Charged Alginate Research Articles

Catalytic Assembly of Peptides Mediated by Complex Coacervates.

The assembly of peptides is generally mediated by liquid-liquid phase separation, which enables control over assembly kinetics, final structure, and functions of peptide-based supramolecular materials. Modulating phase separation can alter the assembly kinetics of peptides by changing solvents or introducing external fields. Herein, we demonstrate that the assembly of peptides can be effectively catalyzed by complex coacervates. The negatively charged sodium alginate (SA) can form complex coacervates with the positively charged KLVFFAE (Aβ16-22, abbreviated as KE) peptide, thereby lowering the nucleation barrier and promoting the assembly of the peptide. As the binding affinity of SA-KE and the dosage of SA decrease, the system shifts from a relatively inefficient template-induced assembly to a highly efficient catalytic assembly before ultimately reverting to slow spontaneous assembly. Therefore, both the affinity as well as the stoichiometry do not follow the intuitive rule that "more is better", but rather there exists an optimal value that maximizes the rate of assembly.

A Facile and Rapid Immobilization Method of Titanium Dioxide-Alginate Composite for The Photocatalytic Removal of Reactive Black-5

A facile and rapid approach to immobilize nano-sized titanium dioxide (TiO2) using a renewable biopolymer (i.e. alginate) has been successfully demonstrated. TiO2 exhibits a positively charged surface in acidic environment due to the presence of hydroxyl groups. Meanwhile, alginate polymer is negatively charged at any pH due to the presence of carboxylic group in the polymer chain. The negatively charged alginate polymer and positively charged TiO2 formed composite instantaneously when the alginate polymer was introduced into the TiO2 nanoparticles suspension. The TiO2-alginate (TiO2-A) composite photocatalyst was characterized using thermogravimetric analysis (TGA), field emission-scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray (EDX) analysis and Fourier Transform Infrared (FTIR). Thermogravimetric analysis indicated that incorporating TiO2 into sodium alginate increases its decomposition temperature due to the stability of TiO2 at elevated temperatures, with the TiO2 content estimated in the composite being 55.6%, lower than the theoretical calculation of 62.8%. FTIR analysis revealed a shift in the peak of the carboxylic group of sodium alginate, suggesting composite formation through electrostatic interactions with TiO2 nanoparticles, while FESEM analysis showed that the TiO2-A composite surface exhibited more pores compared to protonated alginate. The TiO2-A composite was able to remove 90% of the Reactive Black 5 (RB5) in less than 200 min under Ultra-violet (UV) illumination. The optimal pH to remove RB5 was found to be pH 2 due strong electrostatic attraction of negatively charged RB5 on the positive surface of TiO2 nanoparticles. The photocatalyst can be recovered by simple separation method, i.e. gravitational settling, and reused for 10 consecutive cycles with efficiency greater than 90% consistently. The TiO2-A composite is a promising immobilized photocatalyst for practical application in wastewater treatment. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Enhanced interface bonding of hydrophobic encapsulated hydrogel fibers by mechanical interlocking structure: Toward anti-drying and anti-swelling strain sensors

Conductive hydrogel fibers with superior mechanical and electrical performance have been developed for flexible wearable electronics, but the inherent properties of hydrogels for dehydration in the atmosphere and underwater swelling limit its widespread application. In this work, a silicone rubber encapsulated hydrogel fiber with enhanced interface bonding, excellent mechanical and electrical properties was successfully developed, in which the core polyvinyl alcohol/sodium alginate hydrogel fiber was prepared by a continuous wet-spinning and the following freeze-thawing. The interlocking dual-network structure and the improved ion transport by negatively charged sodium alginate gave the core hydrogel fiber excellent strength of 4.15 MPa, elongation-at-break of 1531 % and electrical conductivity of 17.01 S·m−1. After encapsulation using a silicone rubber, the composite hydrogel fiber showed a low expansion rate underwater for 7 days of 1.00 ± 0.21 % and low weight loss in the air over 36 h of 38.67 ± 0.38 %. And the interface bonding of the core hydrogel fiber and silicone layer was enhanced by the bridging effect of amphiphilic stearic acid. Therefore, the composite hydrogel fiber demonstrated a great potential as a strain sensor for underwater communication to ensure the safety of individuals in an underwater environment.

