Gellan gum methacrylate and laponite as an innovative nanocomposite hydrogel for biomedical applications

Laponite nanoclays for the sustained delivery of therapeutic proteins

Protein therapeutics hold immense promise for treating a wide array of diseases. However, their efficacy is often compromised by rapid degradation and clearance. The synthetic smectite clay Laponite emerges as a promising candidate for their sustained delivery. Despite its unique properties allow to load and release proteins mitigating burst release and extending their effects, precise control over Laponite-protein interactions remains challenging since it depends on a complex interplay of factors whose implication is not fully understood yet. The aim of this review article is to shed light on this issue, providing a comprehensive discussion of the factors influencing protein loading and release, including the physicochemical properties of the nanoclay and proteins, pH, dispersion buffer, clay/protein concentration and Laponite degradation. Furthermore, we thoroughly revise the array of bioactive proteins that have been delivered from formulations containing the nanoclay, highlighting Laponite-polymer nanocomposite hydrogels, a promising avenue currently under extensive investigation.

Gellan Gum as a Unique Microbial Polysaccharide: Its Characteristics, Synthesis, and Current Application Trends

Gellan gum (GG) is a linear, negatively charged exopolysaccharide that is biodegradable and non-toxic. When metallic ions are present, a hard and transparent gel is produced, which remains stable at a low pH. It exhibits high water solubility, can be easily bio-fabricated, demonstrates excellent film/hydrogel formation, is biodegradable, and shows biocompatibility. These characteristics render GG a suitable option for use in food, biomedical, and cosmetic fields. Thus, this review paper offers a concise summary of microbial polysaccharides. Moreover, an in-depth investigation of trends in different facets of GG, such as biosynthesis, chemical composition, and physical and chemical properties, is emphasized. In addition, this paper highlights the process of extracting and purifying GG. Furthermore, an in-depth discussion of the advantages and disadvantages of GG concerning other polysaccharides is presented. Moreover, the utilization of GG across different industries, such as food, medicine, pharmaceuticals, cosmetics, etc., is thoroughly examined and will greatly benefit individuals involved in this field who are seeking fresh opportunities for innovative projects in the future.

Injectable Nanoengineered Adhesive Hydrogel for Treating Enterocutaneous Fistulas

Enterocutaneous fistula (ECF) is a severe medical condition where an abnormal connection forms between the gastrointestinal tract and skin. ECFs are, in most cases, a result of surgical complications such as missed enterotomies or anastomotic leaks. The constant leakage of enteric and fecal contents from the fistula site leads to skin breakdown and increases the risk of infection. Despite advances in surgical techniques and postoperative management, ECF accounts for significant mortality rates, estimated between 15-20%, and causes debilitating morbidity. Therefore, there is a critical need for a simple and effective method to seal and heal ECF. Injectable hydrogels with combined properties of robust mechanical properties and cell infiltration/proliferation have the potential to block and heal ECF. Herein, we report the development of an injectable nanoengineered adhesive hydrogel (INAH) composed of a synthetic nanosilicate (Laponite®) and a gelatin-dopamine conjugate for treating ECF. The hydrogel undergoes fast cross-linking using a co-injection method, resulting in a matrix with improved mechanical and adhesive properties. INAH demonstrates appreciable blood clotting abilities and is cytocompatible with fibroblasts. The adhesive properties of the hydrogel are demonstrated in ex vivo adhesion models with skin and arteries, where the volume stability in the hydrated internal environment facilitates maintaining strong adhesion. In vivo assessments reveal that the INAH is biocompatible, supporting cell infiltration and extracellular matrix deposition while not forming fibrotic tissue. These findings suggest that this INAH holds promising translational potential for sealing and healing ECF.

The prescription design and key properties of nasal gel for CNS drug delivery: A review

Central nervous system (CNS) diseases are among the major health problems. However, blood-brain barrier (BBB) makes traditional oral and intravenous delivery of CNS drugs inefficient. The unique direct connection between the nose and the brain makes nasal administration a great potential advantage in CNS drugs delivery. However, nasal mucociliary clearance (NMCC) limits the development of drug delivery systems. Appropriate nasal gel viscosity alleviates NMCC to a certain extent, gels based on gellan gum, chitosan, carbomer, cellulose and poloxamer have been widely reported. However, nasal gel formulation design and key properties for alleviating NMCC have not been clearly discussed. This article summarizes gel formulations of different polymers in existing nasal gel systems, and attempts to provide a basis for researchers to conduct in-depth research on the key characteristics of gel matrix against NMCC.

Photo-cross-linked Hydrogels for Cartilage and Osteochondral Repair

Photo-cross-linked hydrogels, which respond to light and induce structural or morphological transitions, form a microenvironment that mimics the extracellular matrix of native tissue. In the last decades, photo-cross-linked hydrogels have been widely used in cartilage and osteochondral tissue engineering due to their good biocompatibility, ease of fabrication, rapid in situ gel-forming ability, and tunable mechanical and degradable properties. In this review, we systemically summarize the different types and physicochemical properties of photo-cross-linked hydrogels (including the materials and photoinitiators) and explore the biological properties modulated through the incorporation of additives, including cells, biomolecules, genes, and nanomaterials, into photo-cross-linked hydrogels. Subsequently, we compile the applications of photo-cross-linked hydrogels with a specific focus on cartilage and osteochondral repair. Finally, current limitations and future perspectives of photo-cross-linked hydrogels are also discussed.

Advancements and Applications of Injectable Hydrogel Composites in Biomedical Research and Therapy

Injectable hydrogels have gained popularity for their controlled release, targeted delivery, and enhanced mechanical properties. They hold promise in cardiac regeneration, joint diseases, postoperative analgesia, and ocular disorder treatment. Hydrogels enriched with nano-hydroxyapatite show potential in bone regeneration, addressing challenges of bone defects, osteoporosis, and tumor-associated regeneration. In wound management and cancer therapy, they enable controlled release, accelerated wound closure, and targeted drug delivery. Injectable hydrogels also find applications in ischemic brain injury, tissue regeneration, cardiovascular diseases, and personalized cancer immunotherapy. This manuscript highlights the versatility and potential of injectable hydrogel nanocomposites in biomedical research. Moreover, it includes a perspective section that explores future prospects, emphasizes interdisciplinary collaboration, and underscores the promising future potential of injectable hydrogel nanocomposites in biomedical research and applications.

