Evaluation of methods for pore generation and their influence on physio-chemical properties of a protein based hydrogel

Tailoring of Physical Properties in Macroporous Poly(isocyanopeptide) Cryogels

Over the years, synthetic hydrogels have proven remarkably useful as cell culture matrixes to elucidate the role of the extracellular matrix (ECM) on cell behavior. Yet, their lack of interconnected macropores undermines the widespread use of hydrogels in biomedical applications. To overcome this limitation, cryogels, a class of macroporous hydrogels, are rapidly emerging. Here, we introduce a new, highly elastic, and tunable synthetic cryogel, based on poly(isocyanopeptides) (PIC). Introduction of methacrylate groups on PIC facilitated cryopolymerization through free-radical polymerization and afforded cryogels with an interconnected macroporous structure. We investigated which cryogelation parameters can be used to tune the architectural and mechanical properties of the PIC cryogels by systematically altering cryopolymerization temperature, polymer concentration, and polymer molecular weight. We show that for decreasing cryopolymerization temperatures, there is a correlation between cryogel pore size and stiffness. More importantly, we demonstrate that by simply varying the polymer concentration, we can selectively tune the compressive strength of PIC cryogels without affecting their architecture. This unique feature is highly useful for biomedical applications, as it facilitates decoupling of stiffness from other variables such as pore size. As such, PIC cryogels provide an interesting new biomaterial for scientists to unravel the role of the ECM in cellular functions.

The Role of Bioceramics for Bone Regeneration: History, Mechanisms, and Future Perspectives

Osteoporosis is a skeletal disorder marked by compromised bone integrity, predisposing individuals, particularly older adults and postmenopausal women, to fractures. The advent of bioceramics for bone regeneration has opened up auspicious pathways for addressing osteoporosis. Research indicates that bioceramics can help bones grow back by activating bone morphogenetic protein (BMP), mitogen-activated protein kinase (MAPK), and wingless/integrated (Wnt)/β-catenin pathways in the body when combined with stem cells, drugs, and other supports. Still, bioceramics have some problems, such as not being flexible enough and prone to breaking, as well as difficulties in growing stem cells and discovering suitable supports for different bone types. While there have been improvements in making bioceramics better for healing bones, it is important to keep looking for new ideas from different areas of medicine to make them even better. By conducting a thorough scrutiny of the pivotal role bioceramics play in facilitating bone regeneration, this review aspires to propel forward the rapidly burgeoning domain of scientific exploration. In the end, this appreciation will contribute to the development of novel bioceramics that enhance bone regrowth and offer patients with bone disorders alternative treatments.

Skeletal muscle regeneration with 3D bioprinted hyaluronate/gelatin hydrogels incorporating MXene nanoparticles

There has been significant progress in the field of three-dimensional (3D) bioprinting technology, leading to active research on creating bioinks capable of producing structurally and functionally tissue-mimetic constructs. Ti3C2Tx MXene nanoparticles (NPs), promising two-dimensional nanomaterials, are being investigated for their potential in muscle regeneration due to their unique physicochemical properties. In this study, we integrated MXene NPs into composite hydrogels made of gelatin methacryloyl (GelMA) and hyaluronic acid methacryloyl (HAMA) to develop bioinks (namely, GHM bioink) that promote myogenesis. The prepared GHM bioinks were found to offer excellent printability with structural integrity, cytocompatibility, and microporosity. Additionally, MXene NPs within the 3D bioprinted constructs encouraged the differentiation of C2C12 cells into skeletal muscle cells without additional support of myogenic agents. Genetic analysis indicated that representative myogenic markers both for early and late myogenesis were significantly up-regulated. Moreover, animal studies demonstrated that GHM bioinks contributed to enhanced regeneration of skeletal muscle while reducing immune responses in mice models with volumetric muscle loss (VML). Our results suggest that the GHM hydrogel can be exploited to craft a range of strategies for the development of a novel bioink to facilitate skeletal muscle regeneration because these MXene-incorporated composite materials have the potential to promote myogenesis.