Formation of chlorophyll–anionic polysaccharide complex coacervates to improve chlorophyll color stability: Thermodynamic and kinetic stability studies

Chlorophyll (Chl) is the predominant pigment in green plants that can act as a food color and possesses various functional activities. However, its instability and rapid degradation on heating compromise the sensory qualities of its products. This study aimed to enhance the heat resistance of Chl by forming complex coacervates with two negatively charged polysaccharides, sodium alginate (SA) and K-carrageenan (KC). Dynamic light scattering and scanning electron microscopy analyses confirmed the formation of coacervates between Chl and the polysaccharides, whereas Fourier-transform infrared spectroscopy revealed that hydrogen bonding and electrostatic attraction were the primary forces behind complex formation. Electron spin resonance and thermodynamic studies further revealed that these complexes bolstered the thermal stability of Chl, with a maximum improvement of 70.38 % in t1/2 and a reduction of 50.72 % in the degradation rate constant. In addition, the antioxidant capacity of Chl was enhanced up to 35 %. Therefore, this study offers a novel approach to Chl preservation and suggests a viable alternative to artificial pigments in food products.

Coacervation and aggregation in lysozyme/alginate mixtures

Upon electrostatic interaction, the mixture of oppositely charged macromolecules separates into a macromolecule-rich dense phase coexisting with a diluted phase. The associative interaction proceeds through either liquid-liquid phase separation (LLPS) forming complex coacervates or liquid-solid phase separation (LSPS) forming aggregates. We here investigate the assembly of the basic protein lysozyme (LYS) with the negatively charged polysaccharide alginate (ALG) at pH 7 in different conditions of mixing ratios, total concentration, and ionic strength using a droplet-based millifluidic device. Aggregation and coacervation are observed in this system by changing the salt concentration. A 3D phase diagram, with concentration of salt, lysozyme, and alginate as 3D coordinates, gives a thorough description of monophasic, liquid-solid, and liquid-liquid phase separation areas, and the regions where both solid and liquid phases coexist. The thermodynamic aspects behind these two kinds of complex formation are investigated using isothermal titration calorimetry (ITC). Aggregation is associated with a strong affinity between LYS and ALG, with a 100 LYS: 1 ALG stoichiometry ratio, whereas a decreased binding affinity between the two biopolymers leads to coacervation.

Decoupling Charge and Side Chain Effects in Hierarchical Organization of Cationic PFX Peptide and Alginate.

We have successfully created self-assembled membranes by combining positively charged (Pro-X-(Phe-X)5-Pro) PFX peptides with negatively charged alginate. These PFX/alginate membranes were formed by three different peptides that contain either X = Arginine (R), Histidine (H), or Ornithine (O) as their charged amino acid. The assemblies were compared to membranes that were previously reported by us composed of X = lysine (K). This study enabled us to elucidate the impact of amino acids' specific interactions on membrane formation. SEM, SAXS, and cryo-TEM measurements show that although K, R, H, and O may have a similar net charge, the specific traits of the charged amino acid is an essential factor in determining the hierarchical structure of alginate/PFX self-assembled membranes.