Nanoclays for wound management applications

Nanotechnology has been comprehensively applied as a new approach to managing wound healing. Particularly, nanoclays are being used to improve traditional wound healing approaches or new therapies. Nanoclays are nanoscale aluminosilicates with remarkable intrinsic properties, including the capacity to promote hemostatic response, anti-inflammatory effects, angiogenesis, and re-epithelization. The main purpose of the present review is focusing on skin lesions, post-surgical wounds, burn wounds, and chronic ulcer skin wounds that can be treated using nanoclays, not only as vehicles for therapeutic molecules' efficacy improvement but also alone due to their native beneficial features. A systematic search of the PubMed, ScienceDirect, Scopus, Web of Science, and Google Scholar databases revealed several studies satisfying the purpose of our study. In addition, the selected keywords were used to refine the information. Non-planar hydrous phyllosilicates have been compared with other nanoclays considering their acute specific surface area and loading capacity are strongly influenced by their structure. Nanocomposites in the powder form may be directly incorporated in polymers to form gels, biofilms, and scaffolds that may be adjustable to wound sites. Also, nanoclays can be directly incorporated into polymer mats. Regarding hydrogels/films and mats, nanoclays can improve their mechanical strength, thermal stability, viscosity, and cohesive strength. Additionally, nanoclays are able to control drug release, as well as their skin bioavailability, and seem to be promising candidates to overcome cytotoxicity problems; further in vivo toxicity studies are required.

Green Chemistry Principles for Nano- and Micro-Sized Hydrogel Synthesis

The growing demand for drug carriers and green-technology-based tissue engineering materials has enabled the fabrication of different types of micro- and nano-assemblies. Hydrogels are a type of material that have been extensively investigated in recent decades. Their physical and chemical properties, such as hydrophilicity, resemblance to living systems, swelling ability and modifiability, make them suitable to be exploited for many pharmaceutical and bioengineering applications. This review deals with a brief account of green-manufactured hydrogels, their characteristics, preparations, importance in the field of green biomedical technology and their future perspectives. Only hydrogels based on biopolymers, and primarily on polysaccharides, are considered. Particular attention is given to the processes of extracting such biopolymers from natural sources and the various emerging problems for their processing, such as solubility. Hydrogels are catalogued according to the main biopolymer on which they are based and, for each type, the chemical reactions and the processes that enable their assembly are identified. The economic and environmental sustainability of these processes are commented on. The possibility of large-scale processing in the production of the investigated hydrogels are framed in the context of an economy aimed at waste reduction and resource recycling.

The model pH-controlled delivery system based on gelatin-tannin hydrogels containing ferrous ascorbate: iron releasein vitro

Hydrogels have become an essential class among all biomaterials. The specialized biomaterials are highly valued in the field of biomedical applications. One of the problems in wound management is local microelement deficiency associated with extensive wound lesions. The significant lack of elemental iron in the human body leads to serious consequences and prolongs treatment. The synthesis of gelatin-tannin hydrogels with ion delivery function is proposed in this study. The ability to release ions in low acid solution is a sphere of great interest. The pH drop in the wound cavity is usually associated with the contamination of some bacterial cultures. pH-controlled delivery of iron in buffer solutions (рН = 5.5/6.4/7.4) was considered for these hydrogels. The kinetics of iron release was determined by visible spectroscopy. Theoretical models were applied to describe the process of ion delivery. The structure of materials was examined by IR-spectroscopy and demonstrated the incorporation of ferrous ascorbate into hydrogel matrix. Thermal analysis was used to point out the key differences in thermal behavior by isoconversional methods (Flynn-Wall-Ozawa/Kissinger-Akahira-Sunose). The mechanical properties of the materials have been studied. The effect of iron ascorbate on polymer network parameters was discussed. The current study demonstrated the possibility of obtaining gelatin-tannin hydrogels for pH-dependent iron delivery. That provides future perspectives to expand the set of releasing microelements for biomedical applications.

Improved Conductivity in Gellan Gum and Montmorillonite Nanocomposites Electrolytes

Nanocomposite polymer electrolytes (NPEs) were obtained using gellan gum (GG) and 1 to 40 wt.% of montmorillonite (Na⁺SYN-1) clay. The NPEs were crosslinked with formaldehyde, plasticized with glycerol, and contained LiClO₄. The samples were characterized by impedance spectroscopy, thermal analyses (TGA and DSC), UV-vis transmittance and reflectance, X-ray diffraction (XRD), and continuous-wave electron paramagnetic resonance (CW-EPR). The NPEs of GG and 40 wt.% LiClO₄ showed the highest conductivity of 2.14 × 10^-6 and 3.10 × 10^-4 S/cm at 30 and 80 °C, respectively. The samples with 10 wt.% Na⁺SYN-1 had a conductivity of 1.86 × 10^-5 and 3.74 × 10^-4 S/cm at 30 and 80 °C, respectively. TGA analyses revealed that the samples are thermally stable up to 190 °C and this did not change with clay addition. The transparency of the samples decreased with the increase in the clay content and at the same time their reflectance increased. Finally, CW-EPR was performed to identify the coordination environment of Cu²⁺ ions in the GG NPEs. The samples doped with the lowest copper concentration exhibit the typical EPR spectra due to isolated Cu²⁺ ions in axially distorted sites. At high concentrations, the spectra become isotropic because of dipolar and exchange magnetic effects. In summary, GG/clay NPEs presented good ionic conductivity results, which qualifies them for electrochemical device applications.