Multimodal characterization of the collagen hydrogel structure and properties in response to physiologically relevant pH fluctuations

pH fluctuations within the extracellular matrix (ECM) and its principal constituent collagen, particularly in solid tumors and chronic wounds, may influence its structure and function. Whereas previous research examined the impact of pH on collagen fibrillogenesis, this study focuses on determining how pH fluctuations affect collagen hydrogels that mimic the physiological ECM. Utilizing a type I collagen hydrogel, we examined the influence of pH fluctuations on its structure, properties, and function while keeping the collagen hydrated. We show that collagen's secondary structure remains unaltered during pathologically relevant microenvironmental pH changes. By employing cryo scanning electron microscopy and artificial intelligence-assisted image analysis, we show that at physiological pH, collagen hydrogel presents densely packed, aligned, and elongated fibrils, which upon a decrease to pH 6.5, are transformed into shorter, sparser, and disoriented fibrils. The collagen possesses a higher storage modulus yet a lower permeability at pH 7 and 7.8 compared with pH 6.5 and 7.4. Exposing acidified collagen to a basic buffer reinstates its native structure and viscoelastic properties. Our study offers an innovative approach to analyze and characterize perturbations in hydrated collagen-based systems with potential implications for better understanding and combating disease progression. STATEMENT OF SIGNIFICANCE: As the main component of the extracellular matrix, collagen undergoes conformational changes associated with pH changes during disease. We analyze the impact of pH on pre-formed collagen fibers mimicking healthy tissues subjected to disease, and do not focus on the more studied fibrillogenesis process. Using cryogenic SEM, which allowed imaging close to the native state, we show that even minor fluctuations in the pH affect the collagen thickness, length, fiber alignment, and rheological properties. Following exposure to acidic pH, the collagen had short fibers, lacked orientation, and had low mechanical strength. This acidic collagen restored its original properties after returning to a neutral pH. These findings can help determine how pH changes can be modulated to restore healthy collagen properties.

The Effect of Rosmarinic Acid on Neural Differentiation of Wartons Jelly-derived Mesenchymal Stem Cells in Two-dimensional and Three-dimensional Cultures using Chitosan-based Hydrogel

Introduction

Numerous studies have shown the positive effects of rosmarinic acid on the nervous system. Rosmarinic acid as a herbal compound with anti-inflammatory effects can prevent thedestructive effect of inflammation on the nervous system. Furthermore, various studies haveemphasized the advantages of three-dimensional (3D) culture over the two-dimensional (2D) culture of cells.

Methods

In this study, thermosensitive chitosan (CH)-based hydrogel as a 3D scaffoldwith the combination of chitosan, beta-glycerol phosphate and hydroxyl ethyl cellulose (CH-GP-HEC) loaded with rosmarinic acid was used to induce neuronal differentiation in humanWharton jelly stem cells. Also, cells were divided into eight groups to evaluate the effect of 3Dcell culture and to compare gene expression in different induction conditions.

Results

The results ofgene expression analysis showed the highest expression of neuronal markers in Whartons jelly derived mesenchymal stem cells (WJMSCs) cultured in chitosan, beta-glycerol phosphate and hydroxyl ethyl cellulose (ch-gp-hec) loaded with differentiation medium androsmarinic acid. According to the results of gene expression, rosmarinic acid alone has a positiveeffect on the induction of expression of neural markers. This positive effect is enhanced by cellculture in 3D conditions.

Conclusion

This study shows that rosmarinic acid can be considered an inexpensiveand available compound for use in neural tissue engineering. The results of this study indicatethat rosmarinic acid can be considered a cheap and available compound for use in neural tissueengineering.

Synthesis of nanocapsules blended polymeric hydrogel loaded with bupivacaine drug delivery system for local anesthetics and pain management

Local anesthetics are used clinically for the control of postoperative pain management. This study aimed to develop chitosan (CS) with genipin (GP) hydrogels as the hydrophilic lipid shell loaded poly(ε-caprolactone) (PC) nanocapsules as the hydrophobic polymeric core composites (CS-GP/PC) to deliver bupivacaine (BPV) for the prolongation of anesthesia and pain relief. The swelling ratio, in vitro degradation, and rheological properties enhancement of CS-GP/PC polymeric hydrogel. The incorporation of PC nanocapsules into CS-GP hydrogels was confirmed by SEM, FTIR, and XRD analysis. Scanning electron microscopy results demonstrated that the CS-GP hydrogels and CS-GP/PC polymeric hydrogels have a porous structure, the pore dimensions being non-uniform with diameters between 25 and 300 μm. The in vitro drug release profile of CS-GP/PC polymeric hydrogel has been achieved 99.2 ± 1.12% of BPV drug release in 36 h. Cellular viability was evaluated using the CCK-8 test on 3T3 fibroblast cells revealed that the obtained CS-GP/PC polymeric hydrogel with BPV exhibited no obvious cytotoxicity. The CS-GP/PC polymeric hydrogel loaded with BPV showed significant improvement in pain response compared to the control group animals for at least 7 days. When compared with BPV solution, CS-GP hydrogel and CS-GP/PC polymeric hydrogel improved the skin permeation of BPV 3-fold and 5-fold in 24 h, respectively. In vitro and in vivo results pointed out PC nanocapsules loaded CS-GP hydrogel can act as effective drug carriers, thus prolonging and enhancing the anesthetic effect of BPV. Histopathological results demonstrated the excellent biodegradability and biocompatibility of the BPV-loaded CS-GP/PC polymeric hydrogel system on 7, 14, and 21 days without neurotoxicity.HIGHLIGHTSPreparation and characterization of CS-GP/PC polymeric hydrogel system.BPV-loaded CS-GP/PC exhibited prolonged in vitro release in PBS solution.Cytotoxicity of BPV-loaded CS-GP/PC polymeric hydrogel against fibroblast (3T3) cells.Development of CS-GP/PC a promising skin drug-delivery system for local anesthetic BPV.

