Alginate and its application to tissue engineering

Insight into the digestion mechanism of proteins in silver carp (Hypophthalmichthys molitrix) surimi by different alginates

This study aimed to evaluate the impact of potassium alginate (PA), propylene glycol alginate (PGA), and calcium alginate (CA) on the gel properties of silver carp (Hypophthalmichthys molitrix) surimi (control group) throughout gastrointestinal digestion. The findings revealed that the protein digestibility of the PA/PGA and CA groups was found to be lower compared to the control group. Among these groups, the CA group had the lowest digestibility rate at 82.49 ± 3.50 %. The study revealed a reduction in the number of peptides found in the surimi group treated with alginate compared to the control group. Alginate was discovered to have inhibitory effects on proteolysis by forming a robust cross-linked network that obstructs pepsin from accessing its substrates. This research provides valuable insights into the potential application of alginate for improving the digestibility of surimi proteins and creating commercial surimi products.

State-of-the-Art Synthesis of Porous Polymer Materials and Their Several Fantastic Biomedical Applications: a Review

Porous polymers, including hydrogels, covalent organic frameworks (COFs), and hyper crosslinked polymers (HCPs), have become essential in biomedical research for their tunable pore architectures, large surface areas, and functional versatility. This review provides a comprehensive overview of their classification and updated synthesis mechanisms, such as 3D printing, electrospinning, and molecular imprinting. Their pivotal roles in drug delivery, tissue engineering, wound healing, and photodynamic/photothermal therapies, focusing on how pore size, distribution, and architecture impact drug release, cellular interactions, and therapeutic outcomes, are explored. Key challenges, including biocompatibility, mechanical strength, controlled degradation, and scalability, are critically assessed alongside emerging strategies to enhance clinical potential. Finally, recent challenges and future perspectives, emphasizing the broader biomedical applications of porous polymers, are addressed. This work provides valuable insights for advancing next-generation biomedical innovations through these materials.

From lab to life: advances inin-situbioprinting and bioink technology

Bioprinting has the potential to revolutionize tissue engineering and regenerative medicine, offering innovative solutions for complex medical challenges and addressing unmet clinical needs. However, traditionalin vitrobioprinting techniques face significant limitations, including difficulties in fabricating and implanting scaffolds with irregular shapes, as well as limited accessibility for rapid clinical application. To overcome these challenges,in-situbioprinting has emerged as a groundbreaking approach that enables the direct deposition of cells, biomaterials, and bioactive factors onto damaged organs or tissues, eliminating the need for pre-fabricated 3D constructs. This method promises a personalized, patient-specific approach to treatment, aligning well with the principles of precision medicine. The success ofin-situbioprinting largely depends on the advancement of bioinks, which are essential for maintaining cell viability and supporting tissue development. Recent innovations in hand-held bioprinting devices and robotic arms have further enhanced the flexibility ofin-situbioprinting, making it applicable to various tissue types, such as skin, hair, muscle, bone, cartilage, and composite tissues. This review examinesin-situbioprinting techniques, the development of smart, multifunctional bioinks, and their essential properties for promoting cell viability and tissue growth. It highlights the versatility and recent advancements inin-situbioprinting methods and their applications in regenerating a wide range of tissues and organs. Furthermore, it addresses the key challenges that must be overcome for broader clinical adoption and propose strategies to advance these technologies toward mainstream medical practice.

Processes of Obtaining Nanostructured Materialswith a Hierarchical Porous Structure on the Example of Alginate Aerogels

Currently, materials with specific, strictly defined functional properties are becoming increasingly important. A promising strategy for achieving these properties involves developing methods that facilitate the formation of hierarchical porous materials that combine micro-, meso-, and macropores in their structure. Macropores facilitate effective mass transfer of substances to the meso- and micropores, where further adsorption or reaction processes can occur. Aerogels represent a promising class of materials for implementing this approach. The formation of hierarchical porous structures in aerogels can be achieved using soft and hard templating methods or by foaming techniques. This paper presents a comprehensive study of three methods for forming hierarchical porous structures in alginate aerogels: (1) employing surfactants (Pluronic F-68), (2) using zein as a pore-forming component, and (3) foaming in a carbon dioxide medium. The results of micro-CT showed that each of the methods contributes to the formation of macropores within the structure of the resulting aerogels. Size distribution curves of the detected macropores were obtained, showing the presence of macropores ranging from 16 to 323 μm in size for samples obtained using surfactants, from 5 to 195 μm for samples obtained using zein, and from 20 μm to 3 mm for samples obtained by foaming in a carbon dioxide medium. The SEM images demonstrated the macro- and mesoporous fibrous structure of the obtained materials. The nitrogen porosimetry results indicated that samples obtained using surfactants and zein are characterized by a high specific surface area (592-673 m2/g), comparable to the specific surface area for an alginate-based aerogel obtained without the use of pore-forming components. However, the use of the developed methods for the formation of a hierarchical porous structure contributes to an increase in the specific mesopores volume (up to 17.7 cm3/g). The materials obtained by foaming in a carbon dioxide medium are characterized by lower specific surface areas (112-239 m2/g) and specific mesopores volumes (0.6-2.1 cm3/g). Thus, this paper presents a set of methods for forming hierarchical porous structures that can obtain delivery systems for active substances with a controlled release profile and highly efficient platforms for cell culturing.

In Situ Bioprinting: Process, Bioinks, and Applications

Traditional tissue engineering methods face challenges, such as fabrication, implantation of irregularly shaped scaffolds, and limited accessibility for immediate healthcare providers. In situ bioprinting, an alternate strategy, involves direct deposition of biomaterials, cells, and bioactive factors at the site, facilitating on-site fabrication of intricate tissue, which can offer a patient-specific personalized approach and align with the principles of precision medicine. It can be applied using a handled device and robotic arms to various tissues, including skin, bone, cartilage, muscle, and composite tissues. Bioinks, the critical components of bioprinting that support cell viability and tissue development, play a crucial role in the success of in situ bioprinting. This review discusses in situ bioprinting techniques, the materials used for bioinks, and their critical properties for successful applications. Finally, we discuss the challenges and future trends in accelerating in situ printing to translate this technology in a clinical settings for personalized regenerative medicine.

Alginate-based microencapsulation as a strategy to improve the therapeutic potential of cannabidiolic acid

Cannabidiolic Acid (CBDA) is a promising natural compound with potent antioxidant, anti-inflammatory, and anti-emetic properties. Its antioxidant activity rivals that of vitamin E, while its anti-inflammatory effects are also remarkable. Additionally, CBDA has been shown to effectively reduce nausea and emetic attacks. As a more natural and water-soluble alternative to CBD, CBDA offers improved bioavailability and absorption. However, despite its promising potential, the development of effective CBDA delivery systems is still in its early stages. Among the various materials suitable for drug delivery, alginate is a widely used biopolymer due to its abundance and common availability in nature. This study aimed to develop an efficient CBDA delivery carrier using a microflow-dripping method to microencapsulate CBDA into alginate carriers (Alg-CBDA). The antioxidant, antimicrobial, and cytotoxicity properties of these Alg-CBDA capsules were then evaluated. Our results demonstrated that encapsulating CBDA within alginate capsules yielded a novel multifunctional biomaterial with prolonged antioxidant activity up to 72 h and antimicrobial activity against Gram-positive bacteria. Furthermore, the encapsulation process significantly reduced CBDA's cytotoxicity, broadening its potential applications. To our knowledge, this is the first study demonstrating the advantages of CBDA within a drug delivery framework.

Electrospinning of methacrylated alginate for tissue engineering applications

Photo-crosslinkable methacrylated alginate derivatives (M-ALGs) were synthesized via modification of sodium alginate with glycidyl methacrylate. Needle (capillary) and needleless electrospinning techniques were employed to produce their nonwoven fiber mats. Spinning parameters such as applied voltage, solution composition, and flow rate were optimized to form uniform bead-free fibers with an average diameter of about 150 nm. The needleless technique allowed successful electrospinning of M-ALG solutions with wider ranges of viscosities and surface tensions owing to its higher applicable voltage (∼65 kV) compared to that of the needle technique (∼30 kV). Photo-crosslinking of the fibers via UV irradiation allowed the fiber mats to remain insoluble in physiological media while maintaining their mechanical properties. Cultivation of multipotent mesenchymal stem cells (MSCs) with the cross-linked fiber mats in a modified Eagle medium (α-MEM) showed the growth of spherical colonies, indicating the sufficient cytocompatibility of the fiber mats with MSCs.

