Wearable and implantable artificial kidney devices for end-stage kidney disease treatment: Current status and review.

BACKGROUND: Chronic kidney disease (CKD) is a major cause of early death worldwide. By 2030, 14.5 million people will have end-stage kidney disease (ESKD, or CKD stage 5), yet only 5.4 million will receive kidney replacement therapy (KRT) due to economic, social, and political factors. Even for those who are offered KRT by various means of dialysis, the life expectancy remains far too low. OBSERVATION: Researchers from different fields of artificial organs collaborate to overcome the challenges of creating products such as Wearable and/or Implantable Artificial Kidneys capable of providing long-term effective physiologic kidney functions such as removal of uremic toxins, electrolyte homeostasis, and fluid regulation. A focus should be to develop easily accessible, safe, and inexpensive KRT options that enable a good quality of life and will also be available for patients in less-developed regions of the world. CONCLUSIONS: Hence, it is required to discuss some of the limits and burdens of transplantation and different techniques of dialysis, including those performed at home. Furthermore, hurdles must be considered and overcome to develop wearable and implantable artificial kidney devices that can help to improve the quality of life and life expectancy of patients with CKD.

The Signaling Pathways Induced by Exosomes in Promoting Diabetic Wound Healing: A Mini-Review.

Impaired healing of diabetic wounds harms patients' quality of life and even leads to disability and death, which is an urgent issue to be solved clinically. Despite the great progress that has been achieved, it remains a worldwide challenge to develop effective therapeutic treatments for diabetic wounds. Recently, exosomes have attracted special attention because they can be involved in immune response, antigen presentation, cell migration, cell differentiation, tumor invasion and other processes. Meanwhile, exosomes have been proven to hold great potential in the treatment of diabetic wounds. Mechanistic studies of exosomes based on signaling pathways could not only help to uncover the mechanisms by which exosomes promote diabetic wound healing but could also provide a theoretical basis for the clinical application of exosomes. Herein, our mini-review aims to summarize the progress of research on the use of various exosomes derived from different cell types to promote diabetic wound healing, with a focus on the classical signaling pathways, including PI3K/Akt, Wnt, NF-κB, MAPK, Notch, Nrf2, HIF-1α/VEGF and TGF-ß/Smad. The results show that exosomes could regulate these signaling pathways to down-regulate inflammation, reduce oxidative stress, increase angiogenesis, promote fibroblast proliferation, induce re-epithelization and inhibit scar formation, making exosomes attractive candidates for the treatment of diabetic wounds.

Effect of metal ions on the physical properties of multilayers from hyaluronan and chitosan, and the adhesion, growth and adipogenic differentiation of multipotent mouse fibroblasts.

Polyelectrolyte multilayers (PEMs) consisting of the polysaccharides hyaluronic acid (HA) as the polyanion and chitosan (Chi) as the polycation were prepared with layer-by-layer technique (LbL). The [Chi/HA]5 multilayers were exposed to solutions of metal ions (Ca2+, Co2+, Cu2+ and Fe3+). Binding of metal ions to [Chi/HA]5 multilayers by the formation of complexes with functional groups of polysaccharides modulates their physical properties and the bioactivity of PEMs with regard to the adhesion and function of multipotent murine C3H10T1/2 embryonic fibroblasts. Characterization of multilayer formation and surface properties using different analytical methods demonstrates changes in the wetting, surface potential and mechanical properties of multilayers depending on the concentration and type of metal ion. Most interestingly, it is observed that Fe3+ metal ions greatly promote adhesion and spreading of C3H10T1/2 cells on the low adhesive [Chi/HA]5 PEM system. The application of intermediate concentrations of Cu2+, Ca2+ and Co2+ as well as low concentrations of Fe3+ to PEMs also results in increased cell spreading. Moreover, it can be shown that complex formation of PEMs with Cu2+ and Fe3+ ions leads to increased metabolic activity in cells after 24 h and induces cell differentiation towards adipocytes in the absence of any additional adipogenic media supplements. Overall, complex formation of [Chi/HA]5 PEM with metal ions like Cu2+ and Fe3+ represents an interesting and cheap alternative to the use of growth factors for making cell-adhesive coatings and guiding stem cell differentiation on implants and scaffolds to regenerate connective-type of tissues.

