An injectable and self-healing cellulose nanofiber-reinforced alginate hydrogel for bone repair

Crosslinking of gelatin Schiff base hydrogels with different structural dialdehyde polysaccharides as novel crosslinkers: Characterization and performance comparison

Few studies have been conducted on the relationship between the crosslinking ability of dialdehyde polysaccharides (DPs) with different structures and the structure and properties of hydrogels. Herein, the effects of dialdehyde sodium alginate (DSA), dialdehyde guar gum (DGG), and dialdehyde dextran (DDE) as crosslinking agents for gelatin (GE)-based hydrogels were comparatively studied. First, the structure and aldehyde content of DPs were evaluated. Subsequently, the structure, crosslinking degree, and physicochemical properties of GE/DP hydrogels were characterized. Compared with pure GE hydrogels, GE/DP hydrogels had higher thermal stability and mechanical properties. Moreover, the aldehyde content of DPs was ordered as follows: DSA < DGG < DDE. The higher crosslinking degree of the hydrogels formed by DPs with a higher aldehyde content resulted in smaller hydrogel pores, higher mechanical strength, and a lower equilibrium swelling rate. These observations provide a theoretical basis for selecting crosslinking candidates for hydrogel-specific applications.

Ultra-strong and tough cellulose-based conductive hydrogels via orientation inspired by noodles pre-stretching

Due to the unsatisfactory mechanical properties of natural polymer-based conductive hydrogels, their applications are limited. Shaanxi Biangbiang noodles can be toughened by applying external mechanical forces through stretching and beating movements; this process provides inspiration for the preparation of high-strength hydrogels. In this paper, we propose a strategy for the preparation of ultrastrong and ultratough conductive hydrogels by directional prestretching and solvent exchange. Neatly arranged fiber bundles containing many intermolecular hydrogen bonds and metal ion coordination bonds are successfully constructed inside the prepared hydrogels. The hydrogel has exceptional mechanical properties, with a fracture stress exceeding 50 MPa, fracture strain approaching 105 %, fracture toughness exceeding 30 MJ m-3, and high conductivity reaching 11.738 ± 0.06 mS m-1. Impressively, the hydrogel can maintain its high mechanical properties after being frozen at an ultralow temperature of -80 °C for 7 days. Compared with other tough hydrogels, natural tendons and synthetic rubbers, the hydrogel exhibits excellent mechanical properties. The cellulose-based conductive hydrogel prepared in this study can be applied to robotic soft tissues (such as the Achilles tendon) that require high strength and are operated in extreme environments.

Recent advances in nanocellulose based hydrogels: Preparation strategy, typical properties and food application

Nanocellulose has been favored as one of the most promising sustainable nanomaterials, due to its competitive advantages and superior performances such as hydrophilicity, renewability, biodegradability, biocompatibility, tunable surface features, excellent mechanical strength, and high specific surface area. Based on the above properties of nanocellulose and the advantages of hydrogels such as high water absorption, adsorption, porosity and structural adjustability, nanocellulose based hydrogels integrating the benefits of both have attracted extensive attention as promising materials in various fields. In this review, the main fabrication strategies of nanocellulose based hydrogels are initially discussed in terms of different crosslinking methods. Then, the typical properties of nanocellulose based hydrogels are comprehensively summarized, including porous structure, swelling ability, adsorption, mechanical, self-healing, smart response performances. Especially, relying on these properties, the general application of nanocellulose based hydrogels in food field is also discussed, mainly including food packaging, food detection, nutrient embedding delivery, 3D food printing, and enzyme immobilization. Finally, the safety of nanocellulose based hydrogel is summarized, and the current challenges and future perspectives of nanocellulose based hydrogels are put forward.

Characterization Methods to Determine Interpenetrating Polymer Network (IPN) in Hydrogels

Significant developments have been achieved with the invention of hydrogels. They are effective in many fields such as wastewater treatment, food, agriculture, pharmaceutical applications, and drug delivery. Although hydrogels have been used successfully in these areas, there is a need to make them better for future applications. Interpenetrating polymer networks (IPNs) can be created to make hydrogels more adjustable and suitable for a specific purpose. IPN formation is an innovative approach for polymeric systems. It brings two or more polymer networks together with entanglements. The properties of IPNs are controlled by its chemistry, crosslinking density, and morphology. Therefore, it is necessary to understand characterization methods in order to detect the formation of IPN structure and to develop the properties of hydrogels. In recent studies, IPN structure in hydrogels has been determined via chemical, physical, and mechanical methods such as Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), and rheology methods. In this paper, these characterization methods will be explained, recent studies will be scrutinized, and the effectiveness of these methods to confirm IPN formation will be evaluated.

