Injectable, Biodegradable Hydrogels for Tissue Engineering Applications

Exploring the potential of waste biomass-derived pectin and its functionalized derivatives for water treatment

Environmental pollution remains a constant challenge due to the indiscriminate use of fossil fuels, mining activities, chemicals, drugs, aromatic compounds, pesticides, etc. Many emerging pollutants with no fixed standards for monitoring and control are being reported. These have adverse impacts on human life and the environment around us. This alarms the wastewater management towards developing materials that can be used for bulk water treatment and are easily available, low cost, non-toxic and biodegradable. Waste biomass like pectin is extracted from fruit peels which are a discarded material. It is used in pharmaceutical and nutraceutical applications but its application as a material for water treatment is very limited in literature. The scientific gap in literature review reports are evident with discussion only on pectin based hydrogels or specific pectin derivatives for some applications. This review focuses on the chemistry, extraction, functionalization and production of pectin derivatives and their applications in water treatment processes. Pectin functionalized derivatives can be used as a flocculant, adsorbent, nano biopolymer, biochar, hybrid material, metal-organic frameworks, and scaffold for the removal of heavy metals, ions, toxic dyes, and other contaminants. The huge quantum of pectin biomass may be explored further to strengthen environmental sustainability and circular economy practices.

A peptide-based pH-sensitive antibacterial hydrogel for healing drug-resistant biofilm-infected diabetic wounds

Diabetic foot ulcers are a significant complication affecting roughly 15% of diabetic patients. These chronic wounds can be incredibly burdensome, leading to high treatment costs, potential amputations, and additional health complications. Microbiological studies reveal that bacterial infections are the primary culprit behind delayed wound healing. To solve the problem of infection at the wound site, the most fundamental thing is to kill the pathogenic bacteria. Herein, a neoteric strategy to construct novel antibacterial hydrogel COA-T3 that combined photosensitizers (PSs) and antimicrobial peptides (AMPs) via covalent coupling was proposed. Hydrogel COA-T3 composed of quaternized chitosan (QCS) and oxidized dextran (OD) was constructed for co-delivery of the photosensitizer TPI-PN and the antimicrobial peptide HHC10. In vitro and in vivo experiments demonstrated remarkable effectiveness of COA-T3 against drug-resistant bacteria. Furthermore, the hydrogel significantly promoted healing of diabetic infected wounds. This enhanced antibacterial activity is attributed to the pH-sensitive release of both PSs and AMPs within the hydrogel. Additionally, COA-T3 exhibits excellent biocompatibility, making it a promising candidate for wound dressing materials. These findings indicated that the COA-T3 hydrogel is a promising wound dressing material for promoting the healing of diabetic foot ulcers by providing an environment conducive to improved wound healing in diabetic patients.

Towards Stem Cell Therapy for Critical-Sized Segmental Bone Defects: Current Trends and Challenges on the Path to Clinical Translation

The management and reconstruction of critical-sized segmental bone defects remain a major clinical challenge for orthopaedic clinicians and surgeons. In particular, regenerative medicine approaches that involve incorporating stem cells within tissue engineering scaffolds have great promise for fracture management. This narrative review focuses on the primary components of bone tissue engineering-stem cells, scaffolds, the microenvironment, and vascularisation-addressing current advances and translational and regulatory challenges in the current landscape of stem cell therapy for critical-sized bone defects. To comprehensively explore this research area and offer insights for future treatment options in orthopaedic surgery, we have examined the latest developments and advancements in bone tissue engineering, focusing on those of clinical relevance in recent years. Finally, we present a forward-looking perspective on using stem cells in bone tissue engineering for critical-sized segmental bone defects.

Liposome-integrated hydrogel hybrids: Promising platforms for cancer therapy and tissue regeneration

Drug delivery platforms have gracefully emerged as an indispensable component of novel cancer chemotherapy, bestowing targeted drug distribution, elevating therapeutic effects, and reducing the burden of unwanted side effects. In this context, hybrid delivery systems artfully harnessing the virtues of liposomes and hydrogels bring remarkable benefits, especially for localized cancer therapy, including intensified stability, excellent amenability to hydrophobic and hydrophilic medications, controlled liberation behavior, and appropriate mucoadhesion to mucopenetration shift. Moreover, three-dimensional biocompatible liposome-integrated hydrogel networks have attracted unprecedented interest in tissue regeneration, given their tunable architecture and physicochemical properties, as well as enhanced mechanical support. This review elucidates and presents cutting-edge developments in recruiting liposome-integrated hydrogel systems for cancer treatment and tissue regeneration.

Advancements in Regenerative Hydrogels in Skin Wound Treatment: A Comprehensive Review

This state-of-the-art review explores the emerging field of regenerative hydrogels and their profound impact on the treatment of skin wounds. Regenerative hydrogels, composed mainly of water-absorbing polymers, have garnered attention in wound healing, particularly for skin wounds. Their unique properties make them well suited for tissue regeneration. Notable benefits include excellent water retention, creating a crucially moist wound environment for optimal healing, and facilitating cell migration, and proliferation. Biocompatibility is a key feature, minimizing adverse reactions and promoting the natural healing process. Acting as a supportive scaffold for cell growth, hydrogels mimic the extracellular matrix, aiding the attachment and proliferation of cells like fibroblasts and keratinocytes. Engineered for controlled drug release, hydrogels enhance wound healing by promoting angiogenesis, reducing inflammation, and preventing infection. The demonstrated acceleration of the wound healing process, particularly beneficial for chronic or impaired healing wounds, adds to their appeal. Easy application and conformity to various wound shapes make hydrogels practical, including in irregular or challenging areas. Scar minimization through tissue regeneration is crucial, especially in cosmetic and functional regions. Hydrogels contribute to pain management by creating a protective barrier, reducing friction, and fostering a soothing environment. Some hydrogels, with inherent antimicrobial properties, aid in infection prevention, which is a crucial aspect of successful wound healing. Their flexibility and ability to conform to wound contours ensure optimal tissue contact, enhancing overall treatment effectiveness. In summary, regenerative hydrogels present a promising approach for improving skin wound healing outcomes across diverse clinical scenarios. This review provides a comprehensive analysis of the benefits, mechanisms, and challenges associated with the use of regenerative hydrogels in the treatment of skin wounds. In this review, the authors likely delve into the application of rational design principles to enhance the efficacy and performance of hydrogels in promoting wound healing. Through an exploration of various methodologies and approaches, this paper is poised to highlight how these principles have been instrumental in refining the design of hydrogels, potentially revolutionizing their therapeutic potential in addressing skin wounds. By synthesizing current knowledge and highlighting potential avenues for future research, this review aims to contribute to the advancement of regenerative medicine and ultimately improve clinical outcomes for patients with skin wounds.