Alginate-Lysozyme Nanofibers Hydrogels with Improved Rheological Behavior, Printability and Biological Properties for 3D Bioprinting Applications

In this study, alginate nanocomposite hydrogel bioinks reinforced with lysozyme nanofibers (LNFs) were developed. Alginate-LNF (A-LNF) suspensions with different LNF contents (1, 5 and 10 wt.%) were prepared and pre-crosslinked with 0.5% (w/v) CaCl₂ to formulate A-LNF inks. These inks exhibit proper shear-thinning behavior and good recovery properties (~90%), with the pre-crosslinking step playing a crucial role. A-LNF fully crosslinked hydrogels (with 2% (w/v) CaCl₂) that mimic 3D printing scaffolds were prepared, and it was observed that the addition of LNFs improved several properties of the hydrogels, such as the morphology, swelling and degradation profiles, and mechanical properties. All formulations are also noncytotoxic towards HaCaT cells. The printing parameters and 3D scaffold model were then optimized, with A-LNF inks showing improved printability. Selected A-LNF inks (A-LNF0 and A-LNF5) were loaded with HaCaT cells (cell density 2 × 10⁶ cells mL⁻¹), and the cell viability within the bioprinted scaffolds was evaluated for 1, 3 and 7 days, with scaffolds printed with the A-LNF5 bioink showing the highest values for 7 days (87.99 ± 1.28%). Hence, A-LNF bioinks exhibited improved rheological performance, printability and biological properties representing a good strategy to overcome the main limitations of alginate-based bioinks.

Functionalized Hydrogels for Cartilage Repair: The Value of Secretome-Instructive Signaling

Cartilage repair has been a challenge in the medical field for many years. Although treatments that alleviate pain and injury are available, none can effectively regenerate the cartilage. Currently, regenerative medicine and tissue engineering are among the developed strategies to treat cartilage injury. The use of stem cells, associated or not with scaffolds, has shown potential in cartilage regeneration. However, it is currently known that the effect of stem cells occurs mainly through the secretion of paracrine factors that act on local cells. In this review, we will address the use of the secretome—a set of bioactive factors (soluble factors and extracellular vesicles) secreted by the cells—of mesenchymal stem cells as a treatment for cartilage regeneration. We will also discuss methodologies for priming the secretome to enhance the chondroregenerative potential. In addition, considering the difficulty of delivering therapies to the injured cartilage site, we will address works that use hydrogels functionalized with growth factors and secretome components. We aim to show that secretome-functionalized hydrogels can be an exciting approach to cell-free cartilage repair therapy.

Development of polycarbonate urethane-based materials with controlled diclofenac release for cartilage replacement

Hydrogels are very promising human cartilage replacement materials since they are able to mimic its structure and properties. Besides, they can be used as platforms for drug delivery to reduce inflammatory postsurgical reactions. Polycarbonate urethane (PCU) has been used in orthopedic applications due to its long-term biocompatibility and bio-durability. In this work, PCU-based hydrogels with the ability to release an anti-inflammatory (diclofenac) were developed, for the first time, for such purpose. The materials were reinforced with different amounts of cellulose acetate (CA, 10%, 15%, and 25% w/w) or carbon nanotubes (CNT, 1% and 2% w/w) in order to improve their mechanical properties. Samples were characterized in terms of compressive and tensile mechanical behavior. It was found that 15% CA and 2% CNT reinforcement led to the best mechanical properties. Thus, these materials were further characterized in terms of morphology, wettability, and friction coefficient (CoF). Contrarily to CNTs, the addition of CA significantly increased the material's porosity. Both materials became more hydrophilic, and the CoF slightly increased for PCU + 15%CA. The materials were loaded by soaking with diclofenac, and drug release experiments were conducted. PCU, PCU + 15%CA and PCU + 2%CNT presented similar release profiles, being able to ensure a controlled release of DFN for at least 4 days. Finally, in vitro cytotoxicity tests using human chondrocytes were also performed and confirmed a high biocompatibility for the three studied materials.

