Hyaluronic Acid Hydrogels Crosslinked in Physiological Conditions: Synthesis and Biomedical Applications

A quality by design approach to optimise disulfide-linked hyaluronic acid hydrogels

In this study, the disulfide-linked hyaluronic acid (HA) hydrogels were optimised for potential application as a scaffold in tissue engineering through the Quality by Design (QbD) approach. For this purpose, HA was first modified by incorporating the cysteine moiety into the HA backbone, which promoted the formation of disulfide cross-linked HA hydrogel at physiological pH. Utilising a Design of Experiments (DoE) methodology, the critical factors to achieve stable biomaterials, i.e. the degree of HA substitution, HA molecular weight, and coupling agent ratio, were explored. To establish a design space, the DoE was performed with 65 kDa, 138 kDa and 200 kDa HA and variable concentrations of coupling agent to optimise conditions to obtain HA hydrogel with improved rheological properties. Thus, HA hydrogel with a 12 % degree of modification, storage modulus of ≈2321 Pa and loss modulus of ≈15 Pa, was achieved with the optimum ratio of coupling agent. Furthermore, biocompatibility assessments in C28/I2 chondrocyte cells demonstrated the non-toxic nature of the hydrogel, underscoring its potential for tissue regeneration. Our findings highlight the efficacy of the QbD approach in designing HA hydrogels with tailored properties for biomedical applications.

On the design of lignin reinforced acrylic acid/hyaluronic acid adhesive hydrogels with conductive PEDOT:HA nanoparticles

Hydrogels are of great importance in biomedical engineering. They possess the ability to mimic bodily soft tissues, and this allows exciting possibilities for applications such as tissue engineering, drug delivery and wound healing, however much work remains on stability and mechanical robustness to allow for translation to clinical applications. The work herein describes the synthesis and analysis of a biocompatible, versatile hydrogel that has tailorable swelling, high stability when swollen and thermal stability. The synthesis methods used produce a hydrogel with high elasticity, good mechanical properties and rapid crosslinking whilst displaying biocompatibility, adhesion, and conductivity. It has been shown that cell viability in the samples is above 80 % in all cases, a Young's Modulus of up to 85 kPa and high swelling degrees were achieved. These materials show potential for use in numerous applications such as adhesive sensors, skin grafts and drug delivery systems.

Tunable and fast-cured hyaluronic acid hydrogel inspired on catechol architecture for enhanced adhesion property

Hyaluronic acid-based hydrogels have been broadly used in medical applications due to their remarkable properties such as biocompatibility, biodegradability, super hydroscopicity, non-immunogenic effect, etc. However, the inherent weak and hydrophilic polysaccharide structure of pure hyaluronic acid (HA) hydrogels has limited their potential use in muco-adhesiveness, wound dressing, and 3D printing. In this research, we developed in-situ forming of catechol-modified HA hydrogels with improved mechanical properties involving blue-light curing crosslinking reaction. The effect of catechol structure on the physicochemical properties of HA hydrogels was evaluated by varying the content (0-40 %). The as-synthesized hydrogel demonstrated rapid prototyping, excellent wetting adhesiveness, and good biocompatibility. Furthermore, an optimized hydrogel precursor solution was used as a blue light-cured bio-ink with high efficiency and good precision and successfully prototyped a microstructure that mimicked the human hepatic lobule by using DLP 3D printing method. This catechol-modified HA hydrogel with tunable physicochemical and rapid prototyping properties has excellent potential in biomedical engineering.

The bioengineering application of hyaluronic acid in tissue regeneration and repair

The multifaceted role of hyaluronic acid (HA) across diverse biomedical disciplines underscores its versatility in tissue regeneration and repair. HA hydrogels employ different crosslinking including chemical (chitosan, collagen), photo- initiation (riboflavin, LAP), enzymatic (HRP/H2O2), and physical interactions (hydrogen bonds, metal coordination). In biophysics and biochemistry, HA's signaling pathways, primarily through CD44 and RHAMM receptors, modulate cell behavior (cell migration; internalization of HA), inflammation, and wound healing. Particularly, smaller HA fragments stimulate inflammatory responses through toll-like receptors, impacting macrophages and cytokine expression. HA's implications in oncology highlight its involvement in tumor progression, metastasis, and treatment. Elevated HA in tumor stroma impacts apoptosis resistance and promotes tumor growth, presenting potential therapeutic targets to halt tumor progression. In orthopedics, HA's presence in synovial fluid aids in osteoarthritis management, as its supplementation alleviates pain, enhances synovial fluid's viscoelastic properties, and promotes cartilage integrity. In ophthalmology, HA's application in dry eye syndrome addresses symptoms by moisturizing the eyes, replenishing tear film deficiencies, and facilitating wound healing. Intravitreal injections and hydrogel-based systems offer versatile approaches for drug delivery and vitreous humor replacement. For skin regeneration and wound healing, HA hydrogel dressings exhibit exceptional properties by promoting moist wound healing and facilitating tissue repair. Integration of advanced regenerative tools like stem cells and solubilized amnion membranes into HA-based systems accelerates wound closure and tissue recovery. Overall, HA's unique properties and interactions render it a promising candidate across diverse biomedical domains, showcasing immense potentials in tissue regeneration and therapeutic interventions. Nevertheless, many detailed cellular and molecular mechanisms of HA and its applications remain unexplored and warrant further investigation.

Exploring the Formulation and Approaches of Injectable Hydrogels Utilizing Hyaluronic Acid in Biomedical Uses

The characteristics of injectable hydrogels make them a prime contender for various biomedical applications. Hyaluronic acid is an essential component of the matrix surrounding the cells; moreover, hyaluronic acid's structural and biochemical characteristics entice researchers to develop injectable hydrogels for various applications. However, due to its poor mechanical properties, several strategies are used to produce injectable hyaluronic acid hydrogel. This review summarizes published studies on the production of injectable hydrogels based on hyaluronic acid polysaccharide polymers and the biomedical field's applications for these hydrogel systems. Hyaluronic acid-based hydrogels are divided into two categories based on their injectability mechanisms: in situ-forming injectable hydrogels and shear-thinning injectable hydrogels. Many crosslinking methods are used to create injectable hydrogels; chemical crosslinking techniques are the most frequently investigated technique. Hybrid injectable hydrogel systems are widely investigated by blending hyaluronic acid with other polymers or nanoparticulate systems. Injectable hyaluronic acid hydrogels were thoroughly investigated and proven to demonstrate potential in various medical fields, including delivering drugs and cells, tissue repair, and wound dressings.

