Alginate-based hydrogels as drug delivery vehicles in cancer treatment and their applications in wound dressing and 3D bioprinting

Microgel Single-Cell Culture Arrays on a Microfluidic Chip for Selective Expansion and Recovery of Colorectal Cancer Stem Cells

Cancer stem cells (CSCs) are rare and lack definite biomarkers, necessitating new methods for a robust expansion. Here, we developed a microfluidic single-cell culture (SCC) approach for expanding and recovering colorectal CSCs from both cell lines and tumor tissues. By incorporating alginate hydrogels with droplet microfluidics, a high-density microgel array can be formed on a microfluidic chip that allows for single-cell encapsulation and nonadhesive culture. The SCC approach takes advantage of the self-renewal property of stem cells, as only the CSCs can survive in the SCC and form tumorspheres. Consecutive imaging confirmed the formation of single-cell-derived tumorspheres, mainly from a population of small-sized cells. Through on-chip decapsulation of the alginate microgel, ∼6000 live cells can be recovered in a single run, which is sufficient for most biological assays. The recovered cells were verified to have the genetic and phenotypic characteristics of CSCs. Furthermore, multiple CSC-specific targets were identified by comparing the transcriptomics of the CSCs with the primary cancer cells. To summarize, the microgel SCC array offers a label-free approach to obtain sufficient quantities of CSCs and thus is potentially useful for understanding cancer biology and developing personalized CSC-targeting therapies.

Progress of 3D Bioprinting in Organ Manufacturing

Three-dimensional (3D) bioprinting is a family of rapid prototyping technologies, which assemble biomaterials, including cells and bioactive agents, under the control of a computer-aided design model in a layer-by-layer fashion. It has great potential in organ manufacturing areas with the combination of biology, polymers, chemistry, engineering, medicine, and mechanics. At present, 3D bioprinting technologies can be used to successfully print living tissues and organs, including blood vessels, skin, bones, cartilage, kidney, heart, and liver. The unique advantages of 3D bioprinting technologies for organ manufacturing have improved the traditional medical level significantly. In this article, we summarize the latest research progress of polymers in bioartificial organ 3D printing areas. The important characteristics of the printable polymers and the typical 3D bioprinting technologies for several complex bioartificial organs, such as the heart, liver, nerve, and skin, are introduced.

Localized disruption of redox homeostasis boosting ferroptosis of tumor by hydrogel delivery system

Ferroptosis has received ever-increasing attention due to its unparalleled mechanism in eliminating resistant tumor cells. Nevertheless, the accumulation of toxic lipid peroxides (LPOs) at the tumor site is limited by the level of lipid oxidation. Herein, by leveraging versatile sodium alginate (ALG) hydrogel, a localized ferroptosis trigger consisting of gambogic acid (GA), 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (AIPH), and Ink (a photothermal agent), was constructed via simple intratumor injection. Upon 1064 ​nm laser irradiation, the stored AIPH rapidly decomposed into alkyl radicals (R•), which aggravated LPOs in tumor cells. Meanwhile, GA could inhibit heat shock protein 90 (HSP90) to reduce the heat resistance of tumor cells, and forcefully consume glutathione (GSH) to weaken the antioxidant capacity of cells. Systematic in vitro and in vivo experiments have demonstrated that synchronous consumption of GSH and increased reactive oxygen species (ROS) facilitated reduced expression of glutathione peroxidase 4 (GPX4), which further contributed to disruption of intracellular redox homeostasis and ultimately boosted ferroptosis. This all-in-one strategy has a highly effective tumor suppression effect by depleting and generating fatal active compounds at tumor sites, which would pave a new route for the controllable, accurate, and coordinated tumor treatments.

Alginate scaffolds improve functional recovery after spinal cord injury

PURPOSE

In this systematic review and meta-analysis, the use of alginate for the repair of the damaged spinal cord was investigated.

METHODS

After an extensive search of databases including MEDLINE, SCOPUS, EMBASE and Web of Science, an initial screening was performed based on inclusion and exclusion criteria. The full text of related articles was reviewed and data mining was performed. Data were analyzed by calculating the mean of ratios between treated and untreated groups using STATA software. Subgroup analysis was also performed due to heterogeneity. Articles were subjected to quality control and PRISMA guidelines were followed.