Spectral analysis combined with nonlinear optical measurement of laser printed biopolymer composites comprising chitosan/SWCNT.

Biopolymer composites based on two types of chitosan (chitosan succinate and low-molecular weight chitosan) with single-walled carbon nanotubes (SWCNT) were created by laser printing. SWCNT have good dispersibility in chitosan solutions and therefore, can form relatively homogeneous films that was shown in scanning electron microscopy images. For the studies film composites were formed under the action of laser radiation on aqueous dispersion media. Study of the nonlinear optical process during the interaction of laser radiation with a disperse media has shown that low-molecular chitosan has a large nonlinear absorption coefficient of 17 cm/GW, while the addition of SWCNT lead to a significant increase up to 902 cm/GW. The threshold intensity for these samples was 5.5 MW/cm2 with nanotubes. If intensity exceeds the threshold value, nonlinear effects occur, which, in turn, lead to the transformation of a liquid into a solid phase. Characterization of films by FTIR and Raman spectroscopy indicated arising molecular interactions between chitosan and SWCNT detected as a small frequency shift and a change in the shape of radial breathing mode (RBM). The results indicate the possibility using aqueous dispersion media based on chitosan and SWCNT to create three-dimensional films and scaffolds for tissue engineering by laser printing.

Studies on the Mechanisms of Anti-Inflammatory Activity of Heparin- and Hyaluronan-Containing Multilayer Coatings-Targeting NF-κB Signalling Pathway.

The use of implants can be hampered by chronic inflammatory reactions, which may result in failure of the implanted device. To prevent such an outcome, the present study examines the anti-inflammatory properties of surface coatings made of either hyaluronic acid (HA) or heparin (Hep) in combination with chitosan (Chi) prepared as multilayers through the layer-by-layer (LbL) technique. The properties of glycosaminoglycan (GAG)-modified surfaces were characterized in terms of surface topography, thickness and wettability. Results showed a higher thickness and hydrophilicity after multilayer formation compared to poly (ethylene imine) control samples. Moreover, multilayers containing either HA or Hep dampened the inflammatory response visible by reduced adhesion, formation of multinucleated giant cells (MNGCs) and IL-1ß release, which was studied using THP-1 derived macrophages. Furthermore, investigations regarding the mechanism of anti-inflammatory activity of GAG were focused on nuclear transcription factor-кB (NF-κB)-related signal transduction. Immunofluorescence staining of the p65 subunit of NF-κB and immunoblotting were performed that showed a significant decrease in NF-κB level in macrophages on GAG-based multilayers. Additionally, the association of FITC-labelled GAG was evaluated by confocal laser scanning microscopy and flow cytometry showing that macrophages were able to associate with and take up HA and Hep. Overall, the Hep-based multilayers demonstrated the most suppressive effect making this system most promising to control macrophage activation after implantation of medical devices. The results provide an insight on the anti-inflammatory effects of GAG not only based on their physicochemical properties, but also related to their mechanism of action toward NF-κB signal transduction.

Recent Advances in Artificially Sulfated Polysaccharides for Applications in Cell Growth and Differentiation, Drug Delivery, and Tissue Engineering.

Artificially sulfated polysaccharides, as the mimetics of native heparin and heparan sulfate, are important bioactive compounds, since they show great potential for tuning crucial biological activities within living organisms. Herein, we summarize progress in the development of artificially sulfated polysaccharides, such as cellulose sulfate, chitosan sulfate, and other sulfated polysaccharides, with a particular focus on the fields of biomedical and bioengineering applications in the past ten years. Their effects on cell growth and differentiation, but also as building blocks for drug carriers and medical implants, are emphasized.

Anti-inflammatory Surface Coatings Based on Polyelectrolyte Multilayers of Heparin and Polycationic Nanoparticles of Naproxen-Bearing Polymeric Drugs.

