Green seaweed-derived polysaccharides: Insights into various bioactivities for biomedical applications

This research work explores the physicochemical characteristics and biological functions of polysaccharides extracted from four selected green seaweed species: Ulva lactuca (UL), Halimeda opuntia (HO), Caulerpa racemosa (CR), and Chaetomorpha antennina (CA). The extracts were investigated for cell-based bio-activities (i.e., cytotoxicity, cell proliferation and migration) using three cell lines (HDF, HaCaT, RAW264.7) reflecting cell models involved in wound healing, as well as anticoagulant activity. Ulvans from UL significantly increased HaCaT (at 0.06 μg/μL) and HDF (at 0.5 μg/μL) cell proliferation. In addition, extracts from CA showed the highest cell migration ability using HDF and HaCaT cells. UL (all fractions), HO-2A, CR-1B, CA-1A and CA-2B fractions improved phagocytosis. Furthermore, RAW264.7 cells treated with fraction CA-1A produced significantly more intracellular NO (pro-inflammatory) within 24 h compared to control (LPs). Green seaweed extracts CA-2A and UL-1A resulted in lower expression of the pro-inflammatory cytokine TNF-α in skin cells (HDF, HaCaT). Caulerpa cold-extracted polysaccharides possessed higher anticoagulant properties. The Ulva (1,4-linked α-l-rhamnose, β-d-glucuronic acid, l-iduronic acid) and CA extracts are promising sources of bioactive therapeutic agents. Our data provide useful insights into the possible biomedical benefits of selected polysaccharides mixtures (i.e., ulvan, sulfated or/and pyruvylated β-d-galactans, sulfated xyloarabinogalactan) for food, pharmaceutical, and biotechnological applications.

Alginate as a Sustainable and Biodegradable Material for Medical and Environmental Applications-The Case Studies

Alginates are salts of alginic acid derived mainly from sea algae of the genus brown algae. They are also synthesized by some bacteria. They belong to negatively charged polysaccharides exhibiting some rheological properties. High plasticity and the ability to modify the structure are the reasons for their application in numerous industries. Moreover, when in contact with the living tissue, they do not trigger an immune response, and for this reason they are the most often tested materials for medical applications. The paper discusses the latest applications, including 3D bioprinting, drug delivery systems, and sorptive properties. Recognizing alginates as biomaterials, it emphasizes the necessity for precise processing and modification to industrialize them for specific uses. This review aims to provide a thorough understanding of the advancements in alginate research, underscoring their potential for innovative applications.

3D printing of gellan-dextran methacrylate IPNs in glycerol and their bioadhesion by RGD derivatives

The ever-growing need for new tissue and organ replacement approaches paved the way for tissue engineering. Successful tissue regeneration requires an appropriate scaffold, which allows cell adhesion and provides mechanical support during tissue repair. In this light, an interpenetrating polymer network (IPN) system based on biocompatible polysaccharides, dextran (Dex) and gellan (Ge), was designed and proposed as a surface that facilitates cell adhesion in tissue engineering applications. The new matrix was developed in glycerol, an unconventional solvent, before the chemical functionalization of the polymer backbone, which provides the system with enhanced properties, such as increased stiffness and bioadhesiveness. Dex was modified introducing methacrylic groups, which are known to be sensitive to UV light. At the same time, Ge was functionalized with RGD moieties, known as promoters for cell adhesion. The printability of the systems was evaluated by exploiting the ability of glycerol to act as a co-initiator in the process, speeding up the kinetics of crosslinking. Following semi-IPNs formation, the solvent was removed by extensive solvent exchange with HEPES and CaCl2, leading to conversion into IPNs due to the ionic gelation of Ge chains. Mechanical properties were investigated and IPNs ability to promote osteoblasts adhesion was evaluated on thin-layer, 3D-printed disk films. Our results show a significant increase in adhesion on hydrogels decorated with RGD moieties, where osteoblasts adopted the spindle-shaped morphology typical of adherent mesenchymal cells. Our findings support the use of RGD-decorated Ge/Dex IPNs as new matrices able to support and facilitate cell adhesion in the perspective of bone tissue regeneration.

Biomedical applications of stimuli-responsive "smart" interpenetrating polymer network hydrogels

In recent years, owing to the ongoing advancements in polymer materials, hydrogels have found increasing applications in the biomedical domain, notably in the realm of stimuli-responsive "smart" hydrogels. Nonetheless, conventional single-network stimuli-responsive "smart" hydrogels frequently exhibit deficiencies, including low mechanical strength, limited biocompatibility, and extended response times. In response, researchers have addressed these challenges by introducing a second network to create stimuli-responsive "smart" Interpenetrating Polymer Network (IPN) hydrogels. The mechanical strength of the material can be significantly improved due to the topological entanglement and physical interactions within the interpenetrating structure. Simultaneously, combining different network structures enhances the biocompatibility and stimulus responsiveness of the gel, endowing it with unique properties such as cell adhesion, conductivity, hemostasis/antioxidation, and color-changing capabilities. This article primarily aims to elucidate the stimulus-inducing factors in stimuli-responsive "smart" IPN hydrogels, the impact of the gels on cell behaviors and their biomedical application range. Additionally, we also offer an in-depth exposition of their categorization, mechanisms, performance characteristics, and related aspects. This review furnishes a comprehensive assessment and outlook for the advancement of stimuli-responsive "smart" IPN hydrogels within the biomedical arena. We believe that, as the biomedical field increasingly demands novel materials featuring improved mechanical properties, robust biocompatibility, and heightened stimulus responsiveness, stimuli-responsive "smart" IPN hydrogels will hold substantial promise for wide-ranging applications in this domain.