RESULTS

Twelve studies and 17 experiments were included in the study. After SCI, alginate hydrogel had a moderate effect on motor function recovery (SMD = 0.64; 95% CI 0.28-1.00; p < 0.0001) and alginate scaffolds loaded with drugs, growth factors, or cells on the SCI group compared with untreated SCI animals showed has a strong effect in the treatment of SCI (SMD = 2.82; 95% CI 1.49-4.145; p < 0.0001). Treatment with drug/cell in combination with alginate was more strongly significant compared to the groups treated with drug/cell alone (SMD = 4.55; 95% CI 1.42-7.69; p < 0.0001). Alginate alone or in combination therapy when used as an implant, had a more significant effect than injection.

CONCLUSION

These findings suggest that alginate is an efficient scaffold for functional recovery and even a much better scaffold for drug/cell delivery after SCI.

Current Status of Mucoadhesive Gel Systems for Buccal Drug Delivery

BACKGROUND

Buccal drug delivery is a fascinating research field. Gel-based formulations present potent characteristics as buccal systems since they have great physicochemical properties.

METHODS

Among the various gels, in situ gels are viscous colloidal systems consisting of polymers; when physiological conditions change (pH, temperature, ion activation), they are transformed into the gel phase. These systems can improve bioavailability. Other systems, such as nanogels or emulgels can also be applied for buccal delivery with promising results. Polymeric gel-based systems can be produced by natural, semisynthetic, and synthetic polymers. Their main advantage is that the active molecules can be released in a sustained and controllable manner. Several gels based on chitosan are produced for the entrapment of drugs demonstrating efficient retention time and bioavailability due to chitosan mucoadhesion. Besides polysaccharides, poloxamers and carbopol are also used in buccal gels due to their high swelling ability and reversed thermal gelation behavior.

RESULTS

Herein, the authors focused on the current development of mucoadhesive gel systems used in buccal drug delivery. After explaining buccal drug delivery and mucoadhesion, various studies with hydrogels, in situ gels, and nanogels were analyzed as buccal gel systems. Various mucoadhesive gel studies with mucoadhesive polymers have been studied and summarized. This review is presented as valuable guidance to scientists in formulating buccal mucoadhesive drug delivery systems.

CONCLUSION

This review aimed to assist researchers working on buccal drug delivery by summarizing buccal drug delivery, mucoadhesion, and buccal mucoadhesive gel systems recently found in the literature.

Inhaled antibiotic-loaded polymeric nanoparticles for the management of lower respiratory tract infections

Lower respiratory tract infections (LRTIs) are one of the leading causes of deaths in the world. Currently available treatment for this disease is with high doses of antibiotics which need to be administered frequently. Instead, pulmonary delivery of drugs has been considered as one of the most efficient routes of drug delivery to the targeted areas as it provides rapid onset of action, direct deposition of drugs into the lungs, and better therapeutic effects at low doses and is self-administrable by the patients. Thus, there is a need for scientists to design more convenient pulmonary drug delivery systems towards the innovation of a novel treatment system for LRTIs. Drug-encapsulating polymer nanoparticles have been investigated for lung delivery which could significantly reduce the limitations of the currently available treatment system for LRTIs. However, the selection of an appropriate polymer carrier for the drugs is a critical issue for the successful formulations of inhalable nanoparticles. In this review, the current understanding of LRTIs, management systems for this disease and their limitations, pulmonary drug delivery systems and the challenges of drug delivery through the pulmonary route are discussed. Drug-encapsulating polymer nanoparticles for lung delivery, antibiotics used in pulmonary delivery and drug encapsulation techniques have also been reviewed. A strong emphasis is placed on the impact of drug delivery into the infected lungs.

Facile design of lidocaine-loaded polymeric hydrogel to persuade effects of local anesthesia drug delivery system: complete in vitro and in vivo toxicity analyses

The principal goal of the present investigation was to enterprise new and effective drug delivery vesicle for the sustained delivery of local anesthetic lidocaine hydrochloride (LDC), using a novel combination of copolymeric hydrogel with tetrahydroxyborate (COP–THB) to improve bioactivity and therapeutic potential. To support this contention, the physical and mechanical properties, rheological characteristics, and component release of candidate formulations were investigated. An optimized formulation of COP–THB containing LDC to an upper maximum concentration of 1.5% w/w was assessed for drug crystallization. The biocompatibility of the prepared COP–THB hydrogel was exhibited strong cell survival (96%) and growth compatibility on L929 fibroblast cell lines, which was confirmed by using methods of MTT assay and microscopic observations. The COP–THB hydrogel release pattern is distinct from that of COP–THB/LDC hydrogels by the slow-release rate and the low percentage of cumulative release. In vivo evaluations were demonstrated the anesthetic effects and toxicity value of treated samples by using mice models. In addition, COP–THB/LDC hydrogels significantly inhibit in vivo tumor growth in mice model and effectively reduced it is in vivo toxicity. The pharmacological evaluation showed that encapsulation of LDC in COP–THB hydrogels prolonged its anesthetic action with favorable in vitro and in vivo compatibility. This novel design may theoretically be used in promising studies involving the controlled release of local anesthetics.