Propelling Minimally Invasive Tissue Regeneration With Next-Era Injectable Pre-Formed Scaffolds

The growing aging population, with its associated chronic diseases, underscores the urgency for effective tissue regeneration strategies. Biomaterials play a pivotal role in the realm of tissue reconstruction and regeneration, with a distinct shift toward minimally invasive (MI) treatments. This transition, fueled by engineered biomaterials, steers away from invasive surgical procedures to embrace approaches offering reduced trauma, accelerated recovery, and cost-effectiveness. In the realm of MI tissue repair and cargo delivery, various techniques are explored. While in situ polymerization is prominent, it is not without its challenges. This narrative review explores diverse biomaterials, fabrication methods, and biofunctionalization for injectable pre-formed scaffolds, focusing on their unique advantages. The injectable pre-formed scaffolds, exhibiting compressibility, controlled injection, and maintained mechanical integrity, emerge as promising alternative solutions to in situ polymerization challenges. The conclusion of this review emphasizes the importance of interdisciplinary design facilitated by synergizing fields of materials science, advanced 3D biomanufacturing, mechanobiological studies, and innovative approaches for effective MI tissue regeneration.

Multifaceted Hydrogel Scaffolds: Bridging the Gap between Biomedical Needs and Environmental Sustainability

Hydrogels are dynamically evolving 3D networks composed of hydrophilic polymer scaffolds with significant applications in the healthcare and environmental sectors. Notably, protein-based hydrogels mimic the extracellular matrix, promoting cell adhesion. Further enhancing cell proliferation within these scaffolds are matrix-metalloproteinase-triggered amino acid motifs. Integration of cell-friendly modules like peptides and proteins expands hydrogel functionality. These exceptional properties position hydrogels for diverse applications, including biomedicine, biosensors, environmental remediation, and the food industry. Despite significant progress, there is ongoing research to optimize hydrogels for biomedical and environmental applications further. Engineering novel hydrogels with favorable characteristics is crucial for regulating tissue architecture and facilitating ecological remediation. This review explores the synthesis, physicochemical properties, and biological implications of various hydrogel types and their extensive applications in biomedicine and environmental sectors. It elaborates on their potential applications, bridging the gap between advancements in the healthcare sector and solutions for environmental issues.

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

Biophysical stimulation for bone regeneration using a chitosan/barium titanate ferroelectric composite

Herein we report the synthesis of a ferroelectric composed of chitosan (C)/barium titanate (BT) nanoparticles (NPs) with enhanced biocompatibility, non-toxicity, and piezoelectric behavior that can be advantageously used in biomedical applications. FTIR and SEM measurements were performed to assess the mechanism of interaction between the C matrix and BT NPs and their correlation with the biological responses. The dielectric measurements of the as-prepared composites reveal that incorporation of 50% BT NPs in the chitosan matrix leads to a steady increase of the dielectric constant as compared with neat chitosan films. The ferroelectric behavior of the sample was confirmed by the values of the loss factor (0.21-0.003) in the analyzed frequency range (10-1-106 Hz). This behavior suggests that ferroelectric C/BT nanocomposites can act as an active material that promotes accelerated bone regeneration.

Transparent, super stretchable, freezing-tolerant, self-healing ionic conductive cellulose based eutectogel for multi-functional sensors

In this study, we propose a non - toxic and low-cost fabrication of cellulose-based eutectogel through the ZnCl2/H2O/H3PO4 deep eutectic solvent (DES) to dissolve cellulose followed by free-radical polymerization of acrylamide. Particularly, the introduction of cellulose enhances the mechanical properties of eutectogels while eliminating the environmental concerns of the traditional nanocellulose fabrication process. Owing to the dynamic transfer of ions in the eutectogel network, the prepared eutectogels exhibit adjustable conductivity (0.9- 1.37 Sm-1, 15 °C) and stretching sensitivity (Gauge factor = 5.4). The resulting DES - cellulose-based eutectogels (DCEs) exhibited ultra stretchability (4086 %), high toughness (261.3 MJ/m3), excellent ionic conductivity (1.64 Sm-1, 20 °C), high transparency (>85 %), outstanding antifreezing performance (<-80 °C), and other comprehensive characteristics. The DCEs had been proven to have multiple sensitivities to external stimuli, like temperature, strain, and pressure. As a result, the DCEs can be assembled into multifunctional sensors. Moreover, this work also demonstrated the satisfactory performance of DCEs in flexible electroluminescent devices. The low cost and high efficiency made the preparation method of this experiment an efficient strategy for developing high-performance cellulose-based eutectogels, which would greatly promote the application of such materials in areas such as artificial skin for soft robots and other wearable devices.

Tough, self-healing and injectable dynamic nanocomposite hydrogel based on gelatin and sodium alginate

Biomacromolecules based injectable and self-healing hydrogels possessing high mechanical properties have widespread potential in biomedical field. However, dynamic features are usually inversely proportional to toughness. It is challenging to simultaneously endow these properties to the dynamic hydrogels. Here, we fabricated an injectable nanocomposite hydrogel (CS-NPs@OSA-l-Gtn) stimultaneously possessing excellent autonomous self-healing performance and high mechanical strength by doping chitosan nanoparticles (CS-NPs) into dynamic polymer networks of oxidized sodium alginate (OSA) and gelatin (Gtn) in the presence of borax. The synergistic effect of the multiple reversible interactions combining dynamic covalent bonds (i.e., imine bond and borate ester bond) and noncovalent interactions (i.e., electrostatic interaction and hydrogen bond) provide effective energy dissipation to endure high fatigue resistance and cyclic loading. The dynamic hydrogel exhibited excellent mechanical properties like maximum 2.43 MPa compressive strength, 493.91 % fracture strain, and 89.54 kJ/m3 toughness. Moreover, the integrated hydrogel after injection and self-healing could withstand 150 successive compressive cycles. Besides, the bovine serum albumin embedded in CS-NPs could be sustainably released from the nanocomposite hydrogel for 12 days. This study proposes a novel strategy to synthesize an injectable and self-healing hydrogel combined with excellent mechanical properties for designing high-strength natural carriers with sustained protein delivery.