Design and Investigation of an Eco-Friendly Wound Dressing Composed of Green Bioresources- Soy Protein, Tapioca Starch, and Gellan Gum

In the fields of biomedicine and tissue engineering, natural polymer-based tissue-engineered scaffolds are used in multiple applications. As a plant-derived polymer, soy protein, containing multiple amino acids, is structurally similar to components of the extra-cellular matrix (ECM) of tissues. It is biological safety provided a good potential to be material for pure natural scaffolds. Moreover, as a protein, the properties of soy protein can be easily adjusted by modifying the functional groups on it. In addition, by blending soy protein with other synthetic and natural polymers, the mechanical characteristics and bioactive behavior of scaffolds can be facilitated for a variety of bio-applications. In this research, soy protein and polysaccharides tapioca starch are used, and gellan gum to develop a protein-based composite scaffold for cell engineering. The morphology and surface chemical composition are characterized via micro-computed tomography (micro-CT), scanning electron microscope (SEM), and fourier-transform infrared (FTIR) spectroscopy. The soy/tapioca/gellan gum (STG) composite scaffolds selectively help the adhesion and proliferation of L929 fibroblast cells while improving the migration of L929 fibroblast cells in STG composite scaffolds as the increase of soy protein proportion of the scaffold. In addition, STG composite scaffolds show great potential in the wound healing model to enhance rapid epithelialization and tissue granulation.

Gellan Gum in Wound Dressing Scaffolds

Several factors, such as bacterial infections, underlying conditions, malnutrition, obesity, ageing, and smoking are the most common issues that cause a delayed process of wound healing. Developing wound dressings that promote an accelerated wound healing process and skin regeneration is crucial. The properties of wound dressings that make them suitable for the acceleration of the wound healing process include good antibacterial efficacy, excellent biocompatibility, and non-toxicity, the ability to provide a moist environment, stimulating cell migration and adhesion, and providing gaseous permeation. Biopolymers have demonstrated features appropriate for the development of effective wound dressing scaffolds. Gellan gum is one of the biopolymers that has attracted great attention in biomedical applications. The wound dressing materials fabricated from gellan gum possess outstanding properties when compared to traditional dressings, such as good biocompatibility, biodegradability, non-toxicity, renewability, and stable nature. This biopolymer has been broadly employed for the development of wound dressing scaffolds in different forms. This review discusses the physicochemical and biological properties of gellan gum-based scaffolds in the management of wounds.

Clay-Based Nanocomposite Hydrogels for Biomedical Applications: A Review

In recent decades, new and improved materials have been developed with a significant interest in three-dimensional (3D) scaffolds that can cope with the diverse needs of the expanding biomedical field and promote the required biological response in multiple applications. Due to their biocompatibility, ability to encapsulate and deliver drugs, and capacity to mimic the extracellular matrix (ECM), typical hydrogels have been extensively investigated in the biomedical and biotechnological fields. The major limitations of hydrogels include poor mechanical integrity and limited cell interaction, restricting their broad applicability. To overcome these limitations, an emerging approach, aimed at the generation of hybrid materials with synergistic effects, is focused on incorporating nanoparticles (NPs) within polymeric gels to achieve nanocomposites with tailored functionality and improved properties. This review focuses on the unique contributions of clay nanoparticles, regarding the recent developments of clay-based nanocomposite hydrogels, with an emphasis on biomedical applications.

Adjusting Some Properties of Poly(methacrylic acid) (Nano)Composite Hydrogels by Means of Silicon-Containing Inorganic Fillers

The present work aims to show how the main properties of poly(methacrylic acid) (PMAA) hydrogels can be engineered by means of several silicon-based fillers (Laponite XLS/XLG, montmorillonite (Mt), pyrogenic silica (PS)) employed at 10 wt% concentration based on MAA. Various techniques (FT-IR, XRD, TGA, SEM, TEM, DLS, rheological measurements, UV-VIS) were used to comparatively study the effect of these fillers, in correlation with their characteristics, upon the structure and swelling, viscoelastic, and water decontamination properties of (nano)composite hydrogels. The experiments demonstrated that the nanocomposite hydrogel morphology was dictated by the way the filler particles dispersed in water. The equilibrium swelling degree (SDe) depended on both the pH of the environment and the filler nature. At pH 1.2, a slight crosslinking effect of the fillers was evidenced, increasing in the order Mt < Laponite < PS. At pH > pKaMAA (pH 5.4; 7.4; 9.5), the Laponite/Mt-containing hydrogels displayed a higher SDe as compared to the neat one, while at pH 7.4/9.5 the PS-filled hydrogels surprisingly displayed the highest SDe. Rheological measurements on as-prepared hydrogels showed that the filler addition improved the mechanical properties. After equilibrium swelling at pH 5.4, G’ and G” depended on the filler, the Laponite-reinforced hydrogels proving to be the strongest. The (nano)composite hydrogels synthesized displayed filler-dependent absorption properties of two cationic dyes used as model water pollutants, Laponite XLS-reinforced hydrogel demonstrating both the highest absorption rate and absorption capacity. Besides wastewater purification, the (nano)composite hydrogels described here may also find applications in the pharmaceutical field as devices for the controlled release of drugs.

Advances in fermentative production, purification, characterization and applications of gellan gum

Multiple microbial exopolysaccharides have been reported in recent decade with their structural and functional features. Gellan gum (GG) is among these emerging biopolymers with versatile properties. Low production yield, high downstream cost, and abundant market demand have made GG a high cost material. Hence, an understanding on the various possibilities to develop cost-effective gellan gum bioprocess is desirable. This review focuses on details of upstream and downstream process of GG from an industrial perspective. It emphasizes on GG producing Sphingomonas spp., updates on biosynthesis, strain and media engineering, kinetic modeling, bioreactor design and scale-up considerations. Details of the downstream operations with possible modifications to make it cost-effective and environmentally sustainable have been discussed. The updated regulatory criteria for GG as a food ingredient and analytical tools required to validate the same have been briefly discussed. Derivatives of GG and their applications in various industrial segments have also been highlighted.