Immune response to biomaterials can produce chronic inflammation and fibrosis leading to implant failure, which is related to the surface properties of the biomaterials. This work describes the preparation and characterization of polyelectrolyte multilayer (PEM) coatings that combine the anti-inflammatory activity of heparin as polyanion with the potential release of Naproxen, a nonsteroidal anti-inflammatory drug from polymeric nanoparticles (NP) with cationic surface charge. The polyelectrolyte multilayers were characterized by physical methods to estimate multilayer growth, thickness, zeta potential, and topography. It was found that multilayers with NP had negative zeta potentials and expressed a viscoelastic behavior, while studies of topography showed that nanoparticles formed continuous surface coatings. THP-1-derived macrophages were used to study short-term anti-inflammatory activity (time scale 48 h), showing that PEM that contained heparin reduced cell adhesion and IL1-ß secretion, when compared to those with polystyrenesulfonate, used as alternative polyanion in multilayer formation. On the other hand, the presence of NP in PEM was related to a reduced foreign body giant cell formation after 15 days, when compared to PEM that contained chitosan as alternative polycation, which suggests a long-term anti-inflammatory effect of Naproxen-containing nanoparticles. It was also shown that macrophages were able to take up NP from multilayers, which indicates a release of Naproxen by digestion of NP in the lysosomal compartment. These findings indicate that surface coatings composed of heparin and Naproxen-based NP on implants such as biosensors have the potential to attenuate foreign body reaction after implantation, which may improve the long-term functionality of implants.

Protective Effect of N-Arachidonoyl Glycine-GPR18 Signaling after Excitotoxical Lesion in Murine Organotypic Hippocampal Slice Cultures.

N-arachidonoyl glycine (NAGly) is an endocannabinoid involved in the regulation of different immune cells. It was shown to activate the GPR18 receptor, which was postulated to switch macrophages from cytotoxic to reparative. To study GPR18 expression and neuroprotection after NAGly treatment we used excitotoxically lesioned organotypic hippocampal slice cultures (OHSC). The effect of NAGly was also tested in isolated microglia and astrocytes as these cells play a crucial role during neuronal injury. In the present study, the GPR18 receptor was found in OHSC at mRNA level and was downregulated after N-Methyl-D-aspartate (NMDA) treatment at a single time point. Furthermore, treatment with NAGly reduced neuronal damage and this effect was abolished by GPR18 and cannabinoid receptor (CB)2 receptor antagonists. The activation but not motility of primary microglia and astrocytes was influenced when incubated with NAGly. However, NAGly alone reduced the phosphorylation of Akt but no changes in activation of the p44/42 and p38 MAPK and CREB pathways in BV2 cells could be observed. Given NAGly mediated actions we speculate that GPR18 and its ligand NAGly are modulators of glial and neuronal cells during neuronal damage.

pH Responsiveness of Multilayered Films and Membranes Made of Polysaccharides.

We investigated the pH-dependent properties of multilayered films made of chitosan (CHI) and alginate (ALG) and focused on their postassembly response to different pH environments using a quartz crystal microbalance with dissipation monitoring (QCM-D), swelling studies, ζ potential measurements, and dynamic mechanical analysis (DMA). In an acidic environment, the multilayers presented lower dissipation values and, consequently, higher moduli when compared with the values obtained for the pH used during the assembly (5.5). When the multilayers were exposed to alkaline environments, the opposite behavior occurred. These results were further corroborated by the ability of this multilayered system to exhibit a reversible swelling-deswelling behavior within the pH range from 3 to 9. The changes in the physicochemical properties of the multilayer system were gradual and different from those of individual solubilized polyelectrolytes. This behavior is related to electrostatic interactions between the ionizable groups combined with hydrogen bonding and hydrophobic interactions. Beyond the pH range of 3-9, the multilayers were stabilized by genipin cross-linking. The multilayered films also became more rigid while the pH responsiveness conferred by the ionizable moieties of the polyelectrolytes was preserved. This work demonstrates the versatility and feasibility of LbL methodology to generate inherently pH stimulus-responsive nanostructured films. Surface functionalization using pH responsiveness endows several biomedical applications with abilities such as drug delivery, diagnostics, microfluidics, biosensing, and biomimetic implantable membranes.