An Overview on the Big Players in Bone Tissue Engineering: Biomaterials, Scaffolds and Cells

Presently, millions worldwide suffer from degenerative and inflammatory bone and joint issues, comprising roughly half of chronic ailments in those over 50, leading to prolonged discomfort and physical limitations. These conditions become more prevalent with age and lifestyle factors, escalating due to the growing elderly populace. Addressing these challenges often entails surgical interventions utilizing implants or bone grafts, though these treatments may entail complications such as pain and tissue death at donor sites for grafts, along with immune rejection. To surmount these challenges, tissue engineering has emerged as a promising avenue for bone injury repair and reconstruction. It involves the use of different biomaterials and the development of three-dimensional porous matrices and scaffolds, alongside osteoprogenitor cells and growth factors to stimulate natural tissue regeneration. This review compiles methodologies that can be used to develop biomaterials that are important in bone tissue replacement and regeneration. Biomaterials for orthopedic implants, several scaffold types and production methods, as well as techniques to assess biomaterials' suitability for human use-both in laboratory settings and within living organisms-are discussed. Even though researchers have had some success, there is still room for improvements in their processing techniques, especially the ones that make scaffolds mechanically stronger without weakening their biological characteristics. Bone tissue engineering is therefore a promising area due to the rise in bone-related injuries.

Progress in cardiac tissue engineering and regeneration: Implications of gelatin-based hybrid scaffolds

Cardiovascular diseases, particularly myocardial infarction (MI), remain a leading cause of morbidity and mortality worldwide. Current treatments for MI, more palliative than curative, have limitations in reversing the disease completely. Tissue engineering (TE) has emerged as a promising strategy to address this challenge and may lead to improved therapeutic approaches for MI. Gelatin-based scaffolds, including gelatin and its derivative, gelatin methacrylate (GelMA), have attracted significant attention in cardiac tissue engineering (CTE) due to their optimal physical and biochemical properties and capacity to mimic the native extracellular matrix (ECM). CTE mainly recruits two classes of gelatin/GelMA-based scaffolds: hydrogels and nanofibrous. This article reviews state-of-the-art gelatin/GelMA-based hybrid scaffolds currently applied for CTE and regenerative therapy. Hybrid scaffolds, fabricated by combining gelatin/GelMA hydrogel or nanofibrous scaffolds with other materials such as natural/synthetic polymers, nanoparticles, protein-based biomaterials, etc., are explored for enhanced cardiac tissue regeneration functionality. The engraftment of stem/cardiac cells, bioactive molecules, or drugs into these hybrid systems shows great promise in cardiac tissue repair and regeneration. Finally, the role of gelatin/GelMA scaffolds combined with the 3D bioprinting strategy in CTE will also be briefly highlighted.

Commercial hydrogel product for drug delivery based on route of administration

Hydrogels are hydrophilic, three-dimensional, cross-linked polymers that absorb significant amounts of biological fluids or water. Hydrogels possess several favorable properties, including flexibility, stimulus-responsiveness, versatility, and structural composition. They can be categorized according to their sources, synthesis route, response to stimulus, and application. Controlling the cross-link density matrix and the hydrogels' attraction to water while they're swelling makes it easy to change their porous structure, which makes them ideal for drug delivery. Hydrogel in drug delivery can be achieved by various routes involving injectable, oral, buccal, vaginal, ocular, and transdermal administration routes. The hydrogel market is expected to grow from its 2019 valuation of USD 22.1 billion to USD 31.4 billion by 2027. Commercial hydrogels are helpful for various drug delivery applications, such as transdermal patches with controlled release characteristics, stimuli-responsive hydrogels for oral administration, and localized delivery via parenteral means. Here, we are mainly focused on the commercial hydrogel products used for drug delivery based on the described route of administration.

Advances in the Application of Black Phosphorus-Based Composite Biomedical Materials in the Field of Tissue Engineering

Black Phosphorus (BP) is a new semiconductor material with excellent biocompatibility, degradability, and optical and electrophysical properties. A growing number of studies show that BP has high potential applications in the biomedical field. This article aims to systematically review the research progress of BP composite medical materials in the field of tissue engineering, mining BP in bone regeneration, skin repair, nerve repair, inflammation, treatment methods, and the application mechanism. Furthermore, the paper discusses the shortcomings and future recommendations related to the development of BP. These shortcomings include stability, photothermal conversion capacity, preparation process, and other related issues. However, despite these challenges, the utilization of BP-based medical materials holds immense promise in revolutionizing the field of tissue repair.

A review of advanced hydrogels for cartilage tissue engineering

With the increase in weight and age of the population, the consumption of tobacco, inappropriate foods, and the reduction of sports activities in recent years, bone and joint diseases such as osteoarthritis (OA) have become more common in the world. From the past until now, various treatment strategies (e.g., microfracture treatment, Autologous Chondrocyte Implantation (ACI), and Mosaicplasty) have been investigated and studied for the prevention and treatment of this disease. However, these methods face problems such as being invasive, not fully repairing the tissue, and damaging the surrounding tissues. Tissue engineering, including cartilage tissue engineering, is one of the minimally invasive, innovative, and effective methods for the treatment and regeneration of damaged cartilage, which has attracted the attention of scientists in the fields of medicine and biomaterials engineering in the past several years. Hydrogels of different types with diverse properties have become desirable candidates for engineering and treating cartilage tissue. They can cover most of the shortcomings of other treatment methods and cause the least secondary damage to the patient. Besides using hydrogels as an ideal strategy, new drug delivery and treatment methods, such as targeted drug delivery and treatment through mechanical signaling, have been studied as interesting strategies. In this study, we review and discuss various types of hydrogels, biomaterials used for hydrogel manufacturing, cartilage-targeting drug delivery, and mechanosignaling as modern strategies for cartilage treatment.

Branched fructo-oligosaccharides from Polygonatum Cyrtonema Hua as crosslinking agents for cellulose: A novel injectable and on-demand dissolution hydrogel for diabetic wound

Oligosaccharide-containing macromolecular bio adhesives are emerging as highly promising eco-friendly materials to enhance the cytocompatibility of viscous hydrogels for wound healing applications. In our prior research, we extensively elucidated the properties of branch-structure fructo-oligosaccharides derived from Polygonatum Cyrtonema Hua (referred to as PCOS). However, the characteristics of hydrogels based on fructo-oligosaccharides remain to be fully explored. In present work, we developed an injectable, PCOS/carboxymethyl cellulose (CMC) hydrogel which is a dual ion-physical cross-linked hydrogel that can be considered as a potential diabetic wound dressing. The tests showed that the optimal ratios for hydrogel preparation were 2 % CBM 940 (Carbomer 940), 5 % CMC and 10 % PCOS. The resultant hydrogel was formulated into composite hydrogels that were then used for the treatment of full-thickness excisional wounds in a db/db diabetic mouse model. Wound closure and histological evaluation confirmed its beneficial effect on wound healing. Further morphological analysis through scanning electron microscopy images revealed a porous hydrogel structure, while Fourier-transform infrared spectroscopy provided structural insights on the crosslinking reaction. Physicochemical properties of the hybrid hydrogels determined by rheological properties, thermogravimetric, water loss rate, et al., indicated that the double crosslinking PCOS/CMC hybrid hydrogel showed enhanced dynamic mechanical properties and water retention capacity compared to the CMC cellulose matrix hydrogels. Thus, this novel PCOS-hybrid hydrogel exhibited good dissolvability and injectable properties, which was proved to facilitate for the diabetic wound healing both in vitro and in vivo test and holds a potential clinical application in the wound healing.