Highlights

Development a modified sustained release system for the local anesthetic lidocaine.

PVP-THB hydrogel to improve the pharmacological properties of the drug and their anesthetic activities.

Profiles of PVP-THB/LDC showed that the effective release of associated lidocaine.

This new formulation could potentially be used in future local anesthetics.

Collagen-Alginate Composite Hydrogel: Application in Tissue Engineering and Biomedical Sciences

Alginate (ALG), a polysaccharide derived from brown seaweed, has been extensively investigated as a biomaterial not only in tissue engineering but also for numerous biomedical sciences owing to its wide availability, good compatibility, weak cytotoxicity, low cost, and ease of gelation. Nevertheless, alginate lacks cell-binding sites, limiting long-term cell survival and viability in 3D culture. Collagen (Col), a major component protein found in the extracellular matrix (ECM), exhibits excellent biocompatibility and weak immunogenicity. Furthermore, collagen contains cell-binding motifs, which facilitate cell attachment, interaction, and spreading, consequently maintaining cell viability and promoting cell proliferation. Recently, there has been a growing body of investigations into collagen-based hydrogel trying to overcome the poor mechanical properties of collagen. In particular, collagen-alginate composite (CAC) hydrogel has attracted much attention due to its excellent biocompatibility, gelling under mild conditions, low cytotoxicity, controllable mechanic properties, wider availability as well as ease of incorporation of other biomaterials and bioactive agents. This review aims to provide an overview of the properties of alginate and collagen. Moreover, the application of CAC hydrogel in tissue engineering and biomedical sciences is also discussed.

Barrier membranes for tissue regeneration in dentistry

Background: In dentistry, barrier membranes are used for guided tissue regeneration (GTR) and guided bone regeneration (GBR). Various membranes are commercially available and extensive research and development of novel membranes have been conducted. In general, membranes are required to provide barrier function, biosafety, biocompatibility and appropriate mechanical properties. In addition, membranes are expected to be bioactive to promote tissue regeneration. Objectives: This review aims to organize the fundamental characteristics of the barrier membranes that are available and studied for dentistry, based on their components. Results: The principal components of barrier membranes are divided into nonbiodegradable and biodegradable materials. Nonbiodegradable membranes are manufactured from synthetic polymers, metals or composites of these materials. The first reported barrier membrane was made from expanded polytetrafluoroethylene (e-PTFE). Titanium has also been applied for dental regenerative therapy and shows favorable barrier function. Biodegradable membranes are mainly made from natural and synthetic polymers. Collagens are popular materials that are processed for clinical use by cross-linking. Aliphatic polyesters and their copolymers have been relatively recently introduced into GTR and GBR treatments. In addition, to improve the tissue regenerative function and mechanical strength of biodegradable membranes, inorganic materials such as calcium phosphate and bioactive glass have been incorporated at the research stage. Conclusions: Currently, there are still insufficient guidelines for barrier membrane choice in GTR and GBR, therefore dentists are required to understand the characteristics of barrier membranes.

Hybrid Gelatin Hydrogels in Nanomedicine Applications

Gelatin based hydrogels are often incorporated with supporting materials such as chitosan, poly(vinyl alcohol), alginate, carbon nanotubes, and hyaluronic acid. These hybrid materials are specifically of interest in diversified nanomedicine fields as they exhibit unique physicochemical properties, antimicrobial activity, biodegradability, and biocompatibility. The applications include drug delivery, wound healing, cell culture, and tissue engineering. This paper reviews the various up-to-date methods to fabricate gelatin-based hydrogels, including UV photo-cross-linking, electrospinning, and 3D bioprinting. This paper also includes physical, chemical, mechanical, and biocompatibility characterization studies of several hybrid gelatin hydrogels and discusses their relevance in nanomedicine based applications. Challenges associated with the fabrication of hybrid materials for nanotechnology implementation, specifically in nanomedicine development, are critically discussed, and some future recommendations are provided.

