was initially characterized in batch mode to validate the NRC dispersion method. AF4 was then optimized for channel and cross flow, mobile phase composition, and injection volume, among other parameters. Additionally, suspensions containing (1.25-10) mg mL-1 CNC were injected directly into the dRI detector (off-line), yielding a dn/dc value of 0.148 ± 0.003 mL g-1. dRI was then used as an on-line mass sensitive detector to quantify recovery. Results show that maximum recovery (≈ 99%) was achieved under optimized conditions. The weight-averaged molar mass (Mw) was estimated at roughly 107 Da from a partial Zimm analysis. The optical radius of gyration, Rg, and the hydrodynamic radius, Rh, were measured during elution. The shape factor (Rg/Rh) ranged from 1.5 to 1.9 for the fractionated material, supporting an elongated or rod-like structure. To our knowledge, this is the first time that both the morphology and molar mass of CNCs have been directly measured for the full distribution of species. Finally, we developed and demonstrated a semi-preparatory fractionation method to separate CNCs at the milligram scale for off-line research and analysis.

Potentially Immunogenic Contaminants in Wood-Based and Bacterial Nanocellulose: Assessment of Endotoxin and (1,3)-β-d-Glucan Levels

Knowledge gaps in the biosafety data of the nanocellulose (NC) for biomedical use through various routes of administration call for closer look at health and exposure evaluation. This work evaluated the potentially immunogenic contaminants levels, for example, endotoxin and (1,3)-β-d-glucan, in four representative NCs, that is, wood-based NCs and bacterial cellulose (BC). The hot-water extracts were analyzed with ELISA assays, HPSEC-MALLS, GC, and NMR analysis. Varying levels of endotoxin and (1,3)-β-d-glucan contaminats were found in these widely used NCs. Although the β-(1,3)-d-glucan was not detected from the NMR spectra due to the small extract samples amount (2-7 mg), the anomerics and highly diastereotopic 6-CH₂ signals may suggest the presence of β-(1,4)-linkages with β-(1,6) branching in the polysaccharides of NCs' hot-water extracts, which were otherwise not detectable in the enzymatic assay. In all, the article highlights the importance of monitoring various water-soluble potentially immunogenic contaminants in NC for biomedical use.

Nanocellulose as a sustainable biomass material: structure, properties, present status and future prospects in biomedical applications

Nanocellulose, extracted from the most abundant biomass material cellulose, has proved to be an environmentally friendly material with excellent mechanical performance owing to its unique nano-scaled structure, and has been used in a variety of applications as engineering and functional materials. The great biocompatibility and biodegradability, in particular, render nanocellulose promising in biomedical applications. In this review, the structure, treatment technology and properties of three different nanocellulose categories, i.e., nanofibrillated cellulose (NFC), nanocrystalline cellulose (NCC) and bacterial nanocellulose (BNC), are introduced and compared. The cytotoxicity, biocompatibility and frontier applications in biomedicine of the three nanocellulose categories were the focus and are detailed in each section. Future prospects concerning the cytotoxicity, applications and industrial production of nanocellulose are also discussed in the last section.

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

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

Transition from Bioinert to Bioactive Material by Tailoring the Biological Cell Response to Carboxylated Nanocellulose

This work presents an insight into the relationship between cell response and physicochemical properties of Cladophora cellulose (CC) by investigating the effect of CC functional group density on the response of model cell lines. CC was carboxylated by electrochemical TEMPO-mediated oxidation. By varying the amount of charge passed through the electrolysis setup, CC materials with different degrees of oxidation were obtained. The effect of carboxyl group density on the material's physicochemical properties was investigated together with the response of human dermal fibroblasts (hDF) and human osteoblastic cells (Saos-2) to the carboxylated CC films. The introduction of carboxyl groups resulted in CC films with decreased specific surface area and smaller total pore volume compared with the unmodified CC (u-CC). While u-CC films presented a porous network of randomly oriented fibers, a compact and aligned fiber pattern was depicted for the carboxylated-CC films. The decrease in surface area and total pore volume, and the orientation and aggregation of the fibers tended to augment parallel to the increase in the carboxyl group density. hDF and Saos-2 cells presented poor cell adhesion and spreading on u-CC, which gradually increased for the carboxylated CC as the degree of oxidation increased. It was found that a threshold value in carboxyl group density needs be reached to obtain a carboxylated-CC film with cytocompatibility comparable to commercial tissue culture material. Hence, this study demonstrates that a normally bioinert nanomaterial can be rendered bioactive by carefully tuning the density of charged groups on the material surface, a finding that not only may contribute to the fundamental understanding of biointerface phenomena, but also to the development of bioinert/bioactive materials.

