Properties Of Hydrogels Research Articles

Photopolymerization of Chlorpromazine-Loaded Gelatin Methacryloyl Hydrogels: Characterization and Antimicrobial Applications.

This study investigates the synthesis, characterization, and antimicrobial properties of hydrogels synthesized through the UV-pulsed laser photopolymerization of a polymer-photoinitiator-chlorpromazine mixture. Chlorpromazine was used for its known enhanced antimicrobial properties when exposed to UV laser radiation. The hydrogel was formed from a mixture containing 0.05% Irgacure 2959, 10% gelatin methacryloyl, and various concentrations of chlorpromazine (1, 2, and 4 mg/mL). Laser-induced fluorescence spectroscopy was employed to monitor the photoinduced changes of chlorpromazine and Irgacure 2959 during hydrogel formation, providing insight into the photodegradation dynamics. FTIR spectroscopy confirmed the incorporation of irradiated chlorpromazine within the hydrogel matrix, while the release profiles of chlorpromazine showed sustained release only in hydrogels containing 1 mg/mL of CPZ. The hydrogel showed significant antimicrobial activity against MRSA bacteria when compared to that of penicillin. These findings highlight the potential of CPZ loaded during the photopolymerization process into hydrogels as effective antimicrobial agents with sustained release properties, making them suitable for combating resistant bacterial strains.

Engineering and Monitoring the Sustained Release of Extracellular Vesicles from Hydrogels for In Vivo Therapeutic Applications

Extracellular vesicles (EVs) are gaining interest in regenerative medicine and biomaterials have been shown to extend EV bioavailability following delivery. Herein, the labeling of both hydrogels and EVs is reported to better understand hydrogel design for sustained EV release into tissues. Shear‐thinning hydrogels are engineered using guest–host (i.e., adamantane–cyclodextrin) modifications to hyaluronic acid (GH), as well as GH hydrogels with the addition of gelatin crosslinked via transglutaminase (GH+Gel) to temporally control hydrogel properties. When labeled with a near‐IR dye and injected into rat myocardial tissue, the GH+Gel hydrogel is retained (>14 days) longer than the GH hydrogel alone (≈7 days), likely due to the added gelatin network. To overcome challenges associated with common EV labeling methods, a highly versatile metabolic labeling methodology is utilized via the incorporation of N‐azidoacetylmannosamine‐tetraacylated during EV synthesis to introduce azide groups that can then be reacted with DBCO dyes. When injected in saline, EVs are cleared within 24 h in hearts; however, hydrogels enhance EV retention, with levels based on hydrogel degradation behavior, namely, >14 days for GH+Gel hydrogel and ≈7 days for GH hydrogel alone. These findings support the use of hydrogels in EV therapies.

Cutting-Edge Hydrogel Technologies in Tissue Engineering and Biosensing: An Updated Review.

Hydrogels, known for their unique ability to retain large amounts of water, have emerged as pivotal materials in both tissue engineering and biosensing applications. This review provides an updated and comprehensive examination of cutting-edge hydrogel technologies and their multifaceted roles in these fields. Initially, the chemical composition and intrinsic properties of both natural and synthetic hydrogels are discussed, highlighting their biocompatibility and biodegradability. The manuscript then probes into innovative scaffold designs and fabrication techniques such as 3D printing, electrospinning, and self-assembly methods, emphasizing their applications in regenerating bone, cartilage, skin, and neural tissues. In the realm of biosensing, hydrogels' responsive nature is explored through their integration into optical, electrochemical, and piezoelectric sensors. These sensors are instrumental in medical diagnostics for glucose monitoring, pathogen detection, and biomarker identification, as well as in environmental and industrial applications like pollution and food quality monitoring. Furthermore, the review explores cross-disciplinary innovations, including the use of hydrogels in wearable devices, and hybrid systems, and their potential in personalized medicine. By addressing current challenges and future directions, this review aims to underscore the transformative impact of hydrogel technologies in advancing healthcare and industrial practices, thereby providing a vital resource for researchers and practitioners in the field.