Kinetic Method of Producing Pores Inside Protein-Based Biomaterials without Compromising Their Structural Integrity

Hydrogels made from globular proteins cross-linked covalently into a stable network are becoming an important type of biomaterial, with applications in artificial tissue design and cell culture scaffolds, and represent a promising system to study the mechanical and biochemical unfolding of proteins in crowded environments. Due to the small size of the globular protein domains, typically 2-5 nm, the primary network allows for a limited transfer of protein molecules and prevents the passing of particles and aggregates with dimensions over 100 nm. Here, we demonstrate a method to produce protein materials with micrometer-sized pores and increased permeability. Our approach relies on forming two competing networks: a covalent network made from cross-linked bovine serum albumin (BSA) proteins via a light-activated reaction and a physical network triggered by the aggregation of a polysaccharide, alginate, in the presence of Ca²⁺ ions. By fine-tuning the reaction times, we produce porous-protein hydrogels that retain the mechanical characteristics of their less-porous counterparts. We further describe a simple model to investigate the kinetic balance between the nucleation of alginate and cross-linking of BSA molecules and find the upper rate of the alginate aggregation reaction driving pore formation. By enabling a more significant permeability for protein-based materials without compromising their mechanical response, our method opens new vistas into studying protein-protein interactions and cell growth and designing novel affinity methods.

Albumin Microspheres as "Trans-Ferry-Beads" for Easy Cell Passaging in Cell Culture Technology

Protein hydrogels represent ideal materials for advanced cell culture applications, including 3D-cultivation of even fastidious cells. Key properties of fully functional and, at the same time, economically successful cell culture materials are excellent biocompatibility and advanced fabrication processes allowing their easy production even on a large scale based on affordable compounds. Chemical crosslinking of bovine serum albumin (BSA) with N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC) in a water-in-oil emulsion with isoparaffinic oil as the continuous phase and sorbitan monooleate as surfactant generates micro-meter-scale spherical particles. They allow a significant simplification of an indispensable and laborious step in traditional cell culture workflows. This cell passaging (or splitting) to fresh culture vessels/flasks conventionally requires harsh trypsinization, which can be omitted by using the “trans-ferry-beads” presented here. When added to different pre-cultivated adherent cell lines, the beads are efficiently boarded by cells as passengers and can be easily transferred afterward for the embarkment of novel flasks. After this procedure, cells are perfectly viable and show normal growth behavior. Thus, the trans-ferry-beads not only may become extremely affordable as a final product but also may generally replace trypsinization in conventional cell culture, thereby opening new routes for the establishment of optimized and resource-efficient workflows in biological and medical cell culture laboratories.

BSA Hydrogel Beads Functionalized with a Specific Aptamer Library for Capturing Pseudomonas aeruginosa in Serum and Blood

Systemic blood stream infections are a major threat to human health and are dramatically increasing worldwide. Pseudomonas aeruginosa is a WHO-alerted multi-resistant pathogen of extreme importance as a cause of sepsis. Septicemia patients have significantly increased survival chances if sepsis is diagnosed in the early stages. Affinity materials can not only represent attractive tools for specific diagnostics of pathogens in the blood but can prospectively also serve as the technical foundation of therapeutic filtration devices. Based on the recently developed aptamers directed against P. aeruginosa, we here present aptamer-functionalized beads for specific binding of this pathogen in blood samples. These aptamer capture beads (ACBs) are manufactured by crosslinking bovine serum albumin (BSA) in an emulsion and subsequent functionalization with the amino-modified aptamers on the bead surface using the thiol- and amino-reactive bispecific crosslinker PEG₄-SPDP. Specific and quantitative binding of P. aeruginosa as the dedicated target of the ACBs was demonstrated in serum and blood. These initial but promising results may open new routes for the development of ACBs as a platform technology for fast and reliable diagnosis of bloodstream infections and, in the long term, blood filtration techniques in the fight against sepsis.