Visible light-based 3D bioprinted composite scaffolds of κ-carrageenan for bone tissue engineering applications

Three-dimensional (3D) printing of bone scaffolds using digital light processing (DLP) bioprinting technology empowers the treatment of patients suffering from bone disorders and defects through the fabrication of cell-laden patient-specific scaffolds. Here, we demonstrate the visible-light-induced photo-crosslinking of methacrylate-κ-carrageenan (MA-κ-CA) mixed with bioactive silica nanoparticles (BSNPs) to fabricate 3D composite hydrogels using digital light processing (DLP) printing. The 3D printing of complex bone structures, such as the gyroid, was demonstrated with high precision and resolution. DLP-printed 3D composite hydrogels of MA-κ-CA-BSNP were prepared and systematically assessed for their macroporous structure, swelling, and degradation characteristics. The viscosity, rheological, and mechanical properties were also investigated for the influence of nanoparticle incorporation in the MA-κ-CA hydrogels. The in vitro study performed with MC3T3-E1 pre-osteoblast-laden scaffolds of MA-κ-CA-BSNP revealed high cell viability, no cytotoxicity, and proliferation over 21 days with markedly enhanced osteogenic differentiation compared to neat polymeric scaffolds. Furthermore, no inflammation was observed in the 21-day study involving the in vivo examination of DLP-printed 3D composite scaffolds in a Wistar rat model. Overall, the observed results for the DLP-printed 3D composite scaffolds of MA-κ-CA and BSNP demonstrate their biocompatibility and suitability for bone tissue engineering.

Evaluation of Novel Preformed Particle Gel System for Conformance Control in Mature Oil Reservoirs

To address challenges associated with excessive water production in mature oil reservoirs, this study introduces a carboxymethyl cellulose (CMC)-based material as a novel preformed particle gel (PPG) designed to plug excessive water pathways and redistribute the subsequent injected water toward unswept zones. Through microwave-assisted grafting copolymerization of CMC with acrylamide (AM), we successfully generated multi-sized dry particles within the range of 250-800 µm. Comprehensive analyses, including Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), have confirmed the chemical composition and morphology of the resulting carboxymethyl cellulose-grafted crosslinked polyacrylamide (CMC/PAMBA). Swelling kinetics and rheology tests were conducted to confirm the ability of this novel PPG system to perform at different reservoir conditions. The results of core flooding experiments showed that the CMC/PAMBA PPG is capable of plugging open fractures with a water breakthrough pressure gradient of up to 144 psi/ft. This preformed particle gel (PPG) system was designed specifically for application in Middle East reservoirs, which are distinguished by high salinity and elevated temperature levels. This PPG system is able to swell up to 10 times its original size in seawater and maintain a strength of about 1300 Pa at a temperature of 80 °C. Further optimization is conceivable to enhance injection efficiency and achieve superior plugging outcomes.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Oxidized Xanthan Gum Crosslinked NOCC: Hydrogel System and Their Biological Stability from Oxidation Levels of the Polymer

Dynamic hydrogel systems from N,O-carboxymethyl chitosan (NOCC) are investigated in the past years, which has facilitated their widespread use in many biomedical engineering applications. However, the influence of the polymer's oxidation levels on the hydrogel biological properties is not fully investigated. In this study, chitosan is converted into NOCC and introduced to react spontaneously with oxidized xanthan gum (OXG) to form several injectable hydrogels with controlled degradability. Different oxidation levels of xanthan gum, as well as NOCC/OXG volume ratios, are trialed. The infrared spectroscopy spectra verify chemical modification on OXG and successful crosslinking. With increasing oxidation levels, more dialdehyde groups are introduced into the OXG, resulting in changes in physical properties including gelation, swelling, and self-healing efficiency. Under different volume ratios, the hydrogel shows a stable structure and rigidity with higher mechanical properties, and a slower degradation rate. The shear-thinning and self-healing properties of the hydrogels are confirmed. In vitro assays with L929 cells show the biocompatibility of all formulations although the use of a high amount of OXG15 and OXG25 limited the cell proliferation capacity. Findings in this study suggested a suitable amount of OXG at different oxidation levels in NOCC hydrogel systems for tissue engineering applications.

Recent advances in chitosan-based materials; The synthesis, modifications and biomedical applications

The attention to polymer-based biomaterials, for instance, chitosan and its derivatives, as well as the techniques for using them in numerous scientific domains, is continuously rising. Chitosan is a decomposable naturally occurring polymeric material that is mostly obtained from seafood waste. Because of its special ecofriendly, biocompatible, non- toxic nature as well as antimicrobial properties, chitosan-based materials have received a lot of interest in the field of biomedical applications. The reactivity of chitosan is mainly because of the amino and hydroxyl groups in its composition, which makes it further fascinating for various uses, including biosensing, textile finishing, antimicrobial wound dressing, tissue engineering, bioimaging, gene, DNA and drug delivery and as a coating material for medical implants. This study is an overview of the different types of chitosan-based materials which now a days have been fabricated by applying different techniques and modifications that include etherification, esterification, crosslinking, graft copolymerization and o-acetylation etc. for hydroxyl groups' processes and acetylation, quaternization, Schiff's base reaction, and grafting for amino groups' reactions. Furthermore, this overview summarizes the literature from recent years related to the important applications of chitosan-based materials (i.e., thin films, nanocomposites or nanoparticles, sponges and hydrogels) in different biomedical applications.