Real-time detection of metal ions using conjugated polymer composite papers

Cellulose, a natural polymeric material, has widespread technical applications because of its inherent structural rigidity and high surface area. As a conjugated polymer, polypyrrole shows practical potential for a diverse and promising range of future technologies. Here, we demonstrate a strategy for the real-time detection and removal of metal ions with polypyrrole/cellulose (PPCL) composite papers in solution. Simply, the conjugated polymer papers had different chemical/physical properties by applying different potentials to them, which resulted in differentiable response patterns and adsorption efficiencies for individual metal ions. First, large-area PPCL papers with a diameter of 5 cm were readily obtained via vapor deposition polymerization. The papers exhibited both mechanical flexibility and robustness, in which polypyrrole retained its redox property perfectly. The ability of the PPCL papers to recognize metal ions was examined in static and flow cells, in which real-time current change was monitored at five different applied potentials (+1, +0.5, 0, -0.5, and -1 V vs. Ag/AgCl). Distinguishable signals in the PPCL paper responses were observed for individual metal ions through principal component analysis. Particularly, the PPCL papers yielded unique signatures for three metal ions, Hg(ii), Ag(i), and Cr(iii), even in a real sample, groundwater. The sorption of metal ions by PPCL papers was examined in the flow system. The PPCL papers had a greatly superior adsorption efficiency for Hg(ii) compared to that of the other metal ions. With the strong demand for the development of inexpensive, flexible, light-weight, and environmentally friendly devices, the fascinating characteristics of these PPCL papers are likely to provide good opportunities for low-cost paper-based flexible or wearable devices.

Cellulose nanomaterials in water treatment technologies

Cellulose nanomaterials are naturally occurring with unique structural, mechanical and optical properties. While the paper and packaging, automotive, personal care, construction, and textiles industries have recognized cellulose nanomaterials' potential, we suggest cellulose nanomaterials have great untapped potential in water treatment technologies. In this review, we gather evidence of cellulose nanomaterials' beneficial role in environmental remediation and membranes for water filtration, including their high surface area-to-volume ratio, low environmental impact, high strength, functionalizability, and sustainability. We make direct comparison between cellulose nanomaterials and carbon nanotubes (CNTs) in terms of physical and chemical properties, production costs, use and disposal in order to show the potential of cellulose nanomaterials as a sustainable replacement for CNTs in water treatment technologies. Finally, we comment on the need for improved communication and collaboration across the myriad industries invested in cellulose nanomaterials production and development to achieve an efficient means to commercialization.

Citric Acid Cross-Linked Nanocellulose-Based Paper for Size-Exclusion Nanofiltration

This article explores the effect of cross-linking of nanocellulose with citric acid for the development of novel paper filters for potential application within nanofiltration, including sterile (virus) filtration. Cladophora cellulose paper sheets were cross-linked by first soaking in 16 wt % citric acid in the presence of 1 wt % sodium hypophosphate overnight and then curing at 160 °C for 10 min in a hot-press. The cross-linked paper filter samples were then characterized with FTIR, AFM, N₂ gas adsorption, and tensile strength analysis (dry and wet strength). The particle retention properties were further studied with respect to filtering of 20 nm Au nanoparticles with SEM and comparing the UV absorbance intensity of the starting solution and the filtrate. The wet strength of the paper filter was greatly improved following the cross-linking, although in the dry state, the paper becomes brittle. The improved wet strength of the paper filter enables increasing the pressure gradient applied for filtration without compromising the integrity of the filter. This is the first report in which a fully nature-derived paper filter is capable of removing tracer particles as small as 20 nm. It is concluded that citric acid cross-linking of nanocellulose is beneficial for developing paper based sterile (virus) removal industrial filters.

Parallel mechanisms of polypyrrole self-discharge in aqueous media

Self-discharge of oxidized polypyrrole is composed of two parallel self-discharge mechanisms and their relative contributions depend on pH and potential.

A size-exclusion nanocellulose filter paper for virus removal

This is the first time a 100% natural, unmodified nanofibrous polymer-based membrane is demonstrated capable of removing viruses solely based on the size-exclusion principle, with a log10 reduction value (LRV) ≥ 6.3 as limited by the assay lower detection limit and the feed virus titre, thereby matching the performance of industrial synthetic polymer virus removal filters.