Strong, elastic and degradation-tolerated hydrogels composed of chitosan, silk fibroin and bioglass nanoparticles with factor-bestowed activity for bone tissue engineering

Polymer hydrogels intended for use in bone repair need to be strong, elastic, and capable of enduring degradation. However, many natural polymer hydrogels lack these essential properties and thus, are unsuitable for bone repair applications. Here, a new type of multi-network hydrogel with improved mechanical and degradation-resistant properties has been developed for use in bone repair. The hydrogel is composed of thiolated chitosan (TCH), silk fibroin (SF), and thiolated bioglass (TBG) nanoparticles (NPs). The multi-networks are built through sulfhydryl self-crosslinking, diepoxide crosslinker-involved linkages of amino or hydroxyl groups, and enzyme-mediated phenol hydroxyl crosslinking. Additionally, mesoporous TBG NPs serve as a vehicle for loading stromal cell-derived factor-1 (SDF-1) to provide the gel with cell-recruiting activity. The formulated TCH/SF/TBG hydrogels exhibit remarkably enhanced strength, elasticity, and improved degradation tolerance compared to some gels made from only TCH or SF. Furthermore, TCH/SF/TBG gels can support the growth of seeded cells and the deposition of matrix components. Some TCH/SF/TBG gels also demonstrate the ability to release SDF-1 in an approximately linear manner for a few weeks while retaining the chemotactic properties of the released SDF-1. Overall, the multi-network hydrogel has the potential as an in situ forming material for cell-recruiting bone repair and regeneration.

Kartogenin delivery systems for biomedical therapeutics and regenerative medicine

Kartogenin, a small and heterocyclic molecule, has emerged as a promising therapeutic agent for incorporation into biomaterials, owing to its unique physicochemical and biological properties. It holds potential for the regeneration of cartilage-related tissues in various common conditions and injuries. Achieving sustained release of kartogenin through appropriate formulation and efficient delivery systems is crucial for modulating cell behavior and tissue function. This review provides an overview of cutting-edge kartogenin-functionalized biomaterials, with a primarily focus on their design, structure, functions, and applications in regenerative medicine. Initially, we discuss the physicochemical properties and biological functions of kartogenin, summarizing the underlying molecular mechanisms. Subsequently, we delve into recent advancements in nanoscale and macroscopic materials for the carriage and delivery of kartogenin. Lastly, we address the opportunities and challenges presented by current biomaterial developments and explore the prospects for their application in tissue regeneration. We aim to enhance the generation of insightful ideas for the development of kartogenin delivery materials in the field of biomedical therapeutics and regenerative medicine by providing a comprehensive understanding of common preparation methods.

Injectable glucose oxidase-immobilized gelatin hydrogel prevents tumor recurrence via oxidation therapy

In clinical practice, surgery is the preferred treatment for breast cancer; however, the high recurrence rate due to residual tumors after surgery remains a major issue. Hydrogels can reduce the side effects of residual tumors and exert strong anticancer effects, thereby showing potential as therapeutic agents for suppressing tumor recurrence after surgery. Glucose oxidase (GOD)-immobilized gelatin hydrogels (GOD-gelatin hydrogel) were prepared by bioorthogonal click chemistry. Then, the anticancer effect, tumor recurrence inhibition, and biodegradability of the resulting hydrogels were evaluated through cell and animal experiments. GOD-gelatin hydrogel showed cytotoxicity and anticancer effect via H2O2 generation. Unlike free GOD, GOD-gelatin hydrogel remained in the surgical site after implant and continued to suppress tumor recurrence over time. The proposed GOD-gelatin hydrogel system can be easily implanted at the surgical site after tumor surgery, representing a novel treatment to suppress tumor recurrence without any systemic toxicity.

Injectable and Self-Adaptive Gel Scaffold Based on Heparin Microspheres for Adipogenesis of Human Adipose-Derived Stem Cells

An injectable and self-adaptive heparin microsphere-based cell scaffold was developed to achieve adipose regeneration. Simultaneously, the cell scaffold exhibited a dynamic architecture, self-regulated glucose levels, sustained insulin delivery, and steady viscoelastic properties for adipogenesis. The dynamic cell scaffold is cross-linked by the boronate-diol interaction among heparin-based microspheres, which have boronate and maltose groups. Because of the boronate-maltose ester bonds, the gelatinous complex would be partially dismantled and readily display glucose-sensitive performance by free glucose via competitive displacement. The dynamic cross-linking heparin microsphere scaffold can deliver the lipogenic drug insulin to enhance lipid filling, which has an impact on fat tissue enhancement. A 4-week in vitro cell culture demonstrated that the dynamic heparin microsphere-based cell scaffold, through loading with insulin, showed significantly higher efficiency in promoting ASC differentiation compared with traditional 3D culture methods. In vivo histological results further demonstrated that there was a significant increase in adipose in the proposed cell scaffold, which proved to be statistically significant compared with traditional biomaterials. Notable stain expression of the FABP4 and PPAR-γ genes was also observed in the dynamic cell scaffold containing insulin, which was more similar to natural fat.

A Balance between Inter- and Intra-Microgel Mechanics Governs Stem Cell Viability in Injectable Dynamic Granular Hydrogels

Injectable hydrogels are increasingly explored for the delivery of cells to tissue. These materials exhibit both liquid-like properties, protecting cells from mechanical stress during injection, and solid-like properties, providing a stable 3D engraftment niche. Many strategies for modulating injectable hydrogels tune liquid- and solid-like material properties simultaneously, such that formulation changes designed to improve injectability can reduce stability at the delivery site. The ability to independently tune liquid- and solid-like properties would greatly facilitate formulation development. Here, such a strategy is presented in which cells are ensconced in the pores between microscopic granular hyaluronic acid (HA) hydrogels (microgels), where elasticity is tuned with static covalent intra-microgel crosslinks and flowability with mechanosensitive adamantane-cyclodextrin (AC) inter-microgel crosslinks. Using the same AC-free microgels as a 3D printing support bath, the location of each cell is preserved as it exits the needle, allowing identification of the mechanism driving mechanical trauma-induced cell death. The microgel AC concentration is varied to find the threshold from microgel yielding- to AC interaction-dominated injectability, and this threshold is exploited to fabricate a microgel with better injection-protecting performance. This delivery strategy, and the balance between intra- and inter-microgel properties it reveals, may facilitate the development of new cell injection formulations.

Novel Vectors and Administrations for mRNA Delivery

mRNA therapy has shown great potential in infectious disease vaccines, cancer immunotherapy, protein replacement therapy, gene editing, and other fields due to its central role in all life processes. However, mRNA is challenging to pass through the cell membrane due to its significant negative charges and degradation from RNase, so the key to mRNA therapy is efficient packaging and delivery of it with appropriate vectors. Presently researchers have developed various vectors such as viruses and liposomes, but these conventional vectors are now difficult to meet the growing requirement like safety, efficiency, and targeting, so many novel delivery vectors with unique advantages have emerged recently. This review mainly introduces two categories of novel vectors: biomacromolecules and inorganic nanoparticles, as well as two novel methods of control and administration based on these novel vectors: controlled-release administration and non-invasive administration. These novel delivery strategies have the advantages of high safety, biocompatibility, versatility, intelligence, and targeting. This paper analyzes the challenges faced by the field of mRNA delivery in depth, and discusses how to use the characteristics of novel vectors and administrations to solve these problems.