Exploring the Progress of Hyaluronic Acid Hydrogels: Synthesis, Characteristics, and Wide-Ranging Applications

This comprehensive review delves into the world of hyaluronic acid (HA) hydrogels, exploring their creation, characteristics, research methodologies, and uses. HA hydrogels stand out among natural polysaccharides due to their distinct features. Their exceptional biocompatibility makes them a top choice for diverse biomedical purposes, with a great ability to coexist harmoniously with living cells and tissues. Furthermore, their biodegradability permits their gradual breakdown by bodily enzymes, enabling the creation of temporary frameworks for tissue engineering endeavors. Additionally, since HA is a vital component of the extracellular matrix (ECM) in numerous tissues, HA hydrogels can replicate the ECM's structure and functions. This mimicry is pivotal in tissue engineering applications by providing an ideal setting for cellular growth and maturation. Various cross-linking techniques like chemical, physical, enzymatic, and hybrid methods impact the mechanical strength, swelling capacity, and degradation speed of the hydrogels. Assessment tools such as rheological analysis, electron microscopy, spectroscopy, swelling tests, and degradation studies are employed to examine their attributes. HA-based hydrogels feature prominently in tissue engineering, drug distribution, wound recovery, ophthalmology, and cartilage mending. Crafting HA hydrogels enables the production of biomaterials with sought-after qualities, offering avenues for advancements in the realm of biomedicine.

The rheology of injectable hyaluronic acid hydrogels used as facial fillers: A review

Injectable hyaluronic acid (HA) hydrogels have been popularized in facial aesthetics as they provide a long-lasting effect, low risk of complications, allergenicity tests are not required before application and can be easily removed by the action of hyaluronidases. On the other hand, the development of these systems requires in-depth studies of chemical mechanisms involved in hydrogel formation. Ideal dermal fillers should temporarily fluidize during extrusion through the needle and quickly recover their original shape after application. Hydrogels with more elastic properties, for example, are difficult to inject while viscous materials are too liquid. A balance between both properties should be achieved. Each region of the face requires products with distinct rheological properties. High G' dermal fillers are preferable for deeper wrinkles whereas the counterpart with lower values of G' is more indicated in superficial wrinkles or lip augmentation. Factors such as molecular weight and concentration of HA, pH, type and concentration of the crosslinking agent, particle size, crosslinking reaction time and crosslinking agent/polysaccharide ratio should be modulated to achieve specific rheological properties. In this review, the effect of each variable is discussed in detail to guide the rational development of new dermal fillers.

Hyaluronic acid hydrogels with excellent self-healing capacity and photo-enhanced mechanical properties for wound healing

A continuously stable moist healing environment is immensely beneficial for wound healing, which can be availably achieved by providing an in situ hydrogel with enough strength resembling skin tissue and self-healing ability. Herein, through a dual-crosslinking strategy, hyaluronic acid-based hydrogels with excellent self-healing capacity and enhanced mechanical properties are fabricated via the acylhydrazone linkages and subsequent photocrosslinking based on hydrazide-modified sodium hyaluronate and aldehyde-modified maleic sodium hyaluronate. The hydrogels demonstrate the fast gelation process (< 1 min), the controlled swelling behaviors, and the good biocompatibility. Notably, they possess enhanced mechanical strength similar to the human dermis (∼ 2.2 kPa). Also, they can self-heal rapidly with a self-healing efficiency of ∼90 % at 6 h. Based on this, the hyaluronic acid-based hydrogels, without any biological factors involved, can facilitate the full-thickness skin wound reconstruction process by accelerating the three phases of the wound repair, including reducing wound inflammation in the inflammatory phase, promoting angiogenesis in the proliferative phase, and promoting the deposition and reconstruction of collagen in the remodeling phase. The produced hyaluronic acid hydrogel can serve as an ideal candidate for wound healing.

Novel Injectable Hydrogel Formulations and Gas Chromatography Analysis of the Residual Crosslinker in Formulations Intended for Pharmaceutical and Cosmetic Applications

Novel hyaluronic acid (HA) crosslinked with pentaerythritol tetra-acrylate (PT) injectable hydrogels was invented. These injectable hydrogel/dermal filler formulations were synthesised using HA and the acrylate PT as a crosslinker under basic pH conditions using thermal crosslinking methods (oven heating), which provides a simple, safe, and eco-friendly method for crosslinking in 4 h under 45 °C. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were conducted to represent the difference between the formulations in terms of peak formation and pore size, respectively. The crosslinking was partial as is considered to be typical for dermal injectable fillers. The rheological properties of these formulations showed that these novel dermal injectables are highly promising, and the newly developed fillers could be used with better results for dermal anti-wrinkle corrections, shaping, and volumising reasons. Furthermore, crosslinker (PT) residual analysis was carried out to state the formulations that are valid and acceptable for intradermal usage. The results from the GC method validation revealed it was a suitable method for this study. The GC analysis of all five injectable hydrogel/filler formulations demonstrated the formulations HA-PT 1, 2, 3 and 4 were formulated using (0.05-0.1)% w/w PT containing residual PT monomers within the safe limits that were determined to be below (0.008% w/w). This work has shown the development of a novel injectable hydrogel/filler formulation for pharmaceutical and cosmetic applications can be prepared in a more sustainable and simple way using pentaerythritol tetra-acrylate as a crosslinker agent, which holds great promise for the industry's future advancement.

Dual-Modified Hyaluronic Acid for Tunable Double Cross-Linked Hydrogel Adhesives

Conventional techniques for the closure of wounds, such as sutures and staples, have significant drawbacks that can negatively impact wound healing. Tissue adhesives have emerged as promising alternatives, but poor adhesion, low mechanical properties, and toxicity have hindered their widespread clinical adoption. In this work, a dual modified, aldehyde and methacrylate hyaluronic acid (HA) biopolymer (HA-MA-CHO) has been synthesized through a simplified route for use as a double cross-linked network (DCN) hydrogel (HA-MA-CHO-DCN) adhesive for the effective closure and sealing of wounds. HA-MA-CHO-DCN cross-links in two stages: initial cross-linking of the aldehyde functionality (CHO) of HA-MA-CHO using a disulfide-containing cross-linker, 3,3'-dithiobis (propionic hydrazide) (DTPH), leading to the formation of a self-healing injectable gel, followed by further cross-linking via ultraviolet (UV) initiated polymerization of the methacrylate (MA) functionality. This hydrogel adhesive shows a stable swelling behavior and remarkable versatility as the storage modulus (G') has shown to be highly tunable (103-105 Pa) for application to many different wound environments. The new HA-MA-CHO-DCN hydrogel showed excellent adhesive properties by surpassing the burst pressure and lap-shear strength for the widely used bovine serum albumin-glutaraldehyde (BSAG) glue while maintaining excellent cell viability.

Emerging horizons and prospects of polysaccharide-constructed gels in the realm of wound healing

Polysaccharides, with the abundant availability, biodegradability, and inherent safety, offer a vast array of promising applications. Leveraging the remarkable attributes of polysaccharides, biomimetic and multifunctional hydrogels have emerged as a compelling avenue for efficacious wound dressing. The gels emulate the innate extracellular biomatrix as well as foster cellular proliferation. The distinctive structural compositions and profusion of functional groups within polysaccharides confer excellent physical/chemical traits as well as distinct restorative involvements. Gels crafted from polysaccharide matrixes serve as a robust defense against bacterial threats, effectively shielding wounds from harm. This comprehensive review delves into wound physiology, accentuating the significance of numerous polysaccharide-based gels in the wound healing context. The discourse encompasses an exploration of polysaccharide hydrogels tailored for diverse wound types, along with an examination of various therapeutic agents encapsulated within hydrogels to facilitate wound repair, incorporating recent patent developments. Within the scope of this manuscript, the perspective of these captivating gels for promoting optimal healing of wounds is vividly depicted. Nevertheless, the pursuit of knowledge remains ongoing, as further research is warranted to bioengineer progressive polysaccharide gels imbued with adaptable features. Such endeavors hold the promise of unlocking substantial potential within the realm of wound healing, propelling us toward multifaceted and sophisticated solutions.

