Biological Properties Of Hydrogels Research Articles

Optimizing biomaterial inks: A study on the printability of Carboxymethyl cellulose-Laponite nanocomposite hydrogels and dental pulp stem cells bioprinting

Tissue engineering approaches require biocompatible materials with precise pre-designed geometry, shape fidelity, and promote cellular functions. Addressing these requirements, our study focused on developing an optimized bioink formulation using carboxymethyl cellulose (CMC) and Laponite hydrogels tailored for extrusion-based three-dimensional bioprinting. To this, we investigated the rheological properties and filament behavior before and during printing. As Laponite concentration increased in CMC solutions, it improved shear-thinning behavior, viscosity, and storage modulus, resulting in well-defined filament characteristics with lower diffusion rates, excellent shape fidelity, and robust printability. Thus, we achieved a suitable biomaterial ink formulation with concentrations of 1 wt% of CMC and 4 wt% of Laponite (1C4L). Subsequently, a statistical analysis guided us to select the optimal parameters for large-scale construct printing: a nozzle speed of 5 mm/s, a print distance of 0.41 mm, and an extrusion multiplier of 1.35. After that, we enhanced the structural integrity of printed hydrogels through ionic crosslinking with calcium chloride (CaCl2) and citric acid (CA), revealing higher-strength hydrogels at higher concentrations of CaCl2. Finally, we have confirmed the groundbreaking potential of our bioink by integrating dental pulp mesenchymal stem cells (DPSC) into the 1C4L ink. Our bioprinted constructs showed optimized swelling, non-toxic effects, and retained excellent shape fidelity, crucial for creating anatomically accurate tissues. Our findings provide crucial insights linking the rheological analysis, the bioprinting process, and the biological properties of hydrogels, paving the way for their use for tissue engineering and other biomedical applications.

Clay-polymer hybrid hydrogels in the vanguard of technological innovations for bioremediation, metal biorecovery, and diverse applications.

Polymeric hydrogels are among the most studied materials due to their exceptional properties for many applications. In addition to organic and inorganic-based hydrogels, "hybrid hydrogels" have been gaining significant relevance in recent years due to their enhanced mechanical properties and a broader range of functionalities while maintaining good biocompatibility. In this sense, the addition of micro- and nanoscale clay particles seems promising for improving the physical, chemical, and biological properties of hydrogels. Nanoclays can contribute to the physical cross-linking of polymers, enhancing their mechanical strength and their swelling and biocompatibility properties. Nowadays, they are being investigated for their potential use in a wide range of applications, including medicine, industry, and environmental decontamination. The use of microorganisms for the decontamination of environments impacted by toxic compounds, known as bioremediation, represents one of the most promising approaches to address global pollution. The immobilization of microorganisms in polymeric hydrogel matrices is an attractive procedure that can offer several advantages, such as improving the preservation of cellular integrity, and facilitating cell separation, recovery, and transport. Cell immobilization also facilitates the biorecovery of critical materials from wastes within the framework of the circular economy. The present work aims to present an up-to-date overview on the different "hybrid hydrogels" used to date for bioremediation of toxic metals and recovery of critical materials, among other applications, highlighting possible drawbacks and gaps in research. This will provide the latest trends and advancements in the field and contribute to search for effective bioremediation strategies and critical materials recovery technologies.

A Review of Hydrogels, with its Properties and Applications in Medicine

A hydrogel is an insoluble in water three-dimensional polymer network that has the potential to absorb bodily fluids in a biological setting. Hydrogels may also be used in medical applications. Chemical crosslinking mechanisms such as optical polymerization, enzymatic reactions, and physical crosslinking mechanisms such as temperature- and pH-dependent processes, as well as ionic crosslinking, are all responsible for the formation of a network of polymers of this kind. Both physical and chemical hydrogels may be generated by the application of weak secondary forces, but chemical hydrogels can also be formed through the application of covalent forces. Hydrogels may be made from a wide variety of polymers derived from either natural or synthetic sources. The swelling, the mechanical characteristics, and the biological properties of hydrogels are some of the most essential aspects of hydrogels, and each of these qualities may have an effect on the structure and morphology of the hydrogel. Hydrogen is utilized in a variety of medical applications, including tissue engineering, contact lenses, wound dressings, and the release of therapeutic agents. This is possible because hydrogen has a structure that is analogous to the extracellular matrix (ECM), and it also has the ability to absorb water. There is a discussion on hydrogels, the many varieties of hydrogels, the characteristics of hydrogels, and their uses in medicine.

Hydrogels-A Promising Materials for 3D Printing Technology.