Intelligent Vascularized 3D/4D/5D/6D-Printed Tissue Scaffolds

Blood vessels are essential for nutrient and oxygen delivery and waste removal. Scaffold-repairing materials with functional vascular networks are widely used in bone tissue engineering. Additive manufacturing is a manufacturing technology that creates three-dimensional solids by stacking substances layer by layer, mainly including but not limited to 3D printing, but also 4D printing, 5D printing and 6D printing. It can be effectively combined with vascularization to meet the needs of vascularized tissue scaffolds by precisely tuning the mechanical structure and biological properties of smart vascular scaffolds. Herein, the development of neovascularization to vascularization to bone tissue engineering is systematically discussed in terms of the importance of vascularization to the tissue. Additionally, the research progress and future prospects of vascularized 3D printed scaffold materials are highlighted and presented in four categories: functional vascularized 3D printed scaffolds, cell-based vascularized 3D printed scaffolds, vascularized 3D printed scaffolds loaded with specific carriers and bionic vascularized 3D printed scaffolds. Finally, a brief review of vascularized additive manufacturing-tissue scaffolds in related tissues such as the vascular tissue engineering, cardiovascular system, skeletal muscle, soft tissue and a discussion of the challenges and development efforts leading to significant advances in intelligent vascularized tissue regeneration is presented.

Recent Advances in the Development of Biomimetic Materials

In this review, we focused on recent efforts in the design and development of materials with biomimetic properties. Innovative methods promise to emulate cell microenvironments and tissue functions, but many aspects regarding cellular communication, motility, and responsiveness remain to be explained. We photographed the state-of-the-art advancements in biomimetics, and discussed the complexity of a "bottom-up" artificial construction of living systems, with particular highlights on hydrogels, collagen-based composites, surface modifications, and three-dimensional (3D) bioprinting applications. Fast-paced 3D printing and artificial intelligence, nevertheless, collide with reality: How difficult can it be to build reproducible biomimetic materials at a real scale in line with the complexity of living systems? Nowadays, science is in urgent need of bioengineering technologies for the practical use of bioinspired and biomimetics for medicine and clinics.

Integration of Extracellular Matrices into Organ-on-Chip Systems

The extracellular matrix (ECM) is a complex, dynamic network present within all tissues and organs that not only acts as a mechanical support and anchorage point but can also direct fundamental cell behavior, function, and characteristics. Although the importance of the ECM is well established, the integration of well-controlled ECMs into Organ-on-Chip (OoC) platforms remains challenging and the methods to modulate and assess ECM properties on OoCs remain underdeveloped. In this review, current state-of-the-art design and assessment of in vitro ECM environments is discussed with a focus on their integration into OoCs. Among other things, synthetic and natural hydrogels, as well as polydimethylsiloxane (PDMS) used as substrates, coatings, or cell culture membranes are reviewed in terms of their ability to mimic the native ECM and their accessibility for characterization. The intricate interplay among materials, OoC architecture, and ECM characterization is critically discussed as it significantly complicates the design of ECM-related studies, comparability between works, and reproducibility that can be achieved across research laboratories. Improving the biomimetic nature of OoCs by integrating properly considered ECMs would contribute to their further adoption as replacements for animal models, and precisely tailored ECM properties would promote the use of OoCs in mechanobiology.

Choice of Protein, Not Its Amyloid-Fold, Determines the Success of Amyloid-Based Scaffolds for Cartilage Tissue Regeneration

The formation of fibrocartilage during articular cartilage regeneration remains a clinical problem affecting adequate restoration of articular cartilage in joints. To stimulate chondrocytes to form articular cartilage, we investigated the use of amyloid fibril-based scaffolds. The proteins α-synuclein, β-lactoglobulin, and lysozyme were induced to self-assemble into amyloid fibrils and, during dialysis, formed micrometer scale amyloid networks that resemble the cartilage extracellular matrix. Our results show that lysozyme amyloid micronetworks supported chondrocyte viability and extracellular matrix deposition, while α-synuclein and β-lactoglobulin maintained cell viability. With this study, we not only confirm the possible use of amyloid materials for tissue regeneration but also demonstrate that the choice of protein, rather than its amyloid-fold per se, affects the cellular response and tissue formation.

Injectable hydrogels in central nervous system: Unique and novel platforms for promoting extracellular matrix remodeling and tissue engineering

Repairing central nervous system (CNS) is difficult due to the inability of neurons to recover after damage. A clinically acceptable treatment to promote CNS functional recovery and regeneration is currently unavailable. According to recent studies, injectable hydrogels as biodegradable scaffolds for CNS tissue engineering and regeneration have exceptionally desirable attributes. Hydrogel has a biomimetic structure similar to extracellular matrix, hence has been considered a 3D scaffold for CNS regeneration. An interesting new type of hydrogel, injectable hydrogels, can be injected into target areas with little invasiveness and imitate several aspects of CNS. Injectable hydrogels are being researched as therapeutic agents because they may imitate numerous properties of CNS tissues and hence reduce subsequent injury and regenerate neural tissue. Because of their less adverse effects and cost, easier use and implantation with less pain, and faster regeneration capacity, injectable hydrogels, are more desirable than non-injectable hydrogels. This article discusses the pathophysiology of CNS and the use of several kinds of injectable hydrogels for brain and spinal cord tissue engineering, paying particular emphasis to recent experimental studies.

Synthesis, Characterization, Properties, and Biomedical Application of Chitosan-Based Hydrogels

The prospective applications of chitosan-based hydrogels (CBHs), a category of biocompatible and biodegradable materials, in biomedical disciplines such as tissue engineering, wound healing, drug delivery, and biosensing have garnered great interest. The synthesis and characterization processes used to create CBHs play a significant role in determining their characteristics and effectiveness. The qualities of CBHs might be greatly influenced by tailoring the manufacturing method to get certain traits, including porosity, swelling, mechanical strength, and bioactivity. Additionally, characterization methods aid in gaining access to the microstructures and properties of CBHs. Herein, this review provides a comprehensive assessment of the state-of-the-art with a focus on the affiliation between particular properties and domains in biomedicine. Moreover, this review highlights the beneficial properties and wide application of stimuli-responsive CBHs. The main obstacles and prospects for the future of CBH development for biomedical applications are also covered in this review.