Starch-based materials for drug delivery in the gastrointestinal tract-A review

Starch is a natural copolymer with unique physicochemical characteristics. Historically, it has been physically, chemically, or enzymatically modified to obtain ad-hoc functional properties for its use in different applications. In this context, the use of starch-based materials in drug delivery systems (DDSs) has gained great attention mainly because it is cheap, biodegradable, biocompatible, and renewable. This paper reviews the state of the art in starch-based materials design for their use in drug-controlled release with internal stimulus responsiveness; i.e., pH, temperature, colonic microbiota, or enzymes; specifically, those orally administered for its release in the gastrointestinal tract (GIT). Physical-chemical principles in the design of these materials taking into account their response to a particular stimulus are discussed. The relationship between the type of DDSs structure, starch modification routes, and the corresponding drug release profiles are systematically analyzed. Furthermore, the challenges and prospects of starch-based materials for their use in stimulus-responsive DDSs are also debated.

Biodegradable polysaccharide grafted polyacrylamide inhibitor for corrosion in CO2- saturated saline solution

A biodegradable polysaccharide-based inhibitor is grafted with polyacrylamide (PAM) for oilfields' sweet corrosion. The green properties of agar and PAM were incorporated to synthesize an agar-grafted-PAM (AGGPAM) inhibitor. Electrochemical tests of Tafel and AC impedance, were used to determine the corrosion rate of carbon steel (C-steel) and protection efficiency in CO2-saturated 3.5 wt% NaCl solution. The surface morphology was characterized using FESEM coupled with EDX. Results demonstrated the promising performance of AGGPAM in improving steel resistivity, achieving 85% efficiency at 500 mg L-1 and reducing the corrosion rate from 33 to 4.9 mils per year at 25 °C. The electrochemical tests classified AGGPAM as a mixed-type inhibitor, yet with a larger potential to inhibit the cathodic hydrogen evolution. Kinetics study at a temperature of 50 °C revealed a deteriorated AGGPAM inhibition attributed to electrolyte diffusion through the weakly adsorbed AGGPAM film. Nevertheless, the AGGPAM-inhibited solution exhibited a corrosion rate of 26.7 mils per year at 50 °C, which is still lower than that of blank at 25 °C. The steel resistance was diminished from 1436 to 355 Ω cm2 at 50 °C. Implementing AGGPAM coating reduced the steel corrosion rate to 9.6 mils per year, achieving 71% efficiency. AGGPAM inhibitor toxicity was evaluated using ADMETlab, which predicted negligible hazardous impacts. Lastly, potentiostatic testing of steel with AGGPAM at an applied potential of 50 mV illustrated surface protection and decreased current over a prolonged time. Herein, the experimental investigation revealed the promising capabilities of AGGPAM as an efficient corrosion inhibitor in oilfields.

Synthesis and Characterization of Multi-Reducing-End Polysaccharides

Site-specific modification is a great challenge for polysaccharide scientists. Chemo- and regioselective modification of polysaccharide chains can provide many useful natural-based materials and help us illuminate fundamental structure-property relationships of polysaccharide derivatives. The hemiacetal reducing end of a polysaccharide is in equilibrium with its ring-opened aldehyde form, making it the most uniquely reactive site on the polysaccharide molecule, ideal for regioselective decoration such as imine formation. However, all natural polysaccharides, whether they are branched or not, have only one reducing end per chain, which means that only one aldehyde-reactive substituent can be added. We introduce a new approach to selective functionalization of polysaccharides as an entrée to useful materials, appending multiple reducing ends to each polysaccharide molecule. Herein, we reduce the approach to practice using amide formation. Amine groups on monosaccharides such as glucosamine or galactosamine can react with carboxyl groups of polysaccharides, whether natural uronic acids like alginates, or derivatives with carboxyl-containing substituents such as carboxymethyl cellulose (CMC) or carboxymethyl dextran (CMD). Amide formation is assisted using the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM). By linking the C2 amines of monosaccharides to polysaccharides in this way, a new class of polysaccharide derivatives possessing many reducing ends can be obtained. We refer to this class of derivatives as multi-reducing-end polysaccharides (MREPs). This new family of derivatives creates the potential for designing polysaccharide-based materials with many potential applications, including in hydrogels, block copolymers, prodrugs, and as reactive intermediates for other derivatives.

Application of plant products in the synthesis and functionalisation of biopolymers

The burning of plastic trash contributes significantly to the problem of air pollution. Consequently, a wide variety of toxic gases get released into the atmosphere. It is of the utmost importance to develop biodegradable polymers that retain the same characteristics as those obtained from petroleum. In order to decrease the effect that these issues have on the world around us, we need to focus our attention on specific alternative sources capable of biodegrading in their natural environments. Biodegradable polymers have garnered much attention since they can break down through the processes carried out by living creatures. Biopolymers' applications are growing due to their non-toxic nature, biodegradability, biocompatibility, and environmental friendliness. In this regard, we examined numerous methods used to manufacture biopolymers and the critical components from which they get their functional properties. In recent years, economic and environmental concerns have reached a tipping point, increasing production based on sustainable biomaterials. This paper examines plant-based biopolymers as a good resource with potential applications in both biological and non-biological sectors. Scientists have devised various biopolymer synthesis and functionalization techniques to maximize its utility in various applications. In conclusion, recent developments in the functionalization of biopolymers through various plant products and their applications are discussed.

The Integration of Biopolymer-Based Materials for Energy Storage Applications: A Review

Biopolymers are an emerging class of novel materials with diverse applications and properties such as superior sustainability and tunability. Here, applications of biopolymers are described in the context of energy storage devices, namely lithium-based batteries, zinc-based batteries, and capacitors. Current demand for energy storage technologies calls for improved energy density, preserved performance overtime, and more sustainable end-of-life behavior. Lithium-based and zinc-based batteries often face anode corrosion from processes such as dendrite formation. Capacitors typically struggle with achieving functional energy density caused by an inability to efficiently charge and discharge. Both classes of energy storage need to be packaged with sustainable materials due to their potential leakages of toxic metals. In this review paper, recent progress in energy applications is described for biocompatible polymers such as silk, keratin, collagen, chitosan, cellulose, and agarose. Fabrication techniques are described for various components of the battery/capacitors including the electrode, electrolyte, and separators with biopolymers. Of these methods, incorporating the porosity found within various biopolymers is commonly used to maximize ion transport in the electrolyte and prevent dendrite formations in lithium-based, zinc-based batteries, and capacitors. Overall, integrating biopolymers in energy storage solutions poses a promising alternative that can theoretically match traditional energy sources while eliminating harmful consequences to the environment.