Tunable Viscoelasticity of Alginate Hydrogels via Serial Autoclaving

Alginate hydrogels are widely used as biomaterials for cell culture and tissue engineering due to their biocompatibility and tunable mechanical properties. Reducing alginate molecular weight is an effective strategy for modulating hydrogel viscoelasticity and stress relaxation behavior, which can significantly impact cell spreading and fate. However, current methods like gamma irradiation to produce low molecular weight alginates suffer from high cost and limited accessibility. Here, a facile and cost-effective approach to reduce alginate molecular weight in a highly controlled manner using serial autoclaving is presented. Increasing the number of autoclave cycles results in proportional reductions in intrinsic viscosity, hydrodynamic radius, and molecular weight of the polymer while maintaining its chemical composition. Hydrogels fabricated from mixtures of the autoclaved alginates exhibit tunable mechanical properties, with inclusion of lower molecular weight alginate leading to softer gels with faster stress relaxation behaviors. The method is demonstrated by establishing how viscoelastic relaxation affects the spreading of encapsulated fibroblasts and glioblastoma cells. Results establish repetitive autoclaving as an easily accessible technique to generate alginates with a range of molecular weights and to control the viscoelastic properties of alginate hydrogels, and demonstrate utility across applications in mechanobiology, tissue engineering, and regenerative medicine.

Comparison of cation and anion-mediated resolution enhancement of bioprinted hydrogels for membranous tissue fabrication

Fabrication of engineered thin membranous tissues (TMTs) presents a significant challenge to researchers, as these structures are small in scale, but present complex anatomies containing multiple stratified cell layers. While numerous methodologies exist to fabricate such tissues, many are limited by poor mechanical properties, need for post-fabrication, or lack of cytocompatibility. Extrusion bioprinting can address these issues, but lacks the resolution necessary to generate biomimetic, microscale TMT structures. Therefore, our goal was to develop a strategy that enhances bioprinting resolution below its traditional limit of 150 μm and delivers a viable cell population. We have generated a system to effectively shrink printed gels via electrostatic interactions between anionic and cationic polymers. Base hydrogels are composed of gelatin methacrylate type A (cationic), or B (anionic) treated with anionic alginate, and cationic poly-L-lysine, respectively. Through a complex coacervation-like mechanism, the charges attract, causing compaction of the base GelMA network, leading to reduced sample dimensions. In this work, we evaluate the role of both base hydrogel and shrinking polymer charge on effective print resolution and cell viability. The alginate anion-mediated system demonstrated the ability to reach bioprinting resolutions of 70 μm, while maintaining a viable cell population. To our knowledge, this is the first study that has produced such significant enhancement in extrusion bioprinting capabilities, while also remaining cytocompatible.

Recent advances in polysaccharide-based drug delivery systems for cancer therapy: a comprehensive review

Cancer has a high rate of incidence and mortality throughout the world. Although several conventional approaches have been developed for the treatment of cancer, such as surgery, chemotherapy, radiotherapy and thermal therapy, they have remarkable disadvantages which result in inefficient treatment of cancer. For example, immunogenicity, prolonged treatment, non-specificity, metastasis and high cost of treatment, are considered as the major drawbacks of chemotherapy. Therefore, there is a fundamental requirement for the development of breakthrough technologies for cancer suppression. Polysaccharide-based drug delivery systems (DDSs) are the most reliable drug carriers for cancer therapy. Polysaccharides, as a kind of practical biomaterials, are divided into several types, including chitosan, alginates, dextran, hyaluronic acid, cyclodextrin, pectin, etc. Polysaccharides are extracted from different natural resources (like herbal, marine, microorganisms, etc.). The potential features of polysaccharides have made them reliable candidates for therapeutics delivery to cancer sites; the simple purification, ease of modification and functionalization, hydrophilicity, serum stability, appropriate drug loading capacity, biocompatibility, bioavailability, biodegradability and stimuli-responsive and sustained drug release manner are considerable aspects of these biopolymers. This review highlights the practical applications of polysaccharides-based DDSs in pharmaceutical science and cancer therapy.

Algal carbohydrates: Sources, biosynthetic pathway, production, and applications

Algae play a significant role in the global carbon cycle by utilizing photosynthesis to efficiently convert solar energy and atmospheric carbon dioxide into various chemical compounds, notably carbohydrates, pigments, lipids, and released oxygen, making them a unique sustainable cellular factory. Algae mostly consist of carbohydrates, which include a broad variety of structures that contribute to their distinct physical and chemical properties such as degree of polymerization, side chain, branching, degree of sulfation, hydrogen bond etc., these features play a crucial role in regulating many biological activity, nutritional and pharmaceutical properties. Algal carbohydrates have not received enough attention in spite of their distinctive structural traits linked to certain biological and physicochemical properties. Nevertheless, it is anticipated that there will be a significant increase in the near future due to increasing demand, sustainable source, biofuel generation and their bioactivity. This is facilitated by the abundance of easily accessible information on the structural data and distinctive characteristics of these biopolymers. This review delves into the different types of saccharides such as agar, alginate, fucoidan, carrageenan, ulvan, EPS and glucans synthesized by various macroalgal and microalgal systems, which include intracellular, extracellular and cell wall saccharides. Their structure, biosynthetic pathway, sources, production strategies and their applications in various field such as nutraceuticals, pharmaceuticals, biomedicine, food and feed, cosmetics, and bioenergy are also elaborately discussed. Algal polysaccharide has huge a scope for exploitation in future due to their application in food and pharmaceutical industry and it can become a huge source of capital and income.

Commercially available bioinks and state-of-the-art lab-made formulations for bone tissue engineering: A comprehensive review

Bioprinting and bioinks are two of the game changers in bone tissue engineering. This review presents different bioprinting technologies including extrusion-based, inkjet-based, laser-assisted, light-based, and hybrid technologies with their own strengths and weaknesses. This review will aid researchers in the selection and assessment of the bioink; the discussion ranges from commercially available bioinks to custom lab-made formulations mainly based on natural polymers, such as agarose, alginate, gelatin, collagen, and chitosan, designed for bone tissue engineering. The review is centered on technological advancements and increasing clinical demand within the rapidly growing bioprinting market. From this point of view, 4D, 5D, and 6D printing technologies promise a future where unprecedented levels of innovation will be involved in fabrication processes leading to more dynamic multifunctionalities of bioprinted constructs. Further advances in bioprinting technology, such as hybrid bioprinting methods are covered, with the promise to meet personalized medicine goals while advancing patient outcomes for bone tissues engineering applications.

Optimization of an Affordable and Efficient Skin Allograft Composite with Excellent Biomechanical and Biological Properties Suitable for the Regeneration of Deep Skin Wounds: A Preclinical Study

Deep skin wounds require grafting with a skin substitute for treatment. Despite many attempts in the development of an affordable and efficient skin substitute, the repair of deep skin wounds still remains challenging. In the current study, we present a 3D sponge composite made from human placenta (a disposable organ) and sodium alginate with exceptional properties for skin tissue engineering applications. Toward this goal, different proportions of alginate (Alg) and decellularized placenta scaffold (DPS) were composited and freeze-dried to generate a 3D sponge with the desired biomechanical and biological features. Comprehensive in vitro, in ovo, and in vivo characterizations were performed to assess the morphology, physical structure, mechanical behaviors, angiogenic potential, and wound healing properties of the composites. Through these analyses, the scaffold with optimal proportions of Alg (50%) and DPS (50%) was found to have superior properties. The optimized scaffold (Alg50/DPS50) was applied to the full-thickness wounds created in rats. Our data revealed that the addition of DPS to the Alg solution caused a significant improvement in the mechanical characteristics of the scaffold. Remarkably, the fabricated composite scaffold exhibited mechanical properties similar to those of native skin tissue. When implanted into the full-thickness wounds, the Alg50/DPS50 composite scaffold promoted angiogenesis, re-epithelialization, and granulation tissue formation, as compared to the group without a scaffold. Overall, our findings underscore the potential value of this hybrid scaffold for enhancing skin wound healing and suggest an Alg50/DPS50 composite for clinical investigations.

Ultrasound-Assisted Extraction of Alginate from Fucus vesiculosus Seaweed By-Product Post-Fucoidan Extraction

The solid phase byproduct obtained after conventional fucoidan extraction from the brown seaweed Fucus vesiculosus can be used as a source containing alginate. This study involves ultrasound-assisted extraction (UAE) of alginate from the byproduct using sodium bicarbonate. Response surface methodology (RSM) was applied to obtain the optimum conditions for alginate extraction. The ultrasound (US) treatments included 20 kHz of frequency, 20-91% of amplitude, and an extraction time of 6-34 min. The studied investigated the crude alginate yield (%), molecular weight, and alginate content (%) of the extracts. The optimum conditions for obtaining alginate with low molecular weight were found to be 69% US amplitude and sonication time of 30 min. The alginate extracts obtained were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Ultrasound-assisted extraction involving a short treatment lasting 6-34 min was found to be effective in extracting alginate from the byproduct compared to the conventional extraction of alginate using stirring at 415 rpm and 60 °C for 24 h. The US treatments did not adversely impact the alginate obtained, and the extracted alginates were found to have similar characteristics to the alginate obtained from conventional extraction and commercial sodium alginate.