Superhydrophobic Nanocoatings as Intervention against Biofilm-Associated Bacterial Infections

Biofilm formation represents a significant cause of concern as it has been associated with increased morbidity and mortality, thereby imposing a huge burden on public healthcare system throughout the world. As biofilms are usually resistant to various conventional antimicrobial interventions, they may result in severe and persistent infections, which necessitates the development of novel therapeutic strategies to combat biofilm-based infections. Physicochemical modification of the biomaterials utilized in medical devices to mitigate initial microbial attachment has been proposed as a promising strategy in combating polymicrobial infections, as the adhesion of microorganisms is typically the first step for the formation of biofilms. For instance, superhydrophobic surfaces have been shown to possess substantial anti-biofilm properties attributed to the presence of nanostructures. In this article, we provide an insight into the mechanisms underlying biofilm formation and their composition, as well as the applications of nanomaterials as superhydrophobic nanocoatings for the development of novel anti-biofilm therapies.

Bacterial Biopolymer: Its Role in Pathogenesis to Effective Biomaterials

Bacteria are considered as the major cell factories, which can effectively convert nitrogen and carbon sources to a wide variety of extracellular and intracellular biopolymers like polyamides, polysaccharides, polyphosphates, polyesters, proteinaceous compounds, and extracellular DNA. Bacterial biopolymers find applications in pathogenicity, and their diverse materialistic and chemical properties make them suitable to be used in medicinal industries. When these biopolymer compounds are obtained from pathogenic bacteria, they serve as important virulence factors, but when they are produced by non-pathogenic bacteria, they act as food components or biomaterials. There have been interdisciplinary studies going on to focus on the molecular mechanism of synthesis of bacterial biopolymers and identification of new targets for antimicrobial drugs, utilizing synthetic biology for designing and production of innovative biomaterials. This review sheds light on the mechanism of synthesis of bacterial biopolymers and its necessary modifications to be used as cell based micro-factories for the production of tailor-made biomaterials for high-end applications and their role in pathogenesis.

Silk Fibroin Enhances Cytocompatibilty and Dimensional Stability of Alginate Hydrogels for Light-Based Three-Dimensional Bioprinting

Three-dimensional (3D) bioprinting is a technology under active study for use in tissue engineering and regenerative medicine. Bioink comprises cells and polymers and is the essential material for 3D bioprinting. The characteristics of the bioink affect its printability, gelation behavior, and cell compatibility. In this study, alginate derivatives were synthesized to induce rapid gelation, and a bioink was prepared by mixing these alginate derivatives with silk fibroin to enhance cell compatibility. A low-concentration (3 wt %) alginate/silk fibroin (Alg/SF) bioink was pregelated by the ionic cross-linking of Alg to increase the viscosity for 3D printing. The rheological and mechanical properties were analyzed using a rheometer and a texture meter, respectively. Analysis of cell viability and proliferation using fibroblasts (NIH-3T3) in the bioinks showed that the Alg/SF bioink has improved cytocompatibility compared to that of conventional Alg bioinks, making it a promising material for tissue engineering.

pH/Thermo-Responsive Grafted Alginate-Based SiO2 Hybrid Nanocarrier/Hydrogel Drug Delivery Systems

We report the preparation of mesoporous silica nanoparticles covered by layer by layer (LbL) oppositely charged weak polyelectrolytes, comprising poly(allylamine hydrochloride) (PAH) and a sodium alginate, highly grafted by N-isopropylacrylamide/N-tert-butylacrylamide random copolymers, NaALG-g-P(NIPAM90-co-NtBAM10) (NaALG-g). Thanks to the pH dependence of the degree of ionization of the polyelectrolytes and the LCST-type thermosensitivity of the grafting chains of the NaALG-g, the as-prepared hybrid nanoparticles (hNP) exhibit pH/thermo-responsive drug delivery capabilities. The release kinetics of rhodamine B (RB, model drug) can be controlled by the number of PAH/NaALG-g bilayers and more importantly by the environmental conditions, namely, pH and temperature. As observed, the increase of pH and/or temperature accelerates the RB release under sink conditions. The same NaALG-g was used as gelator to fabricate a hNP@NaALG-g hydrogel composite. This formulation forms a viscous solution at room temperature, and it is transformed to a self-assembling hydrogel (sol-gel transition) upon heating at physiological temperature provided that its Tgel was regulated at 30.7 °C, by the NtBAM hydrophobic monomer incorporation in the side chains. It exhibits excellent injectability thanks to its combined thermo- and shear-responsiveness. The hNP@NaALG-g hydrogel composite, encapsulating hNP covered with one bilayer, exhibited pH-responsive sustainable drug delivery. The presented highly tunable drug delivery system (DDS) (hNP and/or composite hydrogel) might be useful for biomedical potential applications.