Fabrication of mung bean protein-sugar beet pectin hydrogels by duo-induction of heating and laccase: Gelling properties and delivery of riboflavin

Aim of this research was to assess gelling properties and riboflavin delivery capacity of mung bean protein (MBP)-sugar beet pectin (SBP) hydrogels by duo-induction of heat and laccase. The results showed that hydrogel properties were regulated by SBP concentration. When SBP concentration was 0.20%, composite hydrogel had the highest stress (665.27 ± 26.36 Pa), water holding capacity (WHC) (75.68 ± 0.88%), storage modulus (G′) and surface hydrophobicity (H0) (9550.50 ± 33.86) (P < 0.05). At the same time, network structure of composite hydrogel was the densest and system was the most stable. When SBP concentration was 0.20%, composite hydrogel had better swelling rate, riboflavin encapsulation efficiency (51.81 ± 2.31%), cumulative release rate, biological accessibility (37.83 ± 0.90%) and storage stability (P < 0.05) compared with low concentration SBP. The introduction of SBP triggered the transition of riboflavin release mechanism to non-Fick release mechanism and transported riboflavin to the colon effectively. This study might provide theoretical support for the interaction between proteins and polysaccharides in composite hydrogel system as well as provide theoretical basis for composite hydrogel to be a delivery vehicle for bioactive substances.

Sliding on Slide-Ring Gels

Recent investigations have pointed to physical entanglements that greatly outnumber chemical crosslinks as key sources of energy dissipation and low friction in hydrogel networks. Slide-ring gels are an emerging class of hydrogels described by their mobile crosslinks, which are formed by rings topologically constrained to slide along linear polymer chains within the network. These materials have enjoyed decades of study by polymer chemists but have been underexplored by the tribology community. In this work, we synthesized a pseudo-rotaxane crosslinker from poly(ethylene glycol) diacrylate (PEG-diacrylate) and α-cyclodextrin-acrylate followed by hydrogel networks by connecting the sliding crosslinks with polyacrylamide chains. The mechanical and tribological properties of slide-ring hydrogels were investigated using a custom-built microtribometer. Slide-ring hydrogels exhibit unique behavior compared to conventional covalently crosslinked polyacrylamide hydrogels and offer a vast design space for future investigations.Graphical

RGD-functionalised self-assembling peptide hydrogel induces a proliferative profile in human osteoblasts in vitro.

Self-assembling peptide hydrogels (SAPHs) have been used in the past decade as reliable three-dimensional (3D) synthetic scaffolds for the culture of a variety of mammalian cells in vitro. Thanks to their versatile physicochemical properties, they allow researchers to tailor the hydrogel properties, including stiffness and functionality to the targeted cells and cells' behaviour. One of the advantages of using SAPH scaffolds is the ease of functionalisation. In the present work, we discuss the effect that functionalising the FEFEFKFK (F, phenylalanine; K, lysine; and E, glutamic acid) hydrogel scaffold using the cell-binding RGDS (fibronectin - R, arginine; G, glycine; D, aspartic acid; S, serine) epitope affects the material properties as well as the function of encapsulated human osteoblast cells. RGDS functionalisation resulted in cells adopting an elongated morphology, suggesting attachment and increased proliferation. While this led to higher cell viability, it also resulted in a decrease in extra-cellular matrix (ECM) protein production as well as a decrease in calcium ion deposition, suggesting lower mineralisation capabilities. The work clearly shows that SAPHs are a flexible platform that allow the modification of scaffolds in a controlled manner to investigate cell-material interactions.

Matrix Viscoelasticity Tunes the Mechanobiological Behavior of Chondrocytes.

In articular cartilage, the pericellular matrix acting as a specialized mechanical microenvironment modulates environmental signals to chondrocytes through mechanotransduction. Matrix viscoelastic alterations during cartilage development and osteoarthritis (OA) degeneration play an important role in regulating chondrocyte fate and cartilage matrix homeostasis. In recent years, scientists are gradually realizing the importance of matrix viscoelasticity in regulating chondrocyte function and phenotype. Notably, this is an emerging field, and this review summarizes the existing literatures to the best of our knowledge. This review provides an overview of the viscoelastic properties of hydrogels and the role of matrix viscoelasticity in directing chondrocyte behavior. In this review, we elaborated the mechanotransuction mechanisms by which cells sense and respond to the viscoelastic environment and also discussed the underlying signaling pathways. Moreover, emerging insights into the role of matrix viscoelasticity in regulating chondrocyte function and cartilage formation shed light into designing cell-instructive biomaterial. We also describe the potential use of viscoelastic biomaterials in cartilage tissue engineering and regenerative medicine. Future perspectives on mechanobiological comprehension of the viscoelastic behaviors involved in tissue homeostasis, cellular responses, and biomaterial design are highlighted. Finally, this review also highlights recent strategies utilizing viscoelastic hydrogels for designing cartilage-on-a-chip.