Advances in 3D printing technology for preparing bone tissue engineering scaffolds from biodegradable materials

Introduction

Bone tissue engineering (BTE) provides an effective repair solution by implanting osteoblasts or stem cells into biocompatible and biodegradable scaffolds to promote bone regeneration. In recent years, the rapid development of 3D bioprinting has enabled its extensive application in fabricating BTE scaffolds. Based on three-dimensional computer models and specialized "bio-inks," this technology offers new pathways for customizing BTE scaffolds. This study reviews the current status and future prospects of scaffold materials for BTE in 3D bioprinting.

Methods

This literature review collected recent studies on BTE and 3D bioprinting, analyzing the advantages and limitations of various scaffold materials for 3D printing, including bioceramics, metals, natural polymers, and synthetic polymers. Key characteristics like biocompatibility, mechanical properties, and degradation rates of these materials were systematically compared.

Results

The study highlights the diverse performances of materials used in BTE scaffolds. Bioceramics exhibit excellent biocompatibility but suffer from brittleness; metals offer high strength but may induce chronic inflammation; natural polymers are biocompatible yet have poor mechanical properties, while synthetic polymers offer strong tunability but may produce acidic by-products during degradation. Additionally, integrating 3D bioprinting with composite materials could enhance scaffold biocompatibility and mechanical properties, presenting viable solutions to current challenges.

Discussion

This review summarizes recent advances in 3D bioprinting for BTE scaffold applications, exploring the strengths and limitations of various materials and proposing composite material combinations to improve scaffold performance. By optimizing material selection and combinations, 3D bioprinting shows promise for creating customized scaffolds, offering a new technical route for clinical applications of BTE. This research provides a unique perspective and theoretical support for advancing 3D bioprinting technology in bone regeneration, outlining future directions for BTE materials and 3D bioprinting technology development.

Cysteine Conjugation: An Approach to Obtain Polymers with Enhanced Muco- and Tissue Adhesion

The modification of polymers towards increasing their biocompatibility gathers the attention of scientists worldwide. Several strategies are used in this field, among which chemical post-polymerization modification has recently been the most explored. Particular attention revolves around polymer-L-cysteine (Cys) conjugates. Cys, a natural amino acid, contains reactive thiol, amine, and carboxyl moieties, allowing hydrogen bond formation and improved tissue adhesion when conjugated to polymers. Conjugation of Cys and its derivatives to polymers has been examined mostly for hyaluronic acid, chitosan, alginate, polyesters, polyurethanes, poly(ethylene glycol), poly(acrylic acid), polycarbophil, and carboxymethyl cellulose. It was shown that the conjugation of Cys and its derivatives to polymers significantly increased their tissue adhesion, particularly mucoadhesion, stability at physiological pH, drug encapsulation efficiency, drug release, and drug permeation. Conjugates were also non-toxic toward various cell lines. These properties make Cys conjugation a promising strategy for advancing polymer applications in drug delivery systems and tissue engineering. This review aims to provide an overview of these features and to present the conjugation of Cys and its derivatives as a modern and promising approach for enhancing polymer tissue adhesion and its application in the medical field.

Alginate Formulation for Wound Healing Applications

Significance: Alginate, sourced from seaweed, holds significant importance in industrial and biomedical domains due to its versatile properties. Its chemical composition, primarily comprising β-D-mannuronic acid and α-L-guluronic acid, governs its physical and biological attributes. This polysaccharide, extracted from brown algae and bacteria, offers diverse compositions impacting key factors such as molecular weight, flexibility, solubility, and stability. Recent Advances: Commercial extraction methods yield soluble sodium alginate essential for various biomedical applications. Extraction processes involve chemical treatments converting insoluble alginic acid salts into soluble forms. While biosynthesis pathways in bacteria and algae share similarities, differences in enzyme utilization and product characteristics are noted. Critical Issues: Despite its widespread applicability, challenges persist regarding alginate's stability, biodegradability, and bioactivity. Further understanding of its interactions in complex biological environments and the optimization of extraction and synthesis processes are imperative. Additionally, concerns regarding immune responses to alginate-based implants necessitate thorough investigation. Future Directions: Future research endeavors aim to enhance alginate's stability and bioactivity, facilitating its broader utilization in regenerative medicine and therapeutic interventions. Novel approaches focusing on tailored hydrogel formations, advanced drug delivery systems, and optimized cellular encapsulation techniques hold promise. Continued exploration of alginate's potential in tissue engineering and wound healing, alongside efforts to address critical issues, will drive advancements in biomedical applications.

Synthesis of agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads: Characterization and application as controlled-release microencapsulated fertilizers

Synthesis of novel agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads, micromeritic/morphometric characteristics of the prepared formulations, greenhouse trials using controlled-release microencapsulated fertilizers, and acute fish toxicity testing were conducted simultaneously for the first time within the scope of an integrated research. In the present analysis, for the first time, 16 different morphometric features, and 32 disinct plant growth traits of the prepared composite beads were explored in detail within the framework of a comprehensive digital image analysis. The hydrogel beads composed of 19 different agro-industrial wastes/materials were successfully synthesized using the ionotropic external gelation technique and CaCl2 as cross-linker. According to micromeritic characteristics, the ionotropically cross-linked beads exhibited 77.86 ± 3.55 % yield percentage and 2.679 ± 0.397 mm average particle size. The dried microbeads showed a good swelling ratio (270.02 ± 80.53 %) and had acceptable flow properties according to Hausner's ratio (1.136 ± 0.028), Carr's index (11.94 ± 2.17 %), and angle of repose (25.03° ± 5.33°) values. The settling process of the prepared microbeads was observed in the intermediate flow regime, as indicated by the average particle Reynolds numbers (169.17 ± 82.81). Experimental findings and non-parametric statistical tests reveal that dried fertilizer matrices demonstrated noteworthy performance on the cultivation of red hot chili pepper plant (Capsicum annuum var. fasciculatum) according to the results of greenhouse trials. Surface morphologies of the best-performing fertilizer matrices were also characterized by Scanning Electron Microscopy. Moreover, the static fish bioassay experiment confirmed that no abnormalities and acute toxic reactions occurred in shortfin molly fish (Poecilia sphenops) fed with dried leaves of red hot chili pepper plants grown with formulated fertilizers. This study showcased a pioneering investigation into the synthesis of microcapsules using synthesized hydrogel beads along with digital image processing for bio-waste management and sustainable agro-application.

Sustained BMP-2 delivery via alginate microbeads and polydopamine-coated 3D-Printed PCL/β-TCP scaffold enhances bone regeneration in long bone segmental defects

Background/Objective

Repair of long bone defects remains a major challenge in clinical practice, necessitating the use of bone grafts, growth factors, and mechanical stability. Hence, a combination therapy involving a 3D-printed polycaprolactone (PCL)/β-tricalcium phosphate (β-TCP) scaffold coated with polydopamine (PDA) and alginate microbeads (AM) for sustained delivery of bone morphogenetic protein-2 (BMP-2) was investigated to treat long bone segmental defects.

Methods

Several in vitro analyses were performed to evaluate the scaffold osteogenic effects in vitro such as PDA surface modification, namely, hydrophilicity and cell adhesion; cytotoxicity and BMP-2 release kinetics using CCK-8 assay and ELISA, respectively; osteogenic differentiation in canine adipose-derived mesenchymal stem cells (Ad-MSCs); formation of mineralized nodules using ALP staining and ARS staining; and mRNA expression of osteogenic differentiation markers using RT-qPCR. Bone regeneration in femoral bone defects was evaluated in vivo using a rabbit femoral segmental bone defect model by performing radiography, micro-computed tomography, and histological observation (hematoxylin and eosin and Masson's trichrome staining).

Results

The PDA-coated 3D-printed scaffold demonstrated increased hydrophilicity, cell adhesion, and cell proliferation compared with that of the control. BMP-2 release kinetics assessment showed that BMP-2 AM showed a reduced initial burst and continuous release for 28 days. In vitro co-culture with canine Ad-MSCs showed an increase in mineralization and mRNA expression of osteogenic markers in the BMP-2 AM group compared with that of the BMP-2-adsorbed scaffold group. In vivo bone regeneration evaluation 12 weeks after surgery showed that the BMP-2 AM/PDA group exhibited the highest bone volume in the scaffold, followed by the BMP-2/PDA group. High cortical bone connectivity was observed in the PDA-coated scaffold groups.