Recent Advances of Taxol-Loaded Biocompatible Nanocarriers Embedded in Natural Polymer-Based Hydrogels

The discovery of paclitaxel (PTX) has been a milestone in anti-cancer therapy and has promoted the development and marketing of various formulations that have revolutionized the therapeutic approach towards several malignancies. Despite its peculiar anti-cancer activity, the physico-chemical properties of PTX compromise the administration of the compound in polar media. Because of this, since the development of the first Food and Drug Administration (FDA)-approved formulation (Taxol®), consistent efforts have been made to obtain suitable delivery systems able to preserve/increase PTX efficacy and to overcome the side effects correlated to the presence of some excipients. The exploitation of natural polymers as potential materials for drug delivery purposes has favored the modulation of the bioavailability and the pharmacokinetic profiles of the drug, and in this regard, several formulations have been developed that allow the controlled release of the active compound. In this mini-review, the recent advances concerning the design and applications of natural polymer-based hydrogels containing PTX-loaded biocompatible nanocarriers are discussed. The technological features of these formulations as well as the therapeutic outcome achieved following their administration will be described, demonstrating their potential role as innovative systems to be used in anti-tumor therapy.

Coaxial Alginate Hydrogels: From Self-Assembled 3D Cellular Constructs to Long-Term Storage

Alginate as a versatile naturally occurring biomaterial has found widespread use in the biomedical field due to its unique features such as biocompatibility and biodegradability. The ability of its semipermeable hydrogels to provide a favourable microenvironment for clinically relevant cells made alginate encapsulation a leading technology for immunoisolation, 3D culture, cryopreservation as well as cell and drug delivery. The aim of this work is the evaluation of structural properties and swelling behaviour of the core-shell capsules for the encapsulation of multipotent stromal cells (MSCs), their 3D culture and cryopreservation using slow freezing. The cells were encapsulated in core-shell capsules using coaxial electrospraying, cultured for 35 days and cryopreserved. Cell viability, metabolic activity and cell-cell interactions were analysed. Cryopreservation of MSCs-laden core-shell capsules was performed according to parameters pre-selected on cell-free capsules. The results suggest that core-shell capsules produced from the low viscosity high-G alginate are superior to high-M ones in terms of stability during in vitro culture, as well as to solid beads in terms of promoting formation of viable self-assembled cellular structures and maintenance of MSCs functionality on a long-term basis. The application of 0.3 M sucrose demonstrated a beneficial effect on the integrity of capsules and viability of formed 3D cell assemblies, as compared to 10% dimethyl sulfoxide (DMSO) alone. The proposed workflow from the preparation of core-shell capsules with self-assembled cellular structures to the cryopreservation appears to be a promising strategy for their off-the-shelf availability.

pH-Sensitive Alginate/Carboxymethyl Chitosan/Aminated Chitosan Microcapsules for Efficient Encapsulation and Delivery of Diclofenac Sodium

To develop an effective pH-sensitive drug carrier, alginate (Alg), carboxymethyl chitosan (CMCs), and aminated chitosan (AmCs) derivatives were employed in this study. A simple ionic gelation technique was employed to formulate Alg-CMCs@AmCs dual polyelectrolyte complexes (PECs) microcapsules as a pH-sensitive carrier for efficient encapsulation and release of diclofenac sodium (DS) drug. The developed microcapsules were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA), and scanning electron microscope (SEM). The results clarified that formation of dual PECs significantly protected Alg microcapsules from rapid disintegration at colon conditions (pH 7.4), and greatly reduced their porosity. In addition, the dual PECs microcapsules can effectively encapsulate 95.4% of DS-drug compared to 86.3 and 68.6% for Alg and Alg-CMCs microcapsules, respectively. Higher DS-release values were achieved in simulated colonic fluid [SCF; pH 7.4] compared to those obtained in simulated gastric fluid [SGF; pH 1.2]. Moreover, the drug burst release was prevented and a sustained DS-release was achieved as the AmCs concentration increased. The results confirmed also that the developed microcapsules were biodegradable in the presence of the lysozyme enzyme. These findings emphasize that the formulated pH-sensitive microcapsules could be applied for the delivery of diclofenac sodium.