Smart biodegradable hydrogels: Drug-delivery platforms for treatment of chronic ophthalmic diseases affecting the back of the eye

This paper aims to develop smart hydrogels based on functionalized hyaluronic acid (HA) and PLGA-PEG-PLGA (PLGA,poly-(DL-lactic-co-glycolic acid); PEG,polyethylene glycol) for use as intraocular drug-delivery platforms. Anti-inflammatory agent dexamethasone-phosphate (0.2 %w/v) was the drug selected to load on the hydrogels. Initially, different ratios of HA-aldehyde (HA-CHO) and thiolated-HA (HA-SH) were assayed, selecting as optimal concentrations 2 and 3 % (w/v), respectively. Optimized HA hydrogel formulations presented fast degradation (8 days) and drug release (91.46 ± 3.80 % in 24 h), thus being suitable for short-term intravitreal treatments. Different technology-based strategies were adopted to accelerate PLGA-PEG-PLGA water solubility, e.g. substituting PEG1500 in synthesis for higher molecular weight PEG3000 or adding cryopreserving substances to the buffer dissolution. PEG1500 was chosen to continue optimization and the final PLGA-PEG-PLGA hydrogels (PPP1500) were dissolved in trehalose or mannitol carbonate buffer. These presented more sustained release (71.77 ± 1.59 % and 73.41 ± 0.83 % in 24 h, respectively) and slower degradation (>14 days). In vitro cytotoxicity studies in the retinal-pigmented epithelial cell line (RPE-1) demonstrated good tolerance (viability values > 90 %). PLGA-PEG-PLGA hydrogels are proposed as suitable candidates for long-term intravitreal treatments. Preliminary wound healing studies with PLGA-PEG-PLGA hydrogels suggested faster proliferation at 8 h than controls.

Smart stimuli-responsive polysaccharide nanohydrogels for drug delivery: a review

Polysaccharides have found extensive utilization as biomaterials in drug delivery systems owing to their remarkable biocompatibility, simple functionalization, and inherent biological properties. Within the array of polysaccharide-based biomaterials, there is a growing fascination for self-assembled polysaccharide nanogels (NG) due to their ease of preparation and enhanced appeal across diverse biomedical appliances. Nanogel (or nanohydrogel), networks of nanoscale dimensions, are created by physically or chemically linking polymers together and have garnered immense interest as potential carriers for delivering drugs due to their favorable attributes. These include biocompatibility, high stability, the ability to adjust particle size, the capacity to load drugs, and their inherent potential to modify their surface to actively target specific cells or tissues via the attachment of ligands that can recognize corresponding receptors. Nanogels can be engineered to respond to specific stimuli, such as pH, temperature, light, or redox conditions, allowing controlled release of the encapsulated drugs. This intelligent targeting capability helps prevent drug accumulation in unintended tissues and reduces the potential side effects. Herein, an overview of nanogels is offered, comprising their methods of preparation and the design of stimulus-responsive nanogels that enable controlled release of drugs in response to specific stimuli.

Current application and modification strategy of marine polysaccharides in tissue regeneration: A review

Marine polysaccharides (MPs) are exceptional bioactive materials that possess unique biochemical mechanisms and pharmacological stability, making them ideal for various tissue engineering applications. Certain MPs, including agarose, alginate, carrageenan, chitosan, and glucan have been successfully employed as biological scaffolds in animal studies. As carriers of signaling molecules, scaffolds can enhance the adhesion, growth, and differentiation of somatic cells, thereby significantly improving the tissue regeneration process. However, the biological benefits of pure MPs composite scaffold are limited. Therefore, physical, chemical, enzyme modification and other methods are employed to expand its efficacy. Chemically, the structural properties of MPs scaffolds can be altered through modifications to functional groups or molecular weight reduction, thereby enhancing their biological activities. Physically, MPs hydrogels and sponges emulate the natural extracellular matrix, creating a more conducive environment for tissue repair. The porosity and high permeability of MPs membranes and nanomaterials expedite wound healing. This review explores the distinctive properties and applications of select MPs in tissue regeneration, highlighting their structural versatility and biological applicability. Additionally, we provide a brief overview of common modification strategies employed for MP scaffolds. In conclusion, MPs have significant potential and are expected to be a novel regenerative material for tissue engineering.

Remdesivir-Loaded Nanoliposomes Stabilized by Chitosan/Hyaluronic Acid Film with a Potential Application in the Treatment of Coronavirus Infection

An object of the present study was the development of liposomes loaded with the medicine Veklury® (remdesivir) stabilized by electrostatic adsorption of polysaccharide film formed from chitosans with different physicochemical characteristics and hyaluronic acid. The functionalization of the structures was achieved through the inclusion of an aptamer (oligonucleotide sequence) with specific affinity to the spike protein of the human coronavirus HCoV-OC43. The hydrodynamic size, electrokinetic potential and stability of the structures were evaluated at each step in the procedure. The encapsulation efficiency and loaded amount of remdesivir (99% and 299 µg/mL) were estimated by UV-vis spectroscopy. Our investigations showed manifestation of promising tendencies for prolonged periods of the drug release and increased effectiveness of its antiviral action. Among all studied versions of the delivery system, the most distinguished and suitable in a model coronavirus therapy are the liposomes formed from chitosan oligosaccharides. The cytotoxicity of the liposomes was determined against the HCT-8 cell line. A cytopathic effect inhibition test was used for the assessment of the antiviral activity of the compounds. The virucidal activity and the effect on the viral adsorption of the samples were reported by the end-point dilution method, and the alteration in viral titer was determined as Δlgs compared to untreated controls. The redox-modulating properties of the nanoparticles were studied in vitro in certain/several/a few chemical model systems. Our investigations showed a manifestation of promising tendencies for a prolonged effect of the drug release and increased effectiveness of its antiviral action.

A Double Cross-Linked Injectable Hydrogel Derived from Muscular Decellularized Matrix Promotes Myoblast Proliferation and Myogenic Differentiation

Injectable hydrogels possess tremendous merits for use in muscle regeneration; however, they still lack intrinsic biological cues (such as the proliferation and differentiation of myogenic cells), thus considerably restricting their potential for therapeutic use. Herein, we developed a double cross-linked injectable hydrogel composed of methacrylamidated oxidized hyaluronic acid (MOHA) and muscular decellularized matrix (MDM). The chemical composition of the hydrogel was confirmed using 1H NMR and Fourier transform infrared spectroscopy. To achieve cross-linking, the aldehyde groups in MOHA were initially reacted with the amino groups in MDM through a Schiff-based reaction. This relatively weak cross-linking provided the MOHA/MDM hydrogel with satisfactory injectability. Furthermore, the methacrylation of MOHA facilitated a second cross-linking mechanism via UV irradiation, resulting in improved gelation ability, biomechanical properties, and swelling performance. When C2C12 myogenic cells were loaded into the hydrogel, our results showed that the addition of MDM significantly enhanced myoblast proliferation compared to the MOHA hydrogel, as demonstrated by live/dead staining and Cell Counting Kit-8 assay after seven days of in vitro cultivation. In addition, gene expression analysis using quantitative polymerase chain reaction indicated that the MOHA/MDM hydrogel promoted myogenic differentiation of C2C12 cells more effectively than the MOHA hydrogel, as evidenced by elevated expression levels of myogenin, troponin T, and MHC in the MOHA/MDM hydrogel group. Moreover, after four to eight weeks of implantation in a full-thickness abdominal wall-defect model, the MOHA/MDM hydrogel could promote the reconstruction and repair of functional skeletal muscle tissue with enhanced tetanic force and tensile strength. This study provides a new double cross-linked injectable hydrogel for use in muscular tissue engineering.