Cu-MSNs and ZnO nanoparticles incorporated poly(ethylene glycol) diacrylate/sodium alginate double network hydrogel for simultaneous enhancement of osteogenic differentiation

In this study, a double network (DN) hydrogel was synthesized using poly(ethylene glycol) diacrylate (PEGDA) and sodium alginate (SA), incorporating copper-doped mesoporous silica nanospheres (Cu-MSNs) and zinc oxide nanoparticles (ZnO NPs). The blending of PEGDA and SA (PS) facilitates the double network and improves the less porous microstructure of pure PEGDA hydrogel. Furthermore, the incorporation of ZnO NPs and Cu-MSNs into the hydrogel network (PS@ZnO/Cu-MSNs) improved the mechanical properties of the hydrogel (Compressive strength = ⁓153 kPa and Young's modulus = ⁓ 1.66 kPa) when compared to PS hydrogel alone (Compressive strength = ⁓ 103 kPa and Young's modulus = ⁓ 0.95 kPa). In addition, the PS@ZnO/Cu-MSNs composite hydrogel showed antibacterial activities against Staphylococcus aureus and Escherichia coli. Importantly, the PS@ZnO/Cu-MSNs hydrogel demonstrated excellent biocompatibility, enhanced MC3T3-E1 cell adhesion, proliferation, and significant early-stage osteoblastic differentiation, as evidenced by increased alkaline phosphatase (ALP), and improved calcium mineralization, as evidenced by increased alizarin red staining (ARS) activities. These findings point to the possible use of the PS@ZnO/Cu-MSNs composite hydrogel in bone tissue regeneration.

Methacrylated gelatin and platelet-rich plasma based hydrogels promote regeneration of critical-sized bone defects

Physiological repair of large-sized bone defects requires instructive scaffolds with appropriate mechanical properties, biocompatibility, biodegradability, vasculogenic ability and osteo-inductivity. The objective of this study was to fabricate in situ injectable hydrogels using platelet-rich plasma (PRP)-loaded gelatin methacrylate (GM) and employ them for the regeneration of large-sized bone defects. We performed various biological assays as well as assessed the mechanical properties of GM@PRP hydrogels alongside evaluating the release kinetics of growth factors (GFs) from hydrogels. The GM@PRP hydrogels manifested sufficient mechanical properties to support the filling of the tissue defects. For biofunction assay, the GM@PRP hydrogels significantly improved cell migration and angiogenesis. Especially, transcriptome RNA sequencing of human umbilical vein endothelial cells and bone marrow-derived stem cells were performed to delineate vascularization and biomineralization abilities of GM@PRP hydrogels. The GM@PRP hydrogels were subcutaneously implanted in rats for up to 4 weeks for preliminary biocompatibility followed by their transplantation into a tibial defect model for up to 8 weeks in rats. Tibial defects treated with GM@PRP hydrogels manifested significant bone regeneration as well as angiogenesis, biomineralization, and collagen deposition. Based on the biocompatibility and biological function of GM@PRP hydrogels, a new strategy is provided for the regenerative repair of large-size bone defects.

Cellulose-alginate hydrogels and their nanocomposites for water remediation and biomedical applications

In the last decade, both cellulose and alginate polysaccharides have been extensively utilized for the synthesis of biocompatible hydrogels because of their alluring characteristics like low cost, biodegradability, hydrophilicity, biodegradability, ease of availability and non-toxicity. The presence of abundant hydrophilic functional groups (like carboxyl and hydroxyl) on the surface of cellulose and alginate or their derivatives makes these materials promising candidates for the preparation of hydrogels with appealing structures and characteristics, leading to growing research in water treatment and biomedical fields. These two polysaccharides are typically blended together to improve hydrogels' desired qualities (mechanical strength, adsorption properties, cellulose/alginate yield). So, keeping in view their extensive applicability, in the present review article, recent advances in the development of cellulose/nanocellulose-alginate-based hydrogels and their relevance in water treatment (adsorption of dyes, heavy metals, etc.) and biomedical field (wound healing, tissue engineering, drug delivery) has been reviewed. Further, impact of other inorganic/organic additives in cellulose/nanocellulose-alginate-based hydrogels properties like contaminants adsorption, drug delivery, tissue engineering, etc., has also been studied. Moreover, the current difficulties and future prospects of nanocellulose-alginate-based hydrogels regarding their water purification and biomedical applications are also discussed at the end.