Laponite-Based Nanomaterials for Drug Delivery

Laponite is a clay-based material composed of synthetic disk-shaped crystalline nanoparticles with highly ionic, large surface area. These characteristics enable the intercalation and dissolution of biomolecules in Laponite-based drug delivery systems. Furthermore, Laponite's innate physicochemical properties and architecture enable the development of tunable pH-responsive drug delivery systems. Laponite's coagulation capacity and cation exchangeability determine its exchange capabilities, drug encapsulation efficiency, and release profile. These parameters are exploited to design highly controlled and efficacious drug delivery platforms for sustained drug release. In this review, they provide an overview of how to design efficient delivery of therapeutics by leveraging the properties and specific interactions of various Laponite-polymer composites and drug moieties.

Fabrication Methods and Form Factors of Gellan Gum-Based Materials for Drug Delivery and Anti-Cancer Applications

Despite the success of cancer therapeutics, off target cell toxicity prevails as one of the main challenges of cancer treatment. Exploration of drug delivery methods is a growing field of research, which involves a variety of materials and processing techniques. A natural polymer, gellan gum presents physicochemical properties that enable drug loading for sustained release in a broad range of environmental conditions and anatomical locations. Gellan gum is an anionic exopolysaccharide, produced via fermentation by Sphingomonas elodea, which gels in the presence of cations. Additionally, it is biocompatible and nontoxic. Multiple physical and chemical gelation processes have been reported for the use of gellan gum in drug delivery applications to produced varying form factors, including hydrogels, nanohydrogels, beads, films, or patches, with tunable mechanical and physicochemical properties. The resulting formulations have shown promising outcomes for drug delivery including improving drug bioavailability, drug solubility, and drug release over time, without compromising biocompatibility or the introduction of adverse effects. This review presents studies in which gellan gum has been processed to enable the delivery of antibiotics, antiallergens, anti-inflammatory, or antifungal molecules with a special focus on drugs for anticancer applications.

Cationic, anionic and neutral polysaccharides for skin tissue engineering and wound healing applications

Today, chronic wound care and management can be regarded as a clinically critical issue. However, the limitations of current approaches for wound healing have encouraged researchers and physicians to develop more efficient alternative approaches. Advances in tissue engineering and regenerative medicine have resulted in the development of promising approaches that can accelerate wound healing and improve the skin regeneration rate and quality. The design and fabrication of scaffolds that can address the multifactorial nature of chronic wound occurrence and provide support for the healing process can be considered an important area requiring improvement. In this regard, polysaccharide-based scaffolds have distinctive properties such as biocompatibility, biodegradability, high water retention capacity and nontoxicity, making them ideal for wound healing applications. Their tunable structure and networked morphology could facilitate a number of functions, such as controlling their diffusion, maintaining wound moisture, absorbing a large amount of exudates and facilitating gas exchange. In this review, the wound healing process and the influential factors, structure and properties of carbohydrate polymers, physical and chemical crosslinking of polysaccharides, scaffold fabrication techniques, and the use of polysaccharide-based scaffolds in skin tissue engineering and wound healing applications are discussed.

Recent trends in gelatin methacryloyl nanocomposite hydrogels for tissue engineering

Gelatin methacryloyl (GelMA), a photocrosslinkable gelatin-based hydrogel, has been immensely used for diverse applications in tissue engineering and drug delivery. Apart from its excellent functionality and versatile mechanical properties, it is also suitable for a wide range of fabrication methodologies to generate tissue constructs of desired shapes and sizes. Despite its exceptional characteristics, it is predominantly limited by its weak mechanical strength, as some tissue types naturally possess high mechanical stiffness. The use of high GelMA concentrations yields high mechanical strength, but not without the compromise in its porosity, degradability, and three-dimensional (3D) cell attachment. Recently, GelMA has been blended with various natural and synthetic biomaterials to reinforce its physical properties to match with the tissue to be engineered. Among these, nanomaterials have been extensively used to form a composite with GelMA, as they increase its biological and physicochemical properties without affecting the unique characteristics of GelMA and also introduce electrical and magnetic properties. This review article presents the recent advances in the formation of hybrid GelMA nanocomposites using a variety of nanomaterials (carbon, metal, polymer, and mineral-based). We give an overview of each nanomaterial's characteristics followed by a discussion of the enhancement in GelMA's physical properties after its incorporation. Finally, we also highlight the use of each GelMA nanocomposite for different applications, such as cardiac, bone, and neural regeneration.

Physicochemical and Rheological Characterization of Different Low Molecular Weight Gellan Gum Products and Derived Ionotropic Crosslinked Hydrogels

A series of four different low molecular weight gellan gum products was obtained by alkaline hydrolysis with the aim to investigate the impact of the molecular weight on the rheological properties of the polysaccharide aqueous dispersions and on the physicochemical characteristics of derived ionotropic crosslinked hydrogels. In particular, thermo-rheological analysis was conducted on aqueous dispersions to study the influence of molecular weight on the thermogelation properties typical of the native polysaccharide while strain sweep experiments were conducted to establish if aqueous dispersion shows a viscoelastic behavior. The effect of different Ca2+ on the rheological properties of hydrogels were studied. Furthermore, ionotropic crosslinked hydrogels were analyzed in terms of morphology on the dried state and swelling behavior, while their viscoelastic properties were studied by means of rheological analysis conducted in frequency sweep regime after different time points of incubation in phosphate buffer at pH 7.4. Release experiments conducted using fluorescein isothiocyanate labelled dextran as a model diffusion agent and was performed to investigate the possibility of using the low molecular weight GG-derived hydrogels as an active molecule-releasing device. Finally, the cytocompatibility of hydrolysis products was investigated, as well as the capacity of hydrogels to encapsulate viable MC3T3-E1 preosteoblastic cells.