Biological Macromolecule-Based Scaffolds for Urethra Reconstruction

Urethral reconstruction strategies are limited with many associated drawbacks. In this context, the main challenge is the unavailability of a suitable tissue that can endure urine exposure. However, most of the used tissues in clinical practices are non-specialized grafts that finally fail to prevent urine leakage. Tissue engineering has offered novel solutions to address this dilemma. In this technology, scaffolding biomaterials characteristics are of prime importance. Biological macromolecules are naturally derived polymers that have been extensively studied for various tissue engineering applications. This review discusses the recent advances, applications, and challenges of biological macromolecule-based scaffolds in urethral reconstruction.

The Effect of the Mechanical Properties of the 3D Printed Gelatin/Hyaluronic Acid Scaffolds on hMSCs Differentiation Towards Chondrogenesis

BACKGROUND

Tissue engineering, including 3D bioprinting, holds great promise as a therapeutic tool for repairing cartilage defects. Mesenchymal stem cells have the potential to treat various fields due to their ability to differentiate into different cell types. The biomimetic substrate, such as scaffolds and hydrogels, is a crucial factor that affects cell behavior, and the mechanical properties of the substrate have been shown to impact differentiation during incubation. In this study, we examine the effect of the mechanical properties of the 3D printed scaffolds, made using different concentrations of cross-linker, on hMSCs differentiation towards chondrogenesis.

METHODS

The 3D scaffold was fabricated using 3D bioprinting technology with gelatin/hyaluronic acid (HyA) biomaterial ink. Crosslinking was achieved by using different concentrations of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methlymorpholinium chloride n-hydrate (DMTMM), allowing for control of the scaffold's mechanical properties. The printability and stability were also evaluated based on the concentration of DMTMM used. The effects of the gelatin/HyA scaffold on chondrogenic differentiation was analyzed by utilizing various concentrations of DMTMM.

RESULTS

The addition of HyA was found to improve the printability and stability of 3D printed gelatin/HyA scaffolds. The mechanical properties of the 3D gelatin/HyA scaffold could be regulated through the use of different concentrations of DMTMM cross-linker. In particular, the use of 0.25 mM DMTMM for crosslinking the 3D gelatin/HyA scaffold resulted in enhanced chondrocyte differentiation.

CONCLUSION

The mechanical properties of 3D printed gelatin/HyA scaffolds cross-linked using various concentrations of DMTMM can influence the differentiation of hMSCs into chondrocytes.

Korean Amberjack Skin-Inspired Hyaluronic Acid Bioink for Reconstruction of Human Skin

Decellularized extracellular matrix (dECM) has been extensively employed as tissue engineering scaffolds because its components can greatly enhance the migration and proliferation of cultivating cells. In this study, we decellularized Korean amberjack skin and incorporated soluble fractions in hyaluronic acid hydrogels with 3D-printed tissue engineering hydrogels to overcome any limitation of animal-derived dECM. The hydrolyzed fish-dECM was mixed with methacrylated hyaluronic acid and chemically crosslinked to 3D-printed fish-dECM hydrogels, where fish-dECM contents affected both printability and injectability of the hydrogels. Swelling ratios and mass erosion of the 3D-printed hydrogels were dependent on fish-dECM contents, where higher fish-dECM in the hydrogel increased swelling ratios and mass erosion rates. The higher content of fish-dECM considerably enhanced the viability of the incorporated cells in the matrix for 7 days. Artificial human skin was constructed by seeding human dermal fibroblasts and keratinocytes in the 3D-printed hydrogels, and a formation of a bilayered skin was visualized with tissue staining. Thus, we envision that 3D-printed hydrogels containing fish-dECM can be an alternative bioink composed of a non-mammal-derived matrix.

Synthesis and characterisation of a novel poly(2-hydroxyethylmethacrylate)-chitosan hydrogels loaded cerium oxide nanocomposites dressing on cutaneous wound healing on nursing care of chronic wound

This study was designed to establish the composition of wound dressing based on poly(2-hydroxyethylmethacrylate)-chitosan (PHEM-CS) hydrogels-loaded cerium oxide nanoparticle (CeONPs) composites for cutaneous wound healing on nursing care of the chronic wound. The as-synthesised PHEM-CS/CeONPs hydrogels nanocomposites were characterised by using UV-visible spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermo gravimetric analysis. The influence of PHEM-CS/CeONPs hydrogels nanocomposites on the gelation time, swelling ratio, in vitro degradation, and mechanical properties was investigated. The as-prepared PHEM-CS/CeONPs hydrogels nanocomposites dressing shows high antimicrobial activity against Staphylococcus aureus and Escherichia coli. Similar trends were observed for the treatment of biofilms where PHEM-CS/CeONPs hydrogels nanocomposites displayed better efficiency. Furthermore, the biological properties of PHEM-CS/CeONPs hydrogels nanocomposites had non-toxic in cell viability and excellent cell adhesion behaviour. After 2 weeks, the wounds treated with the PHEM-CS/CeONPs hydrogels nanocomposite wound dressing achieved a significant closure to 98.5 ± 4.95% compared with the PHEM-CS hydrogels with nearly 71 ± 3.55% of wound closure. Hence, this study strongly supports the possibility of using this novel PHEM-CS/CeONPs hydrogels nanocomposites wound dressing for efficient cutaneous wound healing on chronic wound infection and nursing care.

Synthesis and evaluation of alginate, gelatin, and hyaluronic acid hybrid hydrogels for tissue engineering applications

Tissue engineering (TE) has been proposed extensively as a potential solution to the worldwide shortages of donor organs needed for transplantation. Over the years, numerous hydrogel formulations have been studied for various TE endeavours, including bone, cardiac or neural TE treatment strategies. Amongst the materials used, organic and biocompatible materials which aim to mimic the natural extracellular matrix of the native tissue have been investigated to create biomimicry regenerative environments. As such, the comparison between studies using the same materials is often difficult to accomplish due to varying material concentrations, preparation strategies, and laboratory settings, and as such these variables have a huge impact on the physio-chemical properties of the hydrogel systems. The purpose of the current study is to investigate popular biomaterials such as alginate, hyaluronic acid and gelatin in a variety of concentrations and hydrogel formulations. This aims to provide a clear and comprehensive understanding of their behaviours and provide a rational approach as to the appropriate selection of natural polysaccharides in specific targeted TE strategies.