Application of bedside continuous blood purification in patients with multiple organ dysfunction syndromes

BACKGROUND

The complications of systemic inflammatory response syndrome (SIRS) include acute lung injury, acute kidney injury, shock, and multiple organ dysfunction syndrome (MODS). In recent years, how to clear inflammatory mediators has become a hot topic in critical care medicine. Researchers hypothesize that continuous blood purification (CBP) can effectively eliminate a variety of inflammatory mediators which participate in the occurrence of MODS and adjust the immune imbalance. This study aimed to observe the effects of CBP in MODS patients.

METHODS

In this retrospective clinical study, a total of 38 MODS patients, 18 males and 20 females, were enrolled. After conventional therapy, all the patients received CBP. Biochemistry, blood gas analysis, oxygenation index, mean arterial blood pressure (MAP), acute physiology and chronic health evaluation (APACHE) II scores were monitored.

RESULTS

After CBP, the vital signs of patients were rapidly stable, and electrolyte disorders and acid-base imbalance were corrected. Renal function, blood gas, oxygenation index were all improved. MAP was increased, and APACHE II score was significantly decreased. All patients had good tolerance, stable hemodynamics, and no obvious adverse reaction on CBP compared with pre-CBP.

CONCLUSION

CBP can effectively clean toxins, correct electrolyte acid-base balance, and improve systemic inflammatory response syndrome and the organ function of MODS patients.

Is there a future for electrochemically assisted hemodialysis? Focus on the application of polypyrrole–nanocellulose composites

This work summarizes the various aspects of using electrochemically assisted solute removal techniques in hemodialysis with a focus on blood electrodialysis and electrochemically controlled uremic retention solute removal using polypyrrole. In particular, the feasibility of using highly porous conductive polypyrrole–Cladophora cellulose membranes for hemodialysis are overviewed as a part of our dedicated research efforts during the past 4 years. The potential benefits and the current limitations associated with using the electrochemically controlled uremic retention solute removal techniques are discussed in detail.

Tailoring porosities and electrochemical properties of composites composed of microfibrillated cellulose and polypyrrole

The porosities of composites of polypyrrole and nanocellulose can be tailored from 30 to 98% with ∼10% increments enabling the electrochemical behavior of the materials to be readily controlled.

Obstacles in haemocompatibility testing

ISO 10993-4 is an international standard describing the methods of testing of medical devices for interactions with blood for regulatory purpose. The complexity of blood responses to biomaterial surfaces and the variability of blood functions in different individuals and species pose difficulties in standardisation. Moreover, in vivo or in vitro testing, as well as the clinical relevance of certain findings, is still matter of debate. This review deals with the major remaining problems, including a brief explanation of surface interactions with blood, the current ISO 10993 requirements for testing, and the role of in vitro test models. The literature is reviewed on anticoagulation, shear rate, blood-air interfaces, incubation time, and the importance of evaluation of the surface area after blood contact. Two test categories deserve further attention: complement and platelet function, including the effects on platelets from adhesion proteins, venipuncture, and animal derived- blood. The material properties, hydrophilicity, and roughness, as well as reference materials, are discussed. Finally this review calls for completing the acceptance criteria in the ISO standard based on a panel of test results.

Theoretical Application of Irreversible (Nonequilibrium) Thermodynamic Principles to Enhance Solute Fluxes across Nanofabricated Hemodialysis Membranes

Objective. Nanotechnology has the potential to improve hemodialysis membrane technology. Thus, a major objective is to understand how to enhance toxic solute fluxes across these membranes. The aim of this concept building study is to review the application of irreversible thermodynamic (IT) to solute fluxes. Methods. We expanded the application of the Nernst-Planck equation to include the Kedem-Katchalsky equation, pH, membrane thickness, pore size, and electric potential as variables. Results. (1) Reducing the membrane's thickness from 25 μm to 25 nm increased the flux of creatinine, β₂-microglobulin, and tumor necrosis factor-α (TNF-α) by a thousand times but prevented completely albumin flux, (2) applying an electric potential of 50–400 mV across the membrane enhanced the flux of the respective molecules by 71.167 × 10⁻³, 38.7905 × 10⁻⁸, and 0.595 × 10⁻¹³ mol/s, and (3) changing the pH from 7.35 to 7.42 altered the fluxes minimally. Conclusions. The results supported an argument to investigate the application of IT to study forces of fluxes across membranes. Reducing the membrane's thickness—together with the application of an electrical potential—qualities achievable by nanotechnology, can enhance the removal of uremic toxins by many folds. However, changing the pH at a specific membrane thickness does not affect the flux significantly.