Optimization of mechanical properties of small diameter artificial blood vessels based on alginate/chitosan/gelatin

Due to the rise in cardiovascular disease and the problem of autologous transplant limitation, the emergence of 3D bioprinted blood vessels using natural polymer materials as ink is becoming increasingly important in the field of small-diameter artificial blood vessels (φ ≤ 6 mm). In this paper, gelatin was firstly adopted to explore alginate/chitosan composite hydrogel properties and solve the current issues of poor mechanical performance and suboptimal printability of small-diameter blood vessels, which indicated that the modification caused a 17.7 % increase in compressive strength and a 63.2 % enhancement in tensile properties. The material microstructure evaluation showed that the samples with gelatin(4 %) presented the excellent water absorption rate(>90 %) significantly increasing their porosities. A self-developed 3D bioprinter was utilized to clarify the controllable mechanism of small-diameter artificial blood vessel, which has superior performance and excellent printability. This study provides a new reference solution to the current challenges in the bio-ink performance and printability of small-diameter artificial blood vessels.

Effect of Silk Fibroin on the Mechanical and Transport Properties of Agarose Hydrogels.

In this work, the effect of incorporating silk fibroin, a fibrous biocompatible protein, into physically cross-linked agarose hydrogels was investigated as a simple model study to examine how supramolecular fibrous structures influence the properties of the hydrogels. The rheological and transport properties were studied. Fibroin did not change the general viscoelastic properties of the investigated hydrogels but changed the viscoelastic moduli values and also the mesh size, as calculated from rheometry data. Fibroin influenced the mechanical properties depending on its concentration: at lower concentrations, it increased the mesh size, while at higher concentrations, it acted as a filler, decreasing the mesh size. Similarly, the storage and loss moduli were affected, either increasing or decreasing based on the fibroin concentration. The fibroin effect on the diffusion of two dyes differing in their charge was the result of a combination of structural effects, responsible also for changes in the rheological properties, and a result of electrostatic interactions between the charged groups. For positively charged methylene blue, low fibroin concentrations accelerated diffusion, while higher concentrations slowed it by filling network vacancies. In contrast, for negatively charged eosin-B, fibroin strongly impeded diffusion at all concentrations due to electrostatic repulsion, leading to its accumulation at the hydrogel interface. The findings of this work may contribute to an understanding of the behavior of the extracellular matrix or soft tissues as well as to the development of the tailored design of hydrogel materials.

Eco-Friendly Carbon Nanotubes Reinforced with Sodium Alginate/Polyacrylic Acid for Enhanced Adsorption of Copper Ions: Kinetics, Isotherm, and Mechanism Adsorption Studies.

This study investigates the removal efficiency of Cu2+ from wastewater using a composite hydrogel made of carbon nanotubes (CNTs), sodium alginate (SA), and polyacrylic acid (PAA) prepared by free radical polymerization. The CNTs@SA/PAA hydrogel's structure and properties were characterized using SEM, TEM, FTIR, XRD, rheology, DSC, EDS, elemental mapping analysis, and swelling. The adsorption performance for Cu2+ was tested in batch adsorption experiments, considering the pH, dosage, initial concentration, and contact time. The optimal conditions for Cu2+ removal were pH 5.0, an adsorbent dosage of 500 mg/L, and a contact time of 360 min. The adsorption followed pseudo-second order kinetics. Isotherm analyses (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Sips, Toth, and Khan) revealed that the Freundlich isotherm best described the adsorption, with a maximum capacity of 358.52 mg/g. A thermodynamic analysis indicated that physical adsorption was the main interaction, with the spontaneity of the process also demonstrated. This study highlights the high efficiency and environmental friendliness of CNT@SA/PAA composites for Cu2+ removal from wastewater, offering a promising approach for water treatment.