The current status and development trend of hydrogel application in spinal surgery

Spinal diseases often result in compromised mobility and diminished quality of life due to the intricate anatomy surrounding the nervous system. Medication and surgical interventions remain the primary treatment methods for spinal conditions. However, currently available medications have limited efficacy in treating spinal surgical diseases and cannot achieve a complete cure. Furthermore, surgical intervention frequently results in inevitable alterations and impairments to the initial anatomical integrity of the spinal structure, accompanied by the consequential loss of certain physiological functionalities. Changes in spine surgery treatment concepts and modalities in the last decade have led to a deepening of minimally invasive treatment, with treatment strategies focusing more on repairing and reconstructing the patient's spine and preserving physiological functions. Therefore, developing novel and more efficient treatment strategies to reduce spinal lesions and iatrogenic injuries is essential. In recent years, significant advancements in biomedical research have led to the discovery that hydrogels possess excellent biocompatibility, biodegradability, and adjustable mechanical properties. The application of hydrogel-based biotechnology in spinal surgery has demonstrated remarkable therapeutic potential. This review presents the therapeutic strategies for spinal diseases based on hydrogel tissue engineering technology.

Triple physical cross-linking cellulose nanofibers-based poly(ionic liquid) hydrogel as wearable multifunctional sensors

A novel triple physical cross-linking poly(ionic liquid) hydrogel, composed of poly(acrylamide-co-dodecyl methacrylate-co-1-vinyl-3-methyluracil-imidazolium chloride)/cellulose nanofibers-Ca2+ (PADV/CNFs-Ca2+), was synthesized through micellar-copolymerization followed by a solvent-soaked procedure. The synergistic interactions in polymer network (i.e. the hydrophobic association of dodecyl methacrylate moiety in surfactant micelles, the hydrogen bondings between imidazolium monomer segments and other monomer segments in polymers, and the ionic coordination between Ca2+ and -COO- on cellulose nanofibers surface) endowed the hydrogel with excellent mechanical properties, including high strength (754 kPa of tensile strength and 1905 kPa of compressive strength), outstanding stretchability (1963 %), elastic modulus (56.5 kPa) and remarkable mechanical durability (200 cycles with 500 % deformations and 100 cycles at 50 % compression strain). Besides, this hydrogel exhibited other advantages, such as satisfied conductivity (28.7 mS/cm), high strain/pressure/temperature-sensitive behavior, precise and stable signal transmission, varying degrees of antibacterial activity, and biocompatibility. Owing to the exceptional comprehensive performance, the hydrogel was then assembled as a multifunctional sensor to monitor the joint motion, vocal cord vibration, tactile sensation and body temperature with remarkable sensitivity in real time. This work offered a new strategy for the fabrication of durable, biocompatible, antibacterial and conductive materials for wearable multifunctional electronic devices.

Recent advances in composite hydrogels: synthesis, classification, and application in the treatment of bone defects

Bone defects are often difficult to treat due to their complexity and specificity, and therefore pose a serious threat to human life and health. Currently, the clinical treatment of bone defects is mainly surgical. However, this treatment is often more harmful to patients and there is a potential risk of rejection and infection. Hydrogels have a unique three-dimensional structure that can accommodate a variety of materials, including particles, polymers and small molecules, making them ideal for treating bone defects. Therefore, emerging composite hydrogels are considered one of the most promising candidates for the treatment of bone defects. This review describes the use of different types of composite hydrogel in the treatment of bone defects. We present the basic concepts of hydrogels, different preparation techniques (including chemical and physical crosslinking), and the clinical requirements for hydrogels used to treat bone defects. In addition, a review of numerous promising designs of different types of hydrogel doped with different materials (e.g., nanoparticles, polymers, carbon materials, drugs, and active factors) is also highlighted. Finally, the current challenges and prospects of composite hydrogels for the treatment of bone defects are presented. This review will stimulate research efforts in this field and promote the application of new methods and innovative ideas in the clinical field of composite hydrogels.

Tannic acid-coated cellulose nanocrystal-reinforced transparent multifunctional hydrogels with UV-filtering for wearable flexible sensors

Ionically conductive hydrogels are an ideal alternative material for applications in wearable flexible sensors to monitor human health. However, producing hydrogels with both high sensitivity and excellent versatility is difficult, and their transparency and UV-blocking properties are significantly limited. Here, with mussel- and gecko-inspired biomimicry, all-biomass-based hydrogels (OGTCGs) with self-adhesive, self-healing, transparent, UV-filtering, frost-resistant, environmentally stable, antibacterial, and biocompatible properties were designed and constructed via a simple one-step approach with a water/glycerol system and borax added without any crosslinker using synergistic dynamic covalent and noncovalent chemistry. The transparency of the OGTCG hydrogel reached 81.06 %, while the added tannic acid-coated cellulose nanocrystal (TA@CNC) induced a UV-blocking effect. The OGTCG hydrogel exhibited a high toughness (218.67 kPa) and modulus (100.32 kPa) reinforced by TA@CNC. The OGTCG hydrogel showed good self-healing abilities with an efficiency of over 90 % after 6 h. In a binary solvent system, the OGTCG hydrogel had environmental stability, as illustrated by density functional theory (DFT), greatly broadening its application range. Moreover, it had an electrical conductivity of 2.3 mS cm-1 and a sensitivity of 3.97. Therefore, with its rapid response and real-time monitoring capabilities, the OGTCG hydrogel shows great potential for applications in monitoring human health.

