Gelatin is a natural biopolymer derived from collagen. Due to its many advantages, such as swelling capacity, biodegradability, biocompatibility, and commercial availability, gelatin is widely used in the field of pharmacy, medicine, and the food industry. Gelatin solutions easily form hydrogels during cooling, however, the materials are mechanically poor. To improve their properties, they are often chemically crosslinked. The cross-linking agents are divided into two groups: Zero-length and non-zero-length cross-linkers. In this study, gelatin was cross-linked by three different cross-linking agents: EDC-NHS, as a typically used cross-linker, and also squaric acid (SQ) and dialdehyde starch (DAS), as representatives of a second group of cross-linkers. For all prepared gelatin hydrogels, mechanical strength tests, thermal analysis, infrared spectroscopy, swelling ability, and SEM images were performed. The results indicate that the dialdehyde starch is a better cross-linking agent for gelatin than EDC-NHS. Meanwhile, the use of squaric acid does not give beneficial changes to the properties of the hydrogel.

Hydrogels as biomaterials possess appropriate physicochemical and mechanical properties that enable the formation of a three-dimensional, stable structure used in tissue engineering and 3D printing. The integrity of the hydrogel composition is due to the presence of covalent or noncovalent cross-linking bonds. Using various cross-linking methods and agents is crucial for adjusting the properties of the hydrogel to specific biomedical applications, e.g., for direct bioprinting. The research subject was mixtures of gel-forming polymers: sodium alginate and gelatin. The polymers were cross-linked ionically with the addition of CaCl₂ solutions of various concentrations (10%, 5%, 2.5%, and 1%) and covalently using squaric acid (SQ) and dialdehyde starch (DAS). Initially, the polymer mixture’s composition and the hydrogel cross-linking procedure were determined. The obtained materials were characterized by mechanical property tests, swelling degree, FTIR, SEM, thermal analysis, and biological research. It was found that the tensile strength of hydrogels cross-linked with 1% and 2.5% CaCl₂ solutions was higher than after using a 10% solution (130 kPa and 80 kPa, respectively), and at the same time, the elongation at break increased (to 75%), and the stiffness decreased (Young Modulus is 169 kPa and 104 kPa, respectively). Moreover, lowering the concentration of the CaCl₂ solution from 10% to 1% reduced the final material’s toxicity. The hydrogels cross-linked with 1% CaCl₂ showed lower degradation temperatures and higher weight losses than those cross-linked with 2.5% CaCl₂ and therefore were less thermally stable. Additional cross-linking using SQ and DAS had only a minor effect on the strength of the hydrogels, but especially the use of 1% DAS increased the material’s elasticity. All tested hydrogels possess a 3D porous structure, with pores of irregular shape and heterogenic size, and their swelling degree initially increased sharply to the value of approx. 1000% during the first 6 h, and finally, it stabilized at a level of 1200–1600% after 24 h. The viscosity of 6% gelatin and 2% alginate solutions with and without cross-linking agents was similar, and they were only slightly shear-thinning. It was concluded that a mixture containing 2% sodium alginate and 6% gelatin presented optimal properties after gel formation and lowering the concentration of the CaCl₂ solution to 1% improved the hydrogel’s biocompatibility and positively influenced the cross-linking efficiency. Moreover, chemical cross-linking by DAS or SQ additionally improved the final hydrogel’s properties and the mixture’s printability. In conclusion, among the tested systems, the cross-linking of 6% gelatin–2% alginate mixtures by 1% DAS addition and 1% CaCl₂ solution is optimal for tissue engineering applications and potentially suitable for 3D printing.

Poloxamers are widely used in biomedical applications, but their effectiveness depends on achieving an optimal sol-gel phase transition near body temperature. This study evaluates three different poloxamer mixtures for their potential in treating meniscus tears, focusing on gel formation, injectability, and cell compatibility. The rheological properties, cytotoxicity assessments, and cellular migration experiments were studied using NIH/3T3 fibroblast cells as the standard experimental model for primary research. The poloxamer hydrogels showed properties well suited to injectable or drug delivery systems. Specifically, the combination of Synperonic F108 and Poloxamer 188 tended to show less adhesion and more aggregation, followed by a greater number of viable cells, suggesting its utility as a coating or foundational matrix. Concurrently, the Kolliphor 407 and Poloxamer 188 combination exhibited increased viscosity, maintaining a gel state at physiological temperature. Its biocompatibility indicated the potential for injectable controlled-release systems for musculoskeletal injuries. Our findings demonstrate that the poloxamer concentration and composition significantly influence their biomedical applications. These triblock copolymer systems indicated useful characteristics for surgical applications, such as favorable sol-gel transition kinetics and biocompatibility, suggesting potential applications in osteoarticular regeneration.

Human amniotic membranes (hAMs) obtained during cesarean sections have proven to be clinically useful as an interesting biomaterial in a wide range of tissue engineering applications such as ocular surface reconstruction, burn treatments, chronic wounds, or bedsore ulcers. It presents antimicrobial properties, promotes epithelization, reduces inflammation and angiogenesis, contains growth factors, and constitutes the reservoir of stem cells. However, variability in hAM stiffness and its fast degradation offers an explanation for the poor clinical applications and reproducibility. In addition, the preparatory method of hAM for clinical use can affect its mechanical properties, and these differences can influence its application. As a directly applied biomaterial, the hAM should be available in a ready-to-use manner in clinical settings. In the present study, we performed an analysis to improve the mechanical properties of hAM by the addition of various reagents used as protein cross-linkers: EDC/NHS, PEG-dialdehyde, PEG-NHS, dialdehyde starch, and squaric acid. The effect of hAM modification using different cross-linking agents was determined via infrared spectroscopy, thermal analyses, mechanical properties analyses, enzymatic degradation, and cytotoxicity tests. The use of PEG-dialdehyde, PEG-NHS, dialdehyde starch, and squaric acid increases the mechanical strength and elongation at the breaking point of hAM, while the addition of EDC/NHS results in material stiffening and shrinkage. Also, the thermal stability and degradation resistance were evaluated, demonstrating higher values after cross-linking. Overall, these results suggest that modification of human amniotic membrane by various reagents used as protein cross-linkers may make it easier to use hAM in clinical applications, and the presented study is a step forward in the standardization of the hAM preparation method.

Poloxamer-based hydrogels are a promising matrix for controlled injectable drug delivery, exhibiting a physiological sol–gel transition, stable pH and osmolarity, and sustained release of diclofenac and paracetamol for osteoarticular injuries.

Meniscal injuries are common and often lead to chronic pain, joint instability, and an increased risk of osteoarthritis. Traditional treatments, such as partial meniscectomy, may accelerate joint degeneration. In recent years, biologically active therapies, including platelet-rich plasma (PRP), mesenchymal stem cells (MSCs), hyaluronic acid (HA), bone marrow aspirate concentrate (BMAC), collagen, growth factors (GFs), and silk fibroin (SF), have emerged as promising strategies to enhance meniscal healing. This review evaluates the efficiency of these biological agents in promoting meniscal repair, with a particular focus on their potential integration into injectable hydrogel systems for targeted, minimally invasive delivery. Recent literature from 2015 to 2025 has provided growing insights into the role of biologically active agents and biomaterials in meniscal repair. Among the agents studied, PRP, MSCs, and HA have shown particular promise in modulating inflammation and supporting tissue regeneration. While biological therapies alone may not replace surgery for complex tears, they offer promising, less invasive alternatives that support tissue preservation. However, variability in study design, agent quality, and treatment protocols remains challenging. Further long-term research will be essential to confirm clinical benefits and optimize hydrogel-based delivery methods.