Real-time in situ rheology of alginate hydrogel photocrosslinking

Abstract

The reaction dynamics of biodegradable, photocrosslinkable sodium alginate hydrogels are studied by in situ, dynamic rheology. Alginate, chemically-modified with methacrylate groups, crosslinks by ultraviolet (UV) light exposure in the presence of a photoinitiator. The gel formation is monitored during UV irradiation from a light emitting diode (LED) bottom plate fixture on the rheometer. Material properties of the hydrogels, including gel points and relaxation exponent, are evaluated using the Winter-Chambon criteria. We also report a new, complementary empirical method for determining the gel point from the reduction in sample strain at the onset of gelation, via monitoring the strain curve. In addition, the crosslinking dynamics and hydrogel moduli are altered by changing the UV irradiation intensities (3-15 mW cm À2 ) and degree of methacrylation (5-25%). Dynamic rheological measurements of hydrogels as described in this paper are a potentially powerful tool to elucidate the dynamics of gelation and predict mechanical properties. This technique may aid in the design of polymer formulations with light-reactive chemical species, which have tunable properties that can be matched to a range of applications, including regenerative medicine.

Mimicking the Extracellular Matrix: Tuning the Mechanical Properties of Chondroitin Sulfate Hydrogels by Copolymerization with Oligo(ethylene glycol) Diacrylates

“…Due to closer proximity, presence of a higher number of functional groups on CS structure (groups bearing double carbon-carbon bonds) can enhance the propagation of kinetic chains and increase the moduli and crosslink density of the gels. Similar effects in increasing the moduli by increasing the ratio of the functional groups has been previously reported in hyaluronic acid, gelatin, and alginate gels [20][21][22]. Unlike the effect of functionalization, the dependence of Q and x on the crosslinker length may be less intuitive.…”

Microencapsulation as a novel delivery method for the potential antidiabetic drug, Probucol

“…However, it was noted that the PB-SA formulation behaved in a non-Newtonian, thixotropic manner, as made evident by parallel reductions in the apparent viscosity with increasing stirring speeds, which was expected 33,34. Further evidence of the thixotropic-pseudoplastic behavior of the PB-SA formulation can be seen in the proportional increases in torque and shear rate after rising shear stress forces and an associated decrease in the viscosity characteristic of non-Newtonian fluids and thixotropic behavior of the polymer solutions 35,36. The flow behavior of the microcapsules is important when estimating their PK and pharmacodynamic parameters in terms of transit time and pH-targeted delivery after an oral dose 27,32.…”

A facile CO2 switchable nanocomposite with reversible transition from sol to self-healable hydrogel

“…When subjected to CO 2 bubbling, the low-viscous sol changed to a gel structure, which was slightly viscoelastic and could hold its own weight in the inverted vial (Fig. [21][22][23] As can be seen, the G 0 value showed an obvious increment with increase the concentration of the triblock copolymer from 2 mg mL À1 to 16 mg mL À1 (Fig. The drastic enhancement of viscosity can also be observed from the steady shear measurements (Fig.…”