Recent advances in biopolymer-based hydrogels and their potential biomedical applications

Hydrogels are three-dimensional networks of polymer chains containing large amounts of water in their structure. Hydrogels have received significant attention in biomedical applications owing to their attractive physicochemical properties, including flexibility, softness, biodegradability, and biocompatibility. Different natural and synthetic polymers have been intensely explored in developing hydrogels for the desired applications. Biopolymers-based hydrogels have advantages over synthetic polymers regarding improved cellular activity and weak immune response. These properties can be further improved by grafting with other polymers or adding nanomaterials, and they structurally mimic the living tissue environments, which opens their broad applicability. The hydrogels can be physically or chemically cross-linked depending on the structure. The use of different biopolymers-based hydrogels in biomedical applications has been reviewed and discussed earlier. However, no report is still available to comprehensively introduce the synthesis, advantages, disadvantages, and biomedical applications of biopolymers-based hydrogels from the material point of view. Herein, we systematically overview different synthesis methods of hydrogels and provide a holistic approach to biopolymers-based hydrogels for biomedical applications, especially in bone regeneration, wound healing, drug delivery, bioimaging, and therapy. The current challenges and prospects of biopolymers-based hydrogels are highlighted rationally, giving an insight into the progress of these hydrogels and their practical applications.

Cellulosic Textiles-An Appealing Trend for Different Pharmaceutical Applications

Cellulose, the most abundant biopolymer in nature, is derived from various sources. The production of pharmaceutical textiles based on cellulose represents a growing sector. In medicated textiles, textile and pharmaceutical sciences are integrated to develop new healthcare approaches aiming to improve patient compliance. Through the possibility of cellulose functionalization, pharmaceutical textiles can broaden the applications of cellulose in the biomedical field. This narrative review aims to illustrate both the methods of extraction and preparation of cellulose fibers, with a particular focus on nanocellulose, and diverse pharmaceutical applications like tissue restoration and antimicrobial, antiviral, and wound healing applications. Additionally, the merging between fabricated cellulosic textiles with drugs, metal nanoparticles, and plant-derived and synthetic materials are also illustrated. Moreover, new emerging technologies and the use of smart medicated textiles (3D and 4D cellulosic textiles) are not far from those within the review scope. In each section, the review outlines some of the limitations in the use of cellulose textiles, indicating scientific research that provides significant contributions to overcome them. This review also points out the faced challenges and possible solutions in a trial to present an overview on all issues related to the use of cellulose for the production of pharmaceutical textiles.

Emerging Technology of Nanofiber-Composite Hydrogels for Biomedical Applications

Hydrogels and nanofibers have been firmly established as go-to materials for various biomedical applications. They have been mostly utilized separately, rarely together, because of their distinctive attributes and shortcomings. However, the potential benefits of integrating nanofibers with hydrogels to synergistically combine their functionalities while attenuating their drawbacks are increasingly recognized. Compared to other nanocomposite materials, incorporating nanofibers into hydrogel has the distinct advantage of emulating the hierarchical structure of natural extracellular environment needed for cell and tissue culture. The most important technological aspect of developing "nanofiber-composite hydrogel" is generating nanofibers made of various polymers that are cross-linked and short enough to maintain stable dispersion in hydrated environment. In this review, recent research efforts to develop nanofiber-composite hydrogels are presented, with added emphasis on nanofiber processing techniques. Several notable examples of implementing nanofiber-composite hydrogels for biomedical applications are also introduced.

Bioinspired self-healing injectable nanocomposite hydrogels based on oxidized dextran and gelatin for growth-factor-free bone regeneration

Hydrogels with great biocompatibility, biodegradability, and mechanical properties, combined with osteoconductivity, osteoinductivity, and osteointegration as biomaterials for bone regeneration without adding exogenous growth factors and cells are highly appealing but challenging. Here, inspired by organic-inorganic analogues of natural bone tissue and the adhesion chemistry of mussels, nanocomposite hydrogels with self-healing, injectable, adhesive, antioxidant, and osteoinductive properties (termed GO-PHA-CPs) were constructed by Schiff base cross-linking between dopamine-modified gelatin (Gel-DA) and oxidized dextran (ODex). Furthermore, the hydrogel network was enhanced by the introduction of polydopamine-functionalized nanohydroxyapatite (PHA) by improving the interfacial compatibility between the rigid inorganic particles and the flexible hydrogel matrix. Bioactive cod peptides (CPs) with osteogenic activity from Atlantic cod were further incorporated into the nanocomposite hydrogel. As a result, the multicomponent nanocomposite hydrogel favored the adhesion and spreading of MC3T3-E1 cells. The increased ALP activity suggested that GO-PHA-CPs hydrogels contributed to the osteogenic differentiation of MC3T3-E1 cells. The suitability of GO-PHA-CPs hydrogels for enhancing bone regeneration in vivo was further confirmed by the rat femoral defect model. Our results indicate that the multifunctional GO-PHA-CPs nanocomposite hydrogels without growth factors are a promising and effective candidate material for bone regeneration.