A Review of 3D Polymeric Scaffolds for Bone Tissue Engineering: Principles, Fabrication Techniques, Immunomodulatory Roles, and Challenges

Over the last few years, biopolymers have attracted great interest in tissue engineering and regenerative medicine due to the great diversity of their chemical, mechanical, and physical properties for the fabrication of 3D scaffolds. This review is devoted to recent advances in synthetic and natural polymeric 3D scaffolds for bone tissue engineering (BTE) and regenerative therapies. The review comprehensively discusses the implications of biological macromolecules, structure, and composition of polymeric scaffolds used in BTE. Various approaches to fabricating 3D BTE scaffolds are discussed, including solvent casting and particle leaching, freeze-drying, thermally induced phase separation, gas foaming, electrospinning, and sol-gel techniques. Rapid prototyping technologies such as stereolithography, fused deposition modeling, selective laser sintering, and 3D bioprinting are also covered. The immunomodulatory roles of polymeric scaffolds utilized for BTE applications are discussed. In addition, the features and challenges of 3D polymer scaffolds fabricated using advanced additive manufacturing technologies (rapid prototyping) are addressed and compared to conventional subtractive manufacturing techniques. Finally, the challenges of applying scaffold-based BTE treatments in practice are discussed in-depth.

Recent advances on injectable nanocomposite hydrogels towards bone tissue rehabilitation

There has been significant interest in the recent past to develop injectable hydrogel scaffolds that follow minimally invasive implantation procedures towards efficient healing and regeneration of defective bone tissues. Such scaffolds offer several advantages, as they can be injected into the irregularly shaped defect and can act as a low‐density aqueous reservoir, incorporating necessary components for bone tissue repair and augmentation. Considering that bone is a biocomposite of natural biopolymer and bioapatite nanofiller, there has been a growing trend to develop nanocomposite scaffolds by combining biopolymers and inorganic nanofillers to biomimic the hierarchical nanostructure and composition of natural bone. Furthermore, the nanocomposite scaffolds can be tailored to have patient‐specific bone properties, which can lead to better biological responses. The present article begins with the introduction, followed by an overview of polymer matrices, property requirements, and crosslinking techniques employed for injectable hydrogels. Various strategies to develop injectable composites, with emphasis on nanocomposite hydrogels incorporating bioinert and bioactive nanofillers have been discussed. The fundamental challenges related to the development of injectable hydrogel nanocomposite scaffolds and the research efforts directed towards solving these problems have also been reviewed. Finally, future trends and conclusions on new generation injectable hydrogel nanocomposite bone scaffolds have been discussed in this article.

Sulfamic acid grafted to cross-linked chitosan by dendritic units: a bio-based, highly efficient and heterogeneous organocatalyst for green synthesis of 2,3-dihydroquinazoline derivatives

In this work, novel cross-linked chitosan by the G1 dendrimer from condensation of melamine and toluene-2,4-diisocyante terminated by sulfamic acid groups (CS-TDI-Me-TDI-NHSO3H), as a bio-based and heterogeneous acidic organocatalyst, was designed and prepared. Also, the structure of the prepared organocatalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and thermogravimetric analysis/derivative thermogravimetry (TGA/DTA). Subsequently, the catalytic performance of the biobased and dendritic CS-TDI-Me-TDI-NHSO3H, as a multifunctional solid acid, was evaluated for the preparation of 2,3-dihydroquinazoline derivatives through a three-component reaction by following green chemistry principles. Some of the advantages of this new protocol include high to excellent yields and short reaction times as well as easy preparation and remarkable catalyst stability of the introduced acidic organocatalyst. The CS-TDI-Me-TDI-SO3H catalyst can be used for up to five cycles for the preparation of quinazoline derivatives with a slight decrease in its catalytic activity.

Application of Nano-Inspired Scaffolds-Based Biopolymer Hydrogel for Bone and Periodontal Tissue Regeneration

This review's objectives are to provide an overview of the various kinds of biopolymer hydrogels that are currently used for bone tissue and periodontal tissue regeneration, to list the advantages and disadvantages of using them, to assess how well they might be used for nanoscale fabrication and biofunctionalization, and to describe their production processes and processes for functionalization with active biomolecules. They are applied in conjunction with other materials (such as microparticles (MPs) and nanoparticles (NPs)) and other novel techniques to replicate physiological bone generation more faithfully. Enhancing the biocompatibility of hydrogels created from blends of natural and synthetic biopolymers can result in the creation of the best scaffold match to the extracellular matrix (ECM) for bone and periodontal tissue regeneration. Additionally, adding various nanoparticles can increase the scaffold hydrogel stability and provide a number of biological effects. In this review, the research study of polysaccharide hydrogel as a scaffold will be critical in creating valuable materials for effective bone tissue regeneration, with a future impact predicted in repairing bone defects.