Hydrogels are a promising material for a variety of applications after appropriate functional and structural design, which alters the physicochemical properties and cell signaling pathways of the hydrogels. Over the past few decades, considerable scientific research has made breakthroughs in a variety of applications such as pharmaceuticals, biotechnology, agriculture, biosensors, bioseparation, defense, and cosmetics. In the present review, different classifications of hydrogels and their limitations have been discussed. In addition, techniques involved in improving the physical, mechanical, and biological properties of hydrogels by admixing various organic and inorganic materials are explored. Future 3D printing technology will substantially advance the ability to pattern molecules, cells, and organs. With significant potential for producing living tissue structures or organs, hydrogels can successfully print mammalian cells and retain their functionalities. Furthermore, recent advances in functional hydrogels such as photo- and pH-responsive hydrogels and drug-delivery hydrogels are discussed in detail for biomedical applications.

Recent progress of hydrogel-based local drug delivery systems for postoperative radiotherapy.

Surgical resection and postoperative radiotherapy remained the most common therapeutic modalities for malignant tumors. However, tumor recurrence after receiving such combination is difficult to be avoided because of high invasiveness and radiation resistance of cancer cells during long-term therapy. Hydrogels, as novel local drug delivery systems, presented excellent biocompatibility, high drug loading capacity and sustained drug release property. Compared with conventional drug formulations, hydrogels are able to be administered intraoperatively and directly release the entrapped therapeutic agents to the unresectable tumor sites. Therefore, hydrogel-based local drug delivery systems have their unique advantages especially in sensitizing postoperative radiotherapy. In this context, classification and biological properties of hydrogels were firstly introduced. Then, recent progress and application of hydrogels for postoperative radiotherapy were summarized. Finally, the prospects and challenges of hydrogels in postoperative radiotherapy were discussed.

A Silk Fibroin Methacryloyl-Modified Hydrogel Promoting Cell Adhesion for Customized 3D Cell-Laden Structures

Cell adhesion is the physical basis of tissue formation. Developing a kind of bioink with tunable mechanical properties and the promotion of cell adhesion is a major challenge for tissue engineering. In the present paper, a kind of hydrogel with good printable performance was developed, and cell adhesion was promoted in cell-laden DLP (Digital Light Processing) 3D bioprinting as a flexible solution for customized 3D structures. The hydrogel was prepared by modifying gelatin methacryloyl (GelMA)/hyaluronic acid methacryloyl (HAMA) with silk fibroin methacryloyl (SilMA). The three kinds of materials contain significant components of the extracellular matrix (ECM), such as glycosaminoglycan and proteins. Rheological results indicate that the multicomponent hydrogel precursors exhibit good photocuring behavior and are very suitable for DLP 3D bioprinting. The mechanical and biological properties of hydrogel can be tuned flexibly by SilMA content. Besides this, the SilMA/GelMA/HAMA hydrogel shows higher adhesion strength than the GelMA/HAMA hydrogel. The addition of SilMA into GelMA/HAMA significantly increased cell actin expression and promoted cell adhesion. Furthermore, the cell-laden 3D printed SilMA/GelMA/HAMA porous scaffold structure can remain stable after 7 days of in vitro culture. The survival rate of L929 fibroblasts can be up to 87%, exhibiting a good cell morphology and proliferation. All these results indicate that the SilMA/GelMA/HAMA hydrogel promoting cell adhesion will have broad implications for customized 3D structures in tissue engineering.

Gold Nanoparticle Promoted Formation and Biological Properties of Injectable Hydrogels.

Acceleration of gelation in the biological environment and improvement of overall biological properties of a hydrogel is of enormous importance. Biopolymer stabilized gold (Au) nanoparticles (NPs) exhibit cytocompatibility and therapeutic activity. Hence, in situ gelation and subsequent improvement in the property of a hydrogel by employing Au NPs is an attractive approach. We report that stable Au NPs accelerate the conventional nucleophilic substitution reaction of activated halide-terminated poly(ethylene glycol) and tertiary amine functional macromolecules, leading to the rapid formation of injectable nanocomposite hydrogels in vivo and ex vivo with improved modulus, cell adhesion, cell proliferation, and cytocompatibility than that of a pristine hydrogel. NP surfaces with low chain grafting density and good colloidal stability are crucial requirements for the use of these NPs in the hydrogel formation. Influence of the structure of the amine functional prepolymer, the spacer connecting the halide leaving groups of the substrate, and the structure of the stabilizer on the rate promoting activity of the NPs have been evaluated with model low-molecular-weight substrates and macromolecules by 1H NMR spectroscopy, rheological experiments, and density functional theory. Results indicate a significant effect of the spacer connecting the halide leaving group with the macromolecule. The Au nanocomposite hydrogels show sustained co-release of methotrexate, an anti-rheumatic drug, and the Au NPs. This work provides insights for designing an injectable nanocomposite hydrogel system with multifunctional property. The strategy of the use of cytocompatible Au NPs as a promoter provides new opportunity to obtain an injectable hydrogel system for biological applications.