Infection‐responsive polysaccharide‐based drug‐loaded nano‐assembly for dual‐modal treatment against drug‐resistant bacterial lung infection

AbstractThe escalating issue of lung infections induced by multi‐drug resistant (MDR) bacteria is threatening human health. Thus, the development of efficient drug delivery systems is essential to eliminate MDR bacterial lung infections effectively. Herein, we designed inhalable drug‐loaded nano‐assemblies by the electrostatic interaction between negatively charged sodium alginate and a positively charged antibacterial polymer, quaternized polyethyleneimine (QPEI‐C6), as well as a kind of typical antibiotic for therapy of lung infection, azithromycin (AZT). By adjusting the feed ratios, we optimized the size of the nano‐assembly to approximately 200 nm (STQ12), which was beneficial for penetration through the mucus layer and biofilm. In the slightly acidic environment of the infected site, the nano‐assembly could dissemble responsively and release AZT and QPEI‐C6. Because of the combined bactericidal effect, STQ12 exhibited high bactericidal efficiency against MDR bacteria. In animal experiments, STQ12 showed notable efficacy against MDR bacterial lung infection. Gene transcriptomic results showed that the main effects of STQ12 against bacteria were through influencing the bacterial cell components and metabolic processes, and affecting their growth and reproduction. This work provides a promising strategy to treat MDR bacterium‐induced lower respiratory tract infections.

Recoverable and degradable carboxymethyl chitosan polyelectrolyte hydrogel film for ultra stable encapsulation of curcumin

Hydrogels have shown great potential for application in food science due to their diverse functionalities. However, most hydrogels inevitably contain toxic chemical cross-linking agent residues, posing serious food safety concerns. In this paper, a curcumin/sodium alginate/carboxymethyl chitosan hydrogels (CSCH) were prepared by self-assembly of two oppositely charged polysaccharides, carboxymethyl chitosan and sodium alginate, to form a three-dimensional network encapsulating curcumin for extending food shelf life. The network structure of the CSCH film confirmed by FTIR, XRD, and XPS was mainly formed by electrostatic interactions. The chemical stability of CSCH network encapsulated curcumin was 4.2 times greater than that of free curcumin, with excellent gas barrier, antimicrobial, antioxidant, and biosafety properties. It was found that CSCH films reduced dehydration, prevented nutrient loss, inhibited microbial growth, and lowered the respiration rate, which effectively maintained the quality of mango and prolonged its shelf-life up to 11 days. Notably, CSCH films possessed the properties of rapid recycling (10 mins) and biodegradability (53 days). This polysaccharide-based hydrogel film provides a viable strategy for the development of green and sustainable food packaging.

Gluing blood into adhesive gel by oppositely charged polysaccharide dry powder inspired by fibrin fibers coagulation mediator

Hemostatic powders that adapt to irregularly shaped wounds, allowing for easy application and stable storage, have gained popularity for first-aid hemorrhage control. However, traditional powders often provide weak thrombus support and exhibit limited tissue adhesion, making them susceptible to dislodgment by the bloodstream. Inspired by fibrin fibers coagulation mediator, we have developed a bi-component hemostatic powder composed of positively charged quaternized chitosan (QCS) and negatively charged catechol-modified alginate (Cat-SA). Upon application to the wound, the bi-component powders (QCS/Cat-SA) rapidly absorb plasma and dissolve into chains. These chains interact with each other to form a network, which can effectively bind and entraps clustered red blood cells and platelets, ultimately leading to the creation of a durable and robust thrombus. Significantly, these interconnected polymers adhere to the injury site, offering protection against thrombus disruption caused by the bloodstream. Benefiting from these synthetic properties, QCS/Cat-SA demonstrates superior hemostatic performance compared to commercial hemostatic powders like Celox™ in both arterial injuries and non-compressible liver puncture wounds. Importantly, QCS/Cat-SA exhibits excellent antibacterial activity, cytocompatibility, and hemocompatibility. These advantages of QCS/Cat-SA, including strong blood clotting, wet tissue adherence, antibacterial activity, biosafety, ease of use, and stable storage, make it a promising hemostatic agent for emergency situations.

Cohering Plasma into Adhesive Gel by Natural Biopolymer-Nanoparticle Hybrid Powder for Efficient Hemostasis and Wound Healing.