Recent advances of chitosan-based polymers in biomedical applications and environmental protection

Interest in polymer-based biomaterials such as chitosan and its modifications and also the methods of their application in various fields of science is uninterruptedly growing. Owing to unique physicochemical, biological, ecological, physiological properties, such as biocompatibility, biodegradability, stability in the natural environment, non-toxicity, high biological activity, economic affordability, chelating of metal ions, high sorption properties, chitosan is used in various biomedical and industrial processes. The reactivity of the amino and hydroxyl groups in the structure makes it more interesting for diverse applications in drug delivery, tissue engineering, wound healing, regenerative medicine, blood anticoagulation and bone, tendon or blood vessel engineering, dentistry, biotechnology, biosensing, cosmetics, water treatment, agriculture. Taking into account the current situation in the world with COVID-19 and other viruses, chitosan is also active in the form of a vaccine system, it can deliver antibodies to the nasal mucosa and load gene drugs that prevent or disrupt the replication of viral DNA/RNA, and deliver them to infected cells. The presented article is an overview of the nowaday state of the application of chitosan, based on literature of recent years, showing importance of fundamental and applied studies aimed to expand application of chitosan-based polymers in many fields of science.

Polysaccharides, as biological macromolecule-based scaffolding biomaterials in cornea tissue engineering: A review

Corneal-related diseases and injuries are the leading causes of vision loss, estimated to affect over 10 million people worldwide. Currently, cadaveric corneal grafts are considered the gold standard of treatment to restore cornea-related vision. However, this treatment modality faces different challenges such as donor shortage and graft failure. Therefore, the need for alternative solutions continues to grow. Tissue engineering has dramatically progressed to produce artificial cornea implants in order to repair, regenerate, or replace the damaged cornea. In this regard, a variety of polysaccharides such as cellulose, chitosan, alginate, agarose, and hyaluronic acid have been widely explored as scaffolding biomaterials for the production of tissue-engineered cornea. These polymers are known for their excellent biocompatibility, versatile properties, and processability. Recent progress and future perspectives of polysaccharide-based biomaterials in cornea tissue engineering is reviewed here.

Biomaterials-Based Regenerative Strategies for Skin Tissue Wound Healing

Skin tissue wound healing proceeds through four major stages, including hematoma formation, inflammation, and neo-tissue formation, and culminates with tissue remodeling. These four steps significantly overlap with each other and are aided by various factors such as cells, cytokines (both anti- and pro-inflammatory), and growth factors that aid in the neo-tissue formation. In all these stages, advanced biomaterials provide several functional advantages, such as removing wound exudates, providing cover, transporting oxygen to the wound site, and preventing infection from microbes. In addition, advanced biomaterials serve as vehicles to carry proteins/drug molecules/growth factors and/or antimicrobial agents to the target wound site. In this review, we report recent advancements in biomaterials-based regenerative strategies that augment the skin tissue wound healing process. In conjunction with other medical sciences, designing nanoengineered biomaterials is gaining significant attention for providing numerous functionalities to trigger wound repair. In this regard, we highlight the advent of nanomaterial-based constructs for wound healing, especially those that are being evaluated in clinical settings. Herein, we also emphasize the competence and versatility of the three-dimensional (3D) bioprinting technique for advanced wound management. Finally, we discuss the challenges and clinical perspective of various biomaterial-based wound dressings, along with prospective future directions. With regenerative strategies that utilize a cocktail of cell sources, antimicrobial agents, drugs, and/or growth factors, it is expected that significant patient-specific strategies will be developed in the near future, resulting in complete wound healing with no scar tissue formation.

Moringa (Moringa oleifera Lam.) polysaccharides: Extraction, characterization, bioactivities, and industrial application

Owing to numerous biological activities of different parts of Moringa oleifera Lam., various studies have been carried out to isolate and explore the activities of its various bioactive compounds including polysaccharides. Polysaccharides of M. oleifera have been reported to possess a variety of biofunctionalities including antihyperlipidemic, anti-diabetic, immunomodulatory, antihypertensive and gastrointestinal protection. In addition to bioactive polysaccharides, the gum exudated by stem of this plant is of commercial importance with wide range of applications in pharmaceutical industries. Various extraction and purification methods as well as combination of methods have been used to isolate and purify moringa polysaccharides. Studies suggest that extraction methods influence the structure of polysaccharides and thus their biological activity. This review summarizes all the available literature to provide updated information related to extraction, purification, modification, structural characterization, bioactivities and potential applications of moringa polysaccharides. This review will provide novel insights for future research and applications of moringa polysaccharides.

Preparation of Codonopsis pilosula polysaccharide microcapsules and its effect and mechanism on skin wound healing in rats

In this study, after optimizing the extraction process of CPP (Codonopsis pilosula polysaccharides), CPPM (CPP microcapsules) were prepared. Subsequently, the structural characteristics and physicochemical properties were studied. The results showed that CPPM is a hollow sac-like structure with rough folds and protuberances and comes in spherical or ellipsoidal shapes with uniform particle size. CPPM has certain swelling degree, low hardness, good adhesion, and stability. Then, the effect of CPPM on wounds repair was investigated by a rat model. The results showed that CPPM could improve the wound healing rate. Histological evaluation showed CPPM could promote neovascularization and fibroblast proliferation. By investigating the healing mechanism, it was found that CPPM increased the hydroxyproline content in granulation tissue and had an excellent antioxidant ability, and then inhibited lipid peroxidation, in addition, it significantly increased the transcript levels of VEGF and miRNA-21 genes, indicating that CPPM play an influential role in vascular remodeling during wound healing by up-regulating the expression of VEGF and miRNA-21 genes.