Antibacterial Properties of Grape Seed Extract-Enriched Cellulose Hydrogels for Potential Dental Application: In Vitro Assay, Cytocompatibility, and Biocompatibility.

Hydrogels elaborated from Dasylirion spp. and enriched with grape seed extract (GSE) were investigated for tentative use in dental treatment. Cellulose-GSE hydrogels were elaborated with varying GSE contents from 10 to 50 wt%. The mechanical and physical properties, antimicrobial effect, biocompatibility, and in vitro cytotoxicity were studied. In all the cases, the presence of GSE affects the hydrogel's mechanical properties. The elongation decreased from 12.67 mm for the hydrogel without GSE to 6.33 mm for the hydrogel with the highest GSE content. The tensile strength decrease was from 52.33 N/mm2 (for the samples without GSE) and went to 40 N/mm2 for the highest GSE content. Despite the adverse effects, hydrogels possess suitable properties for manipulation. In addition, all hydrogels exhibited excellent biocompatibility and no cytotoxicity, and the antibacterial performance was demonstrated against S. mutans, E. Faecalis, S. aureus, and P. aureginosa. Furthermore, the hydrogels with 30 wt% GSE inhibited more than 90% of the bacterial growth.

Competition between cross-linking and force-induced local conformational changes determines the structure and mechanics of labile protein networks

Folded protein hydrogels are emerging as promising new materials for medicine and healthcare applications. Folded globular proteins can be modelled as colloids which exhibit site specific cross-linking for controlled network formation. However, folded proteins have inherent mechanical stability and unfolded in response to an applied force. It is not yet understood how colloidal network theory maps onto folded protein hydrogels and whether it models the impact of protein unfolding on network properties. To address this, we study a hybrid system which contains folded proteins (patchy colloids) and unfolded proteins (biopolymers). We use a model protein, bovine serum albumin (BSA), to explore network architecture and mechanics in folded protein hydrogels. We alter both the photo-chemical cross-linking reaction rate and the mechanical properties of the protein building block, via illumination intensity and redox removal of robust intra-protein covalent bonds, respectively. This dual approach, in conjunction with rheological and structural techniques, allows us to show that while reaction rate can ‘fine-tune’ the mechanical and structural properties of protein hydrogels, it is the force-lability of the protein which has the greatest impact on network architecture and rigidity. To understand these results, we consider a colloidal model which successfully describes the behaviour of the folded protein hydrogels but cannot account for the behaviour observed in force-labile hydrogels containing unfolded protein. Alternative models are needed which combine the properties of colloids (folded proteins) and biopolymers (unfolded proteins) in cross-linked networks. This work provides important insights into the accessible design space of folded protein hydrogels without the need for complex and costly protein engineering, aiding the development of protein-based biomaterials.

Molecular Chain Rearrangement-Induced In Situ Formation of Nanofibers for Improving the Strength and Toughness of Hydrogels.

Although poly(vinyl alcohol) (PVA) hydrogel has high elasticity and is suitable for cartilage tissue engineering, it is difficult to have both high strength and toughness. In this study, a simple and universal strategy is proposed to prepare strong and tough PVA hydrogels by in situ forming nanofibers on the original network structure induced by a molecular chain rearrangement. Quenching-tempering alteratively in ethanol and water several times is carried out to strengthen PVA hydrogels (PVA-Etn hydrogels) due to the advantages of noncovalent bonds in adjustability and reversibility. The results show that, after three quenching-tempering cycles, PVA-Et3 hydrogel with water content up to 79 wt % shows comprehensive improved mechanical properties. The compression modulus, tensile modulus, fracture strength, tensile strain, and tear energy of the PVA-Et3 hydrogel are 270, 250, 260, 130, and 180% of the initial PVA hydrogel, respectively. The improved mechanical properties of the PVA-Et3 hydrogel are attributed to the strong cross-linked PVA chains and hydrogen bond-reinforced nanofibers. This study not only provides a simple and efficient solution for the preparation of strong and tough polymer scaffolds in tissue engineering but also provides new insights for understanding the mechanism of improving the mechanical properties of polymer hydrogels by adjusting the molecular structure.