Papaverine loaded injectable and thermosensitive hydrogel system for improving survival of rat dorsal skin flaps

Vasospasm during reconstructive microsurgery is a common, uncertain, and devastating phenomena concerning flap survival. Topical vasodilators as antispasmodic agents are widely used to reduce vasospasm and enhance microvascular anastomosis in reconstructive microsurgery. In this study, thermo-responsive hydrogel (CNH) was fabricated by grafting chitosan (CS) and hyaluronic acid (HA) to poly(N-isopropylacrylamide) (PNIPAM). Papaverine, an anti-spasmodic agent, was then loaded to evaluate its effect on rat skin flap survival. Post-operative flap survival area and water content of rat dorsal skin flap were measured at 7 days after intradermal application of control hydrogel (CNHP0.0) and papaverine loaded hydrogel (CNHP0.4). Tissue malondialdehyde (MDA) content and superoxide dismutase (SOD) activity was measured using enzyme linked immunosorbent assay (ELISA) to determine oxidative stress in flaps. Hematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) were performed to evaluate flap angiogenesis and inflammatory markers. Results showed that CNHP0.4 hydrogel could reduce tissue edema (35.63 ± 4.01%), improve flap survival area (76.30 ± 5.39%), increase SOD activity and decrease MDA content. Consequently, it also increased mean vessel density, upregulated expression of CD34 and VEGF, decreased macrophage infiltration, and reduced CD68 and CCR7 expression based on IHC staining. Overall, these results indicate that CNHP0.4 hydrogel can enhance angiogenesis with anti-oxidative and anti-inflammatory effects and promote skin flap survival by preventing vascular spasm.

New Challenges and Prospective Applications of Three-Dimensional Bioactive Polymeric Hydrogels in Oral and Craniofacial Tissue Engineering: A Narrative Review

Regenerative medicine, and dentistry offers enormous potential for enhancing treatment results and has been fueled by bioengineering breakthroughs over the previous few decades. Bioengineered tissues and constructing functional structures capable of healing, maintaining, and regenerating damaged tissues and organs have had a broad influence on medicine and dentistry. Approaches for combining bioinspired materials, cells, and therapeutic chemicals are critical in stimulating tissue regeneration or as medicinal systems. Because of its capacity to maintain an unique 3D form, offer physical stability for the cells in produced tissues, and replicate the native tissues, hydrogels have been utilized as one of the most frequent tissue engineering scaffolds during the last twenty years. Hydrogels' high water content can provide an excellent conditions for cell viability as well as an architecture that mimics real tissues, bone, and cartilage. Hydrogels have been used to enable cell immobilization and growth factor application. This paper summarizes the features, structure, synthesis and production methods, uses, new challenges, and future prospects of bioactive polymeric hydrogels in dental and osseous tissue engineering of clinical, exploring, systematical and scientific applications.

Biofabrication of engineered dento-alveolar tissue

Oral health is essential for a good overall health. Dento-alveolar conditions have a high prevalence, ranging from tooth decay periodontitis to alveolar bone resorption. However, oral tissues exhibit a limited regenerative capacity, and full recovery is challenging. Therefore, regenerative therapies for dento-alveolar tissue (e.g., alveolar bone, periodontal membrane, dentin-pulp complex) have gained much attention, and novel approaches have been proposed in recent decades. This review focuses on the cells, biomaterials and the biofabrication methods used to develop therapies for tooth root bioengineering. Examples of the techniques covered are the multitude of additive manufacturing techniques and bioprinting approaches used to create scaffolds or tissue constructs. Furthermore, biomaterials and stem cells utilized during biofabrication will also be described for different target tissues. As these new therapies gradually become a reality in the lab, the translation to the clinic is still minute, with a further need to overcome multiple challenges and broaden the clinical application of these alternatives.

Biomedical applications of chitosan/silk fibroin composites: A review

Natural polymers have been used in the biomedical fields for decades, mainly derived from animals and plants with high similarities with biomacromolecules in the human body. As an alkaline polysaccharide, chitosan (CS) attracts much attention in tissue regeneration and drug delivery with favorable biocompatibility, biodegradation, and antibacterial activity. However, to overcome its mechanical properties and degradation behavior drawbacks, a robust fibrous protein-silk fibroin (SF) was introduced to prepare the CS/SF composites. Not only can CS be combined with SF via the amide and hydrogen bond formation, but also their functions are complementary and tunable with the blending ratio. To further improve the performances of CS/SF composites, natural (e.g., hyaluronic acid and collagen) and synthetic biopolymers (e.g., polyvinyl alcohol and hexanone) were incorporated. Also, the CS/SF composites acted as slow-release carriers for inorganic non-metals (e.g., hydroxyapatite and graphene) and metal particles (e.g., silver and magnesium), which could enhance cell functions, facilitate tissue healing, and inhibit bacterial growth. This review presents the state-of-the-art and future perspectives of different biomaterials combined with CS/SF composites as sponges, hydrogels, membranes, particles, and coatings. Emphasis is devoted to the biological potentialities of these hybrid systems, which look rather promising toward a multitude of applications.

Shape-memory collagen scaffold combined with hyaluronic acid for repairing intervertebral disc

BACKGROUND

Intervertebral disc degeneration (IVDD) is a common cause of chronic low back pain (LBP) and a socioeconomic burden worldwide. Conservative therapies and surgical treatments provide only symptomatic pain relief without promoting intervertebral disc (IVD) regeneration. Therefore, the clinical demand for disc regenerative therapies for disc repair is high.

METHODS

In this study, we used a rat tail nucleotomy model to develop mechanically stable collagen-cryogel and fibrillated collagen with shape-memory for use in minimally invasive surgery for effective treatment of IVDD. The collagen was loaded with hyaluronic acid (HA) into a rat tail nucleotomy model.

RESULTS

The shape-memory collagen structures exhibited outstanding chondrogenic activities, having completely similar physical properties to those of a typical shape-memory alginate construct in terms of water absorption, compressive properties, and shape-memorability behavior. The treatment of rat tail nucleotomy model with shape-memory collagen-cryogel/HA alleviated mechanical allodynia, maintained a higher concentration of water content, and preserved the disc structure by restoring the matrix proteins.

CONCLUSION

According to these results, the collagen-based structure could effectively repair and maintain the IVD matrix better than the controls, including HA only and shape-memory alginate with HA.

Topological Optimisation Structure Design for Personalisation of Hydrogel Controlled Drug Delivery System

Personalised controlled drug delivery systems (CDDSs) can adjust drug concentration levels according to patient needs, which has enormous research prospects in precision medicine. In this study, the topological optimisation method was utilised in the structural design of a hydrogel CDDS to achieve a parameter-based adjustment of the drug average concentration in the hydrogel. A polyacrylamide/sodium alginate dual-network hydrogel was selected as a drug carrier, and tetracycline hydrochloride was used as a model drug. The topological optimisation model of the hydrogel CDDS was developed. The effects of the mesh size, target concentration, and volume factor on the optimised results were investigated. Hydrogel flow channel structures were obtained, which satisfied the different target concentrations. To verify the rationality of the optimisation model, in vitro drug release experiments were carried out. The results show that the hydrogel CDDS can control drug release within 7 days, and the drug release tends to follow zero-order release behaviour. The adjustable average concentration of tetracycline hydrochloride in hydrogel CDDS is recommended in the range of 20.79 to 31.04 mol/m³. This novel method provides a reference for personalised structure design of CDDS in the context of precision medicine.