Anti-fatigue, highly resilient photocrosslinkable gellan gum hydrogels reinforced by flexible nanoparticulate polyurethane multi-crosslinkers

In this study, multifunctional polyurethane nanoparticles (MPUNs) were embedded into the methacrylated gellan gum (MGG) to prepare stimuli-responsive hydrogels with improved mechanical properties including remarkable fatigue resistance and excellent self-recoverability. The photocurable MPUNs/MGG nanocomposite hydrogels with different formulations were synthesized through a facile and green solution mixing method. The result obtained from mechanical analysis displayed an excellent improvement in compression strength (120 6 ± 83.7 kPa) and ultimate strain (94.2 ± 2.7%) in the optimized formulation. Furthermore, the optimized formulation could restore approximately its original shape after continuous loading-unloading compression tests over 100 cycles which might result from its favorable crosslinked structure. These reinforced hydrogels exhibited a dual physical and chemical crosslinking mechanism based on the hydrogen bonding formation and photocrosslinking of methacrylate functional groups, respectively. Interestingly, the nanocomposite hydrogels exhibited no significant cytotoxicity to human dermal fibroblast cells which made them suitable as the appropriate biomaterials for the engineering of soft tissues.

Multifunctional hydrogels for wound healing: Special focus on biomacromolecular based hydrogels

Hydrogels are widely used for wound healing applications due to their similarity to the native extracellular matrix (ECM) and ability to provide a moist environment. However, lack of multifunctionality and low mechanical properties of previously developed hydrogels may limit their ability to support skin tissue regeneration. Incorporating various biomaterials and nanostructures into the hydrogels is an emerging approach to develop multifunctional hydrogels with new functions that are beneficial for wound healing. These multifunctional hydrogels can be fabricated with a wide range of functions and properties, including antibacterial, antioxidant, bioadhesive, and appropriate mechanical properties. Two approaches can be used for development of multifunctional hydrogel-based dressings; taking the advantages of the chemical composition of biomaterials and addition of nanomaterials or nanostructures. A large number of synthetic and natural polymers, bioactive molecules, or nanomaterials have been used to obtain hydrogel-based dressings with multifunctionality for wound healing applications. In the present review paper, advances in the development of multifunctional hydrogel-based dressings for wound healing have been highlighted.

Salecan-Clay Based Polymer Nanocomposites for Chemotherapeutic Drug Delivery Systems; Characterization and In Vitro Biocompatibility Studies

Salecan is a microbial polysaccharide suitable to obtain hydrogel for biomedical applications due to the excellent hydrophilicity and biocompatibility properties. In this work, Salecan of different concentrations was introduced into polymethacrylic acid (PMAA) in the presence of clay to form novel semi synthetic hydrogel nanocomposites systems and loaded afterwards with doxorubicin (DOX). The physical-chemical characteristics of the nanocomposites systems and their effect on the viability, and morphology of MDBK (Madin-Darby bovine kidney), HT-29 human colorectal adenocarcinoma and Colo 205 human colon adenocarcinoma cell lines were investigated. DOX release from the nanocomposite systems, cell up-take and subsequent effect on cell proliferation was also analyzed. It was found that Salecan concentration determined the swelling behavior, structural parameters and morphological features of the nanocomposite systems. The hydrogen bonds strongly influenced the formation of PMAA-Salecan-clay systems, each component bringing its own contribution, thus demonstrating the achievement of an advanced crosslinked network and a more compacted hydrogel nanocomposite morphology. All the synthesized nanocomposites had negligible toxicity to normal MDBK cells and chemoresistent HT-29 cell line, whereas in the case of Colo 205 cells a decrease by 40% of the cell viability was obtained for the sample containing the highest amount of Salecan. This effect was correlated with the lowest pore size distribution leading to highest available specific surface area and entrapped amount of DOX which was further released from the nanocomposite sample. Corroborating all the data it can be suggested that the synthesized nanocomposites with Salecan and clay could be good candidates as vehicles for chemotherapeutic agents.

Microbial Exopolysaccharides as Drug Carriers

Microbial exopolysaccharides are peculiar polymers that are produced by living organisms and protect them against environmental factors. These polymers are industrially recovered from the medium culture after performing a fermentative process. These materials are biocompatible and biodegradable, possessing specific and beneficial properties for biomedical drug delivery systems. They can have antitumor activity, they can produce hydrogels with different characteristics due to their molecular structure and functional groups, and they can even produce nanoparticles via a self-assembly phenomenon. This review studies the potential use of exopolysaccharides as carriers for drug delivery systems, covering their versatility and their vast possibilities to produce particles, fibers, scaffolds, hydrogels, and aerogels with different strategies and methodologies. Moreover, the main properties of exopolysaccharides are explained, providing information to achieve an adequate carrier selection depending on the final application.

Interleukin-4-loaded hydrogel scaffold regulates macrophages polarization to promote bone mesenchymal stem cells osteogenic differentiation via TGF-β1/Smad pathway for repair of bone defect

Objective

Tissue engineering is a promising strategy for repair of large bone defect. However, the immune system reactions to biological scaffold are increasingly being recognized as a crucial factor influencing regeneration efficacy. In this study, a bone‐bioactive hydrogel bead loaded with interleukin‐4 (IL‐4) was used to regulate macrophages polarization and accelerate bone regeneration.

Methods

IL‐4‐loaded calcium‐enriched gellan gum (Ca‐GG + IL‐4) hydrogel beads were synthesised. And the effect on cell behaviour was detected. Furthermore, the effect of the Ca‐GG + IL‐4 hydrogel bead on macrophage polarization and the effect of macrophage polarization on bone mesenchymal stem cells (BMSCs) apoptosis and osteogenic differentiation were evaluated in vitro and in vivo.

Results

BMSCs were able to survive in the hydrogel regardless of whether IL‐4 was incorporated. Immunofluorescence staining and qPCR results revealed that Ca‐GG + IL‐4 hydrogel bead could promote M2 macrophage polarization and increase transforming growth factor (TGF)‐β1 expression level, which activates the TGF‐β1/Smad signalling pathway in BMSCs and promotes osteogenic differentiation. Moreover, immunohistochemical analysis demonstrated Ca‐GG + IL‐4 hydrogel bead could promote M2 macrophage polarization and reduce cell apoptosis in vivo. In addition, micro‐CT and immunohistochemical analysis at 12 weeks post‐surgery showed that Ca‐GG + IL‐4 hydrogel bead could achieve superior bone defect repair efficacy in vivo.