Glycosaminoglycan-Based Cryogels as Scaffolds for Cell Cultivation and Tissue Regeneration

Cryogels are a class of macroporous, interconnective hydrogels polymerized at sub-zero temperatures forming mechanically robust, elastic networks. In this review, latest advances of cryogels containing mainly glycosaminoglycans (GAGs) or composites of GAGs and other natural or synthetic polymers are presented. Cryogels produced in this way correspond to the native extracellular matrix (ECM) in terms of both composition and molecular structure. Due to their specific structural feature and in addition to an excellent biocompatibility, GAG-based cryogels have several advantages over traditional GAG-hydrogels. This includes macroporous, interconnective pore structure, robust, elastic, and shape-memory-like mechanical behavior, as well as injectability for many GAG-based cryogels. After addressing the cryogelation process, the fabrication of GAG-based cryogels and known principles of GAG monomer crosslinking are discussed. Finally, an overview of specific GAG-based cryogels in biomedicine, mainly as polymeric scaffold material in tissue regeneration and tissue engineering-related controlled release of bioactive molecules and cells, is provided.

Tunable Sponge-Like Hierarchically Porous Hydrogels with Simultaneously Enhanced Diffusivity and Mechanical Properties

Crosslinked polymers and gels are important in soft robotics, solar vapor generation, energy storage, drug delivery, catalysis, and biosensing. However, their attractive mass transport and volume-changing abilities are diffusion-limited, requiring miniaturization to avoid slow response. Typical approaches to improving diffusion in hydrogels sacrifice mechanical properties by increasing porosity or limit the total volumetric flux by directionally confining the pores. Despite tremendous efforts, simultaneous enhancement of diffusion and mechanical properties remains a long-standing challenge hindering broader practical applications of hydrogels. In this work, cononsolvency photopolymerization is developed as a universal approach to overcome this swelling-mechanical property trade-off. The as-synthesized poly(N-isopropylacrylamide) hydrogel, as an exemplary system, presents a unique open porous network with continuous microchannels, leading to record-high volumetric (de)swelling speeds, almost an order of magnitude higher than reported previously. This swelling enhancement comes with a simultaneous improvement in Young's modulus and toughness over conventional hydrogels fabricated in pure solvents. The resulting fast mass transport enables in-air operation of the hydrogel via rapid water replenishment and ultrafast actuation. The method is compatible with 3D printing. The generalizability is demonstrated by extending the technique to poly(N-tertbutylacrylamide-co-polyacrylamide) and polyacrylamide hydrogels, non-temperature-responsive polymer systems, validating the present hypothesis that cononsolvency is a generic phenomenon driven by competitive adsorption.

Heterogeneous Hydrogel Structures with Spatiotemporal Reconfigurability using Addressable and Tunable Voxels

Stimuli-responsive hydrogels can sense environmental cues and change their volume accordingly without the need for additional sensors or actuators. This enables a significant reduction in the size and complexity of resulting devices. However, since the responsive volume change of hydrogels is typically uniform, their robotic applications requiring localized and time-varying deformations have been challenging to realize. Here, using addressable and tunable hydrogel building blocks-referred to as soft voxel actuators (SVAs)-heterogeneous hydrogel structures with programmable spatiotemporal deformations are presented. SVAs are produced using a mixed-solvent photopolymerization method, utilizing a fast reaction speed and the cononsolvency property of poly(N-isopropylacrylamide) (PNIPAAm) to produce highly interconnected hydrogel pore structures, resulting in tunable swelling ratio, swelling rate, and Young's modulus in a simple, one-step casting process that is compatible with mass production of SVA units. By designing the location and swelling properties of each voxel and by activating embedded Joule heaters in the voxels, spatiotemporal deformations are achieved, which enables heterogeneous hydrogel structures to manipulate objects, avoid obstacles, generate traveling waves, and morph to different shapes. Together, these innovations pave the way toward tunable, untethered, and high-degree-of-freedom hydrogel robots that can adapt and respond to changing conditions in unstructured environments.