A Nanoparticle Ink Allowing the High Precision Visualization of Tissue Engineered Scaffolds by MRI

Hydrogels are widely used as cell scaffolds in several biomedical applications. Once implanted in vivo, cell scaffolds must often be visualized, and monitored overtime. However, cell scaffolds appear poorly contrasted in most biomedical imaging modalities such as magnetic resonance imaging (MRI). MRI is the imaging technique of choice for high-resolution visualization of low-density, water-rich tissues. Attempts to enhance hydrogel contrast in MRI are performed with "negative" contrast agents that produce several image artifacts impeding the delineation of the implant's contours. In this study, a magnetic ink based on ultra-small iron oxide nanoparticles (USPIONs; <5 nm diameter cores) is developed and integrated into biocompatible alginate hydrogel used in cell scaffolding applications. Relaxometric properties of the magnetic hydrogel are measured, as well as biocompatibility and MR-visibility (T₁ -weighted mode; in vitro and in vivo). A 2-week MR follow-up study is performed in the mouse model, demonstrating no image artifacts, and the retention of "positive" contrast overtime, which allows very precise delineation of tissue grafts with MRI. Finally, a 3D-contouring procedure developed to facilitate graft delineation and geometrical conformity assessment is applied on an inverted template alginate pore network. This proof-of-concept establishes the possibility to reveal precisely engineered hydrogel structures using this USPIONs ink high-visibility approach.

Biodegradable Materials for Tissue Engineering: Development, Classification and Current Applications

The goal of this review is to map the current state of biodegradable materials that are used in tissue engineering for a variety of applications. At the beginning, the paper briefly identifies typical clinical indications in orthopedics for the use of biodegradable implants. Subsequently, the most frequent groups of biodegradable materials are identified, classified, and analyzed. To this end, a bibliometric analysis was applied to evaluate the evolution of the scientific literature in selected topics of the subject. The special focus of this study is on polymeric biodegradable materials that have been widely used for tissue engineering and regenerative medicine. Moreover, to outline current research trends and future research directions in this area, selected smart biodegradable materials are characterized, categorized, and discussed. Finally, pertinent conclusions regarding the applicability of biodegradable materials are drawn and recommendations for future research are suggested to drive this line of research forward.

Synthesis and Characterizations of Bioactive Glass Nanoparticle-Incorporated Triblock Copolymeric Injectable Hydrogel for Bone Tissue Engineering

Recently, injectable hydrogels have attracted much interest in tissue engineering (TE) applications because of their controlled flowability, adaptability, and easy handling properties. This work emphasizes the synthesis and characterizations of bioactive glass (BAG) nanoparticle-reinforced poly(ethylene glycol) (PEG)- and poly(N-vinylcarbazole) (pNVC)-based minimally invasive composite injectable hydrogel suitable for bone regeneration. First, the copolymer was synthesized from a combination of PEG and pNVC through reversible addition-fragmentation chain-transfer (RAFT) polymerization and nanocomposite hydrogel constructs were subsequently prepared by conjugating BAG particles at varying loading concentrations. Gel permeation chromatography (GPC) analysis confirmed the controlled nature of the polymer. Various physicochemical characterization results confirmed the successful synthesis of copolymer and nanocomposite hydrogels that showed good gelling and injectability properties. Our optimal nanocomposite hydrogel formulation showed excellent swelling properties in comparison to the copolymeric hydrogel due to the presence of hydrophilic BAG particles. The bone cell proliferation rate was found to be evidently higher in the nanocomposite hydrogel than in the copolymeric hydrogel. Moreover, the enhanced level of ALP activity and apatite mineralization for the nanocomposite in comparison to that for the copolymeric hydrogel indicates accelerated in vitro osteogenesis. Overall, our study findings indicate BAG particle-conjugated nanocomposite hydrogels can be used as promising grafting materials in orthopedic reconstructive surgeries complementary to conventional bone graft substitutes in cancellous bone defects due to their 3D porous framework, minimal invasiveness, and ability to form any desired shape to match irregular bone defects.

Ultrasensitive and Highly Stretchable Multiple-Crosslinked Ionic Hydrogel Sensors with Long-Term Stability

Flexible hydrogels are receiving significant attention for their application in wearable sensors. However, most hydrogel materials exhibit weak and one-time adhesion, low sensitivity, ice crystallization, water evaporation, and poor self-recovery, thereby limiting their application as sensors. These issues are only partly addressed in previous studies. Herein, a multiple-crosslinked poly(2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide-co-acrylamide) (P(SBMA-co-AAm)) multifunctional hydrogel is prepared via a one-pot synthesis method to overcome the aforementioned limitations. Specifically, ions, glycerol, and 2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide are incorporated to reduce the freezing point and improve the moisture retention ability. The proposed hydrogel is superior to existing hydrogels because it exhibits good stretchability (a strain of 2900%), self-healing properties, and transparency through effective energy dissipation in its dynamic crosslinked network. Further, 2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide as a zwitterion monomer results in an excellent gauge factor of 43.4 at strains of 1300-1600% by improving the ion transportability and achieving a strong adhesion of 20.9 kPa owing to the dipole-dipole moment. The proposed hydrogel is promising for next-generation biomedical applications, such as soft robots, and health monitoring.

Fibrin-Enriched Cardiac Extracellular Matrix Hydrogel Promotes In Vitro Angiogenesis

Angiogenesis is essential for cardiac repair after myocardial infarction. Promoting angiogenesis has been demonstrated as an effective approach for myocardial infarction treatment. Several different strategies for inducing myocardial angiogenesis have been explored, including exogenous delivery of angiogenic genes, proteins, microRNAs, cells, and extracellular vesicles. Various types of injectable hydrogels have been investigated for cardiac tissue repair. One of the most promising injectable hydrogels in cardiac regeneration is a cardiac extracellular matrix hydrogel that is derived from decellularized porcine myocardium. It can be delivered minimally invasively via transendocardial delivery. The safety and efficacy of cardiac extracellular matrix hydrogels have been shown in small and large animal myocardial infarction models as well as clinical trials. The main mechanisms underlying the therapeutic benefits of cardiac extracellular matrix hydrogels have been elucidated and involved in the modulation of the immune response, downregulation of pathways related to heart failure progression and fibrosis, upregulation of genes important for cardiac muscle contraction, and enhancing cardiomyocyte differentiation and maturation from stem cells. However, no potent capillary network formation induced by cardiac extracellular matrix hydrogels has been reported. In this study, we tested the feasibility of incorporating a fibrin matrix into cardiac extracellular matrix hydrogels to improve the angiogenic properties of the hydrogel. Our in vitro results demonstrate that fibrin-enriched cardiac extracellular matrix hydrogels can induce robust endothelial cell tube formation from human umbilical vein endothelial cells and promote the sprouting of human mesenchymal stem cell spheroids. The obtained information from this study is very critical toward the future in vivo evaluation of fibrin-enriched cardiac extracellular matrix hydrogels in promoting myocardial angiogenesis.

