Supramolecular Hydrogels Development

Supramolecular hydrogels assemble themselves into ordered structures by molecular self-assembly without artificial external intervention. The self-assembly between molecules is transient and reversible under the interaction of non-covalent bonds. Supramolecular hydrogels are usually thermally reversible and sensitive to external stimuli. Supramolecular hydrogels are physically cross-linked gels and have many advantages that traditional chemically cross-linked gels do not have, such as good biocompatibility, biodegradability, coagulation-melt gel interchange properties and good drug loading properties, and also have stable, long-lasting and controlled release properties for drugs. CD Formulation provides professional supramolecular hydrogel development services, including formulation development, structural characterization, and response analysis of hydrogels.

Fig. 1 SEM morphology of hydrogels. (Yang et al., 2023)

What are Supramolecular Hydrogels?

A supramolecular gel is a three-dimensional reticular hydrogel formed by hydrogen bonding, hydrophobic interactions, π-π interactions and other non-covalent bonds. The highly specific non-covalent interactions of supramolecular gels give them good biocompatibility, biodegradability, coagulation-solubility interactions and good stable controlled drug release properties. These excellent properties make it widely used in various fields of biopharmaceuticals. Its non-covalent cross-linking enables supramolecular gels to encapsulate various drugs without reacting with them and affecting their action. Its biodegradability allows the drug to be dissolved through gel dissolution for slow and controlled release.

Supramolecular Hydrogel Development

Supramolecular hydrogel systems are composed of non-covalent molecular interactions, consisting of two or more molecular monomers stacked on top of each other. This non-covalent cross-linking is a very attractive feature that allows the hydrogel to have a wider range of drug encapsulation. CD Formulation provides professional supramolecular gel development services to its customers, which also includes a series of assay analysis of the gel.

• Structural characterization

CD Formulation investigated the morphology of supramolecular hydrogels by field emission scanning electron microscopy, and studied the morphology of hydrogels under natural air-drying and freeze-drying conditions. Finally, they were observed by FESEM instrument at 3.0 kV after gold spray pretreatment.

The crystal structures of the dry gels were characterized by X-ray diffraction (XRD).

• pH and temperature responsiveness analysis

The temperature responsiveness of the supramolecular hydrogels was tested in a water bath from room temperature to 80°C. The pH responsiveness of the hydrogels can also be tested at different pH values (pH = 2-7).

• Gelation temperature testing

The temperature of supramolecular hydrogels was tested in glass vials using the tube inversion method. The sample was heated until the hydrogel became clear and transparent, and then gradually cooled to room temperature, at which point the sample solution stopped flowing when tilted and was recorded as the gelation temperature. After the sample gelation was completed, it was reheated and the temperature of the vial was shaken from time to time as the temperature slowly increased and the temperature at which the gel began to flow was recorded as the gel melting temperature. Each sample was heated and cooled five times, and the average value was taken as the gel temperature and melting temperature, respectively.

• Rheological analysis

Rheological experiments were performed using a rheometer in order to verify the formation of supramolecular hydrogels and to understand their mechanical properties.

• Self-healing studies

The self-healing properties of supramolecular hydrogels were studied in the macroscopic and microscopic states, respectively. The hydrogel was divided into two halves from the middle, and then the two halves were placed together and photographed to record the self-healing process. The wound healing process was also observed under a microscope.

Reference

1. Yang, Y., et al. (2023) Injectable chitosan-based self-healing supramolecular hydrogels with temperature and pH dual-responsivenesses. International Journal of Biological Macromolecules, 227, 1038-1047.