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.

The objective of this study was to develop a chitosan-based biomaterial with calcium hydroxide and 2% chlorhexidine for intracanal treatment application and, consequently, to diminish the number of microorganisms in the root canal system. The chitosan solution was prepared by dissolving it in 2% and 4% acetic acid (v/v) for 1 h at room temperature (25 °C) with magnetic agitation (430 rpm). Calcium hydroxide was obtained in two stages: the first was the synthesis of the calcium oxide—CaO, and the second was that of the calcium hydroxide—Ca(OH)₂. The samples were developed using different concentrations of chitosan, calcium hydroxide, and chlorhexidine 2%. They were codified as Ca(OH)₂ + Q2% (M1), Ca(OH)₂ + Q4% (M2), Ca(OH)₂ + Q2% + CLX (M3), Ca(OH)₂ + Q4% + CLX (M4), Ca(OH)₂ + Q2% + PEG (M5), and Ca(OH)₂ + Q4% + PEG (M6). They were characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and rheological measurement, and the antimicrobial activity was evaluated in vitro. Characteristic absorption bands of the source materials used in this research were observed in the FTIR spectra. The X-ray diffraction technique indicated that the material has a semi-crystalline structure and that the presence of calcium hydroxide made the biomaterial more crystalline. The viscosity measurement showed a pseudoplastic behavior of the studied samples. The microbiologic analysis was positive for all samples tested, with bigger inhibition zones for the samples M3 and M4. As a result, we conclude that the formulation developed based on chitosan is promising and has potential to be an intracanal medication.

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.

A lack of control over blood loss can have catastrophic implications, including death. Although several hemostatic medications have been employed to reduce bleeding, a vast majority of them are ineffective, expensive, or pose health risks to the patient. To overcome these constraints, chitosan-polyethylene glycol (CS-PEG) hemostatic gels loaded with ethanolic extract of Jatropha mollissima sap (EES) were prepared and their hemostatic, physicochemical, and cytotoxic properties were evaluated. The gels were produced by mixing CS with PEG (an external plasticizer) and EES. The phytochemical analysis revealed a significant concentration of total polyphenols and tannins content in the extract and catechin was identified as one of the key compounds of EES. Infrared spectroscopy analysis revealed the presence of EES in the gels, as well as the chemical interaction between CS and PEG. The gels were thermally stable between 25 and 37 °C (ambient and human body temperature range), had pseudoplastic deformation behavior (rheological properties preserved after shearing), were simple to inject (compression force 30 N), and were biocompatible. In vivo experiments showed that both CS-PEG-EES gels exhibited greater hemostatic action in preventing tail hemorrhage in Wistar rats, with decreased bleeding time and blood weight compared with unloaded CS-PEG gels (control groups) and Hemostank, a commercial product. However, the gel prepared with acetic acid was more efficient in controlling bleeding. These findings reveal that CS-PEG-EES gels can reduce hemorrhages and are a potent, simple, and safe hemostatic agent.

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.

Chitosan/collagen hydrogels have gained prominence in biomedical applications due to their biocompatibility and ability to promote tissue regeneration. However, rheological instability may limit their applicability. This study investigated the structural and rheological properties of chitosan/collagen hydrogels (99:1, 97:3, and 95:5%) crosslinked with 0.1% genipin. The samples were characterized by Fourier Transform Infrared Spectroscopy (FTIR), injectability, viscosity, swelling, biodegradation, and blood clotting time. Genipin crosslinking improved structural stability, increased viscosity and extrusion resistance, and provided slower and more predictable mass loss under physiological and enzymatic conditions. The swelling assay showed a progressive reduction in water uptake with increasing collagen content, further accentuated by genipin, suggesting a denser and more stable polymeric network. Additionally, the hydrogels accelerated blood coagulation, reinforcing their potential use as hemostatic agents.