Conclusion

These findings suggest that the combined use of PDA-coated 3D-printed bone scaffolds and BMP-2 AM can successfully induce bone regeneration even in load-bearing bone segmental defects.

The translational potential of this article

A 3D-printed PCL/β-TCP scaffold was fabricated to mimic the cortical bone of the femur. Along with the application of PDA surface modification and sustained BMP-2 release via AM, the developed scaffold could provide suitable osteoconduction, osteoinduction, and osteogenesis in both in vitro settings and in vivo rabbit femoral segmental bone defect models. Therefore, our findings suggest a promising therapeutic option for treating challenging long bone segmental defects, with potential for future clinical application.

Alginate-based hydrogels mediated biomedical applications: A review

With the development in the field of biomaterials, research on alternative biocompatible materials has been initiated, and alginate in polysaccharides has become one of the research hotspots due to its advantages of biocompatibility, biodegradability and low cost. In recent years, with the further understanding of microscopic molecular structure and properties of alginate, various physicochemical methods of cross-linking strategies, as well as organic and inorganic materials, have led to the development of different properties of alginate hydrogels for greatly expanded applications. In view of the potential application prospects of alginate-based hydrogels, this paper reviews the properties and preparation of alginate-based hydrogels and their major achievements in delivery carrier, dressings, tissue engineering and other applications are also summarized. In addition, the combination of alginate-based hydrogel and new technology such as 3D printing are also involved, which will contribute to further research and exploration.

Quantitative Macromolecular Modeling Assay of Biopolymer-Based Hydrogels

The rubber elasticity theory has been lengthily applied to several polymeric hydrogel substances and upgraded from idealistic models to consider imperfections in the polymer network. The theory relies solely on hyperelastic material models in order to provide a description of the elastic polymer network. While this is also applicable to polymer gels, such hydrogels are rather characterized by their water content and visco-elastic mechanical properties. In this work, we applied rubber elasticity constitutive models through hyperelastic parameter identification of hydrogels based on their stress-strain response to compression. We further performed swelling experiments and determined the intrinsic properties, i.e., density, of the specimens and their components. Additionally, we estimated their equilibrium swelling and employed it in the swelling-equilibrium theory in order to determine the polymer-solvent interaction parameter of each hydrogel with regard to cross-linking. Our results show that the average mesh size obtained from the rubber elasticity theory can be regarded as a concentration-dependent characteristic length of the hydrogel's network and couples the non-linear elastic response to the specimens' inherent visco-elasticity through hysteresis as a quantifier of energy dissipation under large deformation.

Seaweed-derived laminarin and alginate as potential chemotherapeutical agents: An updated comprehensive review considering cancer treatment

Seaweed-derived bioactive substances such as polysaccharides have proven to be effective chemotherapeutic and chemopreventive agents. Laminarin and alginate antioxidant properties aid in the prevention of cancer through dynamic modulation of critical intracellular signaling pathways via apoptosis which produce low cytotoxicity and potential chemotherapeutic effects. Understanding the effects of laminarin and alginate on human cancer cells and their molecular roles in cell death pathways can help to develop a novel chemoprevention strategy. This review emphasizes the importance of apoptosis-modulating laminarin and alginate in a range of malignancies as well as their extraction, molecular structure, and weight. In addition, future nano-formulation enhancements for greater clinical efficacy are discussed. Laminarin and alginate are perfect ingredients because of their distinct physicochemical and biological characteristics and their use-based delivery systems in cancer. The effectiveness of laminarin and alginate against cancer and more preclinical and clinical trials will open up as new chemotherapeutic natural drugs which lead to established as potential cancer drugs.

Exosome-Laden Hydrogels as Promising Carriers for Oral and Bone Tissue Engineering: Insight into Cell-Free Drug Delivery

Mineralization is a key biological process that is required for the development and repair of tissues such as teeth, bone and cartilage. Exosomes (Exo) are a subset of extracellular vesicles (~50-150 nm) that are secreted by cells and contain genetic material, proteins, lipids, nucleic acids, and other biological substances that have been extensively researched for bone and oral tissue regeneration. However, Exo-free biomaterials or exosome treatments exhibit poor bioavailability and lack controlled release mechanisms at the target site during tissue regeneration. By encapsulating the Exos into biomaterials like hydrogels, these disadvantages can be mitigated. Several tissue engineering approaches, such as those for wound healing processes in diabetes mellitus, treatment of osteoarthritis (OA) and cartilage degeneration, repair of intervertebral disc degeneration, and cardiovascular diseases, etc., have been exploited to deliver exosomes containing a variety of therapeutic and diagnostic cargos to target tissues. Despite the significant efficacy of Exo-laden hydrogels, their use in mineralized tissues, such as oral and bone tissue, is very sparse. This review aims to explore and summarize the literature related to the therapeutic potential of hydrogel-encapsulated exosomes for bone and oral tissue engineering and provides insight and practical procedures for the development of future clinical techniques.

Biological Scaffolds in 3D Cell Models: Driving Innovation in Drug Discovery

The discipline of 3D cell modeling is currently undergoing a surge of captivating developments that are enhancing the realism and utility of tissue simulations. Using bioinks which represent cells, scaffolds, and growth factors scientists can construct intricate tissue architectures layer by layer using innovations like 3D bioprinting. Drug testing can be accelerated and organ functions more precisely replicated owing to the precise control that microfluidic technologies and organ-on-chip devices offer over the cellular environment. Tissue engineering is becoming more dynamic with materials that can modify their surroundings with the advent of hydrogels and smart biomaterials. Advances in spheroids and organoids are not only bringing us towards more effective and customized therapies, but they are also improving their ability to resemble actual human tissues. Confocal and two-photon microscopy are examples of advanced imaging methods that provide precise images of the functioning and interaction of cells. Artificial Intelligence models have applications for enhanced scaffold designs and for predicting the response of tissues to medications. Furthermore, via strengthening predictive models, optimizing data analysis, and simplifying 3D cell culture design, artificial intelligence is revolutionizing this field. When combined, these technologies are improving our ability to conduct research and moving us toward more individualized and effective medical interventions.

Borate bioactive glass enhances 3D bioprinting precision and biocompatibility on a sodium alginate platform via Ca2+ controlled self-solidification

Sodium alginate (SA) has gained widespread acclaim as a carrier medium for three-dimensional (3D) bioprinting of cells and a diverse array of bioactive substances, attributed to its remarkable biocompatibility and affordability. The conventional approach for fabricating alginate-based tissue engineering constructs entails a post-treatment phase employing a calcium ion solution. However, this method proves ineffectual in addressing the predicament of low precision during the 3D printing procedure and is unable to prevent issues such as non-uniform alginate gelation and substantial distortions. In this study, we introduced borate bioactive glass (BBG) into the SA matrix, capitalizing on the calcium ions released from the degradation of BBG to incite the cross-linking reaction within SA, resulting in the formation of BBG-SA hydrogels. Building upon this fundamental concept, it unveiled that BBG-SA hydrogels greatly enhance the precision of SA in extrusion-based 3D printing and significantly reduce volumetric contraction shrinkage post-printing, while also displaying certain adhesive properties and electrical conductivity. Furthermore, in vitro cellular experiments have unequivocally established the excellent biocompatibility of BBG-SA hydrogel and its capacity to actively stimulate osteogenic differentiation. Consequently, BBG-SA hydrogel emerges as a promising platform for 3D bioprinting, laying the foundation for the development of flexible, biocompatible electronic devices.

Bioactive polymers: A comprehensive review on bone grafting biomaterials

The application of bone grafting materials in bone tissue engineering is paramount for treating severe bone defects. In this comprehensive review, we explore the significance and novelty of utilizing bioactive polymers as grafts for successful bone repair. Unlike metals and ceramics, polymers offer inherent biodegradability and biocompatibility, mimicking the native extracellular matrix of bone. While these polymeric micro-nano materials may face challenges such as mechanical strength, various fabrication techniques are available to overcome these shortcomings. Our study not only investigates diverse biopolymeric materials but also illuminates innovative fabrication methods, highlighting their importance in advancing bone tissue engineering.