Development of Poly(vinyl alcohol) Grafted Glycidyl Methacrylate/Cellulose Nanofiber Injectable Hydrogels for Meniscus Tissue Engineering

This study aimed to develop poly (vinyl alcohol) grafted glycidyl methacrylate/cellulose nanofiber (PVA-g-GMA/CNF) injectable hydrogels for meniscus tissue engineering. PVA-g-GMA is an interesting polymer for preparing cross-linking injectable hydrogels with UV radiation, but it has poor mechanical properties and low cell proliferation. In this study, CNF as a reinforcing agent was selected to improve mechanical properties and cell proliferation in PVA-g-GMA injectable hydro-gels. The effect of CNF concentration on hydrogel properties was investigated. Both PVA-g-GMA and PVA-g-GMA hydrogels incorporating 0.3, 0.5, and 0.7% (w/v) CNF can be formed by UV curing at a wavelength of 365 nm, 6 mW/cm2 for 10 min. All hydrogels showed substantial microporosity with interconnected tunnels, and a pore size diameter range of 3-68 µm. In addition, all hydrogels also showed high physicochemical properties, a gel fraction of 81-82%, porosity of 83-94%, water content of 73-87%, and water swelling of 272-652%. The water content and swelling of hydrogels were increased when CNF concentration increased. It is worth noting that the reduction of porosity in the hydrogels occurred with increasing CNF concentration. With increasing CNF concentration from 0.3% to 0.7% (w/v), the compressive strength and compressive modulus of the hydrogels significantly increased from 23 kPa to 127 kPa and 27 kPa to 130 kPa, respectively. All of the hydrogels were seeded with human cartilage stem/progenitor cells (CSPCs) and cultured for 14 days. PVA-g-GMA hydrogels incorporating 0.5% and 0.7% (w/v) CNF demonstrated a higher cell proliferation rate than PVA-g-GMA and PVA-g-GMA hydrogels incorporating 0.3% (w/v) CNF, as confirmed by MTT assay. At optimum formulation, 10%PVA-g-GMA/0.7%CNF injectable hydrogel met tissue engineering requirements, which showed excellent properties and significantly promoted cell proliferation, and has a great potential for meniscus tissue engineering application.

Injectable multifunctional carboxymethyl chitosan/hyaluronic acid hydrogel for drug delivery systems

Injectable hydrogels with notable mechanical properties and self-healing ability are promising carriers for use as a drug delivery system. Here, adipic acid dihydrazide (ADH) and calcium ions (Ca2+) were introduced into quaternary ammonium carboxymethyl chitosan and aldehyde-modified hyaluronic acid hydrogels (QCS + OHA). The hydrogels were synthesized through the interaction of the Schiff bases (imine bonds, acylhydrazone bonds) and coordination bonds via a facile one-step approach. The gelation time (∼54 s) ensured excellent injectability. The QCS + OHA + ADH + Ca2+ hydrogel had notable mechanical properties (compressive stress up to 896.30 KPa), good self-healing ability (up to 94 %), good pH responsiveness, and excellent antibacterial properties. In addition, the QCS + OHA + ADH + Ca2+ hydrogel had a high drug loading capacity (121.3 mg/g) and sustained drug release behaviour (≥120 h). The results of cytotoxicity tests showed a high cell proliferation rate (up to 98 %) and good cytocompatibility. In summary, this work presents an injectable and self-healing pH-responsive hydrogel that can be used as a carrier for drug delivery systems.

Biomimetic Spun Silk Ionotronic Fibers for Intelligent Discrimination of Motions and Tactile Stimuli

Innovation in the ionotronics field has significantly accelerated the development of ultraflexible devices and machines. However, it is still challenging to develop efficient ionotronic-based fibers with necessary stretchability, resilience, and conductivity due to inherent conflict in producing spinning dopes with both high polymer and ion concentrations and low viscosities. Inspired by the liquid crystalline spinning of animal silk, this study circumvents the inherent tradeoff in other spinning methods by dry spinning a nematic silk microfibril dope solution. The liquid crystalline texture allows the spinning dope to flow through the spinneret and form free-standing fibers under minimal external forces. The resultant silk-sourced ionotronic fibers (SSIFs) are highly stretchable, tough, resilient, and fatigue-resistant. These mechanical advantages ensure a rapid and recoverable electromechanical response of SSIFs to kinematic deformations. Further, the incorporation of SSIFs into core-shell triboelectric nanogenerator fibers provides outstanding stable and sensitive triboelectric response to precisely and sensitively perceive small pressures. Moreover, by implementing a combination of machine learning and Internet of Things techniques, the SSIFs can sort objects made of different materials. With these structural, processing, performance, and functional merits, the SSIFs prepared herein are expected to be applied in human-machine interfaces.