Characteristics of Sodium Alginate/Antarctic Krill Protein Composite Fiber Based on Cellulose Nanocrystals Modification: Rheology, Hydrogen Bond, Crystallization, Strength, and Water-Resistance

The purpose of adding cellulose nanocrystals (CNCs) into sodium alginate (SA) and Antarctic krill protein (AKP) system is to use the ionic cross-linking of SA and AKP and the dynamic hydrogen-bonding between them and CNCs to construct multiple cross-linking structures, to improve the water-resistance and strength of SA/AKP/CNCs composite fiber. Based on the structural viscosity index in rheological theory, the ratio of spinning solution and temperature were optimized by studying the structural viscosity index of the solution under different CNCs content and temperature, then the composite fiber was prepared by wet spinning. We found that when the content of CNCs is 0.8% and 1.2%, the temperature is 45 °C and 55 °C, the structural viscosity is relatively low. Under the optimal conditions, the intermolecular hydrogen bonds decrease with the increase of temperature. Some of the reduced hydrogen bonds convert into intramolecular hydrogen bonds. Some of them exist as free hydroxyl; increasing CNCs content increases intermolecular hydrogen bonds. With the increase of temperature, the crystallinity of composite fiber increases. The maximum crystallinity reaches 27%; the CNCs content increases from 0.8% to 1.2%, the breaking strength of composite fiber increases by 31%. The water resistance of composite fiber improves obviously, while the swelling rate is only 14%.

Application of Alginate Hydrogels for Next-Generation Articular Cartilage Regeneration

The articular cartilage has insufficient intrinsic healing abilities, and articular cartilage injuries often progress to osteoarthritis. Alginate-based scaffolds are attractive biomaterials for cartilage repair and regeneration, allowing for the delivery of cells and therapeutic drugs and gene sequences. In light of the heterogeneity of findings reporting the benefits of using alginate for cartilage regeneration, a better understanding of alginate-based systems is needed in order to improve the approaches aiming to enhance cartilage regeneration with this compound. This review provides an in-depth evaluation of the literature, focusing on the manipulation of alginate as a tool to support the processes involved in cartilage healing in order to demonstrate how such a material, used as a direct compound or combined with cell and gene therapy and with scaffold-guided gene transfer procedures, may assist cartilage regeneration in an optimal manner for future applications in patients.

Polysaccharides to combat viruses (Covid-19) and microbes: New updates

COVID-19, which is speedily distributed across the world and presents a significant challenge to public health, is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Following MERS coronavirus (MERS-CoV) and SARS, this is the third severe coronavirus outbreak in less than 20 years. To date, there are no exact agents and vaccines available for the treatment of COVID-19 that are clinically successful. Antimicrobial medications are effective in controlling infectious diseases. However, the extensive use of antibiotics makes microbes more resistant to drugs and demands novel bioactive agents' development. Polysaccharides are currently commonly used in the biomedical and pharmaceutical industries for their remarkable applications. Polysaccharides appear to have a wide range of anti-virus (anti-coronavirus) and antimicrobial applications. Polysaccharides are able to induce bacterial cell membrane disruption as they demonstrate potency in binding onto the surfaces of microbial cells. Here, the antiviral mechanisms of such polysaccharides and their success in the application of antiviral infections are reviewed. Additionally, this report provides a summary of current advancements of well-recognized polysaccharides as antimicrobial and anti-biofilm agents.

Waste Materials as a Resource for Production of CMC Superabsorbent Hydrogel for Sustainable Agriculture

Waste materials are receiving more attention as concerns about the future of our planet increase. Cellulose is the most common substance in agricultural waste. Agricultural wastes containing cellulose are misplaced resources that could be reused in various fields for both environmental and economic benefits. In this work, 32 different kinds of waste are investigated for chemical modification in order to obtain carboxymethyl cellulose for the production of a superabsorbent hydrogel that can be applied in agriculture. A brief literature review is provided to help researchers wishing to obtain carboxymethyl cellulose by carboxymethylation starting with waste materials. We also provide details about methods to obtain as well as verify carboxymethylation. Carboxymethyl cellulose (CMC), as a constituent of cellulosic water and superabsorbent hydrogels with applications in agriculture, is described. Superabsorbent hydrogels with CMC are able to absorb huge amounts of water and are biodegradable.

Production and Surface Modification of Cellulose Bioproducts

Petroleum-based synthetic plastics play an important role in our life. As the detrimental health and environmental effects of synthetic plastics continue to increase, the renewable, degradable and recyclable properties of cellulose make subsequent products the "preferred environmentally friendly" alternatives, with a small carbon footprint. Despite the fact that the bioplastic industry is growing rapidly with many innovative discoveries, cellulose-based bioproducts in their natural state face challenges in replacing synthetic plastics. These challenges include scalability issues, high cost of production, and most importantly, limited functionality of cellulosic materials. However, in order for cellulosic materials to be able to compete with synthetic plastics, they must possess properties adequate for the end use and meet performance expectations. In this regard, surface modification of pre-made cellulosic materials preserves the chemical profile of cellulose, its mechanical properties, and biodegradability, while diversifying its possible applications. The review covers numerous techniques for surface functionalization of materials prepared from cellulose such as plasma treatment, surface grafting (including RDRP methods), and chemical vapor and atomic layer deposition techniques. The review also highlights purposeful development of new cellulosic architectures and their utilization, with a specific focus on cellulosic hydrogels, aerogels, beads, membranes, and nanomaterials. The judicious choice of material architecture combined with a specific surface functionalization method will allow us to take full advantage of the polymer's biocompatibility and biodegradability and improve existing and target novel applications of cellulose, such as proteins and antibodies immobilization, enantiomers separation, and composites preparation.

Spin-coated freestanding films for biomedical applications

Spin-coating is a widely employed technique for the fabrication of thin-film coatings over large areas with smooth and homogeneous surfaces. In recent years, research has extended the scope of spin-coating by developing methods involving the interface of the substrate and the deposited solution to obtain self-supported films, also called freestanding films. Thereby, such structures have been developed for a wide range of areas. Biomedical applications of spin-coated freestanding films include wound dressings, drug delivery, and biosensing. This review will discuss the fundamental physical and chemical processes governing the conventional spin-coating as well as the techniques to obtain freestanding films. Furthermore, developments within this field with a primary focus on tissue engineering applications will be reviewed.