Fabrication and Evaluation of Silk Sericin-Derived Hydrogel for the Release of the Model Drug Berberine

Silk sericin (SS) produced by Bombyx mori is normally discarded as waste in manufacturing processes, which causes environmental pollution. Therefore, investigating the use of silk sericin has economic and environmental benefits. As a three-dimensional structure, the sericin-derived hydrogel was explored in different applications. However, many developed gelation procedures raise concerns regarding safety, cost, and duration of gelation time. In this work, "thiol-ene" click chemistry was used to quickly and controllably prepare an SS-derived hydrogel to resolve these early concerns. Then, berberine was loaded and used as a model for investigating the drug-release profiles of the prepared hydrogel. The experimental results revealed that this hydrogel is eligible for a long-term release of berberine. Throughout the antibacterial experiments, the released berberine maintained its antibacterial activity. Our work expands the application of SS in biomedical industries in an eco-friendly way. Furthermore, the discussed strategy could provide a reference for the subsequent development of SS-derived materials.

Image analysis method for heterogeneity and porosity characterization of biomimetic hydrogels

This work presents an image processing procedure for characterization of porosity and heterogeneity of hydrogels network mainly based on the analysis of cryogenic scanning electron microscopy (cryo-SEM) images and can be extended to any other type of microscopy images of hydrogel porous network. An algorithm consisting of different filtering, morphological transformation, and thresholding steps to denoise the image whilst emphasizing the edges of the hydrogel walls for extracting either the pores or hydrogel walls features is explained. Finally, the information of hydrogel porosity and heterogeneity is presented in form of pore size distribution, spatial contours maps and kernel density dot plots. The obtained results reveal that a non-parametric kernel density plot effectively determines the spatial heterogeneity and porosity of the hydrogel.

Smart bio-gel optofluidic Mach-Zehnder interferometers multiphoton-lithographically customized with chemo-mechanical-opto transduction and bio-triggered degradation

Stimulus-responsive optical polymers, especially gels, are enabling new-concept energy-transducing "smart" optics. Full exploitation of their molecule-derived tuning and integration with traditional micro/nano-optics/optoelectronics rely on the implementation of devices by advanced "intelligent" micro/nano-manufacturing technologies, especially photolithographies with wide compatibility. In light of the increasing need for an organic combination of smart optical materials and digital micro/nano-manufacturing, novel "smart" optical micro-switches, namely, stimulus-actuated Mach-Zehnder interferometers as a proof-of-concept demonstration, were prototyped with protein-based hydrogels via aqueous multiphoton femtosecond laser direct writing (FsLDW). Protein-based Mach-Zehnder-interferometric smart optical devices here display a morphological quality sufficient for optical applications (average surface roughness ≤∼20 nm), nano-precision three-dimensional (3D) geometry of these millimeter-scale devices and purposely structured distribution of photo-crosslinking degree. Moreover, the device configuration was customized with unbalanced branches in which meticulous stimulus-responsive ability can be realized by simply tuning the surrounding chemical stimuli (i.e., Na₂SO₄ concentration here). The "heterogeneous" configuration with unbalanced branches (i.e., different optical and stimulus-responsive features) exhibits as-designed "smart" switching of propagated near-infrared light (∼808 nm). These capabilities, along with total biodegradation, indicate the application promise of this gel-based optic construction strategy towards novel "intelligent", bio/eco-friendly, self-tuning or sensing photonic integrated systems like optofluidics.

A Cerberus-Inspired Anti-Infective Multicomponent Gatekeeper Hydrogel against Infections with the Emerging "Superbug" Yeast Candida auris

The pathogenic yeast Candida auris has received increasing attention due to its ability to cause fatal infections, its resistance toward important fungicides, and its ability to persist on surfaces including medical devices in hospitals. To brace health care systems for this considerable risk, alternative therapeutic approaches such as antifungal peptides are urgently needed. In clinical wound care, a significant focus has been directed toward novel surgical (wound) dressings as first defense lines against C. auris. Inspired by Cerberus the Greek mythological "hound of Hades" that prevents the living from entering and the dead from leaving hell, the preparation of a gatekeeper hybrid hydrogel is reported featuring lectin-mediated high-affinity immobilization of C. auris cells from a collagen gel as a model substratum in combination with a release of an antifungal peptide drug to kill the trapped cells. The vision is an efficient and safe two-layer medical composite hydrogel for the treatment of severe wound infections that typically occur in hospitals. Providing this new armament to the repertoire of possibilities for wound care in critical (intensive care) units may open new routes to shield and defend patients from infections and clinical facilities from spreading and invasion of C. auris and probably other fungal pathogens.