Electrospun Fibrous Silica for Bone Tissue Engineering Applications

The production of highly porous and three-dimensional (3D) scaffolds with biomimicking abilities has gained extensive attention in recent years for tissue engineering (TE) applications. Considering the attractive and versatile biomedical functionality of silica (SiO₂) nanomaterials, we propose herein the development and validation of SiO₂-based 3D scaffolds for TE. This is the first report on the development of fibrous silica architectures, using tetraethyl orthosilicate (TEOS) and polyvinyl alcohol (PVA) during the self-assembly electrospinning (ES) processing (a layer of flat fibers must first be created in self-assembly electrospinning before fiber stacks can develop on the fiber mat). The compositional and microstructural characteristics of obtained fibrous materials were evaluated by complementary techniques, in both the pre-ES aging period and post-ES calcination. Then, in vivo evaluation confirmed their possible use as bioactive scaffolds in bone TE.

One-pot and one-step preparation of "living" cellulose nanofiber hydrogel with active double-bond via chemical vapor deposition

Due to the existence of water, it is still a challenge to conduct chemical modification on cellulose nanofiber (CNF) hydrogels with active double bonds. A simple one-pot and one-step method for constructing "living" CNF hydrogel with double bond was created at room temperature. The chemical vapor deposition (CVD) of methacryloyl chloride (MACl) was used to introduce physical-trapped, chemical-anchored and functional double bonds into TEMPO-oxidized cellulose nanofiber (TOCN) hydrogels. TOCN hydrogel could be fabricated within just 0.5 h, the minimum dosage of MACl could be reduced to 3.22 mg/g (MACl/TOCN hydrogel). Furthermore, the CVD methods showed high efficiency for mass production and recyclability. Moreover, the chemical "living" reactivity of the introduced double bonds were verified by the freezing and UV crosslinking, radical polymerization and thiol-ene click reaction. Compared with pure TOCN hydrogel, the obtained functionalized TOCN hydrogel exhibited remarkable improvements in mechanical properties, with enhancements of 12.34 times and 2.04 times, as well as an increase in hydrophobicity by 2.14 times and a fluorescence performance improvement of 2.93 times.

Nano-crosslinked dynamic hydrogels for biomedical applications

Hydrogels resemble natural extracellular matrices and have been widely studied for biomedical applications. Nano-crosslinked dynamic hydrogels combine the injectability and self-healing property of dynamic hydrogels with the versatility of nanomaterials and exhibit unique advantages. The incorporation of nanomaterials as crosslinkers can improve the mechanical properties (strength, injectability, and shear-thinning properties) of hydrogels by reinforcing the skeleton and endowing them with multifunctionality. Nano-crosslinked functional hydrogels that can respond to external stimuli (such as pH, heat, light, and electromagnetic stimuli) and have photothermal properties, antimicrobial properties, stone regeneration abilities, or tissue repair abilities have been constructed through reversible covalent crosslinking strategies and physical crosslinking strategies. The possible cytotoxicity of the incorporated nanomaterials can be reduced. Nanomaterial hydrogels show excellent biocompatibility and can facilitate cell proliferation and differentiation for biomedical applications. This review introduces different nano-crosslinked dynamic hydrogels in the medical field, from fabrication to application. In this review, nanomaterials for dynamic hydrogel fabrication, such as metals and metallic oxides, nanoclays, carbon-based nanomaterials, black phosphorus (BP), polymers, and liposomes, are discussed. We also introduce the dynamic crosslinking method commonly used for nanodynamic hydrogels. Finally, the medical applications of nano-crosslinked hydrogels are presented. We hope that this summary will help researchers in the related research fields quickly understand nano-crosslinked dynamic hydrogels to develop more preparation strategies and promote their development and application.

Lyophilized Platelet-Rich Fibrin Exudate-Loaded Carboxymethyl Chitosan/GelMA Hydrogel for Efficient Bone Defect Repair

Platelet-rich fibrin (PRF) is an autologous growth factor carrier that promotes bone tissue regeneration, but its effectiveness is restrained by poor storage capabilities, uncontrollable concentration of growth factors, unstable shape, etc. Herein, we developed a photocrosslinkable composite hydrogel by incorporating lyophilized PRF exudate (LPRFe) into the carboxymethyl chitosan methacryloyl (CMCSMA)/gelatin methacryloyl (GelMA) hydrogel to effectively solve the dilemma of PRF. The hydrogel possessed suitable physical properties and sustainable release ability of growth factors in LPRFe. The LPRFe-loaded hydrogel could improve the adhesion, proliferation, migration, and osteogenic differentiation of rat bone mesenchymal stem cells (BMSCs). Furthermore, the animal experiments demonstrated that the hydrogel possessed excellent biocompatibility and biodegradability, and the introduction of LPRFe in the hydrogel can effectively accelerate the bone healing process. Conclusively, the combination of LPRFe with CMCSMA/GelMA hydrogel may be a promising therapeutic approach for bone defects.