Alginate-Agarose Hydrogels Improve the In Vitro Differentiation of Human Dental Pulp Stem Cells in Chondrocytes. A Histological Study

Matrix-assisted autologous chondrocyte implantation (MACI) has shown promising results for cartilage repair, combining cultured chondrocytes and hydrogels, including alginate. The ability of chondrocytes for MACI is limited by different factors including donor site morbidity, dedifferentiation, limited lifespan or poor proliferation in vitro. Mesenchymal stem cells could represent an alternative for cartilage regeneration. In this study, we propose a MACI scaffold consisting of a mixed alginate-agarose hydrogel in combination with human dental pulp stem cells (hDPSCs), suitable for cartilage regeneration. Scaffolds were characterized according to their rheological properties, and their histomorphometric and molecular biology results. Agarose significantly improved the biomechanical behavior of the alginate scaffolds. Large scaffolds were manufactured, and a homogeneous distribution of cells was observed within them. Although primary chondrocytes showed a greater capacity for chondrogenic differentiation, hDPSCs cultured in the scaffolds formed large aggregates of cells, acquired a rounded morphology and expressed high amounts of type II collagen and aggrecan. Cells cultured in the scaffolds expressed not only chondral matrix-related genes, but also remodeling proteins and chondrocyte differentiation factors. The degree of differentiation of cells was proportional to the number and size of the cell aggregates that were formed in the hydrogels.

Applied Rheology as Tool for the Assessment of Chitosan Hydrogels for Regenerative Medicine

The regeneration of soft tissues that connect, support or surround other tissues is of great interest. In this sense, hydrogels have great potential as scaffolds for their regeneration. Among the different raw materials, chitosan stands out for being highly biocompatible, which, together with its biodegradability and structure, makes it a great alternative for the manufacture of hydrogels. Therefore, the aim of this work was to develop and characterize chitosan hydrogels. To this end, the most important parameters of their processing, i.e., agitation time, pH, gelation temperature and concentration of the biopolymer used were rheologically evaluated. The results show that the agitation time does not have a significant influence on hydrogels, whereas a change in pH (from 3.2 to 7) is a key factor for their formation. Furthermore, a low gelation temperature (4 °C) favors the formation of the hydrogel, showing better mechanical properties. Finally, there is a percentage of biopolymer saturation, from which the properties of the hydrogels are not further improved (1.5 wt.%). This work addresses the development of hydrogels with high thermal resistance, which allows their use as scaffolds without damaging their mechanical properties.

Hydrogels Based on Oxidized Cellulose Sulfates and Carboxymethyl Chitosan: Studies on Intrinsic Gel Properties, Stability, and Biocompatibility

Cellulose and chitosan are excellent components for the fabrication of bioactive scaffolds, as they are biocompatible and abundantly available. Their derivatives Ocarboxymethyl chitosan (CMChi) and oxidized cellulose sulfate (oxCS) can form in situ gelling, bioactive hydrogels, due to the formation of imine bonds for crosslinking. Here the influence of the degrees of sulfation (DS), oxidation (DO), and the molecular weight of oxCS on intrinsic and rheological properties of such hydrogels and their ability to support the survival and growth of human-adipose-derived stem cells (hADSC) is investigated. It is found that the pH of the hydrogels is generally slightly acidic, while their network density and E-modulus are found to be dependent on the DS and DO, which makes the properties of hydrogels tunable. Extensive studies show that hydrogels can be stable for up to 14 days and that their stability is largely dependent on the DO, molecular weight, and the components mixing ratio. Cytotoxicity studies of the hydrogel with hADSCs show biocompatible gels in dependence on the molecular weight and degree of oxidation with viable cells up to 14 days. These findings can help to develop specifically tailored hydrogels for tissue engineering applications to replace different types of connective tissue.

Gum Tragacanth (GT): A Versatile Biocompatible Material beyond Borders

The use of naturally occurring materials in biomedicine has been increasingly attracting the researchers’ interest and, in this regard, gum tragacanth (GT) is recently showing great promise as a therapeutic substance in tissue engineering and regenerative medicine. As a polysaccharide, GT can be easily extracted from the stems and branches of various species of Astragalus. This anionic polymer is known to be a biodegradable, non-allergenic, non-toxic, and non-carcinogenic material. The stability against microbial, heat and acid degradation has made GT an attractive material not only in industrial settings (e.g., food packaging) but also in biomedical approaches (e.g., drug delivery). Over time, GT has been shown to be a useful reagent in the formation and stabilization of metal nanoparticles in the context of green chemistry. With the advent of tissue engineering, GT has also been utilized for the fabrication of three-dimensional (3D) scaffolds applied for both hard and soft tissue healing strategies. However, more research is needed for defining GT applicability in the future of biomedical engineering. On this object, the present review aims to provide a state-of-the-art overview of GT in biomedicine and tries to open new horizons in the field based on its inherent characteristics.

