Tunable uptake/release mechanism of protein microgel particles in biomimicking environment.

Microgels are intra-molecular crosslinked macromolecules that can be used as vehicles to deliver and release drugs at the point-of-need in the patient's body. Here, gelatin microgels were formed from microfluidics droplets, stabilised by aldehydes and frozen into a spheroidal shape. Microgel morphology and response to external stimuli were characterised. It was found that the behaviour of the spheroidal microgels was sensitive to both pH and ionic strength and that the distribution of charges into the microgels affected the behaviour of swelling and uptake. The uptake of molecules such as Rhodamine B and Methylene Blue were investigated as a model for drug uptake/release mechanisms. Under physiological conditions, the uptake of Rhodamine was rapid and a uniform distribution of the fluorescent molecules was recorded inside the microgels. However, the mechanism of release became slower at lower pH, which mimics the stomach environment. Under physiological conditions, Methylene Blue release occurred faster than for Rhodamine. Anionic and neutral molecules were also tested. In conclusion, the dependence of uptake and release of model drugs on basic/acid conditions shows that microgels could be used for targeted drug delivery. Different shaped microgels, such as spheres, spheroids, and rods, could be useful in tissue engineering or during vascularisation.