Conclusions

The Ca‐GG + IL‐4 hydrogel bead effectively promoted bone defect regeneration via regulating macrophage polarization, reducing cell apoptosis and promoting BMSCs osteogenesis through TGF‐β1/Smad pathway. Therefore, it is a promising strategy for repair of bone defect.

Materials engineering, processing, and device application of hydrogel nanocomposites

Hydrogels are widely implemented as key materials in various biomedical applications owing to their soft, flexible, hydrophilic, and quasi-solid nature. Recently, however, new material properties over those of bare hydrogels have been sought for novel applications. Accordingly, hydrogel nanocomposites, i.e., hydrogels converged with nanomaterials, have been proposed for the functional transformation of conventional hydrogels. The incorporation of suitable nanomaterials into the hydrogel matrix allows the hydrogel nanocomposite to exhibit multi-functionality in addition to the biocompatible feature of the original hydrogel. Therefore, various hydrogel composites with nanomaterials, including nanoparticles, nanowires, and nanosheets, have been developed for diverse purposes, such as catalysis, environmental purification, bio-imaging, sensing, and controlled drug delivery. Furthermore, novel technologies for the patterning of such hydrogel nanocomposites into desired shapes have been developed. The combination of such material engineering and processing technologies has enabled the hydrogel nanocomposite to become a key soft component of electronic, electrochemical, and biomedical devices. We herein review the recent research trend in the field of hydrogel nanocomposites, particularly focusing on materials engineering, processing, and device applications. Furthermore, the conclusions are presented with the scope of future research outlook, which also includes the current technical limitations.

Hydrogel-clay Nanocomposites as Carriers for Controlled Release

The present review aims to summarize the research efforts undertaken in the last few years in the development and testing of hydrogel-clay nanocomposites proposed as carriers for controlled release of diverse drugs. Their advantages, disadvantages and different compositions of polymers/biopolymers with diverse types of clays, as well as their interactions are discussed. Illustrative examples of studies regarding hydrogel-clay nanocomposites are detailed in order to underline the progressive researches on hydrogel-clay-drug pharmaceutical formulations able to respond to a series of demands for the most diverse applications. Brief descriptions of the different techniques used for the characterization of the obtained complex hybrid materials such as: swelling, TGA, DSC, FTIR, XRD, mechanical, SEM, TEM and biology tests, are also included. Enlightened by the presented data, we can suppose that hydrogel-clay nanocomposites will still be a challenging subject of global assiduous researches. We can dare to dream to an efficient drug delivery platform for the treatment of multiple affection concomitantly, these being undoubtedly like "a tree of life" bearing different kinds of fruits and leaves proper for human healing.

Natural Inorganic Ingredients in Wound Healing

Background:

One of the major clinical challenges is to achieve a rapid and efficient treatment of complex chronic wounds. Nowadays, most wound dressings currently available are unable to find a solution the challenges of resistance to bacterial infection, protein adsorption and increased levels of exudates. Natural inorganic ingredients (clay minerals, metal cations, zeolites, etc) could be the key to solve the problem satisfactorily. Some of these materials have shown biocompatibility and ability to enhance cell adhesion, proliferation and cellular differentiation and uptake. Besides, some natural inorganic ingredients effectively retain drugs, allowing the design of drug delivery matrices.

Objective:

possibilities of natural inorganic ingredients in wound healing treatments have been reviewed, the following sections have been included: 1. Introduction 2. Functions of Inorganic Ingredients in wound healing 2.1. Antimicrobial effects 2.2. Hemostatic effects 3. Clay minerals for wound healing 3.1. Clay minerals 3.2. Clay mineral semisolid formulations 3.3. Clay/polymer composites and nanocomposites 3.4. Clay minerals in wound dressings 4. Other inorganic materials for wound healing 4.1. Zeolites 4.2. Silica and other silicates 4.3. Other minerals 4.4. Transition metals 5. Conclusion

Conclusion:

inorganic ingredients possess useful features in the development of chronic wounds advanced treatments. They improve physical (mechanical resistance and water vapor transmission), chemical (release of drugs, hemostasis and/or adsorption of exudates and moisture) and biological (antimicrobial effects and improvement of healing) properties of wound dressings. In summary, inorganic ingredients have proved to be a promising and easily accessible products in the treatment of wounds and, more importantly, chronic wounds.

Laponite-based Nanomaterials for Biomedical Applications: A Review

Laponite based nanomaterials (LBNMs) are highly diverse regarding their mechanical, chemical, and structural properties, coupled with shape, size, mass, biodegradability and biocompatibility. These ubiquitous properties of LBNMs make them appropriate materials for extensive applications. These have enormous potential for effective and targeted drug delivery comprised of numerous biodegradable materials which results in enhanced bioavailability. Moreover, the clay material has been explored in tissue engineering and bioimaging for the diagnosis and treatment of various diseases. The material has been profoundly explored for minimized toxicity of nanomedicines. The present review compiled relevant and informative data to focus on the interactions of laponite nanoparticles and application in drug delivery, tissue engineering, imaging, cell adhesion and proliferation, and in biosensors. Eventually, concise conclusions are drawn concerning biomedical applications and identification of new promising research directions.

Application of Gellan Gum-Based Scaffold for Regenerative Medicine

Gellan gum (GG) is a linear microbial exopolysaccharide which is derived naturally by the fermentation process of Pseudomonas elodea. Application of GG in tissue engineering and regeneration medicine (TERM) is already over 10 years and has shown great potential. Although this biomaterial has many advantages such as biocompatibility, biodegradability, nontoxic in nature, and physical stability in the presence of cations, a variety of modification methods have been suggested due to some disadvantages such as mechanical properties, high gelation temperature, and lack of attachment sites. In this review, the application of GG-based scaffold for tissue engineering and approaches to improve GG properties are discussed. Furthermore, a recent trend and future perspective of GG-based scaffold are highlighted.