Polysaccharide-Based Biomaterials in Tissue Engineering: A Review

In addition to proteins and nucleic acids, polysaccharides are an important type of biomacromolecule widely distributed in plants, animals, and microorganisms. Polysaccharides are considered as promising biomaterials due to their significant bioactivities, natural abundance, immunoactivity, and chemical modifiability for tissue engineering (TE) applications. Due to the similarities of the biochemical properties of polysaccharides and the extracellular matrix of human bodies, polysaccharides are increasingly recognized and accepted. Furthermore, the degradation behavior of these macromolecules is generally nontoxic. Certain delicate properties, such as remarkable mechanical properties and tunable tissue response, can be obtained by modifying the functional groups on the surface of polysaccharide molecules. The applications of polysaccharide-based biomaterials in the TE field have been growing intensively in recent decades, for example, bone/cartilage regeneration, cardiac regeneration, neural regeneration, and skin regeneration. This review summarizes the main essential properties of polysaccharides, including their chemical properties, crosslinking mechanisms, and biological properties, and focuses on the association between their structures and properties. The recent progress in polysaccharide-based biomaterials in various TE applications is reviewed, and the prospects for future studies are addressed as well. We intend this review to offer a comprehensive understanding of and inspiration for the research and development of polysaccharide-based materials in TE.

Dual-functional alginate crosslinker: Independent control of crosslinking density and cell adhesive properties of hydrogels via separate conjugation pathways

Alginate is an abundant natural polysaccharide widely utilized in various biomedical applications. Alginate also possesses numerous hydroxyl and carboxylate functional groups that allow chemical modifications to introduce different functionalities. However, it is difficult to apply various chemical reactions to alginate due to limited solubility in organic solvents. Herein, functional moieties for radical polymerization and cell adhesion were separately conjugated to hydroxyl and carboxylate groups of alginate, respectively, in order to independently control the crosslinking density and cell adhesive properties of hydrogels. Sodium counterions of alginate are first substituted with tetrabutylammonium ions to facilitate the dissolution in an organic solvent, followed by in situ conjugations of (1) cell adhesion molecules (CAM) via carbodiimide-mediated amide formation and (2) methacrylate via ring-opening nucleophilic reaction. The resulting CAM-linked methacrylic alginate was able to not only crosslink different monomers to form hydrogels with varying mechanical properties, but also induce stable cell adhesion to the hydrogels.

From a plant secretion to the promising bone grafts: Cryogels of silicon-integrated quince seed mucilage by microwave-assisted sol-gel reaction

Design and fabrication of biologically active cryogels using novel biopolymer(s) are still of great importance at regenerating bone defects such as traumatic bone injuries, maxillofacial surgery, osteomyelitis, and osteoporosis. Nowadays, plant mucilage, an herbal biomaterial, has been drawn attention by scientists due to their marvelous potential to fabricate 3-dimensional (3D) physical constructs for the field of regenerative medicine. Herein, a 3D cryogel from silicon-integrated quince seed mucilage (QSM) is constructed using microwave-assisted sol-gel reaction, characterized in-depth by attenuated total reflectance Fourier transform-infrared spectroscopy (ATR-FTIR), solid-state silicon cross-polarization magic-angle nuclear magnetic resonance (²⁹Si-CP-MAS NMR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), micro-mechanical testing, porosity, and swelling tests, contact angle measurements, Brunauer-Emmet-Teller and Barret-Joyner-Halenda (BET-BJH) analysis, enzymatic biodegradation test, and field emission-scanning electron microscopy-energy dispersive X-ray spectroscopy (FE-SEM-EDX) mapping. The osteobiologic capacity of the cryogels is determined using human adipose-derived mesenchymal stem cells (hAMSCs) under in vitro conditions. Osteogenic differentiation of hAMSCs on both QSM and silica-modified QSM (Si-QSM) cryogels is analyzed by histochemistry, immunohistochemistry, and quantitative-real time (q-RT) PCR techniques. The results obtained from in vitro experiments demonstrate that the upregulation of osteogenesis-related genes in Si-QSM cryogels presents a stronger and earlier development over QSM cryogels throughout the culture period, which in turn reveals the great potential of this novel Si-incorporated QSM cryogels for bone tissue engineering applications.

Antioxidant and anti-ageing effects of enzymatic polysaccharide from Pleurotus eryngii residue

The wide industrial cultivation of Pleurotus eryngii (P. eryngii) has resulted in the massive production of mushroom residues (MR) with low-efficiency utilization. In the present study, the P. eryngii enzymatic residue polysaccharide (PERP) was obtained from the P. eryngii residues. The characterization analysis showed that PERP was polysaccharides comprised of five kinds of monosaccharides with molecular weight of 2.05 × 10³ Da. PERP also showed rough surface and appeared as spherical structure dispersed in aqueous solution. The animal experiment analysis demonstrated that PERP exhibited potential anti-ageing effects on the brain, liver, kidney and skin, possibly by scavenging reactive radicals, improving the antioxidant status, supressing lipid peroxidation, enhancing organ functions and ameliorating histopathological damage. These results may provide a reference for the efficient utilization of P. eryngii residues in exploring MR-derived functional foods or drugs that delay the ageing process.

Subtle influence on alginate gel properties through host–guest interactions between covalently appended cyclodextrin and adamantane units

Host–guest interactions between functionalized alginate chains modulate the physico-chemical properties of alginate gels.

Characterization of complexes formed between debranched starch and fatty acids having different carbon chain lengths

Recently, amylose-lipid complexes have attracted widespread attention because of their various applications. However, DBS complexed with fatty acids of different carbon chain length are rarely studied. This study aimed to probe the complexation of DBS with saturated fatty acids having different carbon chain lengths (C6-C18). The results revealed that DBS was able to form V-type complexes with all the fatty acids considered. Compared to DBS, the relative crystallinity of the complexes increased 2-3 times. DBS with lauric acid and myristic acid formed three types V-type complexes (type I, type IIa, and type IIb). The complexing index followed the order of hexanoic acid > octanoic acid > capric acid > lauric acid > myristic acid > palmitic acid > stearic acid. Furthermore, lauric acid and myristic acid formed complexes with DBS more easily compared with other fatty acids.