3-Substituted pyrazoles and 4-substituted triazoles as inhibitors of human 15-lipoxygenase-1.

Investigation of 1N-substituted pyrazole-3-carboxanilides as 15-lipoxygenase-1 (15-LOX-1) inhibitors demonstrated that the 1N-substituent was not essential for activity or selectivity. Additional halogen substituents on the pyrazole ring, however, increased activity. Further development led to triazole-4-carboxanilides and 2-(3-pyrazolyl) benzoxazoles, which are potent and selective 15-LOX-1 inhibitors.

Both hyaluronan and collagen type II keep proteoglycan 4 (lubricin) at the cartilage surface in a condition that provides low friction during boundary lubrication.

Wear resistant and ultralow friction in synovial joints is the outcome of a sophisticated synergy between the major macromolecules of the synovial fluid, e.g., hyaluronan (HA) and proteoglycan 4 (PRG4), with collagen type II fibrils and other non-collagenous macromolecules of the cartilage superficial zone (SZ). This study aimed at better understanding the mechanism of PRG4 localization at the cartilage surface. We show direct interactions between surface bound HA and freely floating PRG4 using the quartz crystal microbalance with dissipation (QCM-D). Freely floating PRG4 was also shown to bind with surface bound collagen type II fibrils. Albumin, the most abundant protein of the synovial fluid, effectively blocked the adsorption of PRG4 with HA, through interaction with C and N terminals on PRG4, but not that of PRG4 with collagen type II fibrils. The above results indicate that collagen type II fibrils strongly contribute in keeping PRG4 in the SZ during cartilage articulation in situ. Furthermore, PRG4 molecules adsorbed very well on mimicked SZ of absorbed HA molecules with entangled collagen type II fibrils and albumin was not able to block this interaction. In this last condition PRG4 adsorption resulted in a coefficient of friction (COF) of the same order of magnitude as the COF of natural cartilage, measured with an atomic force microscope in lateral mode.

Improved stability and cell response by intrinsic cross-linking of multilayers from collagen I and oxidized glycosaminoglycans.

Stability of surface coatings against environmental stress, such as pH, high ionic strength, mechanical forces, and so forth, is crucial for biomedical application of implants. Here, a novel extracellular-matrix-like polyelectrolyte multilayer (PEM) system composed of collagen I (Col I) and oxidized glycosaminoglycans (oGAGs) was stabilized by intrinsic cross-linking due to formation of imine bonds between aldehydes of oxidized chondroitin sulfate (oCS) or hyaluronan (oHA) and amino groups of Col I. It was also found that Col I contributed significantly more to overall mass in CS-Col I than in HA-Col I multilayer systems and fibrillized particularly in the presence of native and oxidized CS. Adhesion and proliferation studies with murine C3H10T1/2 embryonic fibroblasts demonstrated that covalent cross-linking of oGAG with Col I had no adverse effects on cell behavior. By contrast, it was found that cell size and polarization was more pronounced on oGAG-based multilayer systems, which corresponded also to the higher stiffness of cross-linked multilayers as observed by studies with quartz crystal microbalance (QCM). Overall, PEMs prepared from oGAG and Col I give rise to stable PEM constructs due to intrinsic cross-linking that may be useful for making bioactive coatings of implants and tissue engineering scaffolds.

Novel mineralized heparin-gelatin nanoparticles for potential application in tissue engineering of bone.

Nanoparticles (NPs) were prepared from succinylated gelatin (s-GL) cross-linked with aldehyde heparin (a-HEP) and used subsequently as a nano-template for the mineralization of hydroxyapatite (HAP). Gelatin was functionalized with succinyl groups that made it soluble at room temperature. Heparin was oxidized to generate aldehyde groups and then used as a cross-linker that can react with s-GL to form NPs via Schiff's base linkage. The polymer concentrations, feed molar ratios and pH conditions were varied to fabricate NPs suspension. NPs were obtained with a spheroid shape of an average size of 196 nm at pH 2.5 and 202 nm at pH 7.4. These NPs had a positive zeta potential of 7.3 ± 3.0 mV and a narrow distribution with PDI 0.123 at pH 2.5, while they had a negative zeta potential of -2.6 ± 0.3 mV and formed aggregates (PDI 0.257) at pH 7.4. The NPs prepared at pH 2.5 with a mean particle size of 196 nm were further used for mineralization studies. The mineralization process was mediated by solution without calcination at 37 °C. The HAP formed on NPs was analyzed by Fourier transform infrared spectroscopy and X-ray diffraction. HAP coated s-GL/a-HEP NPs developed in this study may be used in future as osteoinductive fillers enhancing the mechanical properties of injectable hydrogel or use as potential multifunctional device for nanotherapeutic approaches.