Biomedical potentials of alginate via physical, chemical, and biological modifications

Alginate is a linear polysaccharide with a modifiable structure and abundant functional groups, offers immense potential for tailoring diverse alginate-based materials to meet the demands of biomedical applications. Given the advancements in modification techniques, it is significant to analyze and summarize the modification of alginate by physical, chemical and biological methods. These approaches provide plentiful information on the preparation, characterization and application of alginate-based materials. Physical modification generally involves blending and physical crosslinking, while chemical modification relies on chemical reactions, mainly including acylation, sulfation, phosphorylation, carbodiimide coupling, nucleophilic substitution, graft copolymerization, terminal modification, and degradation. Chemical modified alginate contains chemically crosslinked alginate, grafted alginate and oligo-alginate. Biological modification associated with various enzymes to realize the hydrolysis or grafting. These diverse modifications hold great promise in fully harnessing the potential of alginate for its burgeoning biomedical applications in the future. In summary, this review provides a comprehensive discussion and summary of different modification methods applied to improve the properties of alginate while expanding its biomedical potentials.

Phycocyanin-Loaded Alginate-Based Hydrogel Synthesis and Characterization

Phycocyanin was extracted from Spirulina platensis using conventional extraction (CE), direct ultrasonic-assisted extraction (direct UAE), indirect ultrasonic-assisted extraction (indirect UAE), and microwave-assisted extraction (MAE) methods at different temperatures, extraction intervals, stirring rate, and power intensities while maintaining the same algae to solvent ratio (1:15 w/v). The optimization of the extraction parameters indicated that the direct UAE yielded the highest phycocyanin concentration (29.31 ± 0.33 mg/mL) and antioxidant activity (23.6 ± 0.56 mg TE/g algae), while MAE achieved the highest purity (Rp = 0.5 ± 0.002). Based on the RP value, phycocyanin extract obtained by MAE (1:15 w/v algae to solvent ratio, 40 min, 40 °C, and 900 rpm) was selected as active compound in an alginate-based hydrogel formulation designed as potential wound dressings. Phycocyanin extracts and loaded hydrogels were characterized by FT-IR analysis. SEM analysis confirmed a porous structure for both blank and phycocyanin loaded hydrogels, while the mechanical properties remained approximately unchanged in the presence of phycocyanin. Phycocyanin release kinetics was investigated at two pH values using Zero-order, First-order, Higuchi, and Korsmeyer-Peppas kinetics models. The Higuchi model best fitted the experimental results. The R2 value at higher pH was nearly 1, indicating a superior fit compared with lower pH values.

Nanomaterial-functionalized electrospun scaffolds for tissue engineering

Tissue engineering has emerged as a biological alternative aimed at sustaining, rehabilitating, or enhancing the functionality of tissues that have experienced partial or complete loss of their operational capabilities. The distinctive characteristics of electrospun nanofibrous structures, such as their elevated surface-area-to-volume ratio, specific pore sizes, and fine fiber diameters, make them suitable as effective scaffolds in tissue engineering, capable of mimicking the functions of the targeted tissue. However, electrospun nanofibers, whether derived from natural or synthetic polymers or their combinations, often fall short of replicating the multifunctional attributes of the extracellular matrix (ECM). To address this, nanomaterials (NMs) are integrated into the electrospun polymeric matrix through various functionalization techniques to enhance their multifunctional properties. Incorporation of NMs into electrospun nanofibrous scaffolds imparts unique features, including a high surface area, superior mechanical properties, compositional variety, structural adaptability, exceptional porosity, and enhanced capabilities for promoting cell migration and proliferation. This review provides a comprehensive overview of the various types of NMs, the methodologies used for their integration into electrospun nanofibrous scaffolds, and the recent advancements in NM-functionalized electrospun nanofibrous scaffolds aimed at regenerating bone, cardiac, cartilage, nerve, and vascular tissues. Moreover, the main challenges, limitations, and prospects in electrospun nanofibrous scaffolds are elaborated.

Enhanced anti-tumor and anti-metastatic activity of quercetin using pH-sensitive Alginate@ZIF-8 nanocomposites:in vitroandin vivostudy

Quercetin (Qc) possesses anti-cancer properties, such as cell signaling, growth suppression, pro-apoptotic, anti-proliferative, and antioxidant effects. In this study, we developed an alginate-modified ZIF-8 (Alg@ZIF-8) to enhance the anti-tumor efficacy of Qc. The developed alginate-modified quercetin-loaded ZIF-8 (Alg@Qc@ZIF-8) was characterized using scanning electron microscope (SEM), dynamic light scattering (DLS), fourier transform infrared spectroscopy Thermogravimetric analysis, Brunauer-Emmett-Teller, and x-ray diffraction. The drug release pattern was evaluated at pH 5.4 and 7.4. The cytotoxicity of nanoparticles was assessed on the 4T1 cell line. Finally, the anti-tumor activity of Alg@Qc@ZIF-8 was evaluated in 4T1 tumor-bearing mice. SEM showed that the nanoparticles were spherical with a diameter of mainly below 50 nm. The DLS showed that the developed nanoparticles' hydrodynamic diameter, zeta potential, and polydispersity index were 154.9 ± 7.25 nm, -23.8 ± 5.33 mV, and 0.381 ± 0.09, respectively. The drug loading capacity was 10.40 ± 0.02%. Alg@Qc@ZIF-8 exhibited pH sensitivity, releasing more Qc at pH 5.4 (about 3.62 times) than at pH 7.4 after 24 h. Furthermore, the IC50value of Alg@Qc@ZIF-8 on the 4T1 cell line was 2.16 times lower than net Qc. Importantly, in tumor-bearing mice, Alg@Qc@ZIF-8 demonstrated enhanced inhibitory effects on tumor growth and lung metastasis compared to net Qc. Considering thein vitroandin vivooutcomes, Alg@Qc@ZIF-8 might hold great potential for effective breast cancer management.

The impact of copper nanoparticles surfactant on the structural and biological properties of chitosan/sodium alginate wound dressings

Multifunctional wound dressings based on hydrogels are an efficacious and practicable strategy in therapeutic processes and accelerated chronic wound healing. Here, copper (Cu) nanoparticles were added to chitosan/sodium alginate (CS/SA) hydrogels to improve the antibacterial properties of the prepared wound dressings. Due to the super-hydrophobicity of Cu nanoparticles, polyethylene glycol (PEG) was used as a surfactant, and then added to the CS/SA-based hydrogels. The CS/SA/Cu hydrogels were synthesized with 0, 2, 3.5, and 5 wt% Cu nanoparticles. The structural and morphological properties in presence of PEG were evaluated using Fourier-transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). The biodegradation and swelling properties of the hydrogels were investigated in phosphate buffer saline (PBS) at 37 °C for up to 30 days. Cell viability and adhesion, as well as antibacterial behavior, were investigated via MTT assay, FESEM, and disk diffusion method, respectively. The obtained results showed that PEG provided new intra- and intermolecular bonds that affected significantly the hydrogels' degradation and swelling ratio, which increased up to ~1200 %. Cell viability reached ~110 % and all samples showed remarkable antibacterial behavior when CS/SA/Cu containing 2 wt% was introduced. This study provided new insights regarding the use of PEG as a surfactant for Cu nanoparticles in CS/SA hydrogel wound dressing, ultimately affecting the chemical bonding and various properties of the prepared hydrogels.

Unveiling the potential of alginate-based nanomaterials in sensing technology and smart delivery applications

Sensors are applied to many fields nowadays because of their high sensitivity, low cost, time-saving, user-friendly, and excellent selectivity. Current biomedical and pharmaceutical science has one focus on developing nanoparticle-based sensors, especially biopolymeric nanoparticles. Alginate is a widely used biopolymer in a variety of applications. The hydrogel-forming characteristic, the chemical structure with hydroxy and carboxylate moieties, biocompatibility, biodegradability, and water solubility of alginate have expanded opportunities in material and biomedical sciences. Recently, research on alginate-based nanoparticles and their applications has begun. These materials are gaining popularity because of their wide usage potential in the biomedical and pharmaceutical fields. Many review papers describe applications of alginate in the drug delivery field. The current study covers the structural and physicochemical properties of alginate-based nanoparticles. The prospective applications of alginate-based nanomaterials in various domains are discussed, including drug delivery and environmental sensing applications for humidity, heavy metals, and hydrogen peroxide. Moreover, biomedical sensing applications of alginate-based nanoparticles regarding various analytes such as glucose, cancer cells, pharmaceutical drugs, and human motion will also be reviewed in this paper. Future research scopes highlight existing challenges and solutions.