Hyaluronic acid-based hydrogels: As an exosome delivery system in bone regeneration

Exosomes are extracellular vesicles (EVs) containing various ingredients such as DNA, RNA, lipids and proteins, which play a significant role in intercellular communication. Numerous studies have demonstrated the important role of exosomes in bone regeneration through promoting the expression of osteogenic-related genes and proteins in mesenchymal stem cells. However, the low targeting ability and short circulating half-life of exosomes limited their clinical application. In order to solve those problems, different delivery systems and biological scaffolds have been developed. Hydrogel is a kind of absorbable biological scaffold composed of three-dimensional hydrophilic polymers. It not only has excellent biocompatibility and superior mechanical strength but can also provide a suitable nutrient environment for the growth of the endogenous cells. Thus, the combination between exosomes and hydrogels can improve the stability and maintain the biological activity of exosomes while achieving the sustained release of exosomes in the bone defect sites. As an important component of the extracellular matrix (ECM), hyaluronic acid (HA) plays a critical role in various physiological and pathological processes such as cell differentiation, proliferation, migration, inflammation, angiogenesis, tissue regeneration, wound healing and cancer. In recent years, hyaluronic acid-based hydrogels have been used as an exosome delivery system for bone regeneration and have displayed positive effects. This review mainly summarized the potential mechanism of HA and exosomes in promoting bone regeneration and the application prospects and challenges of hyaluronic acid-based hydrogels as exosome delivery devices in bone regeneration.

Hyaluronic acid-based multifunctional carriers for applications in regenerative medicine: A review

Hyaluronic acid (HA) is an important type of naturally derived carbohydrate polymer with specific polysaccharide macromolecular structures and multifaceted biological functions, including biocompatibility, low immunogenicity, biodegradability, and bioactivity. Specifically, HA hydrogels in a microscopic scale have been widely used for biomedical applications, such as drug delivery, tissue engineering, and medical cosmetology, considering their superior properties outperforming the more conventional monolithic hydrogels in network homogeneity, degradation profile, permeability, and injectability. Herein, we reviewed the recent progress in the preparation and applications of HA microgels in biomedical fields. We first summarized the fabrication of HA microgels by focusing on the different crosslinking/polymerization schemes for HA gelation and the miniaturized fabrication techniques for producing HA-based microparticles. We then highlighted the use of HA-based microgels for different applications in regenerative medicine, including cartilage repair, bioactive delivery, diagnostic imaging, modular tissue engineering. Finally, we discussed the challenges and future perspectives in bridging the translational gap in the utilization of HA-based microgels in regenerative medicine.

Functional Skeletal Muscle Regeneration Using Muscle Mimetic Tissue Fabricated by Microvalve-Assisted Coaxial 3D Bioprinting

3D-printed artificial skeletal muscle, which mimics the structural and functional characteristics of native skeletal muscle, is a promising treatment method for muscle reconstruction. Although various fabrication techniques for skeletal muscle using 3D bio-printers are studied, it is still challenging to build a functional muscle structure. A strategy using microvalve-assisted coaxial 3D bioprinting in consideration of functional skeletal muscle fabrication is reported. The unit (artificial muscle fascicle: AMF) of muscle mimetic tissue is composed of a core filled with medium-based C2C12 myoblast aggregates as a role of muscle fibers and a photo cross-linkable hydrogel-based shell as a role of connective tissue in muscles that enhances printability and cell adhesion and proliferation. Especially, a microvalve system is applied for the core part with even cell distribution and strong cell-cell interaction. This system enhances myotube formation and consequently shows spontaneous contraction. A multi-printed AMF (artificial muscle tissue: AMT) as a piece of muscle is implanted into the anterior tibia (TA) muscle defect site of immunocompromised rats. As a result, the TA-implanted AMT responds to electrical stimulation and represents histologically regenerated muscle tissue. This microvalve-assisted coaxial 3D bioprinting shows a significant step forward to mimicking native skeletal muscle tissue.

Green Chemistry Principles for Nano- and Micro-Sized Hydrogel Synthesis

The growing demand for drug carriers and green-technology-based tissue engineering materials has enabled the fabrication of different types of micro- and nano-assemblies. Hydrogels are a type of material that have been extensively investigated in recent decades. Their physical and chemical properties, such as hydrophilicity, resemblance to living systems, swelling ability and modifiability, make them suitable to be exploited for many pharmaceutical and bioengineering applications. This review deals with a brief account of green-manufactured hydrogels, their characteristics, preparations, importance in the field of green biomedical technology and their future perspectives. Only hydrogels based on biopolymers, and primarily on polysaccharides, are considered. Particular attention is given to the processes of extracting such biopolymers from natural sources and the various emerging problems for their processing, such as solubility. Hydrogels are catalogued according to the main biopolymer on which they are based and, for each type, the chemical reactions and the processes that enable their assembly are identified. The economic and environmental sustainability of these processes are commented on. The possibility of large-scale processing in the production of the investigated hydrogels are framed in the context of an economy aimed at waste reduction and resource recycling.

Granular Disulfide-Crosslinked Hyaluronic Hydrogels: A Systematic Study of Reaction Conditions on Thiol Substitution and Injectability Parameters

Granular polymer hydrogels based on dynamic covalent bonds are attracting a great deal of interest for the design of injectable biomaterials. Such materials generally exhibit shear-thinning behavior and properties of self-healing/recovery after the extrusion that can be modulated through the interactions between gel microparticles. Herein, bulk macro-hydrogels based on thiolated-hyaluronic acid were produced by disulphide bond formation using oxygen as oxidant at physiological conditions and gelation kinetics were monitored. Three different thiol substitution degrees (SD%: 65%, 30% and 10%) were selected for hydrogel formation and fully characterized as to their stability in physiological medium and morphology. Then, extrusion fragmentation technique was applied to obtain hyaluronic acid microgels with dynamic disulphide bonds that were subsequently sterilized by autoclaving. The resulting granular hyaluronic hydrogels were able to form stable filaments when extruded through a syringe. Rheological characterization and cytotoxicity tests allowed to assess the potential of these materials as injectable biomaterials. The application of extrusion fragmentation for the formation of granular hyaluronic hydrogels and the understanding of the relation between the autoclaving processes and the resulting particle size and rheological properties should expand the development of injectable materials for biomedical applications.

Interactions between Sodium Hyaluronate and β-Cyclodextrin as Seen by Transport Properties

Knowledge of mass transport parameters, diffusion, and viscosity of hyaluronic acid (HA) in the presence of cyclodextrins is of considerable importance for areas such as food packaging and drug delivery, among others. Despite a number of studies investigating the functionalization of HA or the corresponding sodium salt by cyclodextrins, only a few studies have reported the effect of cyclodextrins on the mass transport of HA in the presence of these oligosaccharides. Here, we report the tracer binary and ternary interdiffusion coefficients of sodium hyaluronate (NaHy) in water and aqueous β-cyclodextrin solutions. The diffusion behavior of sodium hyaluronate was dependent on the reduced viscosity of NaHy, which, in turn, presented a concave dependence on concentration, with a minimum at approximately 2.5 g dm^-3. The significant decrease in the limiting diffusion coefficient of NaHy (at most 45%) at NaHy concentrations below 1 g dm^-3 in the presence of β-cyclodextrin, taking water as the reference, allowed us to conclude that NaHy strongly interacted with the cyclodextrin.