Functionalized Gelatin/Polysaccharide Hydrogels for Encapsulation of Hepatocytes.

Liver diseases represent a considerable burden to patients and healthcare systems. Hydrogels play an important role in the engineering of soft tissues and may be useful for embedding hepatocytes for different therapeutic interventions or the development of in vitro models to study the pathogenesis of liver diseases or testing of drugs. Here, we developed two types of hydrogels by crosslinking hydrazide-functionalized gelatin with either oxidized dialdehyde hyaluronan or alginate through the formation of hydrazone bonds. Gel formulations were studied through texture analysis and rheometry, showing mechanical properties comparable to those of liver tissue while also demonstrating long-term stability. The biocompatibility of hydrogels and their ability to host hepatocytes was studied in vitro in comparison to pure gelatin hydrogels crosslinked by transglutaminase using the hepatocellular line HepG2. It was found that HepG2 cells could be successfully embedded in the hydrogels, showing no signs of gel toxicity and proliferating in a 3D environment comparable to pure transglutaminase cross-linked gelatin hydrogels used as control. Altogether, hydrazide gelatin in combination with oxidized polysaccharides makes stable in situ gelling systems for the incorporation of hepatocytes, which may pave the way for use in liver tissue engineering and drug testing.

The Combination of Bioactive Herbal Compounds with Biomaterials for Regenerative Medicine.

Regenerative medicine aims to restore the function of diseased or damaged tissues and organs by cell therapy, gene therapy, and tissue engineering, along with the adjunctive application of bioactive molecules. Traditional bioactive molecules, such as growth factors and cytokines, have shown great potential in the regulation of cellular and tissue behavior, but have the disadvantages of limited source, high cost, short half-life, and side effects. In recent years, herbal compounds extracted from natural plants/herbs have gained increasing attention. This is not only because herbal compounds are easily obtained, inexpensive, mostly safe, and reliable, but also owing to their excellent effects, including anti-inflammatory, antibacterial, antioxidative, proangiogenic behavior and ability to promote stem cell differentiation. Such effects also play important roles in the processes related to tissue regeneration. Furthermore, the moieties of the herbal compounds can form physical or chemical bonds with the scaffolds, which contributes to improved mechanical strength and stability of the scaffolds. Thus, the incorporation of herbal compounds as bioactive molecules in biomaterials is a promising direction for future regenerative medicine applications. Herein, an overview on the use of bioactive herbal compounds combined with different biomaterial scaffolds for regenerative medicine application is presented. We first introduce the classification, structures, and properties of different herbal bioactive components and then provide a comprehensive survey on the use of bioactive herbal compounds to engineer scaffolds for tissue repair/regeneration of skin, cartilage, bone, neural, and heart tissues. Finally, we highlight the challenges and prospects for the future development of herbal scaffolds toward clinical translation. Overall, it is believed that the combination of bioactive herbal compounds with biomaterials could be a promising perspective for the next generation of regenerative medicine.

The European Polysaccharide Network of Excellence (EPNOE) research roadmap 2040: Advanced strategies for exploiting the vast potential of polysaccharides as renewable bioresources.