Hemostatic powder is commonly used in emergency bleeding control due to its suitability for irregularly shaped wounds, ease of use, and stable storage. However, traditional powder often has limited tissue adhesion and weak thrombus support, which makes it vulnerable to displacement by blood flow. Herein, we have developed a tricomponent hemostatic powder (MQS) composed of mesoporous bioactive glass nanoparticle (MBG), positively charged quaternized chitosan (QCS), and negatively charged catechol-modified alginate (SADA). Upon application to the wound, MBG with its high specific surface area quickly absorbs plasma, concentrating the blood coagulation factor. Simultaneously, the water-soluble QCS and SADA interact with each other and form a net, which can be further cross-linked by MBG. This network efficiently binds and entraps clustered blood coagulation factors, ultimately resulting in the formation of a durable and robust thrombus. Furthermore, the formed net adheres to the injury site, offering protection against thrombus disruption caused by the bloodstream. Benefiting from the synergistic effect of these three components, MQS demonstrates superior hemostatic performance compared to commercial hemostatic powders like Celox in both arterial injuries and noncompressible liver puncture wounds. Furthermore, MQS can effectively accelerate wound healing. In addition, MQS exhibits excellent antibacterial activity, cytocompatibility, and hemocompatibility. These advantages of MQS, including strong blood clotting, wet tissue adherence, antibacterial activity, wound healing ability, biosafety, ease of use, and stable storage, make it a promising hemostatic agent for emergency situations.

Constructing robust and anti-fouling superwettable membrane with layer-by-layer assembly of Fe(OH)3 colloid

Layer-by-layer (LBL) assembly method, with the advantages of simple operation and strong universality, has attracted much attention recently. However, the weak molecule-to-molecule and molecule-to-ion interactions have limited its development. During this work, the molecule-to-solid interaction was adopted and a robust LBL coating was achieved by alternately depositing positively charged Fe(OH)3 colloids and negatively charged sodium alginate molecules. The molecule-to-solid interaction could continuously regenerate under corrosive conditions due to water insolubility and the chemical stability of solids. When the electrostatic interaction was broken, the abundant chemically stable solids acted as anchors to immobilize the soluble molecules and maintain the stability of the LBL coating. The prepared superwettable membranes exhibited superior oil-in-water emulsion separation efficiency, anti-fouling properties, and chemical stability. Meanwhile, the separation performance survived one week's harsh environments of strong acid and alkali.

ITC study on the interaction of some bile salts with tragacanth, Arabic, and guar gums with potential cholesterol-lowering ability.

The urge of designing new safe and natural functional foods to control blood lipids and dispensable without the need of physician supervision, has increased especially after the coming into effect of the recent EU Commission regulation 2022/860, that regulates the consumption of "red yeast rice," made by fermentation of rice with Monascus purpureus, and perceived as a natural functional food, due to a health risk for frail consumers. The results of the present work are a part of the systematic study we are carrying out of the binding ability of some soluble dietary fibers (SDF) from different natural sources toward selected bile salts (BS). Measurements were carried out by isothermal titration calorimetry (ITC) with the idea to shed light on the mechanism, if any, by which they show cholesterol-lowering activity. Epidemiological studies are sometimes conflicting and offer only hypothesis about the mechanism of action, the most accredited being the reduction of reabsorption of BS in the gut. Previous measurements done on negatively charged pectin and alginate, showed specific binding interaction with monomer NaDC for pectin and no interaction at all for alginate. Chitosan, positively charged and soluble only at low pH, in 100 mM acetate buffer at pH = 3 shows strong exothermic interactions with NaTC and NaTDC. Here we considered two plant exudates (Arabic gum and tragacanth gum) and guar gum, extracted from guar beans, and their interaction with the same bile salts. ITC measurements do not evidence specific interactions between gums and the studied BS, so that their cholesterol lowering ability, if any, is due to a different mechanism very probably bound to the viscosity increase. Moreover, the addition of NaC, the most abundant BS in the bile, at very low concentration (under the cmc) causes a structural change of the solution. The obtained results seem to corroborate the hypothesis that the cholesterol lowering activity is related to the increase in viscosity of guar solution favored by NaC, the major component of the bile.