Modeling the Mechanobiology of Cancer Cell Migration Using 3D Biomimetic Hydrogels

Understanding how cancer cells migrate, and how this migration is affected by the mechanical and chemical composition of the extracellular matrix (ECM) is critical to investigate and possibly interfere with the metastatic process, which is responsible for most cancer-related deaths. In this article we review the state of the art about the use of hydrogel-based three-dimensional (3D) scaffolds as artificial platforms to model the mechanobiology of cancer cell migration. We start by briefly reviewing the concept and composition of the extracellular matrix (ECM) and the materials commonly used to recreate the cancerous ECM. Then we summarize the most relevant knowledge about the mechanobiology of cancer cell migration that has been obtained using 3D hydrogel scaffolds, and relate those discoveries to what has been observed in the clinical management of solid tumors. Finally, we review some recent methodological developments, specifically the use of novel bioprinting techniques and microfluidics to create realistic hydrogel-based models of the cancer ECM, and some of their applications in the context of the study of cancer cell migration.

A Review on the Adaption of Alginate-Gelatin Hydrogels for 3D Cultures and Bioprinting

Sustaining the vital functions of cells outside the organism requires strictly defined parameters. In order to ensure their optimal growth and development, it is necessary to provide a range of nutrients and regulators. Hydrogels are excellent materials for 3D in vitro cell cultures. Their ability to retain large amounts of liquid, as well as their biocompatibility, soft structures, and mechanical properties similar to these of living tissues, provide appropriate microenvironments that mimic extracellular matrix functions. The wide range of natural and synthetic polymeric materials, as well as the simplicity of their physico-chemical modification, allow the mechanical properties to be adjusted for different requirements. Sodium alginate-based hydrogel is a frequently used material for cell culture. The lack of cell-interactive properties makes this polysaccharide the most often applied in combination with other materials, including gelatin. The combination of both materials increases their biological activity and improves their material properties, making this combination a frequently used material in 3D printing technology. The use of hydrogels as inks in 3D printing allows the accurate manufacturing of scaffolds with complex shapes and geometries. The aim of this paper is to provide an overview of the materials used for 3D cell cultures, which are mainly alginate-gelatin hydrogels, including their properties and potential applications.

Alginate/κ-Carrageenan-Based Edible Films Incorporated with Clove Essential Oil: Physico-Chemical Characterization and Antioxidant-Antimicrobial Activity

This study aimed to enhance the properties of CaCl₂ crosslinked sodium alginate/k-carrageenan (SA/KC) incorporated with clove essential oil (CEO). An evaluation of the modification effects on physicochemical, morphological, antioxidant, and antibacterial properties was performed. The properties were observed at various SA/KC ratios (10/0 to 1.5/1), CEO (1.5% to 3%), and CaCl₂ (0% to 2%). The surface morphology was improved by addition of KC and CaCl₂. The Fourier transform infrared (FTIR) result showed insignificant alteration of film chemical structure. The X-ray diffraction (XRD) result confirmed the increased crystallinity index of the film by CaCl₂ addition. On physicochemical properties, a higher proportion of SA/KC showed the declined tensile strength, meanwhile both elongation at break and water solubility were increased. The incorporated CEO film reduced both tensile strength and water solubility; however, the elongation at break was significantly increased. The presence of Ca²⁺ ions remarkably increased the tensile strength despite decreased water solubility. Overall, the addition of KC and CaCl₂ helped in repairing the mechanical properties and flexibility. CEO incorporation showed the effectiveness of profiling the antioxidant and antimicrobial activity indicated by high 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity up to 90.32% and inhibition zone of E. coli growth up to 113.14 mm².

Stem Cell-based Dental Pulp Regeneration: Insights From Signaling Pathways

Deep caries, trauma, and severe periodontitis result in pulpitis, pulp necrosis, and eventually pulp loss. However, no clinical therapy can regenerate lost pulp. A novel pulp regeneration strategy for clinical application is urgently needed. Signaling transduction plays an essential role in regulating the regenerative potentials of dental stem cells. Cytokines or growth factors, such as stromal cell-derived factor (SDF), fibroblast growth factor (FGF), bone morphogenetic protein (BMP), vascular endothelial growth factor (VEGF), WNT, can promote the migration, proliferation, odontogenic differentiation, pro-angiogenesis, and pro-neurogenesis potentials of dental stem cells respectively. Using the methods of signaling modulation including growth factors delivery, genetic modification, and physical stimulation has been applied in multiple preclinical studies of pulp regeneration based on cell transplantation or cell homing. Transplanting dental stem cells and growth factors encapsulated into scaffold regenerated vascularized pulp-like tissue in the root canal. Also, injecting a flowable scaffold only with chemokines recruited endogenous stem/progenitor cells for pulp regeneration. Notably, dental pulp regeneration has gradually developed into the clinical phase. These findings enlightened us on a novel strategy for structural and functional pulp regeneration through elaborate modulation of signaling transduction spatially and temporally via clinically applicable growth factors delivery. But challenges, such as the adverse effects of unphysiological signaling activation, the controlled drug release system, and the safety of gene modulation, are necessary to be tested in future works for promoting the clinical translation of pulp regeneration.