Rapid Preparation of Antifreezing Conductive Hydrogels for Flexible Strain Sensors and Supercapacitors

Conductive hydrogels have shown great promise in flexible electronics, but their practical applications may be impeded by the time-consuming and energy-consuming polymerization process. We proposed a sodium lignosulfonate-Fe (SLS-Fe) strategy to address this challenge and took advantage of carboxymethyl cellulose (CMC) and poly(acrylic acid) to prepare the CMC/PAA/Fe3+/LiCl interpenetrating conductive hydrogels with good self-healing properties, antifreezing properties, and a 6-fold increase in conductivity in this study. The hydrogel-based flexible strain sensors demonstrated a broad detection range (400%), high sensitivity (GF = 6.19 at 200-400%), and human motion detection capability. The hydrogel-based supercapacitor exhibited a single-electrode specific capacitance of 122.36 F g-1 which successfully powered LEDs. Furthermore, the supercapacitor showed a single-electrode specific capacitance of 83.16 F g-1 at -23 °C (68% of the one exhibited at 25 °C). Therefore, the multifunctional performance of the CMC/PAA/Fe3+/LiCl hydrogel is anticipated to play an exemplary role in a new generation of flexible electronics.

Thermosensitive and biodegradable PCL-based hydrogels: potential scaffolds for cartilage tissue engineering

Due to a lack of sufficient blood supply and unique physicochemical properties, the treatment of injured cartilage is laborious and needs an efficient strategy. Unfortunately, most of the current therapeutic approaches are, but not completely, unable to restore the function of injured cartilage. Tissue engineering-based modalities are an alternative option to reconstruct the injured tissue. Considering the unique structure and consistency of cartilage tissue (osteochondral junction), it is mandatory to apply distinct biomaterials with unique properties slightly different from scaffolds used for soft tissues. PCL is extensively used for the fabrication of fine therapeutic scaffolds to accelerate the restorative process. Thermosensitive PCL hydrogels with distinct chemical compositions have paved the way for sophisticated cartilage regeneration. This review aimed to collect recent findings regarding the application of PCL in hydrogels blended with natural, synthetic materials in the context of cartilage healing.

A composite hydrogel scaffold based on collagen and carboxymethyl chitosan for cartilage regeneration through one-step chemical crosslinking

The number of cases of cartilage damage worldwide is increasing annually and this problem severely limits an individual's physical activities, subsequently contributing to additional medical problems. Hydrogels can repair cartilage defects and promote cartilage regeneration. In this study, a composite hydrogel scaffold was prepared with collagen (COL), carboxymethyl chitosan (CMC), and the Arg-Gly-Asp (RGD) peptide through one-step chemical crosslinking, in which the three compositions ratio was especially investigated. The hydrogel scaffold performed well in cell adhesion and biocompatibility experiments, mainly due to the favorable porosity (the aperture was concentrated at 100 μm and the porosity was >70 %) and RGD concentration (2 mM RGD was the optimal concentration, which could effectively improve the attachment of BMSCs to the stent). Moreover, bone marrow mesenchymal stem cells (BMSCs) filled in the hydrogel scaffold, together with transforming growth factor TGF-β3, which was applied to evaluate the feasibility on the repair of the injured cartilage of the rat. In vitro and in vivo study, according to the results of cell proliferation and cytotoxicity, the hydrogel material had no toxic effect on cells, and the COL2/CMC1 hydrogel scaffold had the most obvious role in promoting cell proliferation. The results of pathological section showed that the cell scaffold complex group provided good mechanical properties for the wound and supplemented the stem cells derived from chondrocytes and showed good cartilage defect repair effect; In the scaffold group, the surface fibrosis of the injured area was mainly filled with fibrocartilage and other collagen fibers The hydrogel/BMSCs complex based on COL and CMC can be beneficial for the regeneration of cartilage.

Active Loading of Pectin Hydrogels for Targeted Drug Delivery

Hydrogels provide a promising method for the targeted delivery of protein drugs. Loading the protein drug into the hydrogel free volume can be challenging due to limited quantities of the drug (e.g., growth factor) and complex physicochemical properties of the hydrogel. Here, we investigated both passive and active loading of the heteropolysaccharide hydrogel pectin. Passive loading of glass phase pectin films was evaluated by contact angles and fractional thickness of the pectin films. Four pectin sources demonstrated mean contact angles of 88° with water and 122° with pleural fluid (p < 0.05). Slow kinetics and evaporative losses precluded passive loading. In contrast, active loading of the translucent pectin films was evaluated with the colorimetric tracer methylene blue. Active loading parameters were systematically varied and recorded at 500 points/s. The distribution of the tracer was evaluated by image morphometry. Active loading of the tracer into the pectin films required the optimization of probe velocity, compression force, and contact time. We conclude that active loading using pectin-specific conditions is required for the efficient embedding of low viscosity liquids into pectin hydrogels.

A comprehensive review of properties of the biocompatible thin films on biodegradable Mg alloys

Magnesium (Mg) and its alloys have attracted attention as biodegradable materials for biomedical applications owing to their mechanical properties being comparable to that of bone. Mg is a vital trace element in many enzymes and thus forms one of the essential factors for human metabolism. However, before being used in biomedical applications, the early stage or fast degradation of Mg and its alloys in the physiological environment should be controlled. The degradation of Mg alloys is a critical criterion that can be controlled by a surface modification which is an effective process for conserving their desired properties. Different coating methods have been employed to modify Mg surfaces to provide good corrosion resistance and biocompatibility. This review aims to provide information on different coatings and discuss their physical and biological properties. Finally, the current withstanding challenges have been highlighted and discussed, followed by shedding some light on future perspectives.

Effective BMP-2 Release and Mineralization on a Graphene Oxide/Polyvinylpyrrolidone Hydrogel Forming Poly (ε-Caprolactone) Nanofibrous Scaffolds

PCL nanofibrous scaffolds are widely used as bone scaffolds, and they can increase the efficiency of bone regeneration by loading drugs and/or growth factors onto them. However, to obtain a more effective bone regeneration effect, it is necessary to increase drug loading and release efficiency. In this study, conductive hydrogel forming nanofibrous scaffolds were prepared to increase drug efficiency. GO has an excellent conductivity and biocompatibility, making it an efficient conductive polymer for bone differentiation. Electrospun PCL was immersed in a mixed solution of GO and PVP and then crosslinked using gamma-ray irradiation. It was confirmed that GO/PVP-PCL was successfully prepared through its characterization (morphology, thermal, chemical, electrical, and biological properties). In addition, drug-release efficiency was confirmed by electrical stimulation after loading the sample with BMP-2, a bone-regeneration growth factor. Compared to PCL, it was confirmed that GO/PVP-PCL has an approximately 20% improved drug-release efficiency and an excellent mineralization of the scaffolds using SBF. After culturing MG63 cells on GO/PVP-PCL, a high effect on osteodifferentiation was confirmed by ALP activity. Therefore, GO/PVP-PCL prepared by a gamma-ray-induced crosslinking reaction is expected to be used as biomaterial for bone-tissue engineering.