The effect of swelling/deswelling cycles on the mechanical behaviors of the polyacrylamide hydrogels

In practical applications, hydrogels experience swelling or deswelling in response to external stimuli, showcasing large deformation, tunable mechanical properties, and excellent biocompatibility. Previous studies focused on the effect of individual swelling or deswelling on the mechanical behaviors of hydrogels, neglecting the combined effects of both processes. The underlying mechanism of how the combined processes of swelling and deswelling affect the mechanical behaviors of hydrogels has not been systematically explored. To address this gap, polyacrylamide hydrogels with diverse initial compositions are prepared and subjected to controlled swelling-deswelling or deswelling-swelling cycles to achieve the same water content state. The mechanical properties of the hydrogel samples exposed to these cycles, including shear modulus, stretchability, Mullins effect, and fracture toughness, are experimentally evaluated and compared with those of as-prepared hydrogel samples without undergoing such cycles. Our findings reveal a significant reduction in stretchability, the Mullins effect, and fracture toughness of hydrogels exposed to either cycle. The extent of these reductions varies depending on the initial compositions of the hydrogels. This reduction in properties is primarily attributed to the rearrangement of hydrogel networks during these cycles, which becomes noticeable in hydrogels with network inhomogeneity. We also found that although the shear modulus of hydrogels varies after swelling-deswelling or deswelling-swelling cycles, it remains at relatively consistent levels compared to the as-prepared hydrogel. These findings suggest that the mechanical properties of hydrogels can be adjusted by optimizing the initial compositions and regulating the swelling-deswelling processing method. By studying the effects of swelling/deswelling cycles on the mechanical properties of hydrogels, we provide valuable insights for the application of hydrogels under dynamic environmental changes.

Modeling Cystic Fibrosis Chronic Infection Using Engineered Mucus-like Hydrogels.

The airway mucus of patients with cystic fibrosis has altered properties, which create a microenvironment primed for chronic infections that are difficult to treat. These complex polymicrobial airway infections and corresponding mammalian-microbe interactions are challenging to model in vitro. Here, we report the development of mucus-like hydrogels with varied compositions and viscoelastic properties reflecting differences between healthy and cystic fibrosis airway mucus. Models of cystic fibrosis and healthy airway microenvironments were created by combining the hydrogels with relevant pathogens, human bronchial epithelial cells, and an antibiotic. Notably, pathogen antibiotic resistance was not solely dependent on the altered properties of the mucus-like hydrogels but was also influenced by culture conditions including microbe species, monomicrobial or polymicrobial culture, and the presence of epithelial cells. Additionally, the cystic fibrosis airway model showed the ability to mimic features characteristic of chronic cystic fibrosis airway infections including sustained polymicrobial growth and increased antibiotic tolerance.

Development of a natural ingredient based on phenolic compounds from propolis extract and bentonite and its application in carrageenan hydrogels

Nowadays, there is an increasing consumer demand for more natural and environmentally friendly food additives. The current research aimed to produce and characterize a new additive based on bentonite and the phenolic compounds from green propolis extract, as well as to characterize the effect of this additive on the rheological properties of carrageenan hydrogels. The new additive (biohybrid) was obtained after the adsorption of phenolic compounds on the clay platelets. The adsorption mechanism was explained by Langmuir and Freundlich models, which suggested that adsorbed phenolic compounds form a monolayer and multilayers on the clay surface. Despite phenolic adsorption, the physico-chemical attributes of the bentonite remained unchanged. The incorporation of the biohybrid (BH) increased the sol-gel transition temperature of carrageenan hydrogels. This research reports for the first time the development and application of a new natural ingredient with potential food applications.

Influence of Initial Secondary Structure on Conformation and Mechanical Properties of Spider Silk Protein Gels.