Polysaccharides are among the most abundant bioresources on earth and consequently need to play a pivotal role when addressing existential scientific challenges like climate change and the shift from fossil-based to sustainable biobased materials. The Research Roadmap 2040 of the European Polysaccharide Network of Excellence (EPNOE) provides an expert's view on how future research and development strategies need to evolve to fully exploit the vast potential of polysaccharides as renewable bioresources. It is addressed to academic researchers, companies, as well as policymakers and covers five strategic areas that are of great importance in the context of polysaccharide related research: (I) Materials & Engineering, (II) Food & Nutrition, (III) Biomedical Applications, (IV) Chemistry, Biology & Physics, and (V) Skills & Education. Each section summarizes the state of research, identifies challenges that are currently faced, project achievements and developments that are expected in the upcoming 20 years, and finally provides outlines on how future research activities need to evolve.

Nanoscaled surface patterns influence adhesion and growth of human dermal fibroblasts.

In general, there is a need for passivation of nanopatterned biomaterial surfaces if cells are intended to interact only with a feature of interest. For this reason self-assembled monolayers (SAM), varying in chain length, are used; they are highly effective in preventing protein adsorption or cell adhesion. In addition, a simple and cost-effective technique to design nanopatterns of various sizes and distances, the so-called nanosphere lithography (NSL), is discussed, which allows the control of cell adhesion and growth depending on the feature dimensions. Combining both techniques results in highly selective nanostructured surfaces, showing that single proteins selectively adsorb on activated nanopatterns. Additionally, adhesion and growth of normal human dermal fibroblasts (NHDF) is strongly affected by the nanostructure dimensions, and it is proven that fibronectin (FN) matrix formation of these cells is influenced, too. Moreover, the FN fibrils are linked to the hexagonally close-packed nanopatterns. As a result, the system presented here can be applied in tissue engineering and implant design due to the fact that the nanopattern dimensions give rise to further modifications and allow the introduction of chemical heterogeneity to guide stem cell differentiation in the future.

Bioinspired multiple-interaction model revealed in adsorption of low-density lipoprotein to surface containing saccharide and alkanesulfonate.

A new "multiple-interaction model" for low-density lipoprotein (LDL) adsorption to a specific surface containing saccharide and alkanesulfonate ligands is proposed. The model suggests that there are interactions of the saccharide component beyond electrostatic interactions of the alkanesulfonate component that both influence the LDL adsorption process. This concept of multiple interactions between saccharide and LDL was inspired by the similarity in structures of LDL receptors (LDLR), heparin, and heparans used in LDL-apheresis. The model was confirmed by SPR analysis by the adsorption maxima on SAM surfaces with different compositions of saccharide and alkanesulfonate and additionally by CD detection of the conformation of LDL when in contact with saccharide.

Effect of molecular composition of heparin and cellulose sulfate on multilayer formation and cell response.

Here, the layer-by-layer method was applied to assemble films from chitosan paired with either heparin or a semisynthetic cellulose sulfate (CS) that possessed a higher sulfation degree than heparin. Ion pairing was exploited during multilayer formation at pH 4, while hydrogen bonding is likely to occur at pH 9. Effects of polyanions and pH value during layer formation on multilayers properties were studied by surface plasmon resonance ("dry layer mass"), quartz crystal microbalance with dissipation monitoring ("wet layer mass"), water contact angle, and zeta potential measurements. Bioactivity of multilayers was studied regarding fibronectin adsorption and adhesion/proliferation of C2C12 myoblast cells. Layer growth and dry mass were higher for both polyanions at pH 4 when ion pairing occurred, while it decreased significantly with heparin at pH 9. By contrast, CS as polyanion resulted also in high layer growth and mass at pH 9, indicating a much stronger effect of hydrogen bonding between chitosan and CS. Water contact angle and zeta potential measurements indicated a more separated structure of multilayers from chitosan and heparin at pH 4, while CS led to a more fuzzy intermingled structure at both pH values. Cell behavior was highly dependent on pH during multilayer formation with heparin as polyanion and was closely related to fibronectin adsorption. By contrast, CS and chitosan did not show such dependency on pH value, where adhesion and growth of cells was high. Results of this study show that CS is an attractive candidate for multilayer formation that does not depend so strongly on pH during multilayer formation. In addition, such multilayer system also represents a good substrate for cell interactions despite the rather soft structure. As previous studies have shown specific interaction of CS with growth factors, multilayers from chitosan and CS may be of great interest for different biomedical applications.