Adaptable poly(ethylene glycol) microspheres capable of mixed-mode degradation.

A simple, degradable poly(ethylene glycol) (PEG) microsphere system formed from a water-in-water emulsion process is presented. Microsphere network degradation and erosion were controlled by adjusting the number of hydrolytically labile sites, by varying the PEG molecular weight, and by adjusting the emulsion conditions. Microsphere size was also controllable by adjusting the polymer formulation. Furthermore, it is demonstrated that alternative degradation and erosion mechanisms, such as proteolytic degradation, can be incorporated into PEG microspheres, resulting in mixed-mode degradation. Owing to the adaptability of this approach, it may serve as an attractive option for emerging tissue engineering, drug delivery and gene delivery applications.