Carboxymethyl konjac glucomannan mechanically reinforcing gellan gum microspheres for uranium removal

Biosorbents have been a promising adsorbent to remove uranium while their poor mechanical properties prevent them from being widely used in practice. In this study, carboxymethyl konjac glucomannan (CMKGM) was incorporated to gellan gum to form a double-network gel micro spheres (CMKGM/GG-Al) for uranium removal with its mechanical strength fairly being reinforced. The compressive strength of the CMKGM/GG-Al microspheres was about 6 times than that of GG-Ca microspheres we prepared before while the adsorption capacity still be at a better value with the fitting maximum adsorption capacity being of 97.94 mg/g. Its uranium adsorption properties were investigated by considering the influence of pH, the adsorbent dosage, temperature, initial uranium concentration, time and coexisting ions. The adsorption mechanism was also investigated according to the SEM, EDX, FT-IR and XPS data analysis. The isotherm equilibrium data which were best fitted with Langmuir model and the kinetics data which were best fitted with pseudo-second-order model. It was inferred that the adsorption process was mainly the ion-exchange and the coordination with hydroxyl groups on the adsorbent surface and the adsorption process was endothermic and spontaneous. The CMKGM/GG-Al microspheres prepared in this study would be more conducive to practical application for uranium removal.

Biological Role of Gellan Gum in Improving Scaffold Drug Delivery, Cell Adhesion Properties for Tissue Engineering Applications

Over the past few decades, gellan gum (GG) has attracted substantial research interest in several fields including biomedical and clinical applications. The GG has highly versatile properties like easy bio-fabrication, tunable mechanical, cell adhesion, biocompatibility, biodegradability, drug delivery, and is easy to functionalize. These properties have put forth GG as a promising material in tissue engineering and regenerative medicine fields. Nevertheless, GG alone has poor mechanical strength, stability, and a high gelling temperature in physiological conditions. However, GG physiochemical properties can be enhanced by blending them with other polymers like chitosan, agar, sodium alginate, starch, cellulose, pullulan, polyvinyl chloride, xanthan gum, and other nanomaterials, like gold, silver, or composites. In this review article, we discuss the comprehensive overview and different strategies for the preparation of GG based biomaterial, hydrogels, and scaffolds for drug delivery, wound healing, antimicrobial activity, and cell adhesion. In addition, we have given special attention to tissue engineering applications of GG, which can be combined with another natural, synthetic polymers and nanoparticles, and other composites materials. Overall, this review article clearly presents a summary of the recent advances in research studies on GG for different biomedical applications.

Enriched Gellan Gum hydrogel as visco-supplement

Viscosupplementation, i.e. intra-articular injection of hyaluronic acid derivatives, is considered as the most effective treatment for patients with mild to moderate osteoarthritis. Even if hyaluronic acid is still considered as the gold standard, research is now focusing on the development of new products with enhanced injectability and yet reasonable viscoelastic behavior for OA treatment. A Gellan Gum (GG) hydrogel was synthesized and coated with crosslinked polyvinyl alcohol (PVA) to protect the polysaccharide from degradation during sterilization and improve its performance for the foreseen application. Thermal analyses indicated that mixed hydrogel showed a higher degree of structuring than the bare polysaccharide core without losing its swelling properties, thanks to the hydrophylicity of both coating and cross-linking agent. The PVA coating increased elastic and viscous moduli of the polysaccharide core conferring it a higher resistance to shear and compression and better thixotropic properties. Despite the double crosslinking, hydrogel was injectable. Cytocompatibility towards chondrocytes was verified.

Printing bone in a gel: using nanocomposite bioink to print functionalised bone scaffolds

Free-form printing offers a novel biofabrication approach to generate complex shapes by depositing hydrogel materials within a temporary supportive environment. However, printed hydrogels typically lack the requisite mechanical properties and functionality of the desired tissue, limiting application and, more importantly, safety and efficacy of the implant. The study authors have developed an innovative nanoclay-based bioink to print high shape fidelity functional constructs for potential skeletal application. Laponite® (LAP) nanoclay was combined with gellan gum (GG) to generate a printable hydrogel that was highly stable in vitro, displayed limited swelling ability compared with the silicate-free control and remained stable over time. An agarose fluid gel was found to provide the requisite support for the deposition of the material ink and preservation of the printed structure before crosslinking. Printed C2C12 myoblasts remained viable and displayed extensive proliferation over 21 days in culture. Cell-laden scaffolds demonstrated functionality within 1 day of culture in vitro and that was preserved over 3 weeks. Analysis of absorption and release mechanisms from LAP-GG using model proteins (lysozyme and bovine serum albumin) demonstrated the retention capability of the clay-based materials for compound localisation and absence of burst release. Vascular endothelial growth factor ​was loaded within the agarose fluid gel and absorbed by the material ink via absorption during deposition. The 3D-printed constructs were implanted on the chorioallantoic membrane of a 10-day-old developing chick. Extensive and preferential vasculature infiltration was observed in LAP-GG-loaded vascular endothelial growth factor constructs compared with controls (p<0.01 and p<0.0001) after only 7 days of incubation. The current studies demonstrate, for the first time, the application of innovative LAP-GG 3D constructs in the generation of growth factor-loaded 3D constructs for potential application in skeletal tissue repair.

Design of modular gellan gum hydrogel functionalized with avidin and biotinylated adhesive ligands for cell culture applications

This article proposes the coupling of the recombinant protein avidin to the polysaccharide gellan gum to create a modular hydrogel substrate for 3D cell culture and tissue engineering. Avidin is capable of binding biotin, and thus biotinylated compounds can be tethered to the polymer network to improve cell response. The avidin is successfully conjugated to gellan gum and remains functional as shown with fluorescence titration and electrophoresis (SDS-PAGE). Self-standing hydrogels were formed using bioamines and calcium chloride, yielding long-term stability and adequate stiffness for 3D cell culture, as confirmed with compression testing. Human fibroblasts were successfully cultured within the hydrogel treated with biotinylated RGD or biotinylated fibronectin. Moreover, human bone marrow stromal cells were cultured with hydrogel treated with biotinylated RGD over 3 weeks. We demonstrate a modular and inexpensive hydrogel scaffold for cell encapsulation that can be equipped with any desired biotinylated cell ligand to accommodate a wide range of cell types.