Effect of the Composition of an Esterification Mixture on the Acid Properties of Gel-Forming Phosphorylated Polysaccharides

The physicochemical and biological properties of hydrogels based on starch, dextran, and cellulose phosphates synthesized in orthophosphoric acid–tributyl phosphate–phosphorus(V) oxide and orthophosphoric acid–urea systems are studied. It is found the apparent first step ionization constants of phosphate groups lie in the range of 2.5–2.9 and are virtually independent of the nature of the initial polysaccharide, the means of esterification, and the concentration of functional groups. It is concluded that the differences between the potentiometric curves of the titration of weakly acidic groups are due to the presence of polysaccharide phosphates. Carbamate groups contribute to the formation of a more cross-linked structure of hydrogels, making it difficult to ionize phosphate groups in the second stage. It is established that gel-forming phosphorylated polysaccharides exhibit antitumor activity.

Collagen-Chitosan Hydrogel Formed in Situ Via Enzymatic Crosslinking

In this research, injectable collagen-chitosan conjugates (Col-Chit-Ph) hydrogel was formed by oxidative coupling of phenolic hydroxyl (Ph) groups in polymer chain via peroxidase-catalysed crosslinking reaction. The resulting Col-Chit-Ph solutions formed rapid hydrogel at physiological conditions by utilizing H2O2. The amount of chitosan in the compositions of Col-Chit-Ph hydrogels influenced the mechanical properties of the hydrogels. Here, conjugates having Col:Chit ratio of 1:1 showed greater resistance to compression compared to conjugates having Col:Chit ratio of 3:2. Meanwhile, the efficiency of cell attachment for conjugates with Col:Chit ratio of 4:1 is higher than conjugates with Col:Chit ratio of 1:1. Although the biological properties of hydrogel was good at Col:Chit ratio of 4:1, this hydrogel easily destroyed by external force. However, with higher amount of chitosan in the composite, hydrogels were more mechanically stable. This indicates the importance of the chitosan ratio to the novel Col-Chit-Ph injectable hydrogel composite.

Ultrasonication and Genipin Cross-Linking to Prepare Novel Silk Fibroin–Gelatin Composite Hydrogel

Hydrogels are highly desirable tissue engineering scaffolds due to their high water content and structural similarity to a natural extra cellular matrix. However, the extensive use of hydrogels is limited by their low strength and facile degradation. By combining mechanical integrity and slow degradation of silk fibroin with excellent bioactivity of gelatin, a novel biocompatible protein-based composite hydrogel of silk fibroin and gelatin was developed. The gelation of silk fibroin aqueous solution was accelerated by ultrasonication, and gelatin derived from porcine skin was immobilized into the hydrogel network by the silk fibroin β-sheets. After that, genipin was used to post-cross-link the hydrogel to form a compact and stable hydrogel network. This hydrogel composite was a mechanically robust biomaterial with predictable long-term degradation characteristics. MG63 cells readily attached, spread, and proliferated on the surface of the hydrogels as demonstrated by fluorescein diacetate/propidium iodide staining and mitochondrial activity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Furthermore, the physicochemical and biological properties of hydrogel were fine-tunable by altering the ratio of silk fibroin and gelatin. The silk fibroin/gelatin composite hydrogels are anticipated to have the potential as cartilage or non-load-bearing bone tissue engineering and regeneration.

Microscale hydrogels for medicine and biology: synthesis, characteristics and applications

Microscale hydrogels with dimensions of 200µm or less are powerful tools for various biomedical applications such as tissue engineering, drug delivery, and biosensors, due to their size, biocompatibility, and their controllable biological, chemical, and mechanical properties. In this review, we provide a broad overview of the approaches used to synthesize and characterize microgels, as well as their applications. We discuss the various methods used to fabricate microgels, such as emulsification, micromolding, microfluidics, and photolithography. Furthermore, we discuss the effects of porosity and crosslinking density on the mechanical and biological properties of hydrogels. In addition, we give specific examples of the use of hydrogels, such as scaffolds and cell encapsulation for tissue engineering, controlled release materials for drug delivery, and environmentally sensitive sensors for microdevices. Finally, we will discuss the future applications of this technology.