Characterisation of hydrogels: Linking the nano to the microscale

Hydrogels are water enriched soft materials widely used for applications as varied as super absorbents, breast implants and contact lenses. Hydrogels have also been designed for smart functional devices including drug delivery, tissue engineering and diagnostics such as blood typing. The hydrogel properties and functionality depend on their crosslinking density, water holding capacity and fibre/polymer composition, strength and internal structure. Determining these parameters and properties are challenging. This review presents the main characterisation methods providing both qualitative and quantitative information of the structures and compositions of hydrogel. The length scale of interest ranges from the nano to the micro scale and the techniques and results are analysed in relationship to the hydrogel macroscopic applications. The characterisation methods examined aim at quantifying swelling, mechanical strength, mesh size, bound and free water content, pore structure, chemical composition, strength of chemical bonds and mechanical strength. These hydrogel parameters enable us to understand the fundamental mechanisms of hydrogel formation, to control their structure and functionality, and to optimize and tailor specific hydrogel properties to engineer particular applications.

Numerical Investigations of Hepatic Spheroids Metabolic Reactions in a Perfusion Bioreactor

Miniaturized culture systems of hepatic cells are emerging as a strong tool facilitating studies related to liver diseases and drug discovery. However, the experimental optimization of various parameters involved in the operation of these systems is time-consuming and expensive. Hence, developing numerical tools predicting the function of such systems can significantly reduce the associated cost. In this paper, a perfusion-based three dimensional (3D) bioreactor comprising encapsulated human liver hepatocellular carcinoma (HepG2) spheroids are analyzed. The flow and mass transfer equations for oxygen as well as different metabolites such as albumin, glucose, glutamine, ammonia, and urea were solved in three different domains, i.e., free flow, hydrogel, and spheroid porous media sections. Since the spheroids were encapsulated inside the hydrogel, shear stress imposed on them were found to be less than tolerable thresholds. The predicted cumulative albumin concentration over the 7 days of culture period showed a good agreement with the experimental data. Based on the critical role of oxygen supply to the hepatocytes, a parametric study was performed and the effect of various parameters was investigated. Results illustrated that convection mechanism was the dominant transport mechanism in the main-stream section contrary to the intra spheroids parts where the diffusion was the prevailing transport mechanism. In the hydrogel parts, the rate of diffusion and convection mechanisms were almost identical. As expected, higher perfusion rate would provide high oxygen level for the cells and, smaller spheroids with a diameter of 100 μm were at the low risk of hypoxic conditions due to short diffusive oxygen penetration depth. Numerical results evidenced that spheroids with diameter size >200 μm at low porosities (ε = 0.2-0.3) were at risk of oxygen depletion, especially at locations near the core center. Therefore, these results could be beneficial in preventing hypoxic conditions during in vitro experiments. The presented numerical model provides a numerical platform which can help researchers to design and optimize complex bioreactors and obtain numerical indexes of the main metabolites in a very short time prior to any fabrications. Such numerical indexes can be helpful in certifying the outcomes of forensic investigations.

A dual synergistic of curcumin and gelatin on thermal-responsive hydrogel based on Chitosan-P123 in wound healing application

This study aimed to fabricate the potential therapeutic scaffold to efficiently and safely fastening skin wound healing. A biocompatible grafting polymer-based thermal sensitive hybrid hydrogel (Chitosan-P123, CP) containing gelatin and curcumin was designed to be suitable stiffness for tissue regeneration. A detailed in the rheological study found that the encapsulated agents induced the change in the stiffness of the hydrogel from the hard to the soft. Especial, the thermally induced phase transition of CP hydrogel was governed by the participant of gelatin rather than curcumin. For example, at 25 wt% gelatin, CP hydrogel exhibited a unique gel-sol-gel transition following the function of temperature. Moreover, in vitro investigation revealed that the hybrid hydrogel provides the capacity of especially induced curcumin release with a sustainable rate as well as the excellent biocompatibility scaffold. Altogether with in vivo study, the hybrid hydrogel highlighted the advance of the dual synergistic of curcumin and gelatin in development of smart scaffold system, which promoted the efficacy in the regeneration of the structure and the barrier's function of damaged skin such as wound or skin cancer.