Preparation and Characterization of Alginate Hydrogel Fibers Reinforced by Cotton for Biomedical Applications

In this study, cotton-reinforced alginate hydrogel fibers were successfully synthesized using the wet spinning technique to improve hydrogel fibers' mechanical strength and durability. Structural, chemical, and mechanical properties of the prepared fibers were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray Diffraction, differential scanning calorimeter, and single fiber strength tester. Based on the results obtained from fourier transform infrared spectroscopy and x-ray Diffraction, cotton fibers have been successfully incorporated into the structure of the hydrogel fibers. It was seen from the differential scanning calorimeter results that the incorporation of fibers in the structure even enhanced the thermal stability of the fiber and is viable to be implanted in the human body. Cotton reinforcement in alginate hydrogel fibers increases the modulus up to 56.45 MPa providing significant stiffness and toughness for the hydrogel composite fiber. The tenacity of the fibers increased by increasing the concentration of alginate from 2.1 cN/Tex (1% w/v) to 8.16 cN/Tex (1.5% w/v). Fiber strength increased by 26.75% and water absorbance increased by 120% by incorporating (10% w/w) cotton fibers into the fibrous structure. It was concluded that these cotton-reinforced alginate hydrogel fibers have improved mechanical properties and liquid absorption properties suitable for use in various biomedical applications.

Preparation, physicochemical, and retinal anti-angiogenic evaluation of poloxamer hydrogel containing dexamethasone/avastin-loaded chitosan-N-acetyl-L-cysteine nanoparticles

This study was meant to describe a Poloxamer hydrogel combining Chitosan-N-acetyl-L-cysteine (CNAC) nanoparticles to increase loading and sustained intravitreal administration of Avastin macromolecule. To increase the drug's efficacy and reduce the interfacial fluid pressure in a formulation, dexamethasone was used. To do so, CNAC was synthesized. Then, Avastin- loaded CNAC nanoparticles were prepared and optimized. The resulting hydrogel's sol-gel transition time and viscosity were determined using poloxamer and hydroxypropylmethylcellulose (HPMC). In vitro and in vivo investigations of Avastin-loaded CNAC nanoparticles and hydrogel comprising dexamethasone/Avastin-loaded CNAC nanoparticles were determined. In vitro, the drug release profile of optimized hydrogel containing Avastin-loaded CNAC nanoparticles was sustained and controlled over 256 h. The obtained results point to poloxamer/HPMC (18 %/0.5 %) as the best formulations for this hydrogel to develop a sol-gel transition. About 97 % of dexamethasone was released from the hydrogel within 18 h. In vivo results indicated that the optimized formulation compared with free Avastin could improve Diabetic retinopathy (DR). Consequently, we infer that this new drug delivery method may enhance Avastin intravitreal administration, lowering the frequency, danger, and expense of heavy intravitreal injections and resulting in improved treatment of posterior eye segment neovascularization and concomitant vitreoretinal disorders.

Bacterial Cellulose as a Versatile Biomaterial for Wound Dressing Application

Chronic ulcers are among the main causes of morbidity and mortality due to the high probability of infection and sepsis and therefore exert a significant impact on public health resources. Numerous types of dressings are used for the treatment of skin ulcers-each with different advantages and disadvantages. Bacterial cellulose (BC) has received enormous interest in the cosmetic, pharmaceutical, and medical fields due to its biological, physical, and mechanical characteristics, which enable the creation of polymer composites and blends with broad applications. In the medical field, BC was at first used in wound dressings, tissue regeneration, and artificial blood vessels. This material is suitable for treating various skin diseases due its considerable fluid retention and medication loading properties. BC membranes are used as a temporary dressing for skin treatments due to their excellent fit to the body, reduction in pain, and acceleration of epithelial regeneration. BC-based composites and blends have been evaluated and synthesized both in vitro and in vivo to create an ideal microenvironment for wound healing. This review describes different methods of producing and handling BC for use in the medical field and highlights the qualities of BC in detail with emphasis on biomedical reports that demonstrate its utility. Moreover, it gives an account of biomedical applications, especially for tissue engineering and wound dressing materials reported until date. This review also includes patents of BC applied as a wound dressing material.

Biomimetic Hydrogels in the Study of Cancer Mechanobiology: Overview, Biomedical Applications, and Future Perspectives

Hydrogels are biocompatible polymers that are tunable to the system under study, allowing them to be widely used in medicine, bioprinting, tissue engineering, and biomechanics. Hydrogels are used to mimic the three-dimensional microenvironment of tissues, which is essential to understanding cell–cell interactions and intracellular signaling pathways (e.g., proliferation, apoptosis, growth, and survival). Emerging evidence suggests that the malignant properties of cancer cells depend on mechanical cues that arise from changes in their microenvironment. These mechanobiological cues include stiffness, shear stress, and pressure, and have an impact on cancer proliferation and invasion. The hydrogels can be tuned to simulate these mechanobiological tissue properties. Although interest in and research on the biomedical applications of hydrogels has increased in the past 25 years, there is still much to learn about the development of biomimetic hydrogels and their potential applications in biomedical and clinical settings. This review highlights the application of hydrogels in developing pre-clinical cancer models and their potential for translation to human disease with a focus on reviewing the utility of such models in studying glioblastoma progression.

Additive Manufacturing of Biomaterials-Design Principles and Their Implementation

Additive manufacturing (AM, also known as 3D printing) is an advanced manufacturing technique that has enabled progress in the design and fabrication of customised or patient-specific (meta-)biomaterials and biomedical devices (e.g., implants, prosthetics, and orthotics) with complex internal microstructures and tuneable properties. In the past few decades, several design guidelines have been proposed for creating porous lattice structures, particularly for biomedical applications. Meanwhile, the capabilities of AM to fabricate a wide range of biomaterials, including metals and their alloys, polymers, and ceramics, have been exploited, offering unprecedented benefits to medical professionals and patients alike. In this review article, we provide an overview of the design principles that have been developed and used for the AM of biomaterials as well as those dealing with three major categories of biomaterials, i.e., metals (and their alloys), polymers, and ceramics. The design strategies can be categorised as: library-based design, topology optimisation, bio-inspired design, and meta-biomaterials. Recent developments related to the biomedical applications and fabrication methods of AM aimed at enhancing the quality of final 3D-printed biomaterials and improving their physical, mechanical, and biological characteristics are also highlighted. Finally, examples of 3D-printed biomaterials with tuned properties and functionalities are presented.

Influence of extracellular cues of hydrogel biomaterials on stem cell fate

Tissue engineering is a multidisciplinary field that focuses on creating functional tissue through the combination of biomimetic scaffolds, a cell source, and biochemical/physiochemical cues. Stem cells are often used as the cell source due to their multipotent properties and autologous sourcing; however, the combination of physical and chemical cues that regulate their behavior creates challenges in reproducibly directing them to a specific fate. Hydrogel biomaterials are widely explored as tissue scaffolds due to their innate biomimetic properties and tailorability. For these constructs to be successful, properties such as surface chemistry and spatial configuration, stiffness, and degradability of the biomaterial used for the scaffold framework should be analogous to the natural environment of the tissue they are repairing/replacing. This is imperative, as cues from the surrounding extracellular matrix (ECM) influence stem cell behavior and direct cell differentiation to a specific lineage. Hydrogels offer great promise as tools to control stem cell fate, as researchers can modulate the degradation rates, mechanical properties, swelling behavior, and chemical properties of the biomaterial scaffold to mimic the instructive cues of the native ECM. Discussion of the advantages and challenges of utilizing hydrogel biomaterials as the basis of tissue scaffolds is reviewed herein, as well as specific examples of hydrogels in tissue engineering and advances in hydrogel research to achieve desired cell phenotypes.