Chitosan nanocomposite as an effective carrier of potential herbicidal metabolites for noteworthy phytotoxic effect against major aquatic invasive weed water hyacinth (Eichhornia crassipes)

In this current work, the herbicidal activity of fungal metabolites stacked chitosan nanocomposite against significant aquatic invasive weed Eichhornia crassipes (water hyacinth) was examined. Herbicidal metabolites from the fungal strain Allophoma oligotrophica were extracted and purified under standard condition. Altered ionic gelation technique was received for the amalgamation of chitosan nanocomposite fabricated with herbicidal metabolites. Synthesized nanocomposite incited checked herbicidal impact on the leaflets of water hyacinth. Synthesized nanocomposite induced marked herbicidal effect on the tested leaflets of water hyacinth. Necrotic development on the tested leaflets at earlier incubation period followed by progressive enhancement of necrotic lesion reveals the noteworthy herbicidal activity of the synthesized nanocomposite. Parenchymal, mesenchymal tissue disintegration, reduction of total chlorophyll content, elevated anti oxidative enzymes and changes in qualitative protein profiling of tested leaflets reveals the nanocomposite induced noteworthy morphometric and functional effects. Effect of solvents on the release profile demonstrates that ethyl acetate treatment brought about controlled or sustained release of metabolites. No sign of toxic effect on the zebra fish embryonic developmental stages revealed biocompatibility of the nanocomposite.

Polymeric Materials as Indispensable Tools to Fight RNA Viruses: SARS-CoV-2 and Influenza A

Towards the end of 2019 in Wuhan, suspicions of a new dangerous virus circulating in the air began to arise. It was the start of the world pandemic coronavirus disease 2019 (COVID-19). Since then, considerable research data and review papers about this virus have been published. Hundreds of researchers have shared their work in order to achieve a better comprehension of this disease, all with the common goal of overcoming this pandemic. The coronavirus is structurally similar to influenza A. Both are RNA viruses and normally associated with comparable infection symptoms. In this review, different case studies targeting polymeric materials were appraised to highlight them as an indispensable tool to fight these RNA viruses. In particular, the main focus was how polymeric materials, and their versatile features could be applied in different stages of viral disease, i.e., in protection, detection and treatment.

Biopolymeric nanocarrier: an auspicious system for oral delivery of insulin

Subcutaneous administration of insulin has been practiced for the clinical supervision of diabetes pathogenesis but it is often ineffective to imitate the glucose homeostasis and is always invasive. Therefore, it causes patient discomfort and infection of local tissue. These issues lead to finding an alternative route for insulin delivery that could be effective, promising, and non-invasive. However, delivery of insulin orally is the most suitable route but the rapid breakdown of insulin by the gastrointestinal enzymes becomes a major barrier to this method. Therefore, nanocarriers (which guard insulin against degradation and facilitate its uptake) are preferred for oral insulin delivery. Among various categories of nanocarriers, bio-polymeric nanocarriers draw special attention owing to their hydrophilic, non-toxic, and biodegradable nature. This review provides a detailed overview of insulin-loaded biopolymer-based nanocarriers, which give future direction in the optimization and development of a clinically functional formulation for their effective and safe delivery.

Biomimetic injectable hydrogel based on silk fibroin/hyaluronic acid embedded with methylprednisolone for cartilage regeneration

Articular cartilage injury is characterized by limited self-repair capacity due to the shortage of blood vessels, lymphatics, and nerves. Hence, this study aims to exploit a classic injectable hydrogel platform that can restore the cartilage defects with minimally invasive surgery, which is similar to the natural extracellular microenvironment, and highly porous network for cell adhesion and proliferation. In this study, an injectable scaffold system comprised of silk fibroin (SF) and hyaluronic acid (HA) was developed to adapt the above requirements. Besides, methylprednisolone (MP) was encapsulated by SF/HA scaffold for alleviating inflammation. The SF/HA hydrogel scaffold was prepared by chemical cross-linking between the lysine residues of SF via Schiff base formation, and pore diameter of the obtained hydrogels was 100.47 ± 32.09 µm. The highly porous nature of hydrogel could further benefit the soft tissue regeneration. Compared with HA-free hydrogels, SF/HA hydrogel showed more controlled release on MP. In ovo experiment of chick embryo chorioallantoic membrane (CAM) demonstrated that SF/HA hydrogels not altered the angiogenesis and formation of blood vessels, thus making it suitable for cartilage regeneration. Furthermore, in vivo gel formation was validated in mice model, suggesting in situ gel formation of SF/HA hydrogels. More importantly, SF/HA hydrogels exhibited the controlled biodegradation. Overall, SF/HA hydrogels provide further insights to the preparation of effective scaffold for tissue regeneration and pave the way to improve the articular cartilage injury treatment.

Advances in biomaterials as a retinal patch for the repair of rhegmatogenous retinal detachment

Rhegmatogenous retinal detachment (RRD) is the most common retinological emergency that can cause blindness without surgical treatment. RRD occurs when liquefied vitreous accumulates between the neurosensory retina and the retinal pigment epithelium via retinal breaks, which are caused by the separation of the vitreous from the retina with aging. Currently, the main treatment option is pars plana vitrectomy, which involves surgical removal of the vitreous and laser photocoagulation around retinal breaks to generate firm chorioretinal adhesion, as well as subsequent filling of the vitreous cavity with long-lasting substitutes (expansile gas or silocone oil) to prevent the connection between the subretinal space and the vitreous cavity via the breaks before the chorioretinal adhesion firm enough. However, the postoperative face-down position and the not very satisfactory first retinal reattachment rate place a heavy burden on patients. With the development of technology and materials engineering, researchers have developed biomaterials that can be used as a retinal patch to seal retinal breaks and prevent the connection of subretinal space and vitreous cavity via breaks, thus replacing the long-lasting vitreous substitutes and eliminating the postoperative face-down position. Preclinical studies have demonstrated that biomaterial sealants have enough biocompatibility and efficacy in the in vitro and in vivo experiments. Some sealants have been used in clinical trials on a small scale, and the results indicate promising application prospects of the biomaterial sealants as retinal patches in the repair of RRD. Herein, we review the recent advances in biomaterials as retinal patches for the repair of RRD, focusing on the biomaterial categories, methods, and procedures for sealing retinal breaks, as well as their biocompatibility and efficacy, current limitations, and development perspectives.