Gelatin-polysaccharide composite scaffolds for 3D cell culture and tissue engineering: Towards natural therapeutics

Gelatin is a promising material as scaffold with therapeutic and regenerative characteristics due to its chemical similarities to the extracellular matrix (ECM) in the native tissues, biocompatibility, biodegradability, low antigenicity, cost-effectiveness, abundance, and accessible functional groups that allow facile chemical modifications with other biomaterials or biomolecules. Despite the advantages of gelatin, poor mechanical properties, sensitivity to enzymatic degradation, high viscosity, and reduced solubility in concentrated aqueous media have limited its applications and encouraged the development of gelatin-based composite hydrogels. The drawbacks of gelatin may be surmounted by synergistically combining it with a wide range of polysaccharides. The addition of polysaccharides to gelatin is advantageous in mimicking the ECM, which largely contains proteoglycans or glycoproteins. Moreover, gelatin-polysaccharide biomaterials benefit from mechanical resilience, high stability, low thermal expansion, improved hydrophilicity, biocompatibility, antimicrobial and anti-inflammatory properties, and wound healing potential. Here, we discuss how combining gelatin and polysaccharides provides a promising approach for developing superior therapeutic biomaterials. We review gelatin-polysaccharides scaffolds and their applications in cell culture and tissue engineering, providing an outlook for the future of this family of biomaterials as advanced natural therapeutics.

Easy Manipulation of Architectures in Protein-based Hydrogels for Cell Culture Applications

Hydrogels are recognized as promising materials for cell culture applications due to their ability to provide highly hydrated cell environments. The field of 3D templates is rising due to the potential resemblance of those materials to the natural extracellular matrix. Protein-based hydrogels are particularly promising because they can easily be functionalized and can achieve defined structures with adjustable physicochemical properties. However, the production of macroporous 3D templates for cell culture applications using natural materials is often limited by their weaker mechanical properties compared to those of synthetic materials. Here, different methods were evaluated to produce macroporous bovine serum albumin (BSA)-based hydrogel systems, with adjustable pore sizes in the range of 10 to 70 µm in radius. Furthermore, a method to generate channels in this protein-based material that are several hundred microns long was established. The different methods to produce pores, as well as the influence of pore size on material properties such as swelling ratio, pH, temperature stability, and enzymatic degradation behavior, were analyzed. Pore sizes were investigated in the native, swollen state of the hydrogels using confocal laser scanning microscopy. The feasibility for cell culture applications was evaluated using a cell-adhesive RGD peptide modification of the protein system and two model cell lines: human breast cancer cells (A549) and adenocarcinomic human alveolar basal epithelial cells (MCF7).

Lectin-mediated reversible immobilization of human cells into a glycosylated macroporous protein hydrogel as a cell culture matrix

3D cell culture is a helpful approach to study cell-cell interaction in a native-like environment, but is often limited due the challenge of retrieving cells from the material. In this study, we present the use of recombinant lectin B, a sugar-binding protein with four binding cavities, to enable reversible cell integration into a macroporous protein hydrogel matrix. By functionalizing hydrogel precursors with saccharose, lectin B can both bind to sugar moieties on the cellular surface as well as to the modified hydrogel network. Confocal microscopy and flow cytometry analysis revealed cells to be integrated into the network and to adhere and proliferate. Furthermore, the specificity and reversibility was investigated by using a recombinantly produced yellow fluorescent - lectin B fusion protein and a variety of sugars with diverging affinities for lectin B at different concentrations and elution times. Cells could be eluted within minutes by addition of L-fucose to the cell-loaded hydrogels to make cells available for further analysis.

Beyond bread and beer: whole cell protein extracts from baker's yeast as a bulk source for 3D cell culture matrices

Here, we present a novel approach to form hydrogels from yeast whole cell protein. Countless hydrogels are available for sophisticated research, but their fabrication is often difficult to reproduce, with the gels being complicated to handle or simply too expensive. The yeast hydrogels presented here are polymerized using a four-armed, amine reactive crosslinker and show a high chemical and thermal resistance. The free water content was determined by measuring swelling ratios for different protein concentrations, and in a freeze-drying approach, pore sizes of up to 100 μm in the gel could be created without destabilizing the 3D network. Elasticity was proofed to be adjustable with the help of atomic force microscopy by merely changing the amount of used protein. Furthermore, the material was tested for possible cell culture applications; diffusion rates in the network are high enough for sufficient supply of human breast cancer cells and adenocarcinomic human alveolar basal epithelial cells with nutrition, and cells showed high viabilities when tested for compatibility with the material. Furthermore, hydrogels could be functionalized with RGD peptide and the optimal concentration for sufficient cell adhesion was determined to be 150 μM. Given that yeast protein is one of the cheapest and easiest available protein sources and that hydrogels are extremely easy to handle, the developed material has highly promising potential for both sophisticated cell culture techniques as well as for larger scale industrial applications.