Fabrication and Characterization of Composite Meshes Loaded with Antimicrobial Peptides

Biomaterials-centered infection or implant-associated infection plays critical roles in all areas of medicine with implantable devices. The widespread over use of antibiotics has caused severe bacterial resistance and even super bugs. Therefore, the development of anti-infection implantable devices with non-antibiotic-based new antimicrobial agents is indeed a priority for all of us. In this study, antimicrobial composite meshes were fabricated with broad-spectrum antimicrobial peptides (AMPs). Macroporous polypropylene meshes with poly-caprolactone electrospun nanosheets were utilized as a substrate to load AMPs and gellan gum presented as a media to gel with AMPs. Different amounts of AMPs were loaded onto gellan gum to determine the appropriate dose. The surface morphologies, Fourier-transform infrared spectroscopy spectra, in vitro release profiles, mechanical performances, in vitro antimicrobial properties, and cytocompatibility of composite scaffolds were evaluated. Results showed that AMPs were loaded into the meshes successfully, the in vitro release of AMPs in phosphate-buffered saline was prolonged, and less than 60% peptides were released in 10 days. The mechanical properties of composite meshes were also within the scope of several commercial surgical meshes. Composite meshes with the AMP loading amount of over 3 mg/cm² showed inhibition against both Gram-negative and Gram-positive bacteria effectively, while they presented no toxicity to mammalian cells even at a loading amount of 10 mg/cm². These results demonstrate a new simple and practicable method to offer antimicrobial properties to medical devices for hernia repair.

Gellan Gum/Laponite Beads for the Modified Release of Drugs: Experimental and Modeling Study of Gastrointestinal Release

In this study, gellan gum (GG), a natural polysaccharide, was used to fabricate spherical porous beads suitable as sustained drug delivery systems for oral administration. GG was cross-linked with calcium ions to prepare polymeric beads. Rheological studies and preliminary experiments of beads preparation allowed to identify the GG and the CaCl2 concentrations suitable for obtaining stable and spherical particles. GG beads were formed, through ionotropic gelation technique, with and without the presence of the synthetic clay laponite. The resultant beads were analyzed for dimensions (before and after freeze-drying), morphological aspects and ability to swell in different media miming biological fluids, namely SGF (Simulated Gastric Fluid, HCl 0.1 M) and SIF (Simulated Intestinal Fluid, phosphate buffer, 0.044 M, pH 7.4). The swelling degree was lower in SGF than in SIF and further reduced in the presence of laponite. The GG and GG-layered silicate composite beads were loaded with two model drugs having different molecular weight, namely theophylline and cyanocobalamin (vitamin B12) and subjected to in-vitro release studies in SGF and SIF. The presence of laponite in the bead formulation increased the drug entrapment efficiency and slowed-down the release kinetics of both drugs in the gastric environment. A moving-boundary swelling model with "diffuse" glassy-rubbery interface was proposed in order to describe the swelling behavior of porous freeze-dried beads. Consistently with the swelling model adopted, two moving-boundary drug release models were developed to interpret release data from highly porous beads of different drugs: drug molecules, e.g., theophylline, that exhibit a typical Fickian behavior of release curves and drugs, such as vitamin B12, whose release curves are affected by the physical/chemical interaction of the drug with the polymer/clay complex. Theoretical results support the experimental observations, thus confirming that laponite may be an effective additive for fabricating sustained drug delivery systems.

Stem cell-inspired secretome-rich injectable hydrogel to repair injured cardiac tissue

The objective of this study was to develop an injectable and biocompatible hydrogel that can deliver a cocktail of therapeutic biomolecules (secretome) secreted by human adipose-derived stem cells (hASCs) to the peri-infarct myocardium. Gelatin and Laponite® were combined to formulate a shear-thinning, nanocomposite hydrogel (nSi Gel) as an injectable carrier of secretome (nSi Gel+). The growth factor composition and the pro-angiogenic activity of the secretome were tested in vitro by evaluating the proliferation, migration and tube formation of human umbilical endothelial cells. The therapeutic efficacy of the nSi Gel + system was then investigated in vivo in rats by intramyocardial injection into the peri-infarct region. Subsequently, the inflammatory response, angiogenesis, scar formation, and heart function were assessed. Biocompatibility of the developed nSi Gel was confirmed by quantitative PCR and immunohistochemical tests which showed no significant differences in the level of inflammatory genes, microRNAs, and cell marker expression compared to the untreated control group. In addition, the only group that showed a significant increase in capillary density, reduction in scar area and improved cardiac function was treated with the nSi Gel+. Our in vitro and in vivo findings demonstrate the potential of this new secretome-loaded hydrogel as an alternative strategy to treat myocardial infarction.

STATEMENT OF SIGNIFICANCE

Stem cell based-therapies represent a possible solution to repair damaged myocardial tissue by promoting cardioprotection, angiogenesis, and reduced fibrosis. However, recent evidence indicates that most of the positive outcomes are likely due to the release of paracrine factors (cytokines, growth factors, and exosomes) from the cells and not because of the local engraftment of stem cells. This cocktail of essential growth factors and paracrine signals is known as secretome can be isolated in vitro, and the biomolecule composition can be controlled by varying stem-cell culture conditions. Here, we propose a straightforward strategy to deliver secretome produced from hASCs by using a nanocomposite injectable hydrogel made of gelatin and Laponite®. The designed secretome-loaded hydrogel represents a promising alternative to traditional stem cell therapy for the treatment of acute myocardial infarction.