Complexation-Induced Resolution Enhancement Pleiotropic Small Diameter Vascular Constructs with Superior Antibacterial and Angiogenesis Properties.

3D printing has been widely applied for preparing artificial blood vessels, which will bring innovation to cardiovascular disorder intervention. However, the printing resolution and anti-infection properties of small-diameter vessels (Φ < 6mm) have been challenging in 3D printing. The primary objective of this research is to design a novel coaxial 3D-printing postprocessing method for preparing small-size blood vessels with improved antibacterial and angiogenesis properties. The coaxial printing resolution can be more conveniently improved. Negatively charged polyvinyl alcohol (PVA) and alginate (Alg) interpenetrating networks artificial vessels are immersed in positively charged chitosan (CTS) solution. Rapid dimensional shrinkage takes place on its outer surface through electrostatic interactions. The maximum shrinkage size of wall thickness can reach 61.2%. The vessels demonstrate strong antibacterial properties against Escherichia coli (98.8 ± 0.5%) and Staphylococcus aureus (97.6 ± 1.4%). In rat dorsal skin grafting experiments, Cu2+ can promote angiogenesis by regulating hypoxia-inducible factor-1 pathway. No artificial blood vessel blockage occurs after 5 days of blood circulation in vitro.

Effects of Salt on Phase Behavior and Rheological Properties of Alginate-Chitosan Polyelectrolyte Complexes.

Oppositely charged polyelectrolytes often form polyelectrolyte complexes (PECs) due to the association through electrostatic interactions. Obtaining PECs using natural, biocompatible polyelectrolytes is of interest in the food, pharmaceutical, and biomedical industries. In this work, PECs were prepared from two biopolymers, positively charged chitosan and negatively charged alginate. We investigate the changes in the structure and properties of PECs by adding sodium chloride (salt doping) to the system. The shear modulus of PECs can be tuned from ∼10 to 104 Pa by changing the salt concentration. The addition of salt led to a decrease in the water content of the complex phase with increasing shear modulus. However, at a very high salt concentration, the shear modulus of the complex phase decreased but did not lead to the liquid coacervate formation, typical of synthetic polyelectrolytes. This difference in phase behavior has likely been attributed to the hydrophobicity of chitosan and long semiflexible alginate and chitosan chains that restrict the conformational changes. Large amplitude oscillatory shear experiments captured nonlinear responses of PECs. The compositions of the PECs, determined as a function of salt concentration, signify the preferential partitioning of salt into the complex phase. Small-angle X-ray scattering of the salt-doped PECs indicates that the Kuhn length and radius of the alginate-chitosan associated structure qualitatively agree with the captured phase behavior and rheological data. This study provides insights into the structure-property as a function of salt concentration of natural polymer-based PECs necessary for developing functional materials from natural polyelectrolytes.

Inducible Nitric Oxide Synthase Embedded in Alginate/Polyethyleneimine Hydrogel as a New Platform to Explore NO-Driven Modulation of Biological Function.

