Biodegradable dextran based microgels: a study on network associated water diffusion and enzymatic degradation

Sustained drug delivery represents a major challenge in nanomedicine. Solutions to the many requirements posed by this field are not easy to address using a unique delivery vehicle. In recent years, our goal has been to implement such requirements in a single device by manipulating the structural and functional features of soft biocompatible drug delivery platforms. In this paper we describe a set of biocompatible drug delivery materials, with controlled structure and dimension, which are both biodegradable in a time frame of interest and designed as drug vectors for therapeutic approaches. These microdevices were obtained using ultrasound assisted water-in-water emulsification. The resulting material was a spherical shaped microgel with controlled pore size and water content. The dynamic behaviour of water in these matrixes showed a remarkable supercooling effect, an effect which was more pronounced for those microgels with smaller mesh sizes. The biodegradability of the microgel was monitored by observing the enzymatic breakdown of the material both as a whole, i.e. by observing a large number of microgel particles, and by focussing on single particles. A complex degradation pattern was observed, with the particles first increasing their size followed by a complete structural demolition. The time required to fully degrade a microgel can be tuned by varying the relative enzyme content and/or the degree of crosslinking of the network.