No abstract

No abstract

Microencapsulation within hydrogel microspheres holds much promise for drug and cell delivery applications. Synthetic hydrogels have many advantages over more commonly used natural materials such as alginate, however their use has been limited due to a lack of appropriate methods for manufacturing these microspheres under conditions compatible with sensitive proteins or cells. This study investigated the effect of flow rate and voltage on size and uniformity of the hydrogel microspheres produced via submerged electrospray combined with UV photopolymerization. In addition, the mechanical properties and cell survival within microspheres was studied. A poly(vinyl alcohol) (PVA) macromer solution was sprayed in sunflower oil under flow rates between 1-100 µL/min and voltages 0-10 kV. The modes of spraying observed were similar to those previously reported for electrospraying in air. Spheres produced were smaller for lower flow rates and higher voltages and mean size could be tailored from 50 to 1,500 µm. The microspheres exhibited a smooth, spherical morphology, did not aggregate and the compressive modulus of the spheres (350 kPa) was equivalent to bulk PVA (312 kPa). Finally, L929 fibroblasts were encapsulated within PVA microspheres and showed viability >90% after 24 h. This process shows great promise for the production of synthetic hydrogel microspheres, and specifically supports encapsulation of cells.

The aim of this research was to understand the influence of functional group density on degradation and cell survival within injectable poly(vinyl alcohol) (PVA) hydrogels crosslinked through hydrazone bonds. For this purpose, PVA was modified with aldehyde and hydrazide functional groups. The click reaction between these two macromers, performed under physiologic conditions, led to hydrogel formation in less than 3 min. The influence of the crosslinking density on the gelation time, volumetric swelling ratio and mass loss of the hydrogels was investigated. These systems were slowly degradable as they maintained their gel-like state for more than 120 days. However, these networks also exhibited unusual degradation behaviour that could be the result of a breaking-forming bond phenomenon, attributable to the reversible nature of the hydrazone bond. This study also demonstrated that these networks maintained their mechanical strength while degrading, and cell encapsulation revealed the cytocompatibility of these systems.

Results showed that Acryl-EZE enteric coating systems provide excellent performance in both media (0.1N HCl and acetate buffer pH 4.5) for monolithic and multiparticulate dosage forms.