Nitric oxide (NO), a small free radical molecule, turned out to be pervasive in biology and was shown to have a substantial influence on a range of biological activities, including cell growth and apoptosis. This molecule is involved in signaling and affects a number of physiologic functions. In recent decades, several processes related to cancer, such as angiogenesis, programmed cell death, infiltration, cell cycle progression, and metastasis, have been linked with nitric oxide. In addition, other parallel work showed that NO also has the potential to operate as an anti-cancer agent. As a result, it has gained attention in cancer-related therapeutics. The nitric oxide synthase enzyme family (NOS) is required for the biosynthesis of nitric oxide. It is becoming increasingly popular to develop NO-releasing materials as strong tumoricidal therapies that can deliver sustained high concentrations of nitric oxide to tumor sites. In this paper, we developed NO-releasing materials based on sodium alginate hydrogel. In this regard, alginate hydrogel discs were modified by adsorbing layers of polyethyleneimine and iNOS-oxygenase. These NO-releasing hydrogel discs were prepared using the layer-by-layer film building technique. The iNOS-oxygenase is adsorbed on the positively charged polyethyleneimine (PEI) matrix layer, which was formed on a negatively charged sodium alginate hydrogel. We show that nitric oxide is produced by enzymes contained within the hydrogel material when it is exposed to a solution containing all the components necessary for the NOS reaction. The electrostatic chemical adsorption of the layer-by-layer process was confirmed by FTIR measurements as well as scanning electron microscopy. We then tested the biocompatibility of the resulting modified sodium alginate hydrogel discs. We showed that this NOS-PEI-modified hydrogel is overall compatible with cell growth. We characterized the NOS/hydrogel films and examined their functional features in terms of NO release profiles. However, during the first 24 h of activity, these films show an increase in NO release flux, followed by a gradual drop and then a period of stable NO release. These findings show the inherent potential of using this system as a platform for NO-driven modulation of biological functions, including carcinogenesis.

The Dispersion and Coagulation of Negatively Charged Ca2Nb3O10 Perovskite Nanosheets in Sodium Alginate Dispersion.

Chemically exfoliated nanosheets have been extensively employed as functional nanofillers for the fabrication of polymer nanocomposites due to their remarkable electrical, magnetic and optical properties. However, achieving a good dispersion of charged nanosheets in polymer matrix, which will determine the performance of polymer nanocomposites, remains a challenge. Herein, we investigated the dispersion and aggregation behavior of negatively charged Ca2Nb3O10 (CNO) perovskite nanosheets in negatively charged sodium alginate (SA) aqueous dispersion using dynamic light scattering (DLS). When CNO nanosheets meet with SA, aggregation and coagulation inevitably occurred owing to the absorption of SA on nanosheets. By controlling the electrostatic attraction between positively charged poly(ethylene imine) (PEI) and negatively charged SA, the charge density and hydrodynamic size of SA can be tuned to enable the good dispersion of CNO nanosheets in SA. This result may provide a new strategy to achieve the good dispersion of charged nanosheets in charged polymers for the rational design of multifunctional nanocomposites.

Influence of electrode surface charge on current production by Geobacter sulfurreducens microbial anodes

Positively charged electrode surfaces are thought to enhance electrostatic interaction with mostly negatively charged bacteria cell surface, thereby improving microbial fuel cell performance. In this work, electrostatic self-assembly of charged polymers was used to systematically modify the surface of indium tin coated electrodes. Evaluation was based on start-up time, maximum current, biofilm thickness and coulombic efficiency of microbial Geobacter sulfurreducens anodes. Coated electrodes were polarized to +0.1 V vs. SHE as biological duplicates. The thickest biofilms and in turn highest current density and shortest start-up time was achieved for negatively charged electrode surfaces like non-coated ITO or polystyrol sulfonate coated electrodes, while positively charged chitosan, negatively charged alginate and positively charged polyethylene imine, in the particular order, produced thinner biofilms, with less current and longer start-up time. This finding contradicted the initial hypothesis. Most experiments on electrode surface modifications are accompanied by an increase in available electrode surface which makes it difficult to extract solely the effect caused by the surface modification. Our study showed the importance of considering also factors other than the surface charge, e.g. potential interactions of the surface modification with the conditioning film and the medium, namely the attraction of cations by a negatively charged surface.