HYDRHA: Hydrogels of hyaluronic acid. New biomedical approaches in cancer, neurodegenerative diseases, and tissue engineering

In the last decade, hyaluronic acid (HA) has attracted an ever-growing interest in the biomedical engineering field as a biocompatible, biodegradable, and chemically versatile molecule. In fact, HA is a major component of the extracellular matrix (ECM) and is essential for the maintenance of cellular homeostasis and crosstalk. Innovative experimental strategies in vitro and in vivo using three-dimensional (3D) HA systems have been increasingly reported in studies of diseases, replacement of tissue and organ damage, repairing wounds, and encapsulating stem cells for tissue regeneration. The present work aims to give an overview and comparison of recent work carried out on HA systems showing advantages, limitations, and their complementarity, for a comprehensive characterization of their use. A special attention is paid to the use of HA in three important areas: cancer, diseases of the central nervous system (CNS), and tissue regeneration, discussing the most innovative experimental strategies. Finally, perspectives within and beyond these research fields are discussed.

Directional Submicrofiber Hydrogel Composite Scaffolds Supporting Neuron Differentiation and Enabling Neurite Alignment

Cell cultures aiming at tissue regeneration benefit from scaffolds with physiologically relevant elastic moduli to optimally trigger cell attachment, proliferation and promote differentiation, guidance and tissue maturation. Complex scaffolds designed with guiding cues can mimic the anisotropic nature of neural tissues, such as spinal cord or brain, and recall the ability of human neural progenitor cells to differentiate and align. This work introduces a cost-efficient gelatin-based submicron patterned hydrogel–fiber composite with tuned stiffness, able to support cell attachment, differentiation and alignment of neurons derived from human progenitor cells. The enzymatically crosslinked gelatin-based hydrogels were generated with stiffnesses from 8 to 80 kPa, onto which poly(ε-caprolactone) (PCL) alignment cues were electrospun such that the fibers had a preferential alignment. The fiber–hydrogel composites with a modulus of about 20 kPa showed the strongest cell attachment and highest cell proliferation, rendering them an ideal differentiation support. Differentiated neurons aligned and bundled their neurites along the aligned PCL filaments, which is unique to this cell type on a fiber–hydrogel composite. This novel scaffold relies on robust and inexpensive technology and is suitable for neural tissue engineering where directional neuron alignment is required, such as in the spinal cord.

A self-healing hydrogel based on crosslinked hyaluronic acid and chitosan to facilitate diabetic wound healing

Traditional wound dressings are not able to provide ideal environment for diabetic wounds surface thus hampered the regrowth of fresh tissues. In this study, we designed a novel in situ forming hydrogel and used it as wound dressing material. Carboxymethyl chitosan (CMCS) and oxidized hyaluronic acid (OHA) were selected to construct a pH-responsive and self-healing hydrogel system via Schiff base reaction. Taurine (Tau) with anti-inflammatory property was loaded in the hydrogel through the aforementioned reaction. Under the slightly acidic environment of the diabetic wound site, a responsive release of taurine molecules speeded up the transfer of the taurine into the wound. The physiochemical properties of the prepared CMCS-OHA-Tau hydrogel were characterized. The CMCS-OHA-Tau hydrogel showed good biocompatibility, enhancement of cell migration and inhibited production of inflammatory cytokines.Subsequently, the hydrogel was applied on the wounds of diabetic rats and its boosted efficacy for wound recovery was confirmed.

Self-Adhesive Hydrogel Biomimetic Periosteum to Promote Critical-Size Bone Defect Repair via Synergistic Osteogenesis and Angiogenesis

The periosteum plays an important role in the regeneration of critical-size bone defects, with functions of recruiting multiple cells, accelerating vascular network reconstruction, and guiding bone tissue regeneration. However, these functions cannot be easily implemented by simply simulating the periosteum via a material structure design or by loading exogenous cytokines. Herein, inspired by the periosteal function, we propose a biomimetic periosteum preparation strategy to enhance natural polymer hydrogel membranes using inorganic bioactive materials. The biomimetic periosteum having bone tissue self-adhesive functions and resembling an extracellular matrix was prepared using dopamine-modified gelatin and oxidized hyaluronan (GA/HA), and micro/nanobioactive glass (MNBG) was further incorporated into the hydrogel to fabricate an organic/inorganic co-crosslinked hydrogel membrane (GA/HA-BG). The addition of MNBG enhanced the stability of the natural polymer hydrogel membrane, resulting in a sustained degradation time, biomineralization, and long-term release of ions. The Ca²⁺ and SiO₄^4- ions released by bioactive glass were shown to recruit cells and promote the differentiation of bone marrow stromal cells into osteoblasts, initiating multicentric osteogenic behavior. Additionally, the bioactive ions were able to continuously stimulate the endogenous expression of vascular endothelial growth factor from human umbilical vein endothelial cells through the PI3K/Akt/HIF-1α pathway, which accelerated vascularization of the defect area and synergistically promoted the repair of bone defects. This organic-inorganic biomimetic periosteum has been proved to be effective and versatile in critical-size bone defect repair and is expected to provide a promising strategy for solving clinical issues.

Novel Trends in Hydrogel Development for Biomedical Applications: A Review

Nowadays, there are still numerous challenges for well-known biomedical applications, such as tissue engineering (TE), wound healing and controlled drug delivery, which must be faced and solved. Hydrogels have been proposed as excellent candidates for these applications, as they have promising properties for the mentioned applications, including biocompatibility, biodegradability, great absorption capacity and tunable mechanical properties. However, depending on the material or the manufacturing method, the resulting hydrogel may not be up to the specific task for which it is designed, thus there are different approaches proposed to enhance hydrogel performance for the requirements of the application in question. The main purpose of this review article was to summarize the most recent trends of hydrogel technology, going through the most used polymeric materials and the most popular hydrogel synthesis methods in recent years, including different strategies of enhancing hydrogels’ properties, such as cross-linking and the manufacture of composite hydrogels. In addition, the secondary objective of this review was to briefly discuss other novel applications of hydrogels that have been proposed in the past few years which have drawn a lot of attention.

Biocompatibility and Efficacy of a Linearly Cross-Linked Sodium Hyaluronic Acid Hydrogel as a Retinal Patch in Rhegmatogenous Retinal Detachment Repairment

To prevent the migration of retinal pigment epithelium (RPE) cells into the vitreous cavity through retinal breaks after the pars plana vitrectomy for the repair of rhegmatogenous retinal detachment (RRD), sealing retinal breaks with an appropriate material appears to be a logical approach. According to a review of ocular experiments or clinical trials, the procedure for covering retinal breaks with adhesives is complex. A commercially available cross-linked sodium hyaluronic acid (HA) hydrogel (Healaflow®) with the injectable property was demonstrated to be a perfect retinal patch in RRD clinical trials by our team. Based on the properties of Healaflow®, a linearly cross-linked sodium HA hydrogel (HA-engineered hydrogel) (Qisheng Biological Preparation Co. Ltd. Shanghai, China) with the injectable property was designed, whose cross-linker and cross-linking method was improved. The purpose of this study is to report the characteristics of an HA-engineered hydrogel using Healaflow® as a reference, and the biocompatibility and efficacy of the HA-engineered hydrogel as a retinal patch in the rabbit RRD model. The HA-engineered hydrogel exhibited similar dynamic viscosity and cohesiveness and G′ compared with Healaflow®. The G′ of the HA-engineered hydrogel varied from 80 to 160 Pa at 2% strain under 25°C, and remained constantly higher than G″ over the range of frequency from 0.1 to 10 Hz. In the animal experiment, clinical examinations, electroretinograms, and histology suggested no adverse effects of the HA-engineered hydrogel on retinal function and morphology, confirming its favorable biocompatibility. Simultaneously, our results demonstrated the efficacy of the HA-engineered hydrogel as a retinal patch in the RRD model of rabbit eyes, which can aid in the complete reattachment of the retina without the need for expansile gas or silicone oil endotamponade. The HA-engineered hydrogel could play the role of an ophthalmologic sealant due to its high viscosity and cohesiveness. This pilot study of a small series of RRD models with a short-term follow-up provides preliminary evidence to support the favorable biocompatibility and efficacy of the HA-engineered hydrogel as a promising retinal patch for sealing retinal breaks in retinal detachment repair. More cases and longer follow-up studies are needed to assess its safety and long-term effects.