Recombinant spider silk protein (RSP) is a promising biomaterial for developing high-performance materials independent of fossil fuels. In this study, we investigated the influence of the initial secondary structure of RSPs on the properties of RSP-based hydrogels. By altering the initial structure of RSP to β-sheets (β-RSP), α-helices (α-RSP), and random coils (rc-RSP) through solvent treatment, we compared the structures and mechanical properties of the resulting gels. Solid-state NMR revealed a β-sheet-rich structure in all gels, with the α-RSP gel exhibiting significantly higher strength and Young's modulus compared to the rc-RSP gel. X-ray diffraction revealed that the α-RSP gel had a unique crystalline structure, distinguishing it from the β-RSP and rc-RSP gels. The different initial secondary structures possibly lead to variations in the crystalline and network structures of the molecular chains within the gels, explaining the superior mechanical properties observed in the α-RSP gels.

Leveraging the Physicochemical Attributes of Biomimetic Hydrogel Nanocomposites in Stem Cell Differentiation.

The field of tissue engineering has witnessed significant advancements with the advent of hydrogel nanocomposites (HNC), emerging as a highly promising platform for regenerative medicine. HNCs provide a versatile platform that significantly enhances the differentiation of stem cells into specific cell lineages, making them highly suitable for tissue engineering applications. By incorporating nanoparticles, the mechanical properties of hydrogels, such as elasticity, porosity, and stiffness, are improved, addressing common challenges such as short-term stability, cytotoxicity, and scalability. These nanocomposites also exhibit enhanced biocompatibility and bioavailability, which are crucial to their effectiveness in clinical applications. Furthermore, HNCs are responsive to various triggers, allowing for precise control over their chemical properties, which is beneficial in creating 3D microenvironments, promoting wound healing, and enabling controlled drug delivery systems. This review provides a comprehensive overview of the production methods of HNCs and the factors influencing their physicochemical and biological properties, particularly in relation to stem cell differentiation and tissue repair. Additionally, it discusses the challenges in developing HNCs and highlights their potential to transform the field of regenerative medicine through improved mechanotransduction and controlled release systems.

The Influence of the Structural Architecture on the Swelling Kinetics and the Network Behavior of Sodium-Alginate-Based Hydrogels Cross-Linked with Ionizing Radiation.

The present work discusses the influence of the structural architecture of sodium alginate-co-acrylic acid-poly(ethylene) oxide hydrogels, crosslinked through electron beam (e-beam) radiation processing. The most important properties of the hydrogels were studied in detail to identify a correlation between the architecture of the hydrogels and their properties. Furthermore, the effect of sodium alginate (NaAlg) concentration, the amounts of the polymer blend, and the size of the samples on hydrogel properties were investigated. The results show that the hydrogels cross-linked (0.5% and 1% NaAlg) with 12.5 kGy exhibit improved physicochemical properties. High gel fraction levels (exceeding 83.5-93.7%) were achieved. Smaller hydrogel diameter (7 mm) contributed to a maximum swelling rate and degree of 20.440%. The hydrogel network was dependent on the hydrogels' diameter and the amount of polymer blend used. The hydrogels best suited the first-order rate constants and exhibited a non-Fickian diffusion character with diffusion exponent values greater than 0.5. This study indicates that the cross-linked hydrogel has good properties, particularly because of its high degree of swelling and extensive stability (more than 180 h) in water. These findings show that hydrogels can be effectively applied to the purification of water contaminated with metals, dyes, or even pharmaceuticals, as well as materials with a gradual release of bioactive chemicals and water retention.

Methods to achieve tissue-mimetic physicochemical properties in hydrogels for regenerative medicine and tissue engineering.

Hydrogels are water-swollen polymeric matrices with properties that are remarkably similar in function to the extracellular matrix. For example, the polymer matrix provides structural support and adhesion sites for cells in much of the same way as the fibers of the extracellular matrix. In addition, depending on the polymer used, bioactive sites on the polymer may provide signals to initiate certain cell behavior. However, despite their potential as biomaterials for tissue engineering and regenerative medicine applications, fabricating hydrogels that truly mimic the physicochemical properties of the extracellular matrix to physiologically-relevant values is a challenge. Recent efforts in the field have sought to improve the physicochemical properties of hydrogels using advanced materials science and engineering methods. In this review, we highlight some of the most promising methods, including crosslinking strategies and manufacturing approaches such as 3D bioprinting and granular hydrogels. We also provide a brief perspective on the future outlook of this field and how these methods may lead to the clinical translation of hydrogel biomaterials for tissue engineering and regenerative medicine applications.