Physicochemical and Biological Characterization of Gelatin/Alginate Scaffolds Reinforced with β-TCP, FDBA, and SrHA: Insights into Stem Cell Behavior and Osteogenic Differentiation

Bone tissue engineering necessitates the development of scaffolds with optimal properties to provide a suitable microenvironment for cell adhesion, proliferation, and osteogenic differentiation. The selection of appropriate scaffold materials remains a critical challenge in this field. In this study, we aimed to address this challenge by evaluating and comparing the performance of hydrogel scaffolds reinforced with β-tricalcium phosphate (β-TCP), allograft, and a combination of allograft and strontium hydroxyapatite (SrHA). In this study, scaffolds containing the following compounds with a weight ratio of 75 : 25 : 50 were made using a 3D printer: group (1) alginate + gelatin + β-TCP (TCP), group (2) alginate + gelatin + allograft (Allo), and group (3) alginate + gelatin + allograft + strontium hydroxyapatite (Str). Stem cells extracted from rat bone marrow (rBMSCs) were cultured on scaffolds, and cell proliferation and differentiation tests were performed. Also, the physical and chemical properties of the scaffolds were investigated. The two/one-way analysis of variance (ANOVA) by Tukey's post hoc test was performed. There was no significant difference between scaffolds with pore size and porosity. TCP scaffolds' mechanical strength and degradation rate were significantly lower than the other two groups (P < 0.05). Also, the swelling ratio of Allo scaffolds was higher than in other samples. The amount of cell proliferation in the samples of the TCP group was lower than the other two, and the Allo samples had the best results in this concern (P < 0.01). However, the scaffolds containing strontium hydroxyapatite had significantly higher bone differentiation compared to the other two groups, and the lowest results were related to the scaffolds containing β-TCP. Hydrogel scaffolds reinforced with allograft or its combination with strontium showed better physicochemical and biological behavior compared to those reinforced with β-TCP. Besides, adding strontium had a limited impact on the physicochemical features of allograft-containing scaffolds while improving their potential to induce osteogenic differentiation.

Fibronectin Functionalization: A Way to Enhance Dynamic Cell Culture on Alginate/Hydroxyapatite Scaffolds

Bone defects are a global health concern; bone tissue engineering (BTE) is the most promising alternative to reduce patient morbidity and overcome the inherent drawbacks of autograft and allograft bone. Three-dimensional scaffolds are pivotal in this field due to their potential to provide structural support and mimic the natural bone microenvironment. Following an already published protocol, a 3D porous structure consisting of alginate and hydroxyapatite was prepared after a gelation step and a freezing-drying step. Despite the frequent use of alginate in tissue regeneration, the biological inertness of this polysaccharide hampers proper cell colonization and proliferation. Therefore, the purpose of this work was to enhance the biological properties by promoting the interaction and adhesion between cells and biomaterial with the use of Fibronectin. This extracellular matrix protein was physically adsorbed on the scaffold, and its presence was evaluated with environmental scanning electron microscopy (eSEM) and the Micro-Bicinchoninic Acid (μBCA) protein assay. The MG-63 cell line was used for both static and dynamic (i.e., in bioreactor) 3D cell culturing on the scaffolds. The use of the bioreactor allowed for a better exchange of nutrients and oxygen and a better removal of cell catabolites from the inner portion of the construct, mimicking the physiological environment. The functionalized scaffolds showed an improvement in cell proliferation and colonization compared to non-functionalized ones; the effect of the addition of Fibronectin was more evident in the dynamic culturing conditions, where the cells clearly adhered on the surface of functionalized scaffolds.

Alginate based hemostatic materials for bleeding management: A review

Severe bleeding has caused significant financial losses as well as a major risk to the lives and health of military and civilian populations. Under some situations, the natural coagulation mechanism of the body is unable to achieve fast hemostasis without the use of hemostatic drugs. Thus, the development of hemostatic materials and techniques is essential. Improving the quality of life and survival rate of patients and minimizing bodily damage requires fast, efficient hemostasis and prevention of bleeding. Alginate is regarded as an outstanding hemostatic polymer because of its non-immunogenicity, biodegradability, good biocompatibility, simple gelation, non-toxicity, and easy availability. This review summarizes the basics of hemostasis and emphasizes the recent developments regarding alginate-based hemostatic systems. Structural modifications and mixing with other materials have widely been used for the improvement of hemostatic characteristics of alginate and for making multifunctional medical devices that not only prevent uncontrolled bleeding but also have antibacterial characteristics, drug delivery abilities, and curing effects. This review is hoped to prepare critical insights into alginate modifications for better hemostatic properties.

Motion-Accommodating Dual-Layer Hydrogel Dressing to Deliver Adipose-Derived Stem Cells to Wounds

BACKGROUND

Current dressing materials cannot secure a cell survival-promoting wound environment for stem cell delivery due to insufficient assimilation to skin motion. The authors developed a novel motion-accommodating dual-layer hydrogel dressing for stem cell delivery into such wounds.

METHODS

Dorsal hand skin movement was evaluated to determine the potential range of deformation for a dressing. The outer hydrogel (OH) was fabricated with an alginate-acrylamide double-network hydrogel with a covalently cross-linked elastomer coat. The tough adhesive consisted of a chitosan-based bridging polymer and coupling reagents. OH material properties and adhesiveness on porcine skin were measured. An oxidized alginate-based inner hydrogel (IH) containing human adipose-derived stem cells (ASCs) was evaluated for cell-supporting and cell-releasing properties. The OH's function as a secondary dressing, and dual-layer hydrogel cell delivery potential in wounds were assessed in a rodent model.

RESULTS

The dual-layer hydrogel consisted of OH and IH. The OH target range of deformation was up to 25% strain. The OH adhered to porcine skin, and showed significantly higher adhesion energy than common secondary dressings and endured 900 flexion-extension cycles without detachment. OH showed a similar moisture vapor transmission rate as moisture-retentive dressings. IH maintained embedded cell survival for three days with significant cell release on the contacting surface. OH showed less fibrotic wound healing than other secondary dressings in vivo. The dual-layer hydrogel successfully delivered ASCs into open wounds of nude mice (13 ± 3 cells/HPF).

CONCLUSIONS

The novel dual-layer hydrogel can accommodate patient movement and deliver ASCs into the wound bed by securing the wound microenvironment.

Chitosan composite with mesenchymal stem cells: Properties, mechanism, and its application in bone regeneration

Bone defects resulting from trauma, illness or congenital abnormalities represent a significant challenge to global health. Conventional treatments such as autographs and allografts have limitations, leading to the exploration of bone tissue engineering (BTE) as an alternative approach. This review aims to provide a comprehensive analysis of bone regeneration mechanisms with a focus on the role of chitosan-based biomaterials and mesenchymal stem cells (MSCs) in BTE. In addition, the physiochemical and biological properties of chitosan, its potential for bone regeneration when combined with other materials and the mechanisms through which MSCs facilitate bone regeneration were investigated. In addition, different methods of scaffold development and the incorporation of MSCs into chitosan-based scaffolds were examined. Chitosan has remarkable biocompatibility, biodegradability and osteoconductivity, making it an attractive choice for BTE. Interactions between transcription factors such as Runx2 and Osterix and signaling pathways such as the BMP and Wnt pathways regulate the differentiation of MSCs and bone regeneration. Various forms of scaffolding, including porous and fibrous injections, have shown promise in BTE. The synergistic combination of chitosan and MSCs in BTE has significant potential for addressing bone defects and promoting bone regeneration, highlighting the promising future of clinical challenges posed by bone defects.

Formulation of biodegradable alginate-based nano-carriers for in-vitro drug delivery and antibacterial activity

Evaluation of the controlled release of ciprofloxacin (CIP.HCl) and the antibacterial efficacy of alginate (ALG)-based nanocarriers constitute the primary objectives of the current work. Herein, ALG-based nano-structures were prepared by the co-precipitation method and thoroughly analyzed using different characterization techniques, i.e., fourier transform infrared (FT-IR), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and zeta potential (ZP). The intense peaks emerged at 500, 545, and 750 cm-1 due to the CeO bond. Peaks that appeared at 550-600 cm-1 and 525 cm-1 are due to the stretching vibrations of FeO and ZnO bonds, respectively. Lowering of the peaks from 1640 to 1630 cm-1 and 1420 to 1384 cm-1 were observed in ALG-based nanocomposite (NC) due to the interaction of ALG with metal oxides (MO), which confirmed the formulation of CeO2/ZnFe2O4/ALG nanocomposite. The diffraction peaks at 28.6°, 56.6°, 76.5°, 37°, 47.9°, 62.3°, 74°, 13°, 21° confirmed the synthesis of MO (crystallite size 15.74 nm) and CeO2/ZnFe2O4/ALG (12 nm). In accordance with morphological studies, CeO2/ZnFe2O4 oxides had a uniform distribution throughout the relatively smooth and permeable surface of the ALG-based NC. Ciprofloxacin (CIP) was used as a model drug. Negative values of ZP revealed that CIP-loaded nanocomposite (CeO2/ZnFe2O4/ALG/CIP) had more stability than CeO2/ZnFe2O4/ALG. The maximum percentage of loading around 25 % on ALG NC was examined using the optical density (OD) method at pH 5.5. Correlation coefficients from the first order (0.971), Korsmeyer (0.9858), and Hixson (0.9021) models show the best-fitted models of the release profile in all circumstances. The release mechanism was investigated using various kinetics models. The controlled drug released was observed around 17 % at 40 °C after 3 h at pH 7.4, which is almost identical to the body temperature of a human, which is 37 °C. Similarly, after 24 h, sustained and controlled in-vitro release of the drug was studied, and it was 37, 72, and 74 % at pH 2.2, 7.4, and 9.4, respectively. Thus, prepared ALG-based NC is suitable for the controlled in-vitro release of (CIP.HCl). Metal oxides (CeO2/ZnFe2O4) and ALG-based nanocomposite (CeO2/ZnFe2O4/ALG) showed great antibacterial activity against Staphylococcus aureus (S. aureus) like 15 mm and 14 mm than Escherichia coli (E. coli).