Multifunctional glycerol/citric acid crosslinked polymer hydrophilic gel with absorptive and reducing properties

Multifunctional hydrogel based on glycerol/citric acid presents absorptive and reducing capacities, affording a hybrid gel containing AgNPs in the matrix.

Engineered Microgels-Their Manufacturing and Biomedical Applications

Microgels are hydrogel particles with diameters in the micrometer scale that can be fabricated in different shapes and sizes. Microgels are increasingly used for biomedical applications and for biofabrication due to their interesting features, such as injectability, modularity, porosity and tunability in respect to size, shape and mechanical properties. Fabrication methods of microgels are divided into two categories, following a top-down or bottom-up approach. Each approach has its own advantages and disadvantages and requires certain sets of materials and equipments. In this review, we discuss fabrication methods of both top-down and bottom-up approaches and point to their advantages as well as their limitations, with more focus on the bottom-up approaches. In addition, the use of microgels for a variety of biomedical applications will be discussed, including microgels for the delivery of therapeutic agents and microgels as cell carriers for the fabrication of 3D bioprinted cell-laden constructs. Microgels made from well-defined synthetic materials with a focus on rationally designed ultrashort peptides are also discussed, because they have been demonstrated to serve as an attractive alternative to much less defined naturally derived materials. Here, we will emphasize the potential and properties of ultrashort self-assembling peptides related to microgels.

Alginate Hydrogels with Tuneable Properties

Alginate is a material that has many biomedical applications due to its low toxicity and a variety of favourable physical properties. In particular, the ease in which hydrogels are formed from alginate and the variety of mechanical behaviours that can be imparted on the hydrogels, by understanding alginate chemistry and intuitive design, has made alginate the most widely investigated polysaccharide used for tissue engineering. This chapter provides an overview of alginate, from how the source and natural variations in composition can influence mechanical properties of alginate hydrogels, through to some innovative techniques used to modify and functionalise the hydrogels designed specifically for cell-based therapies. The main focus is on how these strategies of understanding and controlling the chemistry of alginates have resulted in the development of hydrogels that can be tuned to deliver the physical behaviours required for successful application. This will also highlight how research on the physicochemical properties has helped alginate evolve from a structural polysaccharide in brown seaweed into a highly tuneable, multifunctional, smart biomaterial, which is likely to find further biomedical applications in the future.

Electroresponsive Alginate-Based Hydrogels for Controlled Release of Hydrophobic Drugs

Stimuli-responsive biomaterials have attracted significant attention for the construction of on-demand drug release systems. The possibility of using external stimulation to trigger drug release is particularly enticing for hydrophobic compounds, which are not easily released by simple diffusion. In this work, an electrochemically active hydrogel, which has been prepared by gelling a mixture of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and alginate (Alg), has been loaded with curcumin (CUR), a hydrophobic drug with a wide spectrum of clinical applications. The PEDOT/Alg hydrogel is electrochemically active and organizes as segregated PEDOT- and Alg-rich domains, explaining its behavior as an electroresponsive drug delivery system. When loaded with CUR, the hydrogel demonstrates a controlled drug release upon application of a negative electrical voltage. Comparison with the release profiles obtained applying a positive voltage and in the absence of electrical stimuli indicates that the release mechanism dominating this system is complex because of not only the intermolecular interactions between the drug and the polymeric network but also the loading of a hydrophobic drug in a water-containing delivery system.

Design of an Interpenetrating Polymeric Network Hydrogel Made of Calcium-Alginate from a Thermos-Sensitive Pluronic Template as a Thermal-Ionic Reversible Wound Dressing

Polymer-based hydrogels demonstrate superior performance when used as wound dressing. An ideal dressing should possess an active healing function, absorb wound exudates, and provide a moist interface on the wound for rapid injury repair and the prevention of pain and injury during replacement of the dressing. Thus, the aim of this study was to develop a novel, reversible, smart, interpenetrating polymeric network (IPN) by utilizing the thermosensitive network of pluronic F127 (PF127) as a template to regulate the conformation of calcium-ion-crosslinked alginate. We found that the IPN hydrogels formed soft and elastic thermosensitive networks, retaining their form even after absorbing a large amount of wound exudate. The exterior of the hydrogels was made up of a rigid calcium alginate network that supported the entire hydrogel, promoting the stability of the vascular endothelial growth factor (VEGF) payload and controlling its release when the hydrogel was applied topically to wounds. Raman spectroscopy confirmed the layered structure of the hydrogel, which was found to easily disintegrate even after moderate rinsing of the wound with cold phosphate-buffered saline. Taken together, these results show that the IPN hydrogel developed in this study could be a promising delivery platform for growth factors to accelerate wound healing.

