Hydrogels are promising materials for biomedical applications due to their tunable properties. Despite significant research on optimizing the mechanical and rheological properties of chitosan hydrogels, a comprehensive analysis incorporating pH and molarity of the neutralizing solution is still lacking. This study addresses this gap by evaluating how these factors influence the rheological characteristics of chitosan hydrogels. The hydrogels were prepared using an acidic blend and were neutralized with sodium hydroxide solutions. Rheological characterization demonstrated that all samples exhibited pseudoplastic behavior, with viscosity decreasing under shear stress. Hydrogels with higher pH values exhibited lower viscosity, which is attributed to the reduced protonation and weaker electrostatic repulsion between chitosan chains. In contrast, more acidic conditions resulted in increased viscosity and greater chain entanglements. NaOH concentration impacted gel stability; lower concentrations resulted in more stable gels, whereas higher concentrations increased crosslinking but compromised integrity at elevated pH. These findings provide essential insights for optimizing chitosan hydrogels with customized properties, making them highly suitable for specific biomedical applications, such as advanced 3D-printed wound dressings.

Hydrogels are promising materials for biomedical applications due to their tunable properties. Despite significant research on optimizing the mechanical and rheological properties of chitosan hydrogels, a comprehensive analysis incorporating pH and molarity of the neutralizing solution is still lacking. This study addresses this gap by evaluating how these factors influence rheological characteristics of chitosan hydrogels. The hydrogels were prepared using an acidic blend and were neutralized with sodium hydroxide solutions. Rheological characterization demonstrated that all samples exhibited pseudoplastic behavior, with viscosity decreasing under shear stress. Higher pH values’ hydrogels showed reduced viscosity, linked to decreased protonation and electrostatic repulsion between chitosan chains, while more acidic conditions led to higher viscosity and entanglements. NaOH concentration impacted gel stability; lower concentrations resulted in more stable gels, whereas higher concentrations increased crosslinking but compromised integrity at elevated pH. These findings are critical for designing chitosan hydrogels with tailored properties for targeted biomedical uses.

The aim of this study was to develop a material capable of rapidly absorbing bodily fluids and forming a resilient, adhesive, viscoelastic hydrogel in situ to prevent post-surgical adhesions. This material was formulated using O-carboxymethyl chitosan (O-CMCS), oxidized hyaluronic acid (OHA), and a crosslinking pigment derived from genipin and glutamic acid (G/GluP). Both crosslinked (O-CMCS/OHA-G/GluP) and non-crosslinked hydrogels (O-CMCS/OHA) were evaluated using a HAAKE™ MARS™ rheometer for their potential as post-surgical barriers. A rheological analysis, including dynamic oscillatory measurements, revealed that the crosslinked hydrogels exhibited significantly higher elastic moduli (G′), indicating superior gel formation and mechanical stability compared to non-crosslinked hydrogels. The G/GluP crosslinker enhanced gel stability by increasing the separation between G′ and G″ and achieving a lower loss tangent (tan δ < 1.0), indicating robustness under dynamic physiological conditions. The rapid hydration and gelation properties of the hydrogels underscore their effectiveness as physical barriers. Furthermore, the O-CMCS/OHA-G/GluP hydrogel demonstrated rapid self-healing and efficient application via spraying or spreading, with tissue adherence and viscoelasticity to facilitate movement between tissues and organs, effectively preventing adhesions. Additionally, the hydrogel proved to be both cost effective and scalable, highlighting its potential for clinical applications aimed at preventing post-surgical adhesions.

In this study, a full multilevel factorial design (2¹ × 3¹ × 2¹) × 2 was conducted to investigate the effects of molar mass of chitosan (CS), the type of acid used for dissolution, and the composition of the coagulation bath on the coagulation, mechanical properties, and swelling of the filaments. The results showed the statistical significance of the factors in the characteristics of these filaments. The coagulation followed Fick’s second law of diffusion, with an increase in the chitosan molar mass reducing the coagulation rate, as did the use of acetic acid instead of lactic acid. CS with higher molar mass produced filaments with larger diameters, but without a proportional increase in tensile strength. Swelling was influenced by the acid and composition of the coagulation bath. The interaction of CS with acid and the CS molar mass factor were the terms of greatest statistical significance. Crystallinity was higher for samples dissolved in aqueous solutions of acetic acid and coagulated with ethanol, while lactic acid induced greater structural disorder. Samples coagulated with ethanol presented more homogeneous surfaces, while methanol resulted in rougher filaments. These findings emphasize the critical role of processing conditions in tailoring the properties of CS filaments, providing valuable insights for their optimization for biomedical applications.

Self-healing materials operate based on trigger mechanisms, release of healing agents, healing reactions and self-assembly. They are used in infrastructure, aerospace, electronics and biomedical applications. The efficiency of the healing process is crucial, as it must be fast and effective, with the repaired area being as strong as the original material. Experimental identification involves techniques to evaluate mechanical properties, structural integrity and healing efficiency. Chitosan-based hydrogels are promising due to their biocompatibility, biodegradability and excellent mechanical properties.

Shear-Thickening or dilatant behavior is difficult to observe because it is frequently confused with mechanical oscillation or with experimental deviation. In appropriated shear rate range this behavior can be identified in samples that behave as a pseudo-plastic or Newtonian fluid in large shear rate range, evidencing what is currently called the shear-thickening – shear-thinning transition, ST–ST transition, even though this transition is less common than the shear-thinning – shear-thickening transition, in which dilatancy occurs at considerably higher shear rates. Chitosan hydrogels have gained significant attention due to their potential applications in various fields, in-cluding biomedical engineering, drug delivery, and tissue regeneration. These hydro-gels due to its peculiar structure often exhibit ST-ST behavior if the shear rate applied is low enough that this transition can be observed. In this work, chitosan hydrogels obtained from chitosan with different molar masses, degrees of acetylation, degree of crosslinking, preparation methods and aging conditions prior to rheological tests at shear rates between 0.03 s-1 and 1.5 s-1, at temperatures of 22°C, 23°C and 37°C were analyzed and the ST-ST transition related to these parameters. It was found that the ST-ST transition is more influenced by pH, molarity and chitosan concentration than by thermal aging.