Alginate-Sr/Mg Containing Bioactive Glass Scaffolds: The Characterization of a New 3D Composite for Bone Tissue Engineering

In bone regeneration, combining natural polymer-based scaffolds with Bioactive Glasses (BGs) is an attractive strategy to improve the mechanical properties of the structure, as well as its bioactivity and regenerative potential. Methods: For this purpose, a well-studied alginate/hydroxyapatite (Alg/HAp) porous scaffold was enhanced with an experimental bioglass (BGMS10), characterized by a high crystallization temperature and containing therapeutic ions such as strontium and magnesium. This resulted in an improved biological response compared to 45S5 Bioglass®, the "gold" standard among BGs. Porous composite scaffolds were fabricated by freeze-drying technique and characterized by scanning electron microscopy and microanalysis, infrared spectroscopy, and microcomputed tomography. The mechanical properties and cytocompatibility of the new scaffold composition were also evaluated. The addition of bioglass to the Alg/HAp network resulted in a slightly lower porosity. However, despite the change in pore size, the MG-63 cells were able to better adhere and proliferate when cultured for one week on a BG scaffold compared to the control Alg/HAp scaffolds. Thus, our findings indicate that the combination of bioactive glass BGMS10 does not affect the structural and physicochemical properties of the Alg/HAp scaffold and confers bioactive properties to the structures, making the Alg/HAp-BGMS10 scaffold a promising candidate for future application in bone tissue regeneration.

Fabrication of vascularized tissue-engineered bone models using triaxial bioprinting

Bone tissue is a highly vascularized tissue. When constructing tissue-engineered bone models, both the osteogenic and angiogenic capabilities of the construct should be carefully considered. However, fabricating a vascularized tissue-engineered bone to promote vascular formation and bone generation, while simultaneously establishing nutrition channels to facilitate nutrient exchange within the constructs, remains a significant challenge. Triaxial bioprinting, which not only allows the independent encapsulation of different cell types while simultaneously forming nutrient channels, could potentially emerge as a strategy for fabricating vascularized tissue-engineered bone. Moreover, bioinks should also be applied in combination to promote both osteogenesis and angiogenesis. In this study, employing triaxial bioprinting, we used a blend bioink of gelatin methacryloyl (GelMA), sodium alginate (Alg), and different concentrations of nano beta-tricalcium phosphate (nano β-TCP) encapsulated MC3T3-E1 preosteoblasts as the outer layer, a mixed bioink of GelMA and Alg loaded with human umbilical vein endothelial cells (HUVEC) as the middle layer, and gelatin as a sacrificial material to form nutrient channels in the inner layer to fabricate vascularized bone constructs simulating the microenvironment for bone and vascular tissues. The results showed that the addition of nano β-TCP could adjust the mechanical, swelling, and degradation properties of the constructs. Biological assessments revealed the cell viability of constructs containing different concentrations of nano β-TCP was higher than 90% on day 7, The cell-laden constructs containing 3% (w/v) nano β-TCP exhibited better osteogenic (higher Alkaline phosphatase activity and larger Osteocalcin positive area) and angiogenic (the gradual increased CD31 positive area) potential. Therefore, using triaxial bioprinting technology and employing GelMA, Alg, and nano β-TCP as bioink components could fabricate vascularized bone tissue constructs, offering a novel strategy for vascularized bone tissue engineering.

Preparation of thermochromic ink from anthocyanidin-encapsulated alginate nanoparticles for anticounterfeiting applications

In order to make commercial products less vulnerable to counterfeiting, thermochromic inks have proven to be a viable authentication strategy. Herein, we developed a thermochromic ink for authentication by combining an anthocyanidin (ACYD) extract with alginate (ALG). To increase the anthocyanidin/alginate ink stability, a mordant (ferrous sulfate) was employed to tie up the anthocyanidin biomolecules with alginate. ACYD was extracted from red-cabbage and then immobilized into alginate to serve as an environmentally friendly spectroscopic probe. Thermochromic composite inks (ACYD@ALG) were made by adjusting the content of anthocyanidin. A homogenous blue film (608 nm) was printed on a paper surface and investigated by the CIE Lab coordinate system. The blue color transformed into reddish (477 nm) when heated from 35°C to 65°C. Nanoparticles (NPs) of anthocyanidin/mordant (ACYD/M) were examined for their size and morphology to indicate diameters of 80-90 nm, whereas the ACYD/M-encapsulated alginate nanoparticles showed diameters of 120-150 nm. Multiple analytical techniques were utilized to examine the printed papers. The mechanical and rheological performance of both stamped sheets and ink fluid were explored. The cytotoxicity and antimicrobial efficacy of ink (ACYD@ALG) were investigated.

Hydroxyapatite-loaded macroporous calcium alginate hydrogels: Preparation, characterization, and in vitro evaluation

Hydrogels from natural polysaccharides are of great interest for tissue engineering. This study aims (1) to prepare hydroxyapatite-loaded macroporous calcium alginate hydrogels by novel one-step technique using internal gelation in water-frozen solutions; (2) to evaluate their physicochemical properties; (3) to estimate their ability to support cell growth and proliferation in vitro. The structure of the hydrogel samples in a swollen state was studied by confocal laser scanning microscopy and was shown to represent a system of interconnected macropores with sizes of tens micron. The swelling behavior of the hydrogels, their mechanical properties (Young's moduli) in function of a hydroxyapatite content (5-30 mass%) were studied. All hydrogel samples loaded with hydroxyapatite were found to support growth and proliferation of mouse fibroblasts (L929) at long-term cultivation for 7 days. The obtained macroporous composite Ca-Alg-HA hydrogels could be promising for tissue engineering.

Diverse Approaches in Wet-Spun Alginate Filament Production from the Textile Industry Perspective: From Process Optimization to Composite Filament Production

Alginate, categorized as a natural-based biodegradable polymer, stands out for its inherently exclusive properties. Although this unique polymer is widely processed using film, coating, and membrane technologies for different usage areas, textile applications are still limited. This study aims to compile promising approaches that will pave the way for the use of wet-spun alginate filaments in textile applications. In this regard, this study provides information about the molecular structure of alginate, the gel formation mechanism, and cross-linking using different techniques. Our literature review categorizes parameters affecting the mechanical properties of wet-spun alginate filaments, such as the effect of ion source and spinning dope concentration, needle diameter, temperature, and coagulants. Following this, a detailed and comprehensive literature review of the various approaches, such as use of additives, preparation of blended filaments, and grafted nanocrystal addition, developed by researchers to produce composite alginate filaments is presented. Additionally, studies concerning the use of different cations in the coagulation phase are reported. Moreover, studies about the functionalism of wet-spun alginate filaments have been offered.