The adaptation of lipid profile of human fibroblasts to alginate 2D films and 3D printed scaffolds

BACKGROUND

The investigation of the interactions between cells and active materials is pivotal in the emerging 3D printing-biomaterial application fields. Here, lipidomics has been used to explore the early impact of alginate (ALG) hydrogel architecture (2D films or 3D printed scaffolds) and the type of gelling agent (CaCl₂ or FeCl₃) on the lipid profile of human fibroblasts.

METHODS

2D and 3D ALG scaffolds were prepared and characterized in terms of water content, swelling, mechanical resistance and morphology before human fibroblast seeding (8 days). Using a liquid chromatography-triple quadrupole-tandem mass spectrometry approach, selected ceramides (CER), lysophosphatidylcholines (LPC), lysophosphatidic acids (LPA) and free fatty acids (FFA) were analyzed.

RESULTS

The results showed a clear alteration in the CER expression profile depending of both the geometry and the gelling agent used to prepare the hydrogels. As for LPCs, the main parameter affecting their distribution is the scaffold architecture with a significant decrease in the relative expression levels of the species with higher chain length (C20 to C22) for 3D scaffolds compared to 2D films. In the case of FFAs and LPAs only slight differences were observed as a function of scaffold geometry or gelling agent.

CONCLUSIONS

Variations in the cell membrane lipid profile were observed for 3D cell cultures compared to 2D and these data are consistent with activation processes occurring through the mutual interactions between fibroblasts and ALG support. These unknown physiologically relevant changes add insights into the discussion about the relationship between biomaterial and the variations of cell biological functions.

Recent Trends in Three-Dimensional Bioinks Based on Alginate for Biomedical Applications

Three-dimensional (3D) bioprinting is an appealing and revolutionary manufacturing approach for the accurate placement of biologics, such as living cells and extracellular matrix (ECM) components, in the form of a 3D hierarchical structure to fabricate synthetic multicellular tissues. Many synthetic and natural polymers are applied as cell printing bioinks. One of them, alginate (Alg), is an inexpensive biomaterial that is among the most examined hydrogel materials intended for vascular, cartilage, and bone tissue printing. It has also been studied pertaining to the liver, kidney, and skin, due to its excellent cell response and flexible gelation preparation through divalent ions including calcium. Nevertheless, Alg hydrogels possess certain negative aspects, including weak mechanical characteristics, poor printability, poor structural stability, and poor cell attachment, which may restrict its usage along with the 3D printing approach to prepare artificial tissue. In this review paper, we prepare the accessible materials to be able to encourage and boost new Alg-based bioink formulations with superior characteristics for upcoming purposes in drug delivery systems. Moreover, the major outcomes are discussed, and the outstanding concerns regarding this area and the scope for upcoming examination are outlined.

Sulfated Polysaccharides from Marine Algae as a Basis of Modern Biotechnologies for Creating Wound Dressings: Current Achievements and Future Prospects

Wound healing involves a complex cascade of cellular, molecular, and biochemical responses and signaling processes. It consists of successive interrelated phases, the duration of which depends on a multitude of factors. Wound treatment is a major healthcare issue that can be resolved by the development of effective and affordable wound dressings based on natural materials and biologically active substances. The proper use of modern wound dressings can significantly accelerate wound healing with minimum scar mark. Sulfated polysaccharides from seaweeds, with their unique structures and biological properties, as well as with a high potential to be used in various wound treatment methods, now undoubtedly play a major role in innovative biotechnologies of modern natural interactive dressings. These natural biopolymers are a novel and promising biologically active source for designing wound dressings based on alginates, fucoidans, carrageenans, and ulvans, which serve as active and effective therapeutic tools. The goal of this review is to summarize available information about the modern wound dressing technologies based on seaweed-derived polysaccharides, including those successfully implemented in commercial products, with a focus on promising and innovative designs. Future perspectives for the use of marine-derived biopolymers necessitate summarizing and analyzing results of numerous experiments and clinical trial data, developing a scientifically substantiated approach to wound treatment, and suggesting relevant practical recommendations.