Reinforcement of Injectable Hydrogel for Meniscus Tissue Engineering by Using Cellulose Nanofiber from Cassava Pulp

Injectable hydrogels can be applied to treat damaged meniscus in minimally invasive conditions. Generally, injectable hydrogels can be prepared from various polymers such as polycaprolactone (PCL) and poly (N-isopropylacrylamide) (PNIPAAm). Poly (ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer-diacrylate (PEO-PPO-PEO-DA) is an interesting polymer due to its biodegradability and can be prepared as water-insoluble injectable hydrogel after curing with UV light at low intensity. However, mechanical and cell adhesion properties are not optimal for these hydrogels. For the improved mechanical performance of the injectable hydrogel, cellulose nanofiber (CNF) extracted from cassava pulp was used as a reinforcing filler in this study. In addition, gelatin methacrylate (GelMA), the denatured form of collagen was used to enhance cell adhesion. PEO-PPO-PEO-DA/CNF/GelMA injectable hydrogels were prepared with 2-hydroxy-1-(4-(hydroxy ethoxy) phenyl)-2-methyl-1-propanone as a photoinitiator and then cured with UV light, 365 nm at 6 mW/cm². Physicochemical characteristics of the hydrogels and hydrogels with CNF were studied in detail including morphology characterization, pore size diameter, porosity, mechanical properties, water uptake, and swelling. In addition, cell viability was also studied. CNF-reinforced injectable hydrogels were successfully prepared after curing with UV light within 10 min with a thickness of 2 mm. CNF significantly improved the mechanical characteristics of injectable hydrogels. The incorporation of GelMA into the injectable hydrogels improved the viability of human cartilage stem/progenitor cells. At optimum formulation, 12%PEO-PPO-PEO-DA/0.5%CNF/3%GelMA injectable hydrogels significantly promoted cell viability (>80%) and also showed good physicochemical properties, which met tissue engineering requirements. In summary, this work shows that these novel injectable hydrogels have the potential for meniscus tissue engineering.

Advances of Mussel-Inspired Nanocomposite Hydrogels in Biomedical Applications

Hydrogels, with 3D hydrophilic polymer networks and excellent biocompatibilities, have emerged as promising biomaterial candidates to mimic the structure and properties of biological tissues. The incorporation of nanomaterials into a hydrogel matrix can tailor the functions of the nanocomposite hydrogels to meet the requirements for different biomedical applications. However, most nanomaterials show poor dispersion in water, which limits their integration into the hydrophilic hydrogel network. Mussel-inspired chemistry provides a mild and biocompatible approach in material surface engineering due to the high reactivity and universal adhesive property of catechol groups. In order to attract more attention to mussel-inspired nanocomposite hydrogels, and to promote the research work on mussel-inspired nanocomposite hydrogels, we have reviewed the recent advances in the preparation of mussel-inspired nanocomposite hydrogels using a variety of nanomaterials with different forms (nanoparticles, nanorods, nanofibers, nanosheets). We give an overview of each nanomaterial modified or hybridized by catechol or polyphenol groups based on mussel-inspired chemistry, and the performances of the nanocomposite hydrogel after the nanomaterial's incorporation. We also highlight the use of each nanocomposite hydrogel for various biomedical applications, including drug delivery, bioelectronics, wearable/implantable biosensors, tumor therapy, and tissue repair. Finally, the challenges and future research direction in designing mussel-inspired nanocomposite hydrogels are discussed.

Applications of Stimuli-Responsive Hydrogels in Bone and Cartilage Regeneration

Bone and cartilage regeneration is an area of tremendous interest and need in health care. Tissue engineering is a potential strategy for repairing and regenerating bone and cartilage defects. Hydrogels are among the most attractive biomaterials in bone and cartilage tissue engineering, mainly due to their moderate biocompatibility, hydrophilicity, and 3D network structure. Stimuli-responsive hydrogels have been a hot topic in recent decades. They can respond to external or internal stimulation and are used in the controlled delivery of drugs and tissue engineering. This review summarizes current progress in the use of stimuli-responsive hydrogels in bone and cartilage regeneration. The challenges, disadvantages, and future applications of stimuli-responsive hydrogels are briefly described.

Poly(β-amino ester) Dual-Drug-Loaded Hydrogels with Antibacterial and Osteogenic Properties for Bone Repair

In this study, we developed a poly(β-amino ester) (PBAE) hydrogel for the double release of vancomycin (VAN) and total flavonoids of Rhizoma Drynariae (TFRD). VAN was covalently bonded to PBAE polymer chains and was released to enhance the antimicrobial effect first. TFRD chitosan (CS) microspheres were physically dispersed in the scaffold, TFRD was released from the microspheres, and osteogenesis was induced subsequently. The scaffold had good porosity (90.12 ± 3.27%), and the cumulative release rate of the two drugs in PBS (pH 7.4) solution exceeded 80%. In vitro antimicrobial assays demonstrated the antibacterial properties of the scaffold against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Besides these, cell viability assays indicated that the scaffold had good biocompatibility. Moreover, alkaline phosphatase and matrix mineralization were expressed more than in the control group. Overall, cell experiments confirmed that the scaffolds have enhanced osteogenic differentiation capabilities. In conclusion, the dual-drug-loaded scaffold with antibacterial and bone regeneration effects is promising in the field of bone repair.