An injectable, self-healing, 3D printable, double network co-enzymatically crosslinked hydrogel using marine poly- and oligo-saccharides for wound healing application

In this study, we designed dual network hydrogels with antioxidant and antibacterial activities using marine poly- and oligosaccharides with skin wound healing potential. The synergy between dual enzymatic co-crosslinking based on glucose oxidize (GOx)/horseradish peroxidase (HRP) and electrostatic interaction between positively charged chitooligosaccharides (COS) and phenolated chitosan with negatively charged phenolated alginate formed a hydrogel. The Gel-COS hydrogels exhibited toughness, self-healing, moldability, injectability, and 3D printability. Investigation of the physicochemical properties of the hydrogels exhibited a swelling ratio (< 50%) and in vitro biodegradation after 9 days. Furthermore, the hydrogels exhibited antioxidant properties and antibacterial activity against E. coli and S. aureus. The hydrogels were not cytotoxic and enhanced the migration of 3D cell encapsulated 3T3-L1 fibroblasts, blood vessel formation, as well as in vivo wound healing in a rat model. The Gel-COS hydrogel can be considered a promising skin wound dressing material.

Spatially and Temporally Controllable BMP-2 and TGF-β3 Double Release From Polycaprolactone Fiber Scaffolds via Chitosan-Based Polyelectrolyte Coatings.

Temporally and spatially controlled growth factor release from a polycaprolactone fiber mat, which also provides a matrix for directional cell colonization and infiltration, could be a promising regenerative approach for degenerated tendon-bone junctions. For this purpose, polycaprolactone fiber mats were coated with tailored chitosan-based nanogels to bind and release the growth factors bone morphogenetic protein 2 (BMP-2) and transforming growth factor-β3 (TGF-β3), respectively. In this work we provide meaningful in vitro data for the understanding of the drug delivery performance and sterilizability of novel implant prototypes in order to lay the foundation for in vivo testing. ELISA-based in vitro release studies were used to investigate the spatial and temporal control of release, as well as the influence of radiation sterilization on protein activity and release behavior. Layer-by-layer coatings based on BMP-2-containing chitosan tripolyphosphate nanogel particles and negatively charged alginate showed a good sustainment of BMP-2 release from chemically modified polycaprolactone fiber mats. Release control improved with increasing layer numbers. The approach of controlling the release via a barrier of cross-linked chitosan azide proved less promising. By using a simple, partial immersion-based dip-coating process, it was possible to apply opposing gradients of the growth factors BMP-2 and TGF-β3. Final radiation sterilization of the growth factor-loaded implant prototypes resulted in a radiation dose-correlated degradation of the growth factors, which could be prevented by lyophilization into protective matrices. For the manufacture of sterile implants, the growth factor loading step must probably be carried out under aseptic conditions. The layer-by-layer coated implant prototypes provided sustained release from opposing gradients of the growth factors BMP-2 and TGF-β3 and thus represent a promising approach for the restoration of tendon-bone defects.

Macroscopic membranes self‐assembled by alginate and a cationic and amphiphilic peptide for cell culture

AbstractPeptides self‐assembly systems have been explored over the past years in the context of various biological applications, such as tissue engineering and drug delivery. Here we present the development of hierarchically ordered planar and spherical macroscopic membranes constructed by an amphiphilic and cationic β‐sheet peptide that spontaneously assembles with the negatively charged alginate biopolymer. These two components generate a condensed film that developed to exhibit perpendicularly oriented fibers under specific conditioning over days. Here we examined the suitability of these spherical and planar membranes to serve as substrates for cell culture applications. Planar and spherical membranes were stable in the cell culture Dulbecco's modified eagle medium, at 37°C, over days. Breast‐cancer cells seeded on the peptide and alginate sides of fully developed and non‐fully developed planar membrane were viable for more than 2 weeks. In addition, cells were injected into spherical membranes and detected viable close to the rim even at 3 weeks. These results demonstrate the suitability of planar and spherical membranes to serve as a platform, for example, in studying cancer cells in unique niches and alternatively in potential allogeneic cell therapies.