Iron Nano Biocomposite-Infused Biopolymeric Films: A Multifunctional Approach for Robust Skin Repair

Sodium alginate (SA) biopolymeric films have various limitations such as poor mechanical properties, high vapor permeability, lack of antibacterial activity, excessive burst release, and weak cell adhesion. To overcome these limitations, a strategy involving the integration of nanofillers into an SA film matrix is explored. In this context, a cost-effective iron-containing carbon nano biocomposite (FeCNB) nanofiller is developed using a solvent-free technique. This nanocomposite is successfully incorporated into the alginate film matrix at varying concentrations (0.05, 0.1, and 0.15%) aimed at enhancing its physicochemical and biological properties for biomedical applications. Characterization through FESEM and BET analyses confirms the porous nature of the FeCNB. EDX shows the FeCNB's uniform distribution upon its integration into the film matrix, albeit without strong chemical interaction with SA. Instead, hydrogen bonding interactions become apparent in the FTIR spectra. By incorporating the FeCNB, the mechanical attributes of the films are improved and the water vapor permeability approaches the desired range (2000-2500 g/m2day). The film's swelling ratio reduction contributes to a decrease in water permeability. The antibacterial activity and sustained release property of the FeCNB-incorporated film are established using tetracycline hydrochloride (TCl), a model drug. The drug release profile resembled Korsmeyer-Peppas's release pattern. In vitro assessments via the MTT assay and scratch assay on NIH-3T3 cells reveal that FeCNB has no adverse effects on the biocompatibility of alginate films. The cell proliferation and adhesion to the SA film are significantly enhanced after infusion of the FeCNB. The in vivo study performed on the rat model demonstrates improved wound healing by FeCNB-impregnated films. Based on the comprehensive findings, the proposed FeCNB-incorporated alginate films prove to be a promising candidate for robust skin repair.

Bioengineering toolkits for potentiating organoid therapeutics

Organoids are three-dimensional, multicellular constructs that recapitulate the structural and functional features of specific organs. Because of these characteristics, organoids have been widely applied in biomedical research in recent decades. Remarkable advancements in organoid technology have positioned them as promising candidates for regenerative medicine. However, current organoids still have limitations, such as the absence of internal vasculature, limited functionality, and a small size that is not commensurate with that of actual organs. These limitations hinder their survival and regenerative effects after transplantation. Another significant concern is the reliance on mouse tumor-derived matrix in organoid culture, which is unsuitable for clinical translation due to its tumor origin and safety issues. Therefore, our aim is to describe engineering strategies and alternative biocompatible materials that can facilitate the practical applications of organoids in regenerative medicine. Furthermore, we highlight meaningful progress in organoid transplantation, with a particular emphasis on the functional restoration of various organs.

Design and in vitro evaluation of curcumin-loaded PLGA nanoparticle-embedded sodium alginate/gelatin 3D printed scaffolds for Alzheimer's disease

BACKGROUND

Targeted nanoparticles (NPs) are aimed at improving clinical outcomes by enhancing the diagnostic and therapeutic efficacy of drugs in the treatment of Alzheimer's disease (AD).

METHODS

Curcumin (CUR)-loaded poly-lactic-co-glycolic acid (PLGA) NPs (CNPs) were produced to demonstrate a prolonged release and successfully embedded into 3D printed sodium alginate (SA)/gelatin (GEL) scaffolds that can dissolve rapidly sublingually. Characterization and in vitro activity of the NPs and scaffolds were evaluated.

RESULTS

Based on the in vitro drug release studies, 99.6 % of the encapsulated CUR was released in a controlled manner within 18 days for the CNPs. In vitro cell culture studies showed that all samples exhibited cell viability above 84.2 % and no significant cytotoxic effect on SH-SY5Y cells. The samples were analyzed through 2 different pathways by PCR analysis. Real-time PCR results indicated that CNP and CNP-embedded SA/GEL scaffolds (CNPSGS) may show neuroprotective effects by modulating the Wnt/β-catenin pathway. The gene expression level of β-catenin slightly increased compared to the gene expression levels of other proteins and enzymes with these treatments. However, the PI3K/Akt/GSK-3β signaling pathway was regulated at the same time because of the crosstalk between these 2 pathways.

CONCLUSION

CNPSGS might be an effective therapeutic alternative for AD treatment.

Evaluation of the wound healing efficacy of new antibacterial polymeric nanofiber based on polyethylene oxide coated with copper nanoparticles and defensin peptide: An in-vitro to in-vivo assessment

Objective

Today, designing nanofibers with antibacterial properties using electrospinning technology is one of the attractive approaches for wound healing.

Methods

& analysis: This study aims to fabricate a nanocomposite from polyethylene oxide (PEO) coated with copper nanoparticles (NPs) and defensin peptide with wound healing and antimicrobial properties in different ratios of CuNPs/defensin (2/0 mg), (1.5/0.5 mg), and (1/1 mg) in the fixed contain polymer (98 mg). Then, the nanofiber properties were investigated by SEM, tensile, DSC, and BET analysis. Also, the antibacterial properties against S. aureus and E. coli, antioxidant, and in-vivo wound healing effects and histological analysis of the designed nanocomposites were evaluated in rat models.

Results

Our SEM images showed that CuNPs and defensin were properly coated on the PEO surface. According to the tensile, DSC, and antibacterial analysis results, the most appropriate feature was related to CuNPs/defensin (1.5/0.5 mg), with maximum elasticity, heat resistance, and antibacterial activity. Furthermore, the designed nanocomposites showed the best performance as a wound closure agent by increasing dermis and epidermis volume density, stimulating fibroblast cells and collagen fiber production, and improving skin vessels.

Conclusion

According to our results, PEO nanofibers loaded with CuNPs and defensin have the best potential for wound healing, and they can be used as antibacterial materials in the textile, drug, and medical industries.

Investigating the Effect of Processing and Material Parameters of Alginate Dialdehyde-Gelatin (ADA-GEL)-Based Hydrogels on Stiffness by XGB Machine Learning Model

To address the limitations of alginate and gelatin as separate hydrogels, partially oxidized alginate, alginate dialdehyde (ADA), is usually combined with gelatin to prepare ADA-GEL hydrogels. These hydrogels offer tunable properties, controllable degradation, and suitable stiffness for 3D bioprinting and tissue engineering applications. Several processing variables affect the final properties of the hydrogel, including degree of oxidation, gelatin content and type of crosslinking agent. In addition, in 3D-printed structures, pore size and the possible addition of a filler to make a hydrogel composite also affect the final physical and biological properties. This study utilized datasets from 13 research papers, encompassing 33 unique combinations of ADA concentration, gelatin concentration, CaCl2 and microbial transglutaminase (mTG) concentrations (as crosslinkers), pore size, bioactive glass (BG) filler content, and one identified target property of the hydrogels, stiffness, utilizing the Extreme Boost (XGB) machine learning algorithm to create a predictive model for understanding the combined influence of these parameters on hydrogel stiffness. The stiffness of ADA-GEL hydrogels is notably affected by the ADA to GEL ratio, and higher gelatin content for different ADA gel concentrations weakens the scaffold, likely due to the presence of unbound gelatin. Pore size and the inclusion of a BG particulate filler also have a significant impact on stiffness; smaller pore sizes and higher BG content lead to increased stiffness. The optimization of ADA-GEL composition and the inclusion of BG fillers are key determinants to tailor the stiffness of these 3D printed hydrogels, as found by the analysis of the available data.

Progress in the Use of Hydrogels for Antioxidant Delivery in Skin Wounds

The skin is the largest organ of the body, and it acts as a protective barrier against external factors. Chronic wounds affect millions of people worldwide and are associated with significant morbidity and reduced quality of life. One of the main factors involved in delayed wound healing is oxidative injury, which is triggered by the overproduction of reactive oxygen species. Oxidative stress has been implicated in the pathogenesis of chronic wounds, where it is known to impair wound healing by causing damage to cellular components, delaying the inflammatory phase of healing, and inhibiting the formation of new blood vessels. Thereby, the treatment of chronic wounds requires a multidisciplinary approach that addresses the underlying causes of the wound, provides optimal wound care, and promotes wound healing. Among the promising approaches to taking care of chronic wounds, antioxidants are gaining interest since they offer multiple benefits related to skin health. Therefore, in this review, we will highlight the latest advances in the use of natural polymers with antioxidants to generate tissue regeneration microenvironments for skin wound healing.

The Evolution of Technology-Driven In Vitro Models for Neurodegenerative Diseases

The alteration in the neural circuits of both central and peripheral nervous systems is closely related to the onset of neurodegenerative disorders (NDDs). Despite significant research efforts, the knowledge regarding NDD pathological processes, and the development of efficacious drugs are still limited due to the inability to access and reproduce the components of the nervous system and its intricate microenvironment. 2D culture systems are too simplistic to accurately represent the more complex and dynamic situation of cells in vivo and have therefore been surpassed by 3D systems. However, both models suffer from various limitations that can be overcome by employing two innovative technologies: organ-on-chip and 3D printing. In this review, an overview of the advantages and shortcomings of both microfluidic platforms and extracellular matrix-like biomaterials will be given. Then, the combination of microfluidics and hydrogels as a new synergistic approach to study neural disorders by analyzing the latest advances in 3D brain-on-chip for neurodegenerative research will be explored.