Hyaluronic Acid-Based Nanomaterials as a New Approach to the Treatment and Prevention of Bacterial Infections

Bacterial contamination of medical devices is a great concern for public health and an increasing risk for hospital-acquired infections. The ongoing increase in antibiotic-resistant bacterial strains highlights the urgent need to find new effective alternatives to antibiotics. Hyaluronic acid (HA) is a valuable polymer in biomedical applications, partly due to its bactericidal effects on different platforms such as contact lenses, cleaning solutions, wound dressings, cosmetic formulations, etc. Because the pure form of HA is rapidly hydrolyzed, nanotechnology-based approaches have been investigated to improve its clinical utility. Moreover, a combination of HA with other bactericidal molecules could improve the antibacterial effects on drug-resistant bacterial strains, and improve the management of hard-to-heal wound infections. This review summarizes the structure, production, and properties of HA, and its various platforms as a carrier in drug delivery. Herein, we discuss recent works on numerous types of HA-based nanoparticles to overcome the limitations of traditional antibiotics in the treatment of bacterial infections. Advances in the fabrication of controlled release of antimicrobial agents from HA-based nanosystems can allow the complete eradication of pathogenic microorganisms.

Functionalized injectable hyaluronic acid hydrogel with antioxidative and photothermal antibacterial activity for infected wound healing

Infected wound healing has always been a challenge in clinic. Effective and economic wound dressings with combined antibacterial activity and pro-healing function are highly desirable, especially in the context of infected wounds. An obvious advantage of antibacterial wound dressing is to avoid the overuse of antibiotics and the occurrence of drug resistance. Herein, an injectable hyaluronic acid hydrogel with antioxidative and photothermal antibacterial activity as a functional dressing was prepared, characterized and evaluated in an experimental infected wound model. This hydrogel was developed by loading graphene oxide (GO) in a natural polymer network consisting of hyaluronic acid grafted with tyramine (HT) and gelatin grafted with gallic acid (GGA). The HT/GGA/GO hydrogels have a porous cross-linked network structure and demonstrate a good stability, biocompatibility, antioxidant, hemostatic and photothermal antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, in vivo studies have shown that HT₁/GGA₂/GO_0.1 hydrogel dressing combined with photothermal therapy can effectively prevent early infection and accelerate wound healing. These results indicated this functionalized injectable hydrogel HT₁/GGA₂/GO_0.1 has a great potential in wound dressing application.

Drug Delivery from Hyaluronic Acid–BDDE Injectable Hydrogels for Antibacterial and Anti-Inflammatory Applications

Hyaluronic acid (HA) injectable biomaterials are currently applied in numerous biomedical areas, beyond their use as dermal fillers. However, bacterial infections and painful inflammations are associated with healthcare complications that can appear after injection, restricting their applicability. Fortunately, HA injectable hydrogels can also serve as drug delivery platforms for the controlled release of bioactive agents with a critical role in the control of certain diseases. Accordingly, herein, HA hydrogels were crosslinked with 1 4-butanediol diglycidyl ether (BDDE) loaded with cefuroxime (CFX), tetracycline (TCN), and amoxicillin (AMX) antibiotics and acetylsalicylic acid (ASA) anti-inflammatory agent in order to promote antibacterial and anti-inflammatory responses. The hydrogels were thoroughly characterized and a clear correlation between the crosslinking grade and the hydrogels’ physicochemical properties was found after rheology, scanning electron microscopy (SEM), thermogravimetry (TGA), and differential scanning calorimetry (DSC) analyses. The biological safety of the hydrogels, expected due to the lack of BDDE residues observed in ¹H-NMR spectroscopy, was also corroborated by an exhaustive biocompatibility test. As expected, the in vitro antibacterial and anti-inflammatory activity of the drug-loaded HA-BDDE hydrogels was confirmed against Staphylococcus aureus by significantly decreasing the pro-inflammatory cytokine levels.

Natural Hydrogel-Based Bio-Inks for 3D Bioprinting in Tissue Engineering: A Review

Three-dimensional (3D) printing is well acknowledged to constitute an important technology in tissue engineering, largely due to the increasing global demand for organ replacement and tissue regeneration. In 3D bioprinting, which is a step ahead of 3D biomaterial printing, the ink employed is impregnated with cells, without compromising ink printability. This allows for immediate scaffold cellularization and generation of complex structures. The use of cell-laden inks or bio-inks provides the opportunity for enhanced cell differentiation for organ fabrication and regeneration. Recognizing the importance of such bio-inks, the current study comprehensively explores the state of the art of the utilization of bio-inks based on natural polymers (biopolymers), such as cellulose, agarose, alginate, decellularized matrix, in 3D bioprinting. Discussions regarding progress in bioprinting, techniques and approaches employed in the bioprinting of natural polymers, and limitations and prospects concerning future trends in human-scale tissue and organ fabrication are also presented.

Hydrogels on the Base of Modified Chitosan and Hyaluronic Acid Mix as Polymer Matrices for Cytostatics Delivery

The development of biodegradable polysaccharide hydrogel matrices for cytostatic delivery can improve the therapeutic results of patients by prolonging the action of the drug, reducing its toxicity and providing additional biological activity by polysaccharides. In this work, N-succinyl chitosan/hyaluronic acid dialdehyde/cytostatic formulations have been prepared using two different chitosan grades (30 kDa and 150 kDa) and hyaluronic acid dialdehyde. The interaction of amino groups of N-succinyl chitosan and aldehydes of hyaluronic acid resulted in the formation of azomethine bonds and was demonstrated using ¹³C NMR. The elastic properties of the obtained hydrogels determine their use as implants. Two cytostatics—5-fluorouracil and mitomycin C were chosen as drugs because of their using both in oncology and in ophthalmology for the surgical treatment of glaucoma. Hydrogel formulations containing cytostatic were prepared and drug release was studied using in vitro dialysis method. It was established that the molecular weight of N-succinyl chitosan and rheological properties of hydrogel influenced the drug release behavior of the gelling delivery system. Formulations prepared from N-succinyl chitosan with greatest molecular weight and mitomycin C were found to be the most promising for medical application due to their rheological properties and prolonged drug release. Mild preparation conditions, simplicity of the technique, short gelation time (within a minute), 100% yield of hydrogel, suitability for drug release applications